Review and Perspectives on Mercury Release and Migration during Chemical Looping Combustion of Solid Fuels

Chemical looping combustion (CLC) is a promising technology for global carbon reduction. In the CLC system, mercury released during combustion is not only a hazardous pollutant but also a risk to the system safety because mercury can easily lead to the amalgamation and fracture of the decarbonizing equipment. Understanding the mercury release and migration characteristics is the foundation for the safe operation of the CLC system. The purpose of this study is to lay the scientific foundation for achieving deep mercury removal during the CLC of solid fuels. The mercury flow and distribution within the CLC system were discussed. The differences in mercury release between CLC and conventional combustion or gasification were analyzed. The influence mechanisms of the key factors, such as fuel type, temperature, atmosphere, and oxygen carrier, on the release and migration fate of mercury during the CLC processes were discussed. The removal mechanisms of elemental mercury in the CLC system were revealed. Finally, research perspectives on mercury control in the CLC system were proposed. This review includes a comprehensive review of the latest research progress on mercury emission control within the CLC system. The findings of this study can provide guidance for the development of the deep mercury removal technology during CLC processes and help break the bottleneck which restricts the long-term safe operation of the CLC system.