Experimental study on the adsorption and permeability characteristics of coal under the coupling of stress and temperature

In order to simulate the process of gas production in deep coal seams,the isothermal adsorption experiments at different temperatures and the seepage test in the gas loading process were carried out respectively by using the iso-thermal adsorption device and triaxial servo-controlled seepage equipment for the thermo-fluid-solid coupling of coal containing methane. A modified Langmuir model and adsorption-swelling model considering the effects of excess ad-sorption were established to investigate the evolution law of adsorption and seepage under the coupling of stress and temperature. The results show as follows:① the gas adsorption volume increases with the increase of gas pressure at different temperatures,while the adsorption volume decreases with increasing temperature. Under high pressure,it is necessary to consider the error caused by excess adsorption capacity. The modified Langmuir model is more accurate than the original model;② the modified adsorption deformation and swelling model considering the correction of temperature and excess adsorption was established. The strain caused by the adsorption of coal gradually decreases with the increase of pore pressure and strain variation decreases with the increase of temperature. With the increase of pore pressure,the permeability of coal and the variable quantity of permeability caused by adsorption swelling and slippage effect show a tendency of decreasing,which gradually increase with increasing temperature;and ③ adsorption swelling is the main factor that leads to the decrease of permeability of coal. The contribution rate of adsorption swelling and slippage effect to permeability decreases with the increase of pore pressure,and its contribution rate increases with in-creasing temperature.