Investigation of Fe2O3 with MgAl2O4 for chemical-looping combustion

Chemical-looping combustion (CLC) is a combustion technology with inherent separation of the greenhouse gas CO2. The technique involves the use of a metal oxide as an oxygen-carrier, which transfers oxygen from the combustion air to the fuel. The metal oxide Fe2O3 on MgAl2O4 support was examined, and particles of diameter 125-180 mum were prepared by freeze-granulation. The reactivity was evaluated in a fluidized-bed reactor, where the atmosphere was periodically changed. Reduction was performed in 50% CH4 and 50% H2O, while the oxidation was performed in 5% O-2. The sintering temperature and the ratio of metal oxide/inert were varied in order to find the optimal particle properties. The particles were characterized with respect to crushing strength, surface structure, and chemical composition, and 60% Fe2O3 on 40% MgAl2O4 sintered at 1100 degreesC was found to be the most suitable oxygen carrier. The particle had a high reactivity and showed no tendency to agglomerate or break apart during the cyclic tests. The results indicate that the amount of material needed in the fuel reactor would be in the order of 150 kg/MW.