Study on Multifractal of Coal Pore Structure Based on Low Pressure Argon Adsorption and Its Effect on Gas Adsorption/Desorption

Although the coal pore structure is attracting the attention of researchers, studies on the multifractal and gas adsorption/desorption capacity are relatively few. In this study, multifractal characteristics were analyzed, and their effects on gas adsorption/desorption were discussed. The results showed that metamorphism and tectonism affected gas adsorption/desorption by changing the coal pore structure. The limit gas adsorption volume and initial desorption rate of tectonic coals increased by 3.9%–23.9% and 1.96–2.7 times, respectively. The information dimension (D1), correlation dimension (D2), and classical Hurst index gradually decreased with metamorphism and tectonism, while the Hausdorff dimension and Δα gradually increased, indicating that pore size distribution (PSD) was more decentralized or inhomogeneous. The evaluation results of the correlation between multifractal parameters and complexity confirmed its accuracy in assessing pore complexity. Multifractal parameters have a significant impact on gas adsorption/desorption capacity overall, mainly by reflecting the concentration degree, local density, and homogeneity of pores.