水分对煤粒瓦斯扩散动态过程的影响规律

Effects of the moisture content on the dynamic process of the methane diffusion from coal particles

水分是含瓦斯煤粒扩散规律的重要影响因素之一,运用自制设备,试验研究当水分小于等于平衡水时,3种变质程度煤样的瓦斯扩散量、扩散速度和扩散系数随水分、扩散时间的变化规律;基于气体在多孔介质内的吸附解吸理论和Fick扩散定律,分析水分对瓦斯在煤粒内扩散动力参数和动态过程的影响机理。结果表明,在不大于煤样平衡水分条件下,高、中、低变质程度煤样的瓦斯极限扩散量、解吸速度和瓦斯扩散系数随水分增加而显著降低,同一种变质程度干燥煤样的瓦斯扩散系数基本是平衡水分煤样的3~5倍;水分的增加降低了煤粒内的瓦斯初始质量浓度和扩散系数,进而大幅度降低了瓦斯扩散速度;水分子更容易占据煤基质表面吸附位,致使煤对瓦斯的吸附量减少,水分子在煤粒内表面发生多层吸附,而堵塞部分的瓦斯分子在煤粒内表面扩散,缩小了扩散通道,增大了瓦斯扩散阻力,导致含瓦斯煤粒的瓦斯扩散系数减小。

This paper is aimed at introducing its research results of the influential factors of the moisture content upon the emission of the coal gas-containing particles. Therefore, we have done an experimen- tal study with the variation regularity of the diffusion flux, the diffu- sion speed and the coefficient with the moisture content by using a piece of self-developed equipment. As is known, it is easy to analyze the moisture content effect on the dynamic diffusion parameters and the dynamic process of the coal particles containing gas in accordance with the gas volume in the porous media adsorption and desorption theory and Fick＇ s law of diffusion. The results of our experimental study show that the flux, the speed and the coefficient of the diffusion may all tend to decrease obviously with the increase of the moisture content till the moisture content reaches its equilibrium. What is more, we have also worked out the diffusion coefficients of the three rank coal particles in correspondence with the mathematical model of the coal particles containing gas, which let us know that the diffusion coefficient of the coal particles containing gas tends to decrease with the improvement of the gaseous water, until the diffusion coefficient of the dry coal particles is getting to 3 - 5 times as big as one of the coal particles with the equilibrium moisture content under the same rank coal particles. According to the transfer theory of the porous media, it would be possible for the initial mass concentration and diffusion coefficient to decrease by improving the moisture Content, which tends to lead to the slow down of the diffusion speed l On the other hand, the water molecules tend to take more easily adsorbed sites than the methane molecules, so that the adsorption flux of methane gets reduced. At this, the multilayer adsorption would take place in the water molecules, which are likely to impede the surface diffusion of part of the methane molecules, and in turn block partly the diffu- sion path with the increase of the diffusion resistance.