软硬煤瓦斯扩散系数动态变化规律的差异性
Difference of Dynamic Variation Laws of Gas Diffusion Coefficient of Soft and Hard Coal
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摘要: 为了研究软硬煤瓦斯扩散特征的差异性，选择淮南丁集、安阳龙山2种变质程度的软硬煤样，模拟了瓦斯吸附-解吸动态扩散过程，对比了软硬煤瓦斯扩散系数的动态变化特征。采用压汞法测定了软硬煤的孔隙结构参数，分析了软硬煤解吸扩散参数差异的产生机理。结果表明：软硬煤在解吸的初始阶段，软煤的扩散系数明显大于硬煤，但随时间衰减也更快；在整个扩散时间内，煤粒瓦斯扩散系数随放散时间呈现单调递减的减函数，即呈幂函数衰减，最终趋于稳定，扩散系数体现出时变性的特征；软煤的中孔和大孔孔容明显大于硬煤，以致软煤的扩散系数明显大于硬煤；储存于不同孔隙和位置的瓦斯扩散路径的差异是软硬煤瓦斯扩散系数随时间变化的原因。Abstract: In order to study the difference of gas diffusion characteristics of soft and hard coal, soft and hard coal samples from Huainan Dingji, Anyang Longshan Coal Mine with different degree of metamorphism were selected. And the dynamic diffusion process of gas adsorption desorption was simulated in the laboratory. The dynamic change characteristics of gas diffusion coefficient of soft and hard coal were compared. The pore structure parameters of soft and hard coal were determined by pressure mercury test to analyze the mechanism of difference of the desorption and diffusion parameters of the soft and hard coal. Results show that the diffusion coefficient of soft coal is obviously higher than that of hard coal at the initial stage of desorption, and faster decay over the time. The decreasing function which is monotonically decreasing is appeared for gas diffusion coefficient with the diffusion time throughout the diffusion time, and eventually tends to be stable, and the diffusion coefficient shows the characteristic of time variation. The volume of mesopores and macropors of soft coal is obvious higher than that of hard coal, which makes the gas diffusion coefficient of soft coal obviously higher than that of hard coal. The difference of gas diffusion paths, which are stored in different pores and positions, is the reason for the change of gas diffusion coefficient of soft and hard coal with time.
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