煤粒瓦斯扩散行为的气压依赖性研究

Study on dependence of gas diffusion behavior in coal particles on pressure

为了研究煤粒瓦斯扩散系数对气压的依赖性,应用自主搭建的煤岩吸附瓦斯实验系统进行不同气压条件下的煤粒瓦斯扩散实验,并通过模型拟合得到不同气压条件下的扩散系数,分析扩散系数对气压的依赖性。研究结果表明:实验煤样具有双重孔隙结构;由于煤粒对瓦斯具有吸附性,导致模型拟合得到的扩散系数是表观扩散系数而不是真实扩散系数;表观扩散系数与真实扩散系数呈正比例关系,与等温吸附线斜率呈反比例关系;在低压阶段,煤粒瓦斯扩散由努森扩散主导,此时表观扩散系数与气压呈正比例关系;在高压阶段,煤粒瓦斯扩散由分子扩散主导,此时表观扩散系数与气压呈反比例关系。

To study the dependence of gas diffusion coefficient in coal particles on pressure,the gas diffusion experiments under different pressure conditions were carried out by using the self-developed experimental system on gas desorption of coal and rock. The diffusion coefficients under different pressure conditions were obtained through the model fitting,and the dependence of diffusion coefficient on pressure was analyzed. The results showed that the experiment coal sample has a dual porosity structure. The diffusion coefficient obtained through the model fitting is the apparent diffusion coefficient rather that the intrinsic diffusion coefficient due to the adsorbability of coal particles on gas. The apparent diffusion coefficient is positively proportional to the intrinsic diffusion coefficient and negatively proportional to the slope of the adsorption isotherm. In the stage of low pressure,the Knudsen diffusion dominates the gas diffusion in coal particles,and the apparent diffusion coefficient is positively proportional to pressure. In the stage of high pressure,the molecular diffusion dominates the gas diffusion in coal particles,and the apparent diffusion coefficient is negatively proportional to pressure.