Sorption enhanced–chemical looping steam methane reforming: Optimizing the thermal coupling of regeneration in a fixed bed reactor

Abstract

Sorption enhanced–chemical looping steam methane reforming is a promising process for hydrogen production. In this process, the reformer contains, in addition to a solid CO2 sorbent, an oxygen transfer material (OTM). Ιn–situ CO2 capture by the sorbent shifts the overall reaction to the products' side, leading to high purity H2 production in a single step. The saturated sorbent is then regenerated in a second reactor at higher temperatures. The OTM is simultaneously reoxidized, generating significant amount of heat which is in–situ used for sorbent's regeneration. In this work, the optimization of heat coupling during the regeneration step of the intensified process was studied experimentally using a NiO/ZrO2 OTM–reforming catalyst, mechanically mixed with a CaZrO3–promoted CaO sorbent. The effect of two key operating parameters during regeneration was considered: the residence time of the feed stream and the type of oxidant (air, pure O2). Higher space velocities increased the percentage of CaCO3 decomposition without external heat supply. The use of pure O2 can provide in situ 47% of the heat requirements of the sorbent's regeneration, a value which is very close to the theoretical degree of autothermicity under the investigated conditions (57%), while producing a pure, ready for sequestration CO2 stream.