Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.tu-darmstadt.de

Technische Universität Darmstadt

Feasibility Study on Carbonate Looping Process for Post Combustion CO2-Capture

from Coal fired Power Plants

B. Epple und J. Ströhle

4th International Workshop on In-Situ CO2 RemovalLondon, 7-9 July 2008

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.de

CO2 Capture from Coal-Fired Power PlantsOverview of Processes

•• FlueFlue gas gas scrubbingscrubbing (z.B. MEA (z.B. MEA scrubbingscrubbing))– Very high energy demand (Δη ~ 14%), high costs– Environmental problems (toxic absorbents)– „Post-combustion“ technology -> retrofit possible– Far developed

•• OxyfuelOxyfuel combustioncombustion– High energy demand (air separation) – Need for further development (e.g. steam generator/burner)

•• GasificationGasification technology (IGCC)technology (IGCC)– „Pre-combustion“ technology– High energy demand, high costs, complex process– Need for further development (e.g. H2 gas turbine)

•• Membrane Membrane processesprocesses (z.B. AZEP, Oxycoal)– Oxyfuel technology– Low energy demand– High need for development (e.g. materials)

Alternatives: “Oxyfuel“ Chemical LoopingChemical Looping„Post-combustion“ Carbonate LoopingCarbonate Looping

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.de

„Post Combustion“

Carbonate Looping

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.deCarbonate-Looping Principle

CaO

CaCO3

CO2 to compressionDecarbonated

flue gas

Flue gas from power plant AshDeactiveted lime

Make-up CaCO3

O2

Fuel

CARBONATOR650 °C

CALCINER900 °C

• „Post-combustion“ process• Energy demand for O2 supply to calciner (~1/3 of oxyfuel)

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.deCarbonate Looping: Reaktivity of CaO

• Application to continuous operation of two reactors

• Active fraction of CaO (Formula of Abanades (2005)) :

0

0

(1 )(1 )

m wcarb w

R m

f f FX fF F f

× − ×= +

+ × −

• Experiments in batch reactor withcyclic carbonisation/calcination(Abanades, 2002)

• Decrease of reactivity of CaO withnumber of cycles

• Reactivity converges againstconstant values of approx. 15 %

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.deProcess Scheme for Retrofit

Cold end of reference power plant 1052 MWel

CaO/CaCO

Q3

Carbonator

650 °CCalciner

CO reduced2

flue gas

CO compression2

CaCO

3

O2

CaCO3

CaO

FanFGD

Coal

Q2 Q4

Q1

900 °C

Preheater3

3

ASU

Source: Romeo et al.Mod. by EST TU Darmstadt

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.deReference Power Plant 1052 MWel

Hard coalFuel45,6% (net)Efficiency1052MWel (net)2308MWthPower

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.deASPEN Model: Carbonate Looping

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.deASPEN-Modell: Assumptions

• Flue gas from reference plant after FGD

• Aim: 80 % CO2 capture in carbonator

• Pressure increase by fan before carbonator: 200 mbar

• 99 % SO2 capture in carbonator und calciner

• Coal burn-out in calciner: 99,5 %

• Oxygen excess in calciner: λ = 1,1

• O2 purity after ASU: 95 %

• Energy demand for ASU: 185 kWh/t O2 (Source: IVD Stuttgart)

• Cooling of flue gases in steam generator down to 330 °C; below coolingfor internal pre-heating down to ~100 °C

• Water/steam process according to reference plant

• 100 % CO2 capture in calciner

• CO2 compression treated separately (considered later)

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.deASPEN Results: Mass Flows

0

1000

2000

3000

4000

5000

6000

7000

8000

0 25 50 75 100 125 150 175Makeup [t/h]

Zirk

ulie

rend

er M

asse

nstr

om [t

/h]

0

50

100

150

200

250

Koh

lest

rom

[t/h

]

zirkulierender Massenstrom [t/h]

Kohlestrom [t/h]

High Makeup rate (at constant CO2 capture rate in carbonator of 80 %):→ High Active fraction of CaO → low circulating mass flow required→ Low energy demand in calciner for heating CaCO3 from 650 to 900 °C

Circ

ulat

ing

mas

sflo

w[t/

h]

Coa

lmas

sflo

w[t/

h]

Circulating mass flow [t/h]

Coal mass flow [t/h]

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.deASPEN Results: Efficiency

High Makeup rate (at constant CO2 capture rate in carbonator of 80 %):→ Lower energy demand for heating solids, but higher energy demand for first

calcination of fresh limestone→ Less CO2 from coal in calciner (i.e. captured by 100 %)

-4,0

-3,5

-3,0

-2,5

-2,0

0 25 50 75 100 125 150 175Makeup [t/h]

Wirk

ungs

grad

einb

uße

[%-P

unkt

e]

80

85

90

95

100

CO

2-Ef

fizie

nz [%

]

WirkungsgradeinbußeCO2-Effizienz

( ), ,

el, KW el, CL

Kohle KW Kohle CL u

P P m m H

η +=

+

,2

, , ,

22 2 2

CL outCO

KW RG CL fuel CL makeup

COX

CO CO CO=

+ +

* without CO2compression

*

Plan

t effi

cien

cydr

op [%

poi

nts]

CO

2ef

ficie

ncy

[%]

Plant efficiency drop [% points]CO2 efficiency [%]

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.deHeat Balance of Steam Generator

Boundary conditions:

Steam parameters as in referenceplant:

SH: 600 °C, 285 bar

RH: 620 °C, 59 bar

ΔT > 23 K

Feed wate before ECO: 307 °C

Cooling of flue gas down to 330 °C

Results (APROS):

Live steam: 476,6 kg/s

El. gross power: 636,2 MW (as in ASPEN results)Calciner Carbonator

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.deALSTOM CFB Boiler > 200 MWel

Customer Power plant Country Gross

[MWel]

Year of commis- sioning

Fuel

China Guodian Corp. Xialongtan China 300 2007 Bituminous coal China Guodian Corp. Xialongtan China 300 2007 Bituminous coal Qinhuangdao Power Qinhuangdao #6 China 300 2007 Brown coal Qinhuangdao Power Qinhuangdao #5 China 300 2007 Brown coal Yunnan Datang Honghe Kaiyuan 1 China 300 2006 Anthracite Yunnan Datang Honghe Kaiyuan 2 China 300 2006 Bituminous coal Sichuan Baima Power Baima China 300 2005 Bituminous coal East Kentucky Power Gilbert/Spurlock USA 268 2004 Bituminous coal ENEL Sulcis Italy 340 2004 Bituminous coal Reliant Seward #2 USA 290 2004 Waste coal Reliant Seward #1 USA 290 2004 Waste coal AES Puerto Rico Guayama 1 Puerto Rico 250 2002 Bituminous coal AES Puerto Rico Guayama 2 Puerto Rico 250 2002 Bituminous coal Choctaw Generation Red Hills 1 USA 250 2001 Brown coal Choctaw Generation Red Hills 2 USA 250 2001 Brown coal AES Warrior Run Warrior Run USA 208 2000 Bituminous coal Korea Electric Power Tonghae 1 South Korea 220 1998 Anthracite Korea Electric Power Tonghae 2 South Korea 220 1998 Anthracite EdF/Soprolif Provence IV France 250 1995 Lignite

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.de

Largest CFB Boiler

293 m2

Quelle: Foster Wheeler

Lagisza/PL 460 MWe CFB , Commissioning 2008

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.deConclusions

Chemical Looping:

•potentially lowest efficiency drop (< 1 % without CO2 compression)

•restricted suitability for retrofit of existing power plants (CFB)

•promising option for new power plants with CO2 capture

Carbonate Looping:

•efficiency drop (less than 3 % * ) mainly due to supply of O2, but significantly lower than oxyfuel combustion or MEA scrubbing

*plus CO2 compression = in total 6 % efficiency drop

•well suited for retrofit of existing power plants (repowering)

For further investigation regarding in 1 MWth scale at TU Darmstadt

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.de

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Combustion chamber for exhaust gas generation

bottom ash

Ash

container

fabric filter

combustion chamber

blower

flue gases

Main items for modifications- ignition device- chamber (combustion volume)- bottom ash separation- fly-ashes (blower, filter)

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.de

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CFB600Thermal duty up to 1MW

height 10 m

Pressure 200mbar

External diameter 1,3 m

Internal diameter 0,6 m

Baghouse working T 140-180 °C

Carbonator

CFB600 as Carbonator

• primary air and flue gas source

• connection with the calciner

• dust separation and extraction

Venturi scrubber

Carbonator

Baghouse filterHeat exchanger

By-pass

Start-up

burner

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.de

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Calciner (or Gasifier)ACFBG

Thermal duty 1500 kW

Flue gas T 700 - 1000 °C

height 10,5 m

External diameter 1000 mm

Internal diameter 400 mm

Baghouse working T 300-400 °C

Reactor pressure0-100MBAR

(G)

ACFBG as Calciner- pipe connections- gasification mode

Flue gases

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2-Ab

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Kalk

stei

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.deAnsichten 3D-Modell

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2-Ab

sche

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.deAnsichten 3D-Modell

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.deAcknowledgements

• The financial support by the German Ministry of Economics and Technology (BMWi) und the Utility Companies (EON; EnBW; Evonik; RWE)

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.de

„OXYFUEL“

Chemical Looping

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.de

Chemical-Looping Principle

(1)Air reactor

2 MexOy-1 + O2 2 MexOy

(2) Fuel reactor

MexOy + Fuel MexOy-1 + CO2 + H2O

AIR

MexOy

CO2 H2ON2

Fuel

MexOy-1

(1)Air

reactor

(2)Fuel

reactor

• „Oxyfuel process“• No energy demand for separation of N2/O2

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Prof. Dr.-Ing. B. EppleEnergy Systems & Technologywww.est.TU-Darmstadt.de

END