Investigation into compound CaSO4 oxygen carrier for chemical-looping combustion

In this study chemical-looping combustion of methane with compound CaSO4 oxygen carrier prepared by impregnation method was investigated in a fixed bed reactor. The effects of reaction temperature, CH4 percent, particle size and sample mass on reduction were discussed and an appropriate condition was determined by contrastive experiments. The results show that Ni-Fe mixed additive greatly improves the reactivity of CaSO4, and the suitable reaction temperature is around 925°C. Carbon deposition is inhibited and higher gas conversion is obtained by lower CH4 percent and more sample mass. However, the sample particle size has a little effect on the reduction. The long-time reduction-oxidation test demonstrates that compound CaSO4 oxygen carrier has a higher conversion. X-ray diffraction analysis reveals that CaSO4 could be fully reduced into CaS which is also almost oxidized into CaSO4.