煤矿井下护孔筛管煤粉颗粒通过性分析及抽采效果试验

Analysis of coal particles passing screen pipe and test of gas drainage effect in underground coal mine

煤矿井下煤层钻孔后筛管完孔已成为碎软煤层瓦斯抽采的有效护孔措施。为了研究常规圆孔筛管和割缝筛管的缝眼参数变化对瓦斯抽采效果的影响规律,基于离散单元法,利用PFC3D离散元分析软件建立了煤粉颗粒通过筛管的颗粒流模型,对煤粉颗粒在围压下穿过筛管筛眼或割缝的体积量进行了模拟,研究了筛眼直径、割缝宽度和割缝长度等参数变化对煤粉颗粒通过筛管性能的影响规律;结合模拟分析结果,设计了3种割缝筛管和1种圆孔筛管,并在淮北童亭煤矿864工作面进行了瓦斯抽采效果试验。模拟分析结果表明:同样过流面积下,筛管煤粉通过体积量随筛眼直径或割缝宽度和长度的增加而线性增大,同一筛眼直径和割缝宽度下煤粉通过体积量基本相当,且筛眼直径和割缝宽度对于煤粉通过体积量的影响要远大于割缝长度。现场抽采试验表明:3组割缝筛管瓦斯抽采纯量分别比圆孔筛管提高60.0%,43.3%,33.4%,且抽采51 d后的瓦斯混合流量和纯量也分别是圆孔筛管的约4倍,2.5倍和1.5倍以及约2.5倍,2倍和1.5倍,结合10 mm圆孔筛管煤粉体积通过量分别是缝宽2,3,4 mm割缝筛管的22,6,3.3倍,可以发现减小筛管的煤粉体积通过量可有效提高筛管在整个抽采过程中的抽采混合量和瓦斯纯量。

The completion of screen pipe after coal seam drilling has become an effective hole protection measure for gas drainage in broken and soft coal seam.In order to study the influence of the slitting parameters of conventional round-hole screen pipe and slotted screen pipe on the gas drainage effect,this paper built the particle flow model of coal particles passing through screen pipe with PFC3D software on the basis of discrete element method,and analyzed the ability of coal particles passing through screen pipe,as well as the influence of parameters,including the diameter of round-hole,the width of the slotting and the length of the slotting by simulating the coal particles passing through screen pipe under confining pressure.According to the simulation result,the gas drainage tests of the round-hole screen pipe and three kinds of the slotted screen pipe with different slotting parameters were carried out in the coal seam of 864 working face at Tongting coal mine in Huaibei,China.The results of numerical simulation show that the passing volume of coal particles increases linearly with the increase of round-hole diameter or slotted width and length under the same flow area,the passing volume of coal particles is basically the same under the same round-hole diameter and slit width,and the influence of round-hole diameter and slit width on the volume of coal particles passing through is far greater than the slit length.The gas drainage test shows that the net volume of gas drainage of three groups of slotted screen pipes is 60.0%,43.3%and 33.4%higher than that of round-hole screen pipes,and the gas mixing flow and net volume after 51 days of drainage are about 4 times,2.5 times and 1.5 times of the round-hole screen pipes.Combined with the fact that the volume of coal particles passing through the10 mm round hole screen pipe is 22,6 and 3.3 times of the slit width of 2 mm,3 mm and 4 mm slotted screen pipe respectively,it can be found that reducing the volume of coal particles passing through the screen pipe can effectively improve the drainage mixing flow and gas net volume during the whole drainage process.