变质程度对煤中瓦斯扩散规律的影响

Influence of metamorphic degree on gas diffusion law in coal

为研究瓦斯的吸附解吸特性及扩散规律对煤层气产量和开采难易程度的影响,通过高压瓦斯吸附解吸试验,探讨了变质程度影响下煤样中瓦斯的扩散规律。结果表明:随煤样变质程度增大,大分子结构增多使吸附空间增大的同时也加快了吸附进程,导致吸附能力增强,同时煤中对吸附解吸起抑制作用的小分子物质变少,导致能产生解吸的气体量变大,解吸能力变强;相对于较高变质程度的煤,低变质程度煤中的惰质组和壳质组能提供较多的大孔隙,从而使扩散空间增大,此外,低变质程度煤的惰质组中开放型孔隙含量较高,能加快扩散速率,使瓦斯扩散能力随变质程度的增大而减弱。

This paper aims to investigate the effect of adsorption-desorption characteristics and diffusion law of gas on the production of coalbed gas and mining difficulty.The study works by conducting an adsorption and desorption experiment of high-pressure gas to study the diffusion law behind gas in coal influenced by metamorphism.The results show that with the severe metamorphism of the coal,the increase of macromolecular structures enlarges the adsorption space and accelerates the adsorption process,resulting in the enhancement of adsorption capacity;and the small molecular substances in coal that inhibit adsorption and desorption become less,resulting in large amount of gas generating desorption and the desorption capacity enhanced.Compared with the coal with the higher metamorphic degree coal,the inert group and chitin group in low metamorphic degree coal can provide more large pores,and thus enlarge the diffusion space.In addition,the higher content of open cell pores in the inert group of low metamorphic degree coal,can accelerate the diffusion rate,weaken the gas diffusion capacity with the increase of metamorphic degree.