The influence of inorganic components in the Shengli lignite on the bond breaking and functional group evolution patterns during pyrolysis

Abstract Inorganic components, as an important part of coal, have a significant impact on the pyrolysis behaviour of coal. In this paper, the acid washing method is used to remove inorganic components from coal, and the ion exchange method is utilized to load various metals detected by inductively coupled plasma atomic emission spectrometer (ICP) back into the coal in their original content. The effects of inorganic component removal on the physicochemical structure of SL lignite were systematically investigated, with particular focus on bond cleavage mechanisms, evolutionary patterns of functional groups, and pyrolysis characteristics of the coal samples. The results show that the removal of inorganic components can disrupt the cross‐linked structure in SL lignite, promoting the release of aliphatic, aromatic, and oxygen‐containing functional groups at low temperatures. Nevertheless, it is detrimental to the cleavage of C ar O and C al C ar at high temperatures, hinders the further depolymerization of the coal structure, and leads to a decrease in the content of light components in the pyrolysis tar. The addition of K, Fe, and Ca can effectively promote the breaking of various CC bonds and CO bonds during the pyrolysis process, increase the release rate of various functional groups during the pyrolysis process, and increase the content of light components in the pyrolysis tar. Among them, K, due to its strong cracking ability, promotes the extensive breaking of CC bonds. Fe, on the other hand, promotes the generation of H 2 and stabilizes the oxygen‐containing components, resulting in the highest tar yield.