Task 6.5 - Gas Separation and Hot-Gas Cleanup
Catalytic gasification of coal to produce H{sub 2}- and CH{sub 4}-rich gases for consumption in molten carbonate fuel cells is currently under development; however, to optimize the fuel cell performance and extend its operating life, it is desired to separate as much of the inerts (i.e., CO{sub 2} and N{sub 2}) and impurities (i.e., H{sub 2}S and NH{sub 3}) as possible from the fuel gas before they enter the fuel cell. In addition, the economics of the integrated gasification combined cycle (IGCC) can be improved by separating as much of the hydrogen as possible from the fuel, since hydrogen is a high-value product. One process currently under development by the Energy & Environmental Research Center (EERC) for accomplishing this gas separation and hot-gas cleanup involves gas separation membranes. These membranes are operated at temperatures as high as 800 C and pressures up to 300 psig. Some of these membranes can have very small pores (30-50 {angstrom}), which inefficiently separate the undesired gases by operating in the Knudsen diffusion region of mass transport. Other membranes with smaller pore sizes (<5 {angstrom}) operate in the molecular sieving region of mass transport phenomena, Dissolution of atomic hydrogen into thin metallic membranes made of platinum and palladium alloys is also being developed. Technological and economic issues that must be resolved before gas separation membranes are commercially viable include improved gas separation efficiency, membrane optimization, sealing of membranes in pressure vessels, high burst strength of the ceramic material, pore thermal stability, and material chemical stability. Hydrogen separation is dependent on the temperature, pressure, pressure ratio across the membrane, and ratio of permeate flow to total flow. For gas separation under Knudsen diffusion, increasing feed pressure and pressure ratio across the membrane should increase gas permeability; decreasing the temperature and the permeate-to-total flow ratio should also increase gas permeability. In the molecular sieving regime of mass transport, the inlet pressure and pressure ratio should have no effect on gas permeability, while increasing temperature should increase permeability.
- Research Organization:
- National Energy Technology Lab., Pittsburgh, PA, and Morgantown, WV (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- FC21-93MC30097
- OSTI ID:
- 16123
- Report Number(s):
- DOE/MC/30097-5528, M97002194; ON: DE97053314; TRN: US200511%%174
- Resource Relation:
- Other Information: Supercedes report DE00016123; Supercedes report DE97053314; PBD: 1 Jun 1997; PBD: 1 Jun 1997
- Country of Publication:
- United States
- Language:
- English
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Task 6.5/6.7.1 - Materials for Gas Separation and Hydrogen Separation Membranes
Gas separation and hot-gas cleanup
Related Subjects
01 COAL, LIGNITE, AND PEAT
08 HYDROGEN
36 MATERIALS SCIENCE
CERAMICS
COMBINED CYCLES
DIFFUSION
DISSOLUTION
FUEL CELLS
FUEL GAS
GASIFICATION
HYDROGEN
MOLTEN CARBONATE FUEL CELLS
OPTIMIZATION
PALLADIUM ALLOYS
PERMEABILITY
PRESSURE VESSELS
COAL
GASES
IMPURITIES
MEMBRANES
PLATINUM
STABILITY