Effect of fault structure on the structure and oxidative spontaneous combustion characteristics of coal

In order to investigate the influence law of fault tectonic on coal structure and spontaneous combustion characteristics, the fault tectonic coal and primary coal in No. 11301 working face of Hongqingliang coal mine were taken as study samples. The FT-IR experiment of infrared spectrum, thermogravimetric analysis experiment, low temperature nitrogen adsorption experiment and closed coal oxidation experiment were used to analyze the active group content, combustion characteristic temperature, pore structure characteristics, oxygen consumption rate, and oxidation heat release intensity of coal samples from a micro perspective and a macro perspective separately. The results of the FT-IR experiment of infrared spectrum showed that the active groups of the fault tectonic coal were more than those of the native coal, and the oxidation activity of the fault tectonic coal was high. The results of the thermogravimetric analysis experiment showed that the cracking temperature, critical temperature, ignition temperature, peak temperature and combustion temperature of the fault tectonic coal were lower than those of the native coal, and the fault tectonic coal showed a stronger tendency of spontaneous combustion. The results of the low temperature nitrogen adsorption experiment showed that the fault tectonism changed the pore structure of the coal, and compared with the native coal, the specific surface area of the fault tectonic coal increased by 2.5 times, and the average increase of pore size was 2.36 times, the increase of micropore volume and mesopore volume were 2.71 times and 1.69 times respectively. The influence of fault tectonism on the pore structure characteristics of coal was facilitated the oxidation reaction between oxygen and active groups in the pores. The results of the closed coal oxidation experiment showed that under the condition of temperature of 25-70 ℃,oxygen consumption rate, CO release rate, CO₂ release rate and oxidative exothermic intensity of coal increased exponentially with the increasing temperature. Under the condition of oxygen concentration of 20% and temperature of 25-70 ℃,the oxidation exothermic intensity of the fault tectonic coal in No.11301 working face of Hongqingliang coal mine was 1.37-2.00 times of the native coal. The tendency of spontaneous combustion was stronger for the fault tectonic coal compared with the native coal of the seam. The whole studies revealed from micro and macro perspectives that the reason why the fault tectonic coal was more prone to spontaneous combustion in the actual mining environment was that the coal's own structure and spontaneous combustion environment factors were changed to make it more favorable for spontaneous combustion.