A review on mercury removal in chemical looping combustion of coal

Abstract

Chemical looping combustion (CLC) of coal can effective achieve the capture and storage of CO2, reduce the emission of NOx, and realize the energy cascade utilization. During the process of CLC, mercury (Hg) will release from coal and enrich in gas. If Hg has not been effectively treated, it will not only cause the serious harm to human body and environment, but also affect the purification and storage of CO2 by mixing with CO2, as well as lead to the corrosion of equipment, which highlights the importance of Hg removal in CLC. This review summarized the influence and mechanism of gasification medium (signal CO2, signal H2O vapor, as well as mixture of CO2 and H2O vapor), gasification products (CO, H2, NH3, HCl, and H2S), oxygen carrier (single metal oxides of Fe2O3, MnO2, Co3O4, CuO, and CeO2, CaSO4, mixed OC, and natural-ores OC), reaction temperature, as well as reactor configuration in fuel reactor and air reactor on the release, oxidation, and transfer of Hg in CLC of coal. Based on these above, several suggestions about the selection of appropriate H2O(g) content to minimize the release of Hg and promote the oxidation of Hg0, the selection of OC with weak adsorption capacity and strong oxidation performance, the preparation and application of Cu, Mn, Co spinel structured oxides for promoting the catalytic oxidation of Hg0 in CLC high-temperature furnace, and the choice of an appropriate air reactor temperature to maximize the oxidation of Hg0 in the AR and reduce the escape of Hg from the AR outlet were provided for promoting the removal of Hg for CLC in the future.