How To Save Energy Through Enhanced Automation

How to Save Energy Through Enhanced Automation

AIChE Spring Meeting 2008 Douglas White Emerson Process Management

Standards Certification Education & Training Publishing Conferences & Exhibits

Speaker Doug White Principal Consultant and Vice President, APC Services Advanced Applied Technologies Process Systems and Solutions Emerson Process Management Many years experience designing, justifying, installing and commissioning advanced real time computer applications in the process industries. ©2008 Emerson Process Management

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Natural Gas Prices

Natural Gas Prices (Henry Hub) 14 12

$/ MMBTU

10 8 6 4

Forecast

2 0 Jan-93

Jan-95

Jan-97

Jan-99

Jan-01

Jan-03

Jan-05

Jan-07

Jan-09

Date

©2008 Emerson Process Management

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Process Energy Usage Value; 10% Energy Reduction; $/ Ton ($7/ MMBTU)

Process Energy; MM BTU/ Ton Petroleum Refining

4.4

Integrated Pulp/Paper Mill Cement Production Chemicals Ethylene Polyethylene EDC PVC EO

e g r Ethylbenzene a L Styrene EG

C t s

ti

29.0

s o C e l b a ! l l s t o r n t la n o P

©2008 Emerson Process Management

M n

t s o

3.1 20.3

7.9

5.5

7.1

5.0

6.7

4.7

9.4

6.6

4.0

2.8

6.2

4.3

7.1

5.0

2.9

2.1

38.8

27.2

4

Session Objective Present some case studies of the many ways that automation, advanced automation and asset management can save energy in process plants

©2008 Emerson Process Management

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Outline • How is energy used in process plants? • How can automation help save energy? • How do we implement an energy reduction program?

©2008 Emerson Process Management

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General Process Site Energy Flow Process Steam Drives

Purchased Steam

Purchased Fuel Raw Material As Fuel

Purchased Power

Central Steam Production

Process Heating/ Cooling

Process Steam Generated

Process Fired Equipment Central Power Production

Power Plant Process and Offsites

Export Steam

Process Direct Fuel Usage

Export Fuel Process Misc Electric Usage

Process Electric Drives ©2008 Emerson Process Management

Export Power

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“Average” Chemical Site Energy Flow Process Steam Drives

Purchased Steam

Purchased Fuel

Central Steam Production 32%

37%

Purchased Power

Process Steam Generated

Process Fired Equipment

63%

Raw Material As Fuel

Process Heating/ Cooling

Central Power Production

Process Direct Fuel Usage

27%

Process Misc Electric Usage

4%

Power Plant Process and Offsites

22%

Export Steam

Process Electric Drives

©2008 Emerson Process Management %-Equivalent BTU basis (Including losses) on total input

Export Fuel

18%

Export Power 1%

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Integrated Pulping Paper Mill Energy Flow Process Steam Drives

Purchased Steam

Purchased Fuel

Central Steam Production 62%

Process Heating/ Cooling

42% 5%

Raw Material As Fuel 50%

Central Power Production

Process Steam Generated

Process Fired Equipment

Process Direct Fuel Usage

Process/ Fac Misc Electric Usage 4%

25%

Purchased Power 8%

Power Plant Process and Offsites

29%

Export Steam

Process Electric Drives

Emerson Process Management %-Equivalent BTU©2008 basis (Including losses) on total input

Export Fuel

Export Power

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Oil Refinery Energy Flow Process Steam Drives

Purchased Steam 1%

Purchased Fuel

Central Steam Production

Process Heating/ Cooling

34%

25% 44%

Raw Material As Fuel 64%

Central Power Production

6%

Process Steam Generated

Process Fired Equipment

Process Direct Fuel Usage

Process Misc Electric Usage

5%

Purchased Power 10%

Power Plant Process and Offsites

15%

Export Steam

Process Electric Drives

©2008 Emerson Process Management %-Equivalent BTU basis (Including losses) on total input

Export Fuel

Export Power

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Reducing Plant Energy Costs •

Reduce Usage – Individual Equipment – Improve Efficiencies – Boilers, Heaters, kilns – Maximize Useful Recovery - Preheat – Minimize Losses – Cooling water – Minimize Motor Losses – Unit Savings – Optimize Process Unit Operations – Distillation/ Fractionation – Maximize Waste Heat Recovery – Minimize waste/ off spec – Site/ Multi – Unit Savings – Minimize Steam Losses and Downgrading – Switch of steam drives for electric or vice versa – Seasonal effects

•

Reduce Cost of Production and Purchase – Fuel Substitution – Generation Maximization – Boiler and Turbine Allocation – Electric Purchase Optimization

Automation and Advanced Automation are the keys to effective operation and minimum ongoing energy usage ©2008 Emerson Process Management

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Process Industry Energy Saving Primary Targets

• Fired Heaters • Distillation/ Fractionation • Central Power and Steam Production

©2008 Emerson Process Management

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How can Automation Reduce Energy Usage?

©2008 Emerson Process Management

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Variability – Potential Energy Savings Example Heater Stack O2 Variability

12

800

11

700

10 600 9 500

8

O2, %

7

400

6

Fuel Gas Flow

300

5 200 4

2 8:00

100

Target

3

0 9:00

10:00

11:00

12:00

13:00

14:00

Time ©2008 Emerson Process Management

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Energy Savings Through Automation – Target Areas Site- Wide

Process Unit Draft Control

O2

Equipment

FI

TC PI

M ass Cont Dens FF

FC 3-5

FT 3-5 Bottoms

PI

Fuel Gas

Device, Loop ©2008 Emerson Process Management

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Saving Energy – Automation Examples Improved Loop/ Multi-loop Control Performance FC 3-5

FT 3-5

Improved Measurements

Better Control Valve Performance

©2008 Emerson Process Management

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Component Heating Values Fuel Gas Component Heating Value Component

Heat of Combustion kcal/ NM3 (gross)

Heat of Combustion kcal/ kg (gross)

Hydrogen

3020

33910

Methane

9520

13280

Ethane

16820

12410

Propane

24320

12040

Butane

32010

11840

Control Fuel Flows By Mass Instead of Volume

©2008 Emerson Process Management

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Energy Savings From Improved Measurements – Hydrogen Plant

Mass Measurement

Ref: MMI WP_00724

Objective: Control S/C ratio as close to 3.2 as possible but avoid going below Disturbance: Fuel gas C1 77 – 85%; C2 6.8 – 15; N2, CO also fluctuate Test: Normal orifice plus GC – max error 0.2; MMI – max error – 0.02 Benefits: Moving 0.2 ratio closer to limit worth 8 BTU/SCF of H2; 80 MMSCFD plant; $7 MM BTU gas – ©2008 Emerson Process Management

$1.6 MM per year

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Energy Losses Through Bypassing

F2 TC

TC

TC

Fuel F1 F1/(F1+ F2)

Heat Loss Increase -%

0.14

3.2

0.25 0.4

Reference: Shinskey;

6.8

Energy Conservation Through Automation

14.3 ©2008 Emerson Process Management

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Energy Savings – Equipment Level Draft Control

•Improved Multi-Loop Control – Advanced Control

O2

FI

TC PI

M ass Cont Dens FF

PI

Fuel Gas

•Improved Performance Monitoring •Improved Diagnostics

©2008 Emerson Process Management

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Steam System Control Issues Vent PIC1

PIC3

750 psig

FIC2

TGA

FIC1

Objective: Maximum Flow to TGA

TGB

Users

Vent PIC4

50 psig

PIC2

Condensate PRC1

psig 757.0 754.0 751.0 748.0 745.0 0

4500

9000 Mean=750.814 3Sig=3.242

13500

18000 Sec

4500

9000 Mean=212.955 3Sig=6.987

13500

18000 Sec

FRC1

mlb/hr 320.0 315.0

Problem: Pressure Instability in Header Limited Flow to TGA

310.0 305.0 300.0 0

©2008 Emerson Process Management

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Steam System Diagnosis – Valves and Tuning PRC 1 OP

%Out 60.00 58.00 56.00

5% 5%

54.00 52.00 4800

220sec sec 220

5200

5600 Mean=56.0123 3Sig=9.381

6000

6400 Sec

Sec mlb/hr 225.9

FRC2

221.8 217.8 213.7 209.6 4800

psig 752.9

5200

5600 Mean=114.983 3Sig=19.7

6000

6400 Sec

PRC1

Flow controller to TGB has 5% deadband; induces limit cycle in pressure Correction: Fix TGB turbine governor/ steam valve

751.8 750.6 749.5 748.3 4800

5200

5600 Mean=650.814 3Sig=3.242

6000

6400 Sec

Tune controllers as system – not individually

Estimated value of increased flow to TGA - $3000/ day ©2008 Emerson Process Management

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Fired Heater Controls

©2008 Emerson Process Management

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Combustion Control

©2008 Emerson Process Management

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Heater/ Boiler Combustion Control Savings

$/ Yr Savings 100 MM BTU/ Hr $7/ kSCF Gas 400 F Stack Gas Rise $600,000 $500,000 $400,000 $/ Yr $300,000 $200,000 $100,000 $0 2

3

5

7

10

% O2

©2008 Emerson Process Management

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Typical Heater APC Package HIC 353D

PIC 359D

PIC 357D

TI 071 AIC CO 354D

H306

FIC 101

TI 072 FIC 102

TIC 362D

FIC 104 (Up to 4)

Combustion Control

TI 067

TIC 361

TI 069

TI 073 FIC 103

MPC Block

AIC O2 356D

TI 069

TI 043

TI 070

TI 075

Pass Balance

Fuel Demand

Air Demand

FIC 361

©2008 Emerson Process Management

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Excuses For Not Improving Heater Controls • Damper/ Air controls are not reliable – Answer: Add positioners to dampers, with feedback to control system; Analyze and fix controller problems

• Don’t have online analyzer/ can’t maintain them – Answer: Analyzers are cheaper and more reliable – particularly mass flow meters. With higher fuel costs, they are well justified.

©2008 Emerson Process Management

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Distillation Controls

©2008 Emerson Process Management

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Typical Distillation Column PC

LC

FC

FC

Feed, F 20,000 BPD $50/ Bbl

Distillate, D < 5%C5 ;$45/ Bbl AR > 5%C5; $38/ Bbl

Reflux, R TC FC

LC

Bottoms, B < 5 %C4 ; $70/ Bbl > 5%C4; $50/ Bbl

Reboiler, E $36/ Bbl FOE AC

©2008 Emerson Process Management

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Distillation Column Control Savings Cost Per Year Excess Reflux 20000 BPD Stabilizer Column $10/ MM BTU Steam $700,000 $600,000 $500,000 $400,000 $/ Yr $300,000 $200,000 $100,000 $0 5

10

25

50

% Excess Reflux

©2008 Emerson Process Management

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Column Pressure Effect Relative Reboiler Cost Per Year Column Pressure Effect 20000 BPD Stabilizer

120% 100% 80% 60% 40% 20% 0% 100

120

140

160

180

200

Pressure, PSIA Basis: Constant Separation Modeled With ChemSep Peng Robinson Equation of State

©2008 Emerson Process Management

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Energy Savings – Site Wide

•Site Energy/ Utility Management •Steam System Control •Fuel System Control ©2008 Emerson Process Management

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Energy Management and Optimization System

©2008 Emerson Process Management

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Plant Utility Systems – Many Opportunities for Savings BFW FB1

FB2

FB3

WHB1

WHB2

GT1

• Many interacting decision variables HRSG

• Large number of constraints Vent

FG

Unit 1

Unit 2

PRV

ST1

HPS

ST2

Vent

MPS PRV

Demin Plant

Unit 3

Unit 4

Unit 5 LPS

Make-Up

Vent

Condensate

©2008 Emerson Process Management

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Optimizer Decisions • Which boiler(s) should I run? What load? • How much electricity should I produce? Buy? Sell? Is it economic to run the steam turbine? • Which fuel should I buy? How much? • Should I be using more steam drives or more electric drives? • When will efficiency gain from maintenance balance the cost of shut down for this equipment? • How does my actual compare with plan corrected to standard conditions?

©2008 Emerson Process Management

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Full Utility Optimization BFW FB2

FB1

FB3

WHB1 WHB2 GT1

• Many interacting decision variables HRSG

• Large number of constraints

FG HPS

Unit 1

Unit 2

PRV

ST1

ST2

MPS PRV

Demin Plant

Unit 3

Unit 4

Unit 5 LPS

Make-Up

Condensate ©2008 Emerson Process Management

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Overall Energy Optimization Strategy • • • • • •

Continuously Calculate Production Costs Over Load Range with Current Fuel Mix Incorporate Constraints on All Equipment Decisions Made Through Rule Based Logic Boiler Load Allocation – Distribute Steam Production Based on Cost and Constraints Turbine Load Allocation – Distribute Steam for Minimum Cost with Constraints Tie-Line Control – Control Electrical Purchase Based on Economic Decision and Constraints

©2008 Emerson Process Management

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Boiler Load Allocation

©2008 Emerson Process Management

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Load Allocation 90

How to provide 200 kpph steam? Boiler Efficiency

No. 4

Load Most Efficient

No. 3 85 Minimum Cost No. 2 Equal Loads

80

25,000

50,000 ©2008 Emerson Process Management Boiler Load, lb/hr

No. 1

75,000 50

Energy Savings via Site Energy Balance Flue Gas; 200 F BlowDown 384 pph

Flue Gas; 200 F

1600 psia; 940 F 19200 pph

Power 1000 KW

Fuel 24,393 kBTU/ hr

200 psia

Make-Up 384 pph

Condensate

BlowDown 271 pph

0 kBTU/hr Steam; 125 psia 20,200 pph

1600 psia; 940 F 13550 pph

Power 1000 KW

Fuel 18510 kBTU/ hr

200 psia 9600 pph

Make-Up 271 pph

Naïve calculation, value 125 psia steam reduction = 1000 x (1031 Btu/ lb (ΔHv) ÷ 0.7(eff))x $7/MMBtu (Fuel) = $10.31 per klb

Condensate

3754 kBTU/hr Steam; 125 psia 10,100 pph

Reference: Kinney; Energy Conservation in Process Industries

Actual site value 125 psia steam reduction = $4.08 per klb ©2008 Emerson Process Management

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Typical Energy Management System Benefits

1 – 3 % Overall site utility cost savings!

©2008 Emerson Process Management

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Example

©2008 Emerson Process Management

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Utilities Example – Biomass Power Boiler • • •

Paper mill 160k PPH Fluidized-bed Boiler Fuels: – – – –

•

Sludge Wood waste Tires Fuel gas

Incentives: – Maximize use of cheap fuels (Tires & Wood) – Burn all the sludge to minimize land fill – Maximize steam production

©2008 Emerson Process Management

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Solid Fuel Composition Control Tire Derived Fuel (TDF)

Sludge Presses

TDF Target

M

FC

VSM

Sludge Recovery Hopper

Sludge Bin

FC

Sludge Target

FC M

Bark Yard

FC

RSP

RSP

HC

Bark Target

WS

Solid Fuel Bin

HC Silo 1

Silo 2

VSM

RSP

HC

VSM WS

RSP

WS

©2008 Emerson Process Management

HC

Solid Fuel To Boiler 59

Boiler Control To ID Fan To ID Fan Speed Control

PC

FC

Combustion Control

Solid Fuel

Boiler

Solid Fuel

Secondary Air Blower

FC

Overfire Air Ports (18) FC

Primary Air Blower

FC

Load Burners (4) FC

RSP

TC Avg

Fuel Gas

NC

FC

Lance Burners (16)

TI A-F

Air Preheater Ash Screws (2) To Ash Handing

HS

M

M ©2008 Emerson Process Management

HS

TI 60

Boiler Process Control Issues • Varying water in sludge • Long delay & lag times (20 – 60 minutes) to change fuel composition • Fuel composition time constants are a function of fuel bin level • Solid fuel composition in fuel bin is unknown • Bed temperature constraints (max & min) • Multiple operators controlling same unit • Different operating philosophy used by each shift ©2008 Emerson Process Management

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Solid Fuel Composition Control Tire Derived Fuel (TDF)

Sludge Presses

MPC Block

TDF Target

M VSM

Sludge Recovery Hopper

Sludge Bin

FC

Sludge Target

FC M

Predicted BTU Content

Bark Target

Bark Yard RSP

RSP

HC

WS

FC

Solid Fuel Bin

HC Silo 2

Silo 1 VSM

RSP

HC

VSM WS

RSP

WS

©2008 Emerson Process Management

HC

Solid Fuel To Boiler 62

Boiler Control To ID Fan MPC Outputs

To ID Fan Speed Control

PC

FC

Combustion Control

Solid Fuel

Boiler

Solid Fuel

Secondary Air Blower

FC

Overfire Air Ports (18) FC

Primary Air Blower

FC

Load Burners (4) FC

RSP

TC Avg

Fuel Gas

NC

FC

Lance Burners (16)

TI A-F

Air Preheater Ash Screws (2) To Ash Handing

HS

M

M ©2008 Emerson Process Management

HS

TI 63

Power Boiler Sludge

50

Key

40

Current Average

30

SLDG New Average

20 Max Sustainable

10

©2008 Emerson Process Management

1 4/

19

/0

1 3/

30

/0

1 10 3/

18 2/

/0

1 /0

1 /0 29 1/

1/ 9/ 01

00

0 12 /2 0/

TPH

60

64

45 40 35 30 25 20 15 10 5 0

Key Current Average

BARK

New Average

©2008 Emerson Process Management

4/ 19 /0 1

1 3/ 30

/0

1 3/ 10 /0

1 /0 18 2/

1/ 29 /0 1

Max Sustainable

1/ 9/ 01

12 /2 0/ 00

TPH

Power Boiler Bark Fuels

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Power Boiler APC Benefits Difference in Hourly Costs & (Savings)

Power Boiler Natural Gas

Total Savings

$2.22

Sludge Disposal

$56k / mo

($23.04)

Sludge Ash Disposal

$9.18

TDF

$0.46

TDF Ash Disposal

$0.00

Waste Wood

$26.91

W Wood Ash Disposal Total

$0.77 $16.50

Package Boilers Displaced Natural Gas

($98.42)

Net Savings, $/Hr

($81.92)

$672k / yr Project Justified: • Replacement of required pneumatic instruments • DCS Hardware / Software • APC Tools • Turnkey Engineering Services

©2008 Emerson Process Management

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Issues in Evaluating Plant Energy Usage • Unit energy usage depends on production rate • Unit energy usage variance dependent on production rate • Need to correct to standard unit conditions

©2008 Emerson Process Management

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Unit Energy Usage

Specific Energy Usage Btu /Bbl

Energy Usage Btu

0

50

100

Throughput - % Max Capacity ©2008 Emerson Process Management

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Energy Usage - Example 80.00

70.00

60.00

50.00

MMBTU/Hr 40.00

30.00

20.00

10.00

0.00 0.00

1.00

2.00

3.00

4.00

5.00 6.00 Production ©2008 Emerson Process Management T/Hr

7.00

8.00

9.00

10.00

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Unit Energy Usage

x

Variance Increases at Lower Rates

x x

x

x

x

Specific Energy Usage Btu /Bbl

x x

x x x x

x

x

x x

x

x x

x

x x

0

Confidence Limits

x

x

x

50

x

x x

x

100

Throughput - % Max Capacity ©2008 Emerson Process Management

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Unit Energy Usage - Example 10.00

9.00

8.00

7.00

MMBTU/Ton

6.00

5.00

4.00

3.00

2.00

1.00

0.00 0.00

1.00

2.00

3.00

4.00

5.00

6.00

©2008 Emerson Process Management

Production

7.00

8.00

9.00

10.00

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Excuses for Doing Nothing • Not enough manpower - Too busy doing other things • Our plant is special – analysis based on other sites doesn’t apply • We run our plant well already, there won’t be any big savings found • Ostrich - (If we find something obvious, management will ask why we didn’t find it before)

©2008 Emerson Process Management

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Summary • Energy is the largest controllable cost in process operation – it’s efficient production and use are keys to plant profitability • Automation and Advanced Automation are keys to effective use and management of energy in the plant • Implementation of a program to save energy requires a disciplined approach to evaluation and analysis

©2008 Emerson Process Management

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Questions? Comments?

[email protected] More material on subject: http://www.emersonprocess.com/solutions/services/aat

©2008 Emerson Process Management

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