动扩散系数新模型下不同粒径构造煤的瓦斯扩散特征

Features of gas diffusion in tectonic coal with different particle sizes by new model of dynamic diffusion coefficient

为揭示不同粒径构造煤的瓦斯扩散特征,采用瓦斯解吸仪分别在井下现场和实验室内开展了原煤样和不同粒径的构造煤瓦斯扩散实验,并采用低温氮吸附法测定其孔径分布,采用动扩散系数新扩散模型计算各类扩散实验的初始扩散系数D0及其衰减系数β、有效初始扩散系数De0和有效动扩散系数De(t)。结果表明:各类粒径构造煤的瓦斯扩散率初期增长较快,但衰减迅速。同时刻下,粒径越大,D0越大,β越小,构造煤中孔隙由表及里孔径逐渐缩小,正是这种孔径特征控制了D0和β的大小。同时,粒径越大De0和De(t)越小。与之相反,井下构造煤原煤样具有更小的粒径,致使原煤样的瓦斯扩散速度更快,因此构造煤具有更严重的突出危险性。

In order to reveal the features of gas diffusion in tectonic coal with different particle sizes,the gas diffusion experiments of raw coal sample and tectonic coal with different particle sizes were carried out both in laboratory and underground field by using gas desorption apparatus,and the pore diameter distribution of tectonic coal was measured by using low temperature nitrogen adsorption method. The initial diffusion coefficient D0 and its attenuation coefficient β,the effective initial diffusion coefficient De0 and the effective dynamic diffusion coefficient De（ t） of various diffusion experiments were calculated by using the new diffusion model of dynamic diffusion coefficient. The results showed that the gas diffusivity of tectonic coal with different particle sizes presents a faster increase in early stage,but attenuates rapidly. What ＇s more,the lager the particle size,the lager D0 and the smaller β. The pore diameter reduces gradually from surface to center in tectonic coal,and this pore diameter characteristic controls the magnitude of D0 and β. At the same time,the lager the particle size,the smaller both De0 and D（ t）. On the contrary,the raw coal sample of underground tectonic coal has smaller particle size,which results in the faster gas diffusion speed of raw coal sample,so the tectonic coal has more serious outburst hazard.