静电场对煤体瓦斯扩散特性影响研究

Influence of electrostatic field on coal gas diffusion characteristics in coal

为探究静电场对煤体瓦斯扩散变化特性的影响,自主设计并构建瓦斯解吸-扩散试验系统,选取古汉山矿、鹤壁六矿、平顶山八矿和义马耿村矿4个矿区不同变质程度煤样,用以测定电场强度为0、40、120、240 kV/m下的解吸-扩散量,并利用经典单孔扩散模型计算各煤样在4种场强作用下的扩散系数。结果表明:静电场下,随着施加场强的增大,煤样扩散系数具有先增大后减小的变化特征,且呈抛物线状;特征优势场强为40 kV/m时各煤样扩散系数达到最大,而其他场强作用下扩散系数都有所减小;对比不同变质程度煤样电场下扩散特性,结果显示,平顶山八矿肥煤在电场下扩散系数最大,义马矿褐煤扩散系数最小。静电场下扩散特性变化原因为:煤体和瓦斯分子发生激发极化改变了煤体表面吸附势阱深度;电场能引起煤体内微小孔的体积和比表面积增加(减小)。

In order to explore influence of electrostatic field on gas diffusion characteristics in coal,a gas desorption and diffusion test system was independently designed,and desorption and diffusion volume of coals were measured under electric field intensity of 0,40,120 and 240 kV/m respectively with samples of different metamorphism selected from Guhanshan Mine,Hebi No.6 Mine,Pingdingshan No.8 Mine and Yimagengcun Mine.Then,their diffusion coefficient was calculated by using classical single hole diffusion model.The results show that diffusion coefficient of coal samples increases first and then decreases in a parabolic form along with increase of applied electric field strength.It reaches the maximum when characteristic dominant electric field strength is 40 kV/m,but will decrease while under other electric field intensities.Based on comparison of diffusion characteristics of these samples under electric field strength,it is found that coefficient of fat coal in Pingdingshan Mine is the largest while lignite in Yima Mine is the smallest.Reasons for diffusion characteristics variance under electrostatic field are that induced polarization of coal and gas molecules changes adsorption potential well depth on coal surface,and also electric field can cause volume percentage and specific surface area of micro pores in coal to increase(decrease).