Microfractal characteristics of acidified coal under different temperature and adsorption pressure conditions.

This article focuses on investigating the evolution of the pore–fracture structure and fractal characteristics of acidified coal under varying methane (CH₄) adsorption pressures and temperatures, using isothermal adsorption, low-temperature nitrogen adsorption, and scanning electron microscopy (SEM) experiments. The study found that acidification increases the number and connectivity of open and inkwell pores, enhances the proportion of micropores, total pore volume, specific surface area, surface roughness, and methane adsorption capacity, thereby improving coal permeability and inhibiting oxidation-induced thermal damage. The Frenkel–Halsey–Hill (FHH) fractal model was applied to quantify changes in pore complexity, revealing that higher methane adsorption pressures correlate with increased fractal dimensions and stronger oxidation inhibition. These findings provide a theoretical basis for reducing spontaneous combustion risks in coal mining goafs and enhancing coal seam gas extraction efficiency under deep mining conditions.