Analysis of hydrogen-rich syngas generation in chemical looping gasification of lignite: Application of carbide slag as the oxygen carrier, hydrogen carrier, and in-situ carbon capture agent

Chemical looping gasification (CLG) has become a popular method for producing hydrogen-rich syngas due to its environment-friendliness. Recently, a method of using industrial solid waste carbide slag as an oxygen carrier, hydrogen carrier, and in-situ carbon capture agent in the CLG process has been proposed. However, the actual experiment was affected by heat and mass transfer, and the detailed reaction pathway of the carbide slag was not fully understood. In the present study, the process of the CLG process for producing hydrogen-rich syngas with lignite and carbide slag was analyzed using tube furnace experiments, FactSage calculations, and joint characteristic experiment of carbide slag. The result showed that to achieve a gas phase product with a hydrogen concentration exceeding 90 vol% (with dry N2 excluded), a molar ratio of lignite to carbide slag of greater than 1:5 and a reaction temperature of 923 K should be maintained. In terms of the reaction pathway of carbide slag in the CLG process, it was revealed that calcium hydroxide, the primary component of carbide slag, directly participated in the reaction at temperatures of less than 773 K. Overall, this work provides a novel idea for the preparation of hydrogen-rich syngas during CLG process. •The result confirmed the characteristics of oxygen-carrying, hydrogen-carrying and in-situ carbon capture of carbide slag.•Hydrogen content above 90 vol% (with dry N2 excluded) in lignite's CLG can be achieved by a one-step process.•Calcium hydroxide of carbide slag can be directly and indirectly involved in hydrogen release and in-situ carbon capture.