Calcium Looping Process (CLP) for Enhanced Noncatalytic Hydrogen Production with Integrated Carbon Dioxide Capture

The calcium looping process (CLP) is one of the clean coal technologies being developed for the production of hydrogen (H2) and electricity from coal-derived syngas. It integrates the water−gas shift reaction with in situ carbon dioxide (CO2), sulfur, and halide removal in a single-stage reactor. In the CLP, a regenerable calcium-based sorbent is used to react with and remove CO2, sulfur, and halide impurities from the synthesis gas during the production of H2. The removal of CO2 creates a favorable equilibrium and drives the water−gas shift reaction forward per Le Chatelier’s principle enabling the production of high-purity H2. In this investigation, the feasibility and optimum process conditions for the production of H2 in the absence of a water−gas shift catalyst have been described. Calcium oxide (CaO) sorbent has been found to enhance H2 yield to a large extent even in the absence of a water−gas shift catalyst. Specifically, at high pressures, high carbon monoxide (CO) conversion and H2 purity (>99%) have been obtained in the absence of a water−gas shift catalyst at near-stoichiometric steam to carbon (S:C) ratios.