Fantastic Power Plant Audit
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- Pages: 168
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Output 1.1
Power Plant Performance Reporting and Improvement under the Provision of the Indian Energy Conservation Act
Output 1.1 Best practice performance monitoring, analysis of performance procedures, software and analytical tools, measuring instrumentation, guidelines or best practice manuals and newest trends
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Table of Contents 1.
General.................................................................................................. 14
1.1
Survey 'best practise' with basic Definition of Efficiency Indicators ................... 15
1.2
Analysis including Tools for Efficiency Indicators.............................................. 15
1.3
Instrumentation on Efficiency Indicators ........................................................... 16
1.4
Guidelines for basic Definition of Efficiency Indicators...................................... 16
1.5
Energy Audit ..................................................................................................... 16
1.6
Performance/ Benchmarking Analysis ............................................................... 16
1.7
Strategic Outlook (newest Trends & Research) .................................................. 17
2.
Power Scenario in Europe....................................................................... 18
2.1
Development of European & Global Electricity Demand..................................... 18
2.2
Availability, coverage and import dependency of Energy Sources ..................... 19
2.3
Primary Energy Saving through efficient use of Electricity ................................. 20
2.4
Power Plant portfolio in EU................................................................................ 21
2.5
Power Plant projects in Europe .......................................................................... 21
2.6
Pros & Cons of relevant Energy Generation Options .......................................... 23
2.7
Requirement of efficient coal and gas Power Plants .......................................... 25
3.
Directives Applicable to Large Combustion Plants.................................. 27
3.1
Legal basis in the EU ......................................................................................... 27
3.2
Underlying information ..................................................................................... 27
3.3
Document organisation..................................................................................... 28
3.4
The European Energy Industry........................................................................... 28
3.5
Applied technologies ........................................................................................ 28
3.6
Ecological issues ............................................................................................... 29
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3.7
Conditions ........................................................................................................ 29
3.8
Unloading, storage and transport of fuels and additives ................................... 30
3.9
Pre-treatment of fuel ........................................................................................ 32
3.10
Fine dust emissions .......................................................................................... 33
3.11
Heavy metals..................................................................................................... 34
3.12
SO2 emissions................................................................................................... 35
3.13
NOx emissions................................................................................................... 36
4.
Best Available Techniques to increase Efficiency and reduce Emissions.. 39
5.
State of the Art -Reference Power Plant (Source VGB)............................. 40
5.1
Brief Overview ................................................................................................... 40
5.2
Details of the Study ........................................................................................... 41
5.3
Innovations ....................................................................................................... 41
5.4
Layout Planning................................................................................................. 42
5.5
Thermodynamic Design .................................................................................... 42
5.6
Steam Turbine Plant (Turbine, Generator) ......................................................... 44
5.7
High-Pressure Turbine section.......................................................................... 44
5.8
Intermediate-Pressure Turbine section ............................................................. 45
5.9
Low-Pressure Turbine section........................................................................... 46
5.10
Generator Plant ................................................................................................. 47
5.11
Boilers ............................................................................................................... 48
5.12
Water and Steam Cycle ...................................................................................... 50
5.13
Cooling Water Systems...................................................................................... 51
5.14
Technological Options ...................................................................................... 52
5.15
Summary ........................................................................................................... 55
6.
Role of 700°C Technology for the Carbon-free Power Supply ................. 61
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6.1
Introduction and Background ............................................................................ 61
6.2
Status 700°C Technology .................................................................................. 62
6.3
Current and Coming Activities of the 700°C Technology ................................... 66
6.4
Perspectives of the 700°C Technology............................................................... 69
6.5
Regulatory and Political Framework .................................................................. 70
7.
Road Map to High Efficiency Power Plant................................................ 72
8.
Technology Platform for Zero Emission Power Plants by 2020................ 73
9.
Definition of Efficiency Parameters - Basics ........................................... 74
9.1
Efficiency........................................................................................................... 74
9.2
Losses of Efficiency in Combustion Plants......................................................... 75
9.3
Generic Technical Measures to improve Large Combustion Plant's Efficiency.... 76
9.3.1
Combustion ...................................................................................................... 76
9.3.2
Unburned Carbon in Ash................................................................................... 77
9.3.3
Air Excess ......................................................................................................... 77
9.3.4
Steam ................................................................................................................ 77
9.3.5
Flue-Gas Temperature ...................................................................................... 78
9.3.6
Vacuum in the Condenser ................................................................................. 78
9.3.7
Variable Pressure and fixed Pressure Operation ................................................ 78
9.3.8
Condensate and Feed-Water Preheating ........................................................... 79
10.
Energy Balance ...................................................................................... 80
10.1
Efficiency of German Power Plants..................................................................... 81
10.2
Efficiency Degradation ...................................................................................... 82
10.3
Energy Balance of a Coal-Fired Power Plant Unit ............................................... 82
10.4
Operating efficiency in European Power Plants.................................................. 84
10.5
Operating Efficiency of typical Indian Power Plants compared to German Power
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Plants ................................................................................................................ 87 10.6
Comparison of published efficiencies ............................................................... 88
11.
Key parameters and basis for measurements ......................................... 91
11.1
Key operating parameters ................................................................................. 91
11.2
Fuel Parameter .................................................................................................. 92
11.3
Air & Flue Gas Parameters ................................................................................. 93
11.4
Data required .................................................................................................... 93
12.
Official Statistics for Efficiency Indicator and Plant Reliability ................. 95
12.1
Reports on Analysis and Tools for Efficiency Indicators .................................... 95
12.2
Excerpts from Eurostat-Document.................................................................... 96
13.
Performance Indicators & Monitoring ..................................................... 97
13.1
Introduction ...................................................................................................... 97
14.
Software and Analytical Tools for Efficiency and Plant Reliability –Online and Offline ................................................................................................. 102
14.1
Introduction .................................................................................................... 102
14.2
Software Analytical Tools / Modules ............................................................... 103
14.3
Data Collection for the Performance Monitoring ............................................. 103
14.4
Analysis for Performance Monitoring .............................................................. 104
14.5
K I S S Y........................................................................................................... 105
14.6
Systems for Optimized Operation ................................................................... 107
14.7
Lifetime Monitoring System............................................................................. 114
14.8
Data Management System ............................................................................... 116
14.9
Thermodynamic Cycle Calculation Program – Offline Tool .............................. 117
15.
Benchmarking of Power Plant Operation & Management ...................... 121
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15.1
General ........................................................................................................... 121
15.2
Basics of Benchmarking .................................................................................. 121
15.3
Benchmarking of Thermal Power Plants .......................................................... 122
15.4
Benchmarking Methodology............................................................................ 123
15.5
Project Organization ....................................................................................... 129
16.
Energy Audit – Situation in the EU respectively Germany ...................... 131
16.1
Status.............................................................................................................. 131
17.
Overview on Regulations, Guidelines Efficiency/Plant Performance ...... 148
18.
Example: Computerized Plant and Energy Management Systems at the Evonik Steag Voerde Power Plant ......................................................... 153
19.
Latest (state of the art) technologies and status................................... 155
19.1
Technology Perspectives – Availability vs. State of the Art .............................. 155
19.2
Atmospheric Fluidized Bed Firing System........................................................ 155
19.3
Pressurized Fluidized Bed Firing System ......................................................... 156
19.4
Gasification of Coal (IGCC) .............................................................................. 159
19.5
Turbulent Pulverised-Coal Burner ................................................................... 160
19.6
Supercritical Technology ................................................................................. 163
19.7
Six Sigma Concept .......................................................................................... 164
20.
Operating Efficiency of EU Power Plants and Efforts initiated for Improvement ....................................................................................... 165
20.1
Rationale ......................................................................................................... 165
21.
Best Practices Applicable to Indian Scenario......................................... 166
21.1
Online monitoring System............................................................................... 166
21.2
Statistical Process Control Process Detection .................................................. 166
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21.3
Simulator Training on Power Plant Operation .................................................. 166
21.4
Maintenance Management Systems ................................................................. 167
21.5
Benchmarking Practices .................................................................................. 167
22.
Miscellaneous ...................................................................................... 168
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Abbreviations an
Analysis moisture
BAT
Best Available Technique
BDEW
Verband der Deutschen Energie-, Gas-, und Wasserwirtschaft
CCS
Carbon capture and storage
CFBF
Circulating fluidised bed firing system
dai
Dry adsorbent injection (flue gas desulphurisation)
DIN
Deutsche Industrienorm (German DIN Standard)
ESS
Electrostatic separator
EU
European Union
FBF
Fluidised bed firing
FF
Fibrous filter
FGD
Flue gas desulphurisation
GCV
Gross caloric value
hd
Half-dry (flue gas desulphurisation)
HHV
Higher heat value
HP
High pressure
kWh
Kilo Watt hour
LCP
Directive on Large Combustion Plants
lftraf
Air-dry and ash-free
LHV
Lower heat value
LP
Low pressure
MP
Medium pressure
NCV
Net caloric value
PFBF
Pressure fluidised bed firing system
Pm
Primary measures reducing the NOx
raw
Raw
SCR
Selective catalytic NOx reduction
SF
Dust combustion
SFBF
Stationary fluidised bed firing system
SNCR
Selective non-catalytic NOx reduction
TWh
Tera watt-hours
VDI
Vereinigung der deutschen Industrie (Association of German Engineers,
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www.vdi.de) VGB
European Association for Generation of Heat and Power, www.vgb.org)
waf
Water and ash-free
wf
Water-free
wmf
Water and mineral-compound free
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Terms and Definitions Dimension
e
Proportional auxiliary consumption
-
f Ho
Specific fuel consumption
kg/kWh
Upper heating value
kJ/kg
Lower heating value
kJ/kg
Time availability
h
Energy avalability
-
Mass flow of the fuel
kg/s, kg/h
Mass flow of the steam
kg/s, kg/h
Time utilisation
-
Energy utilisation
-
Net generator output
kW
Generator capacity
kW
Gross generator output
kW
Nominal capacity
MWel
High-voltage side net generator output
kW
Electrical auxiliary consumption
kW
Specific net heat consumption
kJ/kWh, kJ/kWs
Average fuel heat
kg/s, kg/h, kg/month
Hu kt
kW &f m &s m
nt
nw Pe
Pgen
Pi
PN Pnet
Pown qe Qf
Q FW Q nRH Q RH
Q SG Q SS se
sn tB
Feed water heat capacity supplied to the kg/s boiler Heat quantity without reheating supplied to kg/s the boiler Reheated heat quantity supplied to the kg/s machine Useful thermal quantity input into the kg/s process Superheated steam heat quantity input into kg/s the machine Number of successful start-ups
-
Number of unsuccessful start-ups
-
Operating time
h
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tN tv
WB
WN Wv z & Q heat
η ηbe η cl η el η fu η th η tr ηtot
Dimension Reference period
h
Available time
h
Energy generated
MWh
Nominal energy
MWh
Unavailable energy
MWH
Start-up reliability
-
Useful thermal heat
kJ/kg
Efficiency
-
Boiler efficiency
-
Losses of thermodynamic cycle
-
Electrical efficiency
-
Degree of fuel use
-
Thermal efficiency of the turbine
-
Efficiency of machine transformer
-
Total efficiency
-
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List of Annexures Annexure I
LCP Directive 2001 /80/ EC
Annexure II
13. BImSchV –Ordinance of implementation of Federal immission control act (English version)
Annexure III
Best Available Techniques
Annexure IV
State of the Art Reference Power Plant incl. its appendices I to VIII
Annexure V
The Evonik Steag Road to the high efficiency power plant
Annexure VIa
Roadmap for low carbon power supply ETP ZEP SRA and SDD study
Annexure VIb
Roadmap for low carbon power supply ETP ZEP SRA and Strategic Research Agenda
Annexure VII
Definition of Efficiency parameters
Annexure VIII
The complexity of thermal power plant efficiencies reporting in India and Germany” (By Dr. Kaupp, GTZ) Best available techniques to increase efficiency and reduce emissions
Annexure IX
Basis for measurements and parameters to be monitored
Annexure X
Analysis and tools for efficiency indicator
Annexure XI
Excerpts from Eurostat Document
Annexure XII
KISSY instructions & Excerpts from performance report
Annexure XIII
IGCC technology
Annexure XIV
Supercritical and ultra super critical technology
Annexure XV
CFBC technology
Annexure XVI
Six sigma process
Annexure XVII
PFBC technology
Annexure XVIII
Advanced Technologies of Preventive Maintenance for Thermal Power Plants-write up by Hitachi
Annexure XIX
Oxyfuel technology for fossil fuel-fired power plants – Dresden University of Technology, Germany
Annexure XX
Results of oxy-fuel combustion for power plants- Dresden University of Technology, Germany
Annexure XXI
Actual efficiency of thermal power plants in Europe, efficiency improvement over a period of time
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Annexure XXII
On line Monitoring System
Annexure XXIII
Statistical Process Control – Fault Detection
Annexure XXIV
Simulator Training
Annexure XXV
Maintenance Management Systems
Annexure XXVI
Monitoring and Controlling of power plants
Annexure XXVII
Maintenance Practices
Annexure XXVIII
Design Criteria of Thermal Power Plants
Annexure XXIX
Stores Inventory and Procurement System
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1.
General
A detailed survey on best practice power plant performance monitoring and was undertaken primarily in Germany/Europe by VGB and EESG.
After the survey detailed
report is prepared which covers the following outputs: •
survey 'best practise power plant performance monitoring in Germany/ Europe' with basic definition of efficiency indicators including samples of reporting
•
basic definition of efficiency indicators
•
software and analytical tools including tools for efficiency indicators used online and offline
•
instrumentation on efficiency indicators
•
guidelines/best practice manuals including VGB
•
energy auditing practise
•
analysis of performance procedure
•
strategic outlook (newest trends & research)
With a view the cover the above activities, the report is structured in to two parts: PART I: The initial part of the report gives an overall report about the electric power market in Europe including a compilation of the power plant projects in Europe. Further a description of the state of the art for electric power technologies as well as the perspective for future developments and the legal prescription for the emission limits according to the EU regulations is given. The intention of this general introduction is to give a better understanding to the specific situation in Europe and Germany in particular. •
power scenario in Europe
•
directives in the EU applicable to large combustion plants
•
best available techniques for large combustion plants
•
best practices to increase efficiency and reduce the emissions
•
state of the art – Reference power plant
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•
new trends – Role of 700 °C technology
•
future perspectives – Carbon Capture & Storage
PART II The later part of the report describes the best practise power plant performance monitoring in Germany/Europe. •
efficiency parameters definitions
•
energy balance
•
basics for the measurements and parameters
•
overview of regulations and guidelines for efficiency and plant performance
•
performance indicators and monitoring of power plants
•
software and analytical tools for efficiency indicators and plant optimisation – Online & Offline
1.1
•
benchmarking in thermal power plants as part of performance indicator
•
energy Audit
•
other relevant papers and reports
Survey 'best practise' with basic Definition of Efficiency Indicators
This document summarizes the technical and physical basis for plant performance indicators - oriented on the indicators needed and the necessary measurement devices. The report covers the definitions of the plant technical indicators as well as the correlated physical measurement units. 1.2
Analysis including Tools for Efficiency Indicators
Based on the selected and described indicators samples for standard reports used in the EU are given. These official reports are published by national authorities as well as industrial organisations like the VGB. The key tool is the control system on the plant process consisting of a measurement device, software transferring the physical unit into a plant indicator and an analysis tool in D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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order to be able to react
1.3
Instrumentation on Efficiency Indicators
The plant measurement system is part of control & instrumentation system; the plant process control system is also part of the above-mentioned system.
1.4
Guidelines for basic Definition of Efficiency Indicators
A distinction is drawn between legal and industrial regulations in the EU. Concerning the industrial regulations the VDI-guidelines are irrelevant for the report on hand; their main focus is on the design area. The main focus of the VGB-guidelines is on the operation area which has to be considered in this report.
1.5
Energy Audit
In the EU are a wide-spread set of directives (to be transposed into national law) targeting the energy sector. There are no regulations for the efficiency of electric power generation. In the past in the EU we had discussions to implement regulations, but at the end the conclusion was that market-driven mechanism are more effective. This position was supported by the fact that the electric power generation in the EU is the most efficient worldwide.
1.6
Performance/ Benchmarking Analysis
Benchmarking
of
power
plant
involves
development
of
essential
technical
and
organizational elements for the long-term commercial sustainability of the power plant operation.
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1.7
Strategic Outlook (newest Trends & Research)
The state of the art in the EU is a consistent system covering the whole chain of measurement, algorithm and analysis tools, available by all the suppliers. Prerequisite for the successful use of these instruments is to raise the awareness of the staff in applying these tools. Research work is mainly concentrating on a closer intercommunication of the technical tools with the business tools like SAP.
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PART I 2. 2.1
Power Scenario in Europe Development of European & Global Electricity Demand
(Source:
VGB
Power
Tech
–Facts
and
Figures
–Electricity
generation
2007,
http://www.vgb.org/en/data_powergeneration.html) The global population is increasing by 78 million people per year. Consequently, the population has doubled during the last five decades. At present, approximately one quarter of the global population of 6.5 billion do not have access to electricity. As a result, electricity consumption is growing faster than any other form of energy. It is expected that present global electricity consumption of 16,595 TWh is expected to double to roughly 30,673 TWh by the year 2030. One-fifth of the electricity generated globally – roughly 3,300 TWh – is required in the European Union (EU). A 30 % rise in demand is expected by 2030. Experts estimate that fossil fuels will continue to cover most of the extra demand. Fossil fuels will still account for roughly 70 % of electricity generated worldwide in 2030. About 60 % of electricity generated in the EU will come from fossil fuels by that time. Renewable energy sources will play increased role in the global primary energy consumption structure. Likewise, nuclear power will maintain an important position in global electricity generation and will even grow in some countries. Expected growth in electricity generation in EU by the year 2030 is 30 % (ie expected requirement is 4,300x109 kWh). While worldwide growth in electricity generation by the year 2030 is 85 % (i.e, expected requirement is 31,673 x 109 kWh)
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2.2
Availability, coverage and import dependency of Energy Sources
Existing primary energy reserves and resources, after including renewable energy sources, are adequate in terms of fossil fuels and uranium around the world. Hard coal and Lignite as well as uranium are the most widespread. However, energy sources have an uneven geographical distribution, which means that some countries and regions, including the European Union, are becoming increasingly dependent on imports. The EU’s fossil fuel reserves amount to approximately by 75,000 million tonnes of coal equivalent, accounting for only 5% of the known reserves worldwide, and consist mainly of lignite and hard coal. The natural gas and oil reserves amount to approximately 5,000 million tonnes of coal equivalent. Europe’s dependency on imported coal will grow from approximately by 30 % today to more than 60% by the year 2030. An import dependency of 81 % is expected for natural gas and of as much as 88 % for oil. Overall, the share of imported energy will increase from approximately from 50% today to roughly 70% by 2030. The causes of this are the nuclear phase-out chosen by some countries, along with the decreasing of cost-effectively exploitable European energy reserves. Only lignite will still be extractable from open cast mines at competitive costs in some countries in the long term. Figure 2-1 gives the development of dependence of imports of EU from 1990 to 2030. Figure 2-1:
Dependence of Imports of EU
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1990
100 90
81
80
Perc entage
86 88 75
66
70 60
2010
2020
2030
81
62
61
50
50
48 50
45 47
67
53
37
40
30
30 20
77
81
2000
18
10 0
2.3
Solid fuels
Oil
Natural gas
Total
Primary Energy Saving through efficient use of Electricity
The link between growth in gross domestic product and primary energy consumption has become weaker in many developed nations in the last few years, due to increased application of electricity facilitating many rationalisation processes. On the one hand, this development reflects the trend towards a service based society; on the other hand, the progress in energy production and its use, for example more efficient power plants, tailored energy application through electronic control or even heat pumps, is playing an important role. The expected use of electric vehicles in the future may reinforce this trend even more. Saving primary energy will therefore require more electricity. There is a risk that forced electricity savings will impair the balance of primary energy and emission cuts unnecessarily.
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2.4
Power Plant portfolio in EU
Total installed capacity of power plants in EU is 752,060 MW, which includes 27 countries. Of which Germany accounts for 18 % of the total EU. Figure 2-2 shows a break up of power plants' installed capacity in the EU.
Power plant portfolio in EU
2.5
16595
16352
13645
13320
12623
Finland
Belgium
Greece
Portugal
Denmark
37435
16997 Romania
Others
17412 CR
9555
19013 Austria
Bulgaria
21544
Spain
UK
Italy
France
0 Germany
MW
20000
Nederlands
32077 Poland
40000
33212
60000
Sweden
80000
75953
100000
81800
86762
120000
Power Plant Portfolio in EU (2005)- Total 752060 MW 115500
140000
132265
Figure 2-2:
Power Plant projects in Europe
The replacement demand for old power plants and the increase in electricity consumption in Europe have led many utilities and other investors to make plans for new projects. In
addition, taking into account also the CO2 emission trading and a worldwide increase in energy demand, coal, natural gas and nuclear power will continue to be the most important primary energy sources for electricity generation. Currently, around 67,000 MW of new build projects based on natural gas have been announced. New build projects based on lignite, hard coal and peat have a combined plant capacity of around 37,300 MW today.
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Two new nuclear power plants with a total capacity of around 3,200 MW are being constructed in the EU in Finland (Olkiluoto) and France (Flamanville), and nuclear power plants with a total capacity of a further 4,082 MW are being planned in Bulgaria, Romania and the Slovak Republic. In addition, output is being increased at existing plants.
New power plant capacity of roughly 52,780 MW is currently being planned based on
renewable energy sources such as wind, hydropower and biomass. In total, projects with a joint capacity of roughly 167,395 MW have been announced. Whether all of the announced new build projects will actually be realised will depend greatly on future primary energy price trends and political conditions (country-specific bonus/malus regulations) due to CO2 reduction strategies. Figure 2-3 gives break up of proposed (or planned) power plants with regard to the energy source. Figure 2-3:
Planned power projects in EU Planned Power Projec ts in EU (total 167395 MW)
67005 48805
50000 40000
RES
Other
88 Wind
Hydro
187 & waste
3233
Residues
469
power
Peat
Oil
7770
Nuclear
4075
2500 Gas
10000 MW 0
Lignite &
30000 20000
Biomass
33263
coal
70000 60000
Hard
80000
It is shown that renewable energies (including wind power) have taken a major share of 32 % (i.e, 52,782 MW).
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2.6
Pros & Cons of relevant Energy Generation Options
At present 46% of the total electricity is generated in Eurpoe is CO2 free. The following Figure 2-4 gives the break up of the power generation. Figure 2-4:
Break up of power generation Nuclear 30%
Biomass, waste, oil, etc 7% Wind 2% Hydro 10%
Coal 31%
Gas 20%
The following Table 2-1 gives pros and cons of relevant electricity generation projects Table 2-1:
Pros and cons of power generation options
Energy Source Nuclear
Pros •
•
Climate-protecting
Cons •
electricity generation with
in some European
no CO2 emissions
countries
Cost-effective and reliable
•
import dependency
•
Extensive effort and cost required for safety
High safety standard at western nuclear power
Long licensing process under nuclear law
supply with no critical
•
Social acceptance problem
•
Disposal and final storage of nuclear fuel not yet
plants
resolved politically
Coal
•
Hard coal can be procured
•
Growing demand for hard
cost-effectively by many
coal (predominantly from
providers on the world
China and India) and
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Energy Source
Pros •
Cons
market
limited transport capacities
Brown coal in Europe is a
entail price risks
readily available domestic
•
raw material •
Gas
•
•
Power plant technology
for natural gas •
Flue gas require cleaning
has great potential for
with corresponding cost
efficiency improvement
and effort for plants
Most environmentally
•
Volatile natural gas prices
friendly fossil fuel
are leading to large
relatively low CO2
fluctuations in electricity
emissions
generation costs
Electricity generation in
•
plants
Dependency on imports from a possible supply risk
highly efficient power
•
CO2 emissions higher than
•
Increasing concentration of
Short erection times and
export sources in
low investment costs for
politically unstable regions
new plants
Wind
•
Climate-protecting
•
Serious obstacles imposed
electricity generation with
by new environmental
no CO2 emissions
protection targets Expansion of existing
•
High plant efficiency
•
Cost-effective operation
potential is problematic for
•
Network services are
environmental policy
available extremely quickly
reasons
•
Flood protection support
•
•
High investment costs for new plants due to extensive compensatory measures not relating to electricity generation
Hydro
Serious obstacles imposed
•
Climate-protecting
•
Electricity generation with
by new environmental
no CO2 emissions
protection targets
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Energy Source
Pros
Cons Expansion of existing
•
High plant efficiency
•
Cost-effective operation
potential is problematic for
•
Network services are
environmental policy
available extremely quickly
reasons
•
Flood protection support
•
•
High investment costs for new plants due to extensive compensatory measures not relating to electricity generation
2.7
Requirement of efficient coal and gas Power Plants
CO2 emissions can be reduced gradually through technological development. The volume of CO2 produced from hard coal electricity generation can be reduced by around 35 % worldwide if low-efficiency power plants (the average global efficiency factor currently stands at 30 %) were replaced by power plants with a 46 % efficiency factor (current state of the art power plants). Therefore, the gradual reduction of CO2 emissions by technological development is the first option. It would result in profitable on three counts: •
resource protection, as less fuel is required for generating the same amount of electricity
•
substantial reduction in CO2 emissions
•
increased electricity generation from the same fuel amount
In the long term, electricity generation from fossil fuels could take place virtually CO2-free through capture and underground storage of CO2. The potential for CO2-reduction of coal-fired power plants is shown in the following Figure 2-5 (Source VGB). Figure 2-5:
Reduction potential in CO2
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1. Efficiency 2. CO2 Emissions gram of CO2 per kWh 3. Fuel consumption g/kWh
Average Worldwide 1.
30%
2.
1.116
3.
480
EU 1.
38%
2.
881
3.
480
Steam power plant State of the art 1. 45% 2. 743 3. 320
2010
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700oC technology 1.
>50 %
2.
669
3.
288
CCS technology
2020
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3. 3.1
Directives Applicable to Large Combustion Plants Legal basis in the EU
The European LCP-Directive 2001/80/EC (see annexure I) applies to combustion plants, the rated thermal input of which is equal to or greater than 50 MW, irrespective of the type of fuel used (solid, liquid or gaseous). In addition to this it shall apply only to combustion plants designed for production of energy with the exception of those, which make direct use of the products of combustion in manufacturing processes. The LCP-Directive defines emission limit values for the discharge of substances from the combustion plant into the air. These emission limit values define the permissible quantity of a substance contained in the waste gases from the combustion plant which may be discharged into the air during a given period; it shall be calculated in terms of mass per volume of the waste gases expressed in mg/Nm3, assuming an oxygen content by volume in the waste gas of 3% in the case of liquid and gaseous fuels, of 6% in the case of solid fuels and 15% for gas turbines. Member States of the EU should bring into force the laws, regulations and administrative provisions necessary to comply with the LCP-Directive. Germany had brought into force the 13. BImSchV, it implements the regulations of the LCP-Directive (English version of 13. BimSchV see annexure II).
3.2
Underlying information
Numerous documents, reports and information from member states, the industry, plant operators and authorities, as well as equipment suppliers and institutions active in environmental protection, have been called on. Further information was gathered during site visits in various European member states and in personal discussions on issues regarding the choice of technology and experiences during the application of reduction techniques.
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3.3
Document organisation
In Europe, the Power and/or Heat Generation sector is a heterogeneous industrial sector. The energy generation is based on numerous fuels, generally to be divided according to their state of aggregation into solid, liquid or gaseous fuels. Therefore this document has been vertically organised so that the individual fuels are listed successively, where joint aspects and techniques are described together, however, in the three introductory chapters.
3.4
The European Energy Industry
Within the European Union every available type of energy source is used for the generation of power and heat. In individual EU member states the selection of the fuel used for energy generation is largely based on the national fuel resources, e.g. on the local or national availability of hard coal, brown coal, biomass, peat, crude oil and natural gas. Since 1990, the share in electric power generated from fossil fuel energy sources has increased by approximately 16 %, while the demand increased by approx. 14 %. The share of the electric power generated from renewable energy sources (including hydroelectric power and biomass) increased by almost 20 %, which is higher than average. Combustion plants are operated either as large supply plants or as industrial combustion plants providing driving power (e.g. in the form of electric power, mechanical energy), steam or heat for industrial production processes.
3.5
Applied technologies
A variety of combustion techniques are applied to the energy generation overall. For the combustion of solid fuels, dust combustion, fluidised bed firing systems and grate firing are all considered conceivable (published by the EU in the BAT data sheet: "Reference Document on Best Available Techniques for Large Combustion Plants", on the conditions described in this document. The possible status of liquid and gaseous fuels corresponds to appropriate boilers, engines and gas turbines on the conditions described in this document. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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The system to be used is selected on the basis of the economic, technical, ecological and local requirements such as availability of the fuels, operational requirements, market conditions and requirements of the mains. Electric power is mainly generated by generating steam in a boiler fired with the selected fuel. This steam is supplied to a turbine that drives a generator, generating electric power. The degree of efficiency of the steam cycle is limited by the requirement to liquefy the steam after it leaves the turbine. Some liquid and gaseous fuels can be fired directly in order to drive turbines with combustion gas or they can be used in internal combustion engines driving the generator. Every technology offers certain advantages to the plant operator, especially regarding its operational suitability with regard to variable energy requirements.
3.6
Ecological issues
Most combustion plants use fuels and other raw materials mined from the Earth’s natural resources, in order to convert them into useable energy. Fossil fuels are the most widely available energy source currently used. However, their combustion leads to an important and sometimes significant burden for the environment as a whole. The combustion process causes the development of emissions into the air, water and soil, with air pollution considered one of the most severe ecological burdens. The most significant emissions developing during the combustion of fossil fuels are SO2, NOx, CO, fine dust (PM10) and greenhouse gases such as N2O and CO2. Further substances such as heavy metals, halogenated compounds and dioxins are discharged in smaller quantities.
3.7
Conditions
The possible emission values are based on daily average values, standard conditions and an O2 content of 6 % / 3 % / 15 % (solid fuels / liquid and gaseous fuels / gas turbines), and refer to a typical burden situation. Brief peak values during peak loads, start-up and shutdown processes and operational malfunctions of the exhaust gas cleaning systems, D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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which might be higher, must be reckoned with.
3.8
Unloading, storage and transport of fuels and additives
In Table 3-1 some options are summarised for avoiding emissions during unloading, storage and transport of fuels and additives such as lime, limestone, ammonia etc. Table 3-1:
Some options to avoid emissions during unloading, storage and transport of fuels and additives
Best possible technology Fine dust
•
Using loading and unloading equipment with as small a drop to the storage heap as possible to reduce the development of diffuse emissions (solid fuels).
•
Using water spray systems in countries with no risk of frost to reduce the development
of
diffuse
emissions
during the storage of solid fuels (solid fuels). •
Arranging transfer conveyors in safe surface areas outdoors so that damage by vehicles and other equipment can be avoided (solid fuels).
•
Using enclosed conveyors with well designed, robust ventilation and filter equipment
at
conveyor
transfer
locations to avoid dust emission (solid fuels). •
Optimising the transport systems to minimise
dust
development
and
transport on location (solid fuels). •
Applying the principles of excellent
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Best possible technology design and construction practice and appropriate maintenance (all fuels). •
Storing lime or limestone in silos with well designed, robust ventilation and filter equipment (all fuels).
Water contamination
•
Storage on sealed, drained surfaces, collection of drained water and water treatment in settling tanks (solid fuels).
•
Using storage systems for liquid fuels with impermeable protective walls able to hold 75 % of the maximum capacity of all tanks or at least the maximum contents of the largest tank.
•
The content of the tank should be indicated and an appropriate alarm system
used;
in
order
to
avoid
overfilling the storage tank, automatic control systems can be used (solid fuels). •
Installing pipelines in safe surface areas outdoors
so
that
leaks
can
be
determined quickly and damage by vehicles and other equipment avoided. For
inaccessible
pipelines,
double-
walled pipes can be used with an automatic
gap
control
(liquid
and
gaseous fuels). •
Collecting the runoff water (rain water) from
fuel
stores
and
treating
this
collected flow (settling tanks or waste water
treatment
plant)
prior
discharging waste water (solid fuels).
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Best possible technology Fire protection
•
Monitoring the storage areas for solid fuels with automatic systems, in order to detect spontaneous combustion and determine danger zones (solid fuels).
Diffuse emissions
•
Using leak detection systems for burner gas and alarm systems (liquid and gaseous fuels).
Efficient use of natural resources
•
Using
expansion
turbines
for
the
recovery of the energy contents of the pressurised burner gases (natural gas supplied via pressure pipes) (liquid and gaseous fuels). •
Preheating the burner gas by using the waste heat of the boiler or gas turbine (liquid and gaseous fuels).
Health and safety risk due to ammonia
•
For the transport and storage of pure liquid ammonia: pressure vessels for pure liquid ammonia > 100 m3 should be designed with a double wall and located below ground; vessels with a capacity not exceeding 100 m3 should be
manufactured
applying
the
annealing treatment (all fuels). •
Considering the safety aspect, using aqueous ammonia is less dangerous than storing and handling pure liquid ammonia (all fuels).
3.9
Pre-treatment of fuel
For solid fuels, the pre-treatment of the fuel mainly consists in blending and mixing in order to ensure stable combustion conditions and to reduce emission peaks. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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3.10
Fine dust emissions
The fine dust discharged during the combustion of solid or liquid fuels is almost exclusively composed of the mineral components. During the combustion of liquid fuels, poor combustion conditions lead to the development of soot. The combustion of natural gas does not constitute a significant dust emission source. In this case, the dust emission values are usually far less than 5 mg/Nm3, without the application of additional technical measures. Table 3-2:
Options regarding the reduction of fine dust emissions in fossil fired combustion plants, excepting gas combustion plants (excerpt from LCP-Directive)
Thermal combustion output (MWth)
Hard coal New plants
Existing
Liquid boiler fuels New plants
plants 50 – 100
Option
Dust emission values (mg/Nm3)
5 - 20
5 - 30
achieving these values
Existing plants
5 - 20
5 – 30
ESS or FF
ESS or FF in 100 – 300
5 - 20
5 - 25
5 - 20
5 – 25
combination with FGD (wet, hd or dai) for SF,
> 300
5 - 10
5 - 20
5 - 10
5 – 20
ESS or FF for FBF
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Output 1.1 Abbreviations: Dai
dry adsorbent injection
ESS
electrostatic separator
FBF
fluidised bed firing
FF
fibrous filter
FGD
flue gas desulphurisation
SF
dust combustion
Hd
half-dry
For the dedusting of exhaust gases in new and existing combustion plants, the applicable state of technology is the use of an electrostatic separator (ESS) or a fibrous filter (FF), where emission values below 5 mg/Nm3 are usually achieved by using a fibrous filter. Cyclone separators and mechanical dedusters alone cannot be considered sufficient; however, they can be used as a prepurification stage within the exhaust gas process. The possible state of technology regarding dedusting and the corresponding emission values are compiled in the table below. For combustion plants exceeding 100 MWth, and especially
exceeding
300 MWth,
the
dust
values
are
lower
because
flue
gas
desulphurisation processes, which are already state of the art for desulphurisation in Germany and the EU, also achieve a reduction of the fine dust.
3.11
Heavy metals
The emission of heavy metals results from their occurrence as a natural component in fossil fuels. Most of the heavy metals to be considered (As, Cd, Cr, Cu, Hg, Ni, Pb, Se, V, Zn) are usually released in the form of compounds (e.g. oxides, chlorides) together with dust. Therefore it is usually possible to reduce the heavy metal emissions by installing high-efficiency dedusting plants such as electrostatic separators or fibrous filters. Only Hg and Se occur at least partially in the steam phase. At the typical operating temperatures of separation plants, mercury indicates a high steam pressure and its separation with fine dust reduction facilities fluctuates significantly. With electrostatic separators or fibrous filters operated in combination with exhaust gas desulphurisation processes such as the limestone wash process, the spray absorption process or the dry adsorbent injection, the average Hg separation level is 75 % (50 % for electrostatic separators and 50 % for exhaust gas desulphurisation plants), and with an additionally D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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available selective catalytic reduction (SCR) in high-dust arrangement (arrangement between boiler and dust separator), it is possible to achieve 90 %.
3.12
SO2 emissions
Emissions of sulphur oxides mainly result from the sulphur occurring in the fuel. In general, natural gas is considered sulphur-free. With certain technical gases this is not the case, and in these cases desulphurisation of the gaseous fuel may be necessary. For combustion plants fired with solid and liquid fuels, the use of low-sulphur fuels and/or desulphurisation is usually an option. Table below (Table 3-3) gives various options regarding the reduction of SO2 emissions in hard and brown coal combustion plants (excerpt from LCP-Directive). Table 3-3:
Options regarding the reduction of SO2 emissions in hard and brown coal combustion plants (excerpt from LCP-Directive)
Thermal
SO2 emission values (mg/Nm3)
combustion
these values
Hard and brown coal
output
Option achieving
(MWth)
New plants
Existing plants
50 – 100
200 - 400*
200 - 400*
Low-sulphur fuel
150 - 400*
150 - 400*
or/and FGD (dai) or
(FBF)
(FBF)
FGD (hd) or FGD (wet)
100 - 200
100 - 250*
100 – 300
(depending on the plant size). Cleaners using seawater. Combined process
> 300
20 - 150*
20 - 200*
reducing NOx and
100 - 200
100 - 200*
SO2. limestone
(CFBF/PFBF)
(CFBF/PFBF)
injection (FBF).
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Output 1.1 Abbreviations: CFBF
circulating fluidised bed firing system
dai
dry adsorbent injection
FBF
fluidised bed firing system
FGD
flue gas desulphurisation
hd
half-dry
PFBF
pressure fluidised bed firing system
In most cases for plants exceeding 100 MWth, however, the use of low-sulphur fuel can only be taken into account as a supplementary measure in combination with other measures
reducing
the SO2
emissions. In addition to
using low-sulphur fuels,
desulphurisation by means of a wet cleaner (reduction rate 92 – 98 %) and the spray absorption process (reduction rate 85 – 92 %) are mainly considered applicable techniques, with a market share of more than 90 % already. Dry exhaust gas desulphurisation processes such as dry adsorbent injection are mainly used for plants with a thermal output of less than 300 MWth. The advantage of the wet cleaner is that it also reduces emissions of HCl, HF, dust and heavy metals. For plants with an output of less than 100 MWth, the wet cleaning process is not considered ideal due to high costs.
3.13
NOx emissions
The most significant nitrogen oxides discharged during combustion are nitrogen monoxide (NO) and nitrogen dioxide (NO2), with common designation NOx. For hard coal dust combustion plants, it is possible to reduce the NOx emissions with primary and secondary measures such as selective catalytic reaction (SCR), where the reduction rate of the SCR system is between 80 % and 95 %. The disadvantage of the application of SCR or SNCR is possible emissions of unconverted ammonia ("ammonia leak"). For small plants without major load fluctuations fired with solid fuels and with a stable fuel quality, the SNCR process is also considered a possible application to reduce NOx emissions.
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This means the use of sophisticated low-NOx burners in combination with other primary measures such as exhaust air return, staged combustion (air grading), fuel grading, etc. The application of primary measures tends to encourage incomplete combustion, causing a higher concentration of unburned carbon within the fly ash and a certain amount of carbon monoxide emissions. For boilers with a fluidised bed firing system firing solid fuels, a reduction of the NOx emission is possible by distributing the air or returning the exhaust gas. The NOx emissions from stationary and circulating fluidised bed firing systems differ slightly. Table 3-4 shown below enables conclusions regarding the minimisation of the NOx emissions and the corresponding emission values for hard coal. Table 3-4:
Options regarding the reduction of NOx emissions in hard coal combustion plants using different combustion techniques (excerpt from LCP-Directive)
Thermal
Combustion
combustion
technique
NOx emission values (mg/Nm3)
Option achieving these values
New plants
Existing plants
grate firing
200 - 300
200 - 300
Pm and/or SNCR
SF
90 - 300
90 - 300
Combination of Pm
output (MWth) 50 – 100
and SNCR or SCR
100 – 300
SFBF & PFBF
200 - 300
200 - 300
SF
90 - 200
90 - 200
Combination of Pm Combination of Pm together with SCR or combined process
SFBF, CFBF &
100 - 200
PFBF
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100 - 200
Combination of Pm together with SNCR
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Thermal
Combustion
combustion
technique
output
NOx emission values (mg/Nm3) New plants
Existing plants
90 - 150
90 - 200
Option achieving these values
(MWth) > 300
SF
Combination of Pm together with SCR or combined process
SFBF, CFBF &
50 - 150
PFBF Abbreviations: CFBF
circulating fluidised bed firing system
PFBF
pressure fluidised bed firing system
Pm
Primary measures reducing the NOx
SCR
selective catalytic NOx reduction
SF
dust combustion
SFBF
stationary fluidised bed firing system
SNCR
selective non-catalytic NOx reduction
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Combination of Pm
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4.
Best Available Techniques to increase Efficiency and reduce Emissions
For clean and new boilers, it can be stated that the efficiency levels around 86 % - 94 % (LHV), are currently recorded for solid fuel, The main losses are associated with flue-gas waste heat via the stack, unburned carbon, waste heat in ash and radiation losses. The effect of fuel is important, assuming boilers with identical performance (same ambient and flue-gas temperature, same excess air, etc.) different boiler efficiencies are obtained depending on the nature of fuel as the following examples illustrate (LHV basis): Fuel
Efficiency [%]
International coal
94
Lignite
92
Low grade lignite
86
The best practices/best available techniques to increase efficiency and reduce the emissions are given in annexure III.
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5.
State of the Art -Reference Power Plant (Source VGB)
5.1
Brief Overview
The study on the "Reference Power Plant" has been produced with the aim of developing a 600 MW capacity hard-coal fired power plant operating at efficiency of 45.9%, concept that is sustainable in the future and will meet these challenges. The main aims of the concept study are to examine the feasibility of a modern power plant with sharply reduced emissions, taking account of the economic conditions that prevail in the deregulated energy market, and also to demonstrate the opportunities for North Rhine-Westphalia (Germany) as an industrial location. Operating on a hard coal Efficiency of over 48% could also be achieved with certain technical measures, which would require different site conditions and different economic boundary conditions. With efficiency of 45.9%, this power plant clearly above average of hard coal power plants currently in operation in Germany where average efficiency is around 38%. The study has shown that technically, economically and ecologically optimised power plant technologies based on hard coal provide good opportunities A number of innovative proposals have been included in the plant design. These innovations were selected according to the criteria of their profitability and feasibility using the materials and technologies currently available on the market. This study brings together the planning performance requirements of the plant operators, the planning work undertaken by the plant manufacturers and the results of the academic institutions. The following gives a brief description, details are given in the annexure IV.
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5.2
Details of the Study
The first phase of the study involved the collection of innovations and an evaluation. Here innovative ideas in the fields of plant planning, process technology, boilers, mechanical engineering, electrical engineering, instrumentation and control and generators were collected and each individual concept evaluated. The decision on whether to incorporate such an innovation into the reference power plant was taken jointly by plant operators and plant constructors. Parallel to this, the innovation evaluation phase was used to investigate the economic feasibility of the different options of improving efficiency. Evaluation factors such as those for improving efficiency, reducing auxiliary station power requirements and increasing availability have been defined for these studies, based on existing market boundary conditions. Plant operators and plant constructors added their experience to these evaluation factors and together they were used to optimise the plant as a whole.
5.3
Innovations
The study started with a brainstorming phase to gather and evaluate ideas. In total, over eighty innovative concepts relating to plant planning, process engineering, boilers, mechanical engineering, electrical engineering, instrumentation & control, and the generator were raised and their technical and economic feasibility evaluated. The technical concepts were discussed in engineering meetings. The decision as to which of these ideas was to be incorporated in the preferred variant was prepared following a discussion of the findings in the project management group. The following innovative concepts that have been considered in the course of this study should be emphasized in particular: •
With the aim of maximizing power conversion in the turbine and also taking the other economic evaluation factors into account, the exhaust crosssection of the low-pressure turbine section is specified as 16 m2. Because of the high centrifugal forces, the exhaust blades must be made of titanium
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alloys. •
With the aim of minimizing capital expenditure, various concepts were studied for installation of the turbine. In the course of this study, a low-level foundation design, i.e. a turbine tabletop at an elevation of around 8 m was compared to conventional design with a tabletop at an elevation of around 16 m. Use of an elevated-level design of foundation for the turbinegenerator at 60 m was also considered.
•
Standard designs (tower-type and two-pass boilers) were also examined and evaluated, as was the concept of the horizontally fired boiler, the aim being to minimize investment costs.
5.4
Layout Planning
Layout planning was conducted with the aim of designing a compact and efficient plant, using as a basis existing project experience gained from standard reference power plants and hard-coal-fired power plants that have already been built. The in-line arrangement selected for the steam turbine-generator and boiler results in short steam lines and at the same time gives a short length of bus ducting and power transmission line to the outdoor switchyard. This feature minimizes cost. The side-by-side arrangement of the cooling tower and electrostatic precipitator allows efficient design of the flue-gas discharge system via the cooling tower, while achieving optimum routing of the circulating water system at the same time.
5.5
Thermodynamic Design
As part of the optimization process a thermodynamic study was made of the different variants. Below is an overview summarizing the findings: •
Utilization of hot mill air or flue gas waste heat by transferring the heat to the HP feed water-heating line.
•
Use of an external de-superheater to increase final feed water temperature up to 320°C.
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•
Reduction of pressure drop in the extraction lines for the HP feed water heaters.
•
Reduction in terminal temperature differences for HP feed water heaters.
•
Consideration of use of an additional LP feed water heater (9th feed water heater).
•
Thermo compression in the area of the LP feed water heaters.
•
Concepts for reheat temperature control (control within boiler or by spray attemperation or by allowing reheat temperature to slide).
•
Consideration of use of an HP feed water heater bypass for mobilization of short-term peak output.
•
Study of a feed water pump drive concept (turbine drive vs. electric drives with various designs).
•
Optimization of the cold end (LP turbine exhaust cross-section and size of cooling tower).
The power plant concept, which has been optimized for technical and economic factors, produces the following technical data: •
Gross capacity: 600 MW
•
Type of boiler: Tower-type boiler with vertical tubes and steam coil air heater
•
Heat recovery: Utilization of mill air heat recuperation
•
Flue gas discharge: Discharge via cooling tower
•
Turbine model: H30-40 / M30-63 / N30-2 x 16 m²
•
Main steam parameters: 285 bar / 600°C / 620°C
•
Condenser pressure: 45 mbar
•
Generator: Water/hydrogen cooling
•
Feed water heating stages: 8 feed water heaters + external de-superheater
•
Feed water final temperature: 303.4°C
•
Feed water pump concept: 3 x 50 % electric motor-driven feed water pumps, variable-speed drive with planetary gearing
In addition to the preferred variant, the following additional requirements for enhancing flexibility have been grouped together in the "flexibility package" option: D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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•
Fast activation of primary frequency control system, as required in the DVG Grid Code "Network and System Rules of the German Transmission System Operators"), 1998 edition.
•
Option of providing additional power by partly bypassing the HP feed water heaters and
•
Use of header-type HP feed water heater instead of tube-sheet design type.
The flexibility package thus takes into account the plant operators' desire to be able to match the power plant’s mode of operation to the requirements of a volatile electricity market, over and beyond straight base load operation.
5.6
Steam Turbine Plant (Turbine, Generator)
The turbine modules used belong to the Siemens steam turbine product line named HMN with best reliability and availability values over the last decades. It is a turboset with separate HP, IP and LP turbine sections. A rigid connection (via so-called push rods) is implemented between the intermediatepressure outer casing and the low-pressure inner casing. This push rod concept for the HMN series turbine allows thermal axial expansion of the rotor system (moving blades) and that of the casing (stationary blades) to be matched. The result of this is a reduction in the axial clearances for the sealing elements between rotor and casing, and thus an improvement in the efficiency of the turbine-generator.
5.7
High-Pressure Turbine section
As high-pressure turbine the module H30-40 will be used. It’s a barrel-type design best suited for sophisticated steam conditions and assigned power output demand. The inlet parameters for the main steam entering the high-pressure turbine section are 600°C at 285 bar.
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The high-pressure turbine section has a barrel-type design. The radial joint is located in the middle of the barrel casing. An HP turbine is equipped with an inner casing due to the high steam parameters of 600°C/285 bar. The HP turbine blading consists of a diagonal stage, which is designed with a low degree of reaction and 17 stages of type 3DSTM (3D design with reduced secondary losses). The entire blading system is designed using the 3DVTM design principle (3DVTM: 3D design with variable stage reaction) so as to optimize blade efficiency. The materials used for the moving and stationary blades are exclusively high-alloy chromium steels with a chromium content of 10 % - 12 %.
5.8
Intermediate-Pressure Turbine section
As intermediate-pressure turbine the module M30-63 will be used. It’s a double flow turbine with inner casing design to cope best with highest reheat temperatures. The inlet parameters for the single-reheat steam entering the IP turbine are 620°C at 60 bar. The model M30-63 IP turbine is a double-flow, dual-shell turbine section. The materials for the shaft and inner casing are high-alloy chromium steels. The outer casing is made of nodular cast iron. This IP turbine module is designed for maximum reheat temperatures. As a outstanding reference the power plant "Isogo", Japan with a reheat temperature of 610°C can be stated. A further increase in reheat temperature to 620°C, affects the creeprupture strength of the shaft material. The use of a slightly modified alloy content for the 10 % chromium shaft material can increase the material strength. The use of 10 % chromium steel with boron shows promising results. Tests of creep-rupture strength for a shaft-like body are available from a German research project (VGB 158). The results are in alignment with the expected increase of creep rupture strength (time frame > 30,000 hours). D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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Active, external steam cooling in the steam inlet area is not required. Vortex cooling is used in the inlet flow area. The first blade stage of the IP turbine consists of a diagonal stage, which is designed with a low degree of reaction. At both the generator and turbine ends the blading of the turbine features 18 stages, these including 13 3DSTM blade profiles and four "tapered twisted" profiles. The first three moving blade stages of both flows are fabricated of Nimonic alloys (nickelbased alloys) on account of the high temperatures to which they are exposed. The other moving and stationary blades are fabricated of high-alloy chromium steels with a chromium content of 10 to 12%. In addition, a double T-head design is used for the blade roots of the first and second moving blade stages. This allows the high loading of centrifugal force on the blade roots and root fixing region. The acting centrifugal force is distributed between all blade contact surfaces and thus reduced.
5.9
Low-Pressure Turbine section
The newly developed turbine section N30-2 x 16m2 is planned as the low-pressure turbine section, a double-flow, dual-shell turbine section. The inlet parameters for the crossover steam are 269°C at 5.5 bar. The condenser pressure is 45 mbar. The inner casing features a welded design housing the stationary blade carrier. The lowpressure inner casing rests on the bearing pedestal base plates by means of support arms. The inner casing rests on a sliding plate and can allow axial movements transferred from the intermediate-pressure outer casing by the rigidly connected push rods. The points where the support arms penetrate the low-pressure outer casing are sealed by expansion joints. The LP outer casing and LP inner casing are thus completely decoupled. The N30-2 x 16 m2 features three drum stages and three standard stages per flow. The exhaust cross section of the final stage is 16 m2 per flow. Steel cannot be used to fabricate D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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this size of blades due to the high centrifugal force loading produced by peak blade speeds of Mach 2. A titanium alloy therefore has to be used. The titanium final stage blades feature a three-dimensional profile with integral shrouding, with a snubber in the middle of the profile. Gap losses at the blade tip are reduced by the integral shrouding. At rated speed the integral shroud and the snubber in the middle of the blade constitute in effect a rigid structure together with the adjacent blades, thereby forming a low-vibration blade assembly.
5.10
Generator Plant
The generator plant consists of a two-pole hydrogen-cooled turbo generator, which is rigidly coupled to the turbine. It has a direct water-cooled stator winding, a static exciter, a two-channel digital automatic voltage regulator and the necessary supply systems i.e. seal oil, hydrogen and primary water units. The stator winding is cooled directly by water, and the rotor is cooled directly by hydrogen. Losses occurring in the other components such as core losses, frictional losses and additional losses are dissipated directly by hydrogen. A large number of radial cooling slots ensure uniform dissipation of heat in the laminated core. The hydrogen is circulated in the closed cooling circuit inside the gas-tight and pressureproof generator frame by a radial blower fitted at the exciter end. The hydrogen coolers are installed in the generator frame. The water (primary water) treated for cooling the stator winding is circulated in the closed circuit by a pump and transfers the heat absorbed in the primary water cooler to the secondary water. The excitation energy is supplied to the rotor winding by a static exciter via slip rings. The excitation unit consists of an exciter transformer and a thyristor assembly in a three-phase bridge circuit.
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5.11
Boilers
Comparison of various boiler designs In order to find the most favorable boiler design for the reference power plant, three different boiler designs were examined. A tower boiler, a two-pass boiler and the innovative horizontally fired boiler were designed and compared with each other in respect of their costs and operational reliability. The aim of establishing specific advantages for each of the types of boiler resulted in different concepts of solution in respect of furnace and the pressure section. MPS mills and low-emission DS burners were used in all variants. The variant comparison is based on a data record for a power plant unit with a gross installed capacity of 550 MW. The fact that in the course of optimising the plant the decision was made that the gross installed capacity of the "preferred variant" would be 600 MW does not affect the conclusions arrived at when comparing the concepts. In order to achieve boiler efficiency of 95%, areas such as the cold end of the flue gas and the furnace were optimised.
Innovations in boiler The greatest improvement in efficiency is achieved by raising the steam parameters to the high steam conditions at the boiler outlet (600°C/620°C/292.5 bar). A further improvement in plant efficiency has been achieved by optimizing the economizer section and raising the feed water temperature. These temperature and pressure increases make it necessary to use new material for the walls (7 CrMoVTiB 10 10) and new super heater materials (hightemperature austenitic materials such as TP347HFG). The efficiency of the boiler is improved to 95% by keeping to the very low excess air coefficients of 1.15 and exhaust gas temperatures of 115°C. The distance to the dew point temperature for flue gas ducts and the electrostatic precipitator is achieved by the specified guaranteed coal with a sulphur content of only 0.6%. As a result of the low air ratio and the flue gas temperature window specified by the DENOX plant upstream of the air heater, the air alone is no longer adequate as the only heat sink because a partial flow of cold air must be routed past the air heater on account of the pulveriser mill air D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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temperature control system. A mill air heat exchanger, one of the innovations, removes the excess heat from the mills’ hot air so that application to the air heater is almost 100%. As a result of transferring this excess heat to the feed water economiser (parallel to the HP preheater section) an exhaust gas temperature of 115°C downstream of the air heater can be achieved. The vertical evaporator tubing in a Benson boiler is a further innovation. The spiral-wound plain tubing is state of the art here, as is a correspondingly high mass flow density to provide adequate cooling of the furnace encompassing walls that are exposed to a high thermal load. The advantages of vertical evaporator tubes pertain more to the design. There is a small advantage as regards auxiliary station power technique since slightly less power is required from the feed pump. From the point of view of production engineering, vertical tubing is easier to manufacture and to assemble. The tie-bars used for the spiralwound tubing are dispensed with. A flatter angle can be used on the hopper, thus allowing the height of the furnace to be reduced and also generating a cost benefit. The Benson range can be extended to a part load of 20%. This results in advantages when later on the RPP will be operated at intermediate load. The vertical evaporator tubing operates with mass flow densities approximately equivalent to a naturally recirculation boiler. For this reason, optimised inner ribs are required in order to provide adequate cooling. A swirl is created in the flow because of the inner ribs, extending the time the inner walls remain wet. The area of the boiling crisis is thus shifted into zones exposed to less heat flux, thus ensuring that the sudden jump in the temperatures of materials is considerably reduced. Heat flux profiles are largely balanced out as a result of the effect of natural circulation that applies with lower mass flow densities. Where it is known that excess heating occurs, this can be corrected by geometrical adjustments - for instance, larger tubes can be used around the burner. Efficiency can be enhanced further by operating the plant with a variable reheater outlet temperature. In the design point at 100% load, there is no injection during steady-state operation. Although the reheater outlet temperature drops with any movement away from the 100% load point, this proved to be the most economically efficient method for, initially, base-load operation and for when subsequently the plant will be operated at intermediate load. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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The partition pitch of 480 mm must also be seen as an innovation. There is no record to date of this kind of spacing becoming blocked. Apart from being able to reduce the height of the boiler by about 1 m, it is also easier to clean by overhead soot blowers. The materials selected for the boiler are:
5.12
•
Evaporator/superheater - vertical tubing
7CrMoVTiB 10 10
•
Superheater 1 support tube partition
HCM 12
•
Superheater 2
Super 304 H or TP 347 HFG
•
Superheater 3
HR3C or AC 66
•
HP outlet header
P92
•
Reheater 1 Outlet
7CrMoVTiB 10 10, HCM 12
•
Reheater 2
HR3C or AC66
•
Reheater outlet header
P92
Water and Steam Cycle
The water/steam cycle essentially consists of the supercritical steam generator, the steam turbine-generator with the condenser, the main condensate pumps, the low-pressure (LP) feed water heaters, the feed water tank, the feed water pumps, the high-pressure (HP) feed water heaters and the connecting pipes. The superheated steam produced in the steam generator is supplied to the turbine which drives the generator. After the steam has driven the HP turbine section and thus released part of its energy, it is passed to the reheater where it is heated up again and then routed to the IP turbine section. The steam flows directly from the IP turbine section to the LP turbine section, where it is expanded to condenser pressure. Finally the steam is condensed in the condenser. The heat of condensation is dissipated via the circulating water system. The condensate produced is collected in the condenser hotwell. The main condensate pumps pump the condensate from there through the LP feed water heaters into the feed D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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water tank. The feed water pumps are then used to pump the water from the feed water tank through the HP feed water heaters and back to the steam generator. The LP feed water heating line, the feed water tank and the HP feed water heaters are heated with steam extracted from the turbine. •
The condenser is a two-casing surface condenser with water boxes positioned at both sides. The steam dome, steam shell and the hotwell are welded structures, as are the water boxes. The following materials are used: Tubes of stainless steel (14401), tube sheets made of stainless steel (14571). The water boxes are made of Carbon steel.
•
Primary frequency control by means of condensate throttling: As the hotwell serves as a condensate storage vessel, there is no need here for an additional cold condensate storage tank.
•
2 x 100 % main condensate pumps: Only one pump operates during normal operation. Following condensate throttling, the second pump is cut in to pump to the feed water tank the condensate that has accumulated in the condenser hotwell in this process. This serves to return the system to its initial status.
•
Bypass cleaning of condensate using a separate 1 x 100% capacity condensate cleaning pump: A 2 x 50% capacity bypass cleaning system for condensate is implemented to satisfy the stringent water quality requirements of the Benson boiler for feed water that is low in salt and low in corrosion products. As a result of this configuration, condensate cleaning can be designed for comparatively low pressure levels and the unit can be operated completely independently of the condensate polishing system.
5.13
Cooling Water Systems
The cooling water systems essentially consist of the natural-draft wet cooling tower, the circulating water system with a make-up water supply system, the auxiliary cooling water system and the closed cooling water system.
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The circulating water pumps supply the condenser with circulating water from the cooling tower basin. Once the heat of condensation rejected to the condenser has been transferred to the circulating water, this water is routed to the natural-draft wet cooling tower. The heat is ultimately dissipated to the atmosphere via the cooling tower. To ensure the requisite cooling water quality, part of the cooling water is blown down. The system is topped up with make-up water to compensate for losses caused by evaporation and blowdown. The auxiliary cooling water is taken from the circulating water system upstream of the condenser. After it has absorbed the heat from the closed cooling water system, it is returned to the circulating water system downstream of the condenser. The closed cooling water system dissipates the heat from the individual cooling loads via the closed cooling water heat exchanger to the auxiliary cooling water system.
5.14
Technological Options
If the market boundary conditions result in higher economic evaluation factors, this signifies that technical solutions requiring higher specific investments to increase efficiency are then cost-effective. In a marginal case the specific additional investment may exactly match the "economic evaluation factor". If the additional investment is higher, the economics of the entire project are reduced. If additional investment is lower, the projects economics would increase accordingly. Assuming that the economic evaluation factors are higher than in the preferred option, as a result of changing boundary conditions (e.g. CO2 emission costs), the enhancement options summarized might then be of interest. In this context, the preferred option with all its boundary conditions would be the basis for option A. Option A, in turn, would be the basis for option B, etc. Details are shown in Table 5-1 and Figure 5-1 below. Turbine driven boiler feed-water pumps were not investigated, due to the fact that the increase of efficiency in comparison to feed-water pumps with frequency-converter is marginal and the capital cost are much higher than the advantage. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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Table 5-1: Description
Preferred option vs. additional options for boosting efficiency Preferred variant
Variant A
Variant B
Variant C
Variant D Plus using of fluegas heat
Plus frequency Specification
Basic
Converter BFP
Plus 320oC feed
Plus cond pressure
+optimized
Temperature
LP-Turbine 4×10m2
+9 stage preheating
Water end-
40 mbar with
Preheaters
transfer
system with low
temperature- heat transfer
+cond . pressure 35mbar
Live steam
3285bar/600oC/62
3285bar/600oC/62
3285bar/600oC/62
3285bar/600oC/62
3285bar/600oC/62
parameter
0o C
0oC
0o C
0oC
0o C
303.4oC
303.4oC
320oC
320.4oC
320.4oC
3HP/FWT/4LP
3HP/FWT/5LP
3HP/FWT/5LP
3HP/FWT/5LP
3HP/FWT/5LP
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes,HP Preheating
Yes, HP Preheating
Yes, HP Preheating
Yes, HP Preheating
Yes, HP Preheating
Yes
Yes
Yes
Yes
Yes
45mbar
45mbar
45mbar
40mbar
35mbar
N30-2×16m2
N30-2×16m2
N30-2×16m2
N30-4×10m2
N30-4×10m2
No
yes
Yes
yes
yes
No
yes
Yes
yes
yes
No
no
yes
yes
yes
No
no
no
yes
no
No
no
no
no
yes
No
no
no
no
no
Feed water endtemperature Number of preheaters External desuperheat er Steam air heater Use of mill air heat
recuperation Sliding reheat temperature Condenser pressure Low pressure turbine 9..stage
preheating Frequency – converter for boiler
feed – water pump (BFB) drive Feed water end – temperature 320oC
Condenser
pressure 40 mbar Condenser
pressure 35 mbar Condenser pressure 25
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Description
Preferred variant
Variant A
Variant B
Variant C
Variant D
No
no
no
no
yes
No
no
no
no
no
mbar Flue gas heat transfer system with low
temperature – heat
transfer Frequency converter for
condensate - pump
Figure 5-1:
Efficiency chart 47.3
47.5 47 46.5 45.9
46
46.1
46.2
Variant A
Variant B
46.5
45.5 45
Preferred variant***
798 Eur/kW
App. 20 EUR/kW gross per% Point**
App. 25 EUR/kW gross per% Point
Variant C
Variant D
App. 30 EUR/kW
Above 35
gross
EUR/kW gross
per% Point
per% Point
Effic ien c y ( %) Vs Ev aluatio n F ac to r *
Power output for all 600 MW at generator terminals * Increase in efficiency in Eur/kWwgross per % point ** The increase of efficiency in varient A considers also reduced aux. power which require additional investment of amount 8 EUR/kW gross *** In the concept study the Preferred Variant was investigated in detail; the Variants A-D have been derived.
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"Increase in efficiency" as an economic evaluation factor of the variant under review (e.g. Variant A: 20 €/kWgross per % point) then represents the additional investment that can be justified in economic terms relative to both the gross installed capacity of the power plant and an efficiency increase of 1 % point net. The respective predecessor variant is the basis for each case. For Variant A that would be the preferred variant, for Variant B it would be Variant A and so on. The increase in efficiency of Variant A compared to the preferred variant also includes the efficiency effect that results from a reduction in the auxiliary power requirement (by changing the feed water pump drive). This reduction in the auxiliary power requirement increases the specific investment for Variant A by an additional 8 €/kW (gross) and corresponds to a parallel rise in the "auxiliary power requirement economic evaluation factor". Independently of the measures presented above, a further increase in efficiency to over 47.3 % is possible by further reducing condenser pressure or by increasing the main steam parameters. If the overall concept is changed, by in example considering dual reheat, additional enhancement options are then available. However, all measures require considerable additional investments.
5.15
Summary
The principle challenges of the power supply industry today are security of supply, lowcost generation of electricity, environmental protection and conservation of available resources. This study on the "Reference Power Plant" has been produced with the aim of developing a hard-coal fired power plant concept that is sustainable in the future and will meet these challenges. The main aims of the concept study are to examine the feasibility of a modern power plant with sharply reduced emissions, taking account of the economic conditions that prevail in the deregulated energy market. The first phase of the study involved the collection of innovations and an evaluation. Here innovative ideas in the fields of plant planning, process technology, boilers, mechanical engineering, electrical engineering, instrumentation and control and generators were collected and each individual concept evaluated. The decision on whether to incorporate such an innovation into the reference power plant was taken jointly by plant operators and D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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plant constructors. Parallel to this, the innovation evaluation phase was used to investigate the economic feasibility of the different options of improving efficiency. Evaluation factors such as those for improving efficiency, reducing auxiliary station power requirements and increasing availability have been defined for these studies, based on existing market boundary conditions. Plant operators and plant constructors added their experience to these evaluation factors and together they were used to optimise the plant as a whole. In this study the power plant concept which is optimized for technical and economic aspects is called the "Preferred variant" and is characterized by the following data: •
Gross installed capacity
600 MW
•
Net Installed capacity
555 MW
•
Net efficiency
45.9 %
•
Main steam parameters
285 bar / 600°C / 620°C
•
Feed water end temperature
303.4°C
•
Condenser pressure
45 mbar, wet closed-circuit cooling via draft cooling tower
•
Price of the plant
478 mill €
•
Specific plant price
797 € / kW gross
•
Boiler type
Benson tower boiler with vertical tubes
•
Utilization of waste heat
Use of mill air heat
•
Flue gas cleaning
SCR-DENOX, electrostatic precipitator, flue gas desulphurization unit using limestone
•
Flue gas discharge
Discharge via cooling tower
•
Steam turbine
three-casing steam turbine with simple intermediate heating and low pressure stages made of titanium alloy
•
Generator
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•
Economiser stages
Eight economizers + external desuperheater
•
Feed water pump concept
3 x 50% electric motor-driven feed water Pumps, variable -speed drive with planetary gearing
The efficiency of the optimum power plant concept "Preferred variant" for the prevailing market conditions is 45.9 %. At less than 800 € gross of installed capacity, the price of the plant is in a range where the RPP is an extremely competitive method of generating energy as compared to the alternatives. The process parameters are crucial for the high efficiency. These include parameters such as high steam pressure and high steam temperatures (285 bar/600°C/620°C), which in certain areas require the use of materials that have only recently been shown to be operationally reliable. As it is practically impossible nowadays to use river water for cooling, closed-circuit cooling via a cooling tower is planned for the reference power plant. The cooling tower is also used to discharge the flue gases produced during combustion. Sulphur and nitrogen are removed from these gases before handling in a separate part of the plant. The standard of flue gas cleaning complies with the strict reference values recently adopted for the European Union. If river water could be used for cooling, it would increase the net efficiency of the plant by a further percentage point to approximately 47 %. Certain technical measures could also be applied to achieve efficiency of over 48 % but these would require different economic boundary conditions than could be assumed at the present time. The effects of double reheating have not been included in this study because the additional investment required would be considerably higher than could be justified by the resulting increased efficiency of about half a percentage point. The efficiency of 45.9 % achieved by the RPP far exceeds the average efficiency currently achieved by hard-coal-fired power plants in Germany. Taking the average efficiency of 38 % (Germany) as a reference point, the increased efficiency of around 8 percentage points reduces the amount of fuel used and consequently also CO2 emissions by around 20 %. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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If the power generated in coal-fired power plants in 2020 were only to be generated in plants with efficiency of at least 46%, the CO2 emissions from coal-fired power plants of 9.1 billion t (average efficiency of 34%, worldwide) forecast for 2020 could be reduced by a further 2.3 billion t to 6.8 billion t (average efficiency 46%). The forecast increase of worldwide CO2 emissions attributable to coal-fired power generation in the period between 2000 and 2020 would thus be reduced from 63 % to 21 %. The studies of economic feasibility for this concept show that the RPP is more efficient than all options for hard-coal-fired power plants that are currently being examined in detail, providing that CO2 emissions entitlements do not have a considerable cost impact. The only solutions that are comparable in economic terms in the fossil-fuelled large power plant sector are modern lignite fired power plants (MLP) and combined cycle power plants using natural gas. In terms of economic feasibility, when these two alternative power plants are compared only the modern lignite fired power plant is slightly more costeffective than the RPP , primarily on account of its extremely low fuel costs, which can also safely be considered to remain at a constant level in real terms over the entire operating period. However, this type of plant can only be operated by companies that have appropriate access to lignite. Nevertheless, this type of plant is extremely relevant to those utilities in terms of covering base-load requirement reliably and cost-effectively in the long term. The time when a plant of the same type as the reference power plant can be used to supply to the grid purely on the basis of commercial decisions depends crucially on the trends that can be expected in the intervening period in respect of the revenues that can be generated on the wholesale market. Currently these are not adequate to justify an investment on business grounds. Overall, the figure for power generation costs based on assumptions made on an individual basis for the new base-load plants that need to be built and which after 17 years will be changed over to intermediate load operation indicate a figure of around 3.3 and 3.5 €ct/kWh. With the planned mode of operation, the RPP is more cost effective than the gas-fired combined-cycle plant, in spite of the considerably higher efficiency of this latter type of D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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plant and its substantially lower investment costs. The main reason for this is that a hard coal price of 41 €/t (heating value for coal to the design specification = 25 GJ/t, purchase price per tce = 48 €) can be assumed. In view of the very considerable reserves available across the world, the low market access barriers and the market structure characterized by intense competition, hard coal prices will at most increase marginally after being adjusted for inflation over the entire period of operation. This result is comparatively robust because the price of natural gas must not increase by more than 0.5 %/year in real terms in order to make up for the cost advantage of hard coal under these conditions. This is unlikely in view of the increase in demand world-wide for gas as a source of energy and its undeniable environmental advantages, which have been documented in the corresponding asking price. Only if - against all expectations - the price of hard coal were to increase in real terms by more than 1 %/year (and the price of gas did not increase at more than this rate over the same period) would the combined cycle plant produce better economic results than the hard-coal-fired reference power plant. However, these economic advantages only apply if possible cost impacts resulting from measures to reduce CO2 are not taken into account. If the impact of CO2 is only 5 € in real terms per ton of CO2 emitted overall, the hard-coal-fired reference power plant would be considerably less viable economically than the gas-fired combined cycle power plant. The same applies even if the gas price rises by up to 1.2 %/year in real terms and the price increase for hard coal is limited to 0% /year. Thus, apart from the usual market risks, plant operators have to deal with the additional unforeseeable business situations that arise from the political aim of CO2 entitlement trading and the actual national arrangements for this as it affects fossil-fuelled power plants. Coal-fired power plants using the latest designs, which are extremely efficient in terms climate protection and conserving resources, can only be built if the suitable political framework conditions are developed for them. The objectives cannot be met under any circumstances if additional costs for CO2 entitlements were to be loaded onto an efficient hard-coal-fired power plant for reasons of climate protection.
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This would only make investment in this technology more difficult and at the same time promote one-sided building of additional gas-fired power plants, with the result that security of supply would be impaired in the long term and dependency on this fuel would lead to increased (price) dependency. In view of the fact that it is expected that hard coal will be extremely significant as an alternative fuel for power generation - on a global scale as well - in the longer term, the successful implementation of the reference power plant in Germany would have considerable export potential, which would contribute to maintaining the expertise of power plant vendors.
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6.
Role of 700°C Technology for the Carbon-free Power Supply 1)
2)
3)
Dr. Franz Bauer , Dr. Dariush Hourfar , Helmut Tschaffon 1) 2)
E.ON Engineering GmbH, Gelsenkirchen 3)
6.1
VGB PowerTech e.V., Essen E.ON Energie AG, München
Introduction and Background
In face of the climate change and the necessary carbon abatement strategy the requirements for the future power supply are carbon-free technologies. Any scenario analysis provided by the IEA Energy Outlook or the publications of the European Commission on this field show the absolute need for carbon-based primary resources for the coming decades. The consequences are the development of carbon-free technologies. The outcome of the Technology Platform ZEP "Zero Emission fossil-fuelled Power Plants" is three major paths for carbon-free technologies: •
post-combustion – capture of CO2 out of the flue gas
•
pre-combustion – integrated gasification of coal in combination with a CO shift
•
oxy-fuel – combustion of fossil fuel under oxygen atmosphere
Clear position of any institution analysing in depth the constraints and opportunities for a carbon free power supply like the TP ZEP or the Eurelectric study ´Role of Electricity´ is that all technological options are needed. Having in mind that climate protection is a global issue the relevance of global competition is evident. As well as the availability of competitive technologies will be decisive for the capability to cope with the challenges and finally to succeed in providing a clean and secure and affordable power supply in the future. The intention of this paper is to point out the strategic role of the 700°C technology, starting with the intention in considering the thermodynamic of the Carnot process and the D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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materials needed to achieve high process parameters leading to high efficient power plants. It is clearly to emphasize: The 700°C technology is the pre-requisite for the successful implementation of two of the described technology paths - post-combustion and oxy-fuel - based on a high-efficient basic process. Consequently we will deal with the status, the current and coming activities and the perspectives of the 700°C technology. Concerning the overall strategic and political context a position referring the necessity for the coherent regulatory framework and a consistent deployment strategy will be given.
6.2
Status 700°C Technology
The beginning of activities concentrating on the development of materials able to bear 700°C steam parameters lies in the early 90´s, leading to the AD700 project, phase I and II, which were finished end of 2006. AD 700 was co-funded by the European Commission within FP5 launched in 1998 by the Commissioner and supported by about 40 stakeholders from equipment suppliers, power generators and the scientific community. The key objective of AD 700 was the development of innovative turbine and boiler designs, identifying and developing material for the components in the high temperature regions and assessment of the economic viability. A broad range of materials - Ni-based alloys have - been investigated, analysed and tested in small samples. Parallel comprehensive studies have been performed in order to work out a basic power plant concept. The goal was to achieve efficiency figures of more than 50 % net and to give first indications about the economic feasibility of this concept. The necessity of carbon-free technology was not yet on the agenda. The main issue was identification and selection of appropriate materials and testing. The targets set out for the boiler materials with respect to mechanical strength were:
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•
Martensitic materials 100 N/mm2 at 650 °C/100,000 hours
•
Austenitic materials 100 N/mm2 at 700 °C/100,000 hours
•
Nickel-based alloys 100 N/mm2 at 750 °C/100,000 hours
These targets were met for the austenitic materials and the superalloys but not for the martensitic materials. It was not possible to find a better steel type than P92. Sandvik developed the austenitic superheater tube material with the trade name Sanicro 25, and Special Metals developed a superalloy for superheater tubes with the trade name Inconel 740. The nickel-based alloys identified for the boiler and steam lines are materials such as Inconel 617 and Nimonic 263. For the turbine components Inconel 617, 625 and Waspalloy, respectively are foreseen for rotors, castings and blade and bolts. A large number of long term creep tests have been carried out both on bar, tube and forged material, and they are still in progress. Table 6-1:
Composition of AD 700 materials (alloys)
Element
Ni
Cr
Co
Mo
Other
A 625
63.5
21.5
0
9
Al, Ti, Nb
A 617
52
22
12
9.5
Al, Ti
A C263
51
20
20
6
Al, Ti
A 740
50
24
20
0.5
Al, Ti, Nm
Sanicro 25 (A 174)
25
22
1.5
0
W, Cu, Fe
Material
The result of both phases of AD 700 was a preference set of materials covering all requirements for boiler materials consisting of membrane wall, headers, pipe-work and valves and for turbine materials with shaft, blades, pipe-work and valves. As important as the material development was the outcome of the plant concept studies demonstrating the principal possibility of both – high efficiency and promising cost figures.
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In the following the key issues are presented. The thermodynamic of the Carnot process with relevance for the plant concept is shown in Figure 6-1. Figure 6-1:
Carnot efficiency and efficiencies of some seawater-cooled plants
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Consequently the thermodynamic scheme for 700°C concept is described in Figure 6-2. Figure 6-2:
AD 700 thermodynamic cycle
As the nickel-based alloys are extremely expensive, the concept of compact design was studied. The aim is to minimize the amount of these materials – e.g. by making the steam lines as short as possible. These studies identified considerable room for savings, which also will be valuable for more conventional plants. For the turbine, a turbine inlet valve, forged rotor, welded rotor, moving blades, stationary blades, bolting and welding of pressure containment parts were considered. Also innovative designs with the aim of reduced need for the nickel-based alloys have been studied. Considerable effort has been made to establish business plans for a full-scale demonstration plant. The studies included a detailed risk assessment and again a check on the feasibility taking the latest material strength values and prices into consideration. The technology is still feasible even when a moderate price for CO2 quotas is used.
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Parallel national projects have been initiated, particularly MARCKO I and II covering both material design and tests in small samples.
Emax Initiative Based on these encouraging results of AD 700 an industry funded strategy study was started with the goal to make a comprehensive evaluation in general and to define the steps necessary to bring this technology to real application under market conditions. The work was done under the umbrella of the Emax Initiative - an industry group driven by the generators coordinated by VGB. The clear result was the confirmation that this concept offers the potential to cover both high efficiency and the fundamental basis for a carbon-free power supply on fossil fuels and before entering into the erection of a demo plant two steps are stringently needed: •
a component test under realistic operation conditions with the experience of design and fabrication of the near full scale components and
•
out of this learning process a pre-engineering study for the specifications for a demo plant covering material concept, design and fabrication, balance of plant consisting of process figures necessary for 50% efficiency, component design and operation requirements.
At the end one will get reliable figures in terms of actions to be done, the realistic time schedule and the financial means needed for realisation – ready for a sound assessment of the contribution for a carbon abatement strategy, of the market opportunities, of the funding requirements - public and industry - and the time and cost risks aligned with.
6.3
Current and Coming Activities of the 700°C Technology
COMTES700 First step of the study was the design, construction, erection and operation of the component test facility (CTF) COMTES 700; i.e. a facility implemented into an operating boiler consisting the key components of a boiler like evaporator membrane wall, superheater, pipe-work, headers and valves, additionally with a turbine control valve and D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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referring ducts. Due to the fact that under FP a continuation in terms of funding was not possible the resources of the Research Fund for Coal and Steel were taken, an occasion to thank for the co-operative support of the DG RTD. The project has been co-ordinated by VGB integrating partners from the equipment suppliers and the generators, i.e. 9 European generators are working together in terms of financing and exchanging experience and pursuing this technology with the goal of implementation in due time. The work started in spring 2004, the component test facility went into operation in July 2005 and until now more than 10.000 operating hours could be achieved. The CTF represented a considerable challenge. The principle diagram may look relatively simple, but the integration in the power plant with all necessary steam-, drain-, vent lines, instrumentation and control equipment represent a really big task, which in this case was made even bigger because the time from the official start to actual operation was only one year and delivery times for the tube and pipe material were long. E.ON has been responsible for the integration and operation of COMTES700 in Scholven F (see Figure 6-3). Figure 6-3:
Principle diagram COMTES700
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Generally one can state that the learning process was very interesting, but very useful and has given clear indications what has to be analysed and investigated within the preengineering study as the next step. Parallel to COMTES700 a test rig in the Esbjerg power plant was installed with a certain precursor function, meaning testing in advance design and material as a kind of accelerating process and to take preventive measures.
PP 700 – pre-engineering study The project has been conceived as a cross-border transnational project. To date, 10 European energy utilities (E.ON Energie AG, Electricité de France, France, Electrabel European Generation, Belgium, EnBW Kraftwerke AG, Germany, EVN AG, Austria, DONG Energy Generation, Denmark, RWE Power AG, Germany, STEAG AG, Germany, Vattenfall Europe Mining & Generation AG & Co. KG, Germany, Vattenfall A/S Nordic Generation, Denmark) have joined together with the aim of developing this sustainable European concept for generating power on the basis of fossil fuels. In the context of the envisaged pre-engineering study the European energy utilities involved will determine viable technical and economic decision-making principles for power plants with a live steam condition of 700°C. The European Generators are working together supported by a European regional fund (local government of the State of North Rhine-Westphalia) in pursuing the issue of preengineering. The equipment suppliers are integrated by orders placed by VGB the coordinator. Goal is to perform an innovative pre-engineering study in order to be ready for a more detailed evaluation of the opportunities of the technology at the end. The necessity and political will of a convincing carbon abatement strategy is on the agenda now. In the mean time the TP ZEP was launched strongly developed and pushed by the stakeholders from the electric power industry lead by VGB. The work of the pre-engineering study has started and is terminated for autumn of 2008 an exciting time is lying ahead.
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6.4
Perspectives of the 700°C Technology
As stated before the necessity for a CO2 free power supply technology is on the political agenda; having in mind the results of the scenario analysis from IEA and EC DG TREN postulating a major share of power supply will be on fossil resources - there is no other way if security of supply and competitiveness are taken into account. The technological development of fossil-fired power plants, with a marked increase in efficiency levels to around 50 %, is at the forefront. In the phase of power plant renewal in the medium term, i.e. in the years from around 2015 to 2020, it could thus be ensured if the project is concluded successfully that the European CO2 reduction targets can be achieved by means of efficient, economically viable power plant solutions. A reduction in specific CO2 emissions per MWh generated of around 25 % compared with power plants currently in operation (mean efficiency 38 %) is associated with 700°C technology. The proportional reduction in the fuel mass flow used can also partly offset rising fuel prices. The competitiveness of the European energy industry and also of the capital goods industry that is to be supplied with electricity and process heat can thus be stabilized. In the long term, i.e. in the new construction period after 2020, the realization and safe operation of a power plant using 700°C technology represents together with other technologies like Oxyfuel and IGCC an essential prerequisite for flushing CO2 economically out of the flue gases and transferring it to suitable deposits. E.ON has announced to build and to operate a demonstration plant based on the 700°C technology. This is an important step towards carbon free technologies. The power output was fixed in the before mentioned pre-engineering study with 550 MW gross. The process will be a single reheat cycle. E.ON plans to erect the demo plant in the northern part of Germany. The operation is scheduled for 2014. To realise this ambitious plan a lot of additional R&D work has to be done. Only to mention one example: It´s necessary to produce reheat pipes out of Alloy 617 with an outer diameter of about 500 mm and a wall thickness of 30 mm. A COORETEC associated project with participation of VGB, several German electric utilities and manufacturers was launched in this year to produce a longitudinal welded pipe. In the beginning of 2008 the pipe will be produced. Afterwards the pipe will be examined and a creep test follows. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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6.5
Regulatory and Political Framework
The 700°C technology is of even higher relevance than before. Two paths out of three major routes are requesting a high-efficient basic plant concept respectively highly efficient components in order to master the technical challenge of resource saving, carbon capturing and affordable generation technologies. This can be provided by the 700°C technology. The key characteristics of the post-combustion process as well the oxy-fuel process are components demanding process heat in form of steam or water or flue gas. In spite of the fact that for determining exact figures intensive research work has to be done. But the first results are showing very clearly that only by a high temperature thermodynamic cycle combined with an optimal integration of the additional steps of carbon capture out of the flue gas - post-combustion - or air separation for delivering oxygen for the combustion oxy-fuel - the goal of a resource saving carbon-free power supply at affordable costs can be achieved. Efficiency of any process step is the key for success. Another important opportunity of the 700°C technology is the one for synergies; synergies in a sense that the key characteristics of components of different power plant concepts are based on the same principles of laws of nature. The design, the construction, the test and the operation of components - even for a specific concept - delivers worthwhile results for other concept using the physical or chemical processes. By respecting and supporting this effect a more efficient and successful development of new power plant concept will be ensured - the key argument for pursuing different promising power plant concept in parallel. This helps essentially to reduce the unavoidable risks of technical development. The strategic context is determined by the following facts: •
Evidence of climate change
•
Access to primary resources
•
Worldwide competition and
•
Necessity to develop Carbon-free technologies for fossil based plants.
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The consequences for the European Union, but the other global players also are to find the right political measures respectively regulatory framework in order to enable to develop the appropriate technologies in due time with the available resources - human and financial one. The supply with energy or power is at the end a question with a huge social background even potential for explosive stresses. The past and the evident future challenge has shown that it is necessary to reflect on the •
goal and approach for public funded research programme
•
balance between basic and industrial research and application
•
relation between public and industry funded research and development and
•
role of political and regulatory framework.
It is time now to intensify a broad and open discussion between all involved parties now with the aim to draw coherent conclusions and to initiate a stringent action plan. The initiative of the European Commission to establish a Strategic Energy Technology Plan, SET plan, has been appreciated. At the end huge investments have to done, but investments are only possible if a level playing field is in place covering the above-mentioned topics.
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7.
Road Map to High Efficiency Power Plant
Efficiency refers in this context not only to the choice of the power plant process and its parameters, but also to operation and maintenance and the efficiencies attained in daily operation. The planning, construction and project handling for such power plants also must be efficient if the projects are to be successful. Finally, the term "efficiency" as applied to net efficiency must be regarded in relation to the power plant efficiencies possible and attainable in each country. The high-efficiency power plant by itself or as an element of Carbon capture and storage (CCS) schemes represents an important contribution to the conservation of fuel resources, but also to climate protection. The European Road to build high efficiency power plants is given in the annexure V, exemplarily Evonik Steag.
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8.
Technology Platform for Zero Emission Power Plants by 2020
Following developments in clean power generation and the priority given to "zero emission power generation" in the Sixth Framework Programme (FP6) industrial stakeholders and the research community had several meetings which resulted in the creation of a technology platform for zero emission fossil fuel power plants. The strategic deployment document and the strategic research agenda as well as more details are given in annexures VI(a) and VI(b). The Experts agree that CO2 capture and storage technology (CCS), together with improved energy conversion efficiency, is a near-term solution to reducing CO2 emissions from fossil fuel power generation on a massive scale. Its immediate deployment is therefore vital if we are to avoid the catastrophic consequences of climate change we are facing today. Yet despite most of the technology elements being available, CCS is still not deployed for two key reasons: 1. The costs and risks still outweigh the commercial benefits 2. The regulatory framework for CO2 storage is not sufficiently defined. The Strategic Research Agenda therefore describes a collaborative programme of technology development for reducing the costs and risks of deployment; while the Strategic Deployment Document outlines how we can accelerate the market to achieve zero emission power production by 2020.
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PART II 9. 9.1
Definition of Efficiency Parameters - Basics Efficiency
There are different ways of describing the efficiency of a combustion installation. There are also a number of national guidelines describing acceptance tests and the measurements of certain efficiencies. The efficiencies defined in this report as well as in the annexures to this report are to be understood as efficiencies at a certain electrical output and normal operating mode, i.e. as the power station is operated in daily generation mode. They are calculated from averaged measured values attained from the values recorded over a certain period of time. This section gives the brief details of various types of efficiencies dealing with the power plants and other related parameters such as: •
Carnot efficiency: The ideal efficiency of a thermal process or ‘Carnot’ efficiency is a measure of the quality of the conversion of heat into work
•
thermal efficiency: thermal efficiency considers only the actual cycle process used in the power station. The efficiency is then the ratio of the useful mechanical output to the heat flow transferred to the cycle process media (as a rule, air or water)
•
the degree of fuel efficiency: The degree of fuel efficiency is defined for cogeneration plants, which generate and emit electrical and thermal energy (heat). For these plants, the useful output consists of the sum of the generated electrical energy and the generated thermal energy
•
proportional auxiliary station service
•
high voltage net capacity
•
heat consumption of generating unit
•
overall efficiency of power plant
•
fuel consumption
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•
specific fuel consumption
•
unit efficiency: Unit efficiency is then the ratio of the net electrical output to the energy supplied with the fuel. The electrical output according to this definition is the output on the high voltage side of the main transformer.
•
unit efficiency for steam withdrawal: If, in a power station unit, steam is extracted for heating or process purposes, then this steam is no longer available for power generation. In order to be able to compare the unit efficiency in this case with the efficiency of pure power generation, the electrical output which could be obtained from the extracted heating steam if it were to expand to the condenser pressure, has to be added to the electrical output.
•
exergy concept and exergy efficiency
•
influence of climate conditions on efficiency
•
relationship between efficiency and environmental issues
Details on this are given in annexure VII.
9.2
Losses of Efficiency in Combustion Plants
The heat energy resulting from the combustion of fossil fuels is transferred to the working medium (steam). During this process, part of the energy is lost in the flue-gas. The total losses from the generation of steam depend on the fuel (ash and water content, calorific value); the capacity and operation of the steam generator; the air-fuel mix; the final temperature of the flue gas; and the mode of operation. The operation of the steam generator requires continuous surveillance. The heat losses from the steam generator can be categorised as: •
losses via the off-gas. These depend on the flue-gas temperature, air mix, fuel composition and the level of fouling of the boiler
•
losses through unburned fuel, the chemical energy of which is not converted. Incomplete combustion causes CO and hydrocarbons to occur in the flue-gas
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•
losses through unburned material in the residues, such as carbon in bottom and fly ash
•
losses via the bottom and fly ash from a DBB and the slag and fly ash from a WBB
•
losses through conduction and radiation. These mainly depend on the quality of insulation of the steam generator.
In addition to the heat losses, the energy consumption needed for the operation of auxiliary machinery (fuel transport equipment, coal mills, pumps and fans, ash removal systems, cleaning of the heating surfaces, etc.) also has to be taken into consideration. Poor combustion lowers the economic viability, increases the environmental impacts and is detrimental to the safety of the plant. The following parameters affect the viability of the plant and may, therefore, be monitored to keep the plant’s efficiency as high as possible: •
fuel composition
•
fineness of grind
•
flue-gas composition (O2, CO2, CO)
•
air mix and flue-gas volume flow
•
air leaking into the combustor
•
boiler fouling
•
temperatures of the combustion air and flue-gases
•
temperature behaviour within the heating surfaces
•
reduction of draught
•
flame profile
•
combustible proportion of residue (annealing loss)
9.3
Generic Technical Measures to improve Large Combustion Plant's Efficiency
9.3.1
Combustion
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combustion is supplied to the boiler. Furthermore, a small percentage of the fuel does not fully combust. The flue-gas temperature must be kept high enough to prevent condensation of acid substances on the heating surfaces.
9.3.2
Unburned Carbon in Ash
Optimisation of the combustion leads to less unburned carbon-in-ash. It should be noted that NOX abatement technologies using combustion modification (primary measures) show a tendency of increased unburned carbon. Increased unburned carbon could also worsen and harm the quality of the coal fly ash and make it difficult, or even prevent, their utilisation for certain applications, with the risk that they may not comply with the specifications and requirements laid down in relevant national and European standards.
9.3.3
Air Excess
The amount of excess air used depends on the type of boiler and on the nature of the fuel. Typically, 12 – 20 % excess air is used for a pulverised coal-fired boiler with a dry bottom. For reasons of combustion quality (related to CO and unburned carbon formation), and for corrosion and safety reasons (e.g. risk of explosion in the boiler) it is often not possible to reduce the excess air levels further.
9.3.4
Steam
The most important factors in increasing efficiency are the highest possible temperature and pressure of the working medium. In modern plants the partially expended steam is reheated by one or more reheating stages.
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9.3.5
Flue-Gas Temperature
The flue-gas temperature leaving the clean boiler (depends on the fuel type) is traditionally between 120°C and 170°C, due to risks of acid corrosion by the condensation of sulphuric acid. However, some designs sometimes incorporate a second stage of air heaters to lower this temperature below 100°C, but with special claddings on the air heater and the stack, which makes this reduction economically unprofitable. By power plants designed without stacks, the flue-gas temperature is between 65 and 70°C.
9.3.6
Vacuum in the Condenser
After leaving the low-pressure section of the steam turbine, the steam is condensed in condensers and the heat released into the cooling water. In order to ensure the maximum pressure drop over the steam turbines, it is desirable to reduce the vacuum to a minimum. In general, the temperature of the cooling water dictates the vacuum, which is lower with once-through cooling systems than with a cooling tower. The best electrical efficiency is possible by seawater or fresh water-cooling and a condenser-pressure with approximately 3.0 kPa. The preferred option is to use seawater or river water if this available.
9.3.7
Variable Pressure and fixed Pressure Operation
In fixed pressure operations, the pressure before the turbines at all load levels is kept more or less constant by changes in the flow cross-section at the turbine inlet. In variable pressure operations with the turbine inlet cross-section at its maximum, the power output is regulated by changes in the pressure before the turbines.
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9.3.8
Condensate and Feed-Water Preheating
The condensate coming out of the condenser and the boiler feed-water are heated by steam to just under the saturation temperature of the extracted steam. The thermal energy from the condensing process thus feeds back into the system, reducing the amount of heat otherwise released from the condenser, therefore improving the efficiency. The optimisation measures taken to improve the efficiency of power plants between 1993 and 2000 which resulted in a CO2 reduction of 11.0 million tonnes per year as shown below: Steam generator
39 %
Process optimization
14 %
Turbine
25 %
Auxiliary power
14 %
The reduction of emissions from large combustion plants can be carried out in different ways.
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10.
Energy Balance
Following figure shows an energy flow chart (Sankey diagram) of the individual losses within the heat flow of a condensation power plant. Figure 10-1: Sankey diagram of individual losses
E ner gy flo w in a 200 MW po wer u n it, lay o u t des ig n : & ) 167.8 kg/s; 245 bar/520 °C Mass flow live steam ( m s First intermediate superheating 78.5 bar/530 °C
Second intermediate superheating 22 bar/540 °C Condenser pressure approx. 0.0235 bar Feed water end preheating 303.6 °C (nine preheater stages) a) Flue gas – air preheating
H) Circulation losses (water and steam)
b) Feed water preheating
I) Turbine losses
c) Fresh air
K) Thermodynamic cycle (water & steam)
d) Make-up water
L) Losses of generator
e) Feed pump turbo set
M) Auxiliary consumption, overall
A) Fuel energy input
N) Auxiliary consumption of the turbine installation
B) Losses due to radiation and unburnt material
O) Auxiliary consumption of the steam generators
C) Exhaust gas loss
P) Steam generator output
D) Ash losses
Q) Turbine output
E) Pipe losses
R) Generator output
F) Loss of the feed pump turbo set
S) Effective useful output
G) Heat loss of the preheating installation
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When analysing the efficiency of conventional power plants, it must be taken into account that the fuel costs amount to approximately 75 % of the total average production costs, which clearly shows the necessity of operating the plant at optimum efficiencies. Not only
cost-effectiveness is required, but also the reduction of the emission of air-polluting substances by saving fuel.
10.1
Efficiency of German Power Plants
Efficiencies in German power plants vary widely and keep increasing due to enhancements of the power plant technology. At present, the data summarised in the following Table 10-1 can be assumed. Table 10-1:
Efficiency of German Power Plants
Power plant type
Net electrical efficiencies in % Current optimum
Target
values
values
Natural gas and steam power plant with condensation
55 – 58
60
Fossil fuel steam power plant with condensation
40 – 48
50
Natural gas turbine power plant
30 – 36
40
Closely connected to the efficiency of a condensation power plant are the process losses, also called cooling water losses or condensation losses. For physical reasons it is impossible to avoid them in a condensation power plant. They are the biggest losses and therefore strongly reduce the power plant efficiency. They are determined by the type of steam power cycle: 1.
the design of the water-steam circuit (e.g. with or without intermediate superheating)
2.
the pressures and temperatures of the live steam and superheated steam
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3.
the cooling water temperature and, connected to it, the condensation pressure
4.
main condensate and feed water pre-heating
One practical solution for the exact determination of the losses or efficiencies is to monitor the heat output and the generated effective output (kW). The heat capacity (kJ/s, MJ/s) is the heat input into the process for a certain time unit.
10.2
Efficiency Degradation
The degradation of the plant efficiency is a normal process, but a permanent challenge to minimise the degree of degradation. State of the art of plant operation and maintenance is to keep the degradation level between the ranges of +/- 0.1 % net efficiency. This impressive figure is the outcome of a well equipped plant in terms of monitoring and cleaning system. The major components of the monitoring system are stress gauges, temperatures measuring and vibration control devices and software tools to calculate heat balance, frequency analysis etc.: The major cleaning systems are water conditioning, condenser cleaning and soot blowing systems. The backbone of these systems is a state of the art process control & instrumentation system allowing the record of any relevant data. The targeted systems respectively indicators are heat transfer decrease in the boiler caused by ash deposits, heat transfer decrease in the condenser caused by fouling effects, air control of the boiler island, avoidance of corrosion in the boiler and pipe system by the well suited operation of the Electrostatic Precipitator and last but not least the turbine island – vibration and frequency control.
10.3
Energy Balance of a Coal-Fired Power Plant Unit
As an example, two energy balances are drawn up for a German coal-fired power plant with a useful output of 830 MW. In one case the steam generator forms the balance limit, D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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in the other one it is the boiler house. The energy balances were drawn up by means of measured values, which were found in a field test for the determination of the unit heat consumption. During the measurements, 100% of the combustion air was taken from the boiler house (internal suction) at a temperature of 55°C. Preheating of the combustion air in relation to the ambient air amounted to 45°C, which corresponds to a heat quantity of 18.5 MW. Yet the radiation and pipe losses at the steam generator according to DIN EN 12952-15 amount to only 2.43 MW. The examination of the supplied heat flows for both energy balances shows a difference of 15.5 MW. This difference is based on the difference between the actual radiation and pipe losses and the radiation and pipe losses as determined according to DIN EN 12952-15. This means that the choice of different balance limits leads to differing at the time of calculating the heat flow input of the fuel heat input. These differences directly influence the calculation of the boiler efficiency and the unit efficiency, where the error amounts to approximately 0.5 % points for the unit efficiency. The radiation and pipe losses of the respective steam generators are included as lumpsum figures in the "indirect method" according to DIN EN 12952-15, depending on the maximum useful heat output. As the measurement results of the different coal-fired power plant units show, the amounts of losses determined that way do not correspond to the actual radiation and pipe losses of the steam generators. If this method is applied in practice, the following consequences result from it: •
Especially for steam generators operated with internal suction, it is not possible to draw up conclusive balance limits. For heating up the combustion air within the steam generation building, the amount of "recovered" energy is much bigger than that which is radiated by the boiler according to the current regulations.
•
The choice of different balance limits around the steam generator leads to differences in the calculation of the fuel heat input. The deviations resulting from this directly affect the unit efficiency.
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Output 1.1 Figure 10-2: Energy balance for the steam generator
Boiler house
tL,env =
10,0 °C
mLhL =
-6,0 MW
(QSt+QV)back =
15,5 MW
tsupply =
25,0 °C
tL,sb =
55,0 °C
mLhL =
12,5 MW
QSt,tot =
13,5 MW QV =
Pfan =
3,0 MW
QN,sb =
831,0 MW
3,0 MW
Steam generator Pcomill =
2,0 MW
Pcomill =
2,0 MW
QA =
53,0 MW
mB(Hu+hB) =
891,0 MW
mB(Hu+hB) =
891,0 MW
QS,F =
8,0 MW
supplied heat flows
supplied heat flows
-6,0 MW
13,5 MW
+
3,0 MW
+
831,0 MW
+
2,0 MW
+
2,0 MW
+
53,0 MW
+
891,0 MW
+
891,0 MW
+
8,0 MW
total
890,0 MW
total
905,5 MW
total
905,5 MW
Efficiency, limit of balance steam generator Efficiency, limit of balance boiler house
10.4
dissipated heat flows
12,5 MW
91,77% 93,03%
Operating efficiency in European Power Plants
The following Figure 10-3, Figure 10-4 and Figure 10-5 show the attainable efficiency of power plants and comparison of various technologies such as IGCC, super critical, nuclear, gas turbine etc in addition to technology perspectives and incremental efficiency improvement in power plants.
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Output 1.1 Figure 10-3: Comparison of efficiency of various types of power plants (Source VGB)
Figure 10-4: Technology perspective in terms of efficiency (Source VGB)
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Output 1.1 Figure 10-5: Efficiency improvement of coal fired boilers (Source VGB)
The efficiencies are evaluated based on the following formula:
Efficiency =
Net kWh Energy Input as NCV
The complexity of thermal power plant efficiencies reporting in India and Germany are given in annexure VIII. The various formulas used for estimation of thermal power plants are given below:
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10.5
Operating Efficiency of typical Indian Power Plants compared to German Power Plants
The following gives the variation in efficiency figures due to evaluation criteria for a typical Indian power plant of 500 MW. Basis for calculation (typical design values) •
Gross rating of the plant
500.15 MW
•
Turbine gross heat rate
1944.6 kcal/kWh
•
Auxiliary power
8.00 %
•
Auxiliary power
40.012 MW
•
Net power output
460.138 MW
•
Coal consumption
278.5 t/h
•
Coal GCV
4,000 kcal/kg
•
Coal NCV
3,758 kcal/kg
•
Fixed carbon
28 %
•
Volatile matter
22 %
•
Moisture
20 %
•
Ash
30 %
Coal analysis
The efficiencies, as described in chapter 10.4 could be determined as follows: •
Efficiency # 1 (based on net kWh & GCV)
35.52%
•
Efficiency # 2 (based net kWh & NCV)
37.81 %
•
Efficiency # 3 (based on gross kWh & GCV)
38.61%
•
Efficiency # 4 (based on gross kWh/NCV)
41.10%
For comparison the typical efficiency of German power plant is given to •
Gross rating of the plant
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•
Turbine gross heat rate
1,944.6 kcal/kWh
•
Auxiliary power
10.80 %
•
Auxiliary power
54 MW
•
Net power output
446 MW
•
Coal consumption
189.7 t/h
•
Coal GCV
5,615 kcal/kg
•
Coal NCV
5,386 kcal/kg
The efficiencies, as described in chapter 10.4 could be determined as follows:
10.6
•
Efficiency # 1 (based on Net kWh & GCV)
36.01 %
•
Efficiency # 2 (based Net kWh & NCV)
37.54 %
•
Efficiency # 3 (based on Gross kWh & GCV)
40.37 %
•
Efficiency # 4 (based on Gross kWh/NCV)
42.09 %
Comparison of published efficiencies
Comparison of published efficiency values for different types of power plant is difficult for several reasons: •
Differences in the calculation of the heating value of the fuel
•
Differences in site conditions and especially condenser pressure
•
Differences in plant design, such as single or double stage reheat at otherwise a similar plant design
•
Consideration of gross or net efficiencies (and plant output), use of add-on equipment such as for example a flue gas desulphurisation
The condenser pressure is commonly the most important factor, and going from a condenser pressure of 0.05 bar, which requires a cooling water temperature of 27-28°C, to 0.02 bar, with a cooling water temperature of 14-15ºC, produces an extra three percentage points. Thus, for proper comparisons, all actual plant efficiencies ought to be recalculated to 'standard conditions' in order to be meaningful.
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In Europe, efficiencies are expressed on the basis of lower heating value (LHV), which is the difference between the higher heating value (HHV which is the total amount of energy contained in the fuel) and the latent heat of evaporation of the water contained in the products of combustion. In Europe, evaluating efficiency by considering the LHV is considered accurate assessment of the 'useful' energy of the fuel for plant where this water goes to the atmosphere in the flue gas stream. The ratio of HHV to LHV depends on coal composition and its heat content. For fuels such as natural gas and biomass with higher hydrogen content, this ratio will be much higher. This complicates comparisons between different technologies and fuels. When generating efficiencies are quoted as based on HHV, the electricity output is divided by the HHV of the fuel used. When they are quoted on an LHV basis, the output is instead divided by the LHV value of the fuel. Consequently, HHV generating efficiencies are lower than LHV generating efficiencies. For example, a coal-fired steam plant with an HHV efficiency of 40% has an LHV efficiency of approximately 42 %, provided plant design and site conditions are the same. A broad understanding of the current status of coal-based power plant can be gained from a comparison of several state-of-the-art steam plants around the world, as illustrated below (Table 10-2): Table 10-2:
Differences in efficiency based on HHV and LHV (Source: www.berr.gov.uk/files/file30703.pdf)
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The Japanese and US plants have relatively high condenser pressures compared to the Danish plant. The Niederaussem plant burns a lower grade lignite, whereas the others are fuelled with bituminous 'trading' coals.
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11.
Key parameters and basis for measurements
11.1
Key operating parameters
Coal fired power plants built are based on the proven and fully developed engineering. The major key operating parameters of power plants are main steam pressure, main steam pressure and condenser vacuum. The hard coal fired power plants, designed for net efficiency in the region of 45%. The following table (Table 11-1) shows the development of boiler efficiency based on the improvement in main steam pressures and temperatures along with related operating parameters. Table 11-1:
Development of boiler efficiency based on improvement in steam pressures, temperatures and other parameters
Parameter
Unit
#1
#2
#3
#4
#5
#6
#7
#8
#9
Efficiency
%
41.0
41.2
41.5
41.6
42.5
42.6
42.8
43.7
44.3
Improvement
%
0
0.5
0.8
0.25
2.0
0.3
0.5
2.0
1.3
Main steam
bar
250
250
250
250
250
300
300
300
300
°C
260
280
280
280
280
280
300
300
300
°C
530
530
540
540
540
540
540
580
580
°C
540
540
560
560
560
560
560
600
600
Condenser
bar
0.047
0.047
0.047
0.047
0.047
0.047
0.047
0.047
0.04
Exhaust gas
°C
130
130
125
125
125
125
125
125
125
pressure Feed water temperature Main steam temperature Reheater steam temperature pressure
temperature
It can be seen that the efficiency is raised as steam pressures and temperatures are raised while the flue gas exhaust temperature and condenser vacuum lowered. Similarly, the following table (Table 11-2) gives the parameters for lignite based power plants. Table 11-2:
Typical boilers operating parameters Parameter
Dim.
Neurath
Schwarze
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Boxberg
Lippen
Niederaussem
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Efficiency
%
Unit E
Pumpe
35.5
40.6
41.7
dorf
Unit K
42.3
45.2
Improvement in efficiency
%
14.4
2.7
1.4
6.9
Main steam pressure
bar
165
262
266
267
269
Feed water temperature
°C
235
274
270
295
Main steam temperature
°C
525
547
545
554
580
Reheater temperature
°C
525
565
581
583
600
Condenser pressure
bar
0.66
0.035/0.046
0.041
0.038
0.028/0.034
In addition to the above the following Table 11-3 summarizes key operating parameters of different power plants in Europe. Table 11-3:
11.2
Key operating parameters of the power plants in Europe
Fuel Parameter
Coal is a natural product. For this reasons its chemical, physical and technological properties depend on the herbal starting substances and the geometrical conditions during carbonisation. The knowledge of chemical, physical and technological properties of coal is of utmost importance for its use as fuel in combustion plants. A German Standard, DIN 51700, defines the most important analysis procedures for the uniform description of properties of solid fuels. To assess the coal, a distinction is made between the pit coal as delivered and the water D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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and ash-free substance (waf). The moisture and ash-free substance contains only the burnable parts of the solid and volatile elements. Prerequisite for smooth operation are the knowledge of and information about these characteristics and properties. The following overview shows the most important characteristics: •
Calorific value
•
Ash content
•
Water content
•
Volatile elements
•
Sulphur content
•
Elementary analysis of the ash
•
Melting behaviour of the ash
•
Mineral size fraction of the pit coal
•
Composition of the mixture
•
Elementary analysis of the coal
•
Apparent weight
•
Grinding fineness of the pulverised fuel
•
Grindability of the coal
The details of the above listed characteristics are given in annexure IX. 11.3
Air & Flue Gas Parameters
The detailed parameters under this category need to be measured/monitored are given as well in the annexure IX. To determine the individual efficiency, the following parameters have to be measured in individual systems: electrical power, pressure, temperature, mass flow, differential pressure and oxygen content. When the measuring data are determined, wear, pollution and leakages have to be taken into account; at least they should be documented. 11.4
Data required
The data required for assessing the effeminacy, output, performance etc given in the D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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annexure IX. •
Table 1:
Parameters required for efficiency determination by energy balance method (Source ASME PTC 4)
•
Table 2:
Parameters required for efficiency determination by inputoutput method
•
Table 3:
Parameter required for capacity determination
•
Table 4:
Parameters required for steam temperature /control range determination
•
Table 5:
Parameters required for excess air determination
•
Table 6:
Parameters required for water / steam pressure drop determination
•
Table 7:
Parameters required for air / flue gas pressure drop determination
•
Table 8:
Parameters required for air infiltration determination
•
Table 9:
Parameters required for fuel, air and flue gas flow determination
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12.
Official Statistics for Efficiency Indicator and Plant Reliability
Each member state of the European Union is obliged to deliver statistical data. The energy sector takes an essential part in the statistics. Special focus is laid on plant efficiency and plant reliability. Special investigations are often made in order to allow an in depth analysis of specific topics. An example is the report of the EU Joint Research Centre, JRC. In addition to the basics the analysis and tools are essential elements to judge a power plant process and appraise it in the whole complexity. With this knowledge and the fact that the single component or single systems have to be measured prepared can a basic measurement be accomplished. But at first specific data are essential. To furnish single countries in Europe, and the very different regions over there, with energy, it is important to be aware of a few facts about the development, afforded power amount and coal consumption. The details about the common technical processes, general fuel heat conversion in boilers, typical elements of a steam cycle are given in annexure X.
12.1
Reports on Analysis and Tools for Efficiency Indicators
Based on the selected and described indicators samples for standard reports used in the EU are given. These official reports are published by national authorities as well as 1.
Eurostat (the Statistical Office of the EU), "Energy, Transport and Environment Indicators" http://epp.eurostat.ec.europa.eu/portal/page?_pageid=0,1136052&_dad= portal&_schema=PORTAL
2.
EU Joint Research Centre, "Reference Document on Best Available Techniques for Energy Efficiency", and download possible under http://eippcb.jrc.es/pages/FActivities.htm (scroll down to "Energy Efficiency" and download the draft document)
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12.2
Excerpts from Eurostat-Document
As official statistics Eurostat has published newest energy indicators for example on energy intensity, gross inland consumption per capita et al. The extracts are given in the annexure XI.
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13.
Performance Indicators & Monitoring
13.1
Introduction
In the liberalized energy market the evaluation of the performance of an own power plant compared to other power pants (benchmarking) is of great importance. To optimise the performance of a power plant in competition: •
the compilation of availability data and evaluation of performance indicators and
•
the comparison of indicators of a single plant with the indicators of peer groups
are strategic tools for many VGB-member-companies. In performance indicators and monitoring of the power plants VGB is very active and is collecting data and information from members' power plants since 1970. The data provide the information about the availability and utilisation of the thermal power plants in order to compare the quality of the power plants and to assess plants behaviour in daily operation. The basic tasks involved in the performance monitoring are •
Collecting of power plant performance indicators with the help of the VGB online power plant information system KISSY (KISSY is power plant information system which include collection and evaluation of performance indicators) As these as these strategic tools were of great importance for power plant operators during the last thirty years the hitherto used old dBase related tool was replaced by a new modern online-power-plantinformation-system KISSY, which is discussed more in detail. With the aid of KISSY, benchmarking can be carried out efficiently.
•
Determination of conventions for the publication of performance data of power plants
•
Preparation of availability- and unavailability reports
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•
Definition of new performance indicators for comparative assessment of the performance of power plants in the liberalized power market
•
Management of road shows for performance indicators and power plant benchmarks
•
Appropriate guideline updating
The major parameters monitored for performance of power plants in Europe are: •
Time availability
•
Energy availability
•
Time utilisation
•
Energy utilisation
•
Start-up reliability
Time availability The time availability is the quotient of the available time and the reference period (calendar time). The available time is the difference between the reference period and the unavailable time.
kt =
kt tv
tN
tv tN Dimension
Time availability
h
Available time
h
Reference Period
h
Energy Availability The energy availability is the quotient of the available energy and the nominal energy. The available energy is the difference between the nominal energy and the unavailable energy. The nominal energy is the product of the nominal capacity and the reference period (calendar time).
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kW
Wv
WN
PN tN
kW =
Wv WN
kw =
WN − Wv PN ⋅ tN Dimension
Energy availability
-
Unavailable energy
MWh
Nominal energy
MWh
Nominal capacity
MWel
Reference Period
h
Time utilisation The time utilization is the quotient of the operating time and the reference period (calendar time). The time utilization is a measure for the real temporal use of a plant. It is independent of the level of the corresponding operating capacity.
nt =
nt
tB tN
tB tN Dimension
Time utilisation
-
Operating time
h
Reference period
h
Energy utilisation The energy utilization is the quotient of the energy generated and the nominal energy. The nominal energy is the product of the nominal capacity and the reference period (calendar time). The energy generated is the product of operating capacity and operating time (numerator).
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The energy utilization is a measure for the energy, which a plant has really generated. Frequently used are also the equivalent definitions "utilization duration" or "full load utilization hours" The correlation between energy utilization and utilization duration
nw
WB
WN
PN tN
nw =
WB WN
=
WB PN ⋅ tN
tN =
WB PN
=
n w ⋅ tN
Dimension Energy utilisation
-
Energy generated
MWh
Nominal energy
MWh
Nominal capacity
MWel
Reference period
h
Start-up reliability The start-up reliability is the quotient of the number of successful start-ups (se) and the sum of successful (se) and unsuccessful start-ups (sn). The start-up reliability is used for the evaluation of units whose service life depends essentially on the number of start-ups, e.g. gas turbines, emergency aggregates.
z=
se se + sn Dimension
z se
sn
Start-up reliability
-
Number of successful start-ups
-
Number of unsuccessful start-ups
-
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Classification of unavailability (NV) Planned unavailability: The beginning and duration of the unavailability have to be determined more than 4 weeks before commencement. Unplanned unavailability: The beginning of unavailability cannot be postponed or only up to 4 weeks. Post-ponable unavailability: The beginning of unavailability can be postponed more than 12 hours up to 4 weeks. Not post-ponable unavailability: The beginning of unavailability cannot be postponed or only up to 12 hours. These performance indicators are also basics of any benchmarking approaches (see chapter 15).
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14.
Software and Analytical Tools for Efficiency and Plant Reliability – Online and Offline
14.1
Introduction
The cost pressures in the power generation business force the power plant operators to take specific measures to improve the operating efficiency and reduce cost. Intelligent evaluation of existing in-service measured data using online and off line analytical tools is one efficient way to recognize the current potential for optimisation by assessing the processes and components. The benefits of online & offline software analytical tools are •
enhance the efficiency of your power plant operation,
•
arrive at maximum electric output that can be generated at the moment taking into account operational and technical constraints
•
computation of ratios and key figures (efficiencies, electric energy from cogeneration, start up cost, etc.)
•
comparison of performance indicators
•
component evaluation (steam generator, heat recovery steam generator, steam/gas turbine, steam- water cycle, condenser, pumps, flue gas circuit, etc.) for optimum and efficient operation
•
optimisation (example: soot-blowing, gas turbine compressor washing, cold end, etc.)
•
forecast (unit efficiency, maximum unit output, etc.)
•
measured-data reconciliation featuring neuronal plausibility checking
•
central alarm-signalling service system
•
individual "what if" process simulation
•
closed-loop operation
•
Individual daily, monthly reports, statistics
•
diagnosis and analysis
•
several others
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14.2
Software Analytical Tools / Modules
Several software analytical modules are available in EU, which are specifically designed for power plant for plant monitoring and optimisation. The typical systems, which are predominant in EU, are: •
General statistics for official use
•
Specific industry driven data collection and compilation tools
•
Systems for optimum operation (Which cover energy management systems / plant optimisation system /system services/systems integration – all in a single module package or individual modules)
•
Lifetime monitoring system
•
Data management system -including subprograms
•
Thermodynamic cycle calculation program – offline monitoring system
The above systems can be installed separately or as a combination with others. The details of these systems are given below:
14.3
Data Collection for the Performance Monitoring
For detailed analysis required data pertain to the above parameters from the power plants are collected very meticulously by VGB: More than 471 power plants across Europe is covered. The data were considered will be fed to the KISSY for the detailed analysis and review. The performance monitoring is carried out by data collection for various types of power plants such as: •
Fossil-fired units
•
Nuclear power plants
•
Combined cycle units
•
Gas turbine units
•
Capacity type
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•
•
Until 99 MW
100-199 MW
200-399 MW
400-500 MW
600 and above
All units
Fuel type by capacity
Bituminous coal fired units
Lignite fired units
Oil /Gas fired units
Furnace type by capacity
Bituminous coal fired units with dry bottom firing
Bituminous coal fired units with slap top firing
•
Units by single or dual boilers
•
Units by subcritical or supercritical pressure
The above units will be considered as total Europe, in addition the entire exercise will also be carried out for Germany Units.
14.4
Analysis for Performance Monitoring
The analysis covers about 217 power plants for the operating period po1997 to 2006. The information analysed for various parameters such as: •
Failure with out damage
•
Damage
•
Check/condition check
•
Lubrication
•
Maintenance
•
Inspection\
•
Preventive maintenance
•
Cleaning
•
Revision
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•
Refuelling
•
Reconstruction/refurbishment
•
Test/functional tests
•
Official test/measure
•
Other incidents
The above analysis is carried out for unavailability incidents per block and year and also for energy unavailability. The analysis will also include on equipment basis such as:
14.5
•
Power transmission
•
Distribution of solid fuels
•
Pressure system, feed water and steam sections
•
Support structure, enclosure, steam generator interior
•
Ash and slag removal, particulate removal
•
Bunker, feeder and pulverising systems
•
Main firing system
•
Combustion air system (primary and secondary)
•
Flue gas exhaust
•
Chemical flue gas treatment system including residual removal
•
Feed water system
•
Steam system
•
Steam turbine plant
•
Generator plant
•
Circulating water system
KISSY
KISSY is Power-Plant-Information-System is a relational data base system on an oracle platform. It currently covers availability data and performance indicators of over 9760 unit years of German and other European power plants. Every full member of VGB can feed data to KISSY data base and at any time read the complete data of his own power plants online D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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via internet. The relevant availability data and performance indicators, which have to be collected and analysed for benchmarking are defined and explained in VGB-guidelines. The new kind of operating power plants initiated by the liberalised market requires the consideration of further performance indicators as for instance •
indicators for commercial availability
•
damage- and condition-oriented indicators
which will be incorporated with the next planned enhancement of KISSY. Every full member of VGB which wants to feed availability data can get access to the KISSY database. Members will get username and password by VGB. Then they can feed, change and read data for their own power plants online via a secure access (SSL-encryption). Data of other power plants are not visible to them via internet. The System will guide on,
which availability data and which data for reporting unavailability incidents have to be collected. Additionally the basic data of the power plant units (see attachment E) have to be fed once
into the database by VGB in order to assign the units to their peer groups for analysis and reporting. The analysis of the anonymous data is done for peer groups by VGB. The data fed by members via internet into the KISSY data base will be transformed anonymous by VGB and related to peer groups for benchmarking. Peer groups cover data of power plants with similar characteristic attributes which therefore can be compared (anonymously) with respect to their performance. Main peer groups for standard reports are: •
fossil-fired units
•
nuclear units
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•
combined cycle units
•
gas turbine units
Arranged by: •
capacity
•
fuel
•
type of firing
•
single/dual boiler
•
sub- / supercritical
Analysis is done for: •
time availability
•
time utilization
•
energy availability
•
energy unavailability
•
energy utilization
All members, which feed data into the KISSY data base get for free the standard reports for the above mentioned peer groups with analysis of key figures of availability and unavailability of components (for the previous 10-years period) annually. Current reports are available for downloading on VGB`s website within a closed user group area for VGB-members only. These reports will be updated every 3 months. For other parties the standard reports are available at VGB Power Tech Services. The detailed procedure in using KISSY is given in annexure XII.
14.6
Systems for Optimized Operation
These are online tools to cover energy management systems / plant optimisation system / system services/systems integration.
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These online analytical tools continuously assess plant operation, comparing it with a current calculated optimum so that the unit can be run at maximum efficiency. These tools are normally based on a three-tiered concept – evaluation, optimisation and forecast for cost-relevant power plant sections. Potential for optimisation is indicated, and even minimal reductions in efficiency are pinpointed. All results are evaluated at cost so that the effects of different operating parameters can be directly compared. The most important task of the plant optimisation system is to monitor the current plant operation and to compare it with the currently possible optimum on a continuous basis. The calculations needed for this are executed automatically on the basis of the current mean values of this time class. The results are saved in the related time archive in the Data Management System and can thus be visualized in the same way as all other data. Two different concepts are followed for the plant diagnosis is •
The optimisation of the plant operation and
•
The monitoring of the components or parameters.
For further details please refer to annexure XXII. A.
Plant Optimisation Systems
The plant optimisation system combines and presents thermodynamic models of the Plant components with economic parameters, specifically variable operation costs, to determine the current deviation between actual and the corresponding optimum plant operation. The thermodynamic modelling takes into account limiting constraints of operation. The plant optimisation also includes an off line manual (what if) analysis tool that enables the user to conduct model-based analysis of plant operation. Plant optimisation system includes the following: •
Thermal cycle optimisation. This computes the entire turbine and regenerative cycle heat balance and simulates the plant so that operator can examine the improvements in heat rate and can change individual cycle parameter.
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•
Computes the boiler efficiency and simulates boiler parameters such that operator can examine the improvements in boiler efficiency.
•
Boiler tube life fractions and stress calculations.
The features of standard graphical representation of the complete package based on Process Flow Diagram and the P&ID are included. The graphic screen is developed in order to enable that the user to conduct model-based analysis of Plant operation and get the results in an understandable manner. The tool includes all required drawings and graphical representation of the total plant system covers all equipment and drives related to the Optimisation package. Process graphic displays will be developed by the power plant operator to have a complete overview of the package indicating the display of equipment of boiler and turbine auxiliaries. The dynamic data is clearly being indicated such that the operator need not refer to multiple diagrams to assess system operation. Arbitrary continuation break points between displays are not used in such systems. B.
Functional Requirements
The plant optimisation functions are based on model-based software. The system computes controllable losses related to plant parameters not being maintained at their design points based on actual loads. The model is also including option to identify equipment cleanliness for various heat transfer sections within the plant. The optimisation software also identifies the actual sequence of soot blowing so that costs of heat loss due to unclean heat transfer sections and the costs of soot blowing can be minimized. Typical Plant Optimisation System will perform the following functional requirements. C.
Boiler Stage Optimisation
The system incorporates complete thermal design. This provides a continuous on-line, cost-benefit assessment of where and when i.e., the actual sequence, to blow soot from individual boiler stage surface areas. The boiler optimisation calculations take into account the following factors:
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•
Main steam conditions
•
Hot reheat conditions
•
Fuel inlet conditions
•
Ambient air conditions
•
Soot blowing usage
•
Gas exit temperature
•
Leakage of air pre-heater
•
Boiler efficiency
•
Heat rate
With boiler optimisation model, operators can obtain a ranking of cost/benefit of soot blowing on monitored boiler stages. The boiler optimisation model will be developed for the following sections: •
Economizer
•
Water walls
•
Super heaters
•
Reheaters
•
Air heaters
The radiative heat transfers, convective heat transfers and heat & mass balance equations are used to generate the above models. High degree of boiler cleanliness shall thus be ensured. D.
Soot Blowing Optimisation
Soot blowing optimisation advises operators to clean boiler stages at appropriate time and location to optimise soot-blowing operation. The high quality boiler calculation advises the operator judicious soot blowing of boiler stages. The boiler cycle monitoring calculations provide the following results: •
Cleanliness factors on boiler stages
•
Furnace exit gas temperature
•
Flue gas temperatures between boiler stages
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•
Actual heat transfer coefficients for each boiler stages
•
Theoretical heat transfer coefficients for each boiler stages
•
Flue gas cross-flow velocities
•
Stage heat absorption
•
Stage average metal temperatures
•
Specific heat of both air and gas
•
Excess air
•
Stage cross flow velocities
Normally a suitable combustion model will be included in the software. E.
Thermal Cycle Optimisation
This module computes the entire turbine and regenerative cycle heat balance and simulates the section of the plant so that operator can examine the improvements in heat rate attainable by changing a cycle parameter. The turbine and regeneration cycle is modelled such that any change of boiler parameters can be examined in relation to the overall heat rate of the plant for what if-scenarios. The turbine optimisation model is normally developed for the following sections: 1. Turbine HP/IP/LP 2. Condenser 3. Deaerator 4. Feed water heaters 5. Pumps (Condensate, Boiler feed) For turbine performance optimisation standards such as ASME PTC6 "Enthalpy Drop" efficiency calculations for determining turbine efficiency will be applied. In monitoring turbine cycle performance the following parameters are calculated: •
Main steam flow
•
Reheat flow
•
Condenser steam flow
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•
Turbine stage flow
•
Individual turbine stage efficiencies
•
Overall HP, IP, LP turbine efficiencies
•
Turbine calculated wheel power
•
Turbine calculated exhaust enthalpies
•
Turbine calculated exhaust velocities
•
Cold reheat steam approach to saturation temperature
•
Superheat spray outlet approach to saturation temperature
•
Expansion line end point at condenser pressure
•
Used energy end point
The power plant personnel provides component degradation tool package, which evaluates heat rate and cost effect of the components detailed below. The calculable losses identify the losses associated with equipment degradation and those associated with nonmaintenance of design parameters independently. •
HP Turbine, IP Turbine, LP Turbine
•
Feed Water Heaters,
•
Condenser
•
Boiler Feed Pumps
•
Deaerator
•
Boiler
•
Turbine Extraction line
•
Condensate pumps
•
Heat Exchanger
In these packages, the turbine stages are considered as long as the steam is still dry at the respective outlet. Since the tools contain a thermodynamic model of the process, losses of the generator cannot be determined. For the same reason steam seal regulators cannot be modelled. However, if necessary, the leakage through the steam seal may be considered as boundary condition. In addition, overall system degradation can be evaluated. Graphical presentation of results will be furnished as a part of the optimisation guides provided to the operator. These will D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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be in the form of bar charts, X-Y plots, and plant mimics. Predictive and diagnostic tools package is adopted in the form of ‘What if’ for diagnosing plant degradation. Those included in the ‘What if’ analysis are the following items, which can be modified by the user to see the effects on plant generation, heat rate and boiler efficiency: •
Throttle pressure
•
Throttle temperature
•
Reheat temperature
•
Condenser backpressure
•
Superheat spray flow
•
Reheat spray flow
•
Final feed water temperature
•
Boiler excess air
•
Flue gas exit temperature
•
Heater bypass
•
Feed water flow
•
Boiler feed pump efficiency
•
Boiler feed pump discharge pressure
•
Feed water heater terminal temperature differences
•
Feed water heater drain cooler approach
•
Turbine stage efficiencies
•
Condenser cleanliness factors
•
Condenser circulating water inlet temperature
•
Circulating water flow
•
Fuel ultimate analysis and heat content
•
Fuel firing rate
•
Boiler stage cleanliness factors
•
Gas re-circulation and tempering
•
Unburned carbon
•
Bottom ash and top ash removal
•
Air heater leakage
•
Ambient air condition
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This package can also be used to evaluate the effects of the following: •
Changing operating conditions and load
•
Comparing test data to best attainable and evaluating the results after ASME correction
•
Changing boiler stage geometry to evaluate the effects on steam and exit temperatures
14.7
Lifetime Monitoring System
The basic objectives of this type of tool are: •
Improved maintenance planning
•
Faster connection to grid
•
Better exploitation of material
Components of power plants exposed to high temperatures and pressures suffer serious material degradation during their lifetime. The appearance of the first cracks in the material indicates the need for component exchange or at least its repair. The degradation originates either from creep of the material caused by pressure induced stress or from fatigue caused by fluctuations of temperature and pressure in the component wall. Under certain stress conditions material creep increases strongly with temperature and decreases with wall thickness. On the other hand fatigue due to temperature induced stress increases with wall thickness. During the design of the component both types of stress are taken into account, leading to an optimum compromise in accordance with the respective design rules. Because the actual plant operation deviates more or less from design conditions, the accumulated material degradation is not proportional to operating time; that is why a regular monitoring of plant operation is recommended. The best way to carry out such monitoring is by continuously operating a data logger together with a data evaluation system. The Lifetime monitoring software system continuously records operating temperatures and pressures around all critical components of a power plant and from that calculate the D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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resulting contributions due to creep and fatigue. Thus the operator is kept well informed about the current status of the plant, especially about the remaining lifetime of the vital components. The mathematical algorithms follow the European standards. The systematic and continuous application of tool reduces the cost for routine maintenance inspections as well as additional tests. Because degradation of component parts is a long-time effect, it is permissible and, in case of malfunction, not avoidable that from time to time component degradation increases
disproportionately.
However,
the
operator
should
keep
in
mind
that
disproportionate degradation increases must be compensated by way of plant operation generating less than proportionate degradation increases, if the planned components lifetimes shall be maintained. Therefore, using SR1 the operator has an instrument suitable for well-aimed influencing the remaining lifetime at his disposal. For example, if the live steam temperature is willingly increased within the admissible range to improve the unit’s heat rate, the corresponding higher creep damage at least partly consumes the free margin possibly accumulated during previous operation, or the planned remaining operation time must be reduced. Analogously, by willingly shortening the start-up time of a boiler – thus saving start-up costs and connecting to the grid faster –increased lifetime consumption due to cyclic fatigue will be recorded. Accordingly the accumulated free margin will be reduced. The respective allowable curves are specific for each component. These curves will be adjusted automatically to the operation pattern recorded in the past. This dynamic adaptation provides the operator with a clear indication on the permissible operations for each monitored component. This type of tools can be employed successfully in many different power plant units either as stand-alone application or in combination with other modules like data reconciliation or optimisation of power plant operation. Normally such systems are designed to run on Windows NT as a client/server system. It includes a specific data management systems as well as a powerful visualisation module. The required data are exchanged with the process control system or with external data management systems via standard interfaces. For system handling and visualisation of D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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calculation results on the customer owned LAN/WAN licence free clients in any number are available.
14.8
Data Management System
The central component of all online systems is the data management system. In annexure XXII a detailed description of the important features of such system is provided. The essential task of this tool is the cyclic import and archiving of measurement values from the control system or from other data sources. Other data sources can be bus systems or online databases. A corresponding interface is provided for each type of data exchange. All other tools installed access this data through an internal interface, evaluate this data and save the results. This tool enables the automatic integration of data to higher time classes. The data is read by default in minute-cycles and integrated internally to 5’-mean values. All the optimisation calculations are done in this time class. Other integration levels are, for example, 15’-values, hourly values, daily values, weekly values, monthly values and yearly values. According to the respective system configuration, these or even other time classes are available. The entire data is saved in the related time-oriented archives. The system has subprograms for visualizing the archived data or for configuring the data management system. The data visualization enables the representation of any time series in diagrams as well as the representation of a point of time in a flow diagram. Diagrams can represent a maximum of 24 data points in up to 6 ordinates. The displayed time period as well as the time class (minute values or daily values, etc) can be selected freely. Along with the chronological display, ordered output curves or x-y-diagrams can also be selected. Along with line charts, bar charts are also possible. Special events or violations of limiting values can be signalled in the flow diagrams through automatic display of texts or through a corresponding colouring.
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14.9
Thermodynamic Cycle Calculation Program – Offline Tool
All the optimisation and evaluation calculations described above require a detailed thermodynamic model of the boiler and of the corresponding power plant process. This model is configured graphically with the help of the Cycle Calculation Program. This can be as offline tool. This tool provides a lot of components of power plants, which not only permit the modelling of the entire water-steam cycle, but also the detailed modelling of the steam generator. Similarly, essential components of the air and flue gas path can also be included in the modelling. Depending on the respective monitoring or optimisation task the required details of the model can be adjusted accordingly. This means that the boiler can be represented by an individual component within the water-steam cycle or it can be constructed from the main components heating surfaces, injections, combustion chamber as well as the connecting pipes. The water-steam cycle itself is constructed from the main components turbine, condenser, pre-heater and pumps as well as the connecting pipes. Especially the turbines are typically modelled as a combination of the individual turbine stages. This tool is a powerful tool to help the Power Plants/define areas of inefficiency component wise and total plant as a whole. The entire plant is first "mapped" by the Software to establish consistency of online data and compare with design parameters of the plant. The outcome of this exercise give a complete mapping of Power Plant configuration including equipment specification into a software that can simulate certain conditions and identify partial mismatches as well as wrong instrumentation display data. The power plant provides the data, which is used to do the mapping of the Power Plant. The Power Plant is mapped based on data input and validate data input by trial runs. This approach is interactive since initial power plant data provided will usually not match due to hidden or known instrumentation errors as well as inaccurate equipment and fuel specification. The objective is to demonstrate more innovative methods to conduct a baseline D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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performance assessment and map the results into software for further analysis and simulation for the benefit of the plant operators. This professional software is a mass and energy balance cycle calculation program – highly integrated into Windows. It is suitable for nearly all-stationary thermodynamic model requests coming out of energy cycles or plant schemes. The mathematical kernel of EBSILON is well known for its extreme convergence stability and for the high calculation velocity (see also annexure XXII). Not at least the last reason for several customers to use software is the user-friendliness which is ensured by 100 % Microsoft-conform, intuitive handling. Therefore it is – for this purpose – the most used software at several small and large companies as nearly a lot of manufacturers and utility companies in the German speaking Europe. Such software program is fully available also in English and French and there are customers in Netherlands, Poland, and Denmark and in China. The modelling is done by using a component library, which in the moment exists of all components as e.g. turbines, heat exchangers, boiler, pumps, generators, gas turbines, combustion chambers, tanks, gasifier, FBC, fuel cell, cooling towers dryer, filters, separators, fans, control elements, calculation modules, text fields, buttons, alarm fields etc. A customer programmable component allows by the use of C-knowledge the fully integration of self generated components. First the cycle is modelled topologically by using the component toolbox and the positioned components are then parameterized. All components are equipped with sets of default values. he sets are taken from a library, which can be modified and enlarged by the user. From this library also total and parts of cycles are eligible. Also a gas turbine library is available. For media properties different tables are available. Fuels (bituminous coal, lignite, gas, oil, hydrogen, biomass etc.) can also be used from a library. Flue gases etc. are nearly unlimited elementary definable or selectable from default compositions. This professional tool is so powerful that in one model also several power plants may be connected by power lines or steam and a district heating system still in a high detail can be calculated in one D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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model in some seconds. The Import and Export of data and results is possible via variety of Excel or ASCII interfaces as via DLL. All adjustments as visualization topics, physical dimensions (or British Units), are components dependent or general (also or fly) eligible. A very comfortable error analysis tool leads the user through this model to the error source. Beside exists a calculable example for every component as an online documentation for general questions. Figure 14-1: Typical mapping of a power plant
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In principle, this software does not restrict the detailing depth of the modelling. The characteristic lines or the characteristic fields for describing the thermodynamic behaviour of the individual components are determined on the basis of the design calculations or by evaluating the measurement values. In this way, the characteristics of the components for the entire load range can be determined. Typical mapping carried out by such typical software is given below (Figure 14-1).
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15.
Benchmarking of Power Plant Operation & Management
15.1
General
Re-organisation of the power industry has progressed and has put pressure on heat and power production cost with the import of electricity from neighboring regions possible. In this context, many power plants have taken up several mid-term programs of efficiency and competitiveness improvement (strategic cost management program). A competitive power generation might only be reached by cost cutting what means technically and cost efficient power and heat generation. In thermal power plants the following subjects are preconditions for this: •
low operation cost
•
low maintenance cost
•
high technical efficiency in plant operation
•
effective management organization
•
compliance with surrounding regulations.
Benchmarking
of
power
plant
involves
development
of
essential
technical
and
organizational elements for the long-term commercial sustainability of the power plant operation.
15.2
Basics of Benchmarking
The competitive energy market in EU demands that power generation companies must have a critical look on their business policy. "Benchmarking" provides a chance to compare a company, a plant or a production unit with another or a "Best Practice"-company, plant or unit, to find out its own ranking in a competitive market. The own position in the competitive market will be given by means of indicators, which will be defined at the beginning of the process.
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Measures for a better economical efficiency of the company / power plant / unit focused on, are to be derived from the results. For example "cost/kWinstalled" is such an indicator in the power sector (Figure 15-1). Figure 15-1: Finding out a position in a competitive market by Benchmarking
What is benchmarking? Why do we need benchmarking?
What?
Comparison of ........ .......... a process or a company with other competing processes or companies with specific indicators (cost, €/kWi in thermal and hydro power plants or WMO in hydro power plants)
Why?
Ranking............. .......... of your own company in the market
Conclusions and development of measures
15.3
Benchmarking of Thermal Power Plants
The total cost will be divided into different groups of cost (Figure 15-2) and then analyzed and compared with other, similar power plants. The greatest attention will turn on the total operating cost. Numerous measures to improve efficiency and production cost have to be elaborated, evaluated, compared and finally best options need to be introduced. This gives the D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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advantage to judge benchmark key indicators versus the background of practical operations. Figure 15-2: In thermal power plants the focus of the analysis is on cost of operation
Total cost €/kWh
Fuel cost €/kWh
Operation €/kWinstalled
Total operating cost €/kWinstalled
Maintenance €/kWinstalled
Capital cost €/kWinstalled
Other €/kWinstalled
Administrative cost €/kWinstalled
15.4
Focus of analysis
Benchmarking Methodology
It is useful to conduct at first an internal and secondly an international Benchmarking to compare these units and to show their ranking compared to the international market. After this analysis the experts can point out cost intensive areas of operation. Measures to realise a cost effective operation of the analyzed power plants will be elaborated in an initial stage and can be suggested to the plants. The benchmarking exercise consists of a pre-phase and additional three project phases (Figure 15-3).
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Output 1.1 Figure 15-3: Phases in a successful Benchmarking process
Development of concept to increase efficiency
Introduction to methodology and selection of subjects to benchmark
Pre-Phase
Data collection
Phase I
Determination of potential for efficiency increase
Phase II
Drawing up of measures and creation of scheme of implementation
Phase III
Implementation
Implementation
Phase IV
In Phase I an extensive and detailed data collection on the subjects to be considered will be performed. This data collection will build the essential basis for all following phases. In the following Phase II the technical and organizational performance will be compared in a way that the determination of potential for efficiency increase will be possible. Following this in a Phase III there will be the focus on drawing up a strategic concept to improve technical efficiency and establish a cost efficient operation. Phase IV encompasses the realization and the implementation of measures and is not part of this proposal.
Pre-Phase
Introduction to the methodology of benchmarking processes
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within the company. Therefore, a team representing top level and working level of Power plant should be created to work on this process. A steering committee is required to take decisions according to the timetable of the project. All parties need to get a general understanding of the process and will be introduced to the methodology of Benchmarking.
Phase I:
Comprehensive technical economical, administrative and organizational data
collection By means of an extensive and detailed data collection in this Phase I the basis for the comparison of technical and organizational performance as well as for the definition of goals and the development of measures in the following phases will be provided (Figure 15-4). Figure 15-4: Overview data collection
Data Data sheets sheets
Other Other(insurance, (insurance,etc.) etc.) Purchasing Purchasing//Materials Materialsmanagement management Organisation Organisation//Processes Processes
AA comprehensive comprehensive data data collection collection ……. ……. 1a. 1a. Fuel Fuel (TPP) (TPP) 1b. 1b. Scheduling Scheduling (HPP) (HPP) 2. 2. Operation Operation 3. 3. Maintenance Maintenance 4. 4. Administration Administration … … is is the the basis basis for for aa comparison comparison of of cost cost for for aa sucessful sucessful benchmarking benchmarking
Employees Employees Cost Cost Technical Technicaldata data Basic Basicdata datasite site
••installed installedcapacity capacity ••number of number ofunits units ••generation generation ••specific specific technical technical features features ••... ...
Reference year: Last year
Data collected and evaluated will include (e.g.): •
fuel supply in TPP
•
process organization (structure, cost, etc.)
•
management organization (hierarchical structure, cost, etc.)
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•
technical and economical data on power generation (operation and maintenance, overhauls, degree of automation, etc.)
•
administrative data (overhead, personnel, etc.).
For a basic year of investigation as well as from following years available data will be taken into account. Total operating cost will be divided into various cost components such as operation cost, maintenance cost and other cost (see chapter 15.3 and Figure 15-2). Maintenance cost themselves will be divided into cost for routine maintenance (cover cost for regular maintenance and other repair expenses) and cost for maintenance projects (cover cost for inspections and scheduled overhauls, cost for individual measures and cost for other measures). Depending on the maintenance cycle annual maintenance cost may vary more or less. It is important to determine a representative mean value for the basic year, preferably the running year. Concentrate on technical issues and consider their economic influence including the following topics: •
Heat and power production efficiency (production equipment efficiency)
•
Heat supply systems efficiency (efficiency of the heat supply infrastructure)
•
Fuel supply efficiency (fuel purchase and storage efficiency)
•
Material and technical supply efficiency (material and technical resources purchase and storage efficiency).
At the end of Phase I the data collected will be presented to the Client and, if required, additional information input from the Client will be discussed.
Phase II:
Determination of potential for efficiency increase
The methodology of Phase II for thermal power and heat generating plants is described below. The results where an efficiency increase seems to be successful and feasible in short term as well as in long-term measures will be presented to the Client at the end of Phase II.
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The data collected in Phase I will be evaluated and key performance indicators and sitespecific correction factors will be elaborated and defined. The site-specific correction factors will be discussed with the responsible power plant personnel. Correction factors are essential to compare power plants. They will be introduced to adjust location and type of a power plant. Site correction factors e.g. consider different levels of wages, different annual working hours or different cost of materials. Correction factors for technical differences will be determined in a multi-step elaboration. Important parameters of the power plant will be determined; by analysis and discussions with the local experts the correction factors will be set up. In addition to general technical differences, other peculiarities having influence on the power plant cost will be considered. Based on the data a comparable gap will be defined, including the international comparable gaps for both units. Results of the comparison will show the power plant’s / unit’s ranking with respect to the category it is operating in. This comparison will be made with international power stations. By comparison with the "Best-Practice" power plants / units savings potential for the power generation units under consideration will be determined and the data assessment of the current situation will allow the definition and suggestion of cost saving measures in Phase III. The collected but non-corrected data do not show differences in cost or efficiency against other power plants. Only the introduction of correction factors allows the demonstration of advantages or disadvantages of the power plant considered versus international power plants. In Figure 15-5 the potential for improvements worth striving for is outlined.
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Output 1.1 Figure 15-5: Evaluation of correction factors in thermal power plants Data comparison Data collection
Data correction Benchmark
Definition of goals
Development of measures
Power Plant 1
Realisation of measures
Power Plant 2 Fuel
Fuel
Operation Power generating costs
To compare power plants, corrective factors need to be applied to make adjustments for sites / power plants types.
Operation Power generating costs
Capital
Capital
Administration
Administration
Figure 15-6: The value of a benchmarking project is not the contest but performance improvement opportunities
disadvantage versus best practise PP
PP 1 non corrected data
advantages versus best practise PP
corrections
improvements worth striving for
PP 1 potential corrected data for improvements
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Phase III:
Drawing up of measures and creation of scheme of implementation
During Phase III first draft measures are drawn up and suggested in the process. The implementation
of
these
measures
will
be
schematically
described.
Technical,
organizational and economic measures to increase the efficiency and saving costs will be developed, suggested and discussed with the management of the power plant branch management and the company management. Points of start, where first measures could be introduced will be found out. The measures elaborated and the implementation scheme will be presented to the Client. After the specific cost reduction measures for the thermal power plants are identified and the required level of investigation for each measure is known, the Consultant will prepare a separate tender for the related services.
15.5
Project Organization
A successful co-operation between Consultant’s and plant's experts is a precondition to elaborate immediate measures, which will lead to comparatively quick results. It is required to establish one project team guided by a steering committee. Plant engineers will be the local engineering partners to the team. The responsible plant and administrative personnel will join the teams, each for the different topics (typical organization (Figure 15-7), and support the benchmarking team. By this the detailed knowledge on the thermal heat and power generating plants is going to be combined with external experience in efficient power plant operation in the liberalized energy market according to the state of the art. To ensure an overall evaluation concerning administrative, management and economic assets, experts will closely work together, exchange their information and discuss the analyses with their power plant's counterparts.
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Output 1.1 Figure 15-7: Typical project organization for a benchmarking process
Steering Steering Committee Committee Member Member of of the the Board Board Power Power Plant Plant Director Director Evonik Evonik Energy Energy Services Services
Project Project Director Director N. N. N. N. (Power (Power Plant) Plant) N. N. N. N. (Evonik (Evonik Energy Energy Services) Services)
Core Core Team Team Production Production
Core Core Team Team Maintenance Maintenance
Core Core Team Team Others Others
N. N. N. N. (Power (Power Plant) Plant) … …
N. N. N. N. (Power (Power Plant) Plant) … …
N. N. N. N. (Power (Power Plant) Plant) … …
N. N. N. N. (Evonik (Evonik Energy Energy Services) Services)
N. N. N. N. (Evonik (Evonik Energy Energy Services) Services)
N. N. N. N. (Evonik (Evonik Energy Energy Services) Services)
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16.
Energy Audit – Situation in the EU respectively Germany
16.1
Status
In the EU are a wide-spread set of directives (to be transposed into national law) targeting the energy sector. There are directives for: •
emission limits (large combustion directive)
•
emission trading
•
utilisation of water (water framework)
•
emission ceiling
•
co-generation of heat and power
•
use of renewables
•
efficiency of transport (vehicles)
•
efficiency of households
But there are no regulations for the efficiency of electric power generation. In the past in the EU we had discussions to implement regulations, but at the end the conclusion was that market-driven mechanism are more effective. This position was supported by the fact that the electric power generation in the EU is the most efficient worldwide. In the following one will explain why and how this impressive result has been achieved. As well as it will be shown how the efficiency is monitored. This offers the possibility to build a bridge for this experience referring the energy auditing procedure to the Indian situation. A simple key reason is: the more efficient a power plant works the most economic it is!
Electric Power Market This statement is outcome of a development lasting for several decades; i.e. nonliberalised and competitive markets. For the pre-competitive area the driving force was – at the end – high cost of the domestic primary resources and/or the lack of domestic primary resources, which have to be bought from elsewhere. Consequence of this experience was a well established culture in improving the technologies needed to achieve high efficiency figures. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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With the opening of the electricity market for competition this culture and state of the art of technology was an excellent basis for the challenges out of competition. The increasing concern about climate change and the necessity to improve efficiency and reduce emissions on one side and the explosion of fuel prices for fossil primary resources had enforced the pressure for further improvements.
Practice Based on the given constraints - presented above - the practical use and application respectively installed technologies will be described.
Philosophy The existing philosophy is determined by the competition driven constraint to be market feasible. Market feasibility means to do anything improving the competitiveness. The competitiveness is a function of •
well established customer relations in terms of prices and services,
•
well positioned power fleet consisting of
base, intermediate and peak load plants and of
balanced fuel portfolio
•
state of the art technology
•
skilled staff in mastering technology & market requirements as pre-requisite
In the following the major focus will be given to the technology sector respectively their solutions.
Technical Solutions The efficient operation is determined by an appropriate design of the plant and its components, realised quality and the corresponding monitoring tools. The key element for pursuing the efficiency of power plant operation is the instrumentation and control system (I&C). By means of the I&C system the staff is able to follow the timely behaviour of key figures defining the efficiency as the case may be the performance.
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The accuracy of the measurement devices does not reach the accuracy of the specific installations for the final approval tests, but it allows a trend analysis of selected operation plant parameters. State of the art plant process control systems are delivering the overall plant efficiency as well as the efficiency of systems and even components. Examples are the effectiveness of •
feed water pre-heating system indicators are the heat transfer factor, the terminal temperature difference and the temperature increase of each high-pressure pre-heater
•
heat transfer of the boiler tubes indicators are the heat transfer factors of each bundle significantly influenced by ash deposits to be removed by the soot blowers
•
air pre-heater indicators are the pressure loss and the leakage of the air pre-heater
•
condenser indicator is the heat transfer factor of the condenser
Specific systems are available supporting the process control system. The goal is to facilitate the complex optimisation process with often contrary influence factors. Based on the process control system the optimisation process will be guided ensuring both optimal and safe operation (see Figure 16-1). In addition to this the minimization of outages, shortening scheduled overhauls and increasing efficiency by detailed planed outages are very important from environmental point of view.
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Indo German Energy Programme Report Output 1.1 Figure 16-1: Performance monitoring of power stations
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Experience and Application IT-systems which provide the above mentioned monitoring functions are used in many German power plant units. The results of the technical and economical evaluation of the power plant are updated every 5 minutes and saved in a data historian. Thus, the trend of the performance of each unit can be monitored on any time scale. Hence plant components are evaluated online and planning data for condition based maintenance are provided. Furthermore optimum modes of operation from economic and ecological aspects are suggested, the impact of different, changing environmental conditions is evaluated and last but not least the unit's operation is optimized coming along with an efficiency enhancement. In addition to the efficient operation the role of the process control system is also the provide information concerning the life time of components and hints necessary for maintenance to be done. Figure 16-2 and Figure 16-3 give an overview the plant monitoring system is shown: •
terminal output (Figure 16-2: 151.5 MW)
•
unit efficiency (Figure 16-2: 42.28 %)
•
boiler efficiency (Figure 16-2: 94.52 %)
•
specific heat consumption (Figure 16-2: 2,184 kJ/kWh)
•
auxiliary consumption (Figure 16-2: 6.58 MW)
Losses are calculated in monetary value (here in DM) •
heating surface, economizer/reheater (Figure 16-2: 62 DM/h)
•
reheat spray flow (Figure 16-2: 19 DM/h)
•
leakage in economizer (Figure 16-2: 25 DM/h)
•
live steam parameter (Figure 16-2: 4 DM/h)
•
condenser pressure (Figure 16-2: 8 DM/h)
•
pre-heater (Figure 16-2: 10 DM/h)
•
current consumption (Figure 16-2: 0 DM/h)
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Output 1.1 Figure 16-2: Screenshot 1 of the plant monitoring system (Evonik power plant)
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Output 1.1 Figure 16-3: Screenshot 2 of the plant monitoring system (Evonik power plant)
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In the following Figure 16-4 to Figure 16-12 in more detail a lignite power station is described as an example. Figure 16-4: Unit overview Figure 16-5: Combustion freeboard including burners Figure 16-6: Soot blowing system Figure 16-7: Soot blowing system and boiler reforming data Figure 16-8: Boiler scheme Figure 16-9: Operation regime of soot blowing Figure 16-10:
Thermodynamic scheme
Figure 16-11:
Boiler air supply system, burner and overhead air
Figure 16-12:
Combustion Air Control
Conclusions The general conclusion is that in spite of the fact that there are no legal obligations the efficiency culture is part of any power plant operation. Basis is the plant design and process control system. An indirect indicator for energy auditing are the performance indicators for availability respectively unavailability. Finally one can quote that energy auditing is essential part of an efficient electric power generation in respecting the limitations of laws of nature and coping with the challenge of a competitive market.
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Indo German Energy Programme Report Output 1.1 Figure 16-4: Unit overview
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Indo German Energy Programme Report Output 1.1 Figure 16-5: Combustion freeboard including burners
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Indo German Energy Programme Report Output 1.1 Figure 16-6: Soot blowing system
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Indo German Energy Programme Report Output 1.1 Figure 16-7: Soot blowing system and boiler reforming data
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Indo German Energy Programme Report Output 1.1 Figure 16-8: Boiler scheme
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Indo German Energy Programme Report Output 1.1 Figure 16-9: Operation regime of soot blowing
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Indo German Energy Programme Report Output 1.1 Figure 16-10: Thermodynamic scheme
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Indo German Energy Programme Report Output 1.1 Figure 16-11: Boiler air supply system, burner and overhead air
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Indo German Energy Programme Report Output 1.1 Figure 16-12: Combustion Air Control
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Output 1.1
17. Overview on Regulations, Guidelines Efficiency/Plant Performance Best practice
System part
Indications
Source
Page
Remarks
items for the analysis
Fuel
Fuel analysis
DIN 51700
Analysis of solid fuels
DIN 51701-2
Carrying out the analysis
Volatile elements Hardgrove
Thermal
Index
efficiency
13. BImSchV
Sulphur
Water pollution
LCP-Directive,
Silicon
LCP-Directive,
13. BImSchV
13
DIN 51724-1
2 to 6
DIN 51724-2
2 to 5
Co-
LCP-Directive,
combustion &
13. BImSchV
refuse derived
8
Determination of sulphur
amount
Determination of sulphur in
the fuel
13
fuels Calcium Ash
Technology for
Primary
LCP-Directive,
avoiding
measurements
13. BImSchV
sulphur
for avoidance
emissions
Determination of the ash 109
content
Carbon
proportion Coal supply
VGB M 211e Use of lowsulphur fuels
Boiler
Steam boiler
Flow -through
Power plant coal feeding
LCP-Directive, 13. BImSchV
109
VGB R 450 L
10
boiler / drum
Guideline for feed water,
boiler (water
boiler water and steam quality
processing) Water / vapour
Interactions
VGB R 450 L
13 - 16
circulation Evaporator Combustion
VGB M 224
chamber Superheater Intermediate heating heating
surfaces Accumulator
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SiC - Melting chamber lining
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Best practice
System part
Indications
Source
Page
Remarks
items for the analysis Hot components Mills
VGB R 123 C/2.9e VGB M 213
Coal dust measurements with the pendular zero-
probe coal milling plants Separators
Temperature
VGB R 200
77
measurement
GW vapour deposition and disconnection is to be
behind
allowed
separator Coal dust
VGB R 108
Fire protection in the power
bunker
plant TRBS 2152
Assessment of the danger of explosion
Burner Deashing
VGB R 201e
Directive on and operation
Purification
VGB R 313e
Internal cleaning of
VGB M 221
waterpipe steam
of deashing plants
generators. Process-
engineering influences on the cleaning of heating surfaces and optimisation of use Combustion conduct
Firing
Combustion
modification
LCP-Directive, 13. BImSchV
97
VGB R 200
Dimensioning and operation of power plant firings
VGB TW 216
Primary measurements for the NOx reduction of dust firings for mineral coal
Reduction of
LCP-Directive,
excess air
13. BImSchV
Sorbens -
LCP-Directive,
injection
13. BImSchV
Sorbens -
LCP-Directive,
Injection for
13. BImSchV
140 " 125 to 127
dry flue gas
127 to 129
conduct Reduced air
LCP-Directive,
preheating
13. BImSchV
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Best practice
System part
Indications
Source
Page
Remarks
items for the analysis Fresh
air
ventilator
Maximum
KWS Training
pressure
book no. 8
104
increase Induced draft
KWS Training Ventilator
book no. 8
design
VGB R 102
104 Order of ventilators for thermal power plants
Pumps Air Preheater
(air flow rate) Heavy metals
LCP-Directive, 13. BImSchV Dust-avoiding
LCP-Directive,
techniques
13. BImSchV
Electrostatic
LCP-Directive,
Electrostatic
LCP-Directive,
Fabric filters
LCP-Directive,
(bag filters)
13. BImSchV
Centrifuge
LCP-Directive,
filter
wet separators
13. BImSchV 13. BImSchV
separator
13. BImSchV
Wet separator
LCP-Directive,
VGB R 103e
13. BImSchV
10 98 99 101 101 104 105 to108
Turbine
Types of
Condensing
Vapour purity/
construction
turbine/ back-
conditioning
pressure turbine
Directive on monitoring and protection of steam turbines
VGB R 105e
The thermal behaviour of steam turbines refer to IEC Technical Specification TS 61370 (page 12)
Turbine
VGB R 504e
Test of big forgings and pressure pieces
Turbine
VGB R 127
operation
VGB Directive on turbine drives
VGB M 101
Rec. on how to avoid damages at steam turbo units
VGB M 114
Efficiency changes at steam turbines
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Best practice
System part
Indications
Source
Page
Remarks
items for the analysis Fitting
VGB R 107
Order and design of fittings
tappings
in thermal power plants
Preheater Piping
VGB R 503e
Directive on internal pipings of the turbo unit
Connecting
VGB R 505e
Types of
VGB R 450 Le
elements Condenser
Directive on screws in
high-temperature areas Directive on the quality of
construction
feed water, boiler water and steam for copper materials VGB R 106e
Directive on condensators
and other heat exchangers, part A copper alloys
VGB R 113Le
Directive on condensators
and other heat exchangers, stainless steel
VGB R 114Le
Directive on condensators
and other heat exchangers, Ti material
Cleanability Flue gas
cleaning
Condensation system
DeNOx
VGB R 305
Directive on planning and
ordering of installations for the reduction of NOx emissions
E - filter
Emission of
LCP-Directive,
particulate
13. BImSchV
matter
VGB R 301
9 Planning and ordering of
installations for the reduction of dust emissions
Heavy metals
LCP-Directive,
NOx emission
LCP-Directive,
Wet scrubber
LCP-Directive,
13. BImSchV 13. BImSchV
13. BImSchV Types of
LCP-Directive,
absorbers
13. BImSchV
Sea water
LCP-Directive,
scrubber
13. BImSchV
10 11 111 117 119
Magnesium wet scrubber
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Best practice
System part
Indications
Source
Page
Remarks
items for the analysis Ammonia wet scrubber
121
Spray dry scrubber
121 to 124
Electrical
Volumetric
VGB R 123
and
flow
Collection of recommendations on the
control
measurements
control technology
technology
Pressure
measurements Temperature measurements Control
VGB R 170 BO-
Design standards for
technology
B6e
instrumentation and
VGB R170 A1e
Measures for the avoidance
control equipment and control of control technology failures Technical unit
VGB R 117
protection Auxiliary
VGB R161
Material for
VGB R 109
pressure-
d+e
power
Technical unit protection for thermal power plants Auxiliary power and
protection of auxiliary power in power plants
General
carrying devices
Availability
VGB Rv 808
Availability of thermal
Losses
DIN - EN
Determination of radiation
power plants 12952 - 15
losses
DIN - EN
General losses
12952 - 11
VGB R 123C Dangers
Losses in start-up and
shut-down processes
TRBS 2152,
Assessment of the danger
TRBS 2152-1,
of explosion
TRBS 2152-2 TRBS 2141,
Assessment of the danger
TRBS 2141-1
of steam and pressure
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18.
Example: Computerized Plant and Energy Management Systems at the Evonik Steag Voerde Power Plant
Evonik Steag Voerde Power Plant has total installed capacity of 2,120 MW. Hard coal is used as fuel. The total power generation is about 10 billion kWh/a The plant has adopted the latest computerized management systems for effective operation & maintenance of the power plants and improving the performance of the unit. The following computerized systems have been adopted •
Energy Management system
•
Plant management system.
Energy Management System The energy management system evaluates the existing on line measured data and recognizes the potential for optimization by assessing the processes and components. The system continuously assesses the plant operation, comparing it with the current calculated optimum, so that the unit can be run at maximum efficiency. The energy management system estimates the potential for optimization and even minimal reduction in operating efficiency is identified and pinpointed.
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The energy management system is based on a three-tiered concept – evaluation, Optimization and forecast for cost relevant power plant sections. All results are evaluated at cost so that the effects of different operating parameters on cost can be directly compared. •
Computation of ratios and key figures such as efficiencies, electric energy from cogeneration, start up cost etc.
•
Component evaluation (steam generator, steam water cycle, condenser, pumps, flue gas circuit etc)
•
Optimizing (soot blowing, gas turbine compressor washing etc)
•
Fore cast (unit efficiency, maximum unit output etc)
Plant Management System Integrated plant management system, makes all operating processes rational and transparent right from shift planning to component use. The plant management system helps the plant team to detect weak spots early and optimize operating procedures. In addition it gives up to date information with all organizational, technical & commercial details. Based on master data and timely operating data acquisition, the plant management system supports the plant team in the following areas of operation: •
Minimizing of the administrative effort invested in plant management
•
Efficient job scheduling and control along with performance recording and documentation
•
Cost optimized shift planning with integral payroll data acquisition
•
Optimizing and reporting of the use of operating supplies and the stocks of supplies
•
Daily cost status, availability data and official requirements compliance information
•
Assurance of compliance with processing and quality standards
•
Subject related control of information flow and authorizations
•
Dependable safety disconnection process with conflict check and switch in warning
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19.
Latest (state of the art) technologies and status
19.1
Technology Perspectives – Availability vs. State of the Art
The technical development is a permanent process and the key attitude is the requirement for patience and perseverance in order to accept the un-evitable errors, to sustain the motivation for searching in new solutions and convince the financing instances to spend money. With these general remarks in mind one can quote that there is always a gap between state of the art and the commercial available technology. One characteristic feature of a commercial available technology is the market viability, i.e. several suppliers offer a technology at competitive conditions. The aspects of local affects for the technologies are of minor relevance in a global world. As a conclusion it is to state clear that the 600°C technology is fully commercial available. There are several suppliers of the raw materials – forging, casting, etc., as well as there are several manufactures able to master the specific requirements of the austenitic materials. At the end there is enough experience driven by some front-runners in order to know what kind of difficulties can occur or preventive measures are reasonable. Parallel to the placing orders, erecting of plants and commissioning of new plants an intensive consolidation programme is launched. It's key purpose is to broaden the range of materials, to gain better understanding of the design specifics and to open the horizon for new ideas.
19.2
Atmospheric Fluidized Bed Firing System
The fluidized bed firing is a firing that takes place in a fluidized bed made up of sand, fuel reduced to small particles (fuel portion of about 2 %) and hot combustion air (primary air through the nozzle bottom). The fuel is kept hovering above the nozzle bed and fluidizes. The small fuel particles have a large surface enabling a thorough burnout. The strong eddying flow results in a most favorable impulse and heat exchange so that a constant temperature is kept up in the fluidized bed. The combustion temperature is determined by the fuel mass flow supplied. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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The temperature is adjusted such that the generation of detrimental gases (CO, NOx) is as low as possible. With fluidized bed firing it is possible to keep the nitrogen oxide emissions low as it allows to operate at a relatively low combustion temperature without temperature peaks. We distinguish between the stationary and the circulating fluidized bed: •
In case of a stationary fluidized bed the ash discharged from the combustion chamber is removed.
•
The circulating fluidized bed is designed with a cyclone downstream of the combustion chamber which serves to return the discharged sand with a certain portion of ash and unburned fuel back into the combustion chamber.
For fluidized bed firing in coal-fired power plants the coal is charged with lime to bind the sulphur contained in the coal. With today's state of technology a power enhancement to 1,000 MWth is feasible with circulating fluidized bed plants and this is currently being implemented in Poland. The principal field of application for atmospheric fluidized bed plants is considered to be the combined production of electric current and heat – i.e. combined heating and power plants. The limitation of the power capacity is of rather low importance here. In addition, this design permits to utilize a broad scope of fuels ranging from coal via biomass through to residual materials.
19.3
Pressurized Fluidized Bed Firing System
Similar to the development of the gas and steam turbine plants (combined cycle turbine facilities) fuelled with natural gas, in the 1950's there was a desire to implement also for power plants fuelled with hard coal such cogeneration power plants consisting of a gas turbine process and a steam turbine process to reach maximum plant efficiency levels. The first large-scale plants with a pressurized fluidized bed firing system were then commissioned in the 1980's. For these systems, the conventional combustion chamber of D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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a gas turbine plant was replaced by a combustion chamber fuelled with coal. As the combustion chamber needs to be operated under increased pressure (approximately 12 bar – 16 bar) to obtain a large efficiency, it became necessary to accommodate it in a cylindrical or spherical pressure vessel (diameter approx. 22 m for a projected 300 MW plant). Based on the pressurized fluidized bed firing system, various testing facilities and pilot plants were erected: •
Testing power plant Grimethorpe, Great Britain
•
Pilot power plant TIDD Ohio, USA
•
Pilot power plant Värtan, Stockholm, Sweden
•
Pilot power plant Escatron, Spain
•
Combined heating and power plant Stadtwerke (public utility company of) Cottbus, Germany
Efficiency The operating experience gained up to date has shown that the pressurized fluidized bed firing has a limited efficiency potential. Owing to the combustion chamber temperature being limited in the fluidized bed to 850 – 900°C, the upper process temperature determining the efficiency is restricted such that maximum plant efficiency values of a mere 45 % can be expected. In practical operation, it was possible to reach an efficiency of about 42 %. Apart from the limited efficiency potential, the experience gained in practical operation has particularly lead to the fact that pressurized fluidized bed firing became less important in modern power plant technology world-wide. Coal supply In a pressurized steam generator the fuel needs to be fed in either via a lockage system or in the form of a coal/water suspension. Drawbacks: •
Considerable wear at the lock fittings has continually entailed system malfunctions.
•
To feed the coal without difficulty it had to be dried to a water content of
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< 2 % involving a high energetic expenditure. •
To prevent explosions in the lock chambers, the locking process had to be laboriously carried out under an inert gas atmosphere.
•
When supplied as a coal/water suspension the slurry pumps used for the process had an inadequate service life.
De-ashing system The ash produced in the coal firing process needs to be discharged from a pressurised pressure vessel via a lockage system. Drawbacks: •
Considerable wear in the pneumatically operated conveying lines
•
Frequent failures of the lock fittings at an ash temperature of 850 °C
Steam generator To provide a combined process, the steam generator is accommodated in a pressure vessel. Drawbacks: •
Poor accessibility for maintenance work
•
Restricted possibility to timely detect malfunctions in the steam generator area.
Purification of the flue gas and gas turbine The flue gases are first cleaned by passing through a cyclone cascade and subsequently further cleaned by means of a ceramic hot gas filter, before they are fed into the gas turbine. Drawbacks: •
Fractures of the ceramic filter cartridges resulted in frequent plant standstills.
•
High residual dust content led to a destruction of the gas turbine blading.
•
Exhaust gases from the gas turbine require another purification downstream of the gas turbine in order to observe the currently applicable dust emission
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levels.
19.4
Gasification of Coal (IGCC)
Another power plant process for the use of coal in combined gas and steam turbine processes is provided by the gasification of coal and the subsequent combustion of the produced synthetic coal gas in a downstream gas and steam turbine plant (IGCC proc-ess or Integrated Gasification Combined Cycle). In the gasifier proper, which is operated at a high gasside pressure of 40 bar, the coal is mostly converted with pure oxygen to become a synthesis gas predominantly consisting of hydrogen and carbon monoxide. The carbon monoxide portion is converted into carbon dioxide and additional hydrogen by adding water steam in a so-called shift reaction. The hydrogen can then be used for power generation in the gas turbine plant of the combined power plant downstream of the coal gasification. In this process the hot flue gases of the gas turbine are fed into the integrated water/steam circulation via a heat-recovery steam generator. Compared to other power plant designs the IGCC technology has the advantage that the carbon dioxide present in the synthesis gas can favorably be precipitated from the process at relatively high pressure, for instance by a Rectisol flue-gas purification process. In the long run, after developing underground storage deposits, this could lead to an implementation of a CO2-poor power plant technology on a coal basis. Furthermore, it is possible to produce synthetic fuels and chemicals from the synthesis gas, which provides new attractive application options for this process in the long term. Since the 1980s, several pilot plants with entrained-phase gasification and fluidized bed gasification have been operated for testing purposes. Today, various processes are offered by Shell, UHDE, General Electric and Siemens. The following pilot plants have since been erected for power generation:
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•
Pilot plant Cool Water, USA, operation 1984 – 1998
•
Pilot plant Buggenum, NL, currently operating
•
Pilot plant Puertollanno, SP, currently operating
Although the IGCC technology has a high development potential, an economically reasonable application in large-scale plants could not be realised to date. The service experiences available today show that there is a continued need for development in the fields of the gas turbine, the hot-gas purification as well as the coal supply and the slag discharge. If ultimately a reliable plant operation with a high availability and a high efficiency is to be implemented, it will be necessary to further optimise the plant components currently being developed and to have them tested in pilot plants. In Germany a first pilot plant is envisaged to be commissioned in 2014. After several years of testing operation a reliable commercial plant engineering will then possibly be available around the year 2020.
19.5
Turbulent Pulverised-Coal Burner
In above comparison of the pulverised coal firing with other firing types and coal conversion methods, it has been demonstrated that none of the techniques that are comparable to pulverised coal firing is able to exceed a thermal power of 1,000 MW. Accordingly, the thermal power required ranging far above 2,000 MW can be generated only when using a pulverised coal firing process. Pulverised coal preparation In the power generation industry, fan mills have become widely accepted for the preparation of brown coal and bowl mills have established themselves for the preparation of hard coal. Essentially, the required preparation comprises the crushing (surface-area amplification), drying and screening. The screen sorting of pulverised coal formerly performed with static separators is increasingly since the 1990's being effected using speed-controlled dynamic separators as shown in Figure 19-1. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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Output 1.1 Figure 19-1: Bowl mill with dynamic separator
Burner description In an almost 100-year development of the pulverized coal burners the so-called jet and swirl stage burners (DS burners) have established themselves; they differ only marginally in terms of burnout and emissions. The swirl stage burners intended of the power plant are arranged at two opposing combustion chamber walls (in a height-offset arrangement, 3 or 2 levels). Each burner consists of a core air tube surrounded by several concentric tubes (refer to Figure 19-2). accommodated in the core air tube there is the ignition and supporting burner (designed as an oil firing), which – only for start-up and supporting load operation is driven forward to the operating position near the combustion chamber wall; usually the ignition and supporting burner is kept in a retracted position in order to have it as little as possible exposed to the heat radiated in the combustion chamber so that the core air tube will require relatively few cooling air. Figure 19-2: Pulverised coal burner (with out ignition and supporting burner)
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The first concentric annular space surrounding the core air tube serves for conveying the pulverized coal / air mixture and is also designated as primary air. For a stable, complete and environmentally friendly combustion, the pulverized coal is to flow into the combustion chamber most uniformly distributed across the burner ring cross section. This is supported by a symmetrical line arrangement, a sufficient primary air velocity and a ring gear at the outer pulverized-coal ring main. The ring gear serves not only to stabilize the flame but also to disintegrate the chunks of pulverized coal. To have all chunks get reached and contacted by the ring gear, the annular flow of pulverized coal around the ring gear is given a slight angular momentum by swirling blades.
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The burner ring cross sections serve for a staged allocation of the combustion air and they can provide their through-flowing air not only with a variable impulse (velocity and volume) but also with different swirl stages. The different swirl stages can be generated by adjustable and fixed swirl blades and supplement the required flame stability, if the stability produced by the ring gear is not sufficient. The flame stability is essentially determined by the portion of volatiles in the coal and the comminution, the fine grain portion of the pulverised coal. The portion of unburned carbon in the electrostatic precipitator ash is required to range below 5%, so that the ash can be further utilised in the cement industry. This is primarily reached by a low coarse grain portion in the pulverised coal, which in turn results from the high grinding performance and a strict grain-size screening in the separator. Turbulent burner aspects: With the NOx primary measures (see BAT measures) harmonised accordingly, it is possible for today's use of "steamcoal" from South Africa or Colombia to reach nitrogen oxide concentrations ranging between 400 mg/Nm³ and 500 mg/Nm³ in the flue gas at the discharge end of the radiation chamber (in front of the bulkhead). Here, the excess air may fluctuate around the Lambda value 1.15 and the unburned matter in the electrostatic precipitator ash can be kept well below 5 % when run at the "optimum operation point". We have explained and commented on the NOx primary measures relating to the BAT measures demonstrating that these requirements are fulfilled for the swirl stage burners. Consequently, today's best available technology is the pulverized coal technology.
19.6
Supercritical Technology
Supercritical (SC) and ultra-supercritical (USC) power plants operate at higher temperatures and greater steam pressures than conventional systems. They require less coal per megawatt-hour, leading to lower emissions per megawatt (including carbon dioxide and mercury), and lower fuel costs per megawatt, leading to higher efficiency and lower fuel costs.
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19.7
Six Sigma Concept
Six Sigma is a powerful data driven, customer focused management methodology that delivers validated improvements in profitability and productivity. Six Sigma implementation will guide organization to: •
improve Customer Satisfaction
•
Increase Profitability
•
Increase Productivity
In most companies today, the cost of poor quality represents 20 % to 30 % of total revenues. The Six Sigma approach implements the proven methodologies for minimizing these costs while reaching world-class quality levels by focusing on breakthrough performance (improvements of 50% or more). For more details on technological perspectives, please refer the following Annexures XIII to XX. Annexure XIII
IGCC technology
Annexure XIV
Supercritical and ultra super critical technology
Annexure XV
CFBC technology
Annexure XVI
Six sigma process
Annexure XVII
PFBC technology
Annexure XVIII
Advanced Technologies of Preventive Maintenance for Thermal Power Plants-write up by Hitachi
Annexure XIX
Oxyfuel technology for fossil fuel-fired power plants – Dresden University of Technology, Germany
Annexure XX
Results of oxy-fuel combustion for power plants- Dresden University of Technology, Germany
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20.
Operating Efficiency of EU Power Plants and Efforts initiated for Improvement
The efficiency of both electricity, and combined electricity and heat production from conventional thermal power plants improved steadily between 1990 and 2004. This was due to the closure of old inefficient plants, improvements in existing technologies and the installation of new, more efficient technologies, often combined with a switch from coal power plants to more efficient combined cycle gas-turbines. This trend is expected to continue in the future. However, the rapid growth in fossil-fuel based electricity production outweighs some of the environmental benefits of the efficiency improvements.
20.1
Rationale
The majority of thermal generation is produced using fossil fuels with associated environmental impacts such as greenhouse gas emissions, but can also include biomass, wastes and geothermal. Whilst the level of environmental impact depends upon factors such as the particular type of fuel and the extent to which abatement technologies are used, all else being equal, the greater the efficiency the lower the environmental impact for each unit of electricity produced. Annexure XXI shows the actual efficiency of thermal power plants in Europe, efficiency improvement over a period of time (paper published by European Environmental Agency) and corrective actions taken for improvement.
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21.
Best Practices Applicable to Indian Scenario
The following best practices which can be applicable are discussed in this section:
21.1
•
Online monitoring system
•
Statistical process control for fault detection
•
Maintenance management system
•
Pooling of inventories
•
Benchmarking of component efficiencies
•
Training including simulator training
Online monitoring System
This system is now gaining wide popularity and being used for all new power plants and also being introduced during retrofit of existing systems. The details of this system is given in annexure XXII.
21.2
Statistical Process Control Process Detection
Statistical Process Control (SPC) is an effective method of monitoring a process through the use of control charts. Control charts enable the use of objective criteria for distinguishing background variation from events of significance based on statistical techniques. Much of its power lies in the ability to monitor both process centre and its variation about that centre. The details are described in annexure XXIII.
21.3
Simulator Training on Power Plant Operation
Simulator training is the best option now available to power plants, which gives the feeling of operating a real Power Plant without incurring any generation loss or damaging any plant equipments. Simulator includes advanced training tools and features, which are as important as the D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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simulator itself in successfully achieving training goals. By integrating these tools into the simulators, which delivers not only training simulators but comprehensive training "systems". As a result, operator training becomes significantly more productive, and the need for intensive instructor involvement is minimized. The detailed write up on the simulator is given in annexure XXIV.
21.4
Maintenance Management Systems
The Maintenance Management Systems is a part of Integral Plant Management aided by sophisticated software. These systems are very popular in Europe and have significant potential of applications in developing countries. The details of such system are given in annexure XXV.
21.5
Benchmarking Practices
The benchmarking practices are described in chapter 15.
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22.
Miscellaneous
The report provides the brief write up on the following •
Monitoring and controlling of power plants (refer to annexure XXVI)
•
Maintenance practices (refer to annexure XXVII)
•
Sizing criteria of thermal power plants (refer to annexure XXVIII)
•
Stores inventory and procurement systems (refer to annexure XXIX)
•
Key operating parameters of power station (refer to chapter 11)
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Power Plant Performance Reporting and Improvement under the Provision of the Indian Energy Conservation Act
Output 1.1 Best practice performance monitoring, analysis of performance procedures, software and analytical tools, measuring instrumentation, guidelines or best practice manuals and newest trends
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Table of Contents 1.
General.................................................................................................. 14
1.1
Survey 'best practise' with basic Definition of Efficiency Indicators ................... 15
1.2
Analysis including Tools for Efficiency Indicators.............................................. 15
1.3
Instrumentation on Efficiency Indicators ........................................................... 16
1.4
Guidelines for basic Definition of Efficiency Indicators...................................... 16
1.5
Energy Audit ..................................................................................................... 16
1.6
Performance/ Benchmarking Analysis ............................................................... 16
1.7
Strategic Outlook (newest Trends & Research) .................................................. 17
2.
Power Scenario in Europe....................................................................... 18
2.1
Development of European & Global Electricity Demand..................................... 18
2.2
Availability, coverage and import dependency of Energy Sources ..................... 19
2.3
Primary Energy Saving through efficient use of Electricity ................................. 20
2.4
Power Plant portfolio in EU................................................................................ 21
2.5
Power Plant projects in Europe .......................................................................... 21
2.6
Pros & Cons of relevant Energy Generation Options .......................................... 23
2.7
Requirement of efficient coal and gas Power Plants .......................................... 25
3.
Directives Applicable to Large Combustion Plants.................................. 27
3.1
Legal basis in the EU ......................................................................................... 27
3.2
Underlying information ..................................................................................... 27
3.3
Document organisation..................................................................................... 28
3.4
The European Energy Industry........................................................................... 28
3.5
Applied technologies ........................................................................................ 28
3.6
Ecological issues ............................................................................................... 29
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3.7
Conditions ........................................................................................................ 29
3.8
Unloading, storage and transport of fuels and additives ................................... 30
3.9
Pre-treatment of fuel ........................................................................................ 32
3.10
Fine dust emissions .......................................................................................... 33
3.11
Heavy metals..................................................................................................... 34
3.12
SO2 emissions................................................................................................... 35
3.13
NOx emissions................................................................................................... 36
4.
Best Available Techniques to increase Efficiency and reduce Emissions.. 39
5.
State of the Art -Reference Power Plant (Source VGB)............................. 40
5.1
Brief Overview ................................................................................................... 40
5.2
Details of the Study ........................................................................................... 41
5.3
Innovations ....................................................................................................... 41
5.4
Layout Planning................................................................................................. 42
5.5
Thermodynamic Design .................................................................................... 42
5.6
Steam Turbine Plant (Turbine, Generator) ......................................................... 44
5.7
High-Pressure Turbine section.......................................................................... 44
5.8
Intermediate-Pressure Turbine section ............................................................. 45
5.9
Low-Pressure Turbine section........................................................................... 46
5.10
Generator Plant ................................................................................................. 47
5.11
Boilers ............................................................................................................... 48
5.12
Water and Steam Cycle ...................................................................................... 50
5.13
Cooling Water Systems...................................................................................... 51
5.14
Technological Options ...................................................................................... 52
5.15
Summary ........................................................................................................... 55
6.
Role of 700°C Technology for the Carbon-free Power Supply ................. 61
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6.1
Introduction and Background ............................................................................ 61
6.2
Status 700°C Technology .................................................................................. 62
6.3
Current and Coming Activities of the 700°C Technology ................................... 66
6.4
Perspectives of the 700°C Technology............................................................... 69
6.5
Regulatory and Political Framework .................................................................. 70
7.
Road Map to High Efficiency Power Plant................................................ 72
8.
Technology Platform for Zero Emission Power Plants by 2020................ 73
9.
Definition of Efficiency Parameters - Basics ........................................... 74
9.1
Efficiency........................................................................................................... 74
9.2
Losses of Efficiency in Combustion Plants......................................................... 75
9.3
Generic Technical Measures to improve Large Combustion Plant's Efficiency.... 76
9.3.1
Combustion ...................................................................................................... 76
9.3.2
Unburned Carbon in Ash................................................................................... 77
9.3.3
Air Excess ......................................................................................................... 77
9.3.4
Steam ................................................................................................................ 77
9.3.5
Flue-Gas Temperature ...................................................................................... 78
9.3.6
Vacuum in the Condenser ................................................................................. 78
9.3.7
Variable Pressure and fixed Pressure Operation ................................................ 78
9.3.8
Condensate and Feed-Water Preheating ........................................................... 79
10.
Energy Balance ...................................................................................... 80
10.1
Efficiency of German Power Plants..................................................................... 81
10.2
Efficiency Degradation ...................................................................................... 82
10.3
Energy Balance of a Coal-Fired Power Plant Unit ............................................... 82
10.4
Operating efficiency in European Power Plants.................................................. 84
10.5
Operating Efficiency of typical Indian Power Plants compared to German Power
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Plants ................................................................................................................ 87 10.6
Comparison of published efficiencies ............................................................... 88
11.
Key parameters and basis for measurements ......................................... 91
11.1
Key operating parameters ................................................................................. 91
11.2
Fuel Parameter .................................................................................................. 92
11.3
Air & Flue Gas Parameters ................................................................................. 93
11.4
Data required .................................................................................................... 93
12.
Official Statistics for Efficiency Indicator and Plant Reliability ................. 95
12.1
Reports on Analysis and Tools for Efficiency Indicators .................................... 95
12.2
Excerpts from Eurostat-Document.................................................................... 96
13.
Performance Indicators & Monitoring ..................................................... 97
13.1
Introduction ...................................................................................................... 97
14.
Software and Analytical Tools for Efficiency and Plant Reliability –Online and Offline ................................................................................................. 102
14.1
Introduction .................................................................................................... 102
14.2
Software Analytical Tools / Modules ............................................................... 103
14.3
Data Collection for the Performance Monitoring ............................................. 103
14.4
Analysis for Performance Monitoring .............................................................. 104
14.5
K I S S Y........................................................................................................... 105
14.6
Systems for Optimized Operation ................................................................... 107
14.7
Lifetime Monitoring System............................................................................. 114
14.8
Data Management System ............................................................................... 116
14.9
Thermodynamic Cycle Calculation Program – Offline Tool .............................. 117
15.
Benchmarking of Power Plant Operation & Management ...................... 121
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15.1
General ........................................................................................................... 121
15.2
Basics of Benchmarking .................................................................................. 121
15.3
Benchmarking of Thermal Power Plants .......................................................... 122
15.4
Benchmarking Methodology............................................................................ 123
15.5
Project Organization ....................................................................................... 129
16.
Energy Audit – Situation in the EU respectively Germany ...................... 131
16.1
Status.............................................................................................................. 131
17.
Overview on Regulations, Guidelines Efficiency/Plant Performance ...... 148
18.
Example: Computerized Plant and Energy Management Systems at the Evonik Steag Voerde Power Plant ......................................................... 153
19.
Latest (state of the art) technologies and status................................... 155
19.1
Technology Perspectives – Availability vs. State of the Art .............................. 155
19.2
Atmospheric Fluidized Bed Firing System........................................................ 155
19.3
Pressurized Fluidized Bed Firing System ......................................................... 156
19.4
Gasification of Coal (IGCC) .............................................................................. 159
19.5
Turbulent Pulverised-Coal Burner ................................................................... 160
19.6
Supercritical Technology ................................................................................. 163
19.7
Six Sigma Concept .......................................................................................... 164
20.
Operating Efficiency of EU Power Plants and Efforts initiated for Improvement ....................................................................................... 165
20.1
Rationale ......................................................................................................... 165
21.
Best Practices Applicable to Indian Scenario......................................... 166
21.1
Online monitoring System............................................................................... 166
21.2
Statistical Process Control Process Detection .................................................. 166
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21.3
Simulator Training on Power Plant Operation .................................................. 166
21.4
Maintenance Management Systems ................................................................. 167
21.5
Benchmarking Practices .................................................................................. 167
22.
Miscellaneous ...................................................................................... 168
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Abbreviations an
Analysis moisture
BAT
Best Available Technique
BDEW
Verband der Deutschen Energie-, Gas-, und Wasserwirtschaft
CCS
Carbon capture and storage
CFBF
Circulating fluidised bed firing system
dai
Dry adsorbent injection (flue gas desulphurisation)
DIN
Deutsche Industrienorm (German DIN Standard)
ESS
Electrostatic separator
EU
European Union
FBF
Fluidised bed firing
FF
Fibrous filter
FGD
Flue gas desulphurisation
GCV
Gross caloric value
hd
Half-dry (flue gas desulphurisation)
HHV
Higher heat value
HP
High pressure
kWh
Kilo Watt hour
LCP
Directive on Large Combustion Plants
lftraf
Air-dry and ash-free
LHV
Lower heat value
LP
Low pressure
MP
Medium pressure
NCV
Net caloric value
PFBF
Pressure fluidised bed firing system
Pm
Primary measures reducing the NOx
raw
Raw
SCR
Selective catalytic NOx reduction
SF
Dust combustion
SFBF
Stationary fluidised bed firing system
SNCR
Selective non-catalytic NOx reduction
TWh
Tera watt-hours
VDI
Vereinigung der deutschen Industrie (Association of German Engineers,
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www.vdi.de) VGB
European Association for Generation of Heat and Power, www.vgb.org)
waf
Water and ash-free
wf
Water-free
wmf
Water and mineral-compound free
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Terms and Definitions Dimension
e
Proportional auxiliary consumption
-
f Ho
Specific fuel consumption
kg/kWh
Upper heating value
kJ/kg
Lower heating value
kJ/kg
Time availability
h
Energy avalability
-
Mass flow of the fuel
kg/s, kg/h
Mass flow of the steam
kg/s, kg/h
Time utilisation
-
Energy utilisation
-
Net generator output
kW
Generator capacity
kW
Gross generator output
kW
Nominal capacity
MWel
High-voltage side net generator output
kW
Electrical auxiliary consumption
kW
Specific net heat consumption
kJ/kWh, kJ/kWs
Average fuel heat
kg/s, kg/h, kg/month
Hu kt
kW &f m &s m
nt
nw Pe
Pgen
Pi
PN Pnet
Pown qe Qf
Q FW Q nRH Q RH
Q SG Q SS se
sn tB
Feed water heat capacity supplied to the kg/s boiler Heat quantity without reheating supplied to kg/s the boiler Reheated heat quantity supplied to the kg/s machine Useful thermal quantity input into the kg/s process Superheated steam heat quantity input into kg/s the machine Number of successful start-ups
-
Number of unsuccessful start-ups
-
Operating time
h
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tN tv
WB
WN Wv z & Q heat
η ηbe η cl η el η fu η th η tr ηtot
Dimension Reference period
h
Available time
h
Energy generated
MWh
Nominal energy
MWh
Unavailable energy
MWH
Start-up reliability
-
Useful thermal heat
kJ/kg
Efficiency
-
Boiler efficiency
-
Losses of thermodynamic cycle
-
Electrical efficiency
-
Degree of fuel use
-
Thermal efficiency of the turbine
-
Efficiency of machine transformer
-
Total efficiency
-
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List of Annexures Annexure I
LCP Directive 2001 /80/ EC
Annexure II
13. BImSchV –Ordinance of implementation of Federal immission control act (English version)
Annexure III
Best Available Techniques
Annexure IV
State of the Art Reference Power Plant incl. its appendices I to VIII
Annexure V
The Evonik Steag Road to the high efficiency power plant
Annexure VIa
Roadmap for low carbon power supply ETP ZEP SRA and SDD study
Annexure VIb
Roadmap for low carbon power supply ETP ZEP SRA and Strategic Research Agenda
Annexure VII
Definition of Efficiency parameters
Annexure VIII
The complexity of thermal power plant efficiencies reporting in India and Germany” (By Dr. Kaupp, GTZ) Best available techniques to increase efficiency and reduce emissions
Annexure IX
Basis for measurements and parameters to be monitored
Annexure X
Analysis and tools for efficiency indicator
Annexure XI
Excerpts from Eurostat Document
Annexure XII
KISSY instructions & Excerpts from performance report
Annexure XIII
IGCC technology
Annexure XIV
Supercritical and ultra super critical technology
Annexure XV
CFBC technology
Annexure XVI
Six sigma process
Annexure XVII
PFBC technology
Annexure XVIII
Advanced Technologies of Preventive Maintenance for Thermal Power Plants-write up by Hitachi
Annexure XIX
Oxyfuel technology for fossil fuel-fired power plants – Dresden University of Technology, Germany
Annexure XX
Results of oxy-fuel combustion for power plants- Dresden University of Technology, Germany
Annexure XXI
Actual efficiency of thermal power plants in Europe, efficiency improvement over a period of time
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Annexure XXII
On line Monitoring System
Annexure XXIII
Statistical Process Control – Fault Detection
Annexure XXIV
Simulator Training
Annexure XXV
Maintenance Management Systems
Annexure XXVI
Monitoring and Controlling of power plants
Annexure XXVII
Maintenance Practices
Annexure XXVIII
Design Criteria of Thermal Power Plants
Annexure XXIX
Stores Inventory and Procurement System
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1.
General
A detailed survey on best practice power plant performance monitoring and was undertaken primarily in Germany/Europe by VGB and EESG.
After the survey detailed
report is prepared which covers the following outputs: •
survey 'best practise power plant performance monitoring in Germany/ Europe' with basic definition of efficiency indicators including samples of reporting
•
basic definition of efficiency indicators
•
software and analytical tools including tools for efficiency indicators used online and offline
•
instrumentation on efficiency indicators
•
guidelines/best practice manuals including VGB
•
energy auditing practise
•
analysis of performance procedure
•
strategic outlook (newest trends & research)
With a view the cover the above activities, the report is structured in to two parts: PART I: The initial part of the report gives an overall report about the electric power market in Europe including a compilation of the power plant projects in Europe. Further a description of the state of the art for electric power technologies as well as the perspective for future developments and the legal prescription for the emission limits according to the EU regulations is given. The intention of this general introduction is to give a better understanding to the specific situation in Europe and Germany in particular. •
power scenario in Europe
•
directives in the EU applicable to large combustion plants
•
best available techniques for large combustion plants
•
best practices to increase efficiency and reduce the emissions
•
state of the art – Reference power plant
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•
new trends – Role of 700 °C technology
•
future perspectives – Carbon Capture & Storage
PART II The later part of the report describes the best practise power plant performance monitoring in Germany/Europe. •
efficiency parameters definitions
•
energy balance
•
basics for the measurements and parameters
•
overview of regulations and guidelines for efficiency and plant performance
•
performance indicators and monitoring of power plants
•
software and analytical tools for efficiency indicators and plant optimisation – Online & Offline
1.1
•
benchmarking in thermal power plants as part of performance indicator
•
energy Audit
•
other relevant papers and reports
Survey 'best practise' with basic Definition of Efficiency Indicators
This document summarizes the technical and physical basis for plant performance indicators - oriented on the indicators needed and the necessary measurement devices. The report covers the definitions of the plant technical indicators as well as the correlated physical measurement units. 1.2
Analysis including Tools for Efficiency Indicators
Based on the selected and described indicators samples for standard reports used in the EU are given. These official reports are published by national authorities as well as industrial organisations like the VGB. The key tool is the control system on the plant process consisting of a measurement device, software transferring the physical unit into a plant indicator and an analysis tool in D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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order to be able to react
1.3
Instrumentation on Efficiency Indicators
The plant measurement system is part of control & instrumentation system; the plant process control system is also part of the above-mentioned system.
1.4
Guidelines for basic Definition of Efficiency Indicators
A distinction is drawn between legal and industrial regulations in the EU. Concerning the industrial regulations the VDI-guidelines are irrelevant for the report on hand; their main focus is on the design area. The main focus of the VGB-guidelines is on the operation area which has to be considered in this report.
1.5
Energy Audit
In the EU are a wide-spread set of directives (to be transposed into national law) targeting the energy sector. There are no regulations for the efficiency of electric power generation. In the past in the EU we had discussions to implement regulations, but at the end the conclusion was that market-driven mechanism are more effective. This position was supported by the fact that the electric power generation in the EU is the most efficient worldwide.
1.6
Performance/ Benchmarking Analysis
Benchmarking
of
power
plant
involves
development
of
essential
technical
and
organizational elements for the long-term commercial sustainability of the power plant operation.
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1.7
Strategic Outlook (newest Trends & Research)
The state of the art in the EU is a consistent system covering the whole chain of measurement, algorithm and analysis tools, available by all the suppliers. Prerequisite for the successful use of these instruments is to raise the awareness of the staff in applying these tools. Research work is mainly concentrating on a closer intercommunication of the technical tools with the business tools like SAP.
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PART I 2. 2.1
Power Scenario in Europe Development of European & Global Electricity Demand
(Source:
VGB
Power
Tech
–Facts
and
Figures
–Electricity
generation
2007,
http://www.vgb.org/en/data_powergeneration.html) The global population is increasing by 78 million people per year. Consequently, the population has doubled during the last five decades. At present, approximately one quarter of the global population of 6.5 billion do not have access to electricity. As a result, electricity consumption is growing faster than any other form of energy. It is expected that present global electricity consumption of 16,595 TWh is expected to double to roughly 30,673 TWh by the year 2030. One-fifth of the electricity generated globally – roughly 3,300 TWh – is required in the European Union (EU). A 30 % rise in demand is expected by 2030. Experts estimate that fossil fuels will continue to cover most of the extra demand. Fossil fuels will still account for roughly 70 % of electricity generated worldwide in 2030. About 60 % of electricity generated in the EU will come from fossil fuels by that time. Renewable energy sources will play increased role in the global primary energy consumption structure. Likewise, nuclear power will maintain an important position in global electricity generation and will even grow in some countries. Expected growth in electricity generation in EU by the year 2030 is 30 % (ie expected requirement is 4,300x109 kWh). While worldwide growth in electricity generation by the year 2030 is 85 % (i.e, expected requirement is 31,673 x 109 kWh)
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2.2
Availability, coverage and import dependency of Energy Sources
Existing primary energy reserves and resources, after including renewable energy sources, are adequate in terms of fossil fuels and uranium around the world. Hard coal and Lignite as well as uranium are the most widespread. However, energy sources have an uneven geographical distribution, which means that some countries and regions, including the European Union, are becoming increasingly dependent on imports. The EU’s fossil fuel reserves amount to approximately by 75,000 million tonnes of coal equivalent, accounting for only 5% of the known reserves worldwide, and consist mainly of lignite and hard coal. The natural gas and oil reserves amount to approximately 5,000 million tonnes of coal equivalent. Europe’s dependency on imported coal will grow from approximately by 30 % today to more than 60% by the year 2030. An import dependency of 81 % is expected for natural gas and of as much as 88 % for oil. Overall, the share of imported energy will increase from approximately from 50% today to roughly 70% by 2030. The causes of this are the nuclear phase-out chosen by some countries, along with the decreasing of cost-effectively exploitable European energy reserves. Only lignite will still be extractable from open cast mines at competitive costs in some countries in the long term. Figure 2-1 gives the development of dependence of imports of EU from 1990 to 2030. Figure 2-1:
Dependence of Imports of EU
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1990
100 90
81
80
Perc entage
86 88 75
66
70 60
2010
2020
2030
81
62
61
50
50
48 50
45 47
67
53
37
40
30
30 20
77
81
2000
18
10 0
2.3
Solid fuels
Oil
Natural gas
Total
Primary Energy Saving through efficient use of Electricity
The link between growth in gross domestic product and primary energy consumption has become weaker in many developed nations in the last few years, due to increased application of electricity facilitating many rationalisation processes. On the one hand, this development reflects the trend towards a service based society; on the other hand, the progress in energy production and its use, for example more efficient power plants, tailored energy application through electronic control or even heat pumps, is playing an important role. The expected use of electric vehicles in the future may reinforce this trend even more. Saving primary energy will therefore require more electricity. There is a risk that forced electricity savings will impair the balance of primary energy and emission cuts unnecessarily.
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2.4
Power Plant portfolio in EU
Total installed capacity of power plants in EU is 752,060 MW, which includes 27 countries. Of which Germany accounts for 18 % of the total EU. Figure 2-2 shows a break up of power plants' installed capacity in the EU.
Power plant portfolio in EU
2.5
16595
16352
13645
13320
12623
Finland
Belgium
Greece
Portugal
Denmark
37435
16997 Romania
Others
17412 CR
9555
19013 Austria
Bulgaria
21544
Spain
UK
Italy
France
0 Germany
MW
20000
Nederlands
32077 Poland
40000
33212
60000
Sweden
80000
75953
100000
81800
86762
120000
Power Plant Portfolio in EU (2005)- Total 752060 MW 115500
140000
132265
Figure 2-2:
Power Plant projects in Europe
The replacement demand for old power plants and the increase in electricity consumption in Europe have led many utilities and other investors to make plans for new projects. In
addition, taking into account also the CO2 emission trading and a worldwide increase in energy demand, coal, natural gas and nuclear power will continue to be the most important primary energy sources for electricity generation. Currently, around 67,000 MW of new build projects based on natural gas have been announced. New build projects based on lignite, hard coal and peat have a combined plant capacity of around 37,300 MW today.
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Two new nuclear power plants with a total capacity of around 3,200 MW are being constructed in the EU in Finland (Olkiluoto) and France (Flamanville), and nuclear power plants with a total capacity of a further 4,082 MW are being planned in Bulgaria, Romania and the Slovak Republic. In addition, output is being increased at existing plants.
New power plant capacity of roughly 52,780 MW is currently being planned based on
renewable energy sources such as wind, hydropower and biomass. In total, projects with a joint capacity of roughly 167,395 MW have been announced. Whether all of the announced new build projects will actually be realised will depend greatly on future primary energy price trends and political conditions (country-specific bonus/malus regulations) due to CO2 reduction strategies. Figure 2-3 gives break up of proposed (or planned) power plants with regard to the energy source. Figure 2-3:
Planned power projects in EU Planned Power Projec ts in EU (total 167395 MW)
67005 48805
50000 40000
RES
Other
88 Wind
Hydro
187 & waste
3233
Residues
469
power
Peat
Oil
7770
Nuclear
4075
2500 Gas
10000 MW 0
Lignite &
30000 20000
Biomass
33263
coal
70000 60000
Hard
80000
It is shown that renewable energies (including wind power) have taken a major share of 32 % (i.e, 52,782 MW).
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2.6
Pros & Cons of relevant Energy Generation Options
At present 46% of the total electricity is generated in Eurpoe is CO2 free. The following Figure 2-4 gives the break up of the power generation. Figure 2-4:
Break up of power generation Nuclear 30%
Biomass, waste, oil, etc 7% Wind 2% Hydro 10%
Coal 31%
Gas 20%
The following Table 2-1 gives pros and cons of relevant electricity generation projects Table 2-1:
Pros and cons of power generation options
Energy Source Nuclear
Pros •
•
Climate-protecting
Cons •
electricity generation with
in some European
no CO2 emissions
countries
Cost-effective and reliable
•
import dependency
•
Extensive effort and cost required for safety
High safety standard at western nuclear power
Long licensing process under nuclear law
supply with no critical
•
Social acceptance problem
•
Disposal and final storage of nuclear fuel not yet
plants
resolved politically
Coal
•
Hard coal can be procured
•
Growing demand for hard
cost-effectively by many
coal (predominantly from
providers on the world
China and India) and
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Energy Source
Pros •
Cons
market
limited transport capacities
Brown coal in Europe is a
entail price risks
readily available domestic
•
raw material •
Gas
•
•
Power plant technology
for natural gas •
Flue gas require cleaning
has great potential for
with corresponding cost
efficiency improvement
and effort for plants
Most environmentally
•
Volatile natural gas prices
friendly fossil fuel
are leading to large
relatively low CO2
fluctuations in electricity
emissions
generation costs
Electricity generation in
•
plants
Dependency on imports from a possible supply risk
highly efficient power
•
CO2 emissions higher than
•
Increasing concentration of
Short erection times and
export sources in
low investment costs for
politically unstable regions
new plants
Wind
•
Climate-protecting
•
Serious obstacles imposed
electricity generation with
by new environmental
no CO2 emissions
protection targets Expansion of existing
•
High plant efficiency
•
Cost-effective operation
potential is problematic for
•
Network services are
environmental policy
available extremely quickly
reasons
•
Flood protection support
•
•
High investment costs for new plants due to extensive compensatory measures not relating to electricity generation
Hydro
Serious obstacles imposed
•
Climate-protecting
•
Electricity generation with
by new environmental
no CO2 emissions
protection targets
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Energy Source
Pros
Cons Expansion of existing
•
High plant efficiency
•
Cost-effective operation
potential is problematic for
•
Network services are
environmental policy
available extremely quickly
reasons
•
Flood protection support
•
•
High investment costs for new plants due to extensive compensatory measures not relating to electricity generation
2.7
Requirement of efficient coal and gas Power Plants
CO2 emissions can be reduced gradually through technological development. The volume of CO2 produced from hard coal electricity generation can be reduced by around 35 % worldwide if low-efficiency power plants (the average global efficiency factor currently stands at 30 %) were replaced by power plants with a 46 % efficiency factor (current state of the art power plants). Therefore, the gradual reduction of CO2 emissions by technological development is the first option. It would result in profitable on three counts: •
resource protection, as less fuel is required for generating the same amount of electricity
•
substantial reduction in CO2 emissions
•
increased electricity generation from the same fuel amount
In the long term, electricity generation from fossil fuels could take place virtually CO2-free through capture and underground storage of CO2. The potential for CO2-reduction of coal-fired power plants is shown in the following Figure 2-5 (Source VGB). Figure 2-5:
Reduction potential in CO2
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1. Efficiency 2. CO2 Emissions gram of CO2 per kWh 3. Fuel consumption g/kWh
Average Worldwide 1.
30%
2.
1.116
3.
480
EU 1.
38%
2.
881
3.
480
Steam power plant State of the art 1. 45% 2. 743 3. 320
2010
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700oC technology 1.
>50 %
2.
669
3.
288
CCS technology
2020
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3. 3.1
Directives Applicable to Large Combustion Plants Legal basis in the EU
The European LCP-Directive 2001/80/EC (see annexure I) applies to combustion plants, the rated thermal input of which is equal to or greater than 50 MW, irrespective of the type of fuel used (solid, liquid or gaseous). In addition to this it shall apply only to combustion plants designed for production of energy with the exception of those, which make direct use of the products of combustion in manufacturing processes. The LCP-Directive defines emission limit values for the discharge of substances from the combustion plant into the air. These emission limit values define the permissible quantity of a substance contained in the waste gases from the combustion plant which may be discharged into the air during a given period; it shall be calculated in terms of mass per volume of the waste gases expressed in mg/Nm3, assuming an oxygen content by volume in the waste gas of 3% in the case of liquid and gaseous fuels, of 6% in the case of solid fuels and 15% for gas turbines. Member States of the EU should bring into force the laws, regulations and administrative provisions necessary to comply with the LCP-Directive. Germany had brought into force the 13. BImSchV, it implements the regulations of the LCP-Directive (English version of 13. BimSchV see annexure II).
3.2
Underlying information
Numerous documents, reports and information from member states, the industry, plant operators and authorities, as well as equipment suppliers and institutions active in environmental protection, have been called on. Further information was gathered during site visits in various European member states and in personal discussions on issues regarding the choice of technology and experiences during the application of reduction techniques.
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3.3
Document organisation
In Europe, the Power and/or Heat Generation sector is a heterogeneous industrial sector. The energy generation is based on numerous fuels, generally to be divided according to their state of aggregation into solid, liquid or gaseous fuels. Therefore this document has been vertically organised so that the individual fuels are listed successively, where joint aspects and techniques are described together, however, in the three introductory chapters.
3.4
The European Energy Industry
Within the European Union every available type of energy source is used for the generation of power and heat. In individual EU member states the selection of the fuel used for energy generation is largely based on the national fuel resources, e.g. on the local or national availability of hard coal, brown coal, biomass, peat, crude oil and natural gas. Since 1990, the share in electric power generated from fossil fuel energy sources has increased by approximately 16 %, while the demand increased by approx. 14 %. The share of the electric power generated from renewable energy sources (including hydroelectric power and biomass) increased by almost 20 %, which is higher than average. Combustion plants are operated either as large supply plants or as industrial combustion plants providing driving power (e.g. in the form of electric power, mechanical energy), steam or heat for industrial production processes.
3.5
Applied technologies
A variety of combustion techniques are applied to the energy generation overall. For the combustion of solid fuels, dust combustion, fluidised bed firing systems and grate firing are all considered conceivable (published by the EU in the BAT data sheet: "Reference Document on Best Available Techniques for Large Combustion Plants", on the conditions described in this document. The possible status of liquid and gaseous fuels corresponds to appropriate boilers, engines and gas turbines on the conditions described in this document. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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The system to be used is selected on the basis of the economic, technical, ecological and local requirements such as availability of the fuels, operational requirements, market conditions and requirements of the mains. Electric power is mainly generated by generating steam in a boiler fired with the selected fuel. This steam is supplied to a turbine that drives a generator, generating electric power. The degree of efficiency of the steam cycle is limited by the requirement to liquefy the steam after it leaves the turbine. Some liquid and gaseous fuels can be fired directly in order to drive turbines with combustion gas or they can be used in internal combustion engines driving the generator. Every technology offers certain advantages to the plant operator, especially regarding its operational suitability with regard to variable energy requirements.
3.6
Ecological issues
Most combustion plants use fuels and other raw materials mined from the Earth’s natural resources, in order to convert them into useable energy. Fossil fuels are the most widely available energy source currently used. However, their combustion leads to an important and sometimes significant burden for the environment as a whole. The combustion process causes the development of emissions into the air, water and soil, with air pollution considered one of the most severe ecological burdens. The most significant emissions developing during the combustion of fossil fuels are SO2, NOx, CO, fine dust (PM10) and greenhouse gases such as N2O and CO2. Further substances such as heavy metals, halogenated compounds and dioxins are discharged in smaller quantities.
3.7
Conditions
The possible emission values are based on daily average values, standard conditions and an O2 content of 6 % / 3 % / 15 % (solid fuels / liquid and gaseous fuels / gas turbines), and refer to a typical burden situation. Brief peak values during peak loads, start-up and shutdown processes and operational malfunctions of the exhaust gas cleaning systems, D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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which might be higher, must be reckoned with.
3.8
Unloading, storage and transport of fuels and additives
In Table 3-1 some options are summarised for avoiding emissions during unloading, storage and transport of fuels and additives such as lime, limestone, ammonia etc. Table 3-1:
Some options to avoid emissions during unloading, storage and transport of fuels and additives
Best possible technology Fine dust
•
Using loading and unloading equipment with as small a drop to the storage heap as possible to reduce the development of diffuse emissions (solid fuels).
•
Using water spray systems in countries with no risk of frost to reduce the development
of
diffuse
emissions
during the storage of solid fuels (solid fuels). •
Arranging transfer conveyors in safe surface areas outdoors so that damage by vehicles and other equipment can be avoided (solid fuels).
•
Using enclosed conveyors with well designed, robust ventilation and filter equipment
at
conveyor
transfer
locations to avoid dust emission (solid fuels). •
Optimising the transport systems to minimise
dust
development
and
transport on location (solid fuels). •
Applying the principles of excellent
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Best possible technology design and construction practice and appropriate maintenance (all fuels). •
Storing lime or limestone in silos with well designed, robust ventilation and filter equipment (all fuels).
Water contamination
•
Storage on sealed, drained surfaces, collection of drained water and water treatment in settling tanks (solid fuels).
•
Using storage systems for liquid fuels with impermeable protective walls able to hold 75 % of the maximum capacity of all tanks or at least the maximum contents of the largest tank.
•
The content of the tank should be indicated and an appropriate alarm system
used;
in
order
to
avoid
overfilling the storage tank, automatic control systems can be used (solid fuels). •
Installing pipelines in safe surface areas outdoors
so
that
leaks
can
be
determined quickly and damage by vehicles and other equipment avoided. For
inaccessible
pipelines,
double-
walled pipes can be used with an automatic
gap
control
(liquid
and
gaseous fuels). •
Collecting the runoff water (rain water) from
fuel
stores
and
treating
this
collected flow (settling tanks or waste water
treatment
plant)
prior
discharging waste water (solid fuels).
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Best possible technology Fire protection
•
Monitoring the storage areas for solid fuels with automatic systems, in order to detect spontaneous combustion and determine danger zones (solid fuels).
Diffuse emissions
•
Using leak detection systems for burner gas and alarm systems (liquid and gaseous fuels).
Efficient use of natural resources
•
Using
expansion
turbines
for
the
recovery of the energy contents of the pressurised burner gases (natural gas supplied via pressure pipes) (liquid and gaseous fuels). •
Preheating the burner gas by using the waste heat of the boiler or gas turbine (liquid and gaseous fuels).
Health and safety risk due to ammonia
•
For the transport and storage of pure liquid ammonia: pressure vessels for pure liquid ammonia > 100 m3 should be designed with a double wall and located below ground; vessels with a capacity not exceeding 100 m3 should be
manufactured
applying
the
annealing treatment (all fuels). •
Considering the safety aspect, using aqueous ammonia is less dangerous than storing and handling pure liquid ammonia (all fuels).
3.9
Pre-treatment of fuel
For solid fuels, the pre-treatment of the fuel mainly consists in blending and mixing in order to ensure stable combustion conditions and to reduce emission peaks. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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3.10
Fine dust emissions
The fine dust discharged during the combustion of solid or liquid fuels is almost exclusively composed of the mineral components. During the combustion of liquid fuels, poor combustion conditions lead to the development of soot. The combustion of natural gas does not constitute a significant dust emission source. In this case, the dust emission values are usually far less than 5 mg/Nm3, without the application of additional technical measures. Table 3-2:
Options regarding the reduction of fine dust emissions in fossil fired combustion plants, excepting gas combustion plants (excerpt from LCP-Directive)
Thermal combustion output (MWth)
Hard coal New plants
Existing
Liquid boiler fuels New plants
plants 50 – 100
Option
Dust emission values (mg/Nm3)
5 - 20
5 - 30
achieving these values
Existing plants
5 - 20
5 – 30
ESS or FF
ESS or FF in 100 – 300
5 - 20
5 - 25
5 - 20
5 – 25
combination with FGD (wet, hd or dai) for SF,
> 300
5 - 10
5 - 20
5 - 10
5 – 20
ESS or FF for FBF
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Output 1.1 Abbreviations: Dai
dry adsorbent injection
ESS
electrostatic separator
FBF
fluidised bed firing
FF
fibrous filter
FGD
flue gas desulphurisation
SF
dust combustion
Hd
half-dry
For the dedusting of exhaust gases in new and existing combustion plants, the applicable state of technology is the use of an electrostatic separator (ESS) or a fibrous filter (FF), where emission values below 5 mg/Nm3 are usually achieved by using a fibrous filter. Cyclone separators and mechanical dedusters alone cannot be considered sufficient; however, they can be used as a prepurification stage within the exhaust gas process. The possible state of technology regarding dedusting and the corresponding emission values are compiled in the table below. For combustion plants exceeding 100 MWth, and especially
exceeding
300 MWth,
the
dust
values
are
lower
because
flue
gas
desulphurisation processes, which are already state of the art for desulphurisation in Germany and the EU, also achieve a reduction of the fine dust.
3.11
Heavy metals
The emission of heavy metals results from their occurrence as a natural component in fossil fuels. Most of the heavy metals to be considered (As, Cd, Cr, Cu, Hg, Ni, Pb, Se, V, Zn) are usually released in the form of compounds (e.g. oxides, chlorides) together with dust. Therefore it is usually possible to reduce the heavy metal emissions by installing high-efficiency dedusting plants such as electrostatic separators or fibrous filters. Only Hg and Se occur at least partially in the steam phase. At the typical operating temperatures of separation plants, mercury indicates a high steam pressure and its separation with fine dust reduction facilities fluctuates significantly. With electrostatic separators or fibrous filters operated in combination with exhaust gas desulphurisation processes such as the limestone wash process, the spray absorption process or the dry adsorbent injection, the average Hg separation level is 75 % (50 % for electrostatic separators and 50 % for exhaust gas desulphurisation plants), and with an additionally D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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available selective catalytic reduction (SCR) in high-dust arrangement (arrangement between boiler and dust separator), it is possible to achieve 90 %.
3.12
SO2 emissions
Emissions of sulphur oxides mainly result from the sulphur occurring in the fuel. In general, natural gas is considered sulphur-free. With certain technical gases this is not the case, and in these cases desulphurisation of the gaseous fuel may be necessary. For combustion plants fired with solid and liquid fuels, the use of low-sulphur fuels and/or desulphurisation is usually an option. Table below (Table 3-3) gives various options regarding the reduction of SO2 emissions in hard and brown coal combustion plants (excerpt from LCP-Directive). Table 3-3:
Options regarding the reduction of SO2 emissions in hard and brown coal combustion plants (excerpt from LCP-Directive)
Thermal
SO2 emission values (mg/Nm3)
combustion
these values
Hard and brown coal
output
Option achieving
(MWth)
New plants
Existing plants
50 – 100
200 - 400*
200 - 400*
Low-sulphur fuel
150 - 400*
150 - 400*
or/and FGD (dai) or
(FBF)
(FBF)
FGD (hd) or FGD (wet)
100 - 200
100 - 250*
100 – 300
(depending on the plant size). Cleaners using seawater. Combined process
> 300
20 - 150*
20 - 200*
reducing NOx and
100 - 200
100 - 200*
SO2. limestone
(CFBF/PFBF)
(CFBF/PFBF)
injection (FBF).
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Output 1.1 Abbreviations: CFBF
circulating fluidised bed firing system
dai
dry adsorbent injection
FBF
fluidised bed firing system
FGD
flue gas desulphurisation
hd
half-dry
PFBF
pressure fluidised bed firing system
In most cases for plants exceeding 100 MWth, however, the use of low-sulphur fuel can only be taken into account as a supplementary measure in combination with other measures
reducing
the SO2
emissions. In addition to
using low-sulphur fuels,
desulphurisation by means of a wet cleaner (reduction rate 92 – 98 %) and the spray absorption process (reduction rate 85 – 92 %) are mainly considered applicable techniques, with a market share of more than 90 % already. Dry exhaust gas desulphurisation processes such as dry adsorbent injection are mainly used for plants with a thermal output of less than 300 MWth. The advantage of the wet cleaner is that it also reduces emissions of HCl, HF, dust and heavy metals. For plants with an output of less than 100 MWth, the wet cleaning process is not considered ideal due to high costs.
3.13
NOx emissions
The most significant nitrogen oxides discharged during combustion are nitrogen monoxide (NO) and nitrogen dioxide (NO2), with common designation NOx. For hard coal dust combustion plants, it is possible to reduce the NOx emissions with primary and secondary measures such as selective catalytic reaction (SCR), where the reduction rate of the SCR system is between 80 % and 95 %. The disadvantage of the application of SCR or SNCR is possible emissions of unconverted ammonia ("ammonia leak"). For small plants without major load fluctuations fired with solid fuels and with a stable fuel quality, the SNCR process is also considered a possible application to reduce NOx emissions.
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This means the use of sophisticated low-NOx burners in combination with other primary measures such as exhaust air return, staged combustion (air grading), fuel grading, etc. The application of primary measures tends to encourage incomplete combustion, causing a higher concentration of unburned carbon within the fly ash and a certain amount of carbon monoxide emissions. For boilers with a fluidised bed firing system firing solid fuels, a reduction of the NOx emission is possible by distributing the air or returning the exhaust gas. The NOx emissions from stationary and circulating fluidised bed firing systems differ slightly. Table 3-4 shown below enables conclusions regarding the minimisation of the NOx emissions and the corresponding emission values for hard coal. Table 3-4:
Options regarding the reduction of NOx emissions in hard coal combustion plants using different combustion techniques (excerpt from LCP-Directive)
Thermal
Combustion
combustion
technique
NOx emission values (mg/Nm3)
Option achieving these values
New plants
Existing plants
grate firing
200 - 300
200 - 300
Pm and/or SNCR
SF
90 - 300
90 - 300
Combination of Pm
output (MWth) 50 – 100
and SNCR or SCR
100 – 300
SFBF & PFBF
200 - 300
200 - 300
SF
90 - 200
90 - 200
Combination of Pm Combination of Pm together with SCR or combined process
SFBF, CFBF &
100 - 200
PFBF
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100 - 200
Combination of Pm together with SNCR
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Thermal
Combustion
combustion
technique
output
NOx emission values (mg/Nm3) New plants
Existing plants
90 - 150
90 - 200
Option achieving these values
(MWth) > 300
SF
Combination of Pm together with SCR or combined process
SFBF, CFBF &
50 - 150
PFBF Abbreviations: CFBF
circulating fluidised bed firing system
PFBF
pressure fluidised bed firing system
Pm
Primary measures reducing the NOx
SCR
selective catalytic NOx reduction
SF
dust combustion
SFBF
stationary fluidised bed firing system
SNCR
selective non-catalytic NOx reduction
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50 - 200
Combination of Pm
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4.
Best Available Techniques to increase Efficiency and reduce Emissions
For clean and new boilers, it can be stated that the efficiency levels around 86 % - 94 % (LHV), are currently recorded for solid fuel, The main losses are associated with flue-gas waste heat via the stack, unburned carbon, waste heat in ash and radiation losses. The effect of fuel is important, assuming boilers with identical performance (same ambient and flue-gas temperature, same excess air, etc.) different boiler efficiencies are obtained depending on the nature of fuel as the following examples illustrate (LHV basis): Fuel
Efficiency [%]
International coal
94
Lignite
92
Low grade lignite
86
The best practices/best available techniques to increase efficiency and reduce the emissions are given in annexure III.
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5.
State of the Art -Reference Power Plant (Source VGB)
5.1
Brief Overview
The study on the "Reference Power Plant" has been produced with the aim of developing a 600 MW capacity hard-coal fired power plant operating at efficiency of 45.9%, concept that is sustainable in the future and will meet these challenges. The main aims of the concept study are to examine the feasibility of a modern power plant with sharply reduced emissions, taking account of the economic conditions that prevail in the deregulated energy market, and also to demonstrate the opportunities for North Rhine-Westphalia (Germany) as an industrial location. Operating on a hard coal Efficiency of over 48% could also be achieved with certain technical measures, which would require different site conditions and different economic boundary conditions. With efficiency of 45.9%, this power plant clearly above average of hard coal power plants currently in operation in Germany where average efficiency is around 38%. The study has shown that technically, economically and ecologically optimised power plant technologies based on hard coal provide good opportunities A number of innovative proposals have been included in the plant design. These innovations were selected according to the criteria of their profitability and feasibility using the materials and technologies currently available on the market. This study brings together the planning performance requirements of the plant operators, the planning work undertaken by the plant manufacturers and the results of the academic institutions. The following gives a brief description, details are given in the annexure IV.
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5.2
Details of the Study
The first phase of the study involved the collection of innovations and an evaluation. Here innovative ideas in the fields of plant planning, process technology, boilers, mechanical engineering, electrical engineering, instrumentation and control and generators were collected and each individual concept evaluated. The decision on whether to incorporate such an innovation into the reference power plant was taken jointly by plant operators and plant constructors. Parallel to this, the innovation evaluation phase was used to investigate the economic feasibility of the different options of improving efficiency. Evaluation factors such as those for improving efficiency, reducing auxiliary station power requirements and increasing availability have been defined for these studies, based on existing market boundary conditions. Plant operators and plant constructors added their experience to these evaluation factors and together they were used to optimise the plant as a whole.
5.3
Innovations
The study started with a brainstorming phase to gather and evaluate ideas. In total, over eighty innovative concepts relating to plant planning, process engineering, boilers, mechanical engineering, electrical engineering, instrumentation & control, and the generator were raised and their technical and economic feasibility evaluated. The technical concepts were discussed in engineering meetings. The decision as to which of these ideas was to be incorporated in the preferred variant was prepared following a discussion of the findings in the project management group. The following innovative concepts that have been considered in the course of this study should be emphasized in particular: •
With the aim of maximizing power conversion in the turbine and also taking the other economic evaluation factors into account, the exhaust crosssection of the low-pressure turbine section is specified as 16 m2. Because of the high centrifugal forces, the exhaust blades must be made of titanium
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alloys. •
With the aim of minimizing capital expenditure, various concepts were studied for installation of the turbine. In the course of this study, a low-level foundation design, i.e. a turbine tabletop at an elevation of around 8 m was compared to conventional design with a tabletop at an elevation of around 16 m. Use of an elevated-level design of foundation for the turbinegenerator at 60 m was also considered.
•
Standard designs (tower-type and two-pass boilers) were also examined and evaluated, as was the concept of the horizontally fired boiler, the aim being to minimize investment costs.
5.4
Layout Planning
Layout planning was conducted with the aim of designing a compact and efficient plant, using as a basis existing project experience gained from standard reference power plants and hard-coal-fired power plants that have already been built. The in-line arrangement selected for the steam turbine-generator and boiler results in short steam lines and at the same time gives a short length of bus ducting and power transmission line to the outdoor switchyard. This feature minimizes cost. The side-by-side arrangement of the cooling tower and electrostatic precipitator allows efficient design of the flue-gas discharge system via the cooling tower, while achieving optimum routing of the circulating water system at the same time.
5.5
Thermodynamic Design
As part of the optimization process a thermodynamic study was made of the different variants. Below is an overview summarizing the findings: •
Utilization of hot mill air or flue gas waste heat by transferring the heat to the HP feed water-heating line.
•
Use of an external de-superheater to increase final feed water temperature up to 320°C.
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•
Reduction of pressure drop in the extraction lines for the HP feed water heaters.
•
Reduction in terminal temperature differences for HP feed water heaters.
•
Consideration of use of an additional LP feed water heater (9th feed water heater).
•
Thermo compression in the area of the LP feed water heaters.
•
Concepts for reheat temperature control (control within boiler or by spray attemperation or by allowing reheat temperature to slide).
•
Consideration of use of an HP feed water heater bypass for mobilization of short-term peak output.
•
Study of a feed water pump drive concept (turbine drive vs. electric drives with various designs).
•
Optimization of the cold end (LP turbine exhaust cross-section and size of cooling tower).
The power plant concept, which has been optimized for technical and economic factors, produces the following technical data: •
Gross capacity: 600 MW
•
Type of boiler: Tower-type boiler with vertical tubes and steam coil air heater
•
Heat recovery: Utilization of mill air heat recuperation
•
Flue gas discharge: Discharge via cooling tower
•
Turbine model: H30-40 / M30-63 / N30-2 x 16 m²
•
Main steam parameters: 285 bar / 600°C / 620°C
•
Condenser pressure: 45 mbar
•
Generator: Water/hydrogen cooling
•
Feed water heating stages: 8 feed water heaters + external de-superheater
•
Feed water final temperature: 303.4°C
•
Feed water pump concept: 3 x 50 % electric motor-driven feed water pumps, variable-speed drive with planetary gearing
In addition to the preferred variant, the following additional requirements for enhancing flexibility have been grouped together in the "flexibility package" option: D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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•
Fast activation of primary frequency control system, as required in the DVG Grid Code "Network and System Rules of the German Transmission System Operators"), 1998 edition.
•
Option of providing additional power by partly bypassing the HP feed water heaters and
•
Use of header-type HP feed water heater instead of tube-sheet design type.
The flexibility package thus takes into account the plant operators' desire to be able to match the power plant’s mode of operation to the requirements of a volatile electricity market, over and beyond straight base load operation.
5.6
Steam Turbine Plant (Turbine, Generator)
The turbine modules used belong to the Siemens steam turbine product line named HMN with best reliability and availability values over the last decades. It is a turboset with separate HP, IP and LP turbine sections. A rigid connection (via so-called push rods) is implemented between the intermediatepressure outer casing and the low-pressure inner casing. This push rod concept for the HMN series turbine allows thermal axial expansion of the rotor system (moving blades) and that of the casing (stationary blades) to be matched. The result of this is a reduction in the axial clearances for the sealing elements between rotor and casing, and thus an improvement in the efficiency of the turbine-generator.
5.7
High-Pressure Turbine section
As high-pressure turbine the module H30-40 will be used. It’s a barrel-type design best suited for sophisticated steam conditions and assigned power output demand. The inlet parameters for the main steam entering the high-pressure turbine section are 600°C at 285 bar.
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The high-pressure turbine section has a barrel-type design. The radial joint is located in the middle of the barrel casing. An HP turbine is equipped with an inner casing due to the high steam parameters of 600°C/285 bar. The HP turbine blading consists of a diagonal stage, which is designed with a low degree of reaction and 17 stages of type 3DSTM (3D design with reduced secondary losses). The entire blading system is designed using the 3DVTM design principle (3DVTM: 3D design with variable stage reaction) so as to optimize blade efficiency. The materials used for the moving and stationary blades are exclusively high-alloy chromium steels with a chromium content of 10 % - 12 %.
5.8
Intermediate-Pressure Turbine section
As intermediate-pressure turbine the module M30-63 will be used. It’s a double flow turbine with inner casing design to cope best with highest reheat temperatures. The inlet parameters for the single-reheat steam entering the IP turbine are 620°C at 60 bar. The model M30-63 IP turbine is a double-flow, dual-shell turbine section. The materials for the shaft and inner casing are high-alloy chromium steels. The outer casing is made of nodular cast iron. This IP turbine module is designed for maximum reheat temperatures. As a outstanding reference the power plant "Isogo", Japan with a reheat temperature of 610°C can be stated. A further increase in reheat temperature to 620°C, affects the creeprupture strength of the shaft material. The use of a slightly modified alloy content for the 10 % chromium shaft material can increase the material strength. The use of 10 % chromium steel with boron shows promising results. Tests of creep-rupture strength for a shaft-like body are available from a German research project (VGB 158). The results are in alignment with the expected increase of creep rupture strength (time frame > 30,000 hours). D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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Active, external steam cooling in the steam inlet area is not required. Vortex cooling is used in the inlet flow area. The first blade stage of the IP turbine consists of a diagonal stage, which is designed with a low degree of reaction. At both the generator and turbine ends the blading of the turbine features 18 stages, these including 13 3DSTM blade profiles and four "tapered twisted" profiles. The first three moving blade stages of both flows are fabricated of Nimonic alloys (nickelbased alloys) on account of the high temperatures to which they are exposed. The other moving and stationary blades are fabricated of high-alloy chromium steels with a chromium content of 10 to 12%. In addition, a double T-head design is used for the blade roots of the first and second moving blade stages. This allows the high loading of centrifugal force on the blade roots and root fixing region. The acting centrifugal force is distributed between all blade contact surfaces and thus reduced.
5.9
Low-Pressure Turbine section
The newly developed turbine section N30-2 x 16m2 is planned as the low-pressure turbine section, a double-flow, dual-shell turbine section. The inlet parameters for the crossover steam are 269°C at 5.5 bar. The condenser pressure is 45 mbar. The inner casing features a welded design housing the stationary blade carrier. The lowpressure inner casing rests on the bearing pedestal base plates by means of support arms. The inner casing rests on a sliding plate and can allow axial movements transferred from the intermediate-pressure outer casing by the rigidly connected push rods. The points where the support arms penetrate the low-pressure outer casing are sealed by expansion joints. The LP outer casing and LP inner casing are thus completely decoupled. The N30-2 x 16 m2 features three drum stages and three standard stages per flow. The exhaust cross section of the final stage is 16 m2 per flow. Steel cannot be used to fabricate D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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this size of blades due to the high centrifugal force loading produced by peak blade speeds of Mach 2. A titanium alloy therefore has to be used. The titanium final stage blades feature a three-dimensional profile with integral shrouding, with a snubber in the middle of the profile. Gap losses at the blade tip are reduced by the integral shrouding. At rated speed the integral shroud and the snubber in the middle of the blade constitute in effect a rigid structure together with the adjacent blades, thereby forming a low-vibration blade assembly.
5.10
Generator Plant
The generator plant consists of a two-pole hydrogen-cooled turbo generator, which is rigidly coupled to the turbine. It has a direct water-cooled stator winding, a static exciter, a two-channel digital automatic voltage regulator and the necessary supply systems i.e. seal oil, hydrogen and primary water units. The stator winding is cooled directly by water, and the rotor is cooled directly by hydrogen. Losses occurring in the other components such as core losses, frictional losses and additional losses are dissipated directly by hydrogen. A large number of radial cooling slots ensure uniform dissipation of heat in the laminated core. The hydrogen is circulated in the closed cooling circuit inside the gas-tight and pressureproof generator frame by a radial blower fitted at the exciter end. The hydrogen coolers are installed in the generator frame. The water (primary water) treated for cooling the stator winding is circulated in the closed circuit by a pump and transfers the heat absorbed in the primary water cooler to the secondary water. The excitation energy is supplied to the rotor winding by a static exciter via slip rings. The excitation unit consists of an exciter transformer and a thyristor assembly in a three-phase bridge circuit.
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5.11
Boilers
Comparison of various boiler designs In order to find the most favorable boiler design for the reference power plant, three different boiler designs were examined. A tower boiler, a two-pass boiler and the innovative horizontally fired boiler were designed and compared with each other in respect of their costs and operational reliability. The aim of establishing specific advantages for each of the types of boiler resulted in different concepts of solution in respect of furnace and the pressure section. MPS mills and low-emission DS burners were used in all variants. The variant comparison is based on a data record for a power plant unit with a gross installed capacity of 550 MW. The fact that in the course of optimising the plant the decision was made that the gross installed capacity of the "preferred variant" would be 600 MW does not affect the conclusions arrived at when comparing the concepts. In order to achieve boiler efficiency of 95%, areas such as the cold end of the flue gas and the furnace were optimised.
Innovations in boiler The greatest improvement in efficiency is achieved by raising the steam parameters to the high steam conditions at the boiler outlet (600°C/620°C/292.5 bar). A further improvement in plant efficiency has been achieved by optimizing the economizer section and raising the feed water temperature. These temperature and pressure increases make it necessary to use new material for the walls (7 CrMoVTiB 10 10) and new super heater materials (hightemperature austenitic materials such as TP347HFG). The efficiency of the boiler is improved to 95% by keeping to the very low excess air coefficients of 1.15 and exhaust gas temperatures of 115°C. The distance to the dew point temperature for flue gas ducts and the electrostatic precipitator is achieved by the specified guaranteed coal with a sulphur content of only 0.6%. As a result of the low air ratio and the flue gas temperature window specified by the DENOX plant upstream of the air heater, the air alone is no longer adequate as the only heat sink because a partial flow of cold air must be routed past the air heater on account of the pulveriser mill air D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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temperature control system. A mill air heat exchanger, one of the innovations, removes the excess heat from the mills’ hot air so that application to the air heater is almost 100%. As a result of transferring this excess heat to the feed water economiser (parallel to the HP preheater section) an exhaust gas temperature of 115°C downstream of the air heater can be achieved. The vertical evaporator tubing in a Benson boiler is a further innovation. The spiral-wound plain tubing is state of the art here, as is a correspondingly high mass flow density to provide adequate cooling of the furnace encompassing walls that are exposed to a high thermal load. The advantages of vertical evaporator tubes pertain more to the design. There is a small advantage as regards auxiliary station power technique since slightly less power is required from the feed pump. From the point of view of production engineering, vertical tubing is easier to manufacture and to assemble. The tie-bars used for the spiralwound tubing are dispensed with. A flatter angle can be used on the hopper, thus allowing the height of the furnace to be reduced and also generating a cost benefit. The Benson range can be extended to a part load of 20%. This results in advantages when later on the RPP will be operated at intermediate load. The vertical evaporator tubing operates with mass flow densities approximately equivalent to a naturally recirculation boiler. For this reason, optimised inner ribs are required in order to provide adequate cooling. A swirl is created in the flow because of the inner ribs, extending the time the inner walls remain wet. The area of the boiling crisis is thus shifted into zones exposed to less heat flux, thus ensuring that the sudden jump in the temperatures of materials is considerably reduced. Heat flux profiles are largely balanced out as a result of the effect of natural circulation that applies with lower mass flow densities. Where it is known that excess heating occurs, this can be corrected by geometrical adjustments - for instance, larger tubes can be used around the burner. Efficiency can be enhanced further by operating the plant with a variable reheater outlet temperature. In the design point at 100% load, there is no injection during steady-state operation. Although the reheater outlet temperature drops with any movement away from the 100% load point, this proved to be the most economically efficient method for, initially, base-load operation and for when subsequently the plant will be operated at intermediate load. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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The partition pitch of 480 mm must also be seen as an innovation. There is no record to date of this kind of spacing becoming blocked. Apart from being able to reduce the height of the boiler by about 1 m, it is also easier to clean by overhead soot blowers. The materials selected for the boiler are:
5.12
•
Evaporator/superheater - vertical tubing
7CrMoVTiB 10 10
•
Superheater 1 support tube partition
HCM 12
•
Superheater 2
Super 304 H or TP 347 HFG
•
Superheater 3
HR3C or AC 66
•
HP outlet header
P92
•
Reheater 1 Outlet
7CrMoVTiB 10 10, HCM 12
•
Reheater 2
HR3C or AC66
•
Reheater outlet header
P92
Water and Steam Cycle
The water/steam cycle essentially consists of the supercritical steam generator, the steam turbine-generator with the condenser, the main condensate pumps, the low-pressure (LP) feed water heaters, the feed water tank, the feed water pumps, the high-pressure (HP) feed water heaters and the connecting pipes. The superheated steam produced in the steam generator is supplied to the turbine which drives the generator. After the steam has driven the HP turbine section and thus released part of its energy, it is passed to the reheater where it is heated up again and then routed to the IP turbine section. The steam flows directly from the IP turbine section to the LP turbine section, where it is expanded to condenser pressure. Finally the steam is condensed in the condenser. The heat of condensation is dissipated via the circulating water system. The condensate produced is collected in the condenser hotwell. The main condensate pumps pump the condensate from there through the LP feed water heaters into the feed D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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water tank. The feed water pumps are then used to pump the water from the feed water tank through the HP feed water heaters and back to the steam generator. The LP feed water heating line, the feed water tank and the HP feed water heaters are heated with steam extracted from the turbine. •
The condenser is a two-casing surface condenser with water boxes positioned at both sides. The steam dome, steam shell and the hotwell are welded structures, as are the water boxes. The following materials are used: Tubes of stainless steel (14401), tube sheets made of stainless steel (14571). The water boxes are made of Carbon steel.
•
Primary frequency control by means of condensate throttling: As the hotwell serves as a condensate storage vessel, there is no need here for an additional cold condensate storage tank.
•
2 x 100 % main condensate pumps: Only one pump operates during normal operation. Following condensate throttling, the second pump is cut in to pump to the feed water tank the condensate that has accumulated in the condenser hotwell in this process. This serves to return the system to its initial status.
•
Bypass cleaning of condensate using a separate 1 x 100% capacity condensate cleaning pump: A 2 x 50% capacity bypass cleaning system for condensate is implemented to satisfy the stringent water quality requirements of the Benson boiler for feed water that is low in salt and low in corrosion products. As a result of this configuration, condensate cleaning can be designed for comparatively low pressure levels and the unit can be operated completely independently of the condensate polishing system.
5.13
Cooling Water Systems
The cooling water systems essentially consist of the natural-draft wet cooling tower, the circulating water system with a make-up water supply system, the auxiliary cooling water system and the closed cooling water system.
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The circulating water pumps supply the condenser with circulating water from the cooling tower basin. Once the heat of condensation rejected to the condenser has been transferred to the circulating water, this water is routed to the natural-draft wet cooling tower. The heat is ultimately dissipated to the atmosphere via the cooling tower. To ensure the requisite cooling water quality, part of the cooling water is blown down. The system is topped up with make-up water to compensate for losses caused by evaporation and blowdown. The auxiliary cooling water is taken from the circulating water system upstream of the condenser. After it has absorbed the heat from the closed cooling water system, it is returned to the circulating water system downstream of the condenser. The closed cooling water system dissipates the heat from the individual cooling loads via the closed cooling water heat exchanger to the auxiliary cooling water system.
5.14
Technological Options
If the market boundary conditions result in higher economic evaluation factors, this signifies that technical solutions requiring higher specific investments to increase efficiency are then cost-effective. In a marginal case the specific additional investment may exactly match the "economic evaluation factor". If the additional investment is higher, the economics of the entire project are reduced. If additional investment is lower, the projects economics would increase accordingly. Assuming that the economic evaluation factors are higher than in the preferred option, as a result of changing boundary conditions (e.g. CO2 emission costs), the enhancement options summarized might then be of interest. In this context, the preferred option with all its boundary conditions would be the basis for option A. Option A, in turn, would be the basis for option B, etc. Details are shown in Table 5-1 and Figure 5-1 below. Turbine driven boiler feed-water pumps were not investigated, due to the fact that the increase of efficiency in comparison to feed-water pumps with frequency-converter is marginal and the capital cost are much higher than the advantage. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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Table 5-1: Description
Preferred option vs. additional options for boosting efficiency Preferred variant
Variant A
Variant B
Variant C
Variant D Plus using of fluegas heat
Plus frequency Specification
Basic
Converter BFP
Plus 320oC feed
Plus cond pressure
+optimized
Temperature
LP-Turbine 4×10m2
+9 stage preheating
Water end-
40 mbar with
Preheaters
transfer
system with low
temperature- heat transfer
+cond . pressure 35mbar
Live steam
3285bar/600oC/62
3285bar/600oC/62
3285bar/600oC/62
3285bar/600oC/62
3285bar/600oC/62
parameter
0o C
0oC
0o C
0oC
0o C
303.4oC
303.4oC
320oC
320.4oC
320.4oC
3HP/FWT/4LP
3HP/FWT/5LP
3HP/FWT/5LP
3HP/FWT/5LP
3HP/FWT/5LP
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes,HP Preheating
Yes, HP Preheating
Yes, HP Preheating
Yes, HP Preheating
Yes, HP Preheating
Yes
Yes
Yes
Yes
Yes
45mbar
45mbar
45mbar
40mbar
35mbar
N30-2×16m2
N30-2×16m2
N30-2×16m2
N30-4×10m2
N30-4×10m2
No
yes
Yes
yes
yes
No
yes
Yes
yes
yes
No
no
yes
yes
yes
No
no
no
yes
no
No
no
no
no
yes
No
no
no
no
no
Feed water endtemperature Number of preheaters External desuperheat er Steam air heater Use of mill air heat
recuperation Sliding reheat temperature Condenser pressure Low pressure turbine 9..stage
preheating Frequency – converter for boiler
feed – water pump (BFB) drive Feed water end – temperature 320oC
Condenser
pressure 40 mbar Condenser
pressure 35 mbar Condenser pressure 25
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Description
Preferred variant
Variant A
Variant B
Variant C
Variant D
No
no
no
no
yes
No
no
no
no
no
mbar Flue gas heat transfer system with low
temperature – heat
transfer Frequency converter for
condensate - pump
Figure 5-1:
Efficiency chart 47.3
47.5 47 46.5 45.9
46
46.1
46.2
Variant A
Variant B
46.5
45.5 45
Preferred variant***
798 Eur/kW
App. 20 EUR/kW gross per% Point**
App. 25 EUR/kW gross per% Point
Variant C
Variant D
App. 30 EUR/kW
Above 35
gross
EUR/kW gross
per% Point
per% Point
Effic ien c y ( %) Vs Ev aluatio n F ac to r *
Power output for all 600 MW at generator terminals * Increase in efficiency in Eur/kWwgross per % point ** The increase of efficiency in varient A considers also reduced aux. power which require additional investment of amount 8 EUR/kW gross *** In the concept study the Preferred Variant was investigated in detail; the Variants A-D have been derived.
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"Increase in efficiency" as an economic evaluation factor of the variant under review (e.g. Variant A: 20 €/kWgross per % point) then represents the additional investment that can be justified in economic terms relative to both the gross installed capacity of the power plant and an efficiency increase of 1 % point net. The respective predecessor variant is the basis for each case. For Variant A that would be the preferred variant, for Variant B it would be Variant A and so on. The increase in efficiency of Variant A compared to the preferred variant also includes the efficiency effect that results from a reduction in the auxiliary power requirement (by changing the feed water pump drive). This reduction in the auxiliary power requirement increases the specific investment for Variant A by an additional 8 €/kW (gross) and corresponds to a parallel rise in the "auxiliary power requirement economic evaluation factor". Independently of the measures presented above, a further increase in efficiency to over 47.3 % is possible by further reducing condenser pressure or by increasing the main steam parameters. If the overall concept is changed, by in example considering dual reheat, additional enhancement options are then available. However, all measures require considerable additional investments.
5.15
Summary
The principle challenges of the power supply industry today are security of supply, lowcost generation of electricity, environmental protection and conservation of available resources. This study on the "Reference Power Plant" has been produced with the aim of developing a hard-coal fired power plant concept that is sustainable in the future and will meet these challenges. The main aims of the concept study are to examine the feasibility of a modern power plant with sharply reduced emissions, taking account of the economic conditions that prevail in the deregulated energy market. The first phase of the study involved the collection of innovations and an evaluation. Here innovative ideas in the fields of plant planning, process technology, boilers, mechanical engineering, electrical engineering, instrumentation and control and generators were collected and each individual concept evaluated. The decision on whether to incorporate such an innovation into the reference power plant was taken jointly by plant operators and D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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plant constructors. Parallel to this, the innovation evaluation phase was used to investigate the economic feasibility of the different options of improving efficiency. Evaluation factors such as those for improving efficiency, reducing auxiliary station power requirements and increasing availability have been defined for these studies, based on existing market boundary conditions. Plant operators and plant constructors added their experience to these evaluation factors and together they were used to optimise the plant as a whole. In this study the power plant concept which is optimized for technical and economic aspects is called the "Preferred variant" and is characterized by the following data: •
Gross installed capacity
600 MW
•
Net Installed capacity
555 MW
•
Net efficiency
45.9 %
•
Main steam parameters
285 bar / 600°C / 620°C
•
Feed water end temperature
303.4°C
•
Condenser pressure
45 mbar, wet closed-circuit cooling via draft cooling tower
•
Price of the plant
478 mill €
•
Specific plant price
797 € / kW gross
•
Boiler type
Benson tower boiler with vertical tubes
•
Utilization of waste heat
Use of mill air heat
•
Flue gas cleaning
SCR-DENOX, electrostatic precipitator, flue gas desulphurization unit using limestone
•
Flue gas discharge
Discharge via cooling tower
•
Steam turbine
three-casing steam turbine with simple intermediate heating and low pressure stages made of titanium alloy
•
Generator
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•
Economiser stages
Eight economizers + external desuperheater
•
Feed water pump concept
3 x 50% electric motor-driven feed water Pumps, variable -speed drive with planetary gearing
The efficiency of the optimum power plant concept "Preferred variant" for the prevailing market conditions is 45.9 %. At less than 800 € gross of installed capacity, the price of the plant is in a range where the RPP is an extremely competitive method of generating energy as compared to the alternatives. The process parameters are crucial for the high efficiency. These include parameters such as high steam pressure and high steam temperatures (285 bar/600°C/620°C), which in certain areas require the use of materials that have only recently been shown to be operationally reliable. As it is practically impossible nowadays to use river water for cooling, closed-circuit cooling via a cooling tower is planned for the reference power plant. The cooling tower is also used to discharge the flue gases produced during combustion. Sulphur and nitrogen are removed from these gases before handling in a separate part of the plant. The standard of flue gas cleaning complies with the strict reference values recently adopted for the European Union. If river water could be used for cooling, it would increase the net efficiency of the plant by a further percentage point to approximately 47 %. Certain technical measures could also be applied to achieve efficiency of over 48 % but these would require different economic boundary conditions than could be assumed at the present time. The effects of double reheating have not been included in this study because the additional investment required would be considerably higher than could be justified by the resulting increased efficiency of about half a percentage point. The efficiency of 45.9 % achieved by the RPP far exceeds the average efficiency currently achieved by hard-coal-fired power plants in Germany. Taking the average efficiency of 38 % (Germany) as a reference point, the increased efficiency of around 8 percentage points reduces the amount of fuel used and consequently also CO2 emissions by around 20 %. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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If the power generated in coal-fired power plants in 2020 were only to be generated in plants with efficiency of at least 46%, the CO2 emissions from coal-fired power plants of 9.1 billion t (average efficiency of 34%, worldwide) forecast for 2020 could be reduced by a further 2.3 billion t to 6.8 billion t (average efficiency 46%). The forecast increase of worldwide CO2 emissions attributable to coal-fired power generation in the period between 2000 and 2020 would thus be reduced from 63 % to 21 %. The studies of economic feasibility for this concept show that the RPP is more efficient than all options for hard-coal-fired power plants that are currently being examined in detail, providing that CO2 emissions entitlements do not have a considerable cost impact. The only solutions that are comparable in economic terms in the fossil-fuelled large power plant sector are modern lignite fired power plants (MLP) and combined cycle power plants using natural gas. In terms of economic feasibility, when these two alternative power plants are compared only the modern lignite fired power plant is slightly more costeffective than the RPP , primarily on account of its extremely low fuel costs, which can also safely be considered to remain at a constant level in real terms over the entire operating period. However, this type of plant can only be operated by companies that have appropriate access to lignite. Nevertheless, this type of plant is extremely relevant to those utilities in terms of covering base-load requirement reliably and cost-effectively in the long term. The time when a plant of the same type as the reference power plant can be used to supply to the grid purely on the basis of commercial decisions depends crucially on the trends that can be expected in the intervening period in respect of the revenues that can be generated on the wholesale market. Currently these are not adequate to justify an investment on business grounds. Overall, the figure for power generation costs based on assumptions made on an individual basis for the new base-load plants that need to be built and which after 17 years will be changed over to intermediate load operation indicate a figure of around 3.3 and 3.5 €ct/kWh. With the planned mode of operation, the RPP is more cost effective than the gas-fired combined-cycle plant, in spite of the considerably higher efficiency of this latter type of D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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plant and its substantially lower investment costs. The main reason for this is that a hard coal price of 41 €/t (heating value for coal to the design specification = 25 GJ/t, purchase price per tce = 48 €) can be assumed. In view of the very considerable reserves available across the world, the low market access barriers and the market structure characterized by intense competition, hard coal prices will at most increase marginally after being adjusted for inflation over the entire period of operation. This result is comparatively robust because the price of natural gas must not increase by more than 0.5 %/year in real terms in order to make up for the cost advantage of hard coal under these conditions. This is unlikely in view of the increase in demand world-wide for gas as a source of energy and its undeniable environmental advantages, which have been documented in the corresponding asking price. Only if - against all expectations - the price of hard coal were to increase in real terms by more than 1 %/year (and the price of gas did not increase at more than this rate over the same period) would the combined cycle plant produce better economic results than the hard-coal-fired reference power plant. However, these economic advantages only apply if possible cost impacts resulting from measures to reduce CO2 are not taken into account. If the impact of CO2 is only 5 € in real terms per ton of CO2 emitted overall, the hard-coal-fired reference power plant would be considerably less viable economically than the gas-fired combined cycle power plant. The same applies even if the gas price rises by up to 1.2 %/year in real terms and the price increase for hard coal is limited to 0% /year. Thus, apart from the usual market risks, plant operators have to deal with the additional unforeseeable business situations that arise from the political aim of CO2 entitlement trading and the actual national arrangements for this as it affects fossil-fuelled power plants. Coal-fired power plants using the latest designs, which are extremely efficient in terms climate protection and conserving resources, can only be built if the suitable political framework conditions are developed for them. The objectives cannot be met under any circumstances if additional costs for CO2 entitlements were to be loaded onto an efficient hard-coal-fired power plant for reasons of climate protection.
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This would only make investment in this technology more difficult and at the same time promote one-sided building of additional gas-fired power plants, with the result that security of supply would be impaired in the long term and dependency on this fuel would lead to increased (price) dependency. In view of the fact that it is expected that hard coal will be extremely significant as an alternative fuel for power generation - on a global scale as well - in the longer term, the successful implementation of the reference power plant in Germany would have considerable export potential, which would contribute to maintaining the expertise of power plant vendors.
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6.
Role of 700°C Technology for the Carbon-free Power Supply 1)
2)
3)
Dr. Franz Bauer , Dr. Dariush Hourfar , Helmut Tschaffon 1) 2)
E.ON Engineering GmbH, Gelsenkirchen 3)
6.1
VGB PowerTech e.V., Essen E.ON Energie AG, München
Introduction and Background
In face of the climate change and the necessary carbon abatement strategy the requirements for the future power supply are carbon-free technologies. Any scenario analysis provided by the IEA Energy Outlook or the publications of the European Commission on this field show the absolute need for carbon-based primary resources for the coming decades. The consequences are the development of carbon-free technologies. The outcome of the Technology Platform ZEP "Zero Emission fossil-fuelled Power Plants" is three major paths for carbon-free technologies: •
post-combustion – capture of CO2 out of the flue gas
•
pre-combustion – integrated gasification of coal in combination with a CO shift
•
oxy-fuel – combustion of fossil fuel under oxygen atmosphere
Clear position of any institution analysing in depth the constraints and opportunities for a carbon free power supply like the TP ZEP or the Eurelectric study ´Role of Electricity´ is that all technological options are needed. Having in mind that climate protection is a global issue the relevance of global competition is evident. As well as the availability of competitive technologies will be decisive for the capability to cope with the challenges and finally to succeed in providing a clean and secure and affordable power supply in the future. The intention of this paper is to point out the strategic role of the 700°C technology, starting with the intention in considering the thermodynamic of the Carnot process and the D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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materials needed to achieve high process parameters leading to high efficient power plants. It is clearly to emphasize: The 700°C technology is the pre-requisite for the successful implementation of two of the described technology paths - post-combustion and oxy-fuel - based on a high-efficient basic process. Consequently we will deal with the status, the current and coming activities and the perspectives of the 700°C technology. Concerning the overall strategic and political context a position referring the necessity for the coherent regulatory framework and a consistent deployment strategy will be given.
6.2
Status 700°C Technology
The beginning of activities concentrating on the development of materials able to bear 700°C steam parameters lies in the early 90´s, leading to the AD700 project, phase I and II, which were finished end of 2006. AD 700 was co-funded by the European Commission within FP5 launched in 1998 by the Commissioner and supported by about 40 stakeholders from equipment suppliers, power generators and the scientific community. The key objective of AD 700 was the development of innovative turbine and boiler designs, identifying and developing material for the components in the high temperature regions and assessment of the economic viability. A broad range of materials - Ni-based alloys have - been investigated, analysed and tested in small samples. Parallel comprehensive studies have been performed in order to work out a basic power plant concept. The goal was to achieve efficiency figures of more than 50 % net and to give first indications about the economic feasibility of this concept. The necessity of carbon-free technology was not yet on the agenda. The main issue was identification and selection of appropriate materials and testing. The targets set out for the boiler materials with respect to mechanical strength were:
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•
Martensitic materials 100 N/mm2 at 650 °C/100,000 hours
•
Austenitic materials 100 N/mm2 at 700 °C/100,000 hours
•
Nickel-based alloys 100 N/mm2 at 750 °C/100,000 hours
These targets were met for the austenitic materials and the superalloys but not for the martensitic materials. It was not possible to find a better steel type than P92. Sandvik developed the austenitic superheater tube material with the trade name Sanicro 25, and Special Metals developed a superalloy for superheater tubes with the trade name Inconel 740. The nickel-based alloys identified for the boiler and steam lines are materials such as Inconel 617 and Nimonic 263. For the turbine components Inconel 617, 625 and Waspalloy, respectively are foreseen for rotors, castings and blade and bolts. A large number of long term creep tests have been carried out both on bar, tube and forged material, and they are still in progress. Table 6-1:
Composition of AD 700 materials (alloys)
Element
Ni
Cr
Co
Mo
Other
A 625
63.5
21.5
0
9
Al, Ti, Nb
A 617
52
22
12
9.5
Al, Ti
A C263
51
20
20
6
Al, Ti
A 740
50
24
20
0.5
Al, Ti, Nm
Sanicro 25 (A 174)
25
22
1.5
0
W, Cu, Fe
Material
The result of both phases of AD 700 was a preference set of materials covering all requirements for boiler materials consisting of membrane wall, headers, pipe-work and valves and for turbine materials with shaft, blades, pipe-work and valves. As important as the material development was the outcome of the plant concept studies demonstrating the principal possibility of both – high efficiency and promising cost figures.
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In the following the key issues are presented. The thermodynamic of the Carnot process with relevance for the plant concept is shown in Figure 6-1. Figure 6-1:
Carnot efficiency and efficiencies of some seawater-cooled plants
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Consequently the thermodynamic scheme for 700°C concept is described in Figure 6-2. Figure 6-2:
AD 700 thermodynamic cycle
As the nickel-based alloys are extremely expensive, the concept of compact design was studied. The aim is to minimize the amount of these materials – e.g. by making the steam lines as short as possible. These studies identified considerable room for savings, which also will be valuable for more conventional plants. For the turbine, a turbine inlet valve, forged rotor, welded rotor, moving blades, stationary blades, bolting and welding of pressure containment parts were considered. Also innovative designs with the aim of reduced need for the nickel-based alloys have been studied. Considerable effort has been made to establish business plans for a full-scale demonstration plant. The studies included a detailed risk assessment and again a check on the feasibility taking the latest material strength values and prices into consideration. The technology is still feasible even when a moderate price for CO2 quotas is used.
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Parallel national projects have been initiated, particularly MARCKO I and II covering both material design and tests in small samples.
Emax Initiative Based on these encouraging results of AD 700 an industry funded strategy study was started with the goal to make a comprehensive evaluation in general and to define the steps necessary to bring this technology to real application under market conditions. The work was done under the umbrella of the Emax Initiative - an industry group driven by the generators coordinated by VGB. The clear result was the confirmation that this concept offers the potential to cover both high efficiency and the fundamental basis for a carbon-free power supply on fossil fuels and before entering into the erection of a demo plant two steps are stringently needed: •
a component test under realistic operation conditions with the experience of design and fabrication of the near full scale components and
•
out of this learning process a pre-engineering study for the specifications for a demo plant covering material concept, design and fabrication, balance of plant consisting of process figures necessary for 50% efficiency, component design and operation requirements.
At the end one will get reliable figures in terms of actions to be done, the realistic time schedule and the financial means needed for realisation – ready for a sound assessment of the contribution for a carbon abatement strategy, of the market opportunities, of the funding requirements - public and industry - and the time and cost risks aligned with.
6.3
Current and Coming Activities of the 700°C Technology
COMTES700 First step of the study was the design, construction, erection and operation of the component test facility (CTF) COMTES 700; i.e. a facility implemented into an operating boiler consisting the key components of a boiler like evaporator membrane wall, superheater, pipe-work, headers and valves, additionally with a turbine control valve and D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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referring ducts. Due to the fact that under FP a continuation in terms of funding was not possible the resources of the Research Fund for Coal and Steel were taken, an occasion to thank for the co-operative support of the DG RTD. The project has been co-ordinated by VGB integrating partners from the equipment suppliers and the generators, i.e. 9 European generators are working together in terms of financing and exchanging experience and pursuing this technology with the goal of implementation in due time. The work started in spring 2004, the component test facility went into operation in July 2005 and until now more than 10.000 operating hours could be achieved. The CTF represented a considerable challenge. The principle diagram may look relatively simple, but the integration in the power plant with all necessary steam-, drain-, vent lines, instrumentation and control equipment represent a really big task, which in this case was made even bigger because the time from the official start to actual operation was only one year and delivery times for the tube and pipe material were long. E.ON has been responsible for the integration and operation of COMTES700 in Scholven F (see Figure 6-3). Figure 6-3:
Principle diagram COMTES700
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Generally one can state that the learning process was very interesting, but very useful and has given clear indications what has to be analysed and investigated within the preengineering study as the next step. Parallel to COMTES700 a test rig in the Esbjerg power plant was installed with a certain precursor function, meaning testing in advance design and material as a kind of accelerating process and to take preventive measures.
PP 700 – pre-engineering study The project has been conceived as a cross-border transnational project. To date, 10 European energy utilities (E.ON Energie AG, Electricité de France, France, Electrabel European Generation, Belgium, EnBW Kraftwerke AG, Germany, EVN AG, Austria, DONG Energy Generation, Denmark, RWE Power AG, Germany, STEAG AG, Germany, Vattenfall Europe Mining & Generation AG & Co. KG, Germany, Vattenfall A/S Nordic Generation, Denmark) have joined together with the aim of developing this sustainable European concept for generating power on the basis of fossil fuels. In the context of the envisaged pre-engineering study the European energy utilities involved will determine viable technical and economic decision-making principles for power plants with a live steam condition of 700°C. The European Generators are working together supported by a European regional fund (local government of the State of North Rhine-Westphalia) in pursuing the issue of preengineering. The equipment suppliers are integrated by orders placed by VGB the coordinator. Goal is to perform an innovative pre-engineering study in order to be ready for a more detailed evaluation of the opportunities of the technology at the end. The necessity and political will of a convincing carbon abatement strategy is on the agenda now. In the mean time the TP ZEP was launched strongly developed and pushed by the stakeholders from the electric power industry lead by VGB. The work of the pre-engineering study has started and is terminated for autumn of 2008 an exciting time is lying ahead.
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6.4
Perspectives of the 700°C Technology
As stated before the necessity for a CO2 free power supply technology is on the political agenda; having in mind the results of the scenario analysis from IEA and EC DG TREN postulating a major share of power supply will be on fossil resources - there is no other way if security of supply and competitiveness are taken into account. The technological development of fossil-fired power plants, with a marked increase in efficiency levels to around 50 %, is at the forefront. In the phase of power plant renewal in the medium term, i.e. in the years from around 2015 to 2020, it could thus be ensured if the project is concluded successfully that the European CO2 reduction targets can be achieved by means of efficient, economically viable power plant solutions. A reduction in specific CO2 emissions per MWh generated of around 25 % compared with power plants currently in operation (mean efficiency 38 %) is associated with 700°C technology. The proportional reduction in the fuel mass flow used can also partly offset rising fuel prices. The competitiveness of the European energy industry and also of the capital goods industry that is to be supplied with electricity and process heat can thus be stabilized. In the long term, i.e. in the new construction period after 2020, the realization and safe operation of a power plant using 700°C technology represents together with other technologies like Oxyfuel and IGCC an essential prerequisite for flushing CO2 economically out of the flue gases and transferring it to suitable deposits. E.ON has announced to build and to operate a demonstration plant based on the 700°C technology. This is an important step towards carbon free technologies. The power output was fixed in the before mentioned pre-engineering study with 550 MW gross. The process will be a single reheat cycle. E.ON plans to erect the demo plant in the northern part of Germany. The operation is scheduled for 2014. To realise this ambitious plan a lot of additional R&D work has to be done. Only to mention one example: It´s necessary to produce reheat pipes out of Alloy 617 with an outer diameter of about 500 mm and a wall thickness of 30 mm. A COORETEC associated project with participation of VGB, several German electric utilities and manufacturers was launched in this year to produce a longitudinal welded pipe. In the beginning of 2008 the pipe will be produced. Afterwards the pipe will be examined and a creep test follows. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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6.5
Regulatory and Political Framework
The 700°C technology is of even higher relevance than before. Two paths out of three major routes are requesting a high-efficient basic plant concept respectively highly efficient components in order to master the technical challenge of resource saving, carbon capturing and affordable generation technologies. This can be provided by the 700°C technology. The key characteristics of the post-combustion process as well the oxy-fuel process are components demanding process heat in form of steam or water or flue gas. In spite of the fact that for determining exact figures intensive research work has to be done. But the first results are showing very clearly that only by a high temperature thermodynamic cycle combined with an optimal integration of the additional steps of carbon capture out of the flue gas - post-combustion - or air separation for delivering oxygen for the combustion oxy-fuel - the goal of a resource saving carbon-free power supply at affordable costs can be achieved. Efficiency of any process step is the key for success. Another important opportunity of the 700°C technology is the one for synergies; synergies in a sense that the key characteristics of components of different power plant concepts are based on the same principles of laws of nature. The design, the construction, the test and the operation of components - even for a specific concept - delivers worthwhile results for other concept using the physical or chemical processes. By respecting and supporting this effect a more efficient and successful development of new power plant concept will be ensured - the key argument for pursuing different promising power plant concept in parallel. This helps essentially to reduce the unavoidable risks of technical development. The strategic context is determined by the following facts: •
Evidence of climate change
•
Access to primary resources
•
Worldwide competition and
•
Necessity to develop Carbon-free technologies for fossil based plants.
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The consequences for the European Union, but the other global players also are to find the right political measures respectively regulatory framework in order to enable to develop the appropriate technologies in due time with the available resources - human and financial one. The supply with energy or power is at the end a question with a huge social background even potential for explosive stresses. The past and the evident future challenge has shown that it is necessary to reflect on the •
goal and approach for public funded research programme
•
balance between basic and industrial research and application
•
relation between public and industry funded research and development and
•
role of political and regulatory framework.
It is time now to intensify a broad and open discussion between all involved parties now with the aim to draw coherent conclusions and to initiate a stringent action plan. The initiative of the European Commission to establish a Strategic Energy Technology Plan, SET plan, has been appreciated. At the end huge investments have to done, but investments are only possible if a level playing field is in place covering the above-mentioned topics.
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7.
Road Map to High Efficiency Power Plant
Efficiency refers in this context not only to the choice of the power plant process and its parameters, but also to operation and maintenance and the efficiencies attained in daily operation. The planning, construction and project handling for such power plants also must be efficient if the projects are to be successful. Finally, the term "efficiency" as applied to net efficiency must be regarded in relation to the power plant efficiencies possible and attainable in each country. The high-efficiency power plant by itself or as an element of Carbon capture and storage (CCS) schemes represents an important contribution to the conservation of fuel resources, but also to climate protection. The European Road to build high efficiency power plants is given in the annexure V, exemplarily Evonik Steag.
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8.
Technology Platform for Zero Emission Power Plants by 2020
Following developments in clean power generation and the priority given to "zero emission power generation" in the Sixth Framework Programme (FP6) industrial stakeholders and the research community had several meetings which resulted in the creation of a technology platform for zero emission fossil fuel power plants. The strategic deployment document and the strategic research agenda as well as more details are given in annexures VI(a) and VI(b). The Experts agree that CO2 capture and storage technology (CCS), together with improved energy conversion efficiency, is a near-term solution to reducing CO2 emissions from fossil fuel power generation on a massive scale. Its immediate deployment is therefore vital if we are to avoid the catastrophic consequences of climate change we are facing today. Yet despite most of the technology elements being available, CCS is still not deployed for two key reasons: 1. The costs and risks still outweigh the commercial benefits 2. The regulatory framework for CO2 storage is not sufficiently defined. The Strategic Research Agenda therefore describes a collaborative programme of technology development for reducing the costs and risks of deployment; while the Strategic Deployment Document outlines how we can accelerate the market to achieve zero emission power production by 2020.
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PART II 9. 9.1
Definition of Efficiency Parameters - Basics Efficiency
There are different ways of describing the efficiency of a combustion installation. There are also a number of national guidelines describing acceptance tests and the measurements of certain efficiencies. The efficiencies defined in this report as well as in the annexures to this report are to be understood as efficiencies at a certain electrical output and normal operating mode, i.e. as the power station is operated in daily generation mode. They are calculated from averaged measured values attained from the values recorded over a certain period of time. This section gives the brief details of various types of efficiencies dealing with the power plants and other related parameters such as: •
Carnot efficiency: The ideal efficiency of a thermal process or ‘Carnot’ efficiency is a measure of the quality of the conversion of heat into work
•
thermal efficiency: thermal efficiency considers only the actual cycle process used in the power station. The efficiency is then the ratio of the useful mechanical output to the heat flow transferred to the cycle process media (as a rule, air or water)
•
the degree of fuel efficiency: The degree of fuel efficiency is defined for cogeneration plants, which generate and emit electrical and thermal energy (heat). For these plants, the useful output consists of the sum of the generated electrical energy and the generated thermal energy
•
proportional auxiliary station service
•
high voltage net capacity
•
heat consumption of generating unit
•
overall efficiency of power plant
•
fuel consumption
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•
specific fuel consumption
•
unit efficiency: Unit efficiency is then the ratio of the net electrical output to the energy supplied with the fuel. The electrical output according to this definition is the output on the high voltage side of the main transformer.
•
unit efficiency for steam withdrawal: If, in a power station unit, steam is extracted for heating or process purposes, then this steam is no longer available for power generation. In order to be able to compare the unit efficiency in this case with the efficiency of pure power generation, the electrical output which could be obtained from the extracted heating steam if it were to expand to the condenser pressure, has to be added to the electrical output.
•
exergy concept and exergy efficiency
•
influence of climate conditions on efficiency
•
relationship between efficiency and environmental issues
Details on this are given in annexure VII.
9.2
Losses of Efficiency in Combustion Plants
The heat energy resulting from the combustion of fossil fuels is transferred to the working medium (steam). During this process, part of the energy is lost in the flue-gas. The total losses from the generation of steam depend on the fuel (ash and water content, calorific value); the capacity and operation of the steam generator; the air-fuel mix; the final temperature of the flue gas; and the mode of operation. The operation of the steam generator requires continuous surveillance. The heat losses from the steam generator can be categorised as: •
losses via the off-gas. These depend on the flue-gas temperature, air mix, fuel composition and the level of fouling of the boiler
•
losses through unburned fuel, the chemical energy of which is not converted. Incomplete combustion causes CO and hydrocarbons to occur in the flue-gas
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•
losses through unburned material in the residues, such as carbon in bottom and fly ash
•
losses via the bottom and fly ash from a DBB and the slag and fly ash from a WBB
•
losses through conduction and radiation. These mainly depend on the quality of insulation of the steam generator.
In addition to the heat losses, the energy consumption needed for the operation of auxiliary machinery (fuel transport equipment, coal mills, pumps and fans, ash removal systems, cleaning of the heating surfaces, etc.) also has to be taken into consideration. Poor combustion lowers the economic viability, increases the environmental impacts and is detrimental to the safety of the plant. The following parameters affect the viability of the plant and may, therefore, be monitored to keep the plant’s efficiency as high as possible: •
fuel composition
•
fineness of grind
•
flue-gas composition (O2, CO2, CO)
•
air mix and flue-gas volume flow
•
air leaking into the combustor
•
boiler fouling
•
temperatures of the combustion air and flue-gases
•
temperature behaviour within the heating surfaces
•
reduction of draught
•
flame profile
•
combustible proportion of residue (annealing loss)
9.3
Generic Technical Measures to improve Large Combustion Plant's Efficiency
9.3.1
Combustion
The fuel is mixed with air and burned in the boiler. It is not possible to obtain an ideal mix between the fuel and air, and therefore, more air than is necessary for stoichiometric D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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combustion is supplied to the boiler. Furthermore, a small percentage of the fuel does not fully combust. The flue-gas temperature must be kept high enough to prevent condensation of acid substances on the heating surfaces.
9.3.2
Unburned Carbon in Ash
Optimisation of the combustion leads to less unburned carbon-in-ash. It should be noted that NOX abatement technologies using combustion modification (primary measures) show a tendency of increased unburned carbon. Increased unburned carbon could also worsen and harm the quality of the coal fly ash and make it difficult, or even prevent, their utilisation for certain applications, with the risk that they may not comply with the specifications and requirements laid down in relevant national and European standards.
9.3.3
Air Excess
The amount of excess air used depends on the type of boiler and on the nature of the fuel. Typically, 12 – 20 % excess air is used for a pulverised coal-fired boiler with a dry bottom. For reasons of combustion quality (related to CO and unburned carbon formation), and for corrosion and safety reasons (e.g. risk of explosion in the boiler) it is often not possible to reduce the excess air levels further.
9.3.4
Steam
The most important factors in increasing efficiency are the highest possible temperature and pressure of the working medium. In modern plants the partially expended steam is reheated by one or more reheating stages.
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9.3.5
Flue-Gas Temperature
The flue-gas temperature leaving the clean boiler (depends on the fuel type) is traditionally between 120°C and 170°C, due to risks of acid corrosion by the condensation of sulphuric acid. However, some designs sometimes incorporate a second stage of air heaters to lower this temperature below 100°C, but with special claddings on the air heater and the stack, which makes this reduction economically unprofitable. By power plants designed without stacks, the flue-gas temperature is between 65 and 70°C.
9.3.6
Vacuum in the Condenser
After leaving the low-pressure section of the steam turbine, the steam is condensed in condensers and the heat released into the cooling water. In order to ensure the maximum pressure drop over the steam turbines, it is desirable to reduce the vacuum to a minimum. In general, the temperature of the cooling water dictates the vacuum, which is lower with once-through cooling systems than with a cooling tower. The best electrical efficiency is possible by seawater or fresh water-cooling and a condenser-pressure with approximately 3.0 kPa. The preferred option is to use seawater or river water if this available.
9.3.7
Variable Pressure and fixed Pressure Operation
In fixed pressure operations, the pressure before the turbines at all load levels is kept more or less constant by changes in the flow cross-section at the turbine inlet. In variable pressure operations with the turbine inlet cross-section at its maximum, the power output is regulated by changes in the pressure before the turbines.
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9.3.8
Condensate and Feed-Water Preheating
The condensate coming out of the condenser and the boiler feed-water are heated by steam to just under the saturation temperature of the extracted steam. The thermal energy from the condensing process thus feeds back into the system, reducing the amount of heat otherwise released from the condenser, therefore improving the efficiency. The optimisation measures taken to improve the efficiency of power plants between 1993 and 2000 which resulted in a CO2 reduction of 11.0 million tonnes per year as shown below: Steam generator
39 %
Process optimization
14 %
Turbine
25 %
Auxiliary power
14 %
The reduction of emissions from large combustion plants can be carried out in different ways.
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10.
Energy Balance
Following figure shows an energy flow chart (Sankey diagram) of the individual losses within the heat flow of a condensation power plant. Figure 10-1: Sankey diagram of individual losses
E ner gy flo w in a 200 MW po wer u n it, lay o u t des ig n : & ) 167.8 kg/s; 245 bar/520 °C Mass flow live steam ( m s First intermediate superheating 78.5 bar/530 °C
Second intermediate superheating 22 bar/540 °C Condenser pressure approx. 0.0235 bar Feed water end preheating 303.6 °C (nine preheater stages) a) Flue gas – air preheating
H) Circulation losses (water and steam)
b) Feed water preheating
I) Turbine losses
c) Fresh air
K) Thermodynamic cycle (water & steam)
d) Make-up water
L) Losses of generator
e) Feed pump turbo set
M) Auxiliary consumption, overall
A) Fuel energy input
N) Auxiliary consumption of the turbine installation
B) Losses due to radiation and unburnt material
O) Auxiliary consumption of the steam generators
C) Exhaust gas loss
P) Steam generator output
D) Ash losses
Q) Turbine output
E) Pipe losses
R) Generator output
F) Loss of the feed pump turbo set
S) Effective useful output
G) Heat loss of the preheating installation
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When analysing the efficiency of conventional power plants, it must be taken into account that the fuel costs amount to approximately 75 % of the total average production costs, which clearly shows the necessity of operating the plant at optimum efficiencies. Not only
cost-effectiveness is required, but also the reduction of the emission of air-polluting substances by saving fuel.
10.1
Efficiency of German Power Plants
Efficiencies in German power plants vary widely and keep increasing due to enhancements of the power plant technology. At present, the data summarised in the following Table 10-1 can be assumed. Table 10-1:
Efficiency of German Power Plants
Power plant type
Net electrical efficiencies in % Current optimum
Target
values
values
Natural gas and steam power plant with condensation
55 – 58
60
Fossil fuel steam power plant with condensation
40 – 48
50
Natural gas turbine power plant
30 – 36
40
Closely connected to the efficiency of a condensation power plant are the process losses, also called cooling water losses or condensation losses. For physical reasons it is impossible to avoid them in a condensation power plant. They are the biggest losses and therefore strongly reduce the power plant efficiency. They are determined by the type of steam power cycle: 1.
the design of the water-steam circuit (e.g. with or without intermediate superheating)
2.
the pressures and temperatures of the live steam and superheated steam
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3.
the cooling water temperature and, connected to it, the condensation pressure
4.
main condensate and feed water pre-heating
One practical solution for the exact determination of the losses or efficiencies is to monitor the heat output and the generated effective output (kW). The heat capacity (kJ/s, MJ/s) is the heat input into the process for a certain time unit.
10.2
Efficiency Degradation
The degradation of the plant efficiency is a normal process, but a permanent challenge to minimise the degree of degradation. State of the art of plant operation and maintenance is to keep the degradation level between the ranges of +/- 0.1 % net efficiency. This impressive figure is the outcome of a well equipped plant in terms of monitoring and cleaning system. The major components of the monitoring system are stress gauges, temperatures measuring and vibration control devices and software tools to calculate heat balance, frequency analysis etc.: The major cleaning systems are water conditioning, condenser cleaning and soot blowing systems. The backbone of these systems is a state of the art process control & instrumentation system allowing the record of any relevant data. The targeted systems respectively indicators are heat transfer decrease in the boiler caused by ash deposits, heat transfer decrease in the condenser caused by fouling effects, air control of the boiler island, avoidance of corrosion in the boiler and pipe system by the well suited operation of the Electrostatic Precipitator and last but not least the turbine island – vibration and frequency control.
10.3
Energy Balance of a Coal-Fired Power Plant Unit
As an example, two energy balances are drawn up for a German coal-fired power plant with a useful output of 830 MW. In one case the steam generator forms the balance limit, D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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in the other one it is the boiler house. The energy balances were drawn up by means of measured values, which were found in a field test for the determination of the unit heat consumption. During the measurements, 100% of the combustion air was taken from the boiler house (internal suction) at a temperature of 55°C. Preheating of the combustion air in relation to the ambient air amounted to 45°C, which corresponds to a heat quantity of 18.5 MW. Yet the radiation and pipe losses at the steam generator according to DIN EN 12952-15 amount to only 2.43 MW. The examination of the supplied heat flows for both energy balances shows a difference of 15.5 MW. This difference is based on the difference between the actual radiation and pipe losses and the radiation and pipe losses as determined according to DIN EN 12952-15. This means that the choice of different balance limits leads to differing at the time of calculating the heat flow input of the fuel heat input. These differences directly influence the calculation of the boiler efficiency and the unit efficiency, where the error amounts to approximately 0.5 % points for the unit efficiency. The radiation and pipe losses of the respective steam generators are included as lumpsum figures in the "indirect method" according to DIN EN 12952-15, depending on the maximum useful heat output. As the measurement results of the different coal-fired power plant units show, the amounts of losses determined that way do not correspond to the actual radiation and pipe losses of the steam generators. If this method is applied in practice, the following consequences result from it: •
Especially for steam generators operated with internal suction, it is not possible to draw up conclusive balance limits. For heating up the combustion air within the steam generation building, the amount of "recovered" energy is much bigger than that which is radiated by the boiler according to the current regulations.
•
The choice of different balance limits around the steam generator leads to differences in the calculation of the fuel heat input. The deviations resulting from this directly affect the unit efficiency.
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Output 1.1 Figure 10-2: Energy balance for the steam generator
Boiler house
tL,env =
10,0 °C
mLhL =
-6,0 MW
(QSt+QV)back =
15,5 MW
tsupply =
25,0 °C
tL,sb =
55,0 °C
mLhL =
12,5 MW
QSt,tot =
13,5 MW QV =
Pfan =
3,0 MW
QN,sb =
831,0 MW
3,0 MW
Steam generator Pcomill =
2,0 MW
Pcomill =
2,0 MW
QA =
53,0 MW
mB(Hu+hB) =
891,0 MW
mB(Hu+hB) =
891,0 MW
QS,F =
8,0 MW
supplied heat flows
supplied heat flows
-6,0 MW
13,5 MW
+
3,0 MW
+
831,0 MW
+
2,0 MW
+
2,0 MW
+
53,0 MW
+
891,0 MW
+
891,0 MW
+
8,0 MW
total
890,0 MW
total
905,5 MW
total
905,5 MW
Efficiency, limit of balance steam generator Efficiency, limit of balance boiler house
10.4
dissipated heat flows
12,5 MW
91,77% 93,03%
Operating efficiency in European Power Plants
The following Figure 10-3, Figure 10-4 and Figure 10-5 show the attainable efficiency of power plants and comparison of various technologies such as IGCC, super critical, nuclear, gas turbine etc in addition to technology perspectives and incremental efficiency improvement in power plants.
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Output 1.1 Figure 10-3: Comparison of efficiency of various types of power plants (Source VGB)
Figure 10-4: Technology perspective in terms of efficiency (Source VGB)
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Output 1.1 Figure 10-5: Efficiency improvement of coal fired boilers (Source VGB)
The efficiencies are evaluated based on the following formula:
Efficiency =
Net kWh Energy Input as NCV
The complexity of thermal power plant efficiencies reporting in India and Germany are given in annexure VIII. The various formulas used for estimation of thermal power plants are given below:
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10.5
Operating Efficiency of typical Indian Power Plants compared to German Power Plants
The following gives the variation in efficiency figures due to evaluation criteria for a typical Indian power plant of 500 MW. Basis for calculation (typical design values) •
Gross rating of the plant
500.15 MW
•
Turbine gross heat rate
1944.6 kcal/kWh
•
Auxiliary power
8.00 %
•
Auxiliary power
40.012 MW
•
Net power output
460.138 MW
•
Coal consumption
278.5 t/h
•
Coal GCV
4,000 kcal/kg
•
Coal NCV
3,758 kcal/kg
•
Fixed carbon
28 %
•
Volatile matter
22 %
•
Moisture
20 %
•
Ash
30 %
Coal analysis
The efficiencies, as described in chapter 10.4 could be determined as follows: •
Efficiency # 1 (based on net kWh & GCV)
35.52%
•
Efficiency # 2 (based net kWh & NCV)
37.81 %
•
Efficiency # 3 (based on gross kWh & GCV)
38.61%
•
Efficiency # 4 (based on gross kWh/NCV)
41.10%
For comparison the typical efficiency of German power plant is given to •
Gross rating of the plant
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•
Turbine gross heat rate
1,944.6 kcal/kWh
•
Auxiliary power
10.80 %
•
Auxiliary power
54 MW
•
Net power output
446 MW
•
Coal consumption
189.7 t/h
•
Coal GCV
5,615 kcal/kg
•
Coal NCV
5,386 kcal/kg
The efficiencies, as described in chapter 10.4 could be determined as follows:
10.6
•
Efficiency # 1 (based on Net kWh & GCV)
36.01 %
•
Efficiency # 2 (based Net kWh & NCV)
37.54 %
•
Efficiency # 3 (based on Gross kWh & GCV)
40.37 %
•
Efficiency # 4 (based on Gross kWh/NCV)
42.09 %
Comparison of published efficiencies
Comparison of published efficiency values for different types of power plant is difficult for several reasons: •
Differences in the calculation of the heating value of the fuel
•
Differences in site conditions and especially condenser pressure
•
Differences in plant design, such as single or double stage reheat at otherwise a similar plant design
•
Consideration of gross or net efficiencies (and plant output), use of add-on equipment such as for example a flue gas desulphurisation
The condenser pressure is commonly the most important factor, and going from a condenser pressure of 0.05 bar, which requires a cooling water temperature of 27-28°C, to 0.02 bar, with a cooling water temperature of 14-15ºC, produces an extra three percentage points. Thus, for proper comparisons, all actual plant efficiencies ought to be recalculated to 'standard conditions' in order to be meaningful.
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In Europe, efficiencies are expressed on the basis of lower heating value (LHV), which is the difference between the higher heating value (HHV which is the total amount of energy contained in the fuel) and the latent heat of evaporation of the water contained in the products of combustion. In Europe, evaluating efficiency by considering the LHV is considered accurate assessment of the 'useful' energy of the fuel for plant where this water goes to the atmosphere in the flue gas stream. The ratio of HHV to LHV depends on coal composition and its heat content. For fuels such as natural gas and biomass with higher hydrogen content, this ratio will be much higher. This complicates comparisons between different technologies and fuels. When generating efficiencies are quoted as based on HHV, the electricity output is divided by the HHV of the fuel used. When they are quoted on an LHV basis, the output is instead divided by the LHV value of the fuel. Consequently, HHV generating efficiencies are lower than LHV generating efficiencies. For example, a coal-fired steam plant with an HHV efficiency of 40% has an LHV efficiency of approximately 42 %, provided plant design and site conditions are the same. A broad understanding of the current status of coal-based power plant can be gained from a comparison of several state-of-the-art steam plants around the world, as illustrated below (Table 10-2): Table 10-2:
Differences in efficiency based on HHV and LHV (Source: www.berr.gov.uk/files/file30703.pdf)
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The Japanese and US plants have relatively high condenser pressures compared to the Danish plant. The Niederaussem plant burns a lower grade lignite, whereas the others are fuelled with bituminous 'trading' coals.
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11.
Key parameters and basis for measurements
11.1
Key operating parameters
Coal fired power plants built are based on the proven and fully developed engineering. The major key operating parameters of power plants are main steam pressure, main steam pressure and condenser vacuum. The hard coal fired power plants, designed for net efficiency in the region of 45%. The following table (Table 11-1) shows the development of boiler efficiency based on the improvement in main steam pressures and temperatures along with related operating parameters. Table 11-1:
Development of boiler efficiency based on improvement in steam pressures, temperatures and other parameters
Parameter
Unit
#1
#2
#3
#4
#5
#6
#7
#8
#9
Efficiency
%
41.0
41.2
41.5
41.6
42.5
42.6
42.8
43.7
44.3
Improvement
%
0
0.5
0.8
0.25
2.0
0.3
0.5
2.0
1.3
Main steam
bar
250
250
250
250
250
300
300
300
300
°C
260
280
280
280
280
280
300
300
300
°C
530
530
540
540
540
540
540
580
580
°C
540
540
560
560
560
560
560
600
600
Condenser
bar
0.047
0.047
0.047
0.047
0.047
0.047
0.047
0.047
0.04
Exhaust gas
°C
130
130
125
125
125
125
125
125
125
pressure Feed water temperature Main steam temperature Reheater steam temperature pressure
temperature
It can be seen that the efficiency is raised as steam pressures and temperatures are raised while the flue gas exhaust temperature and condenser vacuum lowered. Similarly, the following table (Table 11-2) gives the parameters for lignite based power plants. Table 11-2:
Typical boilers operating parameters Parameter
Dim.
Neurath
Schwarze
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Lippen
Niederaussem
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Efficiency
%
Unit E
Pumpe
35.5
40.6
41.7
dorf
Unit K
42.3
45.2
Improvement in efficiency
%
14.4
2.7
1.4
6.9
Main steam pressure
bar
165
262
266
267
269
Feed water temperature
°C
235
274
270
295
Main steam temperature
°C
525
547
545
554
580
Reheater temperature
°C
525
565
581
583
600
Condenser pressure
bar
0.66
0.035/0.046
0.041
0.038
0.028/0.034
In addition to the above the following Table 11-3 summarizes key operating parameters of different power plants in Europe. Table 11-3:
11.2
Key operating parameters of the power plants in Europe
Fuel Parameter
Coal is a natural product. For this reasons its chemical, physical and technological properties depend on the herbal starting substances and the geometrical conditions during carbonisation. The knowledge of chemical, physical and technological properties of coal is of utmost importance for its use as fuel in combustion plants. A German Standard, DIN 51700, defines the most important analysis procedures for the uniform description of properties of solid fuels. To assess the coal, a distinction is made between the pit coal as delivered and the water D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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and ash-free substance (waf). The moisture and ash-free substance contains only the burnable parts of the solid and volatile elements. Prerequisite for smooth operation are the knowledge of and information about these characteristics and properties. The following overview shows the most important characteristics: •
Calorific value
•
Ash content
•
Water content
•
Volatile elements
•
Sulphur content
•
Elementary analysis of the ash
•
Melting behaviour of the ash
•
Mineral size fraction of the pit coal
•
Composition of the mixture
•
Elementary analysis of the coal
•
Apparent weight
•
Grinding fineness of the pulverised fuel
•
Grindability of the coal
The details of the above listed characteristics are given in annexure IX. 11.3
Air & Flue Gas Parameters
The detailed parameters under this category need to be measured/monitored are given as well in the annexure IX. To determine the individual efficiency, the following parameters have to be measured in individual systems: electrical power, pressure, temperature, mass flow, differential pressure and oxygen content. When the measuring data are determined, wear, pollution and leakages have to be taken into account; at least they should be documented. 11.4
Data required
The data required for assessing the effeminacy, output, performance etc given in the D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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annexure IX. •
Table 1:
Parameters required for efficiency determination by energy balance method (Source ASME PTC 4)
•
Table 2:
Parameters required for efficiency determination by inputoutput method
•
Table 3:
Parameter required for capacity determination
•
Table 4:
Parameters required for steam temperature /control range determination
•
Table 5:
Parameters required for excess air determination
•
Table 6:
Parameters required for water / steam pressure drop determination
•
Table 7:
Parameters required for air / flue gas pressure drop determination
•
Table 8:
Parameters required for air infiltration determination
•
Table 9:
Parameters required for fuel, air and flue gas flow determination
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12.
Official Statistics for Efficiency Indicator and Plant Reliability
Each member state of the European Union is obliged to deliver statistical data. The energy sector takes an essential part in the statistics. Special focus is laid on plant efficiency and plant reliability. Special investigations are often made in order to allow an in depth analysis of specific topics. An example is the report of the EU Joint Research Centre, JRC. In addition to the basics the analysis and tools are essential elements to judge a power plant process and appraise it in the whole complexity. With this knowledge and the fact that the single component or single systems have to be measured prepared can a basic measurement be accomplished. But at first specific data are essential. To furnish single countries in Europe, and the very different regions over there, with energy, it is important to be aware of a few facts about the development, afforded power amount and coal consumption. The details about the common technical processes, general fuel heat conversion in boilers, typical elements of a steam cycle are given in annexure X.
12.1
Reports on Analysis and Tools for Efficiency Indicators
Based on the selected and described indicators samples for standard reports used in the EU are given. These official reports are published by national authorities as well as 1.
Eurostat (the Statistical Office of the EU), "Energy, Transport and Environment Indicators" http://epp.eurostat.ec.europa.eu/portal/page?_pageid=0,1136052&_dad= portal&_schema=PORTAL
2.
EU Joint Research Centre, "Reference Document on Best Available Techniques for Energy Efficiency", and download possible under http://eippcb.jrc.es/pages/FActivities.htm (scroll down to "Energy Efficiency" and download the draft document)
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12.2
Excerpts from Eurostat-Document
As official statistics Eurostat has published newest energy indicators for example on energy intensity, gross inland consumption per capita et al. The extracts are given in the annexure XI.
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13.
Performance Indicators & Monitoring
13.1
Introduction
In the liberalized energy market the evaluation of the performance of an own power plant compared to other power pants (benchmarking) is of great importance. To optimise the performance of a power plant in competition: •
the compilation of availability data and evaluation of performance indicators and
•
the comparison of indicators of a single plant with the indicators of peer groups
are strategic tools for many VGB-member-companies. In performance indicators and monitoring of the power plants VGB is very active and is collecting data and information from members' power plants since 1970. The data provide the information about the availability and utilisation of the thermal power plants in order to compare the quality of the power plants and to assess plants behaviour in daily operation. The basic tasks involved in the performance monitoring are •
Collecting of power plant performance indicators with the help of the VGB online power plant information system KISSY (KISSY is power plant information system which include collection and evaluation of performance indicators) As these as these strategic tools were of great importance for power plant operators during the last thirty years the hitherto used old dBase related tool was replaced by a new modern online-power-plantinformation-system KISSY, which is discussed more in detail. With the aid of KISSY, benchmarking can be carried out efficiently.
•
Determination of conventions for the publication of performance data of power plants
•
Preparation of availability- and unavailability reports
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•
Definition of new performance indicators for comparative assessment of the performance of power plants in the liberalized power market
•
Management of road shows for performance indicators and power plant benchmarks
•
Appropriate guideline updating
The major parameters monitored for performance of power plants in Europe are: •
Time availability
•
Energy availability
•
Time utilisation
•
Energy utilisation
•
Start-up reliability
Time availability The time availability is the quotient of the available time and the reference period (calendar time). The available time is the difference between the reference period and the unavailable time.
kt =
kt tv
tN
tv tN Dimension
Time availability
h
Available time
h
Reference Period
h
Energy Availability The energy availability is the quotient of the available energy and the nominal energy. The available energy is the difference between the nominal energy and the unavailable energy. The nominal energy is the product of the nominal capacity and the reference period (calendar time).
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kW
Wv
WN
PN tN
kW =
Wv WN
kw =
WN − Wv PN ⋅ tN Dimension
Energy availability
-
Unavailable energy
MWh
Nominal energy
MWh
Nominal capacity
MWel
Reference Period
h
Time utilisation The time utilization is the quotient of the operating time and the reference period (calendar time). The time utilization is a measure for the real temporal use of a plant. It is independent of the level of the corresponding operating capacity.
nt =
nt
tB tN
tB tN Dimension
Time utilisation
-
Operating time
h
Reference period
h
Energy utilisation The energy utilization is the quotient of the energy generated and the nominal energy. The nominal energy is the product of the nominal capacity and the reference period (calendar time). The energy generated is the product of operating capacity and operating time (numerator).
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The energy utilization is a measure for the energy, which a plant has really generated. Frequently used are also the equivalent definitions "utilization duration" or "full load utilization hours" The correlation between energy utilization and utilization duration
nw
WB
WN
PN tN
nw =
WB WN
=
WB PN ⋅ tN
tN =
WB PN
=
n w ⋅ tN
Dimension Energy utilisation
-
Energy generated
MWh
Nominal energy
MWh
Nominal capacity
MWel
Reference period
h
Start-up reliability The start-up reliability is the quotient of the number of successful start-ups (se) and the sum of successful (se) and unsuccessful start-ups (sn). The start-up reliability is used for the evaluation of units whose service life depends essentially on the number of start-ups, e.g. gas turbines, emergency aggregates.
z=
se se + sn Dimension
z se
sn
Start-up reliability
-
Number of successful start-ups
-
Number of unsuccessful start-ups
-
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Classification of unavailability (NV) Planned unavailability: The beginning and duration of the unavailability have to be determined more than 4 weeks before commencement. Unplanned unavailability: The beginning of unavailability cannot be postponed or only up to 4 weeks. Post-ponable unavailability: The beginning of unavailability can be postponed more than 12 hours up to 4 weeks. Not post-ponable unavailability: The beginning of unavailability cannot be postponed or only up to 12 hours. These performance indicators are also basics of any benchmarking approaches (see chapter 15).
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14.
Software and Analytical Tools for Efficiency and Plant Reliability – Online and Offline
14.1
Introduction
The cost pressures in the power generation business force the power plant operators to take specific measures to improve the operating efficiency and reduce cost. Intelligent evaluation of existing in-service measured data using online and off line analytical tools is one efficient way to recognize the current potential for optimisation by assessing the processes and components. The benefits of online & offline software analytical tools are •
enhance the efficiency of your power plant operation,
•
arrive at maximum electric output that can be generated at the moment taking into account operational and technical constraints
•
computation of ratios and key figures (efficiencies, electric energy from cogeneration, start up cost, etc.)
•
comparison of performance indicators
•
component evaluation (steam generator, heat recovery steam generator, steam/gas turbine, steam- water cycle, condenser, pumps, flue gas circuit, etc.) for optimum and efficient operation
•
optimisation (example: soot-blowing, gas turbine compressor washing, cold end, etc.)
•
forecast (unit efficiency, maximum unit output, etc.)
•
measured-data reconciliation featuring neuronal plausibility checking
•
central alarm-signalling service system
•
individual "what if" process simulation
•
closed-loop operation
•
Individual daily, monthly reports, statistics
•
diagnosis and analysis
•
several others
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14.2
Software Analytical Tools / Modules
Several software analytical modules are available in EU, which are specifically designed for power plant for plant monitoring and optimisation. The typical systems, which are predominant in EU, are: •
General statistics for official use
•
Specific industry driven data collection and compilation tools
•
Systems for optimum operation (Which cover energy management systems / plant optimisation system /system services/systems integration – all in a single module package or individual modules)
•
Lifetime monitoring system
•
Data management system -including subprograms
•
Thermodynamic cycle calculation program – offline monitoring system
The above systems can be installed separately or as a combination with others. The details of these systems are given below:
14.3
Data Collection for the Performance Monitoring
For detailed analysis required data pertain to the above parameters from the power plants are collected very meticulously by VGB: More than 471 power plants across Europe is covered. The data were considered will be fed to the KISSY for the detailed analysis and review. The performance monitoring is carried out by data collection for various types of power plants such as: •
Fossil-fired units
•
Nuclear power plants
•
Combined cycle units
•
Gas turbine units
•
Capacity type
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•
•
Until 99 MW
100-199 MW
200-399 MW
400-500 MW
600 and above
All units
Fuel type by capacity
Bituminous coal fired units
Lignite fired units
Oil /Gas fired units
Furnace type by capacity
Bituminous coal fired units with dry bottom firing
Bituminous coal fired units with slap top firing
•
Units by single or dual boilers
•
Units by subcritical or supercritical pressure
The above units will be considered as total Europe, in addition the entire exercise will also be carried out for Germany Units.
14.4
Analysis for Performance Monitoring
The analysis covers about 217 power plants for the operating period po1997 to 2006. The information analysed for various parameters such as: •
Failure with out damage
•
Damage
•
Check/condition check
•
Lubrication
•
Maintenance
•
Inspection\
•
Preventive maintenance
•
Cleaning
•
Revision
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•
Refuelling
•
Reconstruction/refurbishment
•
Test/functional tests
•
Official test/measure
•
Other incidents
The above analysis is carried out for unavailability incidents per block and year and also for energy unavailability. The analysis will also include on equipment basis such as:
14.5
•
Power transmission
•
Distribution of solid fuels
•
Pressure system, feed water and steam sections
•
Support structure, enclosure, steam generator interior
•
Ash and slag removal, particulate removal
•
Bunker, feeder and pulverising systems
•
Main firing system
•
Combustion air system (primary and secondary)
•
Flue gas exhaust
•
Chemical flue gas treatment system including residual removal
•
Feed water system
•
Steam system
•
Steam turbine plant
•
Generator plant
•
Circulating water system
KISSY
KISSY is Power-Plant-Information-System is a relational data base system on an oracle platform. It currently covers availability data and performance indicators of over 9760 unit years of German and other European power plants. Every full member of VGB can feed data to KISSY data base and at any time read the complete data of his own power plants online D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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via internet. The relevant availability data and performance indicators, which have to be collected and analysed for benchmarking are defined and explained in VGB-guidelines. The new kind of operating power plants initiated by the liberalised market requires the consideration of further performance indicators as for instance •
indicators for commercial availability
•
damage- and condition-oriented indicators
which will be incorporated with the next planned enhancement of KISSY. Every full member of VGB which wants to feed availability data can get access to the KISSY database. Members will get username and password by VGB. Then they can feed, change and read data for their own power plants online via a secure access (SSL-encryption). Data of other power plants are not visible to them via internet. The System will guide on,
which availability data and which data for reporting unavailability incidents have to be collected. Additionally the basic data of the power plant units (see attachment E) have to be fed once
into the database by VGB in order to assign the units to their peer groups for analysis and reporting. The analysis of the anonymous data is done for peer groups by VGB. The data fed by members via internet into the KISSY data base will be transformed anonymous by VGB and related to peer groups for benchmarking. Peer groups cover data of power plants with similar characteristic attributes which therefore can be compared (anonymously) with respect to their performance. Main peer groups for standard reports are: •
fossil-fired units
•
nuclear units
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•
combined cycle units
•
gas turbine units
Arranged by: •
capacity
•
fuel
•
type of firing
•
single/dual boiler
•
sub- / supercritical
Analysis is done for: •
time availability
•
time utilization
•
energy availability
•
energy unavailability
•
energy utilization
All members, which feed data into the KISSY data base get for free the standard reports for the above mentioned peer groups with analysis of key figures of availability and unavailability of components (for the previous 10-years period) annually. Current reports are available for downloading on VGB`s website within a closed user group area for VGB-members only. These reports will be updated every 3 months. For other parties the standard reports are available at VGB Power Tech Services. The detailed procedure in using KISSY is given in annexure XII.
14.6
Systems for Optimized Operation
These are online tools to cover energy management systems / plant optimisation system / system services/systems integration.
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These online analytical tools continuously assess plant operation, comparing it with a current calculated optimum so that the unit can be run at maximum efficiency. These tools are normally based on a three-tiered concept – evaluation, optimisation and forecast for cost-relevant power plant sections. Potential for optimisation is indicated, and even minimal reductions in efficiency are pinpointed. All results are evaluated at cost so that the effects of different operating parameters can be directly compared. The most important task of the plant optimisation system is to monitor the current plant operation and to compare it with the currently possible optimum on a continuous basis. The calculations needed for this are executed automatically on the basis of the current mean values of this time class. The results are saved in the related time archive in the Data Management System and can thus be visualized in the same way as all other data. Two different concepts are followed for the plant diagnosis is •
The optimisation of the plant operation and
•
The monitoring of the components or parameters.
For further details please refer to annexure XXII. A.
Plant Optimisation Systems
The plant optimisation system combines and presents thermodynamic models of the Plant components with economic parameters, specifically variable operation costs, to determine the current deviation between actual and the corresponding optimum plant operation. The thermodynamic modelling takes into account limiting constraints of operation. The plant optimisation also includes an off line manual (what if) analysis tool that enables the user to conduct model-based analysis of plant operation. Plant optimisation system includes the following: •
Thermal cycle optimisation. This computes the entire turbine and regenerative cycle heat balance and simulates the plant so that operator can examine the improvements in heat rate and can change individual cycle parameter.
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•
Computes the boiler efficiency and simulates boiler parameters such that operator can examine the improvements in boiler efficiency.
•
Boiler tube life fractions and stress calculations.
The features of standard graphical representation of the complete package based on Process Flow Diagram and the P&ID are included. The graphic screen is developed in order to enable that the user to conduct model-based analysis of Plant operation and get the results in an understandable manner. The tool includes all required drawings and graphical representation of the total plant system covers all equipment and drives related to the Optimisation package. Process graphic displays will be developed by the power plant operator to have a complete overview of the package indicating the display of equipment of boiler and turbine auxiliaries. The dynamic data is clearly being indicated such that the operator need not refer to multiple diagrams to assess system operation. Arbitrary continuation break points between displays are not used in such systems. B.
Functional Requirements
The plant optimisation functions are based on model-based software. The system computes controllable losses related to plant parameters not being maintained at their design points based on actual loads. The model is also including option to identify equipment cleanliness for various heat transfer sections within the plant. The optimisation software also identifies the actual sequence of soot blowing so that costs of heat loss due to unclean heat transfer sections and the costs of soot blowing can be minimized. Typical Plant Optimisation System will perform the following functional requirements. C.
Boiler Stage Optimisation
The system incorporates complete thermal design. This provides a continuous on-line, cost-benefit assessment of where and when i.e., the actual sequence, to blow soot from individual boiler stage surface areas. The boiler optimisation calculations take into account the following factors:
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•
Main steam conditions
•
Hot reheat conditions
•
Fuel inlet conditions
•
Ambient air conditions
•
Soot blowing usage
•
Gas exit temperature
•
Leakage of air pre-heater
•
Boiler efficiency
•
Heat rate
With boiler optimisation model, operators can obtain a ranking of cost/benefit of soot blowing on monitored boiler stages. The boiler optimisation model will be developed for the following sections: •
Economizer
•
Water walls
•
Super heaters
•
Reheaters
•
Air heaters
The radiative heat transfers, convective heat transfers and heat & mass balance equations are used to generate the above models. High degree of boiler cleanliness shall thus be ensured. D.
Soot Blowing Optimisation
Soot blowing optimisation advises operators to clean boiler stages at appropriate time and location to optimise soot-blowing operation. The high quality boiler calculation advises the operator judicious soot blowing of boiler stages. The boiler cycle monitoring calculations provide the following results: •
Cleanliness factors on boiler stages
•
Furnace exit gas temperature
•
Flue gas temperatures between boiler stages
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•
Actual heat transfer coefficients for each boiler stages
•
Theoretical heat transfer coefficients for each boiler stages
•
Flue gas cross-flow velocities
•
Stage heat absorption
•
Stage average metal temperatures
•
Specific heat of both air and gas
•
Excess air
•
Stage cross flow velocities
Normally a suitable combustion model will be included in the software. E.
Thermal Cycle Optimisation
This module computes the entire turbine and regenerative cycle heat balance and simulates the section of the plant so that operator can examine the improvements in heat rate attainable by changing a cycle parameter. The turbine and regeneration cycle is modelled such that any change of boiler parameters can be examined in relation to the overall heat rate of the plant for what if-scenarios. The turbine optimisation model is normally developed for the following sections: 1. Turbine HP/IP/LP 2. Condenser 3. Deaerator 4. Feed water heaters 5. Pumps (Condensate, Boiler feed) For turbine performance optimisation standards such as ASME PTC6 "Enthalpy Drop" efficiency calculations for determining turbine efficiency will be applied. In monitoring turbine cycle performance the following parameters are calculated: •
Main steam flow
•
Reheat flow
•
Condenser steam flow
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•
Turbine stage flow
•
Individual turbine stage efficiencies
•
Overall HP, IP, LP turbine efficiencies
•
Turbine calculated wheel power
•
Turbine calculated exhaust enthalpies
•
Turbine calculated exhaust velocities
•
Cold reheat steam approach to saturation temperature
•
Superheat spray outlet approach to saturation temperature
•
Expansion line end point at condenser pressure
•
Used energy end point
The power plant personnel provides component degradation tool package, which evaluates heat rate and cost effect of the components detailed below. The calculable losses identify the losses associated with equipment degradation and those associated with nonmaintenance of design parameters independently. •
HP Turbine, IP Turbine, LP Turbine
•
Feed Water Heaters,
•
Condenser
•
Boiler Feed Pumps
•
Deaerator
•
Boiler
•
Turbine Extraction line
•
Condensate pumps
•
Heat Exchanger
In these packages, the turbine stages are considered as long as the steam is still dry at the respective outlet. Since the tools contain a thermodynamic model of the process, losses of the generator cannot be determined. For the same reason steam seal regulators cannot be modelled. However, if necessary, the leakage through the steam seal may be considered as boundary condition. In addition, overall system degradation can be evaluated. Graphical presentation of results will be furnished as a part of the optimisation guides provided to the operator. These will D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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be in the form of bar charts, X-Y plots, and plant mimics. Predictive and diagnostic tools package is adopted in the form of ‘What if’ for diagnosing plant degradation. Those included in the ‘What if’ analysis are the following items, which can be modified by the user to see the effects on plant generation, heat rate and boiler efficiency: •
Throttle pressure
•
Throttle temperature
•
Reheat temperature
•
Condenser backpressure
•
Superheat spray flow
•
Reheat spray flow
•
Final feed water temperature
•
Boiler excess air
•
Flue gas exit temperature
•
Heater bypass
•
Feed water flow
•
Boiler feed pump efficiency
•
Boiler feed pump discharge pressure
•
Feed water heater terminal temperature differences
•
Feed water heater drain cooler approach
•
Turbine stage efficiencies
•
Condenser cleanliness factors
•
Condenser circulating water inlet temperature
•
Circulating water flow
•
Fuel ultimate analysis and heat content
•
Fuel firing rate
•
Boiler stage cleanliness factors
•
Gas re-circulation and tempering
•
Unburned carbon
•
Bottom ash and top ash removal
•
Air heater leakage
•
Ambient air condition
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This package can also be used to evaluate the effects of the following: •
Changing operating conditions and load
•
Comparing test data to best attainable and evaluating the results after ASME correction
•
Changing boiler stage geometry to evaluate the effects on steam and exit temperatures
14.7
Lifetime Monitoring System
The basic objectives of this type of tool are: •
Improved maintenance planning
•
Faster connection to grid
•
Better exploitation of material
Components of power plants exposed to high temperatures and pressures suffer serious material degradation during their lifetime. The appearance of the first cracks in the material indicates the need for component exchange or at least its repair. The degradation originates either from creep of the material caused by pressure induced stress or from fatigue caused by fluctuations of temperature and pressure in the component wall. Under certain stress conditions material creep increases strongly with temperature and decreases with wall thickness. On the other hand fatigue due to temperature induced stress increases with wall thickness. During the design of the component both types of stress are taken into account, leading to an optimum compromise in accordance with the respective design rules. Because the actual plant operation deviates more or less from design conditions, the accumulated material degradation is not proportional to operating time; that is why a regular monitoring of plant operation is recommended. The best way to carry out such monitoring is by continuously operating a data logger together with a data evaluation system. The Lifetime monitoring software system continuously records operating temperatures and pressures around all critical components of a power plant and from that calculate the D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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resulting contributions due to creep and fatigue. Thus the operator is kept well informed about the current status of the plant, especially about the remaining lifetime of the vital components. The mathematical algorithms follow the European standards. The systematic and continuous application of tool reduces the cost for routine maintenance inspections as well as additional tests. Because degradation of component parts is a long-time effect, it is permissible and, in case of malfunction, not avoidable that from time to time component degradation increases
disproportionately.
However,
the
operator
should
keep
in
mind
that
disproportionate degradation increases must be compensated by way of plant operation generating less than proportionate degradation increases, if the planned components lifetimes shall be maintained. Therefore, using SR1 the operator has an instrument suitable for well-aimed influencing the remaining lifetime at his disposal. For example, if the live steam temperature is willingly increased within the admissible range to improve the unit’s heat rate, the corresponding higher creep damage at least partly consumes the free margin possibly accumulated during previous operation, or the planned remaining operation time must be reduced. Analogously, by willingly shortening the start-up time of a boiler – thus saving start-up costs and connecting to the grid faster –increased lifetime consumption due to cyclic fatigue will be recorded. Accordingly the accumulated free margin will be reduced. The respective allowable curves are specific for each component. These curves will be adjusted automatically to the operation pattern recorded in the past. This dynamic adaptation provides the operator with a clear indication on the permissible operations for each monitored component. This type of tools can be employed successfully in many different power plant units either as stand-alone application or in combination with other modules like data reconciliation or optimisation of power plant operation. Normally such systems are designed to run on Windows NT as a client/server system. It includes a specific data management systems as well as a powerful visualisation module. The required data are exchanged with the process control system or with external data management systems via standard interfaces. For system handling and visualisation of D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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calculation results on the customer owned LAN/WAN licence free clients in any number are available.
14.8
Data Management System
The central component of all online systems is the data management system. In annexure XXII a detailed description of the important features of such system is provided. The essential task of this tool is the cyclic import and archiving of measurement values from the control system or from other data sources. Other data sources can be bus systems or online databases. A corresponding interface is provided for each type of data exchange. All other tools installed access this data through an internal interface, evaluate this data and save the results. This tool enables the automatic integration of data to higher time classes. The data is read by default in minute-cycles and integrated internally to 5’-mean values. All the optimisation calculations are done in this time class. Other integration levels are, for example, 15’-values, hourly values, daily values, weekly values, monthly values and yearly values. According to the respective system configuration, these or even other time classes are available. The entire data is saved in the related time-oriented archives. The system has subprograms for visualizing the archived data or for configuring the data management system. The data visualization enables the representation of any time series in diagrams as well as the representation of a point of time in a flow diagram. Diagrams can represent a maximum of 24 data points in up to 6 ordinates. The displayed time period as well as the time class (minute values or daily values, etc) can be selected freely. Along with the chronological display, ordered output curves or x-y-diagrams can also be selected. Along with line charts, bar charts are also possible. Special events or violations of limiting values can be signalled in the flow diagrams through automatic display of texts or through a corresponding colouring.
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14.9
Thermodynamic Cycle Calculation Program – Offline Tool
All the optimisation and evaluation calculations described above require a detailed thermodynamic model of the boiler and of the corresponding power plant process. This model is configured graphically with the help of the Cycle Calculation Program. This can be as offline tool. This tool provides a lot of components of power plants, which not only permit the modelling of the entire water-steam cycle, but also the detailed modelling of the steam generator. Similarly, essential components of the air and flue gas path can also be included in the modelling. Depending on the respective monitoring or optimisation task the required details of the model can be adjusted accordingly. This means that the boiler can be represented by an individual component within the water-steam cycle or it can be constructed from the main components heating surfaces, injections, combustion chamber as well as the connecting pipes. The water-steam cycle itself is constructed from the main components turbine, condenser, pre-heater and pumps as well as the connecting pipes. Especially the turbines are typically modelled as a combination of the individual turbine stages. This tool is a powerful tool to help the Power Plants/define areas of inefficiency component wise and total plant as a whole. The entire plant is first "mapped" by the Software to establish consistency of online data and compare with design parameters of the plant. The outcome of this exercise give a complete mapping of Power Plant configuration including equipment specification into a software that can simulate certain conditions and identify partial mismatches as well as wrong instrumentation display data. The power plant provides the data, which is used to do the mapping of the Power Plant. The Power Plant is mapped based on data input and validate data input by trial runs. This approach is interactive since initial power plant data provided will usually not match due to hidden or known instrumentation errors as well as inaccurate equipment and fuel specification. The objective is to demonstrate more innovative methods to conduct a baseline D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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performance assessment and map the results into software for further analysis and simulation for the benefit of the plant operators. This professional software is a mass and energy balance cycle calculation program – highly integrated into Windows. It is suitable for nearly all-stationary thermodynamic model requests coming out of energy cycles or plant schemes. The mathematical kernel of EBSILON is well known for its extreme convergence stability and for the high calculation velocity (see also annexure XXII). Not at least the last reason for several customers to use software is the user-friendliness which is ensured by 100 % Microsoft-conform, intuitive handling. Therefore it is – for this purpose – the most used software at several small and large companies as nearly a lot of manufacturers and utility companies in the German speaking Europe. Such software program is fully available also in English and French and there are customers in Netherlands, Poland, and Denmark and in China. The modelling is done by using a component library, which in the moment exists of all components as e.g. turbines, heat exchangers, boiler, pumps, generators, gas turbines, combustion chambers, tanks, gasifier, FBC, fuel cell, cooling towers dryer, filters, separators, fans, control elements, calculation modules, text fields, buttons, alarm fields etc. A customer programmable component allows by the use of C-knowledge the fully integration of self generated components. First the cycle is modelled topologically by using the component toolbox and the positioned components are then parameterized. All components are equipped with sets of default values. he sets are taken from a library, which can be modified and enlarged by the user. From this library also total and parts of cycles are eligible. Also a gas turbine library is available. For media properties different tables are available. Fuels (bituminous coal, lignite, gas, oil, hydrogen, biomass etc.) can also be used from a library. Flue gases etc. are nearly unlimited elementary definable or selectable from default compositions. This professional tool is so powerful that in one model also several power plants may be connected by power lines or steam and a district heating system still in a high detail can be calculated in one D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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model in some seconds. The Import and Export of data and results is possible via variety of Excel or ASCII interfaces as via DLL. All adjustments as visualization topics, physical dimensions (or British Units), are components dependent or general (also or fly) eligible. A very comfortable error analysis tool leads the user through this model to the error source. Beside exists a calculable example for every component as an online documentation for general questions. Figure 14-1: Typical mapping of a power plant
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In principle, this software does not restrict the detailing depth of the modelling. The characteristic lines or the characteristic fields for describing the thermodynamic behaviour of the individual components are determined on the basis of the design calculations or by evaluating the measurement values. In this way, the characteristics of the components for the entire load range can be determined. Typical mapping carried out by such typical software is given below (Figure 14-1).
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15.
Benchmarking of Power Plant Operation & Management
15.1
General
Re-organisation of the power industry has progressed and has put pressure on heat and power production cost with the import of electricity from neighboring regions possible. In this context, many power plants have taken up several mid-term programs of efficiency and competitiveness improvement (strategic cost management program). A competitive power generation might only be reached by cost cutting what means technically and cost efficient power and heat generation. In thermal power plants the following subjects are preconditions for this: •
low operation cost
•
low maintenance cost
•
high technical efficiency in plant operation
•
effective management organization
•
compliance with surrounding regulations.
Benchmarking
of
power
plant
involves
development
of
essential
technical
and
organizational elements for the long-term commercial sustainability of the power plant operation.
15.2
Basics of Benchmarking
The competitive energy market in EU demands that power generation companies must have a critical look on their business policy. "Benchmarking" provides a chance to compare a company, a plant or a production unit with another or a "Best Practice"-company, plant or unit, to find out its own ranking in a competitive market. The own position in the competitive market will be given by means of indicators, which will be defined at the beginning of the process.
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Measures for a better economical efficiency of the company / power plant / unit focused on, are to be derived from the results. For example "cost/kWinstalled" is such an indicator in the power sector (Figure 15-1). Figure 15-1: Finding out a position in a competitive market by Benchmarking
What is benchmarking? Why do we need benchmarking?
What?
Comparison of ........ .......... a process or a company with other competing processes or companies with specific indicators (cost, €/kWi in thermal and hydro power plants or WMO in hydro power plants)
Why?
Ranking............. .......... of your own company in the market
Conclusions and development of measures
15.3
Benchmarking of Thermal Power Plants
The total cost will be divided into different groups of cost (Figure 15-2) and then analyzed and compared with other, similar power plants. The greatest attention will turn on the total operating cost. Numerous measures to improve efficiency and production cost have to be elaborated, evaluated, compared and finally best options need to be introduced. This gives the D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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advantage to judge benchmark key indicators versus the background of practical operations. Figure 15-2: In thermal power plants the focus of the analysis is on cost of operation
Total cost €/kWh
Fuel cost €/kWh
Operation €/kWinstalled
Total operating cost €/kWinstalled
Maintenance €/kWinstalled
Capital cost €/kWinstalled
Other €/kWinstalled
Administrative cost €/kWinstalled
15.4
Focus of analysis
Benchmarking Methodology
It is useful to conduct at first an internal and secondly an international Benchmarking to compare these units and to show their ranking compared to the international market. After this analysis the experts can point out cost intensive areas of operation. Measures to realise a cost effective operation of the analyzed power plants will be elaborated in an initial stage and can be suggested to the plants. The benchmarking exercise consists of a pre-phase and additional three project phases (Figure 15-3).
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Output 1.1 Figure 15-3: Phases in a successful Benchmarking process
Development of concept to increase efficiency
Introduction to methodology and selection of subjects to benchmark
Pre-Phase
Data collection
Phase I
Determination of potential for efficiency increase
Phase II
Drawing up of measures and creation of scheme of implementation
Phase III
Implementation
Implementation
Phase IV
In Phase I an extensive and detailed data collection on the subjects to be considered will be performed. This data collection will build the essential basis for all following phases. In the following Phase II the technical and organizational performance will be compared in a way that the determination of potential for efficiency increase will be possible. Following this in a Phase III there will be the focus on drawing up a strategic concept to improve technical efficiency and establish a cost efficient operation. Phase IV encompasses the realization and the implementation of measures and is not part of this proposal.
Pre-Phase
Introduction to the methodology of benchmarking processes
It is very important to get acceptance and support for the Benchmarking process on all levels of power plant, because data acquisition, identification of potential improvements and first of all realization of measures to improve need to be accepted by all stakeholders D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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within the company. Therefore, a team representing top level and working level of Power plant should be created to work on this process. A steering committee is required to take decisions according to the timetable of the project. All parties need to get a general understanding of the process and will be introduced to the methodology of Benchmarking.
Phase I:
Comprehensive technical economical, administrative and organizational data
collection By means of an extensive and detailed data collection in this Phase I the basis for the comparison of technical and organizational performance as well as for the definition of goals and the development of measures in the following phases will be provided (Figure 15-4). Figure 15-4: Overview data collection
Data Data sheets sheets
Other Other(insurance, (insurance,etc.) etc.) Purchasing Purchasing//Materials Materialsmanagement management Organisation Organisation//Processes Processes
AA comprehensive comprehensive data data collection collection ……. ……. 1a. 1a. Fuel Fuel (TPP) (TPP) 1b. 1b. Scheduling Scheduling (HPP) (HPP) 2. 2. Operation Operation 3. 3. Maintenance Maintenance 4. 4. Administration Administration … … is is the the basis basis for for aa comparison comparison of of cost cost for for aa sucessful sucessful benchmarking benchmarking
Employees Employees Cost Cost Technical Technicaldata data Basic Basicdata datasite site
••installed installedcapacity capacity ••number of number ofunits units ••generation generation ••specific specific technical technical features features ••... ...
Reference year: Last year
Data collected and evaluated will include (e.g.): •
fuel supply in TPP
•
process organization (structure, cost, etc.)
•
management organization (hierarchical structure, cost, etc.)
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•
technical and economical data on power generation (operation and maintenance, overhauls, degree of automation, etc.)
•
administrative data (overhead, personnel, etc.).
For a basic year of investigation as well as from following years available data will be taken into account. Total operating cost will be divided into various cost components such as operation cost, maintenance cost and other cost (see chapter 15.3 and Figure 15-2). Maintenance cost themselves will be divided into cost for routine maintenance (cover cost for regular maintenance and other repair expenses) and cost for maintenance projects (cover cost for inspections and scheduled overhauls, cost for individual measures and cost for other measures). Depending on the maintenance cycle annual maintenance cost may vary more or less. It is important to determine a representative mean value for the basic year, preferably the running year. Concentrate on technical issues and consider their economic influence including the following topics: •
Heat and power production efficiency (production equipment efficiency)
•
Heat supply systems efficiency (efficiency of the heat supply infrastructure)
•
Fuel supply efficiency (fuel purchase and storage efficiency)
•
Material and technical supply efficiency (material and technical resources purchase and storage efficiency).
At the end of Phase I the data collected will be presented to the Client and, if required, additional information input from the Client will be discussed.
Phase II:
Determination of potential for efficiency increase
The methodology of Phase II for thermal power and heat generating plants is described below. The results where an efficiency increase seems to be successful and feasible in short term as well as in long-term measures will be presented to the Client at the end of Phase II.
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The data collected in Phase I will be evaluated and key performance indicators and sitespecific correction factors will be elaborated and defined. The site-specific correction factors will be discussed with the responsible power plant personnel. Correction factors are essential to compare power plants. They will be introduced to adjust location and type of a power plant. Site correction factors e.g. consider different levels of wages, different annual working hours or different cost of materials. Correction factors for technical differences will be determined in a multi-step elaboration. Important parameters of the power plant will be determined; by analysis and discussions with the local experts the correction factors will be set up. In addition to general technical differences, other peculiarities having influence on the power plant cost will be considered. Based on the data a comparable gap will be defined, including the international comparable gaps for both units. Results of the comparison will show the power plant’s / unit’s ranking with respect to the category it is operating in. This comparison will be made with international power stations. By comparison with the "Best-Practice" power plants / units savings potential for the power generation units under consideration will be determined and the data assessment of the current situation will allow the definition and suggestion of cost saving measures in Phase III. The collected but non-corrected data do not show differences in cost or efficiency against other power plants. Only the introduction of correction factors allows the demonstration of advantages or disadvantages of the power plant considered versus international power plants. In Figure 15-5 the potential for improvements worth striving for is outlined.
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Output 1.1 Figure 15-5: Evaluation of correction factors in thermal power plants Data comparison Data collection
Data correction Benchmark
Definition of goals
Development of measures
Power Plant 1
Realisation of measures
Power Plant 2 Fuel
Fuel
Operation Power generating costs
To compare power plants, corrective factors need to be applied to make adjustments for sites / power plants types.
Operation Power generating costs
Capital
Capital
Administration
Administration
Figure 15-6: The value of a benchmarking project is not the contest but performance improvement opportunities
disadvantage versus best practise PP
PP 1 non corrected data
advantages versus best practise PP
corrections
improvements worth striving for
PP 1 potential corrected data for improvements
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Phase III:
Drawing up of measures and creation of scheme of implementation
During Phase III first draft measures are drawn up and suggested in the process. The implementation
of
these
measures
will
be
schematically
described.
Technical,
organizational and economic measures to increase the efficiency and saving costs will be developed, suggested and discussed with the management of the power plant branch management and the company management. Points of start, where first measures could be introduced will be found out. The measures elaborated and the implementation scheme will be presented to the Client. After the specific cost reduction measures for the thermal power plants are identified and the required level of investigation for each measure is known, the Consultant will prepare a separate tender for the related services.
15.5
Project Organization
A successful co-operation between Consultant’s and plant's experts is a precondition to elaborate immediate measures, which will lead to comparatively quick results. It is required to establish one project team guided by a steering committee. Plant engineers will be the local engineering partners to the team. The responsible plant and administrative personnel will join the teams, each for the different topics (typical organization (Figure 15-7), and support the benchmarking team. By this the detailed knowledge on the thermal heat and power generating plants is going to be combined with external experience in efficient power plant operation in the liberalized energy market according to the state of the art. To ensure an overall evaluation concerning administrative, management and economic assets, experts will closely work together, exchange their information and discuss the analyses with their power plant's counterparts.
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Output 1.1 Figure 15-7: Typical project organization for a benchmarking process
Steering Steering Committee Committee Member Member of of the the Board Board Power Power Plant Plant Director Director Evonik Evonik Energy Energy Services Services
Project Project Director Director N. N. N. N. (Power (Power Plant) Plant) N. N. N. N. (Evonik (Evonik Energy Energy Services) Services)
Core Core Team Team Production Production
Core Core Team Team Maintenance Maintenance
Core Core Team Team Others Others
N. N. N. N. (Power (Power Plant) Plant) … …
N. N. N. N. (Power (Power Plant) Plant) … …
N. N. N. N. (Power (Power Plant) Plant) … …
N. N. N. N. (Evonik (Evonik Energy Energy Services) Services)
N. N. N. N. (Evonik (Evonik Energy Energy Services) Services)
N. N. N. N. (Evonik (Evonik Energy Energy Services) Services)
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16.
Energy Audit – Situation in the EU respectively Germany
16.1
Status
In the EU are a wide-spread set of directives (to be transposed into national law) targeting the energy sector. There are directives for: •
emission limits (large combustion directive)
•
emission trading
•
utilisation of water (water framework)
•
emission ceiling
•
co-generation of heat and power
•
use of renewables
•
efficiency of transport (vehicles)
•
efficiency of households
But there are no regulations for the efficiency of electric power generation. In the past in the EU we had discussions to implement regulations, but at the end the conclusion was that market-driven mechanism are more effective. This position was supported by the fact that the electric power generation in the EU is the most efficient worldwide. In the following one will explain why and how this impressive result has been achieved. As well as it will be shown how the efficiency is monitored. This offers the possibility to build a bridge for this experience referring the energy auditing procedure to the Indian situation. A simple key reason is: the more efficient a power plant works the most economic it is!
Electric Power Market This statement is outcome of a development lasting for several decades; i.e. nonliberalised and competitive markets. For the pre-competitive area the driving force was – at the end – high cost of the domestic primary resources and/or the lack of domestic primary resources, which have to be bought from elsewhere. Consequence of this experience was a well established culture in improving the technologies needed to achieve high efficiency figures. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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With the opening of the electricity market for competition this culture and state of the art of technology was an excellent basis for the challenges out of competition. The increasing concern about climate change and the necessity to improve efficiency and reduce emissions on one side and the explosion of fuel prices for fossil primary resources had enforced the pressure for further improvements.
Practice Based on the given constraints - presented above - the practical use and application respectively installed technologies will be described.
Philosophy The existing philosophy is determined by the competition driven constraint to be market feasible. Market feasibility means to do anything improving the competitiveness. The competitiveness is a function of •
well established customer relations in terms of prices and services,
•
well positioned power fleet consisting of
base, intermediate and peak load plants and of
balanced fuel portfolio
•
state of the art technology
•
skilled staff in mastering technology & market requirements as pre-requisite
In the following the major focus will be given to the technology sector respectively their solutions.
Technical Solutions The efficient operation is determined by an appropriate design of the plant and its components, realised quality and the corresponding monitoring tools. The key element for pursuing the efficiency of power plant operation is the instrumentation and control system (I&C). By means of the I&C system the staff is able to follow the timely behaviour of key figures defining the efficiency as the case may be the performance.
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The accuracy of the measurement devices does not reach the accuracy of the specific installations for the final approval tests, but it allows a trend analysis of selected operation plant parameters. State of the art plant process control systems are delivering the overall plant efficiency as well as the efficiency of systems and even components. Examples are the effectiveness of •
feed water pre-heating system indicators are the heat transfer factor, the terminal temperature difference and the temperature increase of each high-pressure pre-heater
•
heat transfer of the boiler tubes indicators are the heat transfer factors of each bundle significantly influenced by ash deposits to be removed by the soot blowers
•
air pre-heater indicators are the pressure loss and the leakage of the air pre-heater
•
condenser indicator is the heat transfer factor of the condenser
Specific systems are available supporting the process control system. The goal is to facilitate the complex optimisation process with often contrary influence factors. Based on the process control system the optimisation process will be guided ensuring both optimal and safe operation (see Figure 16-1). In addition to this the minimization of outages, shortening scheduled overhauls and increasing efficiency by detailed planed outages are very important from environmental point of view.
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Indo German Energy Programme Report Output 1.1 Figure 16-1: Performance monitoring of power stations
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Experience and Application IT-systems which provide the above mentioned monitoring functions are used in many German power plant units. The results of the technical and economical evaluation of the power plant are updated every 5 minutes and saved in a data historian. Thus, the trend of the performance of each unit can be monitored on any time scale. Hence plant components are evaluated online and planning data for condition based maintenance are provided. Furthermore optimum modes of operation from economic and ecological aspects are suggested, the impact of different, changing environmental conditions is evaluated and last but not least the unit's operation is optimized coming along with an efficiency enhancement. In addition to the efficient operation the role of the process control system is also the provide information concerning the life time of components and hints necessary for maintenance to be done. Figure 16-2 and Figure 16-3 give an overview the plant monitoring system is shown: •
terminal output (Figure 16-2: 151.5 MW)
•
unit efficiency (Figure 16-2: 42.28 %)
•
boiler efficiency (Figure 16-2: 94.52 %)
•
specific heat consumption (Figure 16-2: 2,184 kJ/kWh)
•
auxiliary consumption (Figure 16-2: 6.58 MW)
Losses are calculated in monetary value (here in DM) •
heating surface, economizer/reheater (Figure 16-2: 62 DM/h)
•
reheat spray flow (Figure 16-2: 19 DM/h)
•
leakage in economizer (Figure 16-2: 25 DM/h)
•
live steam parameter (Figure 16-2: 4 DM/h)
•
condenser pressure (Figure 16-2: 8 DM/h)
•
pre-heater (Figure 16-2: 10 DM/h)
•
current consumption (Figure 16-2: 0 DM/h)
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Output 1.1 Figure 16-2: Screenshot 1 of the plant monitoring system (Evonik power plant)
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Output 1.1 Figure 16-3: Screenshot 2 of the plant monitoring system (Evonik power plant)
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In the following Figure 16-4 to Figure 16-12 in more detail a lignite power station is described as an example. Figure 16-4: Unit overview Figure 16-5: Combustion freeboard including burners Figure 16-6: Soot blowing system Figure 16-7: Soot blowing system and boiler reforming data Figure 16-8: Boiler scheme Figure 16-9: Operation regime of soot blowing Figure 16-10:
Thermodynamic scheme
Figure 16-11:
Boiler air supply system, burner and overhead air
Figure 16-12:
Combustion Air Control
Conclusions The general conclusion is that in spite of the fact that there are no legal obligations the efficiency culture is part of any power plant operation. Basis is the plant design and process control system. An indirect indicator for energy auditing are the performance indicators for availability respectively unavailability. Finally one can quote that energy auditing is essential part of an efficient electric power generation in respecting the limitations of laws of nature and coping with the challenge of a competitive market.
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Indo German Energy Programme Report Output 1.1 Figure 16-4: Unit overview
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Indo German Energy Programme Report Output 1.1 Figure 16-5: Combustion freeboard including burners
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Indo German Energy Programme Report Output 1.1 Figure 16-6: Soot blowing system
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Indo German Energy Programme Report Output 1.1 Figure 16-7: Soot blowing system and boiler reforming data
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Indo German Energy Programme Report Output 1.1 Figure 16-8: Boiler scheme
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Indo German Energy Programme Report Output 1.1 Figure 16-9: Operation regime of soot blowing
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Indo German Energy Programme Report Output 1.1 Figure 16-10: Thermodynamic scheme
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Indo German Energy Programme Report Output 1.1 Figure 16-11: Boiler air supply system, burner and overhead air
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Indo German Energy Programme Report Output 1.1 Figure 16-12: Combustion Air Control
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17. Overview on Regulations, Guidelines Efficiency/Plant Performance Best practice
System part
Indications
Source
Page
Remarks
items for the analysis
Fuel
Fuel analysis
DIN 51700
Analysis of solid fuels
DIN 51701-2
Carrying out the analysis
Volatile elements Hardgrove
Thermal
Index
efficiency
13. BImSchV
Sulphur
Water pollution
LCP-Directive,
Silicon
LCP-Directive,
13. BImSchV
13
DIN 51724-1
2 to 6
DIN 51724-2
2 to 5
Co-
LCP-Directive,
combustion &
13. BImSchV
refuse derived
8
Determination of sulphur
amount
Determination of sulphur in
the fuel
13
fuels Calcium Ash
Technology for
Primary
LCP-Directive,
avoiding
measurements
13. BImSchV
sulphur
for avoidance
emissions
Determination of the ash 109
content
Carbon
proportion Coal supply
VGB M 211e Use of lowsulphur fuels
Boiler
Steam boiler
Flow -through
Power plant coal feeding
LCP-Directive, 13. BImSchV
109
VGB R 450 L
10
boiler / drum
Guideline for feed water,
boiler (water
boiler water and steam quality
processing) Water / vapour
Interactions
VGB R 450 L
13 - 16
circulation Evaporator Combustion
VGB M 224
chamber Superheater Intermediate heating heating
surfaces Accumulator
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Best practice
System part
Indications
Source
Page
Remarks
items for the analysis Hot components Mills
VGB R 123 C/2.9e VGB M 213
Coal dust measurements with the pendular zero-
probe coal milling plants Separators
Temperature
VGB R 200
77
measurement
GW vapour deposition and disconnection is to be
behind
allowed
separator Coal dust
VGB R 108
Fire protection in the power
bunker
plant TRBS 2152
Assessment of the danger of explosion
Burner Deashing
VGB R 201e
Directive on and operation
Purification
VGB R 313e
Internal cleaning of
VGB M 221
waterpipe steam
of deashing plants
generators. Process-
engineering influences on the cleaning of heating surfaces and optimisation of use Combustion conduct
Firing
Combustion
modification
LCP-Directive, 13. BImSchV
97
VGB R 200
Dimensioning and operation of power plant firings
VGB TW 216
Primary measurements for the NOx reduction of dust firings for mineral coal
Reduction of
LCP-Directive,
excess air
13. BImSchV
Sorbens -
LCP-Directive,
injection
13. BImSchV
Sorbens -
LCP-Directive,
Injection for
13. BImSchV
140 " 125 to 127
dry flue gas
127 to 129
conduct Reduced air
LCP-Directive,
preheating
13. BImSchV
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Best practice
System part
Indications
Source
Page
Remarks
items for the analysis Fresh
air
ventilator
Maximum
KWS Training
pressure
book no. 8
104
increase Induced draft
KWS Training Ventilator
book no. 8
design
VGB R 102
104 Order of ventilators for thermal power plants
Pumps Air Preheater
(air flow rate) Heavy metals
LCP-Directive, 13. BImSchV Dust-avoiding
LCP-Directive,
techniques
13. BImSchV
Electrostatic
LCP-Directive,
Electrostatic
LCP-Directive,
Fabric filters
LCP-Directive,
(bag filters)
13. BImSchV
Centrifuge
LCP-Directive,
filter
wet separators
13. BImSchV 13. BImSchV
separator
13. BImSchV
Wet separator
LCP-Directive,
VGB R 103e
13. BImSchV
10 98 99 101 101 104 105 to108
Turbine
Types of
Condensing
Vapour purity/
construction
turbine/ back-
conditioning
pressure turbine
Directive on monitoring and protection of steam turbines
VGB R 105e
The thermal behaviour of steam turbines refer to IEC Technical Specification TS 61370 (page 12)
Turbine
VGB R 504e
Test of big forgings and pressure pieces
Turbine
VGB R 127
operation
VGB Directive on turbine drives
VGB M 101
Rec. on how to avoid damages at steam turbo units
VGB M 114
Efficiency changes at steam turbines
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Best practice
System part
Indications
Source
Page
Remarks
items for the analysis Fitting
VGB R 107
Order and design of fittings
tappings
in thermal power plants
Preheater Piping
VGB R 503e
Directive on internal pipings of the turbo unit
Connecting
VGB R 505e
Types of
VGB R 450 Le
elements Condenser
Directive on screws in
high-temperature areas Directive on the quality of
construction
feed water, boiler water and steam for copper materials VGB R 106e
Directive on condensators
and other heat exchangers, part A copper alloys
VGB R 113Le
Directive on condensators
and other heat exchangers, stainless steel
VGB R 114Le
Directive on condensators
and other heat exchangers, Ti material
Cleanability Flue gas
cleaning
Condensation system
DeNOx
VGB R 305
Directive on planning and
ordering of installations for the reduction of NOx emissions
E - filter
Emission of
LCP-Directive,
particulate
13. BImSchV
matter
VGB R 301
9 Planning and ordering of
installations for the reduction of dust emissions
Heavy metals
LCP-Directive,
NOx emission
LCP-Directive,
Wet scrubber
LCP-Directive,
13. BImSchV 13. BImSchV
13. BImSchV Types of
LCP-Directive,
absorbers
13. BImSchV
Sea water
LCP-Directive,
scrubber
13. BImSchV
10 11 111 117 119
Magnesium wet scrubber
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Best practice
System part
Indications
Source
Page
Remarks
items for the analysis Ammonia wet scrubber
121
Spray dry scrubber
121 to 124
Electrical
Volumetric
VGB R 123
and
flow
Collection of recommendations on the
control
measurements
control technology
technology
Pressure
measurements Temperature measurements Control
VGB R 170 BO-
Design standards for
technology
B6e
instrumentation and
VGB R170 A1e
Measures for the avoidance
control equipment and control of control technology failures Technical unit
VGB R 117
protection Auxiliary
VGB R161
Material for
VGB R 109
pressure-
d+e
power
Technical unit protection for thermal power plants Auxiliary power and
protection of auxiliary power in power plants
General
carrying devices
Availability
VGB Rv 808
Availability of thermal
Losses
DIN - EN
Determination of radiation
power plants 12952 - 15
losses
DIN - EN
General losses
12952 - 11
VGB R 123C Dangers
Losses in start-up and
shut-down processes
TRBS 2152,
Assessment of the danger
TRBS 2152-1,
of explosion
TRBS 2152-2 TRBS 2141,
Assessment of the danger
TRBS 2141-1
of steam and pressure
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18.
Example: Computerized Plant and Energy Management Systems at the Evonik Steag Voerde Power Plant
Evonik Steag Voerde Power Plant has total installed capacity of 2,120 MW. Hard coal is used as fuel. The total power generation is about 10 billion kWh/a The plant has adopted the latest computerized management systems for effective operation & maintenance of the power plants and improving the performance of the unit. The following computerized systems have been adopted •
Energy Management system
•
Plant management system.
Energy Management System The energy management system evaluates the existing on line measured data and recognizes the potential for optimization by assessing the processes and components. The system continuously assesses the plant operation, comparing it with the current calculated optimum, so that the unit can be run at maximum efficiency. The energy management system estimates the potential for optimization and even minimal reduction in operating efficiency is identified and pinpointed.
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The energy management system is based on a three-tiered concept – evaluation, Optimization and forecast for cost relevant power plant sections. All results are evaluated at cost so that the effects of different operating parameters on cost can be directly compared. •
Computation of ratios and key figures such as efficiencies, electric energy from cogeneration, start up cost etc.
•
Component evaluation (steam generator, steam water cycle, condenser, pumps, flue gas circuit etc)
•
Optimizing (soot blowing, gas turbine compressor washing etc)
•
Fore cast (unit efficiency, maximum unit output etc)
Plant Management System Integrated plant management system, makes all operating processes rational and transparent right from shift planning to component use. The plant management system helps the plant team to detect weak spots early and optimize operating procedures. In addition it gives up to date information with all organizational, technical & commercial details. Based on master data and timely operating data acquisition, the plant management system supports the plant team in the following areas of operation: •
Minimizing of the administrative effort invested in plant management
•
Efficient job scheduling and control along with performance recording and documentation
•
Cost optimized shift planning with integral payroll data acquisition
•
Optimizing and reporting of the use of operating supplies and the stocks of supplies
•
Daily cost status, availability data and official requirements compliance information
•
Assurance of compliance with processing and quality standards
•
Subject related control of information flow and authorizations
•
Dependable safety disconnection process with conflict check and switch in warning
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19.
Latest (state of the art) technologies and status
19.1
Technology Perspectives – Availability vs. State of the Art
The technical development is a permanent process and the key attitude is the requirement for patience and perseverance in order to accept the un-evitable errors, to sustain the motivation for searching in new solutions and convince the financing instances to spend money. With these general remarks in mind one can quote that there is always a gap between state of the art and the commercial available technology. One characteristic feature of a commercial available technology is the market viability, i.e. several suppliers offer a technology at competitive conditions. The aspects of local affects for the technologies are of minor relevance in a global world. As a conclusion it is to state clear that the 600°C technology is fully commercial available. There are several suppliers of the raw materials – forging, casting, etc., as well as there are several manufactures able to master the specific requirements of the austenitic materials. At the end there is enough experience driven by some front-runners in order to know what kind of difficulties can occur or preventive measures are reasonable. Parallel to the placing orders, erecting of plants and commissioning of new plants an intensive consolidation programme is launched. It's key purpose is to broaden the range of materials, to gain better understanding of the design specifics and to open the horizon for new ideas.
19.2
Atmospheric Fluidized Bed Firing System
The fluidized bed firing is a firing that takes place in a fluidized bed made up of sand, fuel reduced to small particles (fuel portion of about 2 %) and hot combustion air (primary air through the nozzle bottom). The fuel is kept hovering above the nozzle bed and fluidizes. The small fuel particles have a large surface enabling a thorough burnout. The strong eddying flow results in a most favorable impulse and heat exchange so that a constant temperature is kept up in the fluidized bed. The combustion temperature is determined by the fuel mass flow supplied. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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The temperature is adjusted such that the generation of detrimental gases (CO, NOx) is as low as possible. With fluidized bed firing it is possible to keep the nitrogen oxide emissions low as it allows to operate at a relatively low combustion temperature without temperature peaks. We distinguish between the stationary and the circulating fluidized bed: •
In case of a stationary fluidized bed the ash discharged from the combustion chamber is removed.
•
The circulating fluidized bed is designed with a cyclone downstream of the combustion chamber which serves to return the discharged sand with a certain portion of ash and unburned fuel back into the combustion chamber.
For fluidized bed firing in coal-fired power plants the coal is charged with lime to bind the sulphur contained in the coal. With today's state of technology a power enhancement to 1,000 MWth is feasible with circulating fluidized bed plants and this is currently being implemented in Poland. The principal field of application for atmospheric fluidized bed plants is considered to be the combined production of electric current and heat – i.e. combined heating and power plants. The limitation of the power capacity is of rather low importance here. In addition, this design permits to utilize a broad scope of fuels ranging from coal via biomass through to residual materials.
19.3
Pressurized Fluidized Bed Firing System
Similar to the development of the gas and steam turbine plants (combined cycle turbine facilities) fuelled with natural gas, in the 1950's there was a desire to implement also for power plants fuelled with hard coal such cogeneration power plants consisting of a gas turbine process and a steam turbine process to reach maximum plant efficiency levels. The first large-scale plants with a pressurized fluidized bed firing system were then commissioned in the 1980's. For these systems, the conventional combustion chamber of D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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a gas turbine plant was replaced by a combustion chamber fuelled with coal. As the combustion chamber needs to be operated under increased pressure (approximately 12 bar – 16 bar) to obtain a large efficiency, it became necessary to accommodate it in a cylindrical or spherical pressure vessel (diameter approx. 22 m for a projected 300 MW plant). Based on the pressurized fluidized bed firing system, various testing facilities and pilot plants were erected: •
Testing power plant Grimethorpe, Great Britain
•
Pilot power plant TIDD Ohio, USA
•
Pilot power plant Värtan, Stockholm, Sweden
•
Pilot power plant Escatron, Spain
•
Combined heating and power plant Stadtwerke (public utility company of) Cottbus, Germany
Efficiency The operating experience gained up to date has shown that the pressurized fluidized bed firing has a limited efficiency potential. Owing to the combustion chamber temperature being limited in the fluidized bed to 850 – 900°C, the upper process temperature determining the efficiency is restricted such that maximum plant efficiency values of a mere 45 % can be expected. In practical operation, it was possible to reach an efficiency of about 42 %. Apart from the limited efficiency potential, the experience gained in practical operation has particularly lead to the fact that pressurized fluidized bed firing became less important in modern power plant technology world-wide. Coal supply In a pressurized steam generator the fuel needs to be fed in either via a lockage system or in the form of a coal/water suspension. Drawbacks: •
Considerable wear at the lock fittings has continually entailed system malfunctions.
•
To feed the coal without difficulty it had to be dried to a water content of
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< 2 % involving a high energetic expenditure. •
To prevent explosions in the lock chambers, the locking process had to be laboriously carried out under an inert gas atmosphere.
•
When supplied as a coal/water suspension the slurry pumps used for the process had an inadequate service life.
De-ashing system The ash produced in the coal firing process needs to be discharged from a pressurised pressure vessel via a lockage system. Drawbacks: •
Considerable wear in the pneumatically operated conveying lines
•
Frequent failures of the lock fittings at an ash temperature of 850 °C
Steam generator To provide a combined process, the steam generator is accommodated in a pressure vessel. Drawbacks: •
Poor accessibility for maintenance work
•
Restricted possibility to timely detect malfunctions in the steam generator area.
Purification of the flue gas and gas turbine The flue gases are first cleaned by passing through a cyclone cascade and subsequently further cleaned by means of a ceramic hot gas filter, before they are fed into the gas turbine. Drawbacks: •
Fractures of the ceramic filter cartridges resulted in frequent plant standstills.
•
High residual dust content led to a destruction of the gas turbine blading.
•
Exhaust gases from the gas turbine require another purification downstream of the gas turbine in order to observe the currently applicable dust emission
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levels.
19.4
Gasification of Coal (IGCC)
Another power plant process for the use of coal in combined gas and steam turbine processes is provided by the gasification of coal and the subsequent combustion of the produced synthetic coal gas in a downstream gas and steam turbine plant (IGCC proc-ess or Integrated Gasification Combined Cycle). In the gasifier proper, which is operated at a high gasside pressure of 40 bar, the coal is mostly converted with pure oxygen to become a synthesis gas predominantly consisting of hydrogen and carbon monoxide. The carbon monoxide portion is converted into carbon dioxide and additional hydrogen by adding water steam in a so-called shift reaction. The hydrogen can then be used for power generation in the gas turbine plant of the combined power plant downstream of the coal gasification. In this process the hot flue gases of the gas turbine are fed into the integrated water/steam circulation via a heat-recovery steam generator. Compared to other power plant designs the IGCC technology has the advantage that the carbon dioxide present in the synthesis gas can favorably be precipitated from the process at relatively high pressure, for instance by a Rectisol flue-gas purification process. In the long run, after developing underground storage deposits, this could lead to an implementation of a CO2-poor power plant technology on a coal basis. Furthermore, it is possible to produce synthetic fuels and chemicals from the synthesis gas, which provides new attractive application options for this process in the long term. Since the 1980s, several pilot plants with entrained-phase gasification and fluidized bed gasification have been operated for testing purposes. Today, various processes are offered by Shell, UHDE, General Electric and Siemens. The following pilot plants have since been erected for power generation:
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•
Pilot plant Cool Water, USA, operation 1984 – 1998
•
Pilot plant Buggenum, NL, currently operating
•
Pilot plant Puertollanno, SP, currently operating
Although the IGCC technology has a high development potential, an economically reasonable application in large-scale plants could not be realised to date. The service experiences available today show that there is a continued need for development in the fields of the gas turbine, the hot-gas purification as well as the coal supply and the slag discharge. If ultimately a reliable plant operation with a high availability and a high efficiency is to be implemented, it will be necessary to further optimise the plant components currently being developed and to have them tested in pilot plants. In Germany a first pilot plant is envisaged to be commissioned in 2014. After several years of testing operation a reliable commercial plant engineering will then possibly be available around the year 2020.
19.5
Turbulent Pulverised-Coal Burner
In above comparison of the pulverised coal firing with other firing types and coal conversion methods, it has been demonstrated that none of the techniques that are comparable to pulverised coal firing is able to exceed a thermal power of 1,000 MW. Accordingly, the thermal power required ranging far above 2,000 MW can be generated only when using a pulverised coal firing process. Pulverised coal preparation In the power generation industry, fan mills have become widely accepted for the preparation of brown coal and bowl mills have established themselves for the preparation of hard coal. Essentially, the required preparation comprises the crushing (surface-area amplification), drying and screening. The screen sorting of pulverised coal formerly performed with static separators is increasingly since the 1990's being effected using speed-controlled dynamic separators as shown in Figure 19-1. D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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Output 1.1 Figure 19-1: Bowl mill with dynamic separator
Burner description In an almost 100-year development of the pulverized coal burners the so-called jet and swirl stage burners (DS burners) have established themselves; they differ only marginally in terms of burnout and emissions. The swirl stage burners intended of the power plant are arranged at two opposing combustion chamber walls (in a height-offset arrangement, 3 or 2 levels). Each burner consists of a core air tube surrounded by several concentric tubes (refer to Figure 19-2). accommodated in the core air tube there is the ignition and supporting burner (designed as an oil firing), which – only for start-up and supporting load operation is driven forward to the operating position near the combustion chamber wall; usually the ignition and supporting burner is kept in a retracted position in order to have it as little as possible exposed to the heat radiated in the combustion chamber so that the core air tube will require relatively few cooling air. Figure 19-2: Pulverised coal burner (with out ignition and supporting burner)
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The first concentric annular space surrounding the core air tube serves for conveying the pulverized coal / air mixture and is also designated as primary air. For a stable, complete and environmentally friendly combustion, the pulverized coal is to flow into the combustion chamber most uniformly distributed across the burner ring cross section. This is supported by a symmetrical line arrangement, a sufficient primary air velocity and a ring gear at the outer pulverized-coal ring main. The ring gear serves not only to stabilize the flame but also to disintegrate the chunks of pulverized coal. To have all chunks get reached and contacted by the ring gear, the annular flow of pulverized coal around the ring gear is given a slight angular momentum by swirling blades.
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The burner ring cross sections serve for a staged allocation of the combustion air and they can provide their through-flowing air not only with a variable impulse (velocity and volume) but also with different swirl stages. The different swirl stages can be generated by adjustable and fixed swirl blades and supplement the required flame stability, if the stability produced by the ring gear is not sufficient. The flame stability is essentially determined by the portion of volatiles in the coal and the comminution, the fine grain portion of the pulverised coal. The portion of unburned carbon in the electrostatic precipitator ash is required to range below 5%, so that the ash can be further utilised in the cement industry. This is primarily reached by a low coarse grain portion in the pulverised coal, which in turn results from the high grinding performance and a strict grain-size screening in the separator. Turbulent burner aspects: With the NOx primary measures (see BAT measures) harmonised accordingly, it is possible for today's use of "steamcoal" from South Africa or Colombia to reach nitrogen oxide concentrations ranging between 400 mg/Nm³ and 500 mg/Nm³ in the flue gas at the discharge end of the radiation chamber (in front of the bulkhead). Here, the excess air may fluctuate around the Lambda value 1.15 and the unburned matter in the electrostatic precipitator ash can be kept well below 5 % when run at the "optimum operation point". We have explained and commented on the NOx primary measures relating to the BAT measures demonstrating that these requirements are fulfilled for the swirl stage burners. Consequently, today's best available technology is the pulverized coal technology.
19.6
Supercritical Technology
Supercritical (SC) and ultra-supercritical (USC) power plants operate at higher temperatures and greater steam pressures than conventional systems. They require less coal per megawatt-hour, leading to lower emissions per megawatt (including carbon dioxide and mercury), and lower fuel costs per megawatt, leading to higher efficiency and lower fuel costs.
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19.7
Six Sigma Concept
Six Sigma is a powerful data driven, customer focused management methodology that delivers validated improvements in profitability and productivity. Six Sigma implementation will guide organization to: •
improve Customer Satisfaction
•
Increase Profitability
•
Increase Productivity
In most companies today, the cost of poor quality represents 20 % to 30 % of total revenues. The Six Sigma approach implements the proven methodologies for minimizing these costs while reaching world-class quality levels by focusing on breakthrough performance (improvements of 50% or more). For more details on technological perspectives, please refer the following Annexures XIII to XX. Annexure XIII
IGCC technology
Annexure XIV
Supercritical and ultra super critical technology
Annexure XV
CFBC technology
Annexure XVI
Six sigma process
Annexure XVII
PFBC technology
Annexure XVIII
Advanced Technologies of Preventive Maintenance for Thermal Power Plants-write up by Hitachi
Annexure XIX
Oxyfuel technology for fossil fuel-fired power plants – Dresden University of Technology, Germany
Annexure XX
Results of oxy-fuel combustion for power plants- Dresden University of Technology, Germany
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20.
Operating Efficiency of EU Power Plants and Efforts initiated for Improvement
The efficiency of both electricity, and combined electricity and heat production from conventional thermal power plants improved steadily between 1990 and 2004. This was due to the closure of old inefficient plants, improvements in existing technologies and the installation of new, more efficient technologies, often combined with a switch from coal power plants to more efficient combined cycle gas-turbines. This trend is expected to continue in the future. However, the rapid growth in fossil-fuel based electricity production outweighs some of the environmental benefits of the efficiency improvements.
20.1
Rationale
The majority of thermal generation is produced using fossil fuels with associated environmental impacts such as greenhouse gas emissions, but can also include biomass, wastes and geothermal. Whilst the level of environmental impact depends upon factors such as the particular type of fuel and the extent to which abatement technologies are used, all else being equal, the greater the efficiency the lower the environmental impact for each unit of electricity produced. Annexure XXI shows the actual efficiency of thermal power plants in Europe, efficiency improvement over a period of time (paper published by European Environmental Agency) and corrective actions taken for improvement.
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21.
Best Practices Applicable to Indian Scenario
The following best practices which can be applicable are discussed in this section:
21.1
•
Online monitoring system
•
Statistical process control for fault detection
•
Maintenance management system
•
Pooling of inventories
•
Benchmarking of component efficiencies
•
Training including simulator training
Online monitoring System
This system is now gaining wide popularity and being used for all new power plants and also being introduced during retrofit of existing systems. The details of this system is given in annexure XXII.
21.2
Statistical Process Control Process Detection
Statistical Process Control (SPC) is an effective method of monitoring a process through the use of control charts. Control charts enable the use of objective criteria for distinguishing background variation from events of significance based on statistical techniques. Much of its power lies in the ability to monitor both process centre and its variation about that centre. The details are described in annexure XXIII.
21.3
Simulator Training on Power Plant Operation
Simulator training is the best option now available to power plants, which gives the feeling of operating a real Power Plant without incurring any generation loss or damaging any plant equipments. Simulator includes advanced training tools and features, which are as important as the D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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simulator itself in successfully achieving training goals. By integrating these tools into the simulators, which delivers not only training simulators but comprehensive training "systems". As a result, operator training becomes significantly more productive, and the need for intensive instructor involvement is minimized. The detailed write up on the simulator is given in annexure XXIV.
21.4
Maintenance Management Systems
The Maintenance Management Systems is a part of Integral Plant Management aided by sophisticated software. These systems are very popular in Europe and have significant potential of applications in developing countries. The details of such system are given in annexure XXV.
21.5
Benchmarking Practices
The benchmarking practices are described in chapter 15.
D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
Indo German Energy Programme Report
Page
168 of 168
Date
28.09.2008
Output 1.1
22.
Miscellaneous
The report provides the brief write up on the following •
Monitoring and controlling of power plants (refer to annexure XXVI)
•
Maintenance practices (refer to annexure XXVII)
•
Sizing criteria of thermal power plants (refer to annexure XXVIII)
•
Stores inventory and procurement systems (refer to annexure XXIX)
•
Key operating parameters of power station (refer to chapter 11)
D:\Guptha\Steag\GTZ\Deliverables Finals\NEW IGEN Output 1.1 Report 2008 09 29.doc
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