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In recent years, national gas explosion accidents have occurred from time to time, causing huge losses to the state property and people's lives and safety, and causing very bad effects in society. Statistics at home and abroad indicate that the probability of gas explosion accidents in high gas mines is not very high. The gas emission abnormalities in low gas mines (gas emission abnormal areas: low gas mines according to relative gas emission and absolute gas emission) but in the daily production of gas emission peaks and valleys, the absolute gas emission amount is too large, the local area gas concentration often approach or exceed the "coal mine safety regulations" provides that pose potential threats to the security of production) but when gas An explosion occurred. The reason is mainly because the high gas mines attach great importance to gas management from management personnel to the majority of employees, with advanced equipment, high standard requirements, and strict operation according to regulations, so there is generally no explosion accident. On the contrary, low-gas mine workers, especially managers, are not in charge of gas management, and there is a lack of safety. The annual investment in safety is insufficient (it is important to say it, do it secondarily, don’t be busy), once local gas is overrun, there will be A gas explosion may occur.
Second, the mining area overview
Zaozhuang Mining (Group) Co., Ltd. has 11 pairs of mines, all of which are low-gas mines. Among them, Fucun Coal Industry Co., Ltd., Tianchen Mine and Chaili Mine have gas outflow anomalies.
In April 2000, the gas emission from the fully mechanized top coal caving face in the mining area was abnormal, and the amount of gushing was high. In the annual mine gas classification appraisal, it was designated as a gas anomaly zone by the provincial bureau. In July 2002, during the excavation of 3 215, the gas emission amount reached 5.25m 3 /min; in December 2002, after the 3 215 working face was put into operation, the absolute gas emission amount was 5~5.5m 3 /min. The working surface air volume is 1100m 3 /min, the gas concentration in the return air flow is about 0.5%, and the gas concentration in the return air angle is often around 1%. In 2001 and 2002, it was still designated as an abnormal gas zone by the provincial bureau.
(2) Tianchen Mine North Third Mining Area
During the construction of Tunneling 304 in October 1999, it was found that the concentration of gas in the blasthole was very high, and it was confirmed by relevant experts that it was caused by the invasion of igneous rock. In the subsequent excavation and coal mining process, gas emission abnormalities occurred many times, and many times were forced to stop and stop. In 2000, 2001 and 2002, they were designated as gas anomalies by the provincial bureau.
(3) Chaili Mine 233 Central Mining Area
In 2001, when gas inspection was carried out in the closed area of ​​the goaf, it was found that there was a high concentration of gas in the closed area of ​​the goaf, and a hole was drilled in the 2334 goaf in the 2333 working face. Within the gas concentration of 1.62% to 11.3%, according to the monitoring results and relevant data, it is determined that there is a gas anomaly zone in the 233 goaf, the range is roughly 2334, 2335 goafs and contact lanes. According to the analysis, the gas is abnormal. The main reason is that the temperature of the coal and rock mass around the fire area rises, which accelerates the desorption of gas in the original residual coal, which leads to an increase in gas emission. In 2001 and 2002, the provincial bureau was designated as an abnormal area for gas emission.
3. Analysis of the cause of the abnormal gas emission in the low gas mine in Zaozhuang mining area
(1) Magmatic rock intrusion
Due to the intrusion process of magmatic rock, the area has high temperature and high pressure and carries some hydrothermal gas, which promotes the deterioration of coal seam and produces new CH 4 gas. The rock wall itself acts as a non-breathable wall, preventing gas from escaping, thus forming The CH 4 enrichment area.
(2) Fault
Most of the faults have good sealing properties, and the gas release and drainage conditions are poor. The fault-related structures with large drop are damaged by the stress formed by the faults. They are relatively broken, and the micro-pores, joints and fissures develop, which provides a gas for the gas. With the existing space, the gas enrichment area with complex structures is formed. Once it is affected by the mining or the vibration of the shot, the gas will move and release quickly, forming an abnormal area of ​​gas emission.
(3) Gob area
The three-layer coal mined in the Zaozhuang mining area has a clamping pile of 0-20 m thick in the middle, which is divided into three upper and three lower layers. The mining sequence is generally the first mining of 3 coals and the mining of 3 coals. A large amount of gas is accumulated in the goaf. When the coal mining face of the 3 coal seams was mined, a large amount of gas emerged as the roof fell for the first time. For example, in January 2002, the Group’s subsidiary Fucun Coal Industry Co., Ltd.’s 3nd and 212th faces and the November 203nd and 203th tops of the roof fell for the first time, and the absolute amount of gas in the working face reached 15~19m 3 /min. The gas concentration in the return flow of the working face reached 2.2%, which caused the working face to stop production for 30 and 42 hours respectively.
Fourth, gas control technology
The Zaozhuang mining area is an old mining area with a long history of mining. Many mines are facing the problem of depletion of resources and economic difficulties. Based on the production geological conditions and economic conditions of Zaozhuang Mining Area, we have mastered the abnormal gas emission area in the mining area through careful investigation and research based on the principle of “guaranteeing production, eliminating hidden dangers, comprehensively managing, highlighting prevention, integrating points and focusing on effectivenessâ€. The basic situation, with the help of colleges and universities and professional research institutes, has gradually formed a simple, feasible, effective, practical and effective governance technology system in the long-term management of abnormal gas emission areas.
(1) Pressure equalization ventilation technology
The pressure equalization ventilation technology is suitable for the “island†coal mining face. In order to reduce the gas emission from the goaf, the damper is adjusted in the return air passage of the coal mining face to adjust the air volume, and the pressure increase and increase in the return air passage can be achieved to suppress the gas emission from the goaf. The amplitude of the pressure regulation should be predicted in advance. In order to overcome the blindness of the pressure regulation, the resistance should be measured in advance, and the pressure distribution map should be drawn, and the reasonable adjustment value should be determined through analysis and calculation. Generally, the pressure difference between the control and the adjacent goaf is 10 Pa. The mine ventilation system is a dynamic system that is affected by many factors. Strictly speaking, absolute or long-term balance is unrealistic. It can only be done to minimize the pressure difference and achieve temporary balance. As the pressure relationship between the goaf and the mining face changes with the advancement of the mining face, the relative balance may evolve into a new imbalance. Therefore, the pressure equalization state should be measured regularly. When the system or air volume changes, the wind pressure should be adjusted in time.
(2) pumping back the wind and corner gas
According to the particularity of mining face mining, the last row of cutting-top columns near the goaf in the return air channel is defined as the dividing line, and the goaf is inward, and the area is the area within the intersection of the wind and the surface. Return to the wind. Taking U-shaped ventilation as an example, gas is easy to form a vortex zone at the return air corner. Under the conditions of the laboratory, the scientific research on the wind current of the return air horn is found to be prone to gas accumulation or over-limit of the return wind angle, which is closely related to its wind flow condition, as shown in Figure 1. 
In the gas anomaly out of the anomalous area, the most common problem encountered was the gas concentration limit of the returning wind corner of the coal mining face. The most effective treatment method is to install a draft fan in the return airway. The usual method is to install a FSD2×18.5kW counter-rotating type local fan at 60~80m away from the coal wall of the working face. The installation uses a collapsible rigid air cylinder, and the air suction port of the air duct is extended to 0.5m below the top plate between the top and bottom cutting columns. The air outlet side is installed with a common flexible air duct, and the exhausted gas is directly introduced into the return air passage of the mining area. And installing a methane sensor in the suction side of the suction side and the exhaust side of the exhaust side, adjusting the suction air volume of the extraction fan, so that the gas concentration in the air flow in the extraction air tube does not exceed 3%, and the gas flow at the confluence side of the exhaust side is gas. The concentration does not exceed 1%.
(3) Reasonably increase the air volume and reduce the gas concentration
1. Coal mining face
When the coal mining face is topped and cycled for the first time, due to the collapse of the roof, the gas in the goaf (including the mining area on the surface, the mining area in the upper layer, the mining area in the upper coal layer) is flooded. Dilute the gas by reasonably increasing the air volume at the working surface, and drain the gas as soon as possible. The maximum air volume is limited to the wind speed of the working surface not exceeding 4m/s, generally reaching 1500~1800m 3 /min. At the same time, it is necessary to strengthen the comprehensive dustproof work of the working face to ensure that the coal dust in the return air flow does not exceed the limit.
2, tunneling work surface
When the excavation face encounters geological changes, the amount of gas emission will suddenly increase. At this time, in order to ensure normal safe production, the dual fan can be used to supply air, so that the air volume of the excavation face reaches 400-800 m 3 /min. The maximum air volume is limited to the wind speed of the roadway not exceeding 4m/s. At the same time, it is necessary to strengthen the comprehensive dust prevention work of the excavation working face to prevent the coal dust from exceeding the limit in the return air flow.
(4) Setting the air curtain
In order to reduce the gas concentration of the return air angle, a diagonal curtain can be installed in the working surface by using materials such as air duct cloth, and the air volume passing through the working surface can be led to the return air angle as much as possible to dilute the gas and ensure the gas concentration of the return air angle. Not over limit.
(5) Installation of safety monitoring system
Gas sensors are installed in all mining working faces and other important locations in the mine, and have a power-off function. When a certain gas concentration exceeds the limit, it can automatically alarm and power off to ensure that no gas explosion accident occurs. A voice alarm device is provided in the host of the ground center station. When the gas exceeds the limit, a voice alarm prompt is issued. The central station can also manually control the power-off or power-off according to the needs.
(6) Dual fan, dual power supply, automatic switching and dividing wind
Local ventilation management is the most difficult for gas outflow anomalies. To improve the reliability of local ventilation in recent years, we double fan, dual power in some mines, automatic switching means (Wuxi Jian proof electrical plant) by JDQB-2J local fan dual power switch automatically, greatly improving the local ventilation Machine reliability. That is to install two local ventilators, two power supplies, one for operation and one for standby. When one of the stalls stops for a reason, the other will automatically start within 5 minutes. When the fault is removed, it will automatically switch to another fan.
(7) Arranging the borehole pre-extracted gas
In order to master the initiative of gas control, high-concentration gas accumulated in goaf or geological structure belt can be arranged in advance, gas is extracted by gas drainage pump, and gas concentration is pumped below safety line to ensure future mining. The activity is safe and reliable.
V. Governance effect
After the implementation of the above technical measures, the safety situation of the gas outburst anomaly area in Zaozhuang mining area has obviously improved, and the location and number of gas overruns have dropped drastically, which has eliminated the occurrence of gas explosion accidents. The gas control effect is very obvious, as shown in Table 1, Figure 2. Shown.
The gas outburst anomaly zone poses a serious threat to the safe production of the mine. However, as long as we give full attention to the safety work of the gas outflow abnormal zone, we should take appropriate measures and implement it in place according to local conditions, and we can effectively control it. Production went smoothly.
Practice has proved that the above-mentioned methods and countermeasures that we have developed through research are effective and feasible, and have a high reference significance for the effective treatment of abnormal gas emission areas.
I. Introduction
(1) Fucun Coal Industry Co., Ltd. East Second Mining District
Figure 1 Schematic diagram of the tunnel wind flow structure
It can be seen from Fig. 1 that when the wind turns, the eddy current is formed at the corner (ADE), and the eddy current zone is also formed on the inner side wall after the wind flow turns, generally X≤1.2d, and the variation length L of the wind speed distribution with the frictional resistance coefficient Increase and decrease. For the I-beam support and the anchor net support roadway, L is (8-10)d. Of course, there are still many factors affecting the gas return from the return air corner when mining the actual coal mining face. However, it can be determined that the gas in the goaf is the main source of gas in the return air.
Figure 2 Gas emission abnormality treatment effect map
Table 1 Gas emission abnormal zone gas overrun times table
First quarter
Second quarter
third quater
Fourth quarter
total
1999
17
11
14
12
54
2001
11
10
7
8
36
2002
5
4
4
2
15
Conclusion
April 28, 2023