Application of gas drainage by drilling holes in t

With the increase of mining depth and intensity, the amount of gas emission continues to increase, and gas overrun has become a prominent contradiction that threatens safety and restricts production. Gas drainage has gradually become the main means to solve this contradiction, and it is also the requirement of the "Twelve character" policy of national gas control. This paper analyzes the successful application of roof high drilling to exhaust the gas in the fissure zone of the goaf in the East-West 23# right second mining face of Xinghua mine of Jixi Mining Group, and provides a basis for gas drainage in low permeability coal seams

1 overview of the second right in the East-West mining area of Xinghua mine

Xinghua mine is a large mine with an approved production capacity of 1.4 million T/A. It adopts high-standard common mining and stoping technology and long wall retreating mining method, with an average unit yield of 32 ~ 45 thousand T/month

Xinghua mine is a high gassy mine, with an absolute gas emission of 51.56m3/min and a relative gas emission of 17.97 m3/T. the coal seams are all low permeability coal seams. The 23 m # right second mining face in the East-West mining area is sometimes or even needs to improve the 4-ball machine. The inclined longwall retreating upward mining face has a reserve of 300000 t, a mining height of 2m, an absolute gas emission of 19m3/min and a relative amount of 21m3/T. the upward U-shaped ventilation is adopted in the working face, and the last mining face is used as the gas drainage roadway. Before drainage, the monthly production was 26000 t restricted by gas. After using the roof high-pressure drainage borehole to extract gas from the fissure zone, the monthly production was increased to 42000 T/month, which solved the threat of gas to production

2 selection of drainage method

according to the actual measurement, the gas content of the mining face of this coal seam accounts for 55% of the total gas of the mining face, while the gas released by the three sides of the goaf and the adjacent layers accounts for 45%, Because the coal seam is difficult to be drained (the permeability coefficient increases from 3/min to 9m3/min, and the drainage rate increases by 42% from 30%, which is in the most effective drainage range.

4 drainage effect. This is an economic analysis that every person on earth should do

(1) the gas drainage effect is remarkable. The gas drainage volume is 7.2m3/min, the gas drainage concentration is 55%, and the gas drainage volume is 10368m3/min per day. The gas concentration in the upper corner reduces the restorative milling process of complex workpiece after rough machining from 1.5% - 3.5% to 0.4% - 0.8%, the gas concentration in the return air decreases from about 1.0% to 0.4%, and the drainage rate reaches 38%

see Table 1

Table 1 air volume and gas parameters of working face after drainage

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(2) avoid human contact with high concentration gas and increase safety and reliability

(3) liberated the productivity

the monthly output was 29000 tons before pumping, and increased to 42000 tons after pumping, creating an additional benefit of 1.9 million yuan per month

5 conclusion

it is an effective method for gas drainage in goaf fractures by using roof high drainage boreholes, but the key points are to pay attention to the following aspects:

(1) single hole measurement must be carried out according to different roof lithology, and the best drilling parameters must be selected. The final hole of drilling is 7 ~ 15m away from the roof and 10 ~ 20m away from the air roadway

(2) the sealing of pumping holes must avoid the air leakage zone caused by geological structure and ground pressure

(3) the layout of drilling yard should not only avoid gas dens, but also consider that the smaller the length of hole forming and stubble pressing is, the more economical it is. It is best to choose high bypass drilling yard to construct parallel horizontal drilling in coal seams, which can reduce the length of stubble pressing and improve the utilization rate of drilling

(4) in order to improve the pumping rate, large-diameter pipelines and large-diameter boreholes should be used as far as possible