Research Progress on Sulphur Migration Characteristics in Coal Chemical Looping Combustion Processes

Coal chemical looping combustion (CLC) enables high-concentration CO2 capture with low NOx emissions. However, coal-derived sulphur species in the fuel reactor (FR) present severe challenges, including oxygen carrier (OC) poisoning and CO2 stream contamination. This study identifies coal-derived sulphur within the FR as the primary emission source and systematically characterises its release patterns during pyrolysis and gasification, comparing in-situ gasification CLC (IG-CLC) and chemical looping with oxygen uncoupling (CLOU). Coal sulphur distribution pathways and their governing factors are systematically investigated, followed by a comprehensive characterization of sulphur release behaviour during pyrolysis and gasification. We propose a novel perspective advocating a paradigm shift from passive sulphur tolerance to active in-situ sulphur capture through the rational design of Multifunctional Oxygen Carriers (MOCs). This review provides a comprehensive theoretical framework and practical guidelines for designing sulphur-resistant systems, thereby accelerating the industrial deployment of clean coal chemical looping technologies.