PostCombustion Capture of carbon dioxide by Clathrate Hydrate crystallization

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Post-Combustion Capture of carbon dioxide by
Clathrate Hydrate crystallization

• Rajnish Kumar1, Praveen Linga1, Adebola Adeyemo1,
  Peter Englezos1 and John Ripmeester2

1. Clean Energy Research Center Department of
Chemical and Biological Engineering The
University of British Columbia Vancouver, BC
2. Steacie Institute for Molecular
Sciences National Research Council of Canada 100
Sussex Drive Ottawa, ON
2
Post-combustion capture of CO2 from power plants
involves separation of CO2 from flue gas
CO2, N2, O2 MIXTURE
Flue Gas
Fossil Fuels
COMBUSTION
Air
CO2 capture
CO2
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Flue gas from a coal-fired power plant

• 15-20 CO2, 5 O2 and balance N2
• Low concentration of CO2
• Absorption in MEA solutions most promising
  current method
• Development of ceramic membranes could be more
  efficient

Aaron, D and C. Tsouris, Separation Science and
Technology, 40 321348, 2005
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The clathrate hydrate process

• Hydrate formation is a very new concept for
  CO2 Capture that is still in lab testing (Aaron
  and Tsouris, 2005).

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Gas Hydrates are Crystals

• Formed by water and small molecules like (CH4,
  C2H6, C3H8, CO2, N2, O2, H2)
• No chemical reaction only physical bonding

H2O forms cages enclosing CH4
CO2 hydrate 277.1K and 4.1 MPa
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Basic Idea/Concept
Composition of Hydrate Crystals Different than
Feed
Gas Hydrate Formation from gas mixtures
FEED CO2/N2
Treated flue gas (CO2, N2, O2) is considered a
CO2/N2 mixture
Kang S.P. and H. Lee (2000),Environ. Sci.
Technol.,Vol. 34, No. 20, pp. 4397-4400.
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Laboratory scale CO2 capture

• Crystallizer volume 323 cm3
• Semi-batch operation at constant T P
• We can determine,
• Operating P-T conditions for hydrate
  crystallization
• Rate of hydrate formation
• Split fraction or CO2 recovery

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Post-combustion CO2 capture

• CO2/N2 separation via hydrate formation
• Flue gas mixture 17 mol CO2 and rest N2

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Hydrate crystal formation P T
At T 0.6 C, P 7.7 MPa
phase equilibrium
Pure N2 hydrate
Min pressure to form crystals
Hydrate from Flue Gas (17 CO2)
Pure CO2 hydrate
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CO2 prefers hydrate phase
Hydrate formation experiments were carried out at
0.6 0C and at two pressures 10 MPa and 11 MPa
(Peq 7.7 MPa)
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CO2/N2 separation recovery at 0.6 oC
Gas
83.1 mol N2 16.9 mol CO2
Hydrate
Stage 2
Stage 3
Stage 1
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Post-Combustion Capture of CO2
Single Stage Hydrate Process
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Post-Combustion Capture of CO2
First Stage
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Process Drawbacks

• Flue gas requires compression to high pressure
  (10 MPa) for hydrate formation
• 385MW (77) of the output of a 500MW power plant
  required for compression alone

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Hydrate formation pressure decreases in presence
of THF
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CO2/N2 separation recovery at 0.6 oC (in
presence of THF)
1.0 THF Solution
Gas
83.1 mol N2 16.9 mol CO2
Hydrate
Stage 2
Stage 3
Stage 1
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Post-Combustion Capture of CO2 in presence of
THF and lower pressure

• .

N2
10 CO2
First Stage
CO2 -lean
Membrane Process
17 CO2
Gas Hydrate Process (1)
83 N2
CO2
28 CO2
1 mol THF
Gas Hydrate Process (2)
CO2 -rich
62 CO2
37 CO2
T0.6oC P 2.5 MPa
Gas Hydrate Process (3)
70 CO2
94 CO2
1 mol THF
for Disposal/Storage
1 mol THF
Second Stage
Third Stage
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Concluding Remarks

• CO2 can be separated from flue gas by hydrate
  formation
• CO2 prefers the hydrate phase
• High purity CO2 can be recovered from a flue gas
  mixture in three hydrate formation stages
• Coupled with a single stage membrane process
• Additives such as THF (1mol solution) reduce the
  hydrate formation pressure
• Making it more suitable for industrial
  application

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Current Challenges

• Slow kinetics due to mass transfer restriction

Gas
Slow gas diffusion through hydrate layer
Hydrate layer
water
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Current challenges work underway

• To determine the best contact mode between water
  and gas in order to speed up hydrate formation
• Hydrate formation with water adsorbed on silica
  gel
• Hydrate formation with micro water droplets

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Acknowledgements

• Natural Resources Canada- Greenhouse Gas
  Mitigation Program
• Canada Foundation for Innovation (CFI)
• Clean Energy Research Center

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Compression Cost

• Calculated for a 500MWe PC power plant
• 2,439,000kg/hr flue gas produced
• Compression from atmospheric pressure to 10 MPa
  was considered with 4 staged compressor with
  equal compression ratio for each stage
• 385MW would be required to achieve compression

MIT Report on The Future of Coal
http//web.mit.edu/coal/