An experimental study on the effect of igneous intrusions on chemical structure and combustion characteristics of coal in Daxing Mine, China

To investigate the effect of igneous intrusions on the structure and combustion characteristics of coal, the normal bituminous coal and thermally altered coal were collected from Daxing Mine in China. The chemical structural features of coal were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Structural parameters determined from XRD analyses, including the interlayer spacing of the crystallite (d(002)), stacking height (L-c), aromaticity (f(a(XRD))), and coal rank (R-XRD), revealed that the altered coal showed more crystalline carbon and higher coal rank than the normal bituminous coal. FTIR analyses indicated that igneous intrusions increased the apparent aromaticity of the altered coal and elevated its maturation level, which was consistent with the XRD results. TG-DSC experiments were conducted to study the combustion characteristics of coal. The result showed that the combustion process of the altered coal was delayed to high-temperature region. Compared with the normal coal, the altered coal exhibited lower combustion reactivity and worse combustion performance, as evidenced by lower comprehensive combustion index, higher ignition temperature and burnout temperature, as well as larger apparent activation energy. Moreover, igneous intrusions decreased the heat release and calorific value of the altered coal during combustion, which was ascribed to the changes in chemical composition and structure of the altered coal. This study concluded that igneous intrusions increased the difficulty in igniting the altered coals and reduced its heat release during combustion.