Study on pore structure characteristics and methane adsorption characteristics of Qianbei

As a complex porous medium, coal's pore structure characteristics determine its methane adsorption behavior. This study investigates anthracite from the Qianbei Coalfield through a combination of low-temperature CO? adsorption, low-temperature N? adsorption, and high-pressure mercury intrusion experiments. Fractal theory was employed to analyze the pore structure characteristics, and high-pressure methane isothermal adsorption experiments were conducted to study the impact of pore structure on methane adsorption capacity. The results indicate that the pore structure of Qianbei anthracite is predominantly composed of micropores and mesopores, with macropores constituting a relatively small proportion. Micropores contribute 75%–80% of the total specific surface area and 48%–57% of the total pore volume, representing the primary sites for methane adsorption. Mesopores play a significant transitional role in gas diffusion and transport. Fractal dimension analysis reveals that the structural complexity of mesopores and macropores (D?, D?) is higher than that of micropores (D?), indicating that pore complexity increases with scale. The Langmuir volume (VL) shows a significant positive correlation with micropore volume and specific surface area, but a certain negative correlation with fractal dimension, suggesting that overly complex pore structures may inhibit effective methane adsorption. The association analysis between multi-scale pore structure and fractal characteristics provides a theoretical basis for understanding methane occurrence mechanisms in anthracite and guiding efficient coalbed methane extraction.