Investigation of Mn3O4 with stabilized ZrO2 for chemical-looping combustion

Chemical-looping combustion is a new technology that could contribute to reconcile the contradictory requirements of increased energy demand and less greenhouse gases in the atmosphere. This technique involves combustion of fossil fuels by means of an oxygen carrier which is circulated between air and fuel reactors. The oxygen carriers investigated in this paper are manganese oxides on pure zirconia and zirconia stabilized by either CaO, MgO or CeO2. The effect of the sintering temperature on strength, chemical composition and reactivity of the particles was investigated. Reactivity was investigated on particles of 125-180 mu m in a laboratory fluidized bed-reactor of quartz. Reduction was performed in 50% CH4/50% H2O while the oxidation was carried out in 5% O-2 in nitrogen. For all four types of particles, the reactivity was inversely proportional to the sintering temperature and the strength of the particles. The oxygen carrier that seemed least affected by the continuous redox reactions and at the same time showed high reactivity was Mn3O4 with Mg-ZrO2.