(Chongqing Branch of Coal Science Research Institute Chongqing 400037)
The prevention and control of coal mine gas disaster is the focus of all coal mining countries in the world. This paper briefly introduces the application, research status and progress of regional comprehensive technology aimed at creating intrinsically safe mines, including the prediction technology of gas disaster-prone areas, the evaluation technology of efficient gas drainage effect, and the monitoring and early warning technology of gas disasters.
Keywords coal mine gas disaster prediction technology; Drainage technology; Monitoring and early warning technology
Study on new technology of gas disaster prevention and control
Hu qianting
(Chongqing Branch of Coal Science Research Institute, Chongqing 400037)
Abstract: The prevention and control of gas disasters is the focus of general concern in coal-mining countries all over the world. This paper briefly introduces the research status, progress and application of several comprehensive technologies, such as gas disaster prone area prediction technology, gas effective drainage and drainage effect evaluation technology, and gas disaster monitoring and early warning technology, in order to build an intrinsically safe coal mine.
Keywords: gas disaster; Prediction technology; Extraction technology; Monitoring and early warning technology
The prevention and control of coal mine gas disaster is the focus of all coal mining countries in the world, especially in China, where gas disaster has become the number one killer of casualties in coal mines. In 2005, gas accidents accounted for 70.7% of major coal mine accidents, and the death toll exceeded 100. Since the founding of New China, there have been 22 coal mine accidents with the death toll exceeding 100, and 20 gas and coal dust explosions.
The research on coal mine gas disaster prevention and control technology has developed from a local single technology to a regional comprehensive technology aimed at creating intrinsically safe mines, including gas disaster prone area prediction technology, efficient gas drainage and drainage effect evaluation technology, gas disaster monitoring and early warning technology and so on. This paper briefly introduces the research situation of these technologies.
1 prediction technology of gas disaster-prone areas
Gas disasters are closely related to geological structures, and areas with complex geological structures usually belong to gas disaster-prone areas. In addition, gas disaster-prone areas usually contain high gas content, so predicting high gas content areas is also an effective means to predict gas disaster-prone areas.
Advanced geological structure detection technology, 1. 1 ground penetrating radar
Ground penetrating radar (GPR) is a directional high-frequency electromagnetic wave reflection positioning technology to determine the distribution of underground media. It has been widely used in geotechnical engineering and construction engineering. Through many years' efforts, Chongqing Branch of the General Research Institute of Coal Science recently developed an intrinsically safe geological radar suitable for the coal mine environment, which can detect geological anomalies such as small concealed structures in the coal and rock mass at the depth of 20 ~ 30m in the mining face in advance, and achieved good results through experiments in Xishan, Huainan and Songzao mining areas. In June 5438+February 65438+February 2004, the detection test of coal seam collapse column was carried out in 682 14 tail roadway of Duerping Mine in Xishan. It is found that the radar wave gradually attenuates from shallow to deep in the coal seam, while the radar echo is strongly reflected where there is a collapse column, and the in-phase axis basically forms an arc curve, which clearly reflects the interface between the collapse column and the coal seam and the size range of the collapse column (see Figure 650).
Figure 1 Detection Results of Column Collapse in Du Ping
The position and thickness of 2 # ~ 4 # coal seams in the auxiliary roadway of 22502 working face in Xiqu Coal Mine were detected. The detection results (Figure 2) show that the positions of 2 # coal seam floor and 4 # coal seam roof and floor are clearly reflected, and 4 # coal seam is basically stable within the survey area, with local ups and downs due to faults, and the average thickness of 4 # coal seam is 3.35m m.
Fig. 2 Test results of coal seam thickness in Xiqu Mine
In the auxiliary roadway of 282 10 working face in Xiqu Mine, the boundary of mined-out area is detected with sulfur head in advance: horizontal scanning is carried out along the surface of sulfur head, as shown in Figure 3. It can be seen that there is a strong reflection interface about 30 meters ahead, which is presumed to be an abnormal water-bearing area.
Fig. 3 Detection results of goaf boundary in Xiqu Mine
1.2 picosecond wavelength distance structure detection technology
P-S wavelength distance advanced structure detection technology mainly detects P-wave and S-wave reflected by seismic wave, which is used to analyze and predict geological structure, and can conveniently and quickly predict geological anomalies in coal and rock at the depth of100 ~150 m.
The experiment was conducted in S3-5 Pishun Lane, 740 Return Air Lane and 630 Belt Lane of Chang Cun Mine in Lu 'an from July 9 to June 5, 2005 1 and September 26, 2005/respectively.
Fig. 4 Detection Results of Collapse Column in Changcun Coal Mine
The exploration of S3-5 Pishun Lane in Changcun Mine (Figure 4) shows that there are many reflecting surfaces around 55.8 ~ 87.5 m, and the rock mass is broken, which may be the area affected by the collapse column. Driving roadway to 55m south of S3 return air mountain exposes a collapse column.
The detection of 740 return air roadway in Wangzhuang Mine (Figure 5) shows that there are reflection interfaces at 13.5 meters and 56.5 meters in front of the heading face, and there are some secondary reflection interfaces at 70 ~ 120 meters ... Actually, it is revealed that the F237 fault is a normal fault with strike 132 and dip angle of 20 meters.
Fig. 5 Fault detection results of Wangzhuang Mine
1.3 direct measurement technology of coal seam gas content
Gas content q refers to the gas content per unit mass of coal at 20℃ and one atmosphere. It consists of desorbable gas content and residual gas content, with the unit of m3/t, and its expression standard is raw coal. The value of desorption gas content Qm is equal to the sum of gas loss Q 1, gas desorption amount Q2 of coal sample and gas desorption amount Q3 of coal sample after crushing.
Drill the coal core into the coal seam structure, take out the coal core from the deep part of the coal seam, and put it in the coal sample tube in time to seal it, and record the time from the coring device to the sealing; Then, the gas desorption speed and desorption amount of coal core in the coal sample tube are measured underground, and the gas loss Q1is calculated according to the desorption speed and loss time; Take the coal sample cylinder to the laboratory, then measure the gas quantity released by the coal sample cylinder, and calculate the gas desorption quantity Q2 of the coal core together with the gas desorption quantity measured underground; Put the coal sample in the coal sample cylinder into a sealed crushing system for crushing, measure the amount of gas desorbed during the crushing process and for a period of time after crushing (under normal pressure), and calculate the amount of gas desorbed by crushing. The sum of gas loss, coal core gas desorption and pulverized coal gas desorption is the desorbable gas content, that is, Qm=Q 1+Q2+Q3. Then determine the quality of coal samples, and determine the residual gas content in the coal seam, and finally calculate the gas content in the coal seam.
The test system consists of coal sample cylinder, volume measurement system, gas composition determination system, coal sample crushing system and drilling sampling system, as shown in Figure 6. This method was tested in Huainan Mining Group and compared with the method of drilling cuttings to determine the content of desorbable gas. See table 1 for the test results. As can be seen from the table 1, the desorption accuracy measured by coring method is high. At the same time, compared with the gas emission in the process of roadway excavation (see Figure 7), the trend is obviously basically the same.
Fig. 6 Direct gas content determination system
This method can be used to measure a large number of coal seam gas content data in a large area, understand the distribution of coal seam gas content in various regions, and thus effectively predict the gas disaster-prone areas. At present, the depth of sampling borehole in the test reaches 50m, which is expected to meet the actual needs of coal mine production with the further improvement and expansion of the test.
Fig. 7 Comparison of gas content determination results
Table 1 comparison of test results of gas desorption measured by drilling cuttings method and coring method
2 Efficient gas extraction technology
2. 1 ground drilling to extract gas from coal seam or goaf in pressure relief area.
Gas drainage is the most fundamental means to prevent gas disasters. On the basis of some successful experiences at home and abroad, combined with the actual situation in Huainan mining area, we have carried out experimental research on gas drilling and mining technology in coal seam or goaf on the ground.
Fig. 8 is a borehole structure diagram for extracting gas from coal seams or mined-out areas in pressure relief areas through ground boreholes. When gas is extracted from the pressure-relieved coal seam, the borehole should enter the pressure-relieved coal seam. The test results of gas drainage in goaf of Xie Qiao Mine and Zhangbei Mine of Huainan Mining Group show that the boreholes should be arranged within 30m from the return air roadway, and the spacing between boreholes should be 200～300m. Fig. 9 is the drainage effect diagram of Xie Qiao Coal Mine, and Table 2 summarizes the flow rate and concentration of gas extracted from goaf by ground drilling in Huainan Mining Area. The gas flow rate of ground borehole drainage goaf in Panyi Coal Mine is 5 ~ 1.5m3/min, and the concentration is 60% ~ 85%. The gas flow rate of ground borehole drainage goaf in Zhangbei Coal Mine is 10 ~ 25m3/min, and the concentration is 60% ~ 80%. The gas flow rate of ground borehole drainage goaf in Xie Qiao Coal Mine is10 ~ 20m3/min, and the concentration is 60% ~ 90%. The goaf gas is extracted by ground drilling in Xie Yi Coal Mine, with the extraction amount of 4 ~ 5m3/min and the concentration of 50%.
Table 2 Gas Flow and Concentration of Surface Borehole Drainage in Huainan Mining Area
Fig. 8 Structure diagram of ground borehole for gas drainage in goaf
Xie Qiao Coal Mine Ground Borehole Drainage Goaf Gas Effect Map.
Through the above summary of the implementation effect of ground boreholes in Huainan mining area, it can be seen that: in general, when these boreholes work normally, the gas drainage volume and gas concentration are both high, with an average flow of 1.5m 3/min and an average gas concentration of 80%, and the drainage effect is good. When the working face pushes the borehole for 40 ~ 100 m, the gas flow and concentration in the borehole increase to the maximum (see figure 10).
Figure 10 Gas Flow and Concentration of Ground Borehole Drainage Goaf in Panyi Coal Mine
2.2 Underground Dendritic Long Borehole Bedding Pre-drainage Coal Seam Gas Technology
The VLD- 1000 directional drilling rig made in Australia was introduced into Daning Coal Mine, Shanxi Province, and the drilling direction was adjusted through the guiding and rectifying device, and the slag discharge mode and parameters were determined according to the coal seam strength. VLD directional drilling rig was put into use in Daning Coal Mine in April 2003. By the end of April, 2004, the total footage was 78,484 meters, setting a world record for directional drilling with a single directional drilling rig in VLD underground. By the end of September, 2004, VLD drilling rig had completed directional drilling 160, with the total footage reaching 1 127 16m, the longest drilling reaching 1005m and the length of 20 drilling holes exceeding 800m. See figure 16544 for drilling layout.
Figure 1 1 Daning coal mine bedding dendritic long borehole
The drainage effect of drilling holes with different depths was studied experimentally, and the drilling holes were divided into three groups: 800m, 600m and 400m according to the depth. 1000 m The drainage effect of long dendritic boreholes with different depths is shown in Table 3. It can be seen that the total drilling length of the group with drilling depth of 800m is 153% of that of the group with drilling depth of 400m, and the total cumulative drainage of the group with drilling depth of 400m is 1 year, the second year and the 800th day. The total drilling length of the group with drilling depth of 600 meters is 145% of that of the group with drilling depth of 400 meters, and the cumulative drainage on the first 1 year, the second year and the 800th day is 106% ~ 12 1% of that of the group with drilling depth of 400 meters.
Compared with 1 at the end of the second year, the cumulative total drainage of boreholes increased by 14% ~ 28%, while the cumulative total drainage at the end of 800 d only increased by about 1%. Therefore, the reasonable drainage time of drilling is 1 ~ 2 years.
The first mining face in Daning Coal Mine is 500 meters long and 320 meters wide. In 2003, the branch drilling of the 1000-meter drilling rig was started, with the drilling spacing of about15m (* *12 hole, 34 horizontal branches), the drilling depth of about 500m, and the total footage 1 1000 m. After investigation, the average total drainage amount of a single hole was/kloc. The content of coalbed methane in the first mining face is14m3. In 2005, the emission of coalbed methane was 184.8m3/min, of which the extraction amount was 130m3/min, and the extraction rate of coalbed methane was 70.35%.
Table 3 Analysis Table of Drainage Effect of Branch Long Boreholes with Different Depth and Kilometers
3 gas disaster monitoring technology
Gas disaster monitoring is the key means to discover the hidden danger of gas disaster in time, which mainly includes sensor technology and monitoring network system.
3. 1 infrared gas sensor technology
The infrared gas sensor mainly uses the principle that there is a definite relationship between the absorption performance of infrared light with a certain wavelength and the gas concentration, and works by measuring the absorption degree of infrared light with a certain wavelength to reflect the gas concentration value, as shown in figure 12.
Figure 12 Infrared Gas Sensor
The test results of the developed infrared sensor show that when the gas concentration is between 0% and 5%, the maximum absolute error is 0.06%CH4, the maximum linear deviation is 0.06%, and the average response time is 7.8s When the temperature changes from 0℃ to 40℃, the display error is 0.02%CH4, and the maximum zero drift of 10d stability test is 0.0/. At present, infrared gas sensors with the range of 0 ~ 10% and 0 ~ 40% CH4 have been developed.
3.2 Broadband Monitoring System
The backbone transmission platform of KJ90 distributed networked coal mine comprehensive monitoring system adopts industrial Ethernet communication technology based on I P, which directly extends the ground Ethernet technology to the underground environment of coal mine, and builds an advanced, reliable, standard, high-speed, broadband and two-way comprehensive information transmission platform for mine, which connects all kinds of monitoring equipment, automatic process control equipment, voice communication equipment and image monitoring equipment of mine safety and integrated automation system through IP. And realize the seamless connection with the overall Internet/Intranet architecture of coal mining enterprises, as shown in figure 13.
Figure 13 Functional Structure Diagram of Broadband Monitoring System
4 gas disaster early warning technology
The effective prevention and control of gas disasters is closely related to the level of mine management. However, there are many related factors in the occurrence of gas disasters, and these factors are dynamic, so it is difficult to grasp the changes and possible results of all related factors simply by relying on it. Therefore, we have carried out the research of gas disaster early warning technology. Through the establishment of a large number of information databases, the monitoring system monitors the changes of relevant influencing factors, and uses the relevant models obtained from experimental research to realize the early warning of gas disasters, and puts forward reasonable suggestions to eliminate the hidden dangers of gas disasters, so as to improve the management and decision-making level of mine safety production by technology.
The early warning system is developed based on ARC Infor three-dimensional geographic information system platform, which makes the process and results intuitive. At present, the main functions of gas disaster early warning system are: ① gas occurrence analysis and prediction; ② Prediction of regional coal and gas outburst risk; (3) coal and gas outburst risk prediction in coal mining face; ④ Real-time monitoring and prediction of gas concentration changes; ⑤ Gas explosion risk prediction; ⑥ Functional modules such as system management, mine map maintenance, input and output. Moreover, with the deepening of research, the function is continuously increased, and the model is modified through self-learning. Figure 14 is an interface of system software.
4. 1 gas geology and gas occurrence analysis and prediction
The analysis and prediction of gas geology and gas occurrence mainly aims at drawing gas pressure isoline, gas content isoline and the influence of geological structure on coal and gas outburst, and studies the prediction method and software calculation program of gas geological occurrence based on GIS technology. In this system, the functions of geological structure maintenance and query, geological unit division and intelligent identification, gas pressure isoline drawing of geological units, gas content isoline drawing, isoline distribution range query and distribution map query are mainly studied and developed.
Figure 14 Output result of gas pressure isoline
4.2 Regional Coal and Gas Outburst Risk Prediction
The prediction of regional coal and gas outburst danger mainly aims at drawing the distribution map of outburst danger area, and its prediction basis is the basic parameters such as gas pressure, gas content, geological structure and dynamic phenomenon measured in coal mines. The methods of regional prediction include gas geology method, comprehensive index method, borehole dynamic phenomenon judgment method and other phenomena comprehensive judgment method, and the result of regional prediction is the union of calculation results of various professional modules. The regional forecast results are divided into three levels: outburst threat area, outburst danger area and serious outburst danger area, and the result map can be queried, printed and published interactively.
4.3 Coal and gas outburst risk prediction in coal mining face
The prediction of coal and gas outburst danger in coal mining face is mainly divided into three parts: the prediction of coal and gas outburst danger in coal mining face, the prediction of coal and gas outburst danger in coal roadway driving face and the prediction of coal and gas outburst danger in crosscut uncovering face. The prediction data comes from three aspects: first, the daily prediction data of drilling outburst, including the value of gas desorption index K 1, the amount of cuttings s, the initial velocity of gas emission q and its attenuation index Cq, etc. Second, the dynamic indicators of gas emission in the working face, including the evaluation index V30(V60) of the change of gas emission in Nevas 30(60)min after shooting, and the real-time changes of gas emission in the working face monitored by the monitoring system. Three, geological structure, daily report parameter measuring points, historical mining conditions records, historical outstanding accident records.
4.4 Real-time monitoring and prediction of gas changes
The gas monitoring information comes from the monitoring system, and the task of the early warning server is to regularly read the required information (mainly the real-time value of gas concentration change) from the monitoring system server, and actively transmit it to the early warning server, and then store and display it according to the information requirements, and provide flexible query and statistical analysis functions through the software interface.
Because the monitoring system data is the basis of dynamic early warning of gas disasters, the data acquisition server program requires its own characteristics of stability, reliability and flexibility, and can not have any negative impact on the control system server. In the long run, it is necessary to merge the database servers of monitoring system and early warning system to reduce the waste of data storage resources and centralized management of data.
4.5 Gas explosion risk prediction
The gas explosion risk prediction is based on the gas concentration data monitored by the mine monitoring system in real time. After analysis and processing, the early warning indicators and methods of gas explosion disaster are studied to realize the early warning of gas explosion disaster, including two aspects:
(1) Analyze and judge three kinds of data stored in the database of monitoring system, and realize real-time warning of gas explosion danger;
(2) Analyze and judge according to the early warning results of coal and gas outburst, and realize the early warning of gas explosion risk under abnormal conditions.
4.6 System Management, Mine Map Maintenance and Input/Output
System management, mine map maintenance and input and output are the basis for the normal operation of this system.
(1) system management. System management includes general parameter setting, display style setting, user authority setting, coal mine department allocation and personnel setting, log management, system configuration state diagnosis, database backup and recovery, etc. The function module of system management is to provide guarantee for the normal operation of early warning system.
(2) Mine map maintenance. Mine map maintenance is mainly to maintain the map objects of the mine, including facilities and equipment maintenance, sensor maintenance, roadway maintenance, tunneling face maintenance, coal mining face maintenance, working face prediction measuring point maintenance, outburst accident point maintenance, goaf maintenance, protective belt maintenance, coal mining stage maintenance, mining area maintenance, gas occurrence parameters maintenance, geological structure maintenance, etc.
The design of mine map maintenance module is different from the traditional drawing method. In order to define the object strictly according to the object relationship of the early warning system, when maintaining the map object, it is required not only to accurately draw the mine map and its objects, but also to establish the topological relationship and association method between the objects.
(3) Input and output. Input and output function is the main means for early warning system to run and display early warning results. Input mainly collects data in three ways, namely: daily maintenance input, dynamic input of monitoring system and historical data analysis; Output methods include report printout, report online publishing, map printout and map online publishing.
In addition, the system also designed and studied disaster prevention measures and expert system knowledge base.
5 concluding remarks
Effective prevention and control of gas disasters is a long-term and arduous task, and the technical problems it faces will become more and more complicated. The technology introduced in this paper is some research progress in recent years. Some technologies have only been tested in some mining areas, and it still needs a process to achieve large-scale promotion. Especially the gas disaster early warning technology, it is more important to build a platform at present. Through the research of "Eleventh Five-Year Plan", the National 973 Plan and the National Natural Science Foundation, we will further establish and improve the early warning model, screen and improve the practical prevention technology, and make it have the practical software and hardware technology necessary for dynamic early warning of gas disasters through field trial application and self-learning, which really plays a key role in improving the safety level of coal mines.