Chemical Looping Combustion of Methane or Coal by Fe2O3/CaSO4 Mixed Oxygen Carrier

The effects of Fe2O3 addition to CaSO4 as a composite oxygen carrier, which is a useful material in terms of its combustion and thermal stability, were evaluated in the chemical looping combustion (CLC) of CH4 and coal. The addition of Fe2O3 to CaSO4 was found to enhance the CO2 evolution rate and total amount of CO2 produced, with the best results, in terms of CO2 production and CH4 conversion, obtained with a 20% by weight (wt%) addition of Fe2O3 to CaSO4 (20%Fe2O3/CaSO4). The preliminary study for thermal stability and regeneratability of 20%Fe2O3/CaSO4 in the CLC of CH4 and coal was established over four and three reduction-oxidation cycles, respectively, while the morphology and solid composition of the fresh and spent oxygen carrier were analyzed by scanning electron microscopy and X-ray diffractometry (XRD), respectively. The formation of Ca2Fe2O5 in the reduced 20%Fe2O3/CaSO4, as detected by XRD measurements, appeared to prevent thermal agglomeration. For the CLC of coal, the reaction was optimal at 950C. The results confirm that the 20%Fe2O3/CaSO4 composite oxygen carrier could potentially be used in the CLC process of both gaseous and solid fuels.