Influence of temperature on gas desorption-diffusion laws of coal particles
Résumé
With the continuous increase of coal mining depth in China, the temperature has more and more apparent effect on the coal seam gas adsorption, desorption-diffusion, seepage, et al. To further 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 was used and the gas desorption diffusion process of coal particles was experimental study under the conditions of adsorption equilibrium pressure 1.1MPa and desorption temperature (20℃,30℃and 40℃). The variation law of the coal particles gas desorption diffusion amount and the gas desorption diffusion rate change with temperature were defined. Then the mathematical physics equations of coal particle gas desorption diffusion was established based on the third boundary condition, and the desorption diffusion coefficient was 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 was got. The results show that: (1) the cumulative amount of coal particles 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, the temperature changes has little effect on the desorption-diffusion coefficient. It mainly because the rise of temperature accelerates the gas molecules velocity, it increases the collisions probability between the gas molecules, and the diffusion length of gas molecules becomes smaller, then the effective diffusion cross-sectional area decreases, at last the gas desorption diffusion coefficient reduces. It provides theoretical guidance for the prevention of coal and gas outburst, prediction of gas emission quantity and gas extraction, etc.
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