Praxair is conducting research to develop hydrogen transport membrane (HTM) technology to separate carbon dioxide (CO2) and hydrogen (H2) in coal-derived syngas for IGCC applications. The project team has fabricated palladium based membranes and measured hydrogen fluxes as a function of pressure, temperature, and membrane preparation conditions.
Membranes are a commercially-available technology in the chemical industry for CO2 removal and H2 purification. There is, however, no commercial application of membrane processes that aims at CO2 capture for IGCC syngas. Due to the modular nature of the membrane process, the design does not exhibit economy of scale—the cost of the system will increase linearly as the plant system scale increases making the use of commercially available membranes, for an IGCC power plant, cost prohibitive. For a membrane process to be a viable CO2 capture technology for IGCC applications, a better overall performance is required, including higher permeability, higher selectivity, and lower membrane cost.
The Praxair hydrogen transport membrane (HTM) project targets improvements in H2-CO2 separation membrane characteristics, including higher permeability, higher selectivity, and lower membrane cost. Specifically, the project work will scale-up current HTM technology to develop the design of a membrane hydrogen-separation unit capable of producing at least 4 tons/day of H2 from syngas derived from coal or coal-biomass by testing a 2 lbs/day membrane module using coal-derived syngas. Increased efficiency and directly resulting cost reductions come by operating the transport membranes at higher temperature (in combination with warm gas cleanup technology being developed). HTM technology will be versatile, applicable to both integrated gasification combined cycle (IGCC) with over 90% carbon capture, and having the ability to make chemical grade hydrogen for liquid fuel, chemicals synthesis, and polygeneration applications.
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