aiche 2011 cogen screening 05

8/2/2019 AIChE 2011 Cogen Screening 05

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Cogen Screening for Improved Performanceand CO2 Reduction: Revisiting the R-Curves

[email protected]

2009 Shell Global Solutions (US) Inc. All rights reserved.

By Oscar Aguilar

March 2011

2/39Cogen Screening & Targeting for Improved Performance

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Presentation Outline

1. Introduction

4 Some Definitions

4 Cogen plant design/optimization

4 Challenges in Cogen design/retrofit

2. Cogen Screening & Targeting

4 Main features

4 Cogen configurations

4 Plant customization

4 Results comparison

3. Case Study

4 Cogen targeting for an existing site

4. Conclusions and Future Work


1. I N T R O D U C T I O N


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i Production of power and useful heat from a common energy source

4 Energy cascades to produce power and then meets a heating demand

i Cogeneration is an operating mode for individual units in a CHP system

4 Some steam may be directly delivered by a boiler while some is expanded in aturbine

Introduction

i A system that satisfies the heat and power demands from other processes

4 A combined cycle plant (CCP) produces heat, but only delivers power

4 Heat and power are utilities directly consumed by users (CHP = Utility Systems)

Combined Heat and Power (CHP) Plant

Cogeneration


Introduction

Overview of a CHP Plant

i A series of interconnected units transforming feeds into products (utilities)

4 Flows with direct cost implications: Fuel, Power, Water, Emissions (mainly)

GTg

HRSG

Cool Sys

CTgEM

LD

Deaer

BTg

Fan

BO

Cond

Treatment

Plant

pumpMTgProcess

Steam

GridElectricity

ProcessElectricity

Several

Fuels

Condensate

Returns

Raw Water +

Treat Chems

Shaft

Power

Heat

Rejection

Atmospheric

Emissions

Blowdown +

Water Rejects


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Introduction

CHP/Cogen Plant Optimization

i Objective: Determine the flowsheet conditions that Minimize Opex

4 Establish how to operate each piece of equipment

4 For an existing site, no changes in configuration considered

i Simulation / Optimization tools widely used for these applications4 Integrated approach is needed as all variables are interrelated

4 Streams across boundaries will establish cost implications

Many choices tosupply MP steam

LD

BO BOBO

MTgBTgBTg

GTg

HRSG Each option hascomplex plant-wide

implications!

Options for CHP Optimization:


Introduction

CHP/Cogen Plant Design (grassroots)

i Objective: Determine the flowsheet configuration that will minimize TotalCost (Opex + Capex)

4 Equipment types, number of units, sizes, interconnections

4 Plus the operational variables for a given design

iComplex problem, just a few non-commercial tools have been developed4 In general, no specialized tools to address this type of problems

i Typically addressed by trial-error using (operational) simulation/optim tools!

4 Non-systematic, tedious and time-consuming

BO

GTg

HRSG BO

BO

BO

GTg

HRSG

GTg

HRSG

GTg

HRSG

GTg

HRSG

BO

BOBO

BO

BO

GTg

HRSG

GT

HRSGBO BO BO

GTg

HRSG

GTg

HRSG

What types ofequipment?

How manyunits?

How to connectthem?

How to sizethem?

+All the

operationalissues

Options for CHP Design:


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Introduction

CHP/Cogen Plant Retrofit

i Objective: Determine changes in configuration that will minimize Opex +Capex (or just min Opex for a given Capex)

4 Also design + operational variables to be defined

i A special case of the design problem with some features fixed (existing)4 Reduced searching space compared to grassroots problems

i Again, typically involves a trial-error procedure using operational tools

Options for CHP Retrofit:


Introduction

Challenges in CHP/Cogen Design/Retrofit

i Commercial software mainly intended for operational applications

4 For existing plants with a fixed configuration

i Users have to figure out several configurations to test

4 Mainly based on experience, speculation on the best design

iTrial-Error is time consuming and can miss better opportunities4 May not make consistent comparisons

i Other concerns:

4 What is the best a plant can achieve? (e.g. economics-efficiency-emissions)

4 E/E/E performance trends with configuration changes

4 How to size units to match a certain configuration?

4 Can other designs with similar E/E/E performance save capex

A systematic approach needed to tackle CHP design/retrofit cases


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2. C O G E N S C R E E N I N G &T A R G E T I N G


Cogen Screening & Targeting

Main features

i Quick screening of promising Cogen configurations

4 Side-by-side comparison basis to identify best performers

i Consider Economics-Efficiency-Emissions at the same time

4 Conventionally, only one aspect taken into account

iSystematic guide to define the design/retrofit of the plant4 Practically all major options are compared

4 Ensure decisions are taken in the right direction

4 Top performers can be further evaluated for capex savings

i Customization options to represent different systems

4 Practical problems encountered in industry

i Alternatives beyond existing configuration for retrofit cases

Screening for New Designs + Targeting for Retrofit Cases


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Data Input

i Net steam (heating) demands/surplus and headers pressures

4 Up to 4 steam headers, temperature defined from steam turbines

HEADERS' CONDITIONS STEAM DEMANDS/SURPLUS

VHP Press = 630.0 4 VHP Steam

Tsat = 494.0 2 2 0.00 4

Steam Flow = From Process

Aprox VHP Heat = 0.00 2

HP Press = 400.0 psig HP Steam

Tsat = 448.2 F 2 -145.00 klb/hr

Steam Flow = From Process

Aprox HP Heat = 179.86 MMBtu/hr

MP Press = 250.0 psig MP Steam

Tsat = 406.0 F 1 207.00 klb/hr

Steam Flow = To Process

Aprox MP Heat = 248.86 MMBtu/hr

LP Press = 50.0 psig LP Steam

Tsat = 297.7 F 1 231.00 klb/hr

Target LP Temp = 320.0 F Steam Flow = To ProcessAprox LP Heat = 255.00 MMBtu/hr

VP Press = 0.597 psia

Temp = 85.0 F Net Stm Dem = 683.73 MMBtu/hr

293.00 klb/hr

Deaerator Press Dea = 21.6 psig Process BFW = 622.20 klb/hr

Tsat Dea = 261.4 F Condens Rtn = 404.00 klb/hr

BFW Final BFW T = 262.0 F Proc Wtr Dem = 511.20 klb/hr

psig

klb/hr

MMBtu/hr

F Surplus

Surplus

Demands

Demands



Data Input

i Other site data such as available fuel, power demands, prices

4 Fuel data, CO2 charges, CO2 from external power supplier

FUEL DATA

Fuel Type = 2

Fuel LHV wt = 46.28 1

Fuel LHV wt = 46.50 MJ/kg

Fuel LHV vol = 33.56 1

Fuel LHV vol = 51.00 MJ/Nm3 25C

Fuel HHV/LHV = 1.107 ( - )

Fuel HHV/LHV = 1.10 ( - )

CO2 Release = 2.589 kg-CO2/kg-fuel

CO2 Release = 2.50 kg-CO2/kg-fuel

CO2 Release = 55.942 1 1

CO2 Release = 130.00 g-CO2/ MJ-f uel LH V

Natural Gas

MJ/kg

MJ/Nm3 25C

LHVg-CO2/MJ-fuel

ECONOMIC DATA

Pow Imp Price = 58.28 $/MWh

Pow Exp Price = 58.28 $/MWh

Fuel Price LHV = 6.86 $/MMBtu

Econ Imp Eff = 40.2%

Econ Exp Eff = 40.2%

Onsite CO2 Chrg= 30.00 $/ton

Extern CO2 Chrg= 0.00 $/ton

Mkup Wtr Cost = 1.00 $/ton-water

Desal Wtr Value = 0.26 $/ton-water

Cooling Cost = 1.71 $/MWh

SITE DATA

Pow Demands = 36.00 MWe

Cond Return T = 122.0 F

Mkup Wtr Temp = 77.00 F

Include DA Stm = 2

Heat Calcs Ref 4

Exter Pow CO2 = 0.575 ton/MWh

Equiv Eff = 35.0%

Op Hours = 8760.0 hrs/yr

Cond Return Temp

No


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Main Configuration Options

1. Boilers Only (pure steam system)4 Stand-alone boilers supply steam, all power imported

2. Simple steam turbine extraction

4 Some power extracted in ST before delivering steam

3. Enhanced ST extraction4 Additional VHP header to extract more power from ST

4. Enhanced ST extraction + Condensing4 Extra steam sent to condensing ST

5. Boiler + Gas Turbine with Supp-Fired HRSG4 Steam: Boiler + HRSG with duct firing (SF), Power: GT + bck-press ST

4 Steam producers sized to exactly match demands

6. Boiler + GT w SF HRSG + Condensing4 Steam: Boiler + SF-HRSG, Power: GT + BP ST + condensing ST

4 Extra steam sent to condensing ST



Main Configuration Options (cont)

7. GT w SF-HRSG + Condensing4 All steam from SF-HRSG, extra steam to CT (CT=GT)

8. GT w SF-HRSG4 GT sized to exactly match steam demands (SF=GT)

9. GT w Unfired HRSG4 Larger GT sized to exactly match steam demands (SF=0)

10. GT w UF-HRSG + Condensing4 Additional steam sent to a condensing ST ( CT= GT)

11. GT w UF-HRSG + Exhaust Bypass4 Larger GT as not all exhaust gases produce steam

12. GT w UF-HRSG + Bypass + Condensing4 Even larger as some extra steam to CT


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Customization Options

i Performance parameters can be edited to represent different systems

4 Several units of each type can be represented (e.g. bulk efficiency)

4 Duct firing, condensing steam, GT exhaust bypass can be adjusted

INDIVIDUAL PERFORMANCE PARAMETERS

Boiler Eff = 85%

ST Elec/Mech Eff = 90%

Extra Cond Duty = 40% % Stm heating

Sup Firing = 100% %Max

STg1 Isen Eff = 80%

STg2 Isen Eff = 80%

STg3 Isen Eff = 80%

STg4 Isen Eff = 87%

GT Gross Eff = 34%WHB Correction = 1.000

Desal Water = 0.00 ton/MWh

Pow for Cooling = 2.00 kWe/MW-cool

BFW pmp Eff = 69%

GT Fuel Compress Pow = 5.0% %GT Gross Pow

BD Fraction = 3.0% of steam


3. C A S E S T U D Y C H P R E T R O F I T


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Case Study

Existing CHP plant

i Main driver: Reduce CO2/Energy/Opex cost-effectively

4 What is the best the plant can achieve? How to get there?

ai

DA

HR2

LD3

LD2 32CWP

BO2

Conden

Cool Sys

HPLP

GTg

P

PCW

P4

P3

P2

HR2GTg

HR2GTg

STG 6RGC 11RGC 3WSP 1ovhdC 4AbsP

32CWP1ChgP 7RGC M P LP


Case Study

Short-cut version of the system

i Performance parameters adjusted to represent the existing system

4 Letdown reflected as lower efficiency in ST power production

4 Drivers w/out electric motor option are part of steam demands

167.5 MMBtu/hr 0.0 / 1365.3 MMBtu/hr Temps OK!

125.0 klb/hr 136.0 MW

VHP 630.0 psig 499. 8 k lb/ hr 735. 9 F

494.0 F 0.0 MMBtu/hr

0.00 0.0 klb/hr 0.0 klb/hr

0.0 MW

HP 400.0 psig 638.6 F

448.2 F -179.9 MMBtu/hr

26.14 207.0 klb/hr 5.2 MW -145.0 klb/hr

4.4 MW

MP 250.0 psig 549.0 F

406.0 F 248.9 MMBtu/hr

52.75 417.8 klb/hr 0.0 MW 207.0 klb/hr

19.6 MW

LP 50.0 psig 320.3 F

Dea Steam 297.7 F 255.0 MMBtu/hr

184.5 klb/hr 147.3 klb/hr 231.0 klb/hr

10.1 MW

VP 0.597 psia

85.0 F 129.6 MMBtu/hr

BO

GTg

WHB

STg

STg

STg

STg

EQUIPMENT PERFORMANCE PARAMETER

Boiler Eff = 85%ST Elec/Mech Eff = 90%

Extra Cond Duty = 40% % Stm heating

Boiler Output = 20% %Tot steam flow

Sup Firing = 0% %Max

STg1 Isen Eff = 80%

STg2 Isen Eff = 80%

STg3 Isen Eff = 80%

STg4 Isen Eff = 87%

GT Gross Eff = 34%

WHB Correction = 1.000

Desal Water = 0.00 ton/MWh

Pow for Cooling = 2.00 kWe/MW-cool

BFW pmp Eff = 69%

GT Fuel Compress Pow = 5.0% %GT Gross Pow

BD Fraction = 3.0% of steam


11/21


Case Study

Results 1) Boilers Only

i Typically the reference case as simplest and lowest-capex design

4 All power from external grid, note de-aeration steam for process boilers

423.7 MMBtu/hr

326.8 klb/hr

HP 400.0 psig 644. 5 F

448. 2 F -179.9 MMBtu/hr

59.52 471.4 klb/hr -144.6 klb/hr

MP 250.0 psig 625. 6 F

406. 0 F 248.9 MMBtu/hr

34.26 271.3 klb/hr 200.1 klb/hr

LP 50.0 psig 598. 6 F

Dea Steam 297. 7 F 255.0 MMBtu/hr

66.3 klb/hr 205.0 klb/hr

LD

LD

BO

LDLD

OK: Steam is being supplied to the ProcessOnsite Pow = -0.5 MW

Power Import = 36.5 MW

Power Cost = 18.6 MM$/yr

Net Steam Duty = 324.0 MMBtu/hr

Net Process Stm = 260.5 klb/hr

Fuel Input = 423.7 MMBtu/hr

Fuel Cost = 25.5 MM$/yr

Cooling Duty = 0.0 MMBtu/hr

Desal Potential = 0.0 klb/hr

Cool Net Cost= 0.00 MM$/yr

Onsite CO2 = 219.0 kton/yr

Extern CO2 = 183.6 kton/yr

CO2 Cost = 6.57 MM$/yr

Pow/Heat Ratio = -0.005 Net Pow/Stm

Power Eff = 0.0% %

CHP Eff = 76.5% %

Net Opex = 50.64 MM$/yr


Case Study

Results 2) Simple ST Extraction

i Simple extraction enables some onsite power production

4 Steam temps and flows slightly different

OK: Steam is being supplied to the Process

Onsite Pow = 13.0 MW













Pow/Heat Ratio = 0.136 Net Pow/Stm

Power Eff = 9.2% %

CHP Eff = 77.0% %


*All STs shown on the diagram

478.3 MMBtu/hr Temps OK!

368.9 klb/hr

HP 400.0 psig 644. 5 F

448. 2 F -179.9 MMBtu/hr

26.09 206.6 klb/hr -144.6 klb/hr

2.1 MW

MP 250.0 psig 553. 1 F

406. 0 F 248.9 MMBtu/hr

38.76 306.9 klb/hr 0.0 MW 206.6 klb/hr

11.3 MW

LP 50.0 psig 320. 0 F



BO

STg

STg

BO


12/21


Case Study

Results 3) Enhanced ST Extraction

i Marginally lower opex w higher steam press for power production

4 Additional fuel cancels benefits of extra power

OK: Steam is being supplied to the ProcessOnsite Pow = 16.3 MW














Power Eff = 11.3% %

CHP Eff = 77.0% %


*STs expanding process steam surplus to LP not shown


368.9 klb/hr

VHP 600.0 psig 725. 8 F

488. 9 F 0.0 MMBtu/hr

0.00 0.0 klb/hr 0.0 klb/hr

0.0 MW

HP 400.0 psig 639. 2 F

448. 2 F -179.9 MMBtu/hr

26.13 207.0 klb/hr 5.2 MW -145.0 klb/hr

4.1 MW

MP 250.0 psig 549. 4 F

406. 0 F 248.9 MMBtu/hr

20.45 162.0 klb/hr 0.0 MW 207.0 klb/hr

7.4 MW

LP 50.0 psig 320. 0 F



BO

STg

STg

STg

BO


Case Study

Results 4) Enhanced ST Extraction + Condensing

i Extra steam expanded all the way to condensing

4 Higher opex as fuel/emissions costs offset savings in power
















Power Eff = 15.1% %

CHP Eff = 63.7% %




499.8 klb/hr

VHP 600.0 psig 725. 8 F

488. 9 F 0.0 MMBtu/hr

0.00 0.0 klb/hr 0.0 klb/hr

0.0 MW

HP 400.0 psig 639. 2 F

448. 2 F -179.9 MMBtu/hr

26.13 207.0 klb/hr 5.2 MW -145.0 klb/hr

4.1 MW

MP 250.0 psig 549. 4 F

406. 0 F 248.9 MMBtu/hr

36.97 292.8 klb/hr 0.0 MW 207.0 klb/hr

13.4 MW

LP 50.0 psig 320. 0 F



7.6 MW

VP 0.597 psig


STg

BO

STg

STg

STg

STg


13/21



184.5 klb/hr 22.8 MW

VHP 600.0 psig 184.5 klb/hr 725.8 F


0.00 0.0 klb/hr 0.0 klb/hr

0.0 MW

HP 400.0 psig 639.2 F

448.2 F -179.9 MMBtu/hr

26.13 207.0 klb/hr 5.2 MW -145.0 klb/hr

4.1 MW

MP 250.0 psig 549.4 F

406.0 F 248.9 MMBtu/hr

20.45 162.0 klb/hr 0.0 MW 207.0 klb/hr

7.4 MW

LP 50.0 psig 320.0 F



BOGTg

WHB

STg

STg

STg

Case Study

Results 5) Boiler + GT w SF-HRSG

i Opex decreases as boiler steam share is reduced (transition to pow export)

4 GT+SF-HRSG is more efficient to produce steam and power than BO+ST


Power Import = -2.0 MW

Power Cost = -1.00 MM$/yr









Extern CO2 = -9.8 kton/yr



Power Eff = 22.5% %

CHP Eff = 78.9% %




Case Study

Results 6) Boiler + GT w SF-HRSG + Condensing

i GT+HRSG reduces opex, but BO+CT is not cost-effective

4 Opex varies with boiler steam share and % duct firing in HRSG
















Power Eff = 26.0% %

CHP Eff = 67.6% %




249.9 klb/hr 31.5 MW

VHP 600.0 psig 249. 9 k lb/ hr 725. 8 F

488. 9 F 0.0 MMBtu/hr

0.00 0.0 klb/hr 0.0 klb/hr

0.0 MW

HP 400.0 psig 639. 2 F

448. 2 F -179.9 MMBtu/hr

26.13 207.0 klb/hr 5.2 MW -145.0 klb/hr

4.1 MW

MP 250.0 psig 549. 4 F

406. 0 F 248.9 MMBtu/hr

36.97 292.8 klb/hr 0.0 MW 207.0 klb/hr

13.4 MW

LP 50.0 psig 320. 0 F



10.1 MW

VP 0.597 psia

85.0 F 129.6 MMBtu/hr

BO

GTg

WHB

STg

STg

STg

STg


14/21


Case Study

Results 7) GT w SF-HRSG + Condensing

i Lower opex without boilers, but condensing still impacts opex

4 Opex varies with condensing duty and % duct firing in HRSG















Power Eff = 34.6% %

CHP Eff = 68.1% %



260.6 / 628.2 MMBtu/hr Temps OK!

61.9 MW

VHP 600.0 psig 499. 8 k lb/ hr 725. 8 F

488. 9 F 0.0 MMBtu/hr

0.00 0.0 klb/hr 0.0 klb/hr

0.0 MW

HP 400.0 psig 639. 2 F

448. 2 F -179.9 MMBtu/hr

26.13 207.0 klb/hr 5.2 MW -145.0 klb/hr

4.1 MW

MP 250.0 psig 549. 4 F

406. 0 F 248.9 MMBtu/hr

36.97 292.8 klb/hr 0.0 MW 207.0 klb/hr

13.4 MW

LP 50.0 psig 320. 0 F



7.6 MW

VP 0.597 psia


GTg

WHB

STg

STg

STgSTg

STg


Case Study

Results 8) GT w SF-HRSG

i Eliminating boilers and condensing reduces opex even further

4 Opex varies with % duct firing in HRSG
















Power Eff = 31.0% %

CHP Eff = 80.4% %



192.4 / 463.8 MMBtu/hr Temps OK!

45.7 MW

VHP 600.0 psig 368. 9 k lb/ hr 725. 8 F


0.00 0.0 klb/hr 0.0 klb/hr

0.0 MW

HP 400.0 psig 639.2 F

448.2 F -179.9 MMBtu/hr

26.13 207.0 klb/hr 5.2 MW -145.0 klb/hr

4.1 MW

MP 250.0 psig 549.4 F

406.0 F 248.9 MMBtu/hr

20.45 162.0 klb/hr 0.0 MW 207.0 klb/hr

7.4 MW

LP 50.0 psig 320.0 F



GTg

WHB

STg

STg

STg


15/21


Case Study

Results 9) GT w UF-HRSG

i Unfired HRSG allows installing a larger GT for additional power

4 >Power Eff, but


16/21


Case Study

Results 11) GT w UF-HRSG + Bypass

i GT size fully decoupled from steam demands and condensing

4 More GT output, but Opex

OK: Steam is being supplied to the ProcessOnsite Pow = 203.0 MWe

Power Import = -167.0 MWe













Power Eff = 34.7% %

CHP Eff = 50.9% %



Bpass = 50.0% 0.0 / 1995.7 MMBtu/hr Temps OK!

196.5 MW

VHP 600.0 psig 368. 9 k lb/ hr 725. 8 F

488. 9 F 0.0 MMBtu/hr

0.00 0.0 klb/hr 0.0 klb/hr

0.0 MW

HP 400.0 psig 639. 2 F

448. 2 F -179.9 MMBtu/hr

26.13 207.0 klb/hr 5.2 MW -145.0 klb/hr

4.1 MW

MP 250.0 psig 549. 4 F

406. 0 F 248.9 MMBtu/hr

20.45 162.0 klb/hr 0.0 MW 207.0 klb/hr

7.4 MW

LP 50.0 psig 320. 0 F



0.0 MW

VP 0.597 psia

85.0 F 0.0 MMBtu/hr

GTg

WHB

STg

STg

STgSTg

STg


Case Study

Results 12) GT w UF-HRSG + Bypass + Condensing

i Even larger GT for the same %bypass, but penalty from condensing too

4 A way to produce more power if it were cost effective
















Power Eff = 35.7% %

CHP Eff = 47.6% %



Bpass = 50.0%


0.0 klb/hr 266.2 MW

VHP 600.0 psig 499.8 klb/hr 725.8 F


0.00 0.0 klb/hr 0.0 klb/hr

0.0 MW

HP 400.0 psig 639.2 F

448.2 F -179.9 MMBtu/hr

26.13 207.0 klb/hr 5.2 MW -145.0 klb/hr

4.1 MW

MP 250.0 psig 549.4 F

406.0 F 248.9 MMBtu/hr

36.97 292.8 klb/hr 0.0 MW 207.0 klb/hr

13.4 MW

LP 50.0 psig 320.0 F



7.6 MW

VP 0.597 psia


GTg

WHB

STg

STg

STg

STg

BO


17/21


Case Study

Performance Results: Improved R-Curves

i Conventional R-curves only for limited configurations and equipment sizes

4 Proposed approach customizable to represent different systems

i Portraying the efficiency trends of (practically) all options

R-Curves for diff CHP Configurations

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00

Power/Heat Ratio, MWe/MWth

Efficiency CHP Efficiency

Power Efficiency

BO+ST

BO+GT+SF+ST

BO+ST+CT

GT+SF+STGT+SF+ST+CT

GT+UF+ST+CT

GT+UF+ST+Bpass


Case Study

Performance Results: Improved R-Curves

i Depending on specific site conditions, trends can be different

4 Configurations and sizes will affect site performance

4 E.g. condensing reduces CHP efficiency (but improves power efficiency)

R-Curves for diff CHP Configurations

GT+SF+ST

BO+GT+SF+STBO+ST

BO+ST+CT

GT+SF+ST+CT GT+UF+ST+CT

GT+UF+ST+Bpass

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00


CHP

Efficiency


18/21


Case Study

Economic Results: E-Curves

i Efficiency not always equivalent to cost-effectiveness

4 Decisions should be also supported by economics

i Note the divergent trends in fuel and power costs

Economic Curves for diff CHP Configurations

-200

-150

-100

-50

0

50

100

150

200

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50


A

nnualCost,MM$/yr

Tot Cost

Fuel Cost

Pow Cost

BO+ST

BO+GT+SF+STBO+ST+CT

GT+SF+ST

GT+SF+ST+CT

GT+UF+ST+CTGT+UF+ST+Bpass


Case Study

Fuel Chargeable to Power: Fuel-Power Curves

i How much extra fuel to produce additional power

4 Onsite cost of producing power

BO+BST

BO+GT+100%SF+BST

GT+50%SF+BST

BO+BST+CST

GT+100%SF+BST

GT+100%SF+BST+CST

GT+0%UF+BSTGT+0%UF+BST+CST

GT+0%UF+BST+Bpass

0

10

20

30

40

50

60

70

80

90

0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0 800.0

ExtraPowerCost,$/MWh

Onsite Power, MWe

Extra Power Cost for different CHP ConfigurationsBO = Stand Alone

Boiler

BST = Back-PressSteam Turbine

CST = CondensingSteam Turbine

GT = Gas Turbine100%SF = Fully fired

HRSG0%UF = Unfired HRSGBpass = Bypass HRSG

GT Exhaust

Note 1) BO+BST+CST may show aconstant value since BO+BST is taken

as reference

Note 2) For lower site power, extra costdrops down t o zero


19/21


Case Study

Economic Results: E-Curves

i This approach provides insight to the design process

4 E.g. even if efficiency is reduced, condensing can be cost-effective

i Note that min Opex happens when eliminating duct firing

4 Largest GT size without bypassing the HRSGEconomic Curves for diff CHP Configurations

GT+SF+STBO+GT+SF+ST

BO+ST

BO+ST+CT

GT+SF+ST+CT

GT+UF+ST+CT

GT+UF+ST+Bpass

0

10

20

30

40

50

60

70

80

90

0.00 0.50 1.00 1.50 2.00 2.50 3.00


AnnualCost,MM$/yr


Case Study

CO2 Emissions: CO2-Curves

i To identify the design options that minimize CO2 emissions

4 E.g. impact of CO2 taxes or cost to reduce the emissions

i Trends in onsite and overall CO2 footprint

CO2 Curves for diff CHP Configurations

-1500

-1000

-500

0

500

1000

1500

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50


CO2Emissions,

kton/yr

Onsite CO2

Extern CO2

Tot CO2

BO+ST

BO+GT+SF+STBO+ST+CT

GT+SF+ST

GT+SF+ST+CT

GT+UF+ST+CTGT+UF+ST+Bpass


20/21


Case Study

CO2 Emissions: CO2-Curves

i Trends can significantly change with individual factors

4 Overall emissions vary with internal and external power efficiencies


GT+SF+ST

BO+GT+SF+ST

BO+ST

BO+ST+CT

GT+SF+ST+CT

GT+UF+ST+CT

GT+UF+ST+Bpass

0

50

100

150

200

250

300

350

400

450

500

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50


CO

2Emissions,

kton/yr

Tot CO2


Case Study

CO2 Emmissions: CO2-Curves

i Impact of increasing external efficiency from 35% to 50%

4 In this case, loading the CT increases overall CO2

4 Less emissions by importing power from a more efficient external source


GT+SF+ST

BO+GT+SF+STBO+ST

BO+ST+CT

GT+SF+ST+CT

GT+UF+ST+CT

GT+UF+ST+Bpass

0

100

200

300

400

500

600

700

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50


CO2Emissions,

kton/yr

Tot CO2


21/21


Conclusions & Future Work

h An integrated approach for screening CHP options have been proposed

4 Blending standard calculations with novel features

h Consistent comparison framework to quickly identify promising options

4 Effect of different configurations and equipment sizes on performance

4 Performance: Fuel usage (efficiency), economics, CO2 emissions (E/E/E)

4 Alternatives can be evaluated side-by-side on a consistent basis

4 Can be tailored to represent a specific site or type of plant

h This approach guides the design process in a systematic way

4 Document and support decisions (in the right direction), rather than trial-error

h Screening tool for new designs / Targeting tool for existing sites

4 Best configurations for a new design / best an existing site can achieve

h Still a work in progress:

4 Need more cases to be tested

4 Include other options (desalination, capex)

CHP Screening for Improved

Performance and CO2 Reduction:Revisiting the R-Curves

S i M ti 2010

[email protected]

By Oscar Aguilar

San Antonio, TX March 2010

aiche 2011 cogen screening 05

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