Desulfurization performance of chemical looping conversion using red mud as an oxygen carrier

Abstract

Red mud (RM) is an alkaline waste residue produced in the aluminum industry, which has a huge output and is difficult to treat. However, it can be used as raw material for preparing oxygen carrier (OC) for rich in Fe, Na and Ca. In this paper, three types of RM were selected, and the desulfurization performance and mechanism of RM OCs under different reaction conditions were discussed. The results show that the desulfurization capacity of RM OCs mainly comes from Na/Ca elements, while Fe2O3 has no desulfurization capacity above 750 °C. WSRM OCs have good desulfurization performance, and the desulfurization efficiency of WS900 can reach 86.28 % at 900 °C, although high temperature is not conducive to sulfur fixation by RM OCs. WSRM OC prepared at 800–900 °C has good desulfurization activity, while the OC prepared at 1000 °C or above will have a significant decline in desulfurization performance. The components in RM OCs with desulfurization activity mainly include Na2Ti3O7 and Ca in the form of Ca2SiO4 and CaTiO3, while NaAlSiO4, Na6Al4Si4O17 and Ca2Al2SiO7 almost have no sulfur fixation capacity. The redox performance of the three RM OCs under multi-cycle conditions is little affected by H2S atmosphere; and WSRM OCs rich in Na and Ca have the best redox performance.