孔隙气体在煤层中扩散的机理

Diffusion Mechanism of Porous Gases in Coal Seams

分析了孔隙气体在煤体中的扩散模式和微观机理 ,得出在煤体中存在菲克型扩散、诺森扩散、过渡型扩散、表面扩散和晶体扩散几种扩散模式 ,并分析了抽放时瓦斯气体在煤层中的运移过程及其在煤微孔隙中的扩散过程 .根据分子运动论 ,从微观上讨论了压强和温度对甲烷分子平均自由程的影响规律 ,并解释了升高压强和温度增强甲烷气体在煤层微孔隙中扩散能力的机理 .分析了前人测定的不同压力下瓦斯在煤体中的扩散系数与分子平均自由程之间的关系 ,表明孔隙气体在煤微孔隙中扩散的宏观参数从根本上来看是由于分子微观参数的改变引起的 .

Diffusion modes and micromechanism of gases in coal were analyzed. It was found that in coal seams there are several diffusion modes including Fick diffusion, Knudsen diffusion, transitional diffusion, surface diffusion and crystal diffusion. The movement and diffusion processes of gas in coal seams during the drainage were described. The effect rules of pressure and temperature on the mean molecular free path of gas were discussed in microcosm according to molecular dynamics. The micromechanism of enhancing the diffusion ability of porous gases by increasing pressure and temperature was explained. On the basis of the relationship between the diffusion coefficients and the mean free path of gas molecules, it is shown that the macro-parameters of gas diffusion are determined by the micro-parameters of gas molecules.