Field Evaluation of Carbon Molecular Sieve Membranes for the Separation and Purification of Hydrogen From Coal- and Biomass-Derived Syngas

High-temperature gas separations (GS) with inorganic membranes have attracted attention recently. In particular, the use of such membranes in membrane reactors (MR) has the potential to enhance process intensification and to increase energy savings and/or product yield. Though the potential benefits of high-temperature GS and/or MR processes are substantial, commercialization still remains elusive. A major technical barrier is the lack of robust inorganic membranes and full-scale modules which are suitable for use at the high-temperature and high-pressure conditions required. This team recently proposed and tested in the laboratory a technology, termed the “one-box” process that employs carbon molecular sieve membranes (CMSM) in an MR for the water gas shift reaction of coal- and/or biomass-derived syngas. The process combines syngas contaminant removal and CO conversion into a single unit to produce high-purity hydrogen for power generation and/or chemical use. Towards technology commercialization, full-scale multi-tubular CMSM modules have been constructed and characterized comprehensively to demonstrate the effectiveness of the potting and seal developed by us for full-scale multi-tubular inorganic membranes, in particular for ceramic membranes.  Our successful preparation of the full-scale multi-tubular inorganic membrane module overcomes some of the technical barriers which hamper the commercial implementation of inorganic membranes. Further multiple field-tests of the full-scale CMSM modules were conducted at the US National Carbon Capture Center (NCCC) coal gasification facility under conditions suitable for the “one-box” process; this paper details the results of these tests.  During continuous use (more than 300 hr) in raw coal-derived and/or biomass-derived syngas, the CMSM successfully rejected tar-like species present in the syngas without any evidence of fouling, if the operating temperature was maintained at or above 250 °C. Moreover the membrane permeation properties remained unchanged throughout this extended test.  Simulations, based upon membrane properties measured during these field tests, demonstrate that the “one-box” process, operating on a typical oxygen-blown gasifier off-gas, can deliver more than 90% hydrogen recovery at more than 90% purity (dry-basis), and thus shows good promise for commercial application. The current plan is to field-test the "one-box" process by incorporating the catalyst used in the prior lab-scale study into the full-scale CMSM module developed and field-tested successfully in this study.