Energy efficient sorption enhanced-chemical looping methane reforming process for high-purity H2 production: Experimental proof-of-concept

Abstract

High purity H2 was produced by a novel low-energy sorption enhanced steam methane reforming process by introducing a second loop in order to provide part of the required heat for the endothermic sorbent calcination in the regeneration stage. The feasibility of the intensified reforming process was demonstrated experimentally over a mixture of a bifunctional NiO-based oxygen transfer material/reforming catalyst supported on ZrO2, and a ZrO2-promoted CaO-based CO2 sorbent. The experiments were performed in a bench-scale fixed bed reactor unit. The influence of operating parameters, such as reformer’s temperature, steam/methane and NiO/CaO molar ratios and space velocity of the feed stream, was investigated in order to determine the optimum operating conditions and assess the full potential of the combined process over the two solids. The presence of the CO2 sorbent in the reactor facilitated H2 production of high purity. Equilibrium concentrations were obtained over all studied conditions, even at very high space velocities. The process was further demonstrated with a continuous cyclic test of 20 reforming/regeneration cycles at a temperature of 650°C. The CO2 sorbent and the oxygen transfer material exhibited excellent stability without deterioration in performance for 20 consecutive cycles, corresponding to more than 60h of testing. H2 concentration over 95% was achieved throughout the sorbent’s prebreakthrough region during the reduction/reforming/carbonation stage. During the reoxidation/calcination step, the highly exothermic Ni oxidation provided adequate heat to raise the temperature of the solids and decompose up to 45% of the saturated sorbent without external heating.