Thermal characteristics and microstructural evolution mechanism of coal oxidation under methane atmospheres

Abstract

To investigate the influence of different methane concentrations on the thermal characteristics and microstructural evolution of coal oxidation, a C600 high-precision microcalorimeter combined with Fourier transform infrared spectroscopy (FTIR) was employed to analyze the heat-release behaviour and the variation of key functional groups during coal oxidation under methane–air atmospheres. The main goal of this work is to elucidate the coupled thermal–microstructural response and inhibition mechanism of anthracite oxidation under low methane atmospheres (0%–4%), rather than merely reconfirming the inhibitory effect of methane. With increasing methane concentration, the initial oxidation temperature is delayed from 120.57°C to 126.57°C, while the peak heat flow decreases from 236 to 135 mW and the total heat release drops from 1113.94 to 595.64 J/g, corresponding to a 46% reduction, indicating a pronounced inhibitory effect. FTIR analysis shows that hydroxyl, aliphatic CH and oxygen-containing functional groups are significantly enriched after oxidation in air, whereas their intensities and integrated absorbance areas progressively decrease with increasing methane concentration. The coupled thermal–spectral analysis demonstrates that variations in oxidation exothermic peaks closely correspond to the generation of hydroxyl and oxygen-containing groups, confirming that methane modifies the coal oxidation pathway and heat-release characteristics through combined oxygen-dilution, radical-chain inhibition, and adsorption effects. The primary scientific novelty of this work is the quantitative coupling of microcalorimetry and FTIR to reveal how low-concentration methane simultaneously modifies both thermal behaviour and functional-group evolution of anthracite, and to propose an integrated inhibition mechanism that goes beyond simple oxygen dilution.