Management Of Thermal Pppp

Management of Thermal Power Plant Performance Parameters

Dr. K.C. Yadav, AVP, Noida Technical Training Center

Learning Agenda 









Identification and analysis of input parameters as; Uncontrollable Semi-controllable Controllable Managerial aspect of thermal power plant performance parameters Estimation of energy efficiency parameters i.e. boiler efficiency, THR, UHR and SHR Determination of inevitable effect on performance parameters under design specified operating parameters Preparation of guidance message to the input material managers and operation managers 2

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Need 





Performance of Indian Thermal Power Units has been very poor due to; Wide variation in input (fuel, air and water) parameters than that of the design Inadequate appreciation and understanding of suitably modifying/changing the operating parameters to accommodate the uncontrollable input parameters Lack of managerial will to prioritize performance parameters in sequence of human safety, equipments’ life, energy/exergy efficiency and availability. 3

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Need The need existed; 



To analyze the variation in input parameters and their adverse effect on thermal power plant performance parameters and to modify operating parameters of various power plant process equipments to minimize the adverse effect on performance parameters To promote performance management system to keep vigil over cause and effect relationship of all processes at micro level for the achievement of most optimized values of performance control parameters even when input parameters are significantly different from the design prescribed values 4

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Problem Definition Loss of performance due to variation in input parameters is required to be determined distinctly as inevitable and avoidable so that the improvement efforts can be focused on avoidable loss only

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Objective and Issues Involved 



Objective of the study is based on basic issues of national growth, advancement of status of the citizens, internal / external security, safety of men / material and environmental protection, which depends upon electricity at large Quality power to all at competitive price

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Objective

   

To manage most optimized values of thermal power plant operating parameters in accordance with variation in uncontrollable input parameters, which control; Electricity availability parameters Energy efficiency parameters Equipments’ life parameters Human safety (pollution) parameters

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Issues Involved   

 

 

Large population and population growth High National economic growth rate Growing electricity demand and gap between the demand and supply Increasing coal and electricity tariff Life deterioration of the power plant process equipments Safety of the power personnel Environmental protection 8

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Efforts Rely Upon 

   



Fundamental research, renovation, modernization, retrofitting etc of the process equipments True representative sample analysis Accuracy of the measurements Process superiority of the equipments Proper site selection, plant layout, engineering, procurement, construction, commissioning and testing Awareness of design specified standards of operation and maintenance practices 9

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Gaps

  

Optimization centered integrated approach of managing operating parameters to accommodate wide variation of uncontrollable input parameters to minimize adverse effect on Overall Efficiency, Equipments’ Life and Environmental Pollution has not been adopted, which is essential for maintaining the desired standards of performance parameters.

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Utility of Latest Advancement Fundamental research, renovation and modernization of the coal based thermal power plant process equipments is required to be utilized in integrated approach of improvement in overall performance of the plant

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12

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Compressed Air Flow Model

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Thermal Power Plant Flow Synthesis

Combustion Air Flow Model

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DM Make Up Water Flow Model

FEED LINE AFTER F.C.S. TO FILL ECONOMIZER

WATER WALL DRAIN HEADER TO FILL EVAPORATOR AND DRUM

Figure 3.6 - De-Mineralized Make Up Water Flow Model 16

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Feed Water Flow Model

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Steam Expansion Model

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Electricity Generating Model

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Dynamic Modeling of TPPPP 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Primary Air Flow System Secondary Air Flow System Coal flow System Coal and Primary Air Flow System Fuel Air Supply System (Coal Burners, SADC and Furnace) Drum Model (Coal Combustion and steam generation) Flue Gas Exhaust Temperature (FGET) Regulating System Condenser Flow system Feed water heating system Expansion of Steam through Turbine Electricity Generation System Integrate Grand Model of TPPPP

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Dynamic Modeling of Thermal Power Plant Process Parameters

Primary Air Flow Model

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Dynamic Modeling of Thermal Power Plant Process Parameters

Secondary Air Flow Parameters

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Dynamic Modeling of Thermal Power Plant Process Parameters

Coal Flow Model

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Dynamic Modeling of Thermal Power Plant Process Parameters

Coal and Primary Air Flow Systems

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Dynamic Modeling of Thermal Power Plant Process Parameters

Fuel Air Supply Flow Model

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Dynamic Modeling of Thermal Power Plant Process Parameters

Drum Level Control

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Dynamic Modeling of Thermal Power Plant Process Parameters

Flue Gas Exhaust Temperature Model

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Dynamic Modeling of Thermal Power Plant Process Parameters

Electricity Generation Systems

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Figure - 4.12 Grand Model of Performance Associated Parameters

PWB

+

+

Pm

Q

+

+

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PA

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-

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3

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+

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-

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fg LT SH

HRH

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+

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fg FSH

fg RH

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V

Z

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mil

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O2 %

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GC- 1

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ME

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Performance Parameters Availability Parameters Efficiency Parameters Equipments’ Life Parameters Human Safety Parameters

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Availability Parameters  

Availability Factor Plant Load Factor

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Efficiency Parameters    

Boiler Efficiency Turbine Heat Rate Unit Heat Rate Station Heat Rate

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Efficiency Control Parameters         

Main Steam Temperature Main Steam Pressure Hot Re-Heat Steam Temperature Condenser Vacuum Feed Water Temperature Flue Gas Exhaust Temperature O2 or CO2 % in Flue Gas Auxiliary Power Consumption Load Variation

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Equipments’ Life Parameters        

Pre Combustion Parameter Combustion Parameters Post Combustion Parameters Steam quality parameters Condenser Parameters Turbo Supervisory Parameters Generator Parameters Tube Erosion Parameters Particle Trajectories Particle-Tube Impact Frequency Impact Velocity and Impingement Angle 41

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Human Safety Parameters 

 

Air pollution parameters NOx, SOx and SPM Water pollution Noise pollution

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Estimation of Energy Efficiency Parameters     

Boiler Efficiency (Direct and Indirect method) Turbo Alternator Heat Rate Turbo Alternator Efficiency Unit Heat Rate Station Heat Rate

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Energy Efficiency of the Boiler Boiler Efficiency by Direct Method Qms*(Hms-hfw)+Qrh*(Hhrh-Hcrh) ηb = (Qc*CV+Hcredit)

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Energy efficiency of the Boiler Boiler Efficiency by Indirect Method i.e. by the assessment of losses

Ηb = 100 – Total % Losses

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Boiler Efficiency by Assessment of Losses DFL =W * Cpg * (T – t) W = (C/100+S/267-CinAsh)*100/12(CO2+CO) KgMol/Kg Coal

WFGL=[1.88*(T-25)+2442+4.2*(25–t)]*(Mc+9H)/100 KJ/Kg coal CinAshL=C in A * 33,820 KJ/kg Coal UGL=23,717*(C/100+S/267-inAsh)*CO/12(CO2+CO)KJ/kgCoal MainAirL= Ma * Hu * Cp * (T-t) KJ/Kg Coasl SHinAshL= FlyAsh*Cpfa*(T–t)+BottomAsh*Cpba*(Tf-t) KJ/KgC ShinRejectL= Qmr*Cpr*(Tc+a-t) R&UA/CL (B in KJ/Kg Coal) Log10 B = 0.8167 - 0.4238 log10 C 46

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Energy Efficiency of the Turbine ηc = ∆Hise/(Qms*(Hms-hfw)+Qrh*(Hhrh-Hcrh)) ηt = WT/∆Hiset ηg = MW/WT ηta = MW/(Qms*(Hms-hfw)+Qrh*(Hhrh-Hcrh))

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Energy Efficiency of the Turbine Turbo Alternator Heat Rate THR = (Qms*(Hms-hfw)+Qrh*(Hhrh-Hcrh))/MW Expressed in KJ/KWHrn or in KCal/KWHr

THR = 3600/ ηta in KJ/KWHr THR = 860/ ηta in KCal/KWHr

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Energy Efficiency of the Turbine 

UNIT HEAT RATE



UHR = (THR in KJ/KWHr)/ηb UHR = QC*CVC/MW in KJ/KWHr



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Energy efficiency of the Turbine STATION HEAT RATE   

SHR = Qct*CV/MWt SHR = 100*Qct*CV/(MWt*(100-%APC)) SHR = UHR*100/(100-%APC)

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Condenser Vacuum Management 



Effects of cooling water inlet temperature The primary one is to alter the steam saturation temperature by the same amount as the change. The secondary effect is caused by the fact that the heat transfer of the cooling water film in contact with condenser tubes change with temperature of the water. The primary and secondary changes are in opposite direction. The magnitude of the secondary effect is approximately equal to the fourth root of the mean cooling water temperature. 51

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Condenser Vacuum Management

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Condenser Vacuum Management Cooling Water Flow The primary effect of a change of cooling water flow is to alter it’s temperature rise. The secondary effect, which operates in the same direction as the primary, results from the change of heat transfer rate, due to the changed thickness of the cooling water boundary film. It is approximately proportional to the square root of the flow

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Condenser Vacuum Management

Ts ( Saturation Temp.

Effect of CW Flow on Vacuum 49 48 47 46

Ts

45 44 43 42 41

Qcw ( Cooling Water Flow) 54

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Condenser Vacuum Management Change in Heat Transfer   

Level in Condenser Hot Well Steam Flow Internal/External Tube Deposits

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Condenser Vacuum Management

39382

40185

41005

41842

42696

43568

48102

47159

46234

45328

Series2

44439

48 47.5 47 46.5 46 45.5 45 44.5 44 43.5 43 42.5

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Ts (Saturation Temp)

Effect of Load on Condenser Vacuum)

Qs (Steam Flow) 56

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Condenser Vacuum Management Steam Ejectors / Vacuum Pumps Mal operation of vacuum pump and steam ejectors reduce vacuum. Starting ejector creates vacuum up to 540 mmHgCl, 10 to 30 minutes after, the main ejector should be cut into service followed by immediate withdrawal of starting ejector. Parallel operation of both the ejector shall not only develop the lesser vacuum but also damage the main ejector. Vacuum pump has auto change over from starting to main and normally run satisfactory

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Condenser Vacuum Management Performance Parameters De superheating = T-Ts Sub cooling = Ts-td LMTD = (t2-t1)/ln((Ts-t1)/(Ts-t2)) Temperature rise = t2-t1 TTD =Ts-t2 is high because of; Higher gaseous impurities Air ingress External tube deposits Internal tube deposits

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Feed Water Temperature Management 



Feed water heating system is consisted of two main ejectors, two gland coolers, four low pressure heaters, one direct contact deaerator and three high pressure heaters Feed water temperature at the outlet of the last high pressure heater is a very important efficiency control parameter, which should be optimally half of the main steam temperature

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Feed Water Temperature Management Feed water heaters problems and solutions 







Gaseous impurities in the steam can be managed by better management of boiler and pre-boiler system Vapour line of each heater plays vital role in maintaining the design prescribed value of saturation temperature and also keep terminal temperature difference in acceptable operating range. External tube deposits can gradually increase terminal temperature difference which needs better de mineralized water quality management Internal tube deposits can be effectively minimized by on-line condensate polishing/treatment to maintain terminal temperature difference and condensate/feed water differential pressure across the heater 60

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Feed Water Temperature Management 



Deaerator is the only direct contact heat exchanger and remaining ten heaters of regenerative feed heating system are indirect contact type, major portion of which function like a condenser and hence required to be managed in similar manner discussed for condenser. Both end portions of the each heater perform separate functions, one at the high temperature end works as de super heater and the other at low temperature end works like a sub cooler. De super heating and sub cooling in the heaters are exergetically undesirable and hence attempts should be made to minimize the both

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Excess Air Management Oxygen in flue gas represents the excess air over and above the theoretical air, which is proportionate to coal combustibles but Excess Air requirement increases with increasing coal impurities

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Management of Oxygen in Flue Gas Theoretical Air =4.31*[8*C/3 + 8*(H-O/8) +S] Kg/Kg Coal --- (1) Excess Air =[(TheoreticalCO2%/ActualCO2%)-1]*100%-(2) Excess Air =(O2%*100)/(21-O2%)----------------------------(3) 63

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Management of Oxygen in Flue Gas Shortcomings of the Existing Practice - Unlike theoretical air, no coal parameter is incorporated and hence it does not give any guidance message to operator for suitable change in excess air supply on the basis of coal quality parameters. - Accurately estimated O2% in flue gas for a particular coal may not be valid for a coal different in rank, petrology and composition. 64

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Management of Oxygen in Flue Gas Shortcomings of the Existing Practice - Excess air calculated by using both the above referred equations, is the information of excess air that had been supplied rather than would be supplied for a particular coal. - Information of O2 % at the outlet of boiler does not provide reliable guidance message to forced draught fan operator to supply accurate quantity of air due to time lag and slow combustion response. 65

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Management of Oxygen in Flue Gas



Existing method of maintaining a fixed or an arbitrary percentage of oxygen % in flue gas leads to either Over supply or



Under supply of excess air particularly in case of wide variation in coal quality than that of the design.

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Management of Oxygen in Flue Gas 

Alternative Method of Excess Air Estimation Excess Air =K1*FC-K2*VM+K3*M+K4*A**2+K5--------(4)



Excess Air =K1*C-K2*(5H+3*O/8+S+N)+K3*M+K4*A**2+K5--(5)



Excess Air =k1*I-k2*V-k3*E+k4*M+k5*A**2+k6---------(6) 67

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Management of Oxygen in Flue Gas Assumptions for Applying New Method 







Impact of Hard Grove Index (HGI), Moisture and Ash on pulverizer capacity and fineness is taken care suitably as per the pulverizer condition curves. Pulverizer discharge valve orifices are healthy enough to ensure equal flow to all the four burners at the same elevation. Burner tips and tilting mechanism is not out of synchronism All the fuel air dampers and auxiliary dampers are healthy enough to follow the operating signals as specified 68

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Management of Oxygen in Flue Gas Assumptions for Applying New Method 







No leakage of air anywhere in the air and flue gas path. Proper functioning of the furnace safeguard supervisory system (FSSS) ID, FD & PA Fans are healthy enough to maintain Furnace vacuum, Furnace differential pressure, Wind box pressure, Hot P.A. header pressure ID, FD & PA Fans have sufficient extra capacity (above MCR)

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Management of Oxygen in Flue Gas Equations (4) and (5) are Solved as (7) and (8) Excess Air=0.15*[(F.C.–V.M.)+(M+A**2/10)] ------------(7) Excess Air=0.15*[C-(5H+3*0/8+S+N)+(M+A**2/10] ---(8)

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Management of Oxygen in Flue Gas Test of Equations 



Have been carried out for large numbers of the coal samples, a good numbers of which were collected from different thermal power stations for the purpose of calculating the excess air. The coal parameters of actual samples vary randomly and hence leading to the same kind of variation in calculated excess air. Large numbers of coal samples were simulated by gradually varying the coal parameters so that the results can be presented into an user friendly simple graphics. 71

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Management of Oxygen in Flue Gas 



Estimated excess air is converted into to equivalent amount of O2 % in flue gas, because there is no practice of maintaining excess air as operating parameters. Graphs are plotted for guidance of forced draught fan operator to maintain required oxygen percentage in flue gas on the basis of variation in coal parameters. Coal samples from leading Indian thermal power stations are placed in ascending order of calorific value along with other proximate/ultimate parameters and estimated excess air (O2 % in flue gas) graphically represented for estimating the excess air (O2 % in flue gas) by the forced draught fan operator. A large numbers of simulated coal samples are also considered in similar manner 72

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Management of Oxygen in Flue Gas

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Management of Oxygen in Flue Gas

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Management of Oxygen in Flue Gas Fig. 4 - Effect of Coal Parameter (Proximate Analysis) on Excess Air (O2% in Flue gas)

0.6 0.5

Ash Kg/Kg coal Moisture Kg/Kg coal

0.4

Oxygen % in FG / 5 (E.7) CV in KJ/Kg coal / 40000 Volatile Matter Kg/Kg coal

0.3

Fixed Carbon Kg/Kg coal

0.2 0.1

31

28

25

22

19

16

13

10

7

4

1

0

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Management of Oxygen in Flue Gas Fig. 3 - Effect of Coal Parameter (Ultimate Analysis) on Excess Air (O2% in Flue gas)

0.6 0.5

Carbon Kg/Kg of coal

0.4

Hydrogen Kg/Kg coal

0.3

Nitrogen Kg/Kg coal

0.2

Ash Kg/Kg coal

Oxygen Kg/Kg coal Sulfur Kg/Kg coal Moisture Kg/Kg coal Oxygen % in FG / 5 (E.8)

0.1

CV in KJ/Kg coal / 40000

31

28

25

22

19

16

13

10

7

4

1

0

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Management of Oxygen in Flue Gas Fig. 5 - Effect of Coal Parameter (Proximate Analysis) on Excess Air (O2% in Flue gas)

0.6 0.5

Ash Kg/Kg coal

0.4

Moisture Kg/Kg coal

0.3

CV in K.J./Kg coal / 40000

Oxygen % in FG / 5 (E.7) Volatile Matter Kg/Kg coal

0.2

Fixed Carbon Kg/Kg coal

0.1

28

25

22

19

16

13

10

7

4

1

0

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Management of Oxygen in Flue Gas Fig. 6 - Effect of Coal Parameter (Ultimate Analysis) on Excess Air (O2% in Flue gas)

0.6 0.5

Carbon Kg/Kg of coal Hydrogen Kg/Kg coal

0.4

Oxygen Kg/Kg coal Nitrogen Kg/Kg coal

0.3

Sulfur Kg/Kg coal Ash Kg/Kg coal Moisture Kg/Kg coal

0.2

Oxygen % in FG / 5 (E.8) CV in K.J./Kg coal / 40000

0.1

28

25

22

19

16

13

10

7

4

1

0

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Management of Oxygen in Flue Gas

Fig. 7 - Effect of Coal Parameter (Proximate Analysis) on Excess Air (O2% in Flue gas)

0.6 0.5 Ash Kg/Kg coal

0.4

Moisture Kg/Kg coal Oxygen % in FG / 5 (E.7)

0.3

CV in K.J./Kg coal / 40000 Volatile Matter Kg/Kg coal

0.2

Fixed Carbon Kg/Kg coal

0.1

79

31

29

27

25

23

21

19

17

15

13

11

9

7

5

3

1

0

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Management of Oxygen in Flue Gas Fig, 8 - Effect of Coal Parameter (Ultimate Analysis) on Excess Air (O2% in Flue gas)

0.6 0.5

Carbon Kg/Kg of coal Hydrogen Kg/Kg coal

0.4

Oxygen Kg/Kg coal Nitrogen Kg/Kg coal

0.3

Sulfur Kg/Kg coal Ash Kg/Kg coal

0.2

Moisture Kg/Kg coal Oxygen % in FG / 5 (E.8)

0.1

CV in K.J./Kg coal / 40000

80

31

28

25

22

19

16

13

10

7

4

1

0

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Operational Feasibility Analysis of the Proposals

Management of Oxygen in Flue Gas Fig. 9 - Effect of Coal Parameter (Proximate Analysis) on Excess Air (O2% in Flue gas)

1.4 1.2 1

Ash Kg/Kg coal Moisture Kg/Kg coal

0.8

Oxygen % in FG / 5 (E.7) CV in KJ/Kg coal / 40000

0.6

Volatile Matter Kg/Kg coal Fixed Carbon Kg/Kg coal

0.4 0.2

81

31

28

25

22

19

16

13

10

7

4

1

0

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Operational Feasibility Analysis of the Proposals

Management of Oxygen in Flue Gas Fig. 10 - Effect of Coal Parameter (Ultimate Analysis) on Excess Air (O2% in Flue gas)

1.4 1.2 1 Carbon Kg/Kg of coal Hydrogen Kg/Kg coal

0.8

Oxygen Kg/Kg coal Nitrogen Kg/Kg coal Sulfur Kg/Kg coal

0.6

Ash Kg/Kg coal M oisture Kg/Kg coal Oxygen %in FG / 5 (E.8)

0.4

CV in KJ /Kg coal / 40000

0.2

82

31

29

27

25

23

21

19

17

15

13

11

9

7

5

3

1

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Operational Feasibility Analysis of the Proposals

Management of Oxygen in Flue Gas Fig. 11 - Effect of Coal Parameter (Proximate Analysis) on Excess Air (O2% in Flue gas)

1.4 1.2 1

Ash Kg/Kg coal Moisture Kg/Kg coal

0.8

Oxygen % in FG / 5 (E.7)

0.6

CV in K.J./Kg coal / 40000

0.4

Fixed Carbon Kg/Kg coal

Volatile Matter Kg/Kg coal

0.2 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

0

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Operational Feasibility Analysis of the Proposals

Management of Oxygen in Flue Gas Fig. 12 - Effect of Coal Parameter (Ultimate Analysis) on Excess Air (O2% in Flue gas)

1.4 1.2

Carbon Kg/Kg of coal Hydrogen Kg/Kg coal

1

Oxygen Kg/Kg coal Nitrogen Kg/Kg coal

0.8

Sulfur Kg/Kg coal

0.6

Ash Kg/Kg coal Moisture Kg/Kg coal

0.4

Oxygen % in FG / 5 (E.8) CV in K.J./Kg coal / 40000

0.2

84

31

28

25

22

19

16

13

10

7

4

1

0

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Operational Feasibility Analysis of the Proposals

Management of Oxygen in Flue Gas Fig. 13 - Effect of Coal Parameter (Proximate Analysis) on Excess Air (O2% in Flue gas)

1.2 1

ash kg/kg Coal

0.8

Most kg/kg Coal Oxygn % in FG/5 (E.7)

0.6

CVcoal KJ/Kg/ 40000 VM kg/kg Coal

0.4

FC kg/kg Coal

0.2

85

31

28

25

22

19

16

13

10

7

4

1

0

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Operational Feasibility Analysis of the Proposals

Management of Oxygen in Flue Gas Effect of Ultimate Parameter on Excess Air (O2% in Flue gas) Crbn kg/kg Coal 1.2 Hdgn kg/kg Coal 1 Oxgn kg/kg Coal 0.8

Ntgn kg/kg Coal

0.6

Slf r kg/kg Coal

0.4

ash kg/kg Coal Most kg/kg Coal

0.2

Oxygn % in FG/5 (E.8) 31

28

25

22

19

16

13

10

7

4

1

0

86

CVcoal KJ/Kg/ 40000

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Operational Feasibility Analysis of the Proposals

Management of Oxygen in Flue Gas 







Variation in CV due to combustibles lead to the proportionate changes in theoretical air but excess air requirement changes indifferently depending upon quantities of impurities (oxygen, nitrogen, sulfur, moisture and ash) in coal and their combustion behavior . Proposed excess air is leading to a value of oxygen in flue gas near to the conventional value (i.e. 4%) in many cases, which are operating at or near to the design coal parameters. Excess air (O2 % in flue gas) requirement is increasing tremendously for poor coals with higher ash content. Excess air (O2 % in flue gas) is too low for superior coals specifically with high volatile matter and low ash content.

87

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Operational Feasibility Analysis of the Proposals

Management of Oxygen in Flue Gas Limitations of New Method of Excess Air Estimation 



Proposal of increasing excess air leads complete combustion of poor coal but may increase dry flue gas loss than the reduction in combustible loss. In such cases, minimum total of combustible loss and dry flue gas loss shall decide the optimized quantity of excess air rather than formula under reference. Even this may leads to total flue gas volume, which may be higher enough to cross limits of critical velocity and exponentially increases the flue gas erosion. In this situation load has to be reduced in place of reducing the optimized air. Load reduction cannot be more than 65% for very poor coal and supplementary fuel oil or gas has to be used to minimize loss of boiler life and efficiency.

88

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Management of Flue Gas Exhaust Temperature

Flue gas exhaust temperature rise from 18 deg C to 20 deg C causes 1% loss of boiler efficiency for higher ash coal to the moderate ash coal respectively

89

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Management of Flue Gas Exhaust Temperature

15 10

Dry Gas Loss %

Wet Flue Gas Loss %

5

M oisture In Combustion Loss %

90

190

Flue Gas Temperature in deg. C

180

170

160

150

140

130

120

110

100

90

0 80

Losses in %

20

Boiler Losses %

confidentia

90

90 10 0 11 0 12 0 13 0 14 0 15 0 16 0 17 0 18 0 19 0

88 86 84 82 80 78 80

Blr. Efficiency

Management of Flue Gas Exhaust Temperature

Flu Gas Temperature in deg. C 91

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Management of Flue Gas Exhaust Temperature

Flue Gas Exhaust Temperature Management



Boiler Input System Combustion air flow system Coal & fuel oil flow system

 

Flue gas flow system Water/steam flow system

92

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Management of Flue Gas Exhaust Temperature

Combustion Air Flow System Accurate assessment and correct distribution of combustion air solve many of the steam generator’s problems

93

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Management of Flue Gas Exhaust Temperature

Coal Flow System Unit coal flow system       

Bunkers Feeders Coal burners Pulverizes Primary air fans, Hot and cold primary air ducts Air pre heaters

94

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Management of Flue Gas Exhaust Temperature

Coal Flow System Coal input parameter      

Fixed Carbon Volatile Matter Ash Moisture Hard groove index Coal flow

95

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Management of Flue Gas Exhaust Temperature

Coal Flow System Operating parameters         

Hot primary air flow Hot primary air pressure Hot primary air temperature Pulverized coal fineness Temperature of the coal air mixture Coal flow Raw coal feeder speed Mill differential pressure Coal/air mixture pressure drop from mill outlet to burner

96

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Management of Flue Gas Exhaust Temperature

Coal Flow System Coal supply limits        

Fan power limit Pulverized coal fall out limit Pulverized coal pipe erosion limit Mill outlet temperature limit Mill power limit Maximum coal flow limit Grinding, drying & pulverized coal fineness stability limit Air/coal ratio explosion limit

97

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Management of Flue Gas Exhaust Temperature

Coal Flow System Notable Features of the Coal Flow System 



Design specified quantity of the hot primary air is decided to be adequate to dry maximum possible moisture in the coal. Relatively lesser percentage of actual moisture in coal than that of the design is accommodated by mixing cold primary air also known to be tempering air Mill constraints drawn on airflow versus coal flow graph left very small space for mill operation, known as “mill operating window”

98

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Management of Flue Gas Exhaust Temperature

Flue Gas Flow System System Equipments     

SADC & Burners Mills, Boiler Fans and APH Flame Scanners and Soot Blowers Evaporator, SH, RH and Economizer Boiler Drum

99

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Management of Flue Gas Exhaust Temperature

Flue Gas Flow System

System Parameters

      



Parameters of input Fuel and Air Wind box to furnace differential pressure Mill to furnace differential pressure Furnace vacuum Burner tilt (n-2) coal elevations out of ‘n’ Differential pressure and temperature of the flue gas across WW, PSH, RH, FSH, LTSH Eco, APH & ESP Fire Ball Position

100

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Management of Flue Gas Exhaust Temperature

Flue Gas Flow System Control of Soot Deposits 





Frequent soot blowing with designed steam pressure and temperature can keep the tubes clean to improve the heat transfer. Long retractable soot blowers do not function satisfactorily and causing lot of soot deposition on platen super heater, re-heater, final super heater, low temperature super heater and economizer. Air pre heater soot blowing also should be managed well because its choking results in reduced heat transfer and higher flue gas exhaust temperature. Air pre heater seals are also very important and must be maintained.

101

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Management of Flue Gas Exhaust Temperature

Flue Gas Flow System Control of Acid Deposition Flue gas exhaust temperature can be optimally reduced to avoid occurrence of flue gas dew point temperature. Reduction of flue gas exhaust temper shall be lower for lower flue gas dew point temperature and high ambient temperature. High ash content of the coal neutralizes the acidic effect due to its alkalinity and lead to a lower flue gas dew point temperature.

102

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Management of Flue Gas Exhaust Temperature

Flue Gas Flow System SPM Control in Flue Gas Electro static precipitator reduces the suspended particulate matter up to the extent of 150 mg/NM3, higher fly ash erode the induced draught fan impeller very severely and makes it quite difficult to maintain the differential pressure across the various heat exchangers of the steam generators.

103

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Management of Flue Gas Exhaust Temperature

Water / Steam Flow System Heat released in coal combustion is utilized in converting pressurized water into superheated steam. Heat is absorbed as   

Sensible heat of water in economizer, Latent heat of steam in water walls and Sensible heat of steam in SH/RH. Design specified parameters of flue gas and water / steam across various heat exchangers lead to a constant ratio of heat absorption in them. Variation in airflow, coal flow and flue gas flow parameters vary the water / steam flow parameters which lead to change in heat absorption ratio

104

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Management of Flue Gas Exhaust Temperature

Water / Steam Flow System Heat Balance Equation for the Boiler Heat given by flue gas = heat taken by water/steam Qc*CVc - Losses = Qms (Hms-hw) + Qrh (Hhrh – Hcrm) Qfg*Cpfg*(Tf -Teco) = Qms*(Hms–hw) + Qrh (Hhrh – Hcrh)

105

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Management of Flue Gas Exhaust Temperature

Water / Steam Flow System Detailed Heat Balance Qfg*Cpfg*[ (Tf-Tpsh) + (Tpsh-Trh) + (Trh-Tfsh) + (Tfsh-Tltsh) + (Tltsh-Teco) + (Teco-Taph) ] = Qw*S*(tfwo–tfwi) + Qw*S*(Ts –tfwo) + Qms*L + Qms*Cps*(Tms–Ts) + Qcrh* Cps* (Thrh–Tcrh) I1+I2+I3+I4+ I5+I6 = F1+F2+F3+F4

106

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Management of Equipments’ Life Parameters Wear/tear mechanism     

Erosion Corrosion Creep Fatigue Overheating

107

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Management of Equipments’ Life Parameters

Erosion







High velocity fluid streams with suspended solid impurities erode heat exchanger in thermal plants ranging from condenser to boiler. On average, the erosion wear is proportional to the impact velocity of the particles to the power 2.5. In general the extent of surface erosion by impingement of abrasive particles depends upon the following factors. System operation conditions (such as particle impinging velocity, impact angle, particle number density at impact, properties of the carrier fluid). Nature of target tube material (such as material properties, tube orientation and curvature, and surface condition) The properties of impinging particles (such as particle type and grade, mechanical properties, size and sphericity)

108

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Management of Equipments’ Life Parameters

Erosion Erosion Control Parameters    

Free stream velocity of the fluid (Uo) Impact velocity (W1) Frequency of impaction (η) Impingement angle (β1)

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Management of Equipments’ Life Parameters

Erosion Boiler Erosion Control Indian boilers have already suffered an irreparable loss of life and capacity utilization. Large deviation in coal parameters from the design specified values, leads to significant variation in impacting particles’ properties (grade, size and shape), which erodes external tube surface and cause the failure much before the expiry of design life time.

110

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Management of Equipments’ Life Parameters

Erosion Flue Gas Volume Vfg =Vair+Vm*(H/4+CO/24+M/18+N/28+O/32)*Qc

111

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Management of Equipments’ Life Parameters

Erosion C% IN C/10

16

H% 14

O% N%

12

S%

10

%hike Total vol HHV KCal/kg/4000

8 6 4 2 0 1

3

5

7

9

11

13

15

17

19

112

21

23

25

27

29

31

confidentia

Management of Equipments’ Life Parameters

Erosion 0.3

Hydrogn Kg/Kg coal Oxygen Kg/Kg coal

0.2

Nitrogn Kg/Kg coal Sulfur Kg/Kg coal %total volum Chang/45 0.1

Carbon Kg/Kg coal/5

0 1

3

5

7

9

11 13 15 17 19 21 23 25 27 29 31

113

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Management of Equipments’ Life Parameters

Erosion 0.5

0.4

Hydrogn Kg/Kg coal Oxygen Kg/Kg coal 0.3

Nitrogn Kg/Kg coal Sulfur Kg/Kg coal %total volum Chang/20

0.2

Carbon Kg/Kg coal/5 0.1

0 1

3

5

7

9

11

13

15

17

19

21

114

23

25

27

29

confidentia

Management of Equipments’ Life Parameters

Erosion 0.5

0.4

Hydrogn Kg/Kg coal 0.3

Oxygen Kg/Kg coal Nitrogn Kg/Kg coal

0.2

Sulfur Kg/Kg coal

0.1

%total volum Chang/10 Carbon Kg/Kg coal/5

0 1

3

5

7

9

11 13 15

17 19 21 23

115

25 27 29 31

confidentia

Management of Equipments’ Life Parameters

Erosion 0.5

0.4

Hydrogn Kg/Kg coal

0.3

Oxygen Kg/Kg coal Nitrogn Kg/Kg coal Sulfur Kg/Kg coal

0.2

%total volum Chang/10 Carbon Kg/Kg coal/5 0.1

0 1

3

5

7

9 11 13 15 17 19 21 23 25 27 29 31

116

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Management of Equipments’ Life Parameters

Erosion 0.5

0.4

Hydrogn Kg/Kg coal 0.3

Oxygen Kg/Kg coal Nitrogn Kg/Kg coal

0.2

Sulfur Kg/Kg coal

0.1

%total volum Chang/30 Carbon Kg/Kg coal/5

0 1

3

5

7

9

11 13 15 17 19 21

117

23 25 27 29 31

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Management of Equipments’ Life Parameters

Erosion Hydrogn Kg/Kg coal 0.5

Oxygen Kg/Kg coal Nitrogn Kg/Kg coal

0.4

Sulfur Kg/Kg coal %total volum Chang/20 Carbon Kg/Kg coal/5

0.3

0.2

0.1

0 1

3

5

7

9

11

13 15 17 19

21 23 25

118

27 29 31

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Management of Equipments’ Life Parameters

Erosion

Free Stream Velocity Control       

Air flow Coal flow Coal fineness Burner tilt Mill outlet temperature Secondary air temperature Combustion temperature

119

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Management of Equipments’ Life Parameters

Erosion Free Stream Velocity Control – Cont.    



Secondary air damper position Heat absorption Air pressure at outlet of forced draught fan Flue gas pressure drop across the platen super heater, re-heater, final super heater, low temp super heater, economizer Flue gas temperature drop across platen super heater, re-heater, final super heater, low temp super heater, economizer

120

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Management of Equipments’ Life Parameters

Flue Gas Erosion Abatement Techniques Some of the tube erosion parameters such as shape, size grade, frequency & velocity of the impacting particle, free stream velocity of the carrier fluid and surface condition of the tube itself depend upon various boiler operating and input parameters which can be improved by; - Use of beneficiated coal reduces the frequency of impacting particles. In case of poor coal quality, coal blending and oil support also reduce the boiler tube erosion.

121

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Management of Equipments’ Life Parameters

Flue Gas Erosion Abatement Techniques - Flue gas volume is proportional to the volume of the combustion air. Accurate excess air management is quite essential to keep free stream velocity well within the erosion limits - Frequent use of soot blowing keeps the tube surface clean which do not allow the cross section area to reduce to a value at which free stream velocity can cross the erosion limits. - Baffle plates can be used in high speed zone of boiler to keep the flue gas velocity within the specified ranges.

122

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Management of Equipments’ Life Parameters

Flue Gas Erosion Abatement Techniques - Furnace Vacuum and differential pressures across the wind box, platen super heater, re heater, final super heater and economizer also influence the impacting particle velocity. Well maintained boiler fans are essential to keep various deferential pressures within the specified ranges. - Particle size can be controlled by maintaining pulverizers healthy. Reduced pulverizer capacity operation is essential in case of lower hard groove index, high ash content, high moisture content of the coal, and larger particle size or poor fineness at its outlet.

123

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Management of Human Safety Parameters    

Global warming Acid rain Desertification Ozone layer depletion

124

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Management of Human Safety Parameters

Air pollution   

SOx NOx Suspended particulate matter

125

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Conclusions Some of the improvement potential parameters have been analyzed and examined for implementation to reduce the avoidable loss component of various processes and equipments Many other parameters, which also influence the thermal power plant performance, are not included either because of the satisfactory practices in the power plants or because of the academic limitations of the work

126

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Management of Equipments’ Life Parameters

Flue Gas Erosion Abatement Techniques - Sufficient clearance must be incorporated at the design stage itself on the basis of erosion severity. - Tubes of higher erosion resistance should be used. - Boiler should not be allowed to run at higher loads with very poor coal - Tower type boilers are reported to be less susceptible for flue gas erosion. - Air ingress through men holes, peep holes/inspection doors and cracks should be minimized.

127

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Conclusions Main contribution of the work is related to the assessment of performance loss of various processes and process equipments due to variation in input parameters and its distinction, partly as inevitable and partly as avoidable, which help the power plant performance manager to focus their full attention to reduce the latter of the two. Some of the contributions are briefly concluded in next slides;

128

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Conclusions

Ambient Air Parameters   

Temperature Humidity Purity

Influence   

Air conditioning systems Air cooled devices Air handling devices

129

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Conclusions

Ambient Air Parameters Performance loss for A/C systems Change in air conditioning load on account of ambient air temperature/ relative humidity up to the acceptable optimum values for the men and material inside control volume is inevitable. Difference between inevitably optimized values and pre- decided standard values is avoidable.

130

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Conclusions

Ambient Air Parameters Performance loss of air cooled devices Huge amount of heat is rejected to the ambient air from cooling water, air cooled electrical/electronic equipments and electromechanical losses. Temperature, Humidity and Purity influence the functional performance of various air cooled devices either because of alteration in sensible heat addition to the air or because of reduction in latent heat addition to the air on account of different values of ambient air temperature and humidity respectively.

131

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Conclusions

Ambient Air Parameters Performance loss of air cooled devices Difference between the dry bulb temperature and wet bulb temperature, is proportional to the evaporation of the cooling water through wet cooling tower, which in turn proportionately reduces the temperature of the cooling water and finally it leads to better condenser vacuum, failing which the difference between hot cooling water temperature and ambient air temperature must be high enough to absorb the total heat of cooling water as the sensible heat of air flowing through the cooling tower and failing both, loss of vacuum becomes inevitable.

132

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Conclusions

Ambient Air Parameters Performance loss for air handling devices Driving motors of blowers, fans and compressors consume significant power in thermal power stations, which increases with increasing air temperature. Fans and blowers in the plant handle huge quantity of air at low and moderate discharge pressure, none of which is provided to regulate the temperature of air at its inlet. High humidity and suspended solid impurities increase little power consumption but deteriorate the components of air handling device quite significantly. More power consumption in high flow, low pressure air handling devices is inevitable

133

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Conclusions

Ambient Air Parameters Few other effects of high ambient air temperature 





High air temperature helps in reducing down the flue gas exhaust temperature by increasing average air pre heater metal temperatures and delaying the sulfuric acid formation. High air temperature also helps in maintaining relatively higher values of hot primary air and secondary air, which leads to better pulverization and combustion. Combustion air play vital role at the fire side of the boiler input and output, positive aspects of the changes increase the prescribed standards of the performance and reduce the avoidable component of inefficiency and vice-versa.

134

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Conclusions

Raw Water Parameters 



Deterioration in raw water quality increase the cost of chemical treatment for drinking, bearing cooling and main working media (de-mineralized water). No such treatment is done for the condenser cooling water and deteriorates the condenser life by tube erosion and corrosion, which adversely influence electricity availability and thermal efficiency.

135

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Conclusions

Raw Water Parameters Loss of Condenser Vacuum Condenser vacuum is a semi controllable parameter which is limited by cooling water inlet temperature. Such loss in condenser vacuum is inevitable and hence its impact has been quantitatively determined so that managerial efforts of vacuum improvement can be concentrated on avoidable loss which is equal to actual loss minus the estimated inevitable

136

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Conclusions

Raw Water Parameters Loss of Condenser Vacuum Condenser vacuum is a semi controllable parameter which is limited by cooling water inlet temperature. Such loss in condenser vacuum is inevitable and hence its impact has been quantitatively determined so that managerial efforts of vacuum improvement can be concentrated on avoidable loss which is equal to actual loss minus the estimated inevitable

137

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Conclusions

De Mineralized Water Parameters Initial Filling It is observed that the de mineralized make up water separately filled in condenser hot well, deaerator and boiler drum by using make up water pump, emergency lift pumps and boiler fill pumps respectively. This by passes starting facilities of supplying auxiliary steam to last low pressure heater, hydrazine dozing after deaerator. This do not save starting time and energy as it is claimed but likely to reduce boiler and turbine life due to improper quality of the boiler feed water.

138

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Conclusions

DM Water/Steam Parameters Causes of abnormal water level in the condenser    

Failure of the auto control valve High steam flow Malfunctioning of the condensate pump Tube failure

Consequences  

 

Sub cooling of the condensate increase heat loading High level reduce the heat transfer area for condensation, which results in poor condenser vacuum low level may lead to the damage of the pump and heaters. Raw water damages the entire DM water and steam circuit in a catastrophic manner

139

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Conclusions

DM Water/Steam Parameters Condensate System Extraction steam flow/pressure/temperature and condensate/feed water flow/temperature are the uncontrollable parameters and in turn these make the feed water outlet temperature as the uncontrollable parameter. A very little control on auxiliary steam flow to the last low pressure heater for initial heating before the deaerator is rarely utilized, which leads to loss of life and efficiency

140

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Conclusions

DM Water/Steam Parameters Proper Deaeration Deaerator is meant for physical deaeration of the feed water and raising its temperature and pressure to the suction requirement of boiler feed pump. Hydrazine is injected after the deaerator to reduce the oxygen less than the minimum displayable value of the instrument provided for.

141

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Conclusions

DM Water/Steam Parameters Feed Water System Loss of boiler/turbine life and thermal efficiency due to non availability of the high pressure heaters have been reported to be quite significant in many Indian thermal power station, which demands better standards of operation and maintenance practices.

142

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Conclusions

DM Water/Steam Parameters Feed Water Flow to the Boiler Controlling device of the boiler feed pumps quickly ensure the sufficient differential pressure across the feed control station from where actual flow to the boiler is regulated to maintain the design prescribed water level in the boiler drum. Normal drum level represents the thermodynamic stability of the boiler, which is controlled by rate of steam generation and steam flowing out of the boiler. Steam generation depends upon firing rate and feed water supply.

143

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Conclusions

DM Water/Steam Parameters Sensible heat addition in economizer Feed water temperature at the inlet of the economizer must be more than the flue gas dew point temperature. And at the outlet of economizer must be sufficiently lower than the corresponding flue gas temperature

144

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Conclusions

DM Water/Steam Parameters Evaporation Steam generation rate in the water walls (evaporator) is controlled by heat absorption at external surface of the tubes and fire ball position. Evaporation abnormalities reflects on drum level, un-stability of which indicates poor boiler health. Provision of restricting orifices at the evaporator tubes inlet to ensure equal flow through the tubes help in reducing localized starvation and subsequent overheating.

145

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Conclusions

DM Water/Steam Parameters Steam Super Heating and Re Heating Steam temperature at the outlet of the super heater and re heater should be maintained without injecting any attemperation by properly controlling the other parameters, such as burner tilt and selecting the lower elevation for fuel firing

146

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Conclusions

DM Water/Steam Parameters Expansion of steam in turbine Expansion of steam through steam turbine must be monitored in terms of design specified reductions in temperatures and pressures Variation in turbo supervisory parameters must be analyzed for the improvement of running parameters beginning with steam temperature, pressure and purity.

147

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Conclusions

DM Water/Steam Parameters Steam Flow Control 



Flow of steam to the turbine is controlled by turbine governing system in line with turbo supervisory parameters, generator parameters, condenser vacuum, grid frequency and boiler parameters inclusive of steam temperature and pressure. Normal governing equipments, test equipments, pre emergency equipments and emergency equipments must be maintained well and kept on auto functioning until there is a dire need to bypass any one of them

148

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Conclusions

Coal Flow System Parameters Mill Capacity Modulation Ash Moisture Hard Groove Index Fixed carbon

Fineness

149

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Conclusions

Coal Flow System Parameters Hot primary air flow regulation   

Moisture content in the coal Hot primary air temperature Cold primary air temperature

150

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Conclusions

Coal Flow System Parameters Combustion air flow regulation  

Stoichiometric air flow Excess air flow estmation

151

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Conclusions

Coal Flow System Parameters Secondary air flow regulation = Stoichiometric air + Excess air – Primary air

152

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Conclusions

Coal Flow System Parameters Essentials of Combustion Combustibles from Coal Oxygen Combustion air Turbulence Combustion air pr. & dir. Temperature Supplementary fuel/arc Time Blr. dim. & combustion air

153

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Conclusions

Coal Flow System Parameters Primary air is meant for dry and transport the coal from mill to the furnace. Secondary air is supplied to ensure proper flow of products of combustion and to ensure complete combustion. Tertiary air is supplied to suppress the heat flux to minimize pollutants production

154

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Conclusions

Coal Flow System Parameters Secondary air damper control system play vital role in successful combustion, some of which modulate in proportion to the fuel quantity and known as fuel air dampers where as the others are meant for maintaining prescribed differential pressure in between the secondary air wind box and furnace. Place and direction of secondary air supply is as valuable as the estimation of correct quantity.

155

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Conclusions

Coal Flow System Parameters Role of supplementary fuel firing equipments, monitoring devices, soot blowers etc play equally important role combustion management as that of secondary air dampers, burners, burner tilting mechanism etc.

156

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Conclusions

Coal Flow System Parameters Heat transfer from flue gas to the water/steam is influenced by input, output and differential temperatures of both the hot and cold fluid. External and internal tube deposits or any input/ output variation destabilize the proportionate heat transfer and cause abnormalities leading to the loss of boiler life and efficiency. Air pre heater is the last heat exchanger in the coal combustion flow path, which extract heat from the minimum temperature and send it back to the boiler through combustion air

157

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Recommendations

158

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Recommendations

Ambient Air Parameters

Recommendations for air conditioning systems - 18 deg C, 50-60% RH in winter - 28 deg C, 50-60% RH in summer In place of alignment point of 25 deg C, 50% RH or lower value

Woolen cloths in the winter as usual and internal air circulation in the summer to reduce APC.

159

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Recommendations

Ambient Air Parameters Recommendations for air cooled devices Amount of air supply has to be increased to increase the total

evaporation up to the most optimized limits and rest of the performance loss has to be treated as inevitable. Recirculation flow will also help in avoiding the avoidable component of loss.

160

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Recommendations

Ambient Air Parameters Recommendations for Wet Cooling Towers It is recommended to install air flow variation system with cooling tower fan to partially curtail the loss of condenser vacuum in the situations of high heat and humidity so that the avoidable component of loss of efficiency due to poor condenser vacuum can be set aside.

161

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Recommendations

Ambient Air Parameters Recommendations for air handling devices Low flow high discharge pressure compressors should be provided with pre cooler and inter cooler to minimize the avoidable loss where as for high flow, low discharge pressure the loss should accepted as inevitable

162

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Recommendations

Ambient Air Parameters In case of high ambient air temperature, we should maintain lower flue gas exhaust temperature due to low FGDPT, which lead to better boiler efficiency.

163

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Recommendations

Raw Water Parameters Recommendations for Condenser Vacuum After exhausting all the efforts of cooling water inlet temperature optimization, associated inevitable component of the loss of condenser vacuum has to be determined. So determined inevitable component is deducted from the actual loss to determine the avoidable, which is minimized by increasing cooling water flow, keeping tubes clean, minimizing the air ingress, improving the steam quality and effectively utilizing the vacuum creating devices A paper to this effect was presented in a global conference in 2004 at JMI

164

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Recommendations

Raw Water Parameters 







High TTD causes and remedial measures; Higher gaseous impurities in the steam can be managed by better management of boiler and pre-boiler system Air ingress can be avoided by frequent leak detection test and effective steam sealing of low pressure turbine. External tube deposits can gradually increase terminal temperature difference which needs better de mineralized water quality management. Internal tube deposits causing higher terminal temperature difference with higher cooling water pressure across the condenser can be effectively minimized by on-line condenser tube cleaning.

165

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Recommendations

Raw Water Parameters

Recommendations for reducing the avoidable component of condenser vacuum SE creates vacuum up to 540 mmHgCl. It is better to sufficiently wait till the capacity of starting ejector is exhausted and stable vacuum is maintained. 10 to 15 minutes after the establishment of stable vacuum by starting ejector, ME should be cut into service followed by withdrawal of SE. Parallel operation of both the ejector shall not only develop the lesser vacuum but also damage the main ejector tips.

166

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Recommendations

De Mineralized Water Parameters Recommendations for initial filling It is recommended that after filling condenser hot well to required level, condensate extraction pump should be started to divert the extra DM water to the deaerator until it is half filled. After the establishment of deaerator parameters, boiler feed pump should be started and then feed water should be taken to economizer till water level in the drum is adequate. Boiler fill pumps and emergency lift pumps must not be used for normal start up because they provided to fill boiler for the purposes other than the start up.

167

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Recommendations

DM Water/Steam Parameters Recommendations for Feed Heaters  



Steam and drip control of the heaters should be improved. It is also recommended to have control valves on extraction lines to have better control on feed water outlet temperature. Vapour line of every heater should be kept clean to improve the heat transfer.

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Recommendations

DM Water/Steam Parameters

Recommendations for Proper Deaeration Quantity of the hydrazine injected to the feed water, after the deaerator to reduce the oxygen less than the minimum displayable value of the instrument should be optimized to reduce non condensable gases in the condenser. Attempt should be made to maximize the physical deaeration by properly maintaining the deaerator parameters and repairing the internals to minimize the chemical deaeration to further reduce the formation of non condensable gas in condenser. Auxiliary steam supply to last low pressure heater is beneficial and helps in maintaining the deaereator parameters quickly, which improves physical deaeration.

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Recommendations

DM Water/Steam Parameters High Pressure Heaters Adequate drip level in the heaters and its proper diversion save heat at high potential, which leads to the less destruction of exergy. Practicing exergy analysis for heat exchangers in general, help in improving the performance and applicable to the regenerative feed heating equipments too.

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DM Water/Steam Parameters Recommendations for low feed water temperature at the outlet of economizer Low temperature feed water should be heated introducing an additional heater in between the last high pressure heater and economizer to ensure heat transfer in the boiler under design prescribed differential temperatures and proportions of heat flux.

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Recommendations

DM Water/Steam Parameters Recommendations for the evaporator Boiler blow downs should be optimally utilized. CBD & IBD should utilized only on the basis of chemical analysis of feed water samples from evaporator and use of EBD should be avoided by better co-ordination of fuel firing to the boiler and steam supply to the turbine. Phosphate dozing should be optimized.

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Recommendations

DM Water/Steam Parameters Steam Super Heating and Re Heating Pressure dominated steam must not be allowed for expansion in steam turbine.

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DM Water/Steam Parameters Expansion of steam in turbine On line determination of energy and exergy parameters help operation managers to estimate avoidable component of performance loss and in turn to initiate the action to curtail the same. Axial shift, differential expansion, eccentricity and vibration are also utilized for the improvement of running parameters beginning with steam temperature, pressure and purity.

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Recommendations

DM Water/Steam Parameters Recommendations for Auxiliary Steam Significant amount of steam is taken from the main steam line for auxiliary purposes. Temperature and Pressure are reduced from 540 deg C and 137 Kg/sqcm to 200 deg C and 15 Kg/sqcm by mixing water, which results in large loss of exergy. It will be better to take steam of lower exergetic potential from the different source such as lower temperature header of the super heater, extraction from the turbine, pressure vessel etc.

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Recommendations

Coal Flow System Parameters After exhausting all the efforts of using design specified coal, following efforts should be made to minimize the adverse effect of relatively inferior coal quality than that of the design;   

Pit head coal washing should be done. Fuel blending is recommended Coal mill capacity should be reduced in accordance with mill operating condition curves

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Recommendations

Coal Flow System Parameters 

Total air flow should be modified in accordance with equation 7 and 8 of the chapter VII and total flow through the boiler should be restricted sufficiently lower than that of the critical velocity in any part of the steam generators. Lot of attention is required to improve the operation and maintenance of secondary distribution system particularly for the Indian boilers. A reliable operator friendly secondary air damper control system should be introduced. Paper was presented in 2005 at DCE in international seminar and 2004 JMI)

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Recommendations

Coal Flow System Parameters Capacity of the individual mill should be further reduced either because of inadequate pulverized coal fineness or because of high current of the mill driving motor.  It is also recommended to supply supplementary fuel oil or gas to maintain loading conditions nearest possible to the maximum continuous rating, particularly for the units, which are not stable at partial loads. 

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Recommendations

Coal Flow System Parameters Long retractable soot blowers of many thermal units, do not function satisfactorily and cause lot of soot deposition on PSH, RH, FSH, LTSH & Economizer. APH soot blowing also should be managed well because its choking results in reduced heat transfer and higher flue gas exhaust temperature. Air pre heater seals are also very important and must be maintained.

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Recommendations

Coal Flow System Parameters FGDPT in case of high ash and low sulfur coals is relatively lower, which must be incorporated in the design for a lower flue gas exhaust temperature. Operational efforts also should be made to optimally reduce the flue gas exhaust temperature to improve boiler efficiency as there is no possibility of occurrence of acid deposition. High ambient temperature increases the average air pre heater metal temperature and permit for further lowered down the flue gas exhaust temperature. (Paper was presented at national seminar in Coakata in 2006)

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Recommendations

Coal Flow System Parameters Drum level operator should be provided with additional instrument showing coal flow and steam flow so that he can maintain better heat and mass balance with matching responses.

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Recommendations

Coal Flow System Parameters 





Either economizer may be provided with one more standby feed water heating system or flue gas path should be provided with additional fuel firing system before the economizer. APH may be provided with more heating element to further reduce flue gas exhaust temperature. Design prescribed voltage of electro static precipitator fields and proper functioning of the wrapping mechanism must be maintained to reduces the suspended particulate matter up to the law prescribed value of 150 mg/NM3.

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Recommendations

Coal Flow System Parameters 



Recommendations for minimizing the adverse effect of the tube erosion parameters (i.e. shape, size grade, impact frequency, impact velocity, free stream velocity of the carrier fluid and surface condition of the tube, depend upon various boiler operating and input parameters); (a paper was presented in 2006 in a national seminar at JMI) Flue gas volume is proportional to the volume of the combustion air. Accurate excess air management is quite essential to keep free stream velocity well within the erosion limits

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Recommendations

Coal Flow Systems’ Parameters 





Soot blowing also keeps the tube surface clean which do not allow the cross section area to reduce to a value at which free stream velocity can cross the erosion limits. An improper management of soot blowing itself causes the erosion of the tubes. Baffle plates can be used in high speed zone of boiler to keep the flue gas velocity within the specified ranges. Particle size can be controlled by maintaining pulverizers healthy. Reduced pulverizer capacity operation is essential in case of high ash & moisture content of coal, lower hard groove index and higher particle size (fineness) at its outlet.

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Recommendations

Coal Flow System Parameters 



  

Furnace Vacuum and differential pressures across the wind box, platen super heater, re heater, final super heater and economizer also influence the impacting particle velocity. Well maintained boiler fans are essential to keep various deferential pressures within the specified ranges. Sufficient clearance must be incorporated at the design stage itself on the basis of erosion severity. Tubes of higher erosion resistance should be used. Boiler should not be allowed to run at higher loads with very poor coal Air ingress through men holes, peep holes, inspection doors and cracks should be minimized.

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Recommendations

Coal Flow Systems’ Parameters 

-

SOx reduction has become essential for high sulfur coal based stations by making use of fuel desulphurization unit and putting the flue gas desulphurization units at the discharge of the electro static precipitator. To prevent ozone layer depletion, leakage of green house gases has to be stopped. CO2 is produced in abundance and increases quantity of the green house gases, which can be minimized either by forestation or by putting the decarburization plant before the chimney. Using low NOx Burners Space for flue gas de-sulfurization units Noise control

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Recommendations

General Recommendations 

Apart from the flow process improvement, following recommendations improve the over all performance of plant -

Grid frequency Coal and ash transport Plume effect Vents and safety valve

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Scope of the Work Thermal power plant operation and efficiency managers can make use of the results and recommendation, in accordance with chapter IV to VII. This also evolves useful suggestions to the equipment designers, engineering, procurement and construction managers, commissioning organizers, maintenance personnel and thermal power plant environmentalists. This work is also quite useful for those students of Applied Thermodynamics, Heat Transfer and Fluid Mechanics, whom so ever wish to be the ‘Power Engineer’ and decides to develop expertise in the field of operation and efficiency.

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Future Linkages Any thermal power plant can incorporate the mathematical model with their data acquisition system to give online guidance message to their operator. This work also gives many specific areas (coal parameters, cooling water flow and its inlet temperature to the condenser, flue gas exhaust temperature, O2 % in flue gas, equipment’s life, environmental protection etc), which attract the power plant researchers to know more and more about less and less. Dynamic models evolves lot of scope to researchers.

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Introduction

Future Linkages 

Integrated dynamic model of the thermal power plant processes of this work, can be further advanced for better analysis and examination of micro level cause and effect relationship for the optimization of the performance control, which invite research in future, linking the present work.



Informal validation of this work conducted on some unit of the utility sector was not permitted to be published due the classified stringent constrained with the power plant personnel, under the help and guidance of whom this studied was conducted and concluded. Project on formal validation of the proposals for any specific coal based thermal unit shall be a future linkage leading to the commercial benefit of reference unit.

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Conclusions and Recommendations Desired effect from the thermal power plant is electricity of standardized quantity and quality at the minimum consumption of input fuel oil and coal as the primary cause. To facilitate the first effect as heat from the primary cause of fuel supply, combustion supporting air and initial ignition energy has to be supplied to the furnace as an integral part of the primary cause. Liberated heat is the effect of combustion system, which cause steam generation.

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Conclusions and Recommendations- Cont. Similarly all intermediate effect become the cause for the next process and hence regulation of every process and monitoring its cause and effect in measurable parameters help in improving the performance of associated process. Reasonable guide lines have been provided to optimize the performance of most of the thermal power plant processes along with system wise integration of the same. Integrated mathematical model is capable of providing energy and exergy parameters to incorporate the same in dynamically managing the performance influencing parameters in accordance with causal relationships established in the dynamic model.

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Thank you *