Use of coal as fuel for chemical-looping combustion with Ni-based oxygen carrier

Chemical-looping combustion is an indirect combustion technology with inherent separation of the greenhouse gas CO2. The feasibility of using NiO as an oxygen carrier during chemical-looping combustion of coal has been investigated experimentally at 800−960 °C in the present work. The experiments were carried out in a fluidized bed, where the steam acted as the gasification−fluidization medium. Coal gasification and the reaction of oxygen carrier with the water gas take place simultaneously in the reactor. The oxygen carrier particles exhibit high reactivity above 900 °C, and the dry basis concentration of CO2 in the exit gas of the reactor is nearly 95%. The flue gas composition as a function of the reactor temperature and cyclic reduction number is discussed. At 800−960 °C, the dry basis concentration of CO2 in the flue gas presents a monotonously increasing trend, whereas the dry basis concentration of CO, H2, and CH4 decreases monotonously. The concentrations of CO2, CO, H2, and CH4 in the flue gas as...