Coal mine goaf multi-point self-feedback resistance and integration of variable frequency injection fire prevention and extinguishing method

Abstract

The present application belongs to the technical field of coal spontaneous combustion prevention and control in the goaf of underground coal mining face, and specifically relates to a multi-point self-feedback inerting integrated variable frequency injection and spraying fire prevention and extinguishing method for the goaf of coal mine. The method comprises the following steps: calculating the required nitrogen injection flow for fire prevention and extinguishing in the goaf of working face; calculating the required amount of retardant to be sprayed in each cycle of inerting fire prevention in the goaf of working face; performing injection and spraying operation according to the injection amount and retardant amount calculated in steps 1 and 2 respectively as one injection and spraying cycle per shift; determining the oxygen content of each monitoring point of the goaf tube; calculating the average oxygen concentration of the oxidation zone of the goaf according to the oxygen content of each monitoring point, and then calculating the new nitrogen injection flow to correct the nitrogen injection flow in step 1, and adjusting the nitrogen injection flow of the injection and spraying system in step 3 to perform injection and spraying operation; monitoring the CO and C2H4 gas concentrations in real time during injection and spraying operation; if the CO and C2H4 gas concentrations exceed the standard, dynamically adjusting the nitrogen injection flow and the retardant concentration to perform injection and spraying operation.

Description

Technical Field

[0001] This invention belongs to the field of coal spontaneous combustion prevention technology in the goaf of underground coal mining faces, specifically a multi-point self-feedback inertia integrated variable frequency injection and extinguishing method for coal mine goaf. Background Technology

[0002] Spontaneous combustion fires in coal mines are a major hazard threatening safe production and a key focus of mine fire prevention and control efforts. Nitrogen injection and the spraying of inhibitors are preventative measures against spontaneous combustion. However, current technologies involve separate and complex processes for nitrogen injection and inhibitor spraying, hindering timely feedback and coordination. Furthermore, the fixed amounts of nitrogen injected and inhibitor sprayed prevent adjustments based on the oxidation level of residual coal in the goaf, making frequency conversion control impossible. Excessive spraying wastes resources, while insufficient spraying fails to meet fire prevention requirements, hindering the synergistic optimization of prevention measures and processes.

[0003] The integrated variable frequency injection and spraying fire extinguishing technology combining nitrogen injection and inhibitor spraying is of great theoretical and practical significance for controlling and reducing the occurrence of major safety incidents such as mine fires and gas explosions, especially for improving the mine's prevention of internal fires. Therefore, a multi-point self-feedback inertia integrated variable frequency injection and spraying fire extinguishing system and method for coal mine goaf areas is proposed to solve the above problems. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a multi-point self-feedback inertia integrated variable frequency injection and extinguishing method for fire prevention and suppression in coal mine goaf areas.

[0005] This invention adopts the following technical solution: a multi-point self-feedback inertia integrated variable frequency injection and extinguishing method for fire prevention and extinguishing in coal mine goaf areas, comprising:

[0006] Step 1: Calculate the nitrogen injection flow rate required for fire prevention and extinguishing in the goaf of the working face;

[0007] Step 2: Calculate the amount of inertizing agent required for each cycle of fire prevention in the goaf of the working face;

[0008] Step 3: Based on the nitrogen injection volume and inhibitor dosage calculated in Step 1 and Step 2 respectively, perform the injection operation as one injection cycle for each frame shift;

[0009] Step 4: Determine the oxygen content at each monitoring point in the goaf bundle tube;

[0010] Step 5: Calculate the average oxygen concentration in the oxidation zone of the goaf based on the oxygen content at each monitoring point, then calculate the new nitrogen injection flow rate to correct the nitrogen injection flow rate in Step 1, and adjust the nitrogen injection flow rate of the injection system in Step 3 for injection operation.

[0011] Step 6: During the injection operation, monitor the concentrations of CO and C2H4 gases in real time;

[0012] Step 7: If CO and C2H4 gases are detected to exceed the standard, dynamically adjust the nitrogen injection flow rate and inhibitor concentration for injection operation.

[0013] In some embodiments, the nitrogen injection flow rate required for inerting and fire prevention in the goaf of the working face in step 1 is shown in the following formula.

[0014]

[0015] In the formula: Q N —Nitrogen injection flow rate, m 3 / h;

[0016] Q0—Air leakage within the oxidation zone of the goaf, calculated through air volume testing, in meters. 3 / min;

[0017] C1—Average oxygen concentration in the oxidation zone of the goaf, taken as 10%–21% when initially calculating nitrogen injection amount;

[0018] C2—Inertization fire prevention index for goaf areas, taken as 10%;

[0019] C N —Nitrogen concentration in the injected nitrogen gas: 97%;

[0020] k—the reserve coefficient, which is usually taken as 1.2 to 1.5, but is now taken as 1.3.

[0021] In some embodiments, in step 2, the inhibitor is prepared into an inhibitory solution with a concentration of 4%, and the inhibitory dosage for each cycle of spraying at the coal face is calculated according to the following formula:

[0022] V=KrLShA

[0023] In the formula: V —Inhibitory dosage per cycle spraying at the coal mining face, in tons;

[0024] K —The margin for spraying the inhibitor solution on easily ignited parts is generally taken as 1.2;

[0025] r —Bulk density of coal remaining in the goaf, t / m³ 3 ;

[0026] L —Working surface length, in meters;

[0027] S —The width of a single spraying pass is 0.6m;

[0028] h —The thickness of the remaining coal is taken as 0.5m;

[0029] A —The dosage of inhibitor for residual coal can be calculated as 3.45 kg of inhibitor per ton of residual coal.

[0030] In some embodiments, in step 3, the spraying operation is performed using an aerosol inhibitor injection system, which includes:

[0031] Nitrogen injection pipeline, wherein the integrated inertia injection nozzle at the end of the nitrogen injection pipeline is located in the goaf area;

[0032] The inhibitor tank, inhibitor pump, atomizer, and inhibitor pipeline are connected in sequence.

[0033] A frequency converter is installed on the nitrogen injection line. A tee with an angle of less than 45 degrees is installed at the location where the frequency converter is connected to the nitrogen injection line to connect the inhibitor line.

[0034] In some embodiments, in step 4, an oxygen content monitoring system is used. The bundled tube monitoring system includes: bundled tube 1# measuring point, bundled tube 2# measuring point and bundled tube 3# measuring point set in the goaf area. Bundled tube 1# measuring point, bundled tube 2# measuring point and bundled tube 3# measuring point are connected to the bundled tube sampling pump through a monitoring bundled tube.

[0035] In some embodiments, the oxygen content of three monitoring points (1#, 2#, and 3#) in the goaf area is transmitted in real time to a wireless receiver. The wireless receiver then transmits the data back to the controller. The controller recalculates the nitrogen injection flow rate based on the latest oxygen concentration data to correct the nitrogen injection flow rate in step 1 and adjusts the nitrogen injection flow rate of the injection system in step 3.

[0036] In some embodiments, the distance between measuring point 1# and the return airway along the length of the working face is one-tenth of the working face length, and the distance between measuring point 2# and measuring point 1# and the distance between measuring point 3# and measuring point 2# are both one-quarter to one-third of the working face length.

[0037] In some embodiments, in step 6, the concentrations of CO and C2H4 gases are collected by a bundled tube monitoring system and CO and C2H4 gas sensors located at the upper corner of the roadway.

[0038] The CO and C2H4 gas concentrations from the bundle tube monitoring system and the upper corner sensor are transmitted in real time to the wireless receiver, which then transmits the data signals to the frequency converter.

[0039] In some embodiments, in step 7, the frequency converter dynamically adjusts the nitrogen injection flow rate and inhibitor concentration according to the range of index gas variation and the corresponding integrated inert gas injection standard given in Table 1.

[0040] Table 1. Reference Standard for Multi-Point Self-Feedback Inertia Integrated Variable Frequency Injection Volume

[0041] .

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] This invention creates a multi-point self-feedback inertia integrated variable frequency injection and spraying fire prevention and extinguishing system for coal mine goaf areas, which greatly improves the system integration of nitrogen injection and spraying inhibitors, simplifies the process flow, greatly improves labor efficiency, and reduces labor costs.

[0044] This invention establishes a technology and method for dynamically adjusting the injection volume of nitrogen and inhibitor based on abnormal changes in oxygen concentration in the oxidation zone of the goaf and abnormal changes in the characteristic gases of spontaneous combustion of residual coal. This achieves frequency conversion adjustment and dynamic control of the injection volume of nitrogen and inhibitor, avoiding the contradiction of excessive injection wasting manpower and resources and insufficient injection failing to meet fire prevention needs.

[0045] This invention comprehensively considers monitoring data of characteristic gases from spontaneous combustion of residual coal at multiple monitoring points to formulate injection and extinguishing technical parameters, avoiding misjudgments and inadequate fire prevention and extinguishing effects caused by the complexity of the goaf environment, thus greatly improving safety. Overall, this invention has significant social and economic benefits. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the multi-point self-feedback inertia integrated variable frequency injection fire prevention and extinguishing system for coal mine goaf areas according to the present invention.

[0047] In the diagram, 1-bunch tube sampling pump, 2-monitoring bundle tube, 3-CO and C2H4 gas sensors, 4-measuring point 1#, 5-measuring point 2#, 6-measuring point 3#, 7-inhibiting liquid tank, 8-inhibiting liquid pump, 9-nebulizer, 10-inhibiting agent pipeline, 11-bunch tube and sensor monitoring data wireless receiver, 12-nitrogen injection pipeline, 13-frequency converter controller, 14-inertia integrated injection nozzle. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] This invention provides a multi-point self-feedback inertia-inhibiting integrated variable frequency injection and spraying fire prevention and extinguishing method for coal mine goaf areas. The integrated inertia-inhibiting integrated variable frequency injection and spraying fire prevention and extinguishing system includes: a bundle tube sampling and monitoring system for the oxidation and spontaneous combustion of residual coal in the goaf area, consisting of a bundle tube sampling pump 1, a monitoring bundle tube 2, a bundle tube 1# measuring point 4, a bundle tube 2# measuring point 5, and a bundle tube 3# measuring point 6; CO and C2H4 gas sensors 3; a wireless receiver 11 for bundle tube and sensor monitoring data; an inertia liquefaction system consisting of an inertia liquid tank 7, an inertia liquid pump 8, an atomizer 9, and an inertia agent pipeline 10; a nitrogen injection pipeline 12; a variable frequency controller 13; and an integrated inertia-inhibiting injection and spraying port 14. The variable frequency injection and spraying method for fire prevention and extinguishing is as follows: First, based on the technical parameters of the working face mining, the required nitrogen injection flow rate and the amount of inhibitor to be sprayed in each cycle for fire prevention and extinguishing in the goaf are initially calculated. Then, based on the oxygen concentration data of the oxidizing zone obtained from three monitoring points in the goaf bundle tube, the nitrogen injection flow rate is recalculated and corrected to adjust the nitrogen injection flow rate of the injection and spraying system. Next, based on the CO and C2H4 gas concentrations monitored by the three monitoring points in the goaf bundle tube and the upper corner marker gas sensor, the nitrogen injection flow rate and inhibitor concentration are corrected in real time, dynamically adjusting the injection and spraying volume of the system. This achieves the goal of multi-point self-feedback integrated variable frequency injection and spraying for fire prevention and extinguishing, automatically correcting the nitrogen injection flow rate and inhibitor concentration based on multi-point monitoring data.

[0050] The specific process is as follows:

[0051] Step 1: Initial calculation of the nitrogen injection flow rate required for inerting and fire prevention in the goaf of the working face. According to the "Technical Specification for Nitrogen Fire Prevention and Extinguishing in Coal Mines", nitrogen injection for fire prevention should reduce the original oxygen content in the oxidation zone of the goaf to below the fire prevention inerting index. Therefore, the calculation method for the nitrogen injection flow rate required for inerting and fire prevention in the goaf of the working face is shown in Formula 1, based on the oxygen content in the oxidation zone of the goaf.

[0052] (1)

[0053] In the formula: Q N —Nitrogen injection flow rate, m 3 / h;

[0054] Q0—Air leakage within the oxidation zone of the goaf, calculated through air volume testing, in meters. 3 / min;

[0055] C1—Average oxygen concentration in the oxidation zone of the goaf, taken as 10%–21% when initially calculating nitrogen injection amount;

[0056] C2—Inertization fire prevention index for goaf areas, taken as 10%;

[0057] C N —Nitrogen concentration in the injected nitrogen gas: 97%;

[0058] k—the reserve coefficient, which is usually taken as 1.2 to 1.5, but is now taken as 1.3.

[0059] Step 2: Initial calculation of the amount of inhibitor required for each cycle of inerting and fire prevention in the goaf of the working face. The inhibitor is prepared into an inhibitory solution with a concentration of 4%. The amount of inhibitor to be sprayed per cycle of the coal mining face is calculated according to Formula 2.

[0060] V=KrLShA (2)

[0061] In the formula: V —Inhibitory dosage per cycle spraying at the coal mining face, in tons;

[0062] K —The margin for spraying the inhibitor solution on easily ignited parts is generally taken as 1.2;

[0063] r —Bulk density of coal remaining in the goaf, t / m³ 3 ;

[0064] L —Working surface length, in meters;

[0065] S —The width of a single spraying pass is 0.6m;

[0066] h —The thickness of the remaining coal is taken as 0.5m;

[0067] A —The dosage of inhibitor for residual coal can be calculated as 3.45 kg of inhibitor per ton of residual coal.

[0068] Step 3: The aerosol inhibitor injection system performs injection operations based on the nitrogen injection flow rate and inhibitor dosage calculated in Steps 1 and 2, with each frame shift as one injection cycle, to achieve the fire prevention purpose during normal mining of the working face.

[0069] The aerosol inhibitor injection system includes:

[0070] Nitrogen injection pipeline 12, wherein the inertia-resistant integrated injection nozzle 14 at the end of the nitrogen injection pipeline 12 is located in the goaf area;

[0071] The inhibitor tank 7, inhibitor pump 8, atomizer 9, and inhibitor pipeline 10 are connected in sequence.

[0072] A frequency converter 13 is installed on the nitrogen injection line 12. A tee with an angle of less than 45 degrees is set at the position where the nitrogen injection line 12 connects to the frequency converter 13 for connecting the inhibitor line 10.

[0073] The injection pipeline extends along the intake airway of the working face to the goaf, with the integrated inertia injection port 14 located 30m from the working face. The inhibitor pipeline 10 is connected to a 60-80m long high-pressure hose and a high-pressure valve about 50m from the inhibitor pump 8. The end of the high-pressure hose is connected to the atomizer 9.

[0074] Step 4: Based on the monitoring data of the goaf bundle tube monitoring system, determine the oxygen content of three monitoring points: bundle tube 1# measuring point 4, bundle tube 2# measuring point 5, and bundle tube 3# measuring point 6, and transmit the oxygen concentration data to the wireless receiver 11 in real time.

[0075] The aforementioned bundled tube monitoring system involves deploying a main bundled tube monitoring pipeline 2 in the return airway of the working face. As the working face advances, a bundled tube is pre-buried every 20m behind the support. The bundled tubes are wrapped with 2-inch protective iron pipes. Sampling pump 1 automatically collects samples, and the concentration of the sampled gas is analyzed using a gas chromatograph. A total of three monitoring points are deployed in the goaf area. The distance between monitoring point 1#4 and the return airway along the length of the working face is one-tenth of the working face length. The distances between monitoring point 2#5 and monitoring point 1#4, and between monitoring point 3#6 and monitoring point 2#5, are one-quarter to one-third of the working face length.

[0076] Specifically, based on the monitoring data from the goaf bundle tube monitoring system, the oxygen content at three monitoring points in the goaf—Monitoring Point 4 (1), Monitoring Point 5 (2), and Monitoring Point 6 (3)—is determined, and the oxygen concentration data is transmitted in real time to the wireless receiver 11.

[0077] Step 5: The wireless receiver 11 transmits the oxygen concentration data signal to the frequency converter 13. The frequency converter 13 has a built-in calculation program to calculate the average oxygen concentration of the oxidation zone in the goaf based on the oxygen content of each monitoring point, thereby obtaining the corrected parameter C1 in Formula 1. Then, the nitrogen injection flow rate is calculated again according to Formula 1. The frequency converter 13 performs injection operation by adjusting the nitrogen injection flow rate of the frequency converter control system according to the newly calculated nitrogen injection flow rate.

[0078] Step 6: During the injection operation, monitor the CO and C2H4 gas concentrations at monitoring points 4 (1#), 5 (2#), 6 (3#), and the upper corner sensor 3 in the bundle tube monitoring system in real time, and transmit the monitoring data to the wireless receiver 11 and the frequency converter 13 in real time.

[0079] CO and C2H4 gas sensors 3 are arranged at the upper corner of the working surface. The bundle tube and sensor monitoring data wireless receiver 11 are set in the air intake tunnel and are responsible for receiving the monitoring data of the bundle tube and the upper corner sensor 3. The wireless receiver 11 is connected to the frequency converter 13 in the air intake tunnel. The frequency converter 13 is connected to the nitrogen and atomized inhibitor injection system.

[0080] The monitoring points of the bundle tube monitoring system, the wireless receiver and the frequency converter, and the frequency converter and the injection system are connected via an RS485 bus.

[0081] Step 7: The wireless receiver 11 automatically feeds back the CO and C2H4 gas concentration monitoring data to the frequency converter 13. The controller 13 determines in real time whether the CO and C2H4 gas concentrations meet the target gas change range shown in Table 1. When they do, the frequency converter 13 dynamically adjusts the nitrogen injection flow rate and inhibitor concentration according to the integrated frequency conversion injection and spraying standard given in Table 1, thereby realizing multi-point self-feedback frequency conversion control of the integrated nitrogen injection and spraying aerosol inhibitor system.

[0082] Table 1. Multi-point self-feedback inertia integrated variable frequency injection reference standard

[0083] .

[0084] Table 1 provides a reference standard for multi-point self-feedback inertia integrated frequency conversion injection. This standard comprehensively considers the different variation ranges of coal spontaneous combustion marker gas concentrations at three monitoring points in the bundle tube and the upper corner under different oxidation and spontaneous combustion conditions of residual coal in the goaf. It sets three injection flow rate levels and provides targeted nitrogen and inhibitor injection flow rates, enabling the injection system to be dynamically and quantitatively controlled according to the degree of spontaneous combustion of residual coal. This solves the problems of previous fixed injection flow rates failing to address the waste of manpower and resources due to excessive injection and the inability to meet fire prevention requirements due to insufficient injection. Furthermore, CO and C2H4 are marker gases for coal oxidation and spontaneous combustion; using them as the basis for dynamic control of nitrogen and inhibitor injection flow rates is more accurate.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-point self-feedback inertia integrated variable frequency injection and extinguishing method for fire prevention and control in coal mine goaf areas, characterized in that, include: Step 1: Calculate the nitrogen injection flow rate required for fire prevention and extinguishing in the goaf of the working face; Step 2: Calculate the amount of inertizing agent required for each cycle of fire prevention in the goaf of the working face; Step 3: Based on the nitrogen injection flow rate and inhibitor dosage calculated in Step 1 and Step 2 respectively, perform the injection operation as one injection cycle for each frame shift; Step 4: Determine the oxygen content at each monitoring point in the goaf; In step 4, oxygen content is monitored using a bundled tube monitoring system. The bundled tube monitoring system includes: measuring point 1 (4), measuring point 2 (5), and measuring point 3 (6) set in the goaf area. Measuring point 1 (4), measuring point 2 (5), and measuring point 3 (6) are connected to the bundled tube sampling pump (1) through the monitoring bundled tube (2). The distance between measuring point 1 (4) and the return airway along the length of the working face is one-tenth of the working face length. The distance between measuring point 2 (5) and measuring point 1 (4) and the distance between measuring point 3 (6) and measuring point 2 (5) are both one-quarter to one-third of the working face length. The oxygen content of the three measuring points (4), 5, and 6) in the goaf area is transmitted in real time to the wireless receiver (11). Step 5: Calculate the average oxygen concentration in the oxidation zone of the goaf based on the oxygen content at each monitoring point, then calculate the new nitrogen injection flow rate to correct the nitrogen injection flow rate in Step 1, and adjust the nitrogen injection flow rate of the injection system in Step 3 for injection operation. In step 5, the wireless receiver (11) transmits the data signal to the frequency converter (13). The frequency converter (13) calculates the average oxygen concentration of the oxidation zone in the goaf based on the oxygen content of three measuring points: 1# measuring point (4), 2# measuring point (5), and 3# measuring point (6). Then, it calculates the new nitrogen injection flow rate to correct the nitrogen injection flow rate in step 1 and adjusts the nitrogen injection flow rate of the injection system in step 3. Step 6: During the injection operation, monitor the concentrations of CO and C2H4 gases in real time; In step 6, the concentrations of CO and C2H4 gases are collected by three monitoring points in the goaf area: point 1 (4), point 2 (5), and point 3 (6), as well as by a CO and C2H4 gas sensor (3) located at the upper corner of the roadway. The data is then transmitted in real time to a wireless receiver (11). Step 7: If CO and C2H4 gases are detected to exceed the standard, dynamically adjust the nitrogen injection flow rate and inhibitor concentration for injection operation; In step 7, the wireless receiver (11) automatically feeds back the monitored CO and C2H4 gas data to the frequency converter (13). The frequency converter (13) determines whether the CO and C2H4 gas concentrations meet the range of index gas changes shown in Table 1. When they meet the range, the frequency converter (13) dynamically adjusts the nitrogen injection flow rate and inhibitor concentration according to the integrated frequency injection and spraying standard of the inert gas in Table 1, thereby realizing the multi-point self-feedback frequency control of the integrated nitrogen injection and spraying aerosol inhibitor system. Table 1 。 2. The multi-point self-feedback inertia integrated variable frequency injection and extinguishing method for fire prevention and control in coal mine goaf areas according to claim 1, characterized in that, In step 1, the calculation method for the nitrogen injection flow rate required for fire prevention and extinguishing in the goaf of the working face is shown in the following formula. In the formula: Q N —Nitrogen injection flow rate, m 3 / h; Q0—Air leakage within the oxidation zone of the goaf, calculated through air volume testing, in meters. 3 / min; C1—Average oxygen concentration in the oxidation zone of the goaf, taken as 10%–21% when initially calculating nitrogen injection amount; C2—Inertization fire prevention index for goaf areas, taken as 10%; C N —Nitrogen concentration in the injected nitrogen gas: 97%; k—Reserve coefficient, taken as 1.2 to 1.

5.

3. The multi-point self-feedback inertia integrated variable frequency injection and extinguishing method for fire prevention and extinguishing in coal mine goaf areas according to claim 1, characterized in that, In step 2, the inhibitor is prepared into an inhibitory solution with a concentration of 4%. The dosage of inhibitor sprayed per cycle at the coal mining face is calculated using the following formula: V=KrLShA In the formula: V —Inhibitory dosage per cycle spraying at the coal mining face, in tons; K —The margin of the inhibitor solution sprayed on easily ignited parts; r —Bulk density of coal remaining in the goaf, t / m³ 3 ; L —Working surface length, in meters; S —The width of a single spraying pass is 0.6m; h —The thickness of the remaining coal is taken as 0.5m; A —The dosage of inhibitor for residual coal is calculated based on spraying 3.45 kg of inhibitor per ton of residual coal.

4. The multi-point self-feedback inertia integrated variable frequency injection and extinguishing method for fire prevention and control in coal mine goaf areas according to claim 1, characterized in that, In step 3, the spraying operation is performed using an aerosol inhibitor injection system, which includes: Nitrogen injection pipeline (12), wherein the inert injection nozzle (14) at the end of the nitrogen injection pipeline (12) is located in the goaf area; The inhibitor tank (7), inhibitor pump (8), atomizer (9) and inhibitor pipeline (10) are connected in sequence. A variable frequency controller (13) is installed on the nitrogen injection pipeline (12). A tee with an angle of less than 45 degrees is set at the position where the variable frequency controller (13) is connected to the nitrogen injection pipeline (12) for connecting the inhibitor pipeline (10).

Images