In situ gasification chemical looping combustion of a coal using the binary oxygen carrier natural anhydrite ore and natural iron ore

CaSO4 is an attractive oxygen carrier for Chemical–looping combustion (CLC), because of its high oxygen capacity and low price. But the utilization of CaSO4 oxygen carrier suffers the problems of low reactivity, deactivation caused by sulfur loss and the incomplete fuel conversion due to the thermodynamic limitations. To improve the stability and reactivity of CaSO4 oxygen carrier, a small amount of natural iron ore were added in. The kinetic behavior and thermodynamics of the reduction of the binary oxygen carrier by coal under steam atmosphere were investigated. The results show that Fe2O3 improves the performance of coal gasification and the subsequent conversion of coal syngas to CO2 and H2O. Besides, the addition of Fe2O3 reduces the chance of CaSO4 reduction to CaO by coal syngas, and the oxygen transfer capacity of CaSO4 is maintained. The optimal reaction conditions in fuel reactor are shifted from 950 °C without Fe2O3 to 900 °C with 7% Fe2O3. And the decreases in CO, SO2 and H2S environmental factors can be well up to 81.48%, 76.35% and 100%, respectively. Meanwhile, the CO2 concentration in the dry gas products increases from 81.63% up to 95.35%.