Hydrogen from Coal in a Single Step

Abstract

The production of high-purity hydrogen via steam gasification of coal has been investigated. The separation of CO from H2 in the gasification products is achieved by CO oxidation to CO2 followed by uptake of the CO2 by a suitable removal agent. This uptake of CO2 increases the extent of the water gas shift reaction and enhances the yield and purity of H2. In addition to the water gas shift reaction, the oxidation is enhanced by the use of a solid oxygen transfer agent (Fe2O3) in the hydrogen enrichment pass. Subsequently, the reduced oxygen transfer agent is reoxidized (and thus regenerated) in the presence of air and the heat liberated via the exothermic reaction is utilized to regenerate carbon dioxide removal agent. In this study, the effect of process variables on coal gasification and hydrogen enrichment has been evaluated. Fixed bed gasification studies using coal and coal−Fe2O3 and coal−CaO mixtures were conducted to evaluate the kinetics of gasification and separation effectiveness of the process. Finally, a bench scale fluidized bed reactor was employed to study the efficacy of the simultaneous gasification−hydrogen enrichment process. The reactions were conducted in the temperature range of 670−900 °C at atmospheric pressures. The results from the fundamental studies, the fixed bed reactor studies, and the fluidized bed reactor studies are presented.