Recent Advances in the Evolution of Pollutants and Their Interactions with Oxygen Carriers During Coal Chemical Looping

Chemical looping is a clean, energy-efficient, and economically viable route for coal utilization. However, the pyrolysis and gasification of raw coal in chemical looping generate gaseous pollutants (SOX, NOX, and Hg) and ash that affect both reactor performance and the environment. This review synthesizes the current understanding of the formation, transformation, migration, and release of these pollutants in chemical looping, alongside the behavior of coal ash. It further assesses how these species interact with oxygen carriers, influencing reactivity, redox stability, sintering, agglomeration, attrition, and deactivation. Based on these insights, the review proposes research priorities for pollutant management and oxygen-carrier design, and for elucidating the coupled dynamics of the coal/oxygen-carrier/ash three-component particle system in fuel reactors.