Gas drainage safety technical measures

(1) Long hole drilling technology. The key technology for gas drainage in the bedding layer is the hole-forming technology of the long hole in the bedding layer. When the coal seam (especially the protruding coal seam) is drilled in the coal seam, the sneezing L and the stuck drill are serious, and the hole penetration depth is often only 40. 70m, can not meet the depth of need for gas drainage in the face of coal mining face. To this end, during the "Ninth Five-Year Plan" period, the long borehole construction technology and equipment combined with the pressure slagging process, combined drilling tools and powerful drilling rig (ZSM-250 type bedding layer rig ) were studied, which greatly improved the drilling depth. Up to 100m, the deepest reaches 239m. The key to the pressure slagging process is to determine reasonable wind pressure and air volume. In order to use the compressed air to discharge the cuttings smoothly, the wind speed of the slag discharged in the borehole is usually required to reach 20m/s or more. Under the condition that the compressed air passes through the broken area, the wind pressure and air volume that meet the slag wind speed requirements are mainly Depends on the depth of the hole. The main function of the combination drilling tool is to improve the orientation accuracy of the drilling hole, while also reducing the chance of collapse and other large deformation of the drilling hole. The purpose of the powerful drilling rig is to increase the drilling capacity. The ZSM-250 powerful drilling rig has a diameter of 63mm. It can meet the requirements of 250m of protruding soft coal seam with the wind slag and combination drilling tools. The complete set of technology and equipment was tested in the underground of Qiquan Coal Mine of Furong Mining Bureau of Sichuan Province. The depth of the bedding drilling layer reached 239.6m, and the gas pre-pumping rate reached 32%. Compared with the mesh drilling, it can save The cost per ton of coal is 4.3 to 6.2 yuan. It not only protects coal mine safety, but also saves safety investment and reduces production costs. At present, this set of technology and equipment is being promoted and applied in the offices of Furong, Songzao, Fengcheng and Huainan, and has achieved good results.

(2) Long horizontal drilling technology for rock formations. The main purpose of long horizontal borehole drilling is to pump gas from the goaf and adjacent layers. Many coal mines in China originally used roof roadways to meet this requirement. If drilling is used instead of roadway, it will save a lot of investment. To this end, the theory of moving deformation of overlying strata in the stope is studied. Based on this, a reasonable layout and layout of the drill collar L are determined. Combined with the development of the MK-6 and 7 drilling rigs, the test has a successful hole depth of 500m or more. slate horizontal top layer and the layer adjacent to the long drilling plumb gob gas technology, the maximum amount of gas withdrawn 23.92m3 / min at No.5 single hole, the hole Nevas concentration up to 90%, the average amount of gas withdrawn hole 19m3 /rain, the average concentration of 60%, the effect is quite significant. The technology is used to drill the coal seam in the Jinchengsi River Mine (coal layer, value above 1), and the hole depth is more than 500m, which provides a reliable means for the development of coalbed methane.

(3) Long borehole pre-crack control blasting technology. The technology is to control the pre-splitting blasting of the coal seam, forcing the coal body to produce cracks to release stress and gas, so as to improve the permeability of the coal seam and prevent and control. In order to crack the coal seam during blasting without destroying the roof, special explosive formulations and blasting processes were studied. The test shows that the low-power explosives studied have the characteristics of slow detonation speed, low explosion peak and long acting time, and have good cracking effect on coal seams; the research of pressurized air jet charge, double detonator detonation double detonating cord, The double-detonating cord blasting three-stage coal mine allows the use of solid (powdered) emulsion explosives, and the long borehole controlled blasting technology with radial and axial uncoupled charge is effective, safe and reliable. The technology was carried out in Pingdingshan and Yangquan. In the experimental study, controlled blasting with a hole depth of about 70m was realized in Pingdingshan No.12 Mine.

(4) Hydraulic reaming technology. The larger the aperture, the larger the exposed area of ​​the drilled coal wall, the more favorable the stress release and gas emission. The single-diameter drilling construction faces serious boring, difficulty in slagging, short hole length and geometrical increase of rig load. And many other technical issues. The hydraulic reaming is to first drill a small-aperture borehole with a drill, and then use a high-pressure water jet that can spray a high-pressure water jet and rotate itself to rotate the coal body around the borehole. The motion creates a radially continuous reaming of the entire borehole. As the diameter of the borehole expands, the exposed area of ​​the coal seam increases, more coal is discharged, and the coal seam pressure relief range is further increased, which has a significant effect on increasing the amount of single-draw L-discharge (discharge) of the borehole. In the Zhongliangshan North Mine, the amount of gas drainage increased by 0.6 to 1.0 times after reaming; in the Songzao Mining Bureau, the gas drainage volume increased by more than one time after reaming, and the effect was very obvious.

(5) Gas drainage technology in goaf. Closed intubation and ground drilling and drainage are mainly adopted for goaf, but for coal seams with natural fire hazard, fire sign gas or temperature monitoring should be strengthened. At present, monitoring of fire mark gas and automatic control and regulation of drainage are being developed. Negative pressure and flow devices solve the contradiction between gas drainage and spontaneous combustion.

The extraction of the goaf in the mining face is mainly carried out by means of buried pipe drainage, closed drainage of the goaf by open cut-off side, drilling of the ground, roof and floor. Aiming at the characteristics of low gas concentration in the goaf, the CJK automatic pumping switch was developed. The principle is as follows: the gas concentration of the pumping and discharging pipeline, the gas concentration of the mine gas drainage system and the environmental gas concentration of the discharge section are monitored, so that the concentration of the pumping point or the system concentration in the low concentration pumping is not lower than one. When the value is set, the pumping system performs the pumping. When both values ​​are lower than the set value, it will automatically switch to the ejector ejector ejector state, which will be ventilated and diluted by the ejector to the discharge section; when the environmental concentration of the discharge exceeds the limit, the discharge will be automatically stopped. Under the condition that the gas concentration of the system is not lower than the set value and the safety is ensured, the pumping point gas is subjected to low concentration enhanced pumping. The device has been applied in the gas-enhanced pumping of open goaf in the initial mining period of a fully mechanized caving face of a coal industry group, and the effect is very obvious.

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