Effects of chemistry and mineral on structural evolution and chemical reactivity of coal gangue during calcination: towards efficient utilization

The utilization of coal gangue is usually subjected to calcination to achieve high chemical reactivity and exclude carbon. The correlation between the composition and properties of coal gangue during calcination is essential for its applica- tions. In this paper, the effect of chemistry and minerals of coal gangues on the thermal behavior, structural evolution and chemical states of silicon and aluminum during the calcination process were sys- tematically investigated. The results show that high alumina (AlH) containing coal gangue consists pri- marily of kaolinite, while in medium and low alumina containing (AlM and AlL) groups, the major mineral phases are quartz, kaolinite, illite with minor impuri- ties. The chemical reactivity of coal gangue mainly contributes to the transformation of kaolinite to metakaolinite, while illite plays a minor role and quartz is inert. The combustion of carbon may promote the dehydroxylation of clay minerals and further affects the structure evolution of coal gangue. Theoptimalcalcinationtemperaturetoexcludecarbon and achieve high chemical reactivity is therefore suggested as 700 C. Based on the findings the utilization of coal gangue is discussed in light of composition and structure.