Investigation of immersion-induced coal pore evolution effect on oxygen affinity and thermodynamic characteristic temperature

The immersion-induced pore restructuring and oxidation activity reinforced are critical drivers of coal spontaneous combustion. This study combines the multiple instrumental tests and molecular simulations to propose the immersion long-flame coal chain oxidation promotion mechanism. It reveals the correlated characteristics among the pore expansion, oxygen affinity enhancement, and intensified spontaneous combustion tendency. Those contribute to understanding the intrinsic facilitation patterns of the immersion coal spontaneous combustion. The water immersion transforms the smooth surface into a rough surface with pronounced cracks. It raises the specific surface area, total pore volume, and average pore diameter by 38.0 %, 32.1 %, and 8.0 %. The immersion coal exhibits the decreased micropore volume alongside the increased mesopore and macropore volume that provides more favorable pathways for O₂ adsorption. The O₂ concentration ratio in the coal-occupied region rises from 64.0 % to 72.4 % and its diffusion coefficient drops by 18.5 % that boosts the O₂ accumulation and oxidative reactivity in the immersion coal. The ignition temperature drops by 13.00 °C and the residual mass reduction declines by 5.03 % which demonstrates the increased self-ignition tendency. This study underpins a vital practical strategy for managing the immersion coal spontaneous combustion.