Method for preventing harmful gas in upper goaf from leaking in close-range coal seam downward mining

Abstract

The application discloses a method for preventing harmful gas in an upper goaf from leaking downward in close-range coal seam downward mining, which comprises the following steps: step one: with the mining of an upper coal seam working face, a partition wall is constructed, and an air extraction pipeline is laid; the partition wall divides the space of the upper coal seam goaf into multiple sections, and an air extraction pipeline is separately laid in each section return air roadway; step two: an inert gas injection pipeline is laid; before the mining of a lower coal seam working face, an inert gas injection pipeline is laid in an air inlet roadway of the lower coal seam working face; step three: air extraction prevention and treatment; in the air extraction unit corresponding to the mining stage of the lower coal seam working face, air is extracted through the air extraction pipeline of the air extraction unit, inert gas is injected through the inert gas injection system, and the air extraction pipeline of the corresponding section is switched according to the construction progress until the mining is completed. The method can prevent the harmful gas in the upper goaf from leaking downward, and at the same time, the inert gas in the lower layer moves upward to form a large-area composite inertization goaf, which is beneficial to the prevention and treatment of residual coal spontaneous combustion in the composite goaf formed by the close-range coal seams.

Description

Technical Field

[0001] The present invention relates to the technical field of coal seam mining, and in particular to a method for preventing harmful gas from leaking from an upper goaf during downward mining of a close-range coal seam. Background Art

[0002] Due to the high proportion of closely spaced coal seams in my country and the predominant practice of downward mining, roof collapse during coal seam mining creates numerous interlayer fissures, interconnecting new and old goafs in closely spaced coal seams, forming large-scale composite goafs. Composite goafs formed by closely spaced coal seam mining have a wide distribution of residual coal, with a large amount of residual coal exhibiting a three-dimensional spatial distribution. Furthermore, composite goafs experience high air leakage, and the patterns of this leakage are difficult to determine, making spontaneous combustion of coal in composite goafs particularly frequent. The oxidation and spontaneous combustion of residual coal is accompanied by the production of large quantities of toxic and harmful gases. Furthermore, during the mining of the lower strata, roof collapse can easily lead to the connection of the overlying goaf, allowing toxic and harmful gases accumulated within the upper goaf to escape downward.

[0003] Affected by the negative pressure ventilation of the mine, the toxic and harmful gases produced during the oxidation and spontaneous combustion of the residual coal and accumulated in the upper goaf escaped with the wind flow to the lower coal seam working face and accumulated in large quantities in the return air corner, posing a serious threat to the life safety of underground workers. In addition, a large amount of gas produced by coal oxidation poured into the return mining working face, seriously interfering with the accuracy of the application of coal spontaneous combustion warning indicator gas and affecting the normal production of the lower coal seam working face.

[0004] At present, the solution to this problem is mainly to reduce air leakage from the goaf to the working face through pressure-equalizing fire prevention and extinguishing measures. However, pressure-equalizing fire prevention and extinguishing has high requirements for underground safety management, and the air adjustment measures are complicated. If management errors occur, it is very easy to cause toxic and harmful gases to exceed the limit on the working face, threatening the lives of underground workers, and may cause secondary disasters and cause serious economic losses. Summary of the Invention

[0005] The present invention aims to solve the technical problems existing in the prior art. In particular, it innovatively proposes a method for preventing the leakage of harmful gases in the upper coal seam goaf during the downward mining of close-range coal seams. The method can prevent the harmful gases accumulated in the goaf of the upper coal seam from leaking to the working face of the lower coal seam during the downward mining of close-range coal seams. At the same time, a large-area composite inerting area is formed behind the goaf to ensure safe production of the working face of the lower coal seam.

[0006] In order to achieve the above-mentioned object of the present invention, the present invention provides a method for preventing harmful gas from leaking from the upper goaf during downward mining of a close-range coal seam, comprising the following steps:

[0007] Step 1: As the upper coal seam working face is mined, an isolation wall is constructed and an exhaust pipeline is laid; the grouting pipe of the grouting equipment is extended from the gap between the supports into the goaf or sealing materials are poured through high-position drilling holes to form an isolation wall, and the space in the goaf of the upper coal seam is divided into multiple sections along its mining direction, each section is isolated into a relatively independent exhaust unit, and an exhaust pipeline leading to the external extraction system is laid separately in the return air lane of each section. All exhaust pipelines are sheathed with protective steel pipes, and the parts of the exhaust pipelines located in the corresponding exhaust units are provided with multiple filtered exhaust ends;

[0008] Step 2: Laying an inert gas injection pipeline; before mining the lower coal seam working face, laying an inert gas injection pipeline in the air intake tunnel of the lower coal seam working face, wherein the inert gas injection pipeline is connected to an inert gas injection system for injecting inert gas, and the inert gas injection pipeline is used to inject inert gas;

[0009] Step three: gas extraction for prevention and control; in the gas extraction unit where the upper coal seam goaf corresponding to the lower coal seam working face mining stage is located, gas is extracted through the gas extraction pipeline of the gas extraction unit to form a negative pressure space in the gas extraction unit, and at the same time, inert gas is injected into the lower coal seam goaf through the inert injection system to form an airflow flowing from the lower coal seam goaf to the upper coal seam goaf, and the harmful gases in the upper and lower coal seam goafs are extracted from the gas extraction unit of the upper coal seam goaf; and the gas extraction pipeline of the corresponding section is switched according to the mining construction progress of the lower coal seam working face until the mining of the lower coal seam working face is completed.

[0010] In the above scheme: the filtering and exhausting end head described in step 1 includes a flower tube, a dust filter is fixed in the flower tube, and the dust filter is connected to the exhaust pipeline.

[0011] In the above scheme: the protective steel pipe described in step one is provided with a protective tee at the filter exhaust end corresponding to the exhaust pipeline, and the three ends of the protective tee are respectively used to connect the adjacent steel pipe body and the flower pipe.

[0012] In the above scheme: the exhaust pipeline described in step 1 is laid at least 1.5m above the ground.

[0013] In the above scheme: the exhaust pipeline includes a main pipe located in the protective steel pipe and a branch pipe used to connect to the filter exhaust end. When connecting the filter exhaust end, the branch pipe is pulled out 15-20cm from the protective tee and connected to the dust filter, and then the flower pipe is connected to the port of the protective tee through the flange.

[0014] In the above scheme: the injection inert pipeline described in step 3 is hung on the coal wall of the chute, and the hanging height of the injection inert pipeline is higher than 1.5m.

[0015] In the above scheme: the extension depth of the section described in step 1 is 50-200m.

[0016] In the above solution: the filling material of the grouting equipment is LMF lightweight filling material.

[0017] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0018] 1. Lay an exhaust pipeline in the goaf of the upper coal seam. When the lower coal seam working face is mined, the harmful gas in the goaf of the upper coal seam is extracted, forming a negative pressure space in the goaf of the upper coal seam. Combined with the positive pressure space formed by injecting inert gas into the goaf of the lower coal seam, the harmful gas in the goaf of the upper coal seam is prevented from leaking down along the interlayer cracks into the working face of the lower coal seam, thereby avoiding the threat to the life safety of underground workers caused by the leakage of toxic and harmful gases. At the same time, the harmful gas is extracted from the exhaust pipeline in the goaf of the upper coal seam, reducing the content of harmful gas in the goaf of the upper coal seam.

[0019] 2. By pouring sealing materials, an isolation wall is constructed inside the goaf of the upper coal seam to form multiple relatively independent gas extraction units. Pumping gas from the independent units is beneficial to improving the gas extraction effect and making it easier to control the gas migration in the goaf of the upper and lower coal seams;

[0020] 3. When the lower coal seam working face is mined back to the corresponding extraction unit in the goaf of the upper coal seam, the corresponding extraction pipeline is opened to extract only the harmful gas in the extraction unit corresponding to the lower coal seam working face. This is more targeted in preventing and controlling the leakage of harmful gases. It is not necessary to extract all the harmful gases in the goaf of the upper coal seam, thus reducing the working pressure of the extraction pump and effectively controlling gas migration.

[0021] 4. During normal mining at the lower coal seam working face, nitrogen is continuously injected into the goaf of the lower coal seam working face through the inerting pipeline. This can not only inertify the residual coal in the goaf of the lower coal seam and prevent spontaneous combustion of the residual coal in the goaf of the lower coal seam, but also form a positive pressure space to prevent the leakage of harmful gases in the goaf of the upper coal seam. At the same time, the inert gas in the lower coal seam working face moves upward to form a large-area composite inerting goaf, which is beneficial to the prevention and control of spontaneous combustion of residual coal in the composite goaf formed in close proximity to the coal seam, and ensure normal production of the mine. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Exhaust pipe laying diagram.

[0023] Figure 2 Schematic diagram of the exhaust pipeline protection tee.

[0024] Figure 3 Diagram of nitrogen injection pipeline laying.

[0025] Figure 4 Schematic diagram of the inter-frame spacing grouting method.

[0026] Figure 5 Schematic diagram of gas flow between close-range coal seams before gas leakage prevention measures are implemented.

[0027] Figure 6 Schematic diagram of gas flow between close-range coal seams after implementation of anti-gas leakage measures. DETAILED DESCRIPTION

[0028] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0029] like Figures 1 to 6 As shown, a method for preventing harmful gas from leaking from the upper goaf during downward mining of a close-range coal seam comprises the following steps:

[0030] Step 1: As the upper coal seam working face is mined, an isolation wall is constructed and an exhaust pipe 1 is laid. The grouting pipe of the grouting equipment 7 is extended from the gap between the supports into the goaf, or a sealing material is injected through a high-level drill hole to form an isolation wall. The space within the goaf of the upper coal seam is divided into multiple sections extending from 50 to 200 meters in depth along the mining direction. Each section is isolated into a relatively independent exhaust unit. The filling material of the grouting equipment 7 is LMF lightweight filling material, which is non-toxic, odorless, non-polluting, non-corrosive, and has no impact on the working environment.

[0031] A separate exhaust pipeline 1 leading to the external extraction system is laid in the return airway of each section. The exhaust pipeline 1 is laid 1.5 meters above the ground in the upper coal seam goaf to prevent water accumulation from affecting the extraction as the working face advances. All exhaust pipelines 1 are sheathed with protective steel pipes 2, and the portion of the exhaust pipeline 1 located within the corresponding extraction unit is equipped with multiple filtered exhaust terminals.

[0032] The filter exhaust end includes a floral tube 5, in which a dust filter 6 is fixed. The dust filter 6 is connected to the exhaust pipe 1. The protective steel pipe 2 is provided with a protective tee 3 corresponding to the filter exhaust end of the exhaust pipe 1. The three ends of the protective tee 3 are used to connect to the adjacent steel pipe body and the floral tube 5 respectively.

[0033] The exhaust pipeline 1 includes a main pipe located in the protective steel pipe 2 and a branch pipe used to connect to the filter exhaust end. When connecting the filter exhaust end, the branch pipe is pulled out 15-20 cm from the protective tee 3, and the branch pipe is fixed with an anchor agent and connected to the dust filter 6. Then, the flower pipe 5 is connected to the port of the protective tee 3 using a flange 4 to prevent dislocation during construction.

[0034] Step 2: Lay the inert gas injection pipeline 8; Before the lower coal seam working face is mined, lay the inert gas injection pipeline 8 in the air intake tunnel of the lower coal seam working face. The inert gas injection pipeline 8 is connected to the inert gas injection system for injecting inert gas. The inert gas injection pipeline 8 is suspended on the coal wall of the chute, and the suspension height of the inert gas injection pipeline 8 is higher than 1.5m. The nitrogen injection pipeline is made of a seamless steel pipe with a diameter of 80mm. Among them, the inert gas injection pipeline 8 is buried using the step-by-step burial method. When the gas outlet end of the inert gas injection pipeline 8 is buried 10-15m inside the goaf, nitrogen injection begins, and when it is buried 30-50m inside the goaf, it stops. Replace the step-by-step pipe to continue nitrogen injection into the goaf of the lower coal seam working face. Maintain nitrogen injection during the advancement of the lower coal seam working face to form a positive pressure space in the goaf of the lower coal seam working face to prevent harmful gases from leaking from the goaf of the upper coal seam into the lower coal seam working face.

[0035] Step 3: gas extraction prevention and control; use the gas extraction unit in the upper coal seam goaf corresponding to the lower coal seam working face mining stage, and extract gas through the gas extraction pipeline (1) of the gas extraction unit, so that a negative pressure space is formed in the section, and at the same time, inert gas is injected into the lower coal seam working face through the inert injection system to form an air flow from the lower coal seam goaf to the upper coal seam goaf, and the harmful gases in the upper and lower coal seam goafs are extracted from the gas extraction unit in the upper coal seam goaf and passed to the extraction system; and switch the gas extraction pipeline (1) of the corresponding section according to the mining construction progress of the lower coal seam working face until the mining of the lower coal seam working face is completed.

[0036] For example, when the mining range of the lower coal seam working face corresponds to the first section at the far left of the upper coal seam goaf, the exhaust pipe 1 of this section is opened to extract gas, and the harmful gas is extracted and discharged, while forming a negative pressure space to prevent the leakage of harmful gas; at the same time, the lower coal seam working face maintains nitrogen injection, so that the goaf of the lower coal seam working face forms a positive pressure space, preventing the toxic and harmful gas from the upper coal seam goaf from leaking down. When the lower coal seam working face is mined to the second section near the upper coal seam goaf, the exhaust pipe 1 of the second section of the upper coal seam goaf is opened to extract gas, and then the above steps are repeated until the mining of the lower coal seam working face is completed.

Claims

1. A method for preventing harmful gas from leaking from the upper goaf during down-mining mining of a close-range coal seam, characterized in that: The following steps are involved: Step 1: As the upper coal seam working face is mined, an isolation wall is constructed and an exhaust pipe (1) is laid; the grouting pipe of the grouting equipment (7) is extended from the gap between the supports into the goaf or a sealing material is poured through a high-position drill hole to form an isolation wall, and the space in the goaf of the upper coal seam is divided into multiple sections along its mining direction, each section is isolated into a relatively independent exhaust unit, and an exhaust pipe (1) leading to an external extraction system is laid separately in the return air lane of each section, all the exhaust pipes (1) are sheathed with a protective steel pipe (2), and the part of the exhaust pipe (1) located in the corresponding exhaust unit is provided with multiple filter exhaust terminals; The filtering exhaust terminal described in step 1 includes a flower tube (5), a dust filter (6) is fixed in the flower tube (5), and the dust filter (6) is connected to the exhaust pipe (1). The filtering exhaust terminal corresponding to the exhaust pipe (1) on the protective steel pipe (2) described in step 1 is provided with a protective tee (3), and the three ends of the protective tee (3) are respectively used to connect the adjacent steel pipe bodies and the flower tube (5). The exhaust pipe (1) includes a main pipe located in the protective steel pipe (2) and a branch pipe for connecting to the filtering exhaust terminal. When connecting the filtering exhaust terminal, the branch pipe is pulled out from the protective tee (3) by 15-20 cm, connected to the dust filter (6), and fixed with an anchoring agent. Then, the flower tube (5) is connected to the port of the protective tee (3) through the flange (4); Step 2: laying an inert gas injection pipeline (8); before the lower coal seam working face is mined, an inert gas injection pipeline (8) is laid in the air inlet tunnel of the lower coal seam working face, the inert gas injection pipeline (8) is connected to an inert gas injection system for injecting inert gas, and the inert gas injection pipeline (8) is used to inject inert gas; and the inert gas injection pipeline (8) is buried by a step-by-step burial method, and when the gas outlet end of the inert gas injection pipeline (8) is buried at a position of 10-15m inside the goaf, nitrogen injection begins, and when it is buried at a position of 30-50m inside the goaf, nitrogen injection is stopped, and the step-by-step pipe is replaced to continue nitrogen injection into the goaf of the lower coal seam working face; Step 3: Gas extraction prevention and control; in the gas extraction unit where the upper coal seam goaf corresponding to the lower coal seam working face mining stage is located, gas is extracted through the gas extraction pipeline (1) of the gas extraction unit, so that a negative pressure space is formed in the gas extraction unit, and at the same time, inert gas is injected into the lower coal seam goaf through the inert injection system to form an air flow from the lower coal seam goaf to the upper coal seam goaf, and harmful gases in the upper and lower coal seam goafs are extracted from the gas extraction unit of the upper coal seam goaf; and the gas extraction pipeline (1) of the corresponding section is switched according to the mining construction progress of the lower coal seam working face until the mining of the lower coal seam working face is completed.

2. The method for preventing harmful gas from leaking from the upper goaf during close-range coal seam downward mining according to claim 1, characterized in that: The exhaust pipe (1) described in step 1 is laid at least 1.5 m above the ground.

3. The method for preventing harmful gas from leaking from the upper goaf during close-range coal seam downward mining according to claim 1, characterized in that: The inert injection pipeline (8) described in step 2 is suspended on the coal wall of the chute, and the suspension height of the inert injection pipeline (8) is higher than 1.5m.

4. The method for preventing harmful gas from leaking from the upper goaf during downward mining of a close-range coal seam according to claim 1, characterized in that: The section described in step 1 extends to a depth of 50-200 m.

5. The method for preventing harmful gas from leaking from the upper goaf during close-range coal seam downward mining according to claim 1, characterized in that: The filling material of the grouting equipment (7) is LMF lightweight filling material.

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