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The erosion of igneous rocks affects the structural and spontaneous combustion characteristics of coal. A series of tests were conducted, including programmed heating, thermogravimetric analysis, FT-IR spectroscopy, low-temperature nitrogen adsorption, and pressed mercury experiments on samples from primary coal and coal eroded by igneous rocks from the Tashan Mine and Xiaonan Mine within the same coal seam. Based on these experiments, we analyzed various properties of coal, such as the oxidation characteristics, spontaneous combustion limit, active functional group content, chemical structure, and pore structure, from both macroscopic and microscopic perspectives. The results indicated significant trends after the erosion of igneous rocks: (1) there were increases in the oxygen consumption rate, as well as the CO and CO2 release rates; (2) the upper limit of air leakage intensity increased, the minimum thickness of floating coal decreased, and the lower limit of oxygen volume fraction decreased; (3) there was a decrease in the activation energy required for coal ignition; (4) there was a decrease in the active functional group content while improving the structural stability; and (5) there were the alterations in the pore structure of coal. These promoted the oxidation reactions between oxygen and the active groups within the coal matrix, increasing the propensity for spontaneous combustion, particularly in the igneous rocks with low oxidation activity. [ABSTRACT FROM AUTHOR]

In order to explore the influence law of igneous rock erosion on coal spontaneous combustion characteristics and structure, taking primary coal and igneous rock eroded coal in the same coal face of Shanxi Mine and Liaoning Mine as the samples, the oxidation characteristics, the limit parameters of the spontaneous combustion, the content of the active functional group and pore structure characteristics of coal were analyzed from macro and micro perspectives by temperature programmed test, FT-IR experiment, low temperature nitrogen adsorption experiment and mercury injection experiment respectively. The results of temperature programmed test showed that igneous rock erosion increased the spontaneous combustion risk of coal, igneous rock erosion could enhance the gas circulation inside the coal body, which is conducive to the oxidation reaction between oxygen and active groups inside the coal body, and the coal body of the igneous erosion had higher oxidizing activity. In addition, igneous rock erosion altered the occurrence conditions of coal seams, increased the difficulty of coal seams mining and the intensity of wind leakage in the mining airspace, prolonged the oxidation time of the residual coal in the “oxidized heating zone” in goaf, thus increasing the risk of spontaneous combustion of coal from the level of external influencing factors. The erosion of igneous rock changes the structure of coal itself and the external environmental factors of coal spontaneous combustion, which intensifies the spontaneous combustion risk of the eroded coal seam.

The erosion of igneous rocks affects the structural and spontaneous combustion characteristics of coal. A series of tests were conducted, including programmed heating, thermogravimetric analysis, FT-IR spectroscopy, low-temperature nitrogen adsorption, and pressed mercury experiments on samples from primary coal and coal eroded by igneous rocks from the Tashan Mine and Xiaonan Mine within the same coal seam. Based on these experiments, we analyzed various properties of coal, such as the oxidation characteristics, spontaneous combustion limit, active functional group content, chemical structure, and pore structure, from both macroscopic and microscopic perspectives. The results indicated significant trends after the erosion of igneous rocks: (1) there were increases in the oxygen consumption rate, as well as the CO and CO2 release rates; (2) the upper limit of air leakage intensity increased, the minimum thickness of floating coal decreased, and the lower limit of oxygen volume fraction decreased; (3) there was a decrease in the activation energy required for coal ignition; (4) there was a decrease in the active functional group content while improving the structural stability; and (5) there were the alterations in the pore structure of coal. These promoted the oxidation reactions between oxygen and the active groups within the coal matrix, increasing the propensity for spontaneous combustion, particularly in the igneous rocks with low oxidation activity.