Use of Fe2O3-Containing Industrial Wastes As the Oxygen Carrier for Chemical-Looping Combustion of Coal: Effects of Pressure and Cycles

Abstract

Chemical-looping combustion (CLC), employing metal oxide(s) as the oxygen carrier for solid fuels (such as coal and biomass) combustion, is of growing interest thanks to its low cost of CO2 capture and the high system conversion efficiency. In this work, Fe2O3-containing wastes from the steel industry were applied as the oxygen carrier for chemical looping combustion with a Chinese bituminous coal in a bench-scale fixed-bed reactor. The performance of Fe2O3-containing industrial wastes was estimated with comparison to that of two other commercial iron ores (MAC iron ore from Australia and CVRD iron ore from Brazil). Effects of the operating pressure of the system (from 0.1 to 0.5 MPa) and cycle number (0–20) on the performance of the oxygen carriers were extensively studied, in terms of overall gas composition, carbon conversion, and its conversion rate. The Fe2O3-containing industrial wastes were remarkably sensitive with the operating pressure, as more pyrolysis gases and char gasification products were converted under higher pressure leading to higher concentration of CO2 and lower concentrations of CO and CH4. The elevated pressure also increased the carbon conversion and the overall reaction rate. The reactivity and porosity of the Fe2O3-containing industrial wastes under atmospheric pressure were notably enhanced by the reduction cycles, giving the concentration of 99% CO2 and the carbon conversion 81.41% after 20 cycles. Comparatively, the Fe2O3-containing industrial wastes exhibited better performance as oxygen carrier than the other two iron ores (MAC iron ore and CVRD iron ore), while the two iron ores behaved similarly to the Fe2O3-containing industrial waste with regard to the variation of operating pressure and cycles. It could be concluded that the Fe2O3-containing industrial wastes would be the outstanding oxygen carrier for chemical-looping combustion of coal over the other two iron ores.