Interaction between bimetallic composite oxygen carriers and coal and its contribution to coal direct chemical looping gasification

Coal direct chemical looping gasification (CDCLG) to produce synthesis gas was investigated with Fe-based bimetallic composite oxygen carriers (Fe-M oxides, M - Ba, Ca, Cu, Ni and Co). Thermogravimetric-mass spectrum analysis and fixed-bed tests indicated that reaction between coal and Fe-based composite oxygen carriers via direct contact could not be negligible in the CDCLG process. The contribution of the reaction between the two solid particles to the carbon conversion was estimated. Furthermore, the yields of synthesis gas production were also conducted to evaluate performance for the prepared samples. Of the five investigated Fe-based bimetallic composite oxygen carriers (OCs), Fe Ni oxides/Al2O3 presented high reactivity with coal and high selectivity for synthesis gas during coal-OC steam gasification, which made it attractive for the CDCLG process. By comparing with the main phases of the Fe-based OCs after cycling and the raw samples before test, it could be observed that there were no significant changes in material phases. Combined with the SEM images of the Fe-based OCs samples, we can conclude that the prepared OCs showed a good heat-resistant property, which was beneficial for keeping a stable performance in the CDCLG experiment. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.