On the use of membrane reactors in biomass utilization

2013-07-31IGCC power plants show promise for environmentally-benign power generation. In these plants coal and/or biomass are first gasified into syngas, which is then processed in a water gas-shift (WGS) reactor to further enhance its hydrogen content for power generation. However, impurities in the syngas, primarily H₂S, NH₃, various organic vapors and tar-like species are detrimental to catalyst life and must be removed before the gas enters the WGS reactor. This, today, means cooling the syngas for clean-up and then reheating it to the WGS reaction temperature. For use in various industrial applications, and potentially for CO₂ capture/sequestration, hydrogen purification is required. This, today, is accomplished by conventional absorption/desorption processes, which results in significant process complexity and energy penalty for the overall plant. Ideally, one would like to establish a ""one-box"" process in which the syngas is fed directly into the WGS reactor, which then effectively converts the CO into hydrogen in the presence of all the aforementioned impurities, and delivers a contaminant-free hydrogen product. In this study, the development of such a process is described. It includes a catalytic membrane reactor (MR) making use of a hydrogen-selective, carbon molecular sieve membrane, and a sulfur-tolerant Co/Mo/Al₂O₃ catalyst. The membrane reactor’s behavior has been investigated for different experimental conditions and compared with the modeling results. The model is used to further discuss the scale-up of the proposed process