Study on the mechanism of mineral effects on coal oxidation and combustion properties in the Dongsheng Coalfield

To elucidate the mechanism by which minerals influence coal spontaneous combustion, coal samples from the Fourth Mining Area of the Dongsheng Coalfield were subjected to acid-base delignification to remove minerals and characterize their types and contents. Combined with in-situ infrared spectroscopy, thermogravimetric-mass spectrometry (TG-MS), and programmed temperature-gas chromatography techniques, systematically analyzing the evolution of functional groups, oxygen consumption characteristics, gas products, and differences in combustion behavior before and after mineral removal. Experimental results indicate that the initial temperature for alkane oxidation in ash-removed coal samples increased by 30-70 °C, confirming that minerals significantly catalyze low-temperature alkane oxidation. Mineral component correlation analysis indicates that albite, gypsum, and calcite are key catalytic minerals. During the high-temperature combustion stage, the influence of minerals on combustion behavior exhibited distinct differences among coal samples: After ash removal treatment, the ignition temperature of GJL and LJH coal increased by 58 °C and 42 °C, respectively, while the maximum weight loss rate decreased by 54 % and 15 %. In contrast, the combustion characteristics of HQL and MKQ coal showed minimal changes after ash removal treatment, with MKQ coal exhibiting a slight decrease in ignition temperature. Based on XRF and mineral composition analysis, it is inferred that magnesium doping is a key factor influencing the combustion behavior of carbon skeletons, and its catalytic effect is closely related to the type of support: magnesium-doped materials supported on kaolinite/perlite exhibit significantly stronger catalytic activity than those supported on quartz. This study elucidates the role of key minerals and their occurrence forms in the coal spontaneous combustion process through the correlation between mineral composition, oxidation pathways, and combustion behavior. It lays a crucial experimental and theoretical foundation for deepening the understanding of coal spontaneous combustion mechanisms and advancing prevention and control technologies.