Model and decarbonization performance of moving bed reduction reactor for natural gas chemical looping combustion

Chemical looping combustion is a promising method for reducing CO2 emissions while achieving high-level fuel utilization. The use of moving bed reactors, characterized by their operational flexibility and minimal particle loss, offers a viable alternative for chemical looping processes. In this study, we develop a new porous media model that integrates gas-solid two-phase flow, heat and mass transfer processes, and thermochemical reactions to characterize and optimize a moving bed reduction reactor. We numerically analyze and compare the performance characteristics of the moving bed reduction reactor using NiO/Al2O3 as the oxygen carrier and CH4 as the fuel. The results demonstrate the superiority of the countercurrent operation, which achieves higher fuel utilization efficiency and a more uniform temperature profile under the conditions of constant wall temperature. The benefits of uniform inlet gas injection highlight the need for a gas distributor to avoid maldistribution and enhance the reactor performance. The effects of circulation rate, inlet temperature, active material concentration, and reduction degree of oxygen carrier, and steam-carbon ratio on the reactor performance are evaluated in terms of methane conversion and fuel utilization efficiency. Additionally, a quantitative relationship between the reactor volume required for 95% fuel utilization and the oxygen carrier inlet temperature is established. These research findings provide a fundamental reference for the development of the moving bed reduction reactor for chemical looping combustion processes.