A method for determining spontaneous combustion three zones of a fully mechanized working face goaf of a spontaneous combustion mine

Abstract

The application discloses a method for determining spontaneous combustion three-zone of a goaf of a fully-mechanized working face of a spontaneous combustion mine, and comprises the following steps: arranging a plurality of ground wells on the ground above a non-mining working face; sealingly connecting a gas extraction pump and a ground well wellhead through a gas extraction pipeline; when the working face is close to the ground well, starting the gas extraction pump, monitoring the oxygen concentration in the gas extraction pipeline, and stopping the monitoring when the working face has passed the position of the ground well and the oxygen concentration is stable; and determining the width of the spontaneous combustion three-zone of the goaf according to the oxygen concentration. The application can monitor the oxygen concentration and flow variation in the goaf in real time at the wellhead end of the ground well, determine the spontaneous combustion three-zone width of the left-over coal resources in the goaf according to the oxygen concentration, and provide a new determination method, thereby providing a reference for the effective implementation of the fire prevention and extinguishing work of the goaf of a high-gas or coal and gas outburst mine.

Description

Technical Field

[0001] This invention relates to the field of underground safety detection and prevention technology in coal mines, and in particular to a method for determining the three spontaneous combustion zones in the goaf of a fully mechanized mining face. Background Technology

[0002] With the increasing number of high-gas coal mines and coal and gas mines in my country, the gas control technologies and methods employed have become more complex and diverse. Besides using protective layer mining, directional long-bore drilling, and other underground gas extraction measures for pre-gas control in high-gas outburst coal seams, surface drilling extraction has gradually become the main technology for pre-extraction before coal seam development in most parts of my country. Due to the multiple advantages of surface drilling, such as not occupying underground roadway space and not being affected by the progress of underground roadway construction, surface drilling pre-extraction, surface drilling extraction before mining and during longwall mining, and extraction of goaf areas after mining have all been applied in most mines.

[0003] Spontaneous combustion in goafs is a major natural hazard that must be addressed when mining spontaneously combustible or easily combustible coal seams. To prevent spontaneous combustion of coal resources left in goafs, most mines have upgraded their fully mechanized mining technology and equipment, moving from top-coal caving mining to full-height mining in a single pass. They have also strengthened top-coal caving and production process management during the mining phase, reducing the amount of coal left in the goaf. The main purpose is to reduce the probability of spontaneous combustion in the goaf. However, due to the complexity of coal production processes and the influence of objective geological conditions, the presence of coal resources left in goafs is always unavoidable. To prevent spontaneous combustion in goafs, it is necessary to determine the three zones of spontaneous combustion in the goaf under specific production processes and levels, in order to implement targeted fire prevention and extinguishing measures. In existing technologies, the method for determining the width of the three spontaneous combustion zones based on oxygen concentration involves measuring the oxygen concentration underground by passing through pipelines from the unsealed area to the sealed area. Due to the complex and variable working environment underground and the influence of positioning accuracy, the measurement results are difficult to guide fire prevention and extinguishing work in goaf areas. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, embodiments of the present invention propose a method for determining the three spontaneous combustion zones in the goaf of a fully mechanized mining face.

[0006] This invention proposes a method for determining the three spontaneous combustion zones in the goaf of a fully mechanized mining face, comprising the following steps:

[0007] (1) Arrange several surface wells on the ground above the unmined working face;

[0008] (2) The gas extraction pump and the wellhead of the surface well are sealed and connected through the gas extraction pipeline;

[0009] (3) When the mining face approaches the surface well, start the gas extraction pump and monitor the oxygen concentration in the gas extraction pipeline. Stop monitoring when the mining face has passed the surface well and the oxygen concentration remains stable.

[0010] (4) Determine the width of the three spontaneous combustion zones in the goaf based on the oxygen concentration.

[0011] In some embodiments, drilling is stopped when the surface well reaches 5-10m above the coal seam roof.

[0012] In some embodiments, the surface well is located in the solid coal between the working face intake airway and the working face return airway, and is closer to the side of the working face return airway.

[0013] In some embodiments, a multi-parameter instrument is installed on the gas extraction pipeline, and the multi-parameter instrument is connected to the mine gas monitoring system.

[0014] In some embodiments, the gas extraction pipeline is further provided with a valve, which is used to temporarily seal the surface well.

[0015] In some embodiments, the gas extraction pipeline is further provided with a manual verification port, which is used to verify the multi-parameter instrument.

[0016] In some embodiments, the gas extraction pump has an extraction negative pressure of 15-30 kPa and a flow rate of 30-50 m³ / h. 3 / min.

[0017] In some embodiments, when the working face to be mined is close to the surface well, the vertical distance between the cut-in and the surface well is 30-50m.

[0018] In some embodiments, monitoring is stopped when the mining face has passed the location of the surface well and the oxygen concentration remains stable for 5-10 days.

[0019] In some embodiments, an oxygen concentration greater than 18% is a heat dissipation zone, an oxygen concentration less than 10% is an asphyxiation zone, and an oxygen concentration between 10% and 18% is an oxidation zone.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This invention provides a new method for determining the three-zone width of spontaneous combustion of abandoned coal resources in the goaf by real-time monitoring of oxygen concentration and flow rate changes at the wellhead of the surface well, and provides a reference for the effective implementation of goaf fire prevention and extinguishing work in high-gas or coal and gas outburst mines.

[0022] The method for determining the three zones of spontaneous combustion in goaf proposed in this invention is simple and quick to operate, and the measurement results are more accurate and reliable compared with previous methods such as empirical methods and numerical simulations. Attached Figure Description

[0023] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0024] Figure 1 This is a diagram showing the distribution pattern of the three zones of spontaneous combustion in the goaf of a fully mechanized mining face.

[0025] Figure 2 A cross-sectional view of the surface well layout provided in an embodiment of the present invention;

[0026] Figure 3 A plan view of the ground well layout provided for an embodiment of the present invention;

[0027] Figure 4 This is the measured oxygen concentration curve of well No. 1 in this embodiment of the invention;

[0028] Figure 5 This is the measured oxygen concentration curve of well No. 2 in this embodiment of the invention;

[0029] Figure 6 This is the measured oxygen concentration curve of well No. 3 in this embodiment of the invention;

[0030] Explanation of reference numerals in the attached figures:

[0031] Surface well 1, Surface wellhead 2, Surface well bottom end 3, Coal seam 4, Cutting hole 5, Valve 6, Manual calibration port 7, Positive pressure side of extraction pump 8, Gas extraction pump 9, Negative pressure side of extraction pump 10, Multi-parameter instrument 11, No. 1 surface well 12, No. 2 surface well 13, No. 3 surface well 14, Fully mechanized mining face 15, Intake airway 16, Goaf 17, Oxidation zone 18, Return airway 19, Heat dissipation zone 20, Asphyxiation zone 21, Gas extraction pipeline 22. Detailed Implementation

[0032] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0033] The following describes, with reference to the accompanying drawings, a method for determining the three spontaneous combustion zones in the goaf of a fully mechanized mining face according to an embodiment of the present invention.

[0034] The method for determining the three spontaneous combustion zones in the goaf of a fully mechanized mining face of a mine, according to the present invention, includes the following steps:

[0035] (1) Arrange several surface wells 1 on the ground above the unmined mining face;

[0036] (2) The gas extraction pump 9 and the surface wellhead 2 are sealed and connected through the gas extraction pipeline 22;

[0037] (3) When the mining face approaches the surface well 1, start the gas extraction pump 9 and monitor the oxygen concentration in the gas extraction pipeline 22. Stop monitoring when the mining face has passed the position of the surface well 1 and the oxygen concentration remains stable.

[0038] (4) Determine the width of the three spontaneous combustion zones in the goaf based on the oxygen concentration.

[0039] In step (1), before the construction of surface well 1, the geological data of the coal seam and coal rock of the mine, the distribution of mining faces set in the mine production connection plan, one or more surface wells 1 are designed and constructed above the planned non-mining mining face, and the surface drilling is completed before coal production is carried out in the fully mechanized mining face 15.

[0040] Construction of surface well 1 was carried out according to the designed construction process. Surface well 1 was located in the solid coal between the intake airway 16 and the return airway 19 of the working face. The drilling was carried out vertically and located on one side of the return airway 19 of the working face.

[0041] When surface drilling reaches above the coal seam roof, drilling is stopped and the well is completed. In some embodiments, surface well 1 is drilled vertically downwards to 5-10m above the coal seam roof, that is, drilling stops when the bottom end 3 of the surface well is 5-10m above the coal seam 4. Therefore, surface well 1 of the present invention is a goaf well, which is used to extract the large amount of gas that emerges after coal mining.

[0042] In some embodiments, such as Figure 3 As shown, above the longwall mining face 15, in the solid coal between the intake airway 16 and the return airway 19, three surface wells 1 are arranged near the return airway 19, namely surface well 12, surface well 13, and surface well 14. Surface well 14 is close to the face cut-out 5, and after the face is mined, it forms a goaf 17.

[0043] After the surface well 1 is constructed, the gas extraction pump 9 and the surface wellhead 2 are sealed and connected through the gas extraction pipeline 22.

[0044] like Figure 2 As shown, after the surface well 1 is constructed in place, a gas extraction pump 9 is installed near the wellhead 2. The gas extraction pump 9 is then sealed to the wellhead 2 via a gas extraction pipeline 22. The gas extraction pipeline 22, the gas extraction pump 9, and the wellhead 2 are sealed together to ensure a tight, leak-proof connection. During extraction, the gas extraction pump 9 performs negative pressure extraction from the surface well 1. The side of the gas extraction pump 9 closest to the wellhead 2 is the negative pressure side 10, and the side of the gas extraction pump 9 furthest from the wellhead 2 is the positive pressure side 8. The gas extracted from the surface well 1 by the gas extraction pump 9 is transported via pipeline to other gas-using locations or discharged.

[0045] The gas drainage pipeline 22 is equipped with a multi-parameter analyzer 11, a valve 6, and a manual calibration port 7. The multi-parameter analyzer 11 is connected to the mine gas monitoring system. The multi-parameter analyzer 11 can monitor the concentration and flow rate of various gases such as carbon monoxide, methane, oxygen, and acetylene in the gas drainage pipeline 22 in real time. The monitoring data from the multi-parameter analyzer 11 is integrated into the mine gas monitoring system and can be recorded and viewed in real time. The manual calibration port 7 is used to calibrate the multi-parameter analyzer 11. The valve 6, located on the gas drainage pipeline 22, prevents accidental operation or leakage of water or other gases from the bottom of the surface well 1.

[0046] Before production begins at the working face, the gas extraction pump 9 is shut down. At this time, the valve 6 installed on the gas extraction pipeline 22 is closed to temporarily seal the surface well 1.

[0047] When the mining face approaches the surface well 1, start the gas extraction pump 9 and monitor the oxygen concentration in the gas extraction pipeline 22 until the oxygen concentration remains stable.

[0048] Specifically, during the backfilling of the working face, the vertical distance between the cut-in 5 and the surface well 1 is monitored. When the distance between the cut-in 5 and the surface well 1 is 30-50m, valve 6 on the gas extraction pipeline 22 is opened, and the gas extraction pump 9 is started to carry out uninterrupted negative pressure extraction. The oxygen concentration change in the gas extraction pipeline 22 is monitored using a multi-parameter instrument 11. After the working face has been backfilled past the position of the surface well 1, and the oxygen concentration monitored in the gas extraction pipeline 22 of the surface well remains stable for 5-10 days, the observation is stopped.

[0049] The multi-parameter instrument 11 is connected to the mine gas monitoring system. During the extraction process, the multi-parameter instrument 11 transmits test data to the gas monitoring system, so that the oxygen concentration can be viewed in real time through the gas monitoring system.

[0050] During the sampling process, the test data from manual verification port 7 is compared with the test data from multi-parameter instrument 11 to ensure the accuracy of the test data from multi-parameter instrument 11.

[0051] During the extraction process, the gas extraction pump 9 operates at a negative pressure of 15-30 kPa and a flow rate of 30-50 m³ / h. 3 / min.

[0052] The three zones of spontaneous combustion in goaf can be divided using methods such as wind speed method, oxygen concentration method, temperature method, and numerical simulation. In this invention, the oxygen concentration method is used, which is based on the distribution of oxygen concentration from the outside to the inside of the goaf. Among them, oxygen concentration >18% is the heat dissipation zone, oxygen concentration between 10% and 18% is the oxidation zone, and oxidation concentration <10% is the asphyxiation zone.

[0053] like Figure 3 As shown, during the longwall mining process, this invention involves sequentially testing the three spontaneous combustion zones of the goaf at the locations of surface well 12, surface well 13, and surface well 14. This is equivalent to testing the three spontaneous combustion zones of the goaf, thereby repeatedly verifying the accuracy of the method of this invention.

[0054] When surface wells are used to extract gas from the goaf, the airflow within the goaf will intensify, allowing more fresh air to enter. The spontaneous combustion zones within the goaf are significantly different from those in traditional goafs where surface wells are not used for extraction. If traditional fire prevention and extinguishing methods are still used without considering the current state of gas management in new fully mechanized mining faces, it will result in ineffective fire prevention and extinguishing measures or waste of human, financial, and material resources due to blind implementation of fire prevention and extinguishing measures.

[0055] This invention provides a novel method for determining the width of the three spontaneous combustion zones (heat dissipation zone 20, oxidation zone 18, and asphyxiation zone 21) of abandoned coal resources in goaf areas by real-time monitoring of oxygen concentration and flow changes at the wellhead. This method offers a reference for the effective implementation of goaf fire prevention and extinguishing work in high-gas or coal and gas outburst mines. The proposed method for determining the three spontaneous combustion zones in goaf areas is simple and quick to operate, and the results are more accurate and reliable compared to previous methods using empirical methods and numerical simulations.

[0056] This invention utilizes existing methods for gas drainage in surface wells in many high-gas and coal and gas outburst mines in my country. It involves pre-draining gas from the original coal seam before coal mining, and intensified drainage during and after mining to prevent gas exceedance accidents caused by large-scale gas outbursts during high-intensity mechanized mining. Based on existing surface well construction, real-time monitoring of oxygen in the extracted gas is conducted during the working face's passage through the surface well to determine the three spontaneous combustion zones in the goaf. This method eliminates the need for additional surface drilling, achieving multiple uses from a single well, saving costs, and allowing for repeatable monitoring of this key fire prevention and extinguishing parameter, with stable and reliable results.

[0057] The method of this invention was applied to the western mining area of ​​Weijiadi Coal Mine, where three surface wells, designated as Well No. 1, Well No. 2, and Well No. 3, were designed and constructed above the planned longwall face. Using the method of this invention, a multi-parameter instrument was employed to statistically analyze the changes in oxygen concentration in the goaf corresponding to Well No. 1, Well No. 2, and Well No. 3. The measured oxygen concentration curves for Well No. 1, Well No. 2, and Well No. 3 are shown below. Figure 4 , Figure 5 and Figure 6 As shown. For ease of understanding, the coordinates of the distance between the drilling rig and the pushline are plotted on the upper and lower sides of the horizontal axis. From Figures 4-6 It can be seen that the oxygen concentration generally decreases as the distance between the drilling and pushline increases, eventually stabilizing. According to... Figure 4 The relationship curve between the distance between the drilling and pushline and the oxygen concentration can be used to determine the width of the three spontaneous combustion zones in Well No. 1, proving the feasibility of the method of this invention. Similarly, based on... Figure 5 and Figure 6 The relationship curve between the distance between the drilling and pushline and the oxygen concentration can be used to determine the width of the three spontaneous combustion zones in wells No. 2 and No. 3. Repeated observations were conducted to verify the method of this invention, making the results stable and reliable.

[0058] Specifically, based on the method for determining the three spontaneous combustion zones in the goaf of surface wells, engineering practice was carried out in the fully mechanized longwall face of the 1103 extra-thick coal seam. The North 1103 coal seam has an average thickness of 13m, a strike length of 850m, a dip length of 200m, and a recovery rate of 92%. According to the prediction of mine gas emission, the main source of gas in the working face is gas emission from the goaf, and the shortest ignition period of the coal seam is 36 days. Drilling parameters: The first borehole uses a Φ311.1mm diameter hole to penetrate the loose layer and a Φ244.5mm surface casing is installed; the second borehole uses a Φ215.9mm diameter hole to drill to the top of the expected fracture zone and a Φ177.8mm casing is installed; the third borehole uses a Φ152mm diameter hole for open-hole completion; the fourth borehole uses a 108mm diameter hole to terminate at the roof of the main coal seam.

[0059] Implementation Results: Three surface decompression and extraction wells were drilled at the 1103 working face. During the working face recovery period, parameters such as oxygen and methane concentrations extracted from the wells were measured daily. After three rounds of verification, the distribution range of the three spontaneous combustion zones in the goaf was determined. When the working face push line was 0-35m from the surface well position, the O2 concentration was approximately 18%-21%; when the working face push line was 35-67m from the surface well position, the O2 concentration was approximately 8%-18%; and when the working face push line was more than 67m from the surface well position, the O2 concentration was below 8%. After identifying the three spontaneous combustion zones in the goaf, grouting holes and nitrogen injection holes were constructed in the ventilation and return airways of the fully mechanized longwall face. The final hole location was 35m behind the goaf. As the working face advanced, the remaining coal within 30m of the goaf, passing through the oxidation zone, was isolated and oxidized by grouting with yellow mud or injecting nitrogen, thus disrupting the air leakage, oxygen supply, and heat storage environment, and eliminating the possibility of spontaneous combustion of coal. With this measure, it was no longer necessary to seal the goaf with sprayed materials at the lower end of the working face. Calculations showed that 15,936 yuan was saved for every 30m of working face advancement, resulting in a total saving of 1,221,760 yuan in fire prevention and extinguishing costs for this working face.

[0060] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0061] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0062] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for determining the three spontaneous combustion zones in the goaf of a fully mechanized mining face, characterized in that, Includes the following steps: (1) Arrange several surface wells on the ground above the unmined working face; (2) Seal the connection between the gas extraction pump and the surface wellhead through the gas extraction pipeline; (3) When the mining face approaches the surface well, start the gas extraction pump and monitor the oxygen concentration in the gas extraction pipeline. Stop monitoring when the mining face has passed the surface well and the oxygen concentration remains stable. (4) Determine the width of the three spontaneous combustion zones in the goaf based on the oxygen concentration.

2. The method as described in claim 1, characterized in that, Drilling of the surface well should be stopped when it reaches 5-10m above the top of the coal seam.

3. The method as described in claim 1, characterized in that, The surface well is located in the solid coal between the intake airway and the return airway of the working face, and is closer to the side of the return airway.

4. The method as described in claim 1, characterized in that, A multi-parameter instrument is installed on the gas extraction pipeline, and the multi-parameter instrument is connected to the mine gas monitoring system.

5. The method as described in claim 1, characterized in that, The gas extraction pipeline is also equipped with a valve, which is used to temporarily seal the surface well.

6. The method as described in claim 4, characterized in that, The gas extraction pipeline is also equipped with a manual verification port, which is used to verify the multi-parameter instrument.

7. The method as described in claim 1, characterized in that, The gas extraction pump has an extraction negative pressure of 15-30 kPa and a flow rate of 30-50 m³ / h. 3 / min.

8. The method as described in claim 1, characterized in that, When the working face to be mined is close to the surface well, the vertical distance between the cut-in and the surface well is 30-50m.

9. The method as described in claim 1, characterized in that, Monitoring will cease when the longwall face has passed the location of the surface well and the oxygen concentration remains stable for 5-10 days.

10. The method as described in claim 1, characterized in that, The oxygen concentration is greater than 18% in the heat dissipation zone, less than 10% in the asphyxiation zone, and between 10% and 18% in the oxidation zone.

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