Evolution mechanism of thermodynamic characteristic parameters of CH₄ adsorption influenced by structural coal quality ratio

With the increasing depth of coal seam mining in China, the consequences of coal and gas outburst accidents are becoming more and more serious, which poses a great threat to mine safety production. Tectonic coal is one of the main coal sample types prone to outburst, and the outburst law and phenomenon change obviously with the proportion of tectonic coal quality. In order to explore the thermodynamic mechanism of gas adsorption in structured coal with different mass ratios, PCT-C80 adsorption calorimeter was used to carry out gas isothermal adsorption and calorimetric test based on mixed coal samples, and the calculation models of adsorption enthalpy, Gibbs free energy and gas adsorption entropy were established from the thermodynamic point of view. Based on the test and calculation results, the relationships between adsorption capacity and adsorption heat, gas adsorption constant and the proportion of structural coal with different mass ratios are discussed respectively, and the variation laws of gas adsorption enthalpy, surface free energy and adsorption entropy of structural coal with different mass ratios are analyzed. The results show thatthe gas adsorption heat of structural coals with different mass ratios increases with the increase of adsorption capacity; The adsorption heat and adsorption constant A both increase first and then decrease with the increase of structural coal mass ratio, and the adsorption constant B shows the opposite change law. With the increase of the ratio of structural coal, the gas adsorption heat, adsorption enthalpy and adsorption entropy all increase at first and then decrease, and all reaching the maximum when the proportion of structural coal is 50%, while Gibbs free energy shows the opposite change law; According to the test results and fitting formula, the mathematical relationship between the thermodynamic parameters of gas adsorption and gas emission in mixed coal is summarized. Through the above research, the variation law of thermodynamic characteristic parameters of gas adsorption under the influence of structural coal ratio is obtained, and the thermodynamic action mechanism of mixed coal samples is revealed, which provides a certain theoretical basis for clarifying the mechanism of coal induction and gas outburst caused by mining disturbed structural coal.