Reactivity of Natural Ilmenite and Fe₂O₃/Al₂O₃ Oxygen Carriers over Multiple Cycles

Abstract

Chemical-looping coal combustion (CLC) is a high efficiency technology for the conversion of coal and the potential capture of CO₂ capture. The CLC is based on the transfer of oxygen from air to the fuel by a solid oxygen carrier. This study, investigated ilmenite reduction contained two steps of Fe₂O₃ to FeO, and FeO to Fe by CO and the conditions that avoid the deep reduction with multiple cycles by using TG. Reaction models for the reduction of ilmenite with multiple cycles were examined. A synthetic Fe₂O₃/Al₂O₃ oxygen carrier was also tested for comparison. Ilmenite re-oxidation by air after a second reduction step caused particle agglomeration, since Fe oxidation produces large amount of heat. To protect against the deep reduction of FeO to Fe in ilmenite, short reduction times and the incomplete reduction of Fe₂O₃ to FeO can be used. The reduction of iron oxide in the reduction of Fe₂O₃ to FeO step can also be limited when 0.3< CO/(CO+CO₂) <0.7. Reaction models for the reduction of ilmenite with multiple cycles were examined.