Experimental study on effect of heat on methane adsorption and desorption in coal based on modified langmuir model

In order to study the influence of heat on coal adsorption and desorption of gas and its degree,a high-pressure gas adsorption apparatus and thermostatic water bath device were used to conduct methane adsorption/desorption experiments on No.11-2 coal samples in Pan 3 Coal Mine under different constant temperature environments. The results show that the amount of methane adsorption increases with the increase of methane pressure under the same temperature,but the increase gradually decreases. Under the same gas pressure,the amount of methane adsorption decreases with the increase of temperature. The Langmuir equation is introduced a correction coefficient to the gas pressure,and then fit the experimental data of coal adsorption methane at different constant temperatures. It is found that compared with the traditional Langmuir equation,the correlation coefficient of the modified Langmuir equation fitting curve is higher,and the standard errors of the adsorption constants a,b obtained by the combined regression are smaller. On the basis of the Langmuir equation correction model,the adsorption constants a,b and the correction coefficient c at different experimental temperatures are polynomial fitting to obtain the model of the coal adsorption methane content and temperature and pressure. The experiment shows that the adsorption and desorption curves of coal for methane at the same temperature do not overlap,and the desorption lags behind the adsorption. The higher the temperature,the smaller the distance between the adsorption and desorption curves,which indicates the weaker desorption hysteresis of methane by coal. The adsorption/desorption hysteresis evaluation model is used to quantitatively calculate the desorption hysteresis at different temperatures,and it is a negative exponential relationship between the amount of desorption hysteresis and temperature by curve fitting. From the perspective of adsorption heat,it is further revealed that the reason of for the desorption hysteresis is that the heat of adsorption is less than the heat of desorption,and the difference between the adsorption/desorption heat of coal to methane is smaller as the temperature increases,which leads to the smaller the amount of desorption hysteresis.