Coal spontaneous combustion (CSC) is a disaster associated with coal mining that leads to loss of coal resources and environmental and human health issues. To investigate kinetic characteristics for oxidation of coal, three coal samples were collected from different coal mining areas in the Southern Junggar coalfield. Subsequently, the collected coal samples were ground into different particle sizes and tested using microscopic and macroscopic methods, including thermal gravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffraction, and temperature-programmed oxidation. The results obtained are as follows: the sharpest absorption peak (002) indicates that graphitization is high. Furthermore, the results show that the SKS coal sample is prone to spontaneous combustion; the greater the aromatic hydrocarbon content is, the more difficult it is for CSC to occur, while the opposite is true for oxygen-containing functional groups. The SKS data confirmed this conclusion; the rate for generation of CO and CO₂ controlled the possibility of SKS oxidation at 110 °C and provided an indication of the temperature. During the dehydration stage, the WD sample had the lowest activation energy, indicating that it was most susceptible to spontaneous combustion. During the combustion stage, the lowest activation energy was found for the SKS sample with particle sizes < 0.075 mm, indicating that particle size was one of the factors affecting spontaneous combustion. The activation energy for dehydration was significantly lower than that for combustion, which showed that the coal oxygen reaction was more likely to occur in the dehydration stage. Based on DSC curves, the SKS sample had the largest exothermicity, indicating that it would ignite more readily.

Adsorption thermodynamic characteristics are an important part of the methane adsorption mechanism, and are useful for understanding the energy transmission mechanism of coalbed methane (CBM) migration in coal reservoirs. To study the effect of coal pore characteristics on methane adsorption heat, five different types of rank coals were used for low-pressure nitrogen, low-pressure carbon dioxide, and methane adsorption experiments. Pore structure and adsorption parameters, including maximum adsorption capacity and adsorption heat, were obtained for five coal samples, and their relationships were investigated. The results show that the low-pressure nitrogen adsorption method can measure pores within 1.7–300 nm, while the low-pressure carbon dioxide adsorption method can measure micropores within 0.38–1.14 nm. For the five coal samples, comprehensive pore structure parameters were obtained by combining the results of the low-pressure nitrogen and carbon dioxide adsorption experiments. The comprehensive results show that micropores contribute the most to the specific surface area of anthracite, lean coal, fat coal, and lignite, while mesopores contribute the most to the specific surface area of coking coal. Mesopores contribute the most to the pore volume of the five coal samples. The maximum adsorption capacity has a significant positive correlation with the specific surface area and pore volume of micropores less than 2 nm, indicating that methane is mainly adsorbed on the surface of micropores, and can also fill the micropores. The adsorption heat has a significant positive correlation with the specific surface area and pore volume of micropores within 0.38–0.76 nm, indicating that micropores in this range play a major role in determining the methane adsorption heat.

In the present paper, with using diverse methods (including the SEM, the XRD, the TPO, the FTIR, and the TGA) , the authors analysed samples of the major coal seam in Dahuangshan Mining area with different particle sizes and with different heated temperatures (from 50 to 800 °C at regular intervals of 50 °C). The results from SEM and XRD showed that high temperature and high number of pores, fissures, and hierarchical structures in the coal samples could facilitate oxidation reactions and spontaneous combustion. A higher degree of graphitization and much greater number of aromatic microcrystalline structures facilitated spontaneous combustion. The results from TPO showed that the oxygen consumption rate of the coal samples increased exponentially with increasing temperature. The generation rates of different gases indicated that temperatures of 90 °C or 130 °C could accelerate coal oxidation. With increasing temperature, the coal oxidation rate increased, and the release of gaseous products was accelerated. The FTIR results showed that the amount of hydroxide radicals and oxygen-containing functional groups increased with the decline in particle size, indicating that a smaller particle size may facilitate the oxidation reaction and spontaneous combustion of coal. The absorbance and the functional group areas at different particle sizes were consistent with those of the heated coal samples, which decreased as the temperature rose. The results from TGA showed that the characteristic temperature T₃ declined with decreasing particle size. After the sample with 0.15–0.18 mm particle size was heated, its carbon content decreased, and its mineral content increased, inhibiting coal oxidation. This result also shows that the activation energy of the heated samples tended to increase at the stage of high-temperature combustion with increasing heating temperature.