Nitrogen long-distance conveying supercharging device and method for coal mine

Abstract

The invention discloses a long-distance nitrogen conveying and pressurizing device for a coal mine, which comprises a main pipeline, a normal-pressure conveying pipeline, a pressurizing pipeline, a branch pipeline, a first electric valve, a pressurizing main engine, a second electric valve, a first one-way valve and a third electric valve, one end of the main pipeline is connected with a ground nitrogen generation station, and the other end of the main pipeline is connected with the normal-pressure conveying pipeline and the pressurizing pipeline; one end of the normal-pressure conveying pipeline is located in a nitrogen injection area, the other end of the pressurizing pipeline is located in a high-pressure nitrogen using area, and the two ends of the branch pipeline are connected to the normal-pressure conveying pipeline and the pressurizing pipeline correspondingly. The problem of pressure loss caused by the fact that gas in an existing conveying pipeline is conveyed through a long-distance pipeline is solved, a double-pressure switching system is arranged in the pressurizing main machine, and input nitrogen can be converted according to supply requirements so as to meet the pressure requirements of different working conditions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of supercharging, and particularly provides a nitrogen gas long-distance conveying supercharging device and method for coal mines. BACKGROUND

[0002] Inert gas fire prevention and extinguishing technology is one of the main fire prevention and extinguishing measures for goaf in coal mines stipulated in the Ventilation Fire Prevention and Extinguishing Rules. Most domestic large and medium-sized coal mine production enterprises start to choose ground nitrogen production stations that do not require explosion-proof design, have sufficient gas source, large nitrogen production capacity, and are more convenient to operate and maintain, to ensure the normal and safe production of coal mines. After completing nitrogen production on the ground, the nitrogen gas is conveyed to the underground through special nitrogen conveying pipelines to provide pressurized nitrogen gas for coal mine underground fire prevention and extinguishing or other nitrogen gas needs.

[0003] Among them, in order to ensure that the nitrogen injection area for coal mine underground fire prevention and extinguishing has sufficient flow and pressure of nitrogen gas supply, so as to meet the requirement in the Coal Mine Nitrogen Fire Prevention and Extinguishing Technology Specification that the absolute pressure of input nitrogen gas should not be less than 0.2 MPa, it is usually necessary to convey nitrogen gas with a pressure of 0.3 MPa to 1.6 MPa to the nitrogen injection area, and a nitrogen source with sufficient pressure and flow is also required for other high-pressure nitrogen areas in coal mines, for example, when auxiliary drilling and deslagging construction is carried out in coal mines, it is necessary to meet the demand that the gas supply pressure should be greater than or equal to 2.0 MPa, to ensure sufficient nitrogen pressure to drive drilling and coal ash discharge.

[0004] With the increase of mining depth and range, the length requirement of nitrogen gas produced by ground nitrogen production stations for conveying through nitrogen pipelines also increases. The outlet pressure of nitrogen gas produced by ground nitrogen production stations is generally 0.8 MPa to 1.0 MPa. In the process of long-distance pipeline gas conveying, due to reasons such as diameter change of conveying pipeline, valve or inner wall friction, pipeline bending, etc., the along-path resistance and local resistance are generated, which leads to gas pressure loss of conveying pipeline, reduction of conveying flow, and reduction of pressure loss to 0.2 MPa or less, finally resulting in that the pressure energy of nitrogen gas output by ground nitrogen production stations cannot effectively cover a larger range.

[0005] At present, the ground natural gas pipeline transportation adopts gas turbine to cooperate with centrifugal compressor to pressurize, so that the natural gas can be transported farther, but this kind of pressurizing mode cannot be used in the underground coal mine because the gas turbine does not meet the explosion-proof requirements of the coal mine, the centrifugal compressor is too large to be used in the narrow space of the underground coal mine, and thus it is difficult to be used in the underground coal mine, and the existing nitrogen supply to the nitrogen injection area uses a low-pressure nitrogen making machine to produce nitrogen, and other high-pressure nitrogen generally uses a high-pressure nitrogen making machine, the nitrogen produced by the two machines has different parameters such as pressure and flow, and cannot be used interchangeably, and it is difficult to select different pressure values of nitrogen to be supplied to the nitrogen injection area or the high-pressure nitrogen area in the narrow space according to the requirements; in addition, if a variable frequency motor and a frequency converter are selected to realize the output of different rotating speeds, the adjustment of the output pressure in a small range can be realized, but the two kinds of working conditions cannot be met, and the variable frequency motor and the frequency converter are high in cost and large in size, and are not dominant in the narrow space of the underground coal mine, and thus the existing equipment cannot select different pressure values of nitrogen to be supplied to the nitrogen injection area or the high-pressure nitrogen area in the narrow space according to the requirements. SUMMARY

[0006] To solve the above problems, the present application provides a nitrogen long-distance transportation pressurizing device for coal mine and a method, to solve the problem that the gas pipeline in the underground coal mine is difficult to supply different pressure values of nitrogen to the nitrogen injection area or the high-pressure nitrogen area in the narrow space according to the requirements.

[0007] To achieve the above purpose, the technical scheme adopted by the present application is as follows: a nitrogen long-distance transportation pressurizing device for coal mine, connected with a ground nitrogen making station, comprising a main pipeline, a normal pressure transportation pipeline, a pressurizing pipeline, a branch pipeline, a first electric valve, a pressurizing main machine, a second electric valve, a first one-way valve and a third electric valve, one end of the main pipeline is connected with the ground nitrogen making station, and the other end of the main pipeline is connected with the normal pressure transportation pipeline and the pressurizing pipeline, the other end of the normal pressure transportation pipeline is located in the nitrogen injection area, the other end of the pressurizing pipeline is located in the high-pressure nitrogen area, and the two ends of the branch pipeline are connected with the normal pressure transportation pipeline and the pressurizing pipeline respectively; the first electric valve, the pressurizing main machine, the first one-way valve and the third electric valve are sequentially assembled on the pressurizing pipeline, the second electric valve is assembled on the branch pipeline, one end of the branch pipeline is located at the input end of the first one-way valve, and the other end of the branch pipeline is located at the input end of the nitrogen injection area; the pressurizing main machine comprises an air compressor and a double pressure switching system, the double pressure switching system is used to convert the nitrogen input into the air compressor into the pressure value required by the nitrogen injection area or the pressure value required by the high-pressure nitrogen area and output to the nitrogen injection area or the high-pressure nitrogen area.

[0008] Further, the air compressor is provided with an air inlet butterfly valve and an oil-gas bucket, and the double pressure switching system is arranged between the air inlet butterfly valve and the oil-gas bucket.

[0009] Further, the double pressure switching system comprises a high pressure proportional valve, a low pressure proportional valve, a loading electromagnetic valve and a high-low pressure conversion valve, the high pressure proportional valve, the low pressure proportional valve and the loading electromagnetic valve are connected in parallel and two ends thereof are connected with the inlet butterfly valve and the oil-gas cylinder respectively, and the high-low pressure conversion valve is connected in series with the low pressure proportional valve.

[0010] Further, the gas buffer assembly comprises a low pressure gas buffer tank and a high pressure gas buffer tank, the low pressure gas buffer tank and the high pressure gas buffer tank are arranged on the pressurizing pipeline, and the low pressure gas buffer tank and the high pressure gas buffer tank are located at two ends of the pressurizing host respectively.

[0011] Further, the pressurizing pipeline is further provided with a flow limiting valve and a vortex flow meter, and the flow limiting valve and the vortex flow meter are arranged between the first electric valve and the low pressure gas buffer tank, and an output end of the flow limiting valve is connected with an input end of the vortex flow meter.

[0012] Further, an overflow pipeline is connected between an output end of the first electric valve and the nitrogen injection area, and a reverse flow valve is connected on the overflow pipeline.

[0013] Further, the branch pipeline is further provided with a discharge valve, and an input end of the discharge valve is connected with an output end of the second electric valve.

[0014] Further, the normal pressure conveying pipeline is provided with a fourth electric valve and a second check valve, and an output end of the fourth electric valve is connected with an input end of the second check valve.

[0015] A coal mine nitrogen long distance conveying pressurization method, which adopts the coal mine nitrogen long distance conveying pressurization device, and specifically comprises the following steps: When it is required to provide the nitrogen injection area with nitrogen gas with a pressure value of 0.3 MPa to 1.6 MPa, the first electric valve, the pressurizing host and the second electric valve are opened, the third electric valve is closed, the double pressure switching system is started to convert the nitrogen gas input into the pressurizing host into nitrogen gas with a pressure value of 0.3 MPa to 1.6 MPa, and then the nitrogen gas is conveyed into the nitrogen injection area; When it is required to provide the high pressure nitrogen area with nitrogen gas with a pressure value greater than or equal to 2.0 MPa, the first electric valve, the pressurizing host and the third electric valve are opened, the second electric valve is closed, the double pressure switching system is started to convert the nitrogen gas input into the pressurizing host into nitrogen gas with a pressure value greater than or equal to 2.0 MPa, and then the nitrogen gas is conveyed into the high pressure nitrogen area.

[0016] The beneficial effects of using the present application are: 1. The nitrogen gas pipeline in the coal mine goaf is provided with a booster host, which can pressurize the nitrogen gas transported from the ground nitrogen station, avoiding the problem of pressure loss of the gas in the pipeline transported through the long distance pipeline.

[0017] 2. The booster host uses an air compressor to pressurize alone, compared with the pressurizing mode through a gas turbine and a centrifugal compressor, can be used in a narrow area, and meets the coal mine explosion-proof requirement.

[0018] 3. The booster host is internally provided with a double-pressure switching system, which can convert the input nitrogen gas according to the supply demand to meet the pressure demand of different working conditions, ensure the sufficient flow and pressure of the nitrogen gas supply in the coal mine underground fire extinguishing and nitrogen injection area, meet the requirements of the input nitrogen gas in the coal mine nitrogen fire extinguishing technical specification, and can provide a gas source with sufficient pressure and flow for other high-pressure nitrogen areas. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a structural schematic view of the present application.

[0020] Figure 2 is a structural schematic view of the booster host of the present application.

[0021] The reference signs include: 1. first electric valve, 2. booster host, 211. inlet butterfly valve, 212. oil and gas barrel, 221. high-pressure proportional valve, 222. low-pressure proportional valve, 223. loading electromagnetic valve, 224. high-low pressure conversion valve, 3. second electric valve, 31. pressure relief valve, 4. first check valve, 5. third electric valve, 61. low-pressure gas buffer tank, 62. high-pressure gas buffer tank, 71. flow limiting valve, 72. vortex flowmeter, 81. fourth electric valve, 82. second check valve, 9. backflow valve. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0023] Embodiment one

[0024] Reference Figure 1 and Figure 2The utility model relates to a kind of nitrogen long-distance conveying pressurizing device for coal mine, connect with ground nitrogen station, including main pipeline, normal-pressure conveying pipeline, pressurizing pipeline, branch pipeline, first electric valve 1, pressurizing host 2, second electric valve 3, first check valve 4 and third electric valve 5, one end of main pipeline connects ground nitrogen station, and another end of main pipeline connects normal-pressure conveying pipeline and pressurizing pipeline, another end of normal-pressure conveying pipeline is located in nitrogen injection area, another end of pressurizing pipeline is located in high-pressure nitrogen area, branch pipeline two ends are connected to normal-pressure conveying pipeline and pressurizing pipeline respectively.

[0025] First electric valve 1, pressurizing host 2, first check valve 4 and third electric valve 5 are sequentially assembled on pressurizing pipeline, second electric valve 3 is assembled on branch pipeline, one end of branch pipeline is located in the input end of first check valve 4, and another end of branch pipeline is located in the input end of nitrogen injection area.

[0026] Pressurizing host 2 includes air compressor and double-pressure switching system, and the double-pressure switching system is used to convert nitrogen input into air compressor into the pressure value required by nitrogen injection area or the pressure value required by high-pressure nitrogen area and output to nitrogen injection area or high-pressure nitrogen area.

[0027] Specifically, air inlet butterfly valve 211 and oil-gas bucket 212 are arranged in air compressor, and double-pressure switching system is arranged between air inlet butterfly valve 211 and oil-gas bucket 212.

[0028] Air compressor adopts existing bipolar compression screw air compressor, and the pressure system arranged between air inlet butterfly valve 211 and oil-gas bucket 212 in air compressor is improved to be double-pressure switching system.

[0029] Specifically, the double-pressure switching system includes high-pressure proportional valve 221, low-pressure proportional valve 222, loading solenoid valve 223 and high-low pressure conversion valve 224, high-pressure proportional valve 221, low-pressure proportional valve 222 and loading solenoid valve 223 are connected in parallel, and two ends are connected with air inlet butterfly valve 211, oil-gas bucket 212 respectively, high-low pressure conversion valve 224 is connected in series with low-pressure proportional valve 222.

[0030] In this embodiment, the booster host 2 is arranged in the pipeline for conveying nitrogen in the goaf of the coal mine underground, and the booster host 2 is used to complete the pressurization process of the nitrogen underground, so as to avoid the problem of pressure loss of the gas in the conveying pipeline through long-distance pipeline conveying. The booster host 2 uses an air compressor to pressurize alone, compared with the pressurization mode through a gas turbine combined with a centrifugal compressor, can be used in a narrow area, and meets the coal mine explosion-proof requirements. Through the arranged double-pressure switching system, nitrogen with an output pressure value of 0.3 MPa to 1.6 MPa can be realized to the nitrogen injection area, and nitrogen with an output pressure value greater than or equal to 2.0 MPa can be realized to the high-pressure nitrogen area. The nitrogen with sufficient flow and pressure is supplied to the coal mine underground fire extinguishing and nitrogen injection area, so as to meet the requirements of the coal mine nitrogen fire extinguishing technical specification on the required absolute pressure of the input nitrogen being not less than 0.2 MPa and the required flow of the design, and at the same time, the nitrogen source with sufficient pressure and flow can be provided for other high-pressure nitrogen areas.

[0031] When it is required to convert to nitrogen with a pressure of 0.3 MPa to 1.6 MPa, the booster host 2 is opened through the control assembly, the loading electromagnetic valve 223 is closed, the high-low pressure switching valve 224 is opened, the nitrogen input into the air compressor is loaded to 0.3 MPa to 1.6 MPa, at this time, the low-pressure proportional valve 222 is automatically opened, and the nitrogen with the required pressure value is continuously released.

[0032] When it is required to convert to nitrogen with a pressure greater than or equal to 2.0 MPa, the booster host 2 is opened through the control assembly, the loading electromagnetic valve 223 and the high-low pressure switching valve 224 are closed, and when the nitrogen is pressurized to a value greater than or equal to 2.0 MPa, the high-pressure proportional valve 221 is automatically opened, and the nitrogen with the required pressure value is continuously released.

[0033] In order to facilitate control, the control assembly is further included, the control assembly includes a mine explosion-proof intelligent controller, a remote control system and a parameter acquisition system; the mine explosion-proof intelligent controller is used to control the whole machine, each electric valve, and the opening and closing of the explosion-proof electric control / gas-driven switch; the remote control system is used to remotely control the coal mine underground equipment; the parameter acquisition system is used to acquire the real-time oxygen concentration of the goaf, the nitrogen outlet pressure, flow and temperature parameters of the nitrogen conveying pipeline, and perform calculation and processing; when the nitrogen shortage amount of the goaf is insufficient, the remote control system feeds back to the mine explosion-proof intelligent controller, and the mine explosion-proof intelligent controller adjusts the opening degree of each electric valve.

[0034] The parameter collection system comprises a hardware system and a software system. The hardware system mainly comprises sensors, a signal processing module, a data collection host and the like. The software system is a data analysis and processing software. The parameter collection system collects key parameters of the device through sensors, and performs amplification, filtering and gain adjustment on the electrical signals through the signal processing module, so as to ensure the accuracy and stability of the data. The data collection host is responsible for receiving and processing the data collected by the sensors, and converting the data into readable digital signals, which are displayed in the local or uploaded to the ground control room through the network.

[0035] The parameter collection system collects real-time oxygen concentration in the goaf, nitrogen outlet pressure, flow and temperature of the nitrogen conveying pipeline and other key parameters through various sensors, and transmits the parameters to the data collection host. Through the program written in the data analysis and processing software, in combination with the data of the goaf volume and air leakage volume collected in advance, the nitrogen shortage in the goaf is calculated through the following formula, and then fed back to the mine explosion-proof intelligent controller. By adjusting the opening of each electric valve, the pressure and flow of the booster host 2 are adjusted in real time to meet the demand of nitrogen injection in the goaf. The calculation formula of the nitrogen shortage in the goaf is as follows: In the formula, is the air leakage volume in the oxidation zone of the goaf, with the unit of m 3 / min; is the nitrogen shortage in the goaf, with the unit of m 3 / min; is the real-time supply amount of nitrogen in the goaf, with the unit of m 3 / min; is the average oxygen concentration in the oxidation zone of the goaf, with the unit of %; is the inertization and fire prevention index of the goaf, which is the critical oxygen concentration of coal spontaneous combustion, with the unit of %; is the nitrogen concentration of the injected nitrogen, with the unit of %; K is a standby coefficient, which is taken as 1.2-1.5 (in the goaf underground).

[0036] If the temperature of the goaf collected by the parameter collection system exceeds the preset upper limit of temperature, the mine explosion-proof intelligent controller adjusts the cooling water flow of the cooling system in the air compressor to adjust the input temperature of the goaf.

[0037] The gas supply end (ground nitrogen station), demand end (nitrogen injection area / high-pressure gas end) and coal mine underground booster device can be linked and controlled through the control assembly; the real-time oxygen concentration of the goaf, the nitrogen outlet pressure, flow and temperature of the nitrogen conveying pipeline and other key parameters are collected by the parameter acquisition system, transmitted to the data acquisition host, fed back to the mine explosion-proof intelligent controller after processing, and the pressure, flow, temperature and other parameters of the output nitrogen are adjusted in real time through the double-pressure switching system and cooling system of the air compressor.

[0038] Specifically, it also includes a gas buffer assembly, which includes a low-pressure gas buffer tank 61 and a high-pressure gas buffer tank 62, and the low-pressure gas buffer tank 61 and the high-pressure gas buffer tank 62 are arranged on the booster pipeline, and the low-pressure gas buffer tank 61 and the high-pressure gas buffer tank 62 are respectively located at both ends of the booster host 2.

[0039] The gas buffer assembly can be selected for use according to actual conditions, the low-pressure gas buffer tank 61 provided can provide a smooth gas source for the booster host 2, and the high-pressure gas buffer tank 62 provided can provide a smooth gas source for the equipment connected behind.

[0040] Specifically, the booster pipeline is also provided with a flow limiting valve 71 and a vortex flow meter 72, and the flow limiting valve 71 and the vortex flow meter 72 are arranged between the first electric valve 1 and the low-pressure gas buffer tank 61, and the output end of the flow limiting valve 71 is connected with the input end of the vortex flow meter 72.

[0041] The flow limiting valve 71 can control the flow entering the booster host 2, avoid excessive gas flow into the booster host 2, make the booster host difficult to handle and cause the service life to be reduced, and the vortex flow meter 72 provided can measure the pressure, temperature and flow of the nitrogen conveying key parameters for adjustment.

[0042] Specifically, the output end of the first electric valve 1 is connected with the nitrogen injection area through an overflow pipeline, and the overflow pipeline is connected with a backflow valve 9.

[0043] The backflow valve 9 is set to be opened when the gas pressure value in the pipeline is greater than or equal to 0.6 MPa, and the backflow valve 9 provided can prevent pressure overrun caused by failure of the booster host 2.

[0044] Specifically, the branch pipeline is also provided with a relief valve 31, and the input end of the relief valve 31 is connected with the output end of the second electric valve 3.

[0045] The relief valve 31 can play a protection role, when the high-pressure nitrogen area stops using gas and causes the pipeline to be pressurized, the relief valve 31 is used to release pressure to the original pipeline to the nitrogen injection area.

[0046] Specifically, the fourth electric valve 81 and the second one-way valve 82 are arranged on the atmospheric pressure conveying pipeline, and the output end of the fourth electric valve 81 is connected with the input end of the second one-way valve 82.

[0047] When it is not necessary to provide high-pressure nitrogen, the fourth electric valve 81 is opened, the first electric valve 1 is closed, and the booster host 2 is closed, and at this time, the nitrogen gas conveyed by the ground nitrogen injection station directly enters the nitrogen injection area through the fourth electric valve 81 and the second one-way valve 82.

[0048] Embodiment two

[0049] A coal mine nitrogen long-distance conveying and pressurizing method adopts the coal mine nitrogen long-distance conveying and pressurizing device in embodiment one, and specifically includes the following steps: When it is necessary to provide nitrogen gas with a pressure value of 0.3 MPa to 1.6 MPa to the nitrogen injection area, the first electric valve 1, the booster host 2 and the second electric valve 3 are opened, the third electric valve 5 is closed, and the double-pressure switching system is started to convert the nitrogen gas input into the booster host 2 into nitrogen gas with a pressure value of 0.3 MPa to 1.6 MPa and convey it to the nitrogen injection area; The process closes the third electric valve 5 and the fourth electric valve 81, and opens the first electric valve 1 and the second electric valve 3; the nitrogen gas conveyed by the ground nitrogen injection station enters the booster pipeline, sequentially passes through the first electric valve 1, the flow limiting valve 71, the vortex flow meter 72 and the low-pressure gas buffer tank 61, and then enters the booster host 2, and the nitrogen gas is pressurized to 0.3 MPa to 1.6 MPa by the double-pressure switching system in the booster host 2 and then output, during the conversion process of the double-pressure switching system, the booster host 2 is opened by the control assembly, the loading electromagnetic valve 223 is closed and the high-low pressure switching valve 224 is opened, the nitrogen gas input into the air compressor is pressurized to 0.3 MPa to 1.6 MPa and reaches the opening set value of the low-pressure proportional valve 222, and the nitrogen gas with the required pressure value is continuously released, and after the nitrogen gas is pressurized, it sequentially passes through the high-pressure gas buffer tank 62, the second electric valve 3 and the relief valve 31, and then enters the nitrogen injection area through the gas conveying pipeline.

[0050] When it is necessary to provide nitrogen gas with a pressure value greater than or equal to 2.0 MPa to the high-pressure nitrogen area, the first electric valve 1, the booster host 2 and the third electric valve 5 are opened, the second electric valve 3 is closed, and the double-pressure switching system is started to convert the nitrogen gas input into the booster host 2 into nitrogen gas with a pressure value greater than or equal to 2.0 MPa and then convey it to the high-pressure nitrogen area; The process closes the second electric valve 3 and the fourth electric valve 81, and opens the first electric valve 1 and the third electric valve 5; the nitrogen delivered by the ground nitrogen injection station enters the booster pipeline, and then enters the booster host 2 through the first electric valve 1, the flow limiting valve 71, the vortex flowmeter 72 and the low-pressure gas buffer tank 61, and is boosted to a pressure value greater than or equal to 2.0 MPa by the double-pressure switching system in the booster host 2, and is then output; during the switching process of the double-pressure switching system, the booster host 2 is opened, the loading electromagnetic valve 223 and the high-low pressure switching valve 224 are closed by the control assembly, the nitrogen input into the air compressor is boosted to a pressure value greater than or equal to 2.0 MPa and reaches the opening setting value of the high-pressure proportional valve 221, and the nitrogen of the required pressure value is continuously released, and then the boosted nitrogen enters the high-pressure nitrogen area through the high-pressure gas buffer tank 62, the first check valve 4 and the third electric valve 5 in sequence, and then enters the high-pressure nitrogen area through the gas delivery pipeline.

[0051] The above is only the preferred embodiment of the present application, and for those skilled in the art, many changes can be made to the specific implementation and application range according to the idea of the present application, as long as these changes do not deviate from the concept of the present application, and all belong to the protection scope of the present application.

Claims

1. A long-distance nitrogen transport and pressurization device for coal mines, connected to a ground nitrogen production station, characterized in that: The main pipeline, normal pressure conveying pipeline, booster pipeline, branch pipeline, first electric valve (1), booster host (2), second electric valve (3), first check valve (4) and third electric valve (5) are included, one end of the main pipeline is connected with the ground nitrogen station, and the other end of the main pipeline is connected with the normal pressure conveying pipeline and the booster pipeline, the other end of the normal pressure conveying pipeline is located in the nitrogen injection area, the other end of the booster pipeline is located in the high pressure nitrogen area, and the two ends of the branch pipeline are connected with the normal pressure conveying pipeline and the booster pipeline respectively. The first electric valve (1), the booster host (2), the first check valve (4) and the third electric valve (5) are sequentially assembled on the booster pipeline, the second electric valve (3) is assembled on the branch pipeline, one end of the branch pipeline is located at the input end of the first check valve (4), and the other end of the branch pipeline is located at the input end of the nitrogen injection area. The booster host (2) includes an air compressor and a double pressure switching system, the double pressure switching system is used for converting the nitrogen input into the air compressor into the pressure value required by the nitrogen injection area or the pressure value required by the high pressure nitrogen area and outputting to the nitrogen injection area or the high pressure nitrogen area.

2. The nitrogen long-distance conveying pressurizing device for coal mine of claim 1, wherein: The air compressor is provided with an air inlet butterfly valve (211) and an oil gas bucket (212), and the double pressure switching system is arranged between the air inlet butterfly valve (211) and the oil gas bucket (212).

3. The nitrogen long-distance conveying pressurizing device for coal mine of claim 2, wherein: The double pressure switching system includes a high pressure proportional valve (221), a low pressure proportional valve (222), a loading electromagnetic valve (223) and a high-low pressure conversion valve (224), the high pressure proportional valve (221), the low pressure proportional valve (222) and the loading electromagnetic valve (223) are connected in parallel and connected with the air inlet butterfly valve (211) and the oil gas bucket (212) at two ends, and the high-low pressure conversion valve (224) is connected in series with the low pressure proportional valve (222).

4. The nitrogen long-distance conveying pressurizing device for coal mine of claim 3, wherein: It also includes a gas buffer assembly, the gas buffer assembly includes a low pressure gas buffer tank (61) and a high pressure gas buffer tank (62), the low pressure gas buffer tank (61) and the high pressure gas buffer tank (62) are arranged on the booster pipeline, and the low pressure gas buffer tank (61) and the high pressure gas buffer tank (62) are located at two ends of the booster host (2) respectively.

5. The nitrogen long distance conveying pressurizing device for coal mine according to claim 4, characterized in that: The booster pipeline is also provided with a flow limiting valve (71) and a vortex flowmeter (72), and the flow limiting valve (71) and the vortex flowmeter (72) are arranged between the first electric valve (1) and the low pressure gas buffer tank (61), and the output end of the flow limiting valve (71) is connected with the input end of the vortex flowmeter (72).

6. The nitrogen long distance conveying pressurizing device for coal mine according to claim 5, characterized in that: The output end of the first electric valve (1) is connected with the overflow pipeline between the output end of the first electric valve (1) and the nitrogen injection area, and the overflow pipeline is connected with the reverse flow valve (9).

7. The nitrogen long distance conveying pressurizing device for coal mine according to claim 6, characterized in that: The branch pipeline is also provided with a relief valve (31), and the input end of the relief valve (31) is connected with the output end of the second electric valve (3).

8. The nitrogen long distance conveying pressurizing device for coal mine according to claim 7, characterized in that: The normal pressure conveying pipeline is provided with a fourth electric valve (81) and a second check valve (82), and the output end of the fourth electric valve (81) is connected with the input end of the second check valve (82).

9. The method for long-distance nitrogen gas transmission and pressure boosting for coal mines, which adopts the long-distance nitrogen gas transmission and pressure boosting device for coal mines according to any one of claims 1 to 8, and specifically comprises the following steps: when nitrogen gas with a pressure value of 0.3 MPa to 1.6 MPa is needed to be provided to the nitrogen injection area, the first electric valve (1), the pressure boosting host (2) and the second electric valve (3) are opened, the third electric valve (5) is closed, and the double-pressure switching system is started to convert the nitrogen gas input into the pressure boosting host (2) into nitrogen gas with a pressure value of 0.3 MPa to 1.6 MPa and deliver it into the nitrogen injection area; when nitrogen gas with a pressure value of greater than or equal to 2.0 MPa is needed to be provided to the high-pressure nitrogen area, the first electric valve (1), the pressure boosting host (2) and the third electric valve (5) are opened, the second electric valve (3) is closed, and the double-pressure switching system is started to convert the nitrogen gas input into the pressure boosting host (2) into nitrogen gas with a pressure value of greater than or equal to 2.0 MPa and deliver it into the high-pressure nitrogen area.

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