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Integration Studies of

Post-Combustion CO2 Capture by

Wet Chemical Absorption into

Hamburg University of Technology

Institute of Energy Systems

Wet Chemical Absorption into

Coal-fired Power Plant

4th International Conference on Clean Coal Technologies

17 – 21 May 2009. Dresden. Germany

Imo Pfaff

Jochen Oexmann

Alfons Kather

Institute of

Energy Systems

Session: Carbon Capture Technolgies (II)


Institut of Energy Systems

Post-combustion CO2 capture by wet chemical absorption processes

+ Based on the conventional steam power plant process

+ Retrofittable

− Relatively high efficiency penalty

Efficiency losses due to

▸ CO2 capture unit

• Heat demand to regenerate solvent

Background

Other CO2

compression

Power

Structure of efficiency losses

• Heat demand to regenerate solvent

• Power demand

▸ CO2 compression

▸ Further auxiliary loads (fans etc.)

Focus of most studies retrofit integration

�This study: focus on Greenfield

▸Overall power plant optimization possible

2

CO2 capture unit

Heat



Reference power plant process

▸ Concept study reference power plant North Rhine-Westphalia

(USC, ηnet = 45.6 %, 600 MWel, gross )

Underlying Assumptions






Wet chemical absorption process

▸MEA based process with optimistic performance parameters:

- 3.3 GJ/t CO2 @ 90% capture rate

�� Steam supply pressure 3.3 bar

to atmosphere



flue gasfrom FGD

steam

reboiler

to compression






Wet chemical absorption process

▸MEA based process with optimistic performance parameters:

- 3.3 GJ/t CO2 @ 90% capture rate




CO2 compression process

▸ 8-staged compressor, each stage intercooled

▸ Pipeline conditions 110 bar, 40 °C

1 2 3/4 6/75 8



Study Approach

CCS power plant

▸ Design at full load with 90 % CO2 capture rate

▸ Flow sheet layout unchanged to maintain comparability

▸MEA process parameters not varied

For each design case

▸Optimization of steam bleed pressures of pre-heat train

▸Optimal reboiler condensate return point

Conducted analyses

1. Evaluate impact of integration

2. Optimization by waste heat recovery measures

6



General Integration Issues

Interface requirements delivered by the power plant

1. Heat for regeneration in sufficient quantity and quality

2. Power to drive the CO2 compressor, pumps and fans

3. Cooling water to discharge waste heat

Only reasonable option extract LP-steam form IP/LP crossover pipe

▸ Best suited to extract large mass flows (~ 50% needed)

▸ To meet the required quality (T,p) over entire load range

• steam attemperation

7

reboiler

To condensate

pre-heat train

From IP/LP

crossover pipe

spray

attemperator



Interface requirements delivered by the power plant

1. Heat for regeneration in sufficient quantity and quality

2. Power to drive the CO2 compressor, pumps and fans

3. Cooling water to discharge waste heat

Only reasonable option extract LP-steam form IP/LP crossover pipe

▸ Best suited to extract large mass flows (~ 50% needed)

General Integration Issues

3.3 bar to CCU

IP/ LPcrossover pipe

▸ To meet the required quality (T,p) over entire load range

• steam attemperation

• pressure maintenance concept

8



Impact of Pressure of the IP/LP Crossover Pipe

50

60

70

80

90

100

35.4

35.5

35.6

35.7

35.8

35.9

Ne

t e

ffic

ien

cy a

t d

esi

gn

po

int

in %

Min

ima

l lo

ad

wit

ho

ut

thro

tte

lin

g in

IP/L

P c

ross

ov

er

pip

e i

n %

9

0

10

20

30

40

34.9

35.0

35.1

35.2

35.3

3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5

IP/LP crossover pipe design pressure in bar

base case- 10.6 % N

et

eff

icie

ncy

at

de

sig

n p

oin

t in

%

Min

ima

l lo

ad

wit

ho

ut

thro

tte

lin

g in

IP/L

P c

ross

ov

er

pip

e i

n %



Optimisation by Waste Heat Recovery (I)

Potential sources of waste heat for recovery

▸ Reasonable temperature level needed

10



Potential sources of waste heat for recovery

▸ Reasonable temperature level needed

• Partial condenser at desober head

• Intercoolers and aftercooler of CO2 compressor

Possible heat sinks for direct integration

▸ Condensate pre-heating

Optimisation by Waste Heat Recovery (I)

▸ Combustion air pre-heating (replacement of steam air heater)

Advanced heat integration �� improve the temperature level of the waste heat

▸ Sikpping distinct intercoolers of the CO2 compressor (heat pumping)

▸ Increase air pre-heat to finally achieve feedwater pre-heating (heat

shifting)

11



No Heat recovery measure

1 DHC ► Condensate

2 DHC► Combustion Air

3 7 IC ► Condensate


Optimisation by Waste Heat Recovery (II)

Efficiency improvement in % points

Simple heat recovery



6 DHC ► Advanced APH

7 Combination of 1+5

8 Combination of 1+5+6

12

Advanced heat recovery

Combinations



Conclusions

Steam demand predominant reason for efficiency penalty

Design point efficiency strongly dependent on design philosophy

▸ Excess of 2.2 bar decreases efficiency by 0.9 % points at design point

▸ Slope of part load efficiency improved with increased crossover pipe

pressure

�� Has to be carefully considered regarding planned operation

Optimization by heat recovery measures

▸ Up to 0.9 % point advancement in efficiency (promising)

▸ Increases degree of integration �� potentially lowers availability / operability

▸Most cost effective option has to be evaluated

13



Thank you for your attention!

Imo Pfaff - [email protected]

Institute of Energy Systems

14



Advanced Combustion Air Pre-heat Configuration

APHSec. I

APHSec. II

Feedwater-heater

Tem

per

atur e

Configuration without bypass

Available temperature level of

flue gas bypass

(mass flow determines the heat

available)

15

Sec. II

Air Heater

(steam/waste

heat)

APH Sec I APH Sec II

TransferredHeat

Combustion Air

without bypass

Waste Heat Input

Constant flue gas temperature

integration studies of post-combustion co 2 capture by wet ... filehamburg university of technology...

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