Influence mechanism of pore structure evolution on oxygen consumption dynamics during low-temperature oxidation of igneous metamorphic coal

In igneous-intruded coal seams, coal undergoes significant metamorphism, which critically alters its pore structure and oxygen consumption dynamics, thereby elevating its spontaneous combustion tendency. This study investigates the specific surface area, pore volume, structure complexity/connectivity, heterogeneity/local features of pore size distribution, and oxygen consumption dynamics of igneous metamorphic coal through N 2 /CO 2 isothermal adsorption tests and low-temperature oxidation experiments, and elucidates the influence mechanisms of pore structure evolution on oxygen consumption dynamics during low-temperature oxidation. With increasing metamorphic degree, igneous metamorphic coal exhibits a more pronounced reduction in specific surface area during oxidation, while the increase in structure complexity due to coal-oxygen reactions is suppressed. Thermally metamorphic coal demonstrates accelerated oxygen consumption, with oxidation amplifying the difference in reaction rates compared to raw coal. Key mechanisms include oxidation-induced reduction in mesopore complexity and micropore volume, decreased dominance of small-pore-volume apertures, and increased heterogeneity, collectively leading to a lower half-oxygen-consuming temperature and steeper oxygen consumption curves. Simultaneously, increased pore volume/complexity and reduced uniformity/connectivity act synergistically to enhance oxygen consumption capacity, highlighting the coupling between pore structure evolution and oxidation behavior in igneous metamorphic coal. This study provides theoretical insights into the pore-oxygen coupling mechanisms governing coal spontaneous combustion in igneous intrusion areas.