Research on Low Temperature Oxidation Characteristics of Coal Under the Condition of Igneous Intrusion

In order to study the low-temperature oxidation characteristics of coal under the condition of igneous intrusion, two pairs of samples collected from S5709 and S2905 coalface in Daxing Mine, with one normal and one metamorphic coal affected by the igneous intrusion in each pair were investigated. The oxygen consumption, gas emission （CO, C₂H₄） and crossing point temperature T_cpt of the samples were tested by the temperature programmed experimental apparatus, and the low temperature nitrogen adsorption, mercury intrusion were used to analyze the pore structure under the influence of igneous intrusion. The results show that the surface area and pore volume of macroscopic pores and part of the mesopore increase for coal intruded by igneous rocks, and its average pore size is larger. And the O₂ consumption of metamorphic coal is higher, while T_cpt is lower compared to the normal coal. The tendency index of coal spontaneous combustion falls from 605.69 of normal coal to 310.62 in S5709, and from 761.34 to 382.91 in S2905, respectively. Moreover, the gas emission of metamorphic coal is higher than that of the normal coal. The effect of high temperature and pressure induced by igneous rocks causes the development of coal pore with pore size more than 20 nm, thus, the risk of coal spontaneous combustion increases.