A Compact Integrated Warm Syngas Overall Cleanup System

Gasification of coal or biomass to syngas followed by catalytic synthesis of ammonia, hydrocarbons or oxygenates provides a feasible strategy to meet the increasing demand for fertilizers and transportation fuels. This syngas has many impurities, including As, Be, Cd, Cl, Cr, Hg, K, N, Na, P, Pb, S, Sb, Se, V, Zn. Most of them need to be removed down to part per billion levels (ppb) due to their strong interactions with syngas reforming and synthesis catalysts. Although technical approaches exist for removal of these species, they are rather costly, employing solvents at ambient or lower temperature and backup sacrificial sorbents. The energy efficiency of the current process would be improved if all the contaminants can be removed at temperatures higher than the syngas reforming and chemical synthesis temperatures (greater than 200oC). In this presentation, we will describe our recent progress in developing a compact, integrated system for overall impurity cleanup from warm syngases generated from water-quenched coal or biomass gasifiers. This compact system consists of four major sub-systems: 1) a particulate filter to remove solid impurities, 2) a high capacity sacrificial absorption bed to remove HCl, 3) two sequential absorbent beds to remove sulfur from more than 1000 ppm levels down to less than 60 ppb levels, and 4) a high capacity metal-based sacrificial absorbent to remove As, P, Se, and trace level S and HCl. Each sub-system was individually developed, and a compact integrated system was built up. This integrated system was demonstrated to be able to remove all the catalysts poisons in a simulated warm syngas stream and thus effectively prevented the downstream syngas reforming catalysts from being deactivated. This compact system can also be used in stationary hydrocarbon fuel processors for clean feed gas generation for fuel cells applications.