Coal gasification using chemical looping with varied metal oxides as oxygen carriers

Coal gasification using chemical looping (CGCL) has been suggested as an innovative coal gasification technology for producing high quality synthesis gas with lattice oxygen from oxygen carrier instead of molecular oxygen. In this work, highly active nanoparticles (NPs) based on the transition metals Mn, Co Fe and Ni were prepared and used as oxygen carriers (OCs) to promote carbon conversion. Furthermore, the reaction mechanism between OCs and coal was investigated to guide the design of OCs and the fuel reactor. It was found that the presences of OCs evidently facilitated to coal gasification and enhanced total carbon conversion. Of the four investigated OCs, Mn@meso-SiO2 presented high reactivity with coal and high selectivity for synthesis gas during coal-OC steam gasification, which made it attractive for the CGCL process. TG-MS analysis indicated that direct solid-solid contact reaction between coal and OCs could not be negligible in the CGCL process. Furthermore, no significant changes in material phases were found by comparing with the main phases of the OCs after cycling and the raw samples before test. Combined with the SEM images of the OCs samples, it can be conclude that the used OCs showed a good heat-resistant property. (C) 2019 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.