Chemical looping reforming: process fundamentals and oxygen carriers

Abstract

Chemical looping reforming (CLR) provides a viable process intensification approach for clean and efficient syngas production from carbonaceous fuel with inherent gas–gas separation. The rational design of metal oxide-based oxygen carriers and the scale-up of associated CLR reactor systems play important roles in CLR process development. This review first introduces the concept and advantages of CLR as well as its historical development. The process fundamentals, including basic schemes, reaction stoichiometry, thermodynamics, kinetics and reactor system design, are reviewed. The integral approach for CLR process development is illustrated, showing that the design and compatibility of oxygen carriers and reactor systems are critical for CLR performance. The reaction principle during the reduction of oxygen carriers is discussed, followed by strategies for improving the redox reactivity and stability. We further review and discuss the latest exciting advances on this subject with the purpose of illustrating factors that govern fundamental mechanisms in the redox reaction chemistry of oxygen carriers and their design principles for sustained chemical looping reactor applications. It is expected that these new advances will inspire more effective oxygen carriers and efficient reactor systems for the development and deployment of various CLR processes.