Mitglied der Helmholtz-Gemeinschaft
Routen der CO2-Abscheidung
in Kraftwerken
E. Riensche, J. Nazarko, S. Schiebahn, M. Weber, L. Zhao, D. Stolten
Forschungszentrum Jülich GmbH, D-52425 Jülich
Institut für Energie- und Klimaforschung – IEK-3: Brennstoffzellen
Jahreshaupttagung der DPG - Arbeitskreis Energie (AKE)
Dresden, 13.-16. März 2011
Introduction
Three phases of power production from coal occur:
• 20th century: Continually increasing efficiency up to ……………..….… ~45 %
• Ending with: Flue gas cleaning (DeNOx, Dedust, DeSOx) ……….....… 1-2 %-points loss
• 21th century: Necessity for CCS (Carbon Capture and Storage) … ~8-14 %-points loss
Challenge of CCS:
• Collecting CO2 as pure as possible
• High efficiency of power production
Current efficiency penalties of 12-14 %-points
• CO2 separation degrees ~90% and
• CO2 purities between ~90 and 99 mol%
R&D:
• Gas separation
• Integrated CCS systems
CO2-Abscheidung, Vortrag D. Stolten, Dresden 16.03.2011
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CCS Process Steps
CO2 separation
1
2
Potential
power plant
modifications
• Further flue gas
cleaning
• CO shift
• Recirculation
Gas/gas
separation
• CO2/N2
• O2/N2, CO2/H2O
• CO2/H2
CO2 transport and storage
3
4
5
Potential
subsequent
CO2 cleaning
CO2 compression
1  100 bar
liquefaction
Further
compression
Exceptions:
e.g. post comb.
chilled ammonia
15-20  100 bar
Power plant
6
Potential further
compression
Up to
1000 bar
Pipeline
e.g. 500 km
pressure drop
200  100 bar
Injection
at significant
depth
e.g. aquifers
in Germany
1 – 10 km
• Up to 6 processes contribute to CCS energy demand
 Accumulated losses to be minimized
CO2-Abscheidung, Vortrag D. Stolten, Dresden 16.03.2011
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Data Base of Energy Content for Fossil Fuels
CH4
10
LHV / MJ/kgCO2
203%
Typical
Coal
C
10
117%
5
100%
0
MJ/kgfuel
32.8
25.0
50.0
MJ/kgCO2
kWhth/tCO2
8.94
2480
10.5
2910
18.2
5050
Emission:
Nm³CO2/kWhth
0.205
0.175
0.101
0
Source: Reference power plant NRW, VGB 2004
• Typical coal: LHV = 2910 kWhth/tCO2 produced
 Efficiency loss = 1 %-point for CCS energy demand of 29 kWhe/tCO2 (100% separated)
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LHV / kWhth/Nm³CO2
20
Separation Routes, Tasks and Methods
Routes
Postcombustion
Oxyfuel
Separation tasks
Methods
CO2 vs. N2 - from flue gas
Absorption with liquids
Carbonate Looping
Adsorption with solids
Membranes
O2 vs. N2- from air
Cryogenic air separation (standard)
Chemical looping combustion
Membranes
(after CO shift to CO2)
Absorption with liquids
Carbonate looping
Membranes
H2 vs. CO2
Adsorption with solids
Membranes
CO2 vs. H2- from coal gas
Precombustion
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Prevalent Gas Separation Methods
Separation methods
Separation principles
Materials
Sep. gas
Amines
Chemical
Amino salts
Ammonia
Absorption
with liquids
“Rectisol”
Physical
CO2
“Selexol”
“Purisol”
Cryogenic
air separation
Condensation
& Rectification
O2
Reaction with solids
(Chemical Looping)
Me <–> MeO
Ni, Cu, Fe
AO <–> ACO3
CaO, MgO, FeO
CO2
Molecular
transport
Polymer
Microporous
CO2
or H2
MIEC for O2 sep.
O2
Membranes
Ionic / atomic
transport
MIEC: Mixed Ionic-Electronic Conductor
MPEC: Mixed Protonic-Electronic Conductor
CO2-Abscheidung, Vortrag D. Stolten, Dresden 16.03.2011
MPEC for H2 sep.
Metallic
H2
Folie 6
Absorption with Liquids
Purified Gas
CO2
CO2
Capture
Solvent
Solvent
+ CO2
Gas with CO2
Solvent
Regeneration
Solvent
make-up
Spent
solvent
Solvent loading with CO2
Physical
Henry´s
law
IGCC
Flue gas
Chemical
pCO2~5-10 bar
Energy
Partial pressure of CO2
 Chemical absorption for low CO2 partial pressures, e.g. flue gases
 Physical absorption for high CO2 partial pressures, e.g. coal gas (IGCC, pressurized)
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Reaction with Solids
CO2 + H2O
Oxidation
unit
(Air reactor)
Air
NiO
Ni
Reduction
unit
(Fuel reactor)
Fuel
Oxyfuel via
Chemical Looping Combustion
CO2-free
flue gas
Absorption
(Carbonizing)
T = 650 °C
Coal gas or
flue gas
with CO2
CO2
for compression
CaCO3
CaO
Regeneration
(Calcining)
T = 900 °C
Ash
CaO
CaCO3
Make-up
CaCO3
Fuel
Oxygen
Carbonate Looping
• CLC: applicable for coal gas & natural gas
• CLC: direct oxygen transport via a metal carrier
 CLC promises energy saving oxygen delivery for oxyfuel
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Polymer Membranes: CO2 Separation from Natural Gas
Example for a natural gas field
p ~100 bar
p ~100 bar
Natural gas
pCO2 ~10 bar
p ~1 bar
pCO2 ~1 bar
CO2
• Transport: solution diffusion mechanism
• Driving force: partial pressure difference
• Compressors: not required in natural gas fields
• Integration in coal power plants:
- Limitation in operating temperature
- Compression energy to be considered
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Inorganic Membranes
Inorganic Membranes
Metallic
Ceramic
Microporous
Dense
Dense
MPEC: Mixed
Protonic-Electronic
Conductors
H+/e-
Diffusion of Hatoms
Amorphous:
e.g. Sol-gel
membranes
Crystalline:
e.g. Zeolites
MIEC: Mixed
Ionic-Electronic
Conductors
O2-/e-
Up to 600 °C
150 - 400 °C
150 - 400 °C
800 - 1000 °C
500 - 800 °C
O2/N2 – Oxy
H2/CO2 – Pre(H2)
H2/CO2 – Pre(H2)
jH 2  S H 2  DH 2 / L

CO2/N2 – Post
CO2/N2 – Post
H2/CO2 – Pre(H2) H2/CO2 – Pre(H2)
pH 2  pH 2

j A  PA   pA  pA 
CO2-Abscheidung, Vortrag D. Stolten, Dresden 16.03.2011


jO 2  RT 16 F 2   amb L   ln  pO 2 pO 2 
Folie 10
Résumé: CCS Power Plant Classes
Basic concept
Route
Gas
separation
task
Post
CO2
Oxy
O2
Gas separation method
Cond.
Absorption / Reaction
Membrane separation
Cryog. Absorption w. liquids Reaction with solids
air sepaPolymer
Chemical
Physical
Adsorption
Reaction
ration
SPP
IGCC*
SPP
IGCC*
SPP
IGCC
CO2
SPP
IGCC
IGCC +
Shift
SPP
IGCC*
Porous
Metallic
SPP
IGCC*
SPP
IGCC
IGCC +
Shift
Mixed
cond.
SPP
IGCC
IGCC +
Shift
Pre
H2
IGCC +
Shift
IGCC +
Shift**
IGCC +
Shift**
IGCC +
Shift**
IGCC +
Shift**
* Flue gas recycle for higher CO2 concentration
** Flue gas recycle for membrane sweep with a large O2-poor N2 gas stream
• Today: two power plant technologies: Steam Power Plant (SPP) and IGCC
• Identified: 32 CCS power plant classes
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Increase of CO2 Concentrations through Flue Gas Recycling
IGCC
Post-combustion
(basic)
Coal gas
Post-combustion with flue gas
recycling (advanced)
CO2~6%
λ~2.5
SG
GT
CO2 Coal gas
ST
Air
CO2~13-15%
λ~1
Steam power plant
Air
λ~1
CO2 Coal gas
GT
ST
Air
N2~70%
O2~10%
Coal
Oxyfuel
(with flue gas recycling)
Air
CO2
GT
ST
H2O
N2~5%
O2~0%
CO2
Coal
n/a
N2,
(H2O)
λ~1
ASU O
2
CO2~12-14%
ST
CO2~90%
Air
CO2~90%
λ~1
ASU O
2
CO2
ST
H2O
l: air ratio, ASU: air separation unit, GT: gas turbine, SG: steam generator, ST: steam turbine
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Post-combustion: Amine Scrubbing
CO2-free
flue gas
CO2+H2O
40°C
60°C
90°C
Absorber
Desorber
Heat
exchanger
Flue gas
100°C
55°C
Heat supply
• Absorption heat is released at low temperature
• Desorption requires heat at higher temperature
• Heat supplied by steam condensation at the desorber
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Compression energy / kWh/tCO2
120
4
For compression to 120 bar
CO2 captured at 1 bar
takes from efficiency 4 %-points
(100% CO2 separation, 5 mol% N2)
100
3
Source: after Göttlicher 2004
80
60
2
40
1
20
0
Plant efficiency loss / %-points
Final Compression of Captured CO2 to 120 bar
0
0
20
40
60
80
100
CO 2 pressure after capture / bar
120
 CO2 released at 10 bar takes 2 %-points (e.g. Post-combustion/Chilled ammonia)
 CO2 released at 30 bar takes 1 %-point (e.g. Pre-combustion/H2 membrane)
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CO2 Phase Diagram for Pure CO2 and CO2-N2 Mixtures
Pipeline
Source:
Goos, Riedel, Zhao, Blum,
GHGT-10, Amsterdam 2010
• Pure CO2: Two-phase behaviour only at the saturation line
• Impure CO2: Two-phase regions occur - exceeding 100 bar
 Work hypothesis for pipeline transport: 5 mol% N2 tolerable
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Conclusions
CCS concepts encompass a broad variety of solutions
• Post-combustion, Oxyfuel, Pre-combustion
• Gas separation: Absorption, Adsorption, Reaction with solids, Rectification, Membranes.
All concepts show potentials for further improvement
• Materials´ and componenent development
• Integration of components and “CCS waste heat” (from capture and compression).
The minimum efficiency penalty for CCS is estimated to be
• 4 %-points for CO2 capture from flue gas (90% separation) and
• Even potentially lower, if separation of pure gases is avoided, e.g. by
- Membrane sweep (permeation - dilution) and
- Chemical looping (e.g. reaction of O2 with a metal carrier – directly in air).
Successful development of CCS concepts will require in-depth dialogue between
process engineers and material scientists.
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Thank You for Your Attention!
June 20-22-2011, Frankfurt am Main
Efficient Carbon Capture for Coal Power Plants
www.icepe2011.de
CO2-Abscheidung, Vortrag D. Stolten, Dresden 16.03.2011
Folie 17
Thank You for Your Attention!
2nd International Conference on Process Engineering
Efficient Carbon Capture for Coal Power Plants
June 20-22, 2011
Frankfurt am Main/ Germany
Registration:
www.icepe2011.de
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