Study on the influence of microscopic components and pore structure of coal-rock system on methane adsorption

In order to explore the influence of the micro-components and pore structure of the coal-rock system on methane adsorption, six groups of coal samples of Shaqu No.1 mine were selected to study the effects of microscopic components and pore structure characteristics on methane adsorption by industrial analysis, X-ray diffraction, scanning electron microscopy and energy spectrum analysis, low-temperature nitrogen adsorption, computed tomography and coal-rock methane adsorption experiments.The research results show that the content of inorganic components in coal samples is 15.82% to 20.93%, and that in rock samples is 90.80% to 94.68%, which are mainly composed of quartz and clay minerals.The BET specific surface area of the rock sample is 3.32 m²/g to 8.70 m²/g and the adsorption pore volume is 0.009 5 cm³/g to 0.019 1 cm³/g, which are all larger than those of the coal sample.The pore surface roughness and pore structure complexity of the rock sample are slightly larger than those of the coal sample, which are related to the high content of clay minerals.The methane adsorption isotherm curves of coal-rock samples are all in line with the Langmuir model, and the adsorption law can be described by the limit adsorption capacity V_L and Langmuir pressure p_L; under the same adsorption temperature, the adsorption property of coal samples is much larger than that of rock samples, and there is a certain adsorption of rock samples.The analysis shows that the content of organic components, clay mineral content, surface fractal dimension, specific surface area and adsorption pore volume have significant effects on the V_L and p_L of the methane adsorption process.Based on multiple linear regression, the influence of 5 factors on methane adsorption was analyzed.The sample with high content of organic components and large specific surface area of CH₄ molecule has a larger limit adsorption capacity V_L, while high content of clay minerals is not conducive to the adsorption of methane; the smaller the adsorption pore volume, the higher the content of clay minerals, the larger the specific surface area and the greater the Langmuir pressure p_L is.