Dr Mathieu Lucquiaudm.lucquiaud@ed.ac.uk

University of Edinburgh

Addressing technology uncertainties in power plants with post-combustion capture: The need for bespoke CCS

power plant models

20th March 2012,Mathematical Modelling and

Simulation of Power Plant and CO2 Capture

Future-proofing capture plants against technology developments

Capture technology is going to changeNeed for bespoke integrated power plant model to understand performance lock-in and future-proof design of CCS

Retrofitting existing power plants with CCS is a cost competitive option requiring lower capital costs than a new-build with CCS plant

Existing steam cycles may be retrofitted with post-combustion capture

Two examples

1

1

2

2 0

0

HPIP

condenser

LP LP

Heat recovery from

capture process

Solvent

reboiler

Desuperheater

back pressure

turbine

Floating pressure

Relocate

deaerator steam

extraction

Floating IP/LP crossover pressure retrofit with post-combustion capture

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

0

20

40

60

80

100

120

0 1 2 3 4 5 6 7 8 9

per

cen

tage

po

int

per

cen

tage

Stage location

IP turbine mechanical integrity for a floating IP turbine pressure retrofit

- 8 impulse stages - crossover pressure from 11 to 5.5 bara

relative increase in stage loading absolute loss of stage isentropic efficiency

Modeling considerations

Commercial software limitations for steam cycle model

Need to understand impact on mechanical integrity of steam turbines

Commercial software : black box approach to turbinesMechanical integrity not included

Future-proofing capture plants against technology developments

Capture technology is going to changeNeed for bespoke integrated power plant model to understand performance lock-in and future-proof design of CCS

Retrofitting existing power plants with CCS is a cost competitive option requiring lower capital costs than a new-build with CCS plant

Existing steam cycles may be retrofitted with post-combustion capture

Two examples

TODAY

A MODEL FOR CCS DEPLOYMENT

1st generation solvents

1st and 2nd generation solvents

2nd generation solvents and beyond

RETROFIT 1st UNITS WITH 2nd GENERATION SOLVENTS

Future-proofing capture plants against technology developments

Capture technology is going to change

Motivations for future-proofing power generation asset

Keep the plant license to operate by securing compliance with stricter environmental legislation New solvent becomes Best Available Technology (e.g. for lower carryover in flue gas)Level of capture has to be increased beyond ~ 90%

Future-proofing capture plants against technology developments

Capture technology is going to change

Motivations for future-proofing power generation asset

Keep the plant license to operate by securing compliance with stricter environmental legislation New solvent becomes Best Available Technology (e.g. for lower carryover in flue gas)Level of capture has to be increased beyond ~ 90%

Improve power plant economics Increase plant capacity (MW sent out for sale)Raise efficiencyReduce exposure to carbon costsReduce operating costs Enhance reliability and availability

Methodology – Step 1

What is a better solvent? Focus on electricity output penalty and overall process assessmentElectricity output penalty = (loss of generator output + compression power + ancillary power) / CO2 mass flow

Dedicated steam cycle and compression modelRelate electricity output penalty of new-build plants to key amine process parameters

- Solvent energy of regeneration, GJ/tCO2

- Solvent temperature of regeneration, ºC- Desorber and delivery pressure, bar- Ancillary power, kWh/tCO2

For more details: Lucquiaud and Gibbins (2011) On the integration of CO2 capture with coal-fired power plants: A methodology to assess and optimise solvent-based post-combustion capture systems, Chemical Engineering Research and Design, doi:10.1016/j.cherd.2011.03.003

1

1

2

2 0

0

HPIP

condenser

LP LP

Heat recovery from stripper overhead

reflux condenser and compressor

intercoolers

Solvent

reboiler

Desuperheater

Lucquiaud and Gibbins (2011)

New-build steam cycle with integrated post-combustion capture

DE

SO

RB

ER

pipeline

Condensate

Steam cycle

boiler feed water

Cooling water

Lucquiaud and Gibbins (2011)

Compression train model with heat integration into the power cycle

100

150

200

250

300

350

1 1.5 2 2.5 3 3.5 4

Elec

tric

ity

ou

tpu

t p

enal

ty (

kWh

/tC

O2

)

solvent thermal energy of regeneration (GJ/tCO2)

2 bar 4 bar 8 bar 16 bar

Reference line: EOP of 290 kWh/tCO2, desorber pressure of 2 bar, solvent energy of regeneration of 3.2 GJ/tCO2 and ancillary power for the amine plant of 20 kWh/tCO2.

Illustration of trade-offs between key amine process parameters

Solvent regeneration: 120ºC

Lucquiaud and Gibbins(2011)

Methodology – Step 2

Sensitivity of electricity output penalty to key solvent parameters Specific heat capacity Thermal stability Enthalpy of absorption Mass transfer

Reference plant: New-build unit with post-combustion captureReference solvent: 30%wt MEA

Objectives of methodology: - Generate a range of hypothetical solvents, variations in key

solvent parameters are not thermodynamically consistent- Assess performance for dedicated new-build plants for each

solvent- Identify pieces of equipment leading to performance lock -in

ST

RIP

PE

RSOLVENT

REBOILER

to stack

SC

RU

BB

ER

From boiler

Generic amine flowsheetObjectives are to characterise process parameters

as a function of key solvent properties

Desorber pressure

Reboiler temperature

Energy of regenerationAncillary power

Into dedicated

compression and power

plant model

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325

350

375

400

425

450

0.25 0.27 0.29 0.31 0.33 0.35 0.37 0.39 0.41 0.43 0.45

Ele

ctri

city

ou

tpu

t p

enal

ty (

kW

h/t

CO

2)

solvent lean loading (mol/mol)

+30%

+15%

-30%

-15%

reference

Future-proofing coal plantsSensitivity of performance to solvent heat capacity

Preliminary results

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3.25

3.5

3.75

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4.5

4.75

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80 90 100 110 120 130 140 150 160 170 180

bar

GJ/

tCO

2

Solvent reboiler temperature (ºC)

Thermal energy of regeneration Desorber pressure

Future-proofing coal plantsSensitivity of performance to solvent thermal stability

Preliminary results

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50

100

150

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250

300

350

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450

80 90 100 110 120 130 140 150 160 170 180

kW

h/t

CO

2

Solvent reboiler temperature (ºC)

Overall EOP EOP steam extraction EOP compression

Sensitivity of performance to solvent thermal stabilityExample of performance lock-in

Preliminary results

Area of performance lock-in with a non-

upgradeable steam turbine systems

Preliminary findings

Critical pieces of equipment and related solvent properties Steam turbine – solvent temperature and energy of regeneration Absorber – kinetics and mass transfer Compression - enthalpy of absorption, solvent temperature of

regeneration Desorber - enthalpy of absorption, solvent temperature of

regeneration Pipeline (if increased capture levels)

Modeling considerations

Commercial software limitations for integrated power plant model with carbon capture=> Commercial software: black box approach to solvent

thermodynamic properties=> Need for bespoke solvent property models – not necessarily thermodynamic consistent - for this work

Conclusions

Mechanical integrity of steam turbines not included in process software

Future-proofing options need to include the overall CCS process and not the amine plant in isolation.

Because future technology developments are by nature uncertain, there is a need for bespoke solvent property model

What is required:• Move away from black box commercial software• Use custom build model

Questions to the audience Open source integrated power plant CCS model validated by pilot

plant data, steady-state and dynamic What role of the UK CCS academic community? Intellectual property arrangements Ownership of model