159 / 2023-07-05 19:36:51

Gas migration law and gas extraction optimization of extra-thick coal seam with hard roof

extra-thick coal seam ; gas migration ; high pumping alley

The No.3-5 coal seam of Tongxin Mine in Datong mining area belongs to the extra-thick coal seam. It has the characteristics of large thickness of mining coal seam, large amount of gas emission and wide range of mining influence. During the weighting period, the working face is easy to produce the potential safety hazard of gas overrun. Therefore, it is particularly important to clarify the law of gas migration in extra-thick coal seam and put forward corresponding prevention and control technology to solve the problem of gas overrun in working face. Fluent numerical simulation software was used to simulate the gas migration in the goaf of 8207 working face. The results show that under the condition of U-type ventilation in 8207 working face, gas accumulation occurs in the upper corner area, and the gas concentration can reach 5 %. The high drainage roadway is selected as the gas prevention and control technology of 8207 working face. Through the simulation results, it is determined that the vertical distance of the high drainage roadway is 18 m and the horizontal distance is 15 m as the best high drainage roadway layout orientation. At this time, the highest gas concentration in the upper corner is only 0.63 %, the highest gas concentration in the working face is only 0.57 %, and the gas extraction concentration is 3.92 %. The gas control effect of the working face under this layout scheme is the best. 7 kPa is determined as the best negative pressure of extraction, which can not only control the gas concentration in the working face and upper corner, but also avoid the danger of spontaneous combustion due to the excessive wind speed of air leakage. The optimal extraction weight range is determined to be 0.33 ~ 1. With the help of mine gas field monitoring data, it is concluded that the average gas concentration in the upper corner of the working face is 0.247 % after using the high drainage roadway as the gas prevention and control technology, and the average gas extraction rate during the pressure period of the working face can reach 80.8 %. Therefore, the gas prevention and control technology of high drainage roadway can effectively control the gas concentration of the working face.