Research Progress and Perspectives of Solid Fuels Chemical Looping Reaction with Fe-Based Oxygen Carriers

Chemical looping (CL) is regarded as a promising technology in industrial applications, because of its inherent characteristic of CO2 capture. The technique of CL is applied in solid fuels fields, including chemical looping combustion (CLC), chemical looping gasification (CLG), chemical looping reforming (CLR), chemical looping water splitting (CLWS), and oxygen carrier aided combustion (OCAC). Oxygen carrier is a core media in chemical looping reaction, which plays the role of transporting oxygen and has the function of decreasing the energy penalty of air separation. Among all oxygen carriers, iron-based (Fe-based) materials are of most possibilities to be applied in industrial field, because of its economical and eco-friendly characteristics. Some reviews have reported the Fe-based oxygen carrier in CL application. However, the related preparation methods, overall application of CL and theoretical reaction calculation of Fe-based oxygen carriers have not been covered comprehensively. In this Review, the general view of Fe-based oxygen carrier including iron ores and artificial synthesis are reviewed. In addition, the different synthesis methods of Fe-based oxygen carrier are meticulously and profoundly summarized, involving mechanical mixing, impregnation, spraying drying, freeze granulation, sol–gel, solution combustion, and coprecipitation method. Then, the characteristics of Fe-based oxygen carrier from the perspectives of thermodynamics, redox kinetics analysis, antisintering and wear property of iron oxides are discussed in detail. Furthermore, the chemical looping reaction mechanism of Fe-based oxygen carriers is reviewed from the perspectives of reaction and oxygen carrier migration mechanism. Moreover, this review summarizes the application of Fe-based oxygen carrier in CLC, CLG, CLR, CLWS, and OCAC. And the recent progress of reaction mechanism of oxygen carrier by density functional theory (DFT) calculations and machine learning are further presented. Finally, the challenges and prospects for Fe-based oxygen carrier with the corresponding effective strategies are proposed. It is expected that this Review may provide insights into the Fe-based oxygen carrier and the practical application of chemical looping.