Method for guiding and discharging gas extracted by underground pump station to ground for utilization

Abstract

The invention relates to a method for guiding and discharging gas extracted by an underground pump station to the ground for utilization, and belongs to the technical field of coal mine gas treatment. Comprising the following steps: S1, determining a gas drainage pipeline system route, a pipeline well construction position and arrangement positions among pipes of a ground fortification section; s2, the maximum gas extraction mixing amount of an underground pump station is counted and analyzed, and a pipeline system of the drainage section is designed according to the maximum gas extraction mixing amount; s3, a production mine generally does not have a channel for guiding and discharging gas from the underground to the ground through a gas guiding and discharging pipeline, a pipeline shaft needs to be constructed, and design construction of the pipeline shaft is conducted in combination with gas guiding and discharging pipeline type selection; s4, the led and discharged low-concentration gas and high-concentration gas extracted by a ground pump station are mixed and utilized, and the mixed gas is used for power generation; the problem that air flow gas overrun possibly exists when gas extracted by an underground pump station is discharged into a main air return way at present is solved.

Description

Technical Field

[0001] This invention belongs to the field of coal mine gas control technology, specifically relating to a method for extracting and discharging gas from underground pumping stations to the surface for utilization. Background Technology

[0002] my country's resource endowment of being rich in coal, poor in oil, and lacking in gas dictates that coal is the primary energy resource and the cornerstone of my country's energy structure. The formation of coal is accompanied by a large amount of gas, and gas disasters in high-gas and coal-gas outburst mines are major factors restricting safe and efficient mine production. The main methods of coal mine gas control are mine ventilation and gas extraction. For mines with large gas emissions, gas extraction is the primary method, and the first step in implementing gas extraction is to construct a gas extraction system. Currently, mine gas extraction systems mainly consist of permanent surface extraction systems (surface pumping stations) and temporary underground extraction systems (underground pumping stations). With increasing coal seam depth and mining intensity, mine gas emissions have significantly increased, or changes in mine gas control methods have led to some mines' existing surface extraction systems being unable to meet the needs of mine gas control, necessitating an upgrade of the gas extraction system capacity. Compared with surface permanent gas extraction systems, underground temporary gas extraction systems have the advantages of shorter construction period, lower investment, shorter pipeline laying lines, higher extraction efficiency, and can be put into use quickly. Therefore, they have become the primary choice for many mines to improve their gas extraction system capacity. In particular, after the elimination of gas tail roadways, in order to quickly realize the change of gas control method from tail roadway ventilation to extraction at the working face, some high-gas and outburst mines have built underground gas pumping stations.

[0003] The extraction and discharge of methane from underground gas pumping stations into the return airway not only increases the total amount of methane discharged by the ventilation system, but also poses a risk of exceeding methane limits in the return airway as the extraction volume fluctuates. Furthermore, the concentration of methane extracted from underground pumping stations drops to below 0.75% after dilution by airflow, which is even lower and not conducive to the clean utilization of methane. With the implementation of GB41022-2021 "Basic Indicators for Coal Mine Gas Extraction," the portion of methane extracted underground that is not pumped to the surface is no longer included in the mine's methane extraction volume when calculating the mine's methane extraction rate. According to GB21522-2024 "Emission Standard for Coalbed Methane (Coal Mine Gas)," low-concentration methane with a usable methane concentration higher than or equal to 8% and an extraction volume greater than or equal to 10 m³ / min should be utilized by constructing supporting methane utilization facilities; low-concentration methane with a methane concentration higher than or equal to 8% and an extraction volume greater than or equal to 10 m³ / min that is currently unusable should be destroyed. Summary of the Invention

[0004] This invention overcomes the shortcomings of existing technologies and proposes a method for diverting extracted gas from underground pumping stations to the surface for utilization; it solves the problem that the gas flow from underground pumping stations into the main return airway may exceed the limit.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution.

[0006] A method for extracting and discharging methane from an underground pumping station to the surface for utilization includes the following steps:

[0007] S1. On-site survey and drainage route design: Conduct on-site surveys of underground pump station venting and surface industrial sites. Combine the comparison diagrams above and below ground to determine the route of the gas drainage pipeline system, the construction location of pipeline wells, and the layout location of pipes in the surface defense section, so as to minimize the route of the gas drainage pipeline.

[0008] S2, statistically analyze the maximum gas extraction mixing volume of the downhole pump station, and design the pipeline system of the inlet and outlet section according to the maximum gas extraction mixing volume;

[0009] S2.1 Selection of gas drainage pipelines;

[0010] S2.2 Calculate the resistance of the gas drainage pipeline. Based on the calculation of the gas drainage pipeline resistance, and according to the positive pressure at the gas outlet of the downhole pumping station, verify whether the pressure at the gas outlet of the downhole pumping station can overcome the resistance of the gas drainage pipeline and smoothly drain the gas to the surface to achieve surface drainage or utilization.

[0011] S3. Production mines typically do not have a channel for gas to be discharged from underground to the surface via gas drainage pipelines, so pipeline wells need to be constructed. The design and construction of pipeline wells are carried out in conjunction with the selection of gas drainage pipelines.

[0012] S3.1, Select the layout of the pipeline shaft;

[0013] S3.2, Conduct safety and stability analysis on the pipeline well;

[0014] S3.3, Select the diameter and length of the manhole;

[0015] S3.4, Select the construction method for the pipeline well;

[0016] S3.5, Processing the wall of the pipeline well;

[0017] S4 involves mixing low-concentration methane gas from the drainage system with high-concentration methane gas extracted by surface pumping stations for use, particularly for concentrations below 2% to 10% and extraction volumes greater than 10 m³. 3 The methane gas produced per minute is mixed with high-concentration methane extracted from the ground pumping station. The concentration of the mixed methane gas is controlled at 12% through mixing. The mixed methane gas is then used to generate electricity. The safety facilities for the low-concentration methane gas pipeline used for power generation are equipped with three different fire-resistant and explosion-proof devices based on the principles of fire arrest, explosion suppression, and explosion prevention.

[0018] Furthermore, in step S2.1, the pipe diameter is calculated based on the maximum gas extraction volume using the following formula, and a suitable gas drainage pipeline is selected:

[0019] ;

[0020] In the formula:

[0021] d—Diameter of the gas exhaust pipeline, in meters;

[0022] Q L —The gas flow rate that needs to be extracted by the gas drainage pipeline, in m³ / min;

[0023] V—Design flow velocity of gas inside the gas inlet / outlet pipeline, in m / s.

[0024] Furthermore, in step S2.2, the frictional resistance of the gas exhaust pipeline is calculated using the following formula:

[0025]

[0026]

[0027]

[0028] In the formula:

[0029] H—resistance loss, unit: Pa;

[0030] L—Length of the gas outlet pipeline, in meters;

[0031] Q0—Mixed gas flow rate under standard conditions, in m³ / s 3 / h;

[0032] d—Inner diameter of the gas outlet pipe, in mm;

[0033] ν0—Kinematic viscosity of mixed gas under standard conditions, in m³ 2 / s;

[0034] ρ—Density of mixed gas in the gas inlet and outlet pipeline, in kg / m³ 3

[0035] Δ—Equivalent absolute roughness of the inner wall of the gas exhaust pipeline, in mm;

[0036] P0—Atmospheric pressure under standard conditions, in Pa;

[0037] P—Absolute pressure of gas in the gas exhaust pipeline, in Pa;

[0038] T—The absolute temperature of the gas in the gas exhaust pipeline at temperature t, in K;

[0039] T0—Absolute temperature under standard conditions, in K;

[0040] t—The temperature of the gas in the gas exhaust pipeline, in °C.

[0041] Furthermore, in step S2.2, the local resistance loss of the pipeline is calculated as 20% of the straight pipe resistance loss, so the total resistance loss of the downhole pump station pipeline is: H 总 =H 摩擦阻力 +H 局部总阻力 .

[0042] Furthermore, in step S3.1, the pipe well is arranged vertically.

[0043] Furthermore, in step S3.2, good geological integrity of the strata and the absence of adverse geological environments such as goafs and structural zones are prerequisites for maintaining the stability of the pipeline well.

[0044] Furthermore, in step S3.3, based on the selection of the gas drainage pipeline, and taking into account the construction space for the pipeline outer wall and the amount of drilling work, approximately 1.5 times the diameter of the gas drainage pipeline is selected as the diameter of the pipeline well, and the length of the pipeline well is the difference between the elevation of the well and the elevation of the construction site.

[0045] Furthermore, in step S3.4, based on the geological structure and rock properties, the topsoil section and weathered rock section are constructed using the impact hammer method, with protective mud added to the wellbore. The stable bedrock section employs a pilot hole positioning and two-stage reaming process. The construction is divided into two stages: pilot hole construction and two-stage reaming. First, a small-diameter pilot hole is constructed using a directional drilling rig, with simultaneous drilling and inclination measurement to correct deviations in a timely manner, achieving precise borehole guidance and positioning. After the pilot hole penetrates the strata and connects with the underground roadway, the drill bit is used to ream the hole at the bottom. The two-stage reaming is carried out using a reverse drilling rig, drilling upwards from the bottom of the hole. The primary reaming focuses on enlarging the pilot hole to allow the lowering of the secondary reaming reverse drilling rod. The secondary reaming is carried out to the diameter of the pipeline well, and the reaming cuttings are discharged from the underground roadway.

[0046] Furthermore, in S3.5.1, mechanical rock breaking and mud slurry wall protection are used in the topsoil section and weathered rock section. After entering the rock, the casing is lowered, and concrete is transported from the casing to the bottom to replace the concrete and mud, so as to achieve the purpose of high filling cementing of the entire section with concrete.

[0047] S3.5.2, the bedrock section is protected by a casing. The construction process adopts the hole-hole casing pull-out grouting method. The casing is a spiral welded steel pipe. After the pipeline is lowered in sequence, the wellhead is sealed. Then, pure cement slurry is used to fill the well with cement slurry behind the wall for cementing.

[0048] The beneficial effects of this invention compared to the prior art are as follows:

[0049] (1) While giving full play to the advantages of underground gas pumping stations such as short construction period, shorter extraction pipelines closer to extraction sites and high extraction efficiency, this paper proposes a method for underground pumping stations to extract gas and discharge it to the surface for utilization, and gives the ways of extraction and surface utilization.

[0050] (2) Pipe wells have a small footprint, flexible site selection, and short construction period. Using pipe wells as drainage channels increases the investment in pipe wells, but avoids the reduction of effective ventilation cross section, increased ventilation resistance, construction difficulties and safety issues caused by laying pipelines in return air wells.

[0051] (3) After the underground pump station extracts gas and discharges it to the surface for use, it not only reduces the gas pressure of the mine ventilation, but also includes this part of the gas in the total amount of gas extracted from the mine, which can effectively improve the gas extraction rate of the mine, and also reduce greenhouse gas emissions, realizing the clean utilization of gas, creating economic benefits while bringing greater environmental benefits. Attached Figure Description

[0052] The present invention will now be described in further detail with reference to the accompanying drawings:

[0053] Figure 1 This is a three-dimensional schematic diagram of the entire invention;

[0054] Figure 2 It is a plan view of the underground pumping station, gas drainage pipeline, and pipeline well;

[0055] Figure 3 This is a schematic diagram showing the connections between the gas drainage pipeline, the ground defense section, the ground pumping station, the mixing device, and the gas utilization system.

[0056] Figure 4 yes Figure 3 A magnified view of a portion of point A in the middle;

[0057] Among them, 1 is the underground pumping station, 2 is the gas drainage pipeline, 3 is the pipeline well, 4 is the surface defense section, 5 is the gas outlet of the underground pumping station, 6 is the return air connecting roadway, 7 is the mixing device, 8 is the gas utilization system, 9 is the water seal fire arresting and explosion venting device, 10 is the automatic powder injection explosion suppression device, 11 is the automatic explosion arresting device, 12 is the backflow prevention device, 13 is the vent pipe, and 14 is the surface pumping station. Detailed Implementation

[0058] To make the technical problems to be solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail with reference to the embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The technical solutions of this invention are described in detail below with reference to the embodiments and accompanying drawings, but the scope of protection is not limited thereto.

[0059] like Figure 1 As shown in Figure 4, the present invention provides a method for extracting and discharging methane from a downhole pumping station to the surface for utilization, comprising the following steps:

[0060] S1, on-site survey and drainage route design.

[0061] A site survey was conducted on the underground pump station 1 for venting gas and the surface industrial site. By combining the comparison diagrams of the surface and underground, the system route of the gas drainage pipeline 2, the construction location of the pipeline well 3, and the layout of the pipes in the surface defense section 4 were determined. This ensured that the route of the gas drainage pipeline 2 was the shortest, facilitating the convenient and quick transportation of the gas to the utilization end. It also facilitated the layout of the surface defense section 4 and the mixing device 7.

[0062] The route of the gas drainage pipeline system 2 is as follows: underground pump station outlet 5 → return air connecting roadway 6 → pipeline well 3 → surface defense section 4 → mixing device 7 → gas utilization system 8.

[0063] S2, statistically analyze the maximum gas extraction mixing volume of downhole pump station 1, and design the drainage section pipeline system according to the maximum gas extraction mixing volume.

[0064] S2.1, Gas drainage pipeline selection 2.

[0065] Calculate the pipe diameter based on the maximum gas extraction volume using the following formula, and select a suitable gas drainage pipeline 2:

[0066] ;

[0067] In the formula:

[0068] d—Diameter of gas outlet pipe 2, in meters;

[0069] Q L —The gas flow rate that needs to be extracted from gas drainage pipeline 2, in m³ / min;

[0070] V—Design flow velocity of gas inside the gas inlet / outlet pipeline 2, in m / s.

[0071] S2.2, Calculation of resistance in gas drainage pipeline 2.

[0072] Based on the calculation of the resistance of the gas drainage pipeline 2, and according to the positive pressure of the gas outlet 5 of the downhole pump station, it is verified whether the pressure of the gas outlet 5 of the downhole pump station can overcome the resistance of the gas drainage pipeline 2 and be successfully drained to the surface to achieve surface drainage or utilization.

[0073] The frictional resistance of gas exhaust pipeline 2 (S2.2.1) is calculated using the following formula:

[0074]

[0075]

[0076]

[0077] In the formula:

[0078] H—resistance loss, unit: Pa;

[0079] L—Length of gas outlet pipeline 2, in meters;

[0080] Q0—Mixed gas flow rate under standard conditions, in m³ / s 3 / h;

[0081] d—Inner diameter of gas outlet pipe 2, in mm;

[0082] ν0—Kinematic viscosity of mixed gas under standard conditions, in m³ 2 / s;

[0083] ρ—Density of mixed gas in gas inlet / outlet pipeline 2, in kg / m³ 3

[0084] Δ—Equivalent absolute roughness of the inner wall of gas exhaust pipe 2, in mm;

[0085] P0—Atmospheric pressure under standard conditions, in Pa;

[0086] P—Absolute pressure of gas in gas exhaust pipe 2, in Pa;

[0087] T—The gas temperature in gas exhaust pipeline 2 is the absolute temperature at time t, in K;

[0088] T0—Absolute temperature under standard conditions, in K;

[0089] t—The temperature of the gas in gas exhaust pipeline 2, in °C.

[0090] S2.2.2 The local resistance loss of the pipeline is calculated as 20% of the straight pipe resistance loss. Therefore, the total resistance loss of the pipeline in the downhole pump station 1 is: H 总 =H 摩擦阻力 +H 局部总阻力 .

[0091] S3. Production mines usually do not have a channel to discharge gas from underground to the surface through gas drainage pipeline 2. It is necessary to construct pipeline well 3. In conjunction with the selection of gas drainage pipeline 2, pipeline well 3 is designed and constructed.

[0092] S3.1, Select the layout of pipe well 3: adopt the vertical layout.

[0093] S3.2, Safety and stability analysis of pipeline well 3: Good geological integrity and absence of adverse geological environments such as goaf and structural zones are prerequisites for maintaining the stability of pipeline well 3.

[0094] S3.3, Select the diameter and length of the pipeline well 3: Based on the selection of the gas drainage pipeline 2, and taking into account the construction space of the pipeline outer wall and the amount of drilling work, the diameter of the pipeline well 3 is generally selected as about 1.5 times the diameter of the gas drainage pipeline 2. The length of the pipeline well 3 is the difference between the elevation of the well and the elevation of the construction site.

[0095] S3.4, Select the construction method for pipeline well 3: Based on the geological structure and rock properties, the topsoil and weathered rock sections will be constructed using the impact hammer method, with mud added to protect the wellbore; the stable bedrock section will use a pilot hole positioning and two-stage reaming process. The construction is divided into two stages: pilot hole construction and two-stage reaming. First, a small-diameter pilot hole will be constructed using a directional drilling rig, with simultaneous drilling and deviation measurement to correct deviations in a timely manner, achieving precise borehole guidance and positioning. After the pilot hole penetrates the strata and connects with the underground roadway, the drill bit will be used to ream the hole at the bottom. The two-stage reaming will be carried out using a raise boring machine, drilling upwards from the bottom of the hole. The first-stage reaming (sweeping) focuses on enlarging the pilot hole to allow the lowering of the second-stage reaming raise boring drill rod; the second-stage reaming will be carried out to the diameter of pipeline well 3, and the reaming drill cuttings will be discharged from the underground roadway.

[0096] S3.5, process the protective wall of the pipe well 3.

[0097] S3.5.1, mechanical rock breaking and mud wall protection are used in the topsoil section and weathered rock section. After entering the rock, the casing is lowered and concrete is transported from the casing to the bottom for concrete and mud replacement, so as to achieve the purpose of high filling cementing of the entire section with concrete.

[0098] S3.5.2, the bedrock section is protected by a casing. The construction process adopts the hole-hole casing pull-out grouting method. The casing is a spiral welded steel pipe. After the pipeline is lowered in sequence, the wellhead is sealed. Then, pure cement slurry is used to fill the well with cement slurry behind the wall for cementing.

[0099] S4, the low-concentration methane gas discharged is mixed with the high-concentration methane gas extracted by the ground pumping station 14 for utilization.

[0100] Downhole pump station 1 is primarily a low-negative-pressure extraction system, typically used for gas extraction from goaf areas in longwall mining faces using a "drainage-instead-of-drainage" approach. The extracted gas is characterized by large mixing volumes, low concentrations (generally 2%~10%), and wide fluctuations. Firstly, low-concentration gas poses serious safety hazards during transportation and utilization, necessitating the installation of safety protection sections and safety assurance facilities. Secondly, for gas with concentrations below 2%~10% and extraction volumes greater than 10 m³ / min, it is mixed with the high-concentration gas extracted from surface pump station 14. The mixed gas concentration is controlled to 12%, and the resulting gas is used for power generation. The safety assurance facilities for the low-concentration gas pipeline used for power generation should be equipped with three different principles of fire-resistant and explosion-proof devices: flame arrestor, explosion suppression, and explosion-proof. The installation sequence of these safety assurance facilities is: first-stage flame arrestor, second-stage explosion suppression device, and third-stage explosion-proof device.

[0101] In this embodiment, based on pipe diameter selection calculations and pipeline resistance calculations, a pipe diameter of 800mm is selected from the gas outlet 5 of the underground pump station to the bottom of the pipeline well 3, consistent with the pipe diameter of the gas outlet pipeline. A pipe diameter of 1000mm is selected for the pipeline well 3 and the surface protection section. The gas outlet 5 of the underground pump station is connected to the gas drainage pipeline 2 via a tee. Before the gas drainage pipeline 2 enters the bottom of the pipeline well 3, a water drainer and a slag removal filter must be installed.

[0102] The design of the ground-based gas pipeline transportation safety assurance system for section 4 includes a pipe chamber measuring 25m in length, 4m in width, and 4.5m in height. After the gas exhaust pipeline 2 exits from the pipeline well 3, a water seal fire arrestor and explosion relief device 9, an automatic powder spraying explosion suppression device 10, and an automatic explosion arrestor device 11 are installed.

[0103] ① Install a set of two powder spraying tanks of automatic powder spraying explosion suppression device 10 at a position 6m before the bend into the pipe room, so as to ensure that the distance between the automatic powder spraying tank and the flame sensor on the vent pipe is 30m-60m.

[0104] ② To prevent gas backflow and pipeline explosion transmission that may occur when the gas extraction pump stops operating, a backflow prevention device 12 and an automatic explosion arrestor 11 are installed in the ground defense section 4.

[0105] ③ Install a detonating cord on the water seal fire arrestor and explosion relief device 9. The height of the detonating cord opening must be at least 1m above the roof of the pipe room.

[0106] ④ Install a gas vent pipe 13 on the pipeline after the water seal fire arrestor and explosion relief device 9. The height of the vent pipe 13 opening must be at least 3m above the roof of the pipe room, and a flame sensor must be installed within 5m of the pipe opening. A pressure sensor must be installed within 2m of the center of the horizontal conveying pipe.

[0107] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for extracting and discharging methane gas from an underground pumping station to the surface for utilization, characterized in that, Includes the following steps: S1. On-site survey and drainage route design: Conduct on-site surveys of underground pump station venting and surface industrial sites. Combine the comparison diagrams above and below ground to determine the route of the gas drainage pipeline system, the construction location of pipeline wells, and the layout location of pipes in the surface defense section, so as to minimize the route of the gas drainage pipeline. S2, statistically analyze the maximum gas extraction mixing volume of the downhole pump station, and design the pipeline system of the inlet and outlet section according to the maximum gas extraction mixing volume; S2.1 Selection of gas drainage pipeline; S2.2 Calculate the resistance of the gas drainage pipeline. Based on the calculation of the gas drainage pipeline resistance, and according to the positive pressure at the gas outlet of the downhole pumping station, verify whether the pressure at the gas outlet of the downhole pumping station can overcome the resistance of the gas drainage pipeline and smoothly drain the gas to the surface to achieve surface drainage or utilization. S3. Production mines typically do not have a channel for gas to be discharged from underground to the surface via gas drainage pipelines, so pipeline wells need to be constructed. The design and construction of pipeline wells are carried out in conjunction with the selection of gas drainage pipelines. S3.1, Select the layout of the pipeline shaft; S3.2, Conduct safety and stability analysis on the pipeline well; S3.3, Select the diameter and length of the manhole; S3.4, Select the construction method for the pipeline well; S3.5, Processing the wall of the pipeline well; S4 involves mixing low-concentration methane gas from the drainage system with high-concentration methane gas extracted by surface pumping stations for use, particularly for concentrations below 2% to 10% and extraction volumes greater than 10 m³. 3 The methane gas produced per minute is mixed with high-concentration methane extracted from the ground pumping station. The concentration of the mixed methane gas is controlled at 12% through mixing. The mixed methane gas is then used to generate electricity. The safety facilities for the low-concentration methane gas pipeline used for power generation are equipped with three different fire-resistant and explosion-proof devices based on the principles of fire arrest, explosion suppression, and explosion prevention.

2. The method for extracting and discharging methane from an underground pumping station to the surface for utilization according to claim 1, characterized in that: In step S2.1, the pipe diameter is calculated according to the maximum gas extraction mixing capacity using the following formula, and a gas inlet / outlet pipeline of appropriate diameter is selected: ； In the formula: d—Diameter of the gas exhaust pipeline, in meters; Q L —The gas flow rate that needs to be extracted by the gas drainage pipeline, in m³ / min; V—Design flow velocity of gas inside the gas inlet / outlet pipeline, in m / s.

3. The method for extracting and discharging methane from an underground pumping station to the surface for utilization according to claim 1, characterized in that: In step S2.2, the frictional resistance of the gas exhaust pipeline is calculated using the following formula: ； ； ； In the formula: H—resistance loss, unit: Pa; L—Length of the gas outlet pipeline, in meters; Q0—Mixed gas flow rate under standard conditions, in m³ / s 3 / h; d—Inner diameter of the gas outlet pipe, in mm; ν0—Kinematic viscosity of mixed gas under standard conditions, in m³ 2 / s; ρ—Density of mixed gas in the gas inlet and outlet pipeline, in kg / m³ 3 Δ—Equivalent absolute roughness of the inner wall of the gas exhaust pipeline, in mm; P0—Atmospheric pressure under standard conditions, in Pa; P—Absolute pressure of gas in the gas exhaust pipeline, in Pa; T—The absolute temperature of the gas in the gas exhaust pipeline at temperature t, in K; T0—Absolute temperature under standard conditions, in K; t—The temperature of the gas in the gas exhaust pipeline, in °C.

4. The method for extracting and discharging methane from an underground pumping station to the surface for utilization according to claim 1, characterized in that: In step S2.2, the local resistance loss of the pipeline is calculated as 20% of the straight pipe resistance loss. Therefore, the total resistance loss of the downhole pump station pipeline is: H 总 =H 摩擦阻力 +H 局部总阻力 .

5. The method for extracting and discharging methane from an underground pumping station to the surface for utilization according to claim 1, characterized in that: In step S3.1, the pipeline well is arranged vertically.

6. The method for extracting and discharging methane from an underground pumping station to the surface for utilization according to claim 1, characterized in that: In step S3.2, good geological integrity of the strata and rock mass, and the absence of adverse geological environments such as goaf and structural zones, are prerequisites for maintaining the stability of the pipeline well.

7. The method for extracting and discharging methane from an underground pumping station to the surface for utilization according to claim 1, characterized in that: In step S3.3, based on the selection of the gas drainage pipeline, and taking into account the construction space of the pipeline outer wall and the amount of drilling work, approximately 1.5 times the diameter of the gas drainage pipeline is selected as the diameter of the pipeline well, and the length of the pipeline well is the difference between the elevation of the well and the elevation of the construction site.

8. A method for extracting and discharging methane from an underground pumping station to the surface for utilization according to claim 1, characterized in that: In step S3.4, based on the geological structure and rock properties, the topsoil and weathered rock sections are constructed using the impact hammer method, with protective mud added to the wellbore. The stable bedrock section employs a pilot hole positioning and two-stage reaming process. The construction is divided into two stages: pilot hole construction and two-stage reaming. First, a small-diameter pilot hole is constructed using a directional drilling rig, with drilling and inclination measurement performed simultaneously to correct deviations in a timely manner, achieving precise borehole guidance and positioning. After the pilot hole penetrates the strata and connects with the underground roadway, the bottom of the hole is enlarged by the drill bit. The two-stage reaming is carried out using a reverse drilling rig, drilling upwards from the bottom of the hole. The primary reaming focuses on enlarging the pilot hole to allow the lowering of the secondary reaming reverse drilling rod. The secondary reaming is carried out to the diameter of the pipeline well, and the reaming cuttings are discharged from the underground roadway.

9. A method for extracting and discharging methane from an underground pumping station to the surface for utilization according to claim 1, characterized in that: S3.5.1, mechanical rock breaking and mud wall protection are used in the topsoil section and weathered rock section. After entering the rock, the casing is lowered and concrete is transported from the casing to the bottom to replace the concrete and mud, so as to achieve the purpose of high filling cementing of the entire section with concrete. S3.5.2, the bedrock section is protected by a casing. The construction process adopts the hole-hole casing pull-out grouting method. The casing is a spiral welded steel pipe. After the pipeline is lowered in sequence, the wellhead is sealed. Then, pure cement slurry is used to fill the well with cement slurry behind the wall for cementing.

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