Influence of temperature on gas desorption-diffusion laws of coal particles

With the continuous increase in coal mining depth in China, temperature has a more and more apparent effect on the coal seam gas adsorption, desorption-diffusion, and seepage. To investigate the effect of temperature on the gas desorption and flow law of coal, the coal gas desorption test system by independent research and development is used. The gas desorption diffusion process of coal particles was studied under the conditions of adsorption equilibrium pressure 1.1 MPa and desorption temperature (20 degrees C, 30 degrees C and 40 degrees C). The variation law of the coal particle gas desorption-diffusion amount and the gas desorption-diffusion rate change with temperature are defined. Subsequently, the mathematical physics equations of coal particle gas desorption diffusion is established based on the third boundary condition, and the desorption-diffusion coefficient is solved by using the piecewise fitting method combined with the dynamic process characteristic of gas desorption-diffusion and the experimental data. The variation law of the gas diffusion coefficient change with temperature is found. The results show that: (1) the cumulative amount of coal particle gas diffusion desorption is a capped monotonically increasing function, and the higher the temperature, the faster the initial rate of gas desorption-diffusion. (2) in the short time (t < 10min), the gas desorption-diffusion coefficient decreases as the temperature increases, and when t > 10min, temperature change has little effect on the desorption-diffusion coefficient. This effect is mainly due to the fact that the rise in temperature accelerates the velocity of the gas molecules, therefore increasing the probability of collisions between the gas molecules. The diffusion length of gas molecules is reduced, followed by a decrease in the effective diffusion cross-sectional area. Finally, the gas desorption-diffusion coefficient is reduced. This provides theoretical guidance for the prevention of coal and gas outburst and the prediction of gas emission quantity and extraction.