Enhancement of Ca_2Fe_2O_5 oxygen carrier through Mg/Al/Zn oxide support for biomass chemical looping gasification

摘要

Oxygen carriers (OCs) determined the performance of biomass chemical looping gasification (CLG). This work focused on the potential effects of Mg/Al/Zn oxides on the CLG reactivity of brownmilerite-type Ca2Fe2O5, and the interactions between them were studied. The results showed Al oxide was unsuitable as support for Ca2Fe2O5, because it broke the crystalline structure of Ca2Fe2O5 and weakened the syngas selectivity in CLG. ZnO could enhance the syngas production property, but reduced into metal Zn, thus was also unacceptable to be added into Ca2Fe2O5. MgO addition enhanced the oxygen release capacity of Ca2Fe2O5, and the TGA and fixed bed tests showed the improvement in biomass CLG performance. MgO also provided a solvent for the reduced OC, which would raise its melting temperature by the dissolution, thus enhance the OC ability in multiple redox reactions. The 10 redox times test also showed the prepared MgO/Ca2Fe2O5 could almost kept stable reactivity. The study also provided a strategy for designing other redox materials operated in high temperature, like chemical looping or calcium looping.