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

摘要

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). In-situ CO2 capture by the sorbent shifts the overall reaction to the products' side, leading to high purity H-2 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 O-2). Higher space velocities increased the percentage of CaCO3 decomposition without external heat supply. The use of pure O-2 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.