Effect of inorganic acid elution on microcrystalline structure and spontaneous combustion tendency of Shengli lignite

XRD, Raman, XPS and FT-IR were used to examine microcrystalline structure changes of Shengli lignite eluted by inorganic acid (HCl, H2SO4 and HCl-HF). By adopting a designed surface adsorption instrument-GC, the samples were oxidized at low temperature through pulse method to investigate their oxygen adsorption under different temperatures. Via low-temperature oxidation, TG/DTG and fixed bed combustion tests, the spontaneous combustion tendency of coal samples were investigated. The results show that the removal of minerals increases the degree of order and graphitization of the coal structure. Compared with raw coal, oxygen absorption of inorganic acid elution samples decreases obviously. With the increase of adsorption temperature, oxygen absorption capacity increases significantly, but decreases with the increasing level of removed minerals, which reduces spontaneous combustion tendency of the treated coal.