Fuel, Vol.216, 181-189, 2018
Effects of igneous intrusions on the structure and spontaneous combustion propensity of coal: A case study of bituminous coal in Daxing Mine, China
An investigation of the effects of igneous intrusions on the physicochemical structure and spontaneous combustion characteristics of coal is important for safe production in coal mines. In this study, unaltered coal and thermally-altered coal affected by igneous intrusions were collected from Daxing Mine. The mineral and ash composition, surface functional groups, surface morphology and pore structure were characterized by XRD, XPS, SEM, N-2 adsorption and mercury intrusion porosimetry. The spontaneous combustion propensity of coal samples was investigated using oxidation kinetics experiment. Mineral and ash composition analysis revealed that igneous intrusions increased the relative contents of calcite and CaO in the thermally-altered coal. The results of XPS tests indicated that the content of C-C/C-H slightly increased and an obvious pi - pi* shake-up satellite peak appeared in the thermally-altered coal, but that the contents of C-O-, C=O, and COO- showed a decreasing trend. Compared with the pore structure of the unaltered coal, higher porosity, larger pore volume, and larger average pore diameter were found in the thermally-altered coal. Moreover, more pores with diameter > 20 nm were formed due to igneous intrusions, which would improve the transport capacity of O-2 in pores to react with active sites on pore surfaces in the thermally-altered coal. Moreover, igneous intrusions increased the O-2 consumption rate of the thermally-altered coal, and decreased its crossing point temperature and spontaneous combustion propensity evaluating index I. This study concluded that igneous intrusions improved the spontaneous combustion risk of Daxing bituminous coal.