Asphalt emptying system

Abstract

The invention relates to an asphalt emptying system which comprises an underground emptying tank, an asphalt storage tank, a nitrogen pipeline, a breathing pipeline and an asphalt emptying header pipe, the nitrogen pipeline, the breathing pipeline and the asphalt emptying header pipe are arranged on the upper portion of the underground emptying tank, an extrusion pipeline is arranged on the lower portion of the underground emptying tank, and the other end of the extrusion pipeline is connected with the asphalt storage tank. The nitrogen pipeline, the breathing pipeline, the asphalt emptying header pipe and the extrusion pipeline are all provided with electromagnetic valves, all the electromagnetic valves are connected with a liquid level recording interlocking alarm instrument and a pressure recording control instrument, and a gas sealing bottom valve is arranged at the connecting position of the extrusion pipeline and the underground emptying groove. The workload of operators is reduced, a large amount of investment, operation cost, operation cost and maintenance cost are saved, operation is simplified, maintenance is very convenient, nitrogen serving as back pressure is prevented from being discharged, and the safety of the system is improved.

Description

Technical Field

[0001] The invention relates to the technical field of asphalt production in the coking field, and in particular to an asphalt venting system. Background Art

[0002] During the processing of coal tar, about 50% to 60% of medium-temperature asphalt is generally produced, which is a bulk product of tar processing. Modified asphalt is currently the main downstream product of medium-temperature asphalt, and is mainly used in the electrolytic aluminum industry to produce prebaked anodes, prepare battery rods or electrode binders.

[0003] The medium-temperature asphalt and modified asphalt products produced domestically are stored in asphalt depots. Regardless of asphalt production or storage, underground asphalt drain tanks are rarely installed. The asphalt pipelines are manually purged of liquid asphalt and returned to the asphalt storage tanks for processing. Because, even if an underground asphalt drain tank is installed and an asphalt submersible pump is installed in the drain tank, the asphalt submersible pump will soon be stuck due to intermittent operation. If a screw pump is selected, it needs to be purged clean after each operation for the next use, which is very cumbersome and cannot be automated.

[0004] Although underground asphalt vent tanks are rarely installed, they are very necessary in operation. It is very convenient to empty the asphalt pipeline into the underground vent tank. There is no need to worry about overpressure in the underground vent tank when blowing the pipeline to the underground vent tank, because the underground vent tank is pressure-resistant. However, when blowing back to the asphalt storage tank, the asphalt storage tank is not pressure-resistant. Therefore, great caution must be exercised in operation to prevent the occurrence of overpressure and rupture accidents in the asphalt storage tank.

[0005] Can nitrogen be used as back pressure to press the liquid asphalt discharged from the underground vent tank back into the asphalt storage tank? Theoretically, it is possible, but there is also a risk of sending a large amount of high-pressure nitrogen into the asphalt storage tank during the process of nitrogen pressing the liquid asphalt back into the asphalt storage tank, and the speed is faster, and the safety problem is difficult to solve.

[0006] In summary, when setting up an underground asphalt drain tank, the urgent problem to be solved is the convenience and safety of operation. It does not require complicated maintenance and simple operation is sufficient. Summary of the invention

[0007] In order to overcome the shortcomings of the prior art, the present invention provides an asphalt venting system, which uses nitrogen as back pressure, introduces high-pressure nitrogen, and presses the liquid asphalt emptied from the underground venting tank back into the asphalt storage tank, and arranges an air-sealing bottom valve between the asphalt extrusion pipeline and the underground venting tank. The function of this air-sealing bottom valve is to automatically close when the liquid asphalt is about to be discharged, thereby improving the safety of the system. The entire system is simple to operate, highly practical, can realize automated operation, is safe to operate, is simple to maintain, and has high economic value.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] An asphalt venting system comprises an underground venting tank, an asphalt storage tank, a nitrogen pipeline, a breathing pipeline and an asphalt venting main pipe. The nitrogen pipeline, the breathing pipeline and the asphalt venting main pipe are arranged on the upper part of the underground venting tank, and the other end of the breathing pipeline is connected to the gas main pipe. An extrusion pipeline is arranged at the lower part of the underground venting tank, and the other end of the extrusion pipeline is connected to the asphalt storage tank. The nitrogen pipeline, the breathing pipeline, the asphalt venting main pipe and the extrusion pipeline are all provided with solenoid valves, and all the solenoid valves are connected to a liquid level recording interlocking alarm instrument and a pressure recording control instrument. A gas sealing bottom valve is arranged at the connection position between the extrusion pipeline and the underground venting tank.

[0010] Furthermore, the asphalt venting system also includes a circulation pipeline and a bypass pipeline. One end of the circulation pipeline is connected to the outlet end of the solenoid valve on the extrusion pipeline, and the other end is connected to the underground venting tank. A gate valve is arranged on the circulation pipeline. The bypass pipeline is arranged in parallel with the breathing pipeline between the underground venting tank and the gas main pipe.

[0011] Furthermore, a throttling orifice plate is provided at the outlet end of the solenoid valve on the breathing pipeline.

[0012] Furthermore, a solenoid valve is arranged on the bypass pipeline, and the solenoid valve on the bypass pipeline is connected to a liquid level recording interlock alarm instrument and a pressure recording control instrument.

[0013] Furthermore, a second gate valve is provided on the extrusion pipeline.

[0014] Furthermore, the air sealing bottom valve includes a valve core and a valve seat. The valve core is a steel pipe with a strip-shaped hole on the side wall and a float on the top. The valve seat is a steel pipe with a flange on the bottom. The flange is connected to the extrusion pipeline. Constraint bolts are arranged on the side wall of the valve seat steel pipe. The valve core steel pipe is inserted into the valve seat steel pipe. The valve core float falls on the upper end of the top of the valve seat steel pipe, and the constraint bolts are arranged in the strip-shaped hole.

[0015] Furthermore, the asphalt venting method of the asphalt venting system has the following specific steps:

[0016] S1. Initially, gate valve 1 is in a closed state, gate valve 2 is in an open state, all solenoid valves are in a closed state, the solenoid valve on the bypass pipeline and the solenoid valve on the asphalt venting main pipe are opened, the underground venting tank is in a normal pressure state, and liquid asphalt can be sent into the underground venting tank through the asphalt venting main pipe. With the inflow of liquid asphalt, the valve core of the air sealing bottom valve rises under the action of buoyancy, and the air sealing bottom valve is in an open state;

[0017] S2. When the liquid level recording interlock alarm instrument shows that the liquid level is at the high limit, the interlock closes the solenoid valve on the bypass pipeline and the solenoid valve on the asphalt venting main pipe, opens the solenoid valve on the nitrogen pipeline and the solenoid valve on the extrusion pipeline, and the nitrogen pipeline is in the open state, and the extrusion pipeline is in the open state;

[0018] S3. The nitrogen pipeline fills nitrogen into the underground vent tank. Under the action of nitrogen, the liquid asphalt in the tank enters the extrusion pipeline through the strip hole of the gas sealing bottom valve, and the asphalt is sent to the asphalt storage tank through the extrusion pipeline;

[0019] S4. When the liquid level recording interlock alarm instrument shows that the liquid level is at the lower limit, the interlock closes the solenoid valve on the nitrogen pipeline and the solenoid valve on the extrusion pipeline, opens the solenoid valve on the breathing pipeline, and the nitrogen in the underground vent tank returns to the venting gas main pipe at a small flow rate under the control of the throttling orifice plate. When the pressure displayed by the pressure recording control instrument PRC01 before the valve is reduced to 50kPa, close the solenoid valve on the breathing pipeline, open the solenoid valve on the bypass pipeline and the solenoid valve on the asphalt venting main pipe, and the underground vent tank is in a normal pressure state;

[0020] S5, open gate valve 1, open the circulation pipeline, close gate valve 2, close the asphalt passage from the extrusion pipeline to the asphalt storage tank, introduce nitrogen purge into the extrusion pipeline from gate valve 2 to the underground vent tank, use nitrogen to purge the asphalt in the extrusion pipeline from the circulation pipeline back to the underground vent tank, then close gate valve 1 and open gate valve 2;

[0021] S6. During steps S1 to S5, the air sealing bottom valve is always in the open state. If the solenoid valve of the extrusion pipeline fails to close, or the liquid level measurement is wrong and the solenoid valve on the extrusion pipeline is not closed, the liquid asphalt in the underground vent tank will continue to be squeezed out until the air sealing bottom valve is closed due to the lack of buoyancy of the valve core float, and is closed under the pressure of nitrogen to prevent the discharge of high-pressure nitrogen.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) Nitrogen is used as back pressure. High-pressure nitrogen is introduced to pressurize the liquid asphalt discharged from the underground vent tank back to the asphalt storage tank, eliminating the need for a liquid asphalt delivery pump. The pressure-out pipeline is not easily blocked, which reduces maintenance time and the workload of operators, saving a lot of investment and operating costs, operating costs and maintenance costs, simplifying operations and making maintenance very convenient.

[0024] 2) A gas-sealing bottom valve is installed between the liquid asphalt extrusion pipeline and the underground vent tank. The function of this gas-sealing bottom valve is to automatically close when the liquid asphalt is about to be exhausted, preventing nitrogen as back pressure from being discharged into the asphalt storage tank, causing the asphalt storage tank to rupture due to overpressure, thereby improving the safety of the system, improving the system's working efficiency, and reducing the potential safety hazards to equipment and surrounding personnel during the liquid asphalt extrusion operation.

[0025] 3) Use liquid level recording interlock alarm instrument and pressure recording control instrument to realize automated operation, improve system work efficiency, and improve system mobility and flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of an asphalt venting system described in the present invention.

[0027] Figure 2 It is a schematic diagram of the connection structure of the underground venting tank and the air sealing bottom valve described in the present invention.

[0028] Figure 3 The invention relates to the air sealing bottom valve structure.

[0029] Figure 4 It is a schematic diagram of the valve core structure of the present invention.

[0030] Figure 5 It is a schematic diagram of the valve seat structure of the present invention.

[0031] In the figure: 1. Underground vent tank; 2. Asphalt storage tank; 3. Air sealing bottom valve; 4. Solenoid valve one; 5. Solenoid valve two; 6. Solenoid valve three; 7. Solenoid valve four; 8. Solenoid valve five; 9. Gate valve one; 10. Gate valve two; 11. Throttle orifice plate; 12. Equipment interface, flange and blind plate; 13. Extrusion pipeline; 14. Nitrogen pipeline; 15. Breathing pipeline; 16. Bypass pipeline; 17. Asphalt vent main pipe; 18. Circulation pipeline; 19. Gas main pipe; 20. Valve core; 21. Valve seat; 22. Float; 23. Flange; 24. Restraining bolt; 25. Nitrogen purge; LRSA01. Liquid level recording interlock alarm instrument; PRC01. Pressure recording control instrument; H. High limit; L. Low limit. DETAILED DESCRIPTION

[0032] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings:

[0033] like Figure 1-Figure 5As shown, an asphalt venting system includes an underground venting tank 1, an asphalt storage tank 2, a nitrogen pipeline 14, a breathing pipeline 15 and an asphalt venting main pipe 17. The nitrogen pipeline 14, the breathing pipeline 15 and the asphalt venting main pipe 17 are arranged on the upper part of the underground venting tank 1, the breathing pipeline 15 is connected to the underground venting tank 1 and the gas main pipe 19, the lower part of the underground venting tank 1 is arranged with an extrusion pipeline 13, and the other end of the extrusion pipeline 13 is connected to the asphalt storage tank 2, the nitrogen pipeline 14 is arranged with an electromagnetic valve 14, the breathing pipeline 15 is arranged with an electromagnetic valve 25, and the asphalt venting main pipe 17 is arranged with an electromagnetic valve 30. A solenoid valve four 7 is installed, and a solenoid valve five 8 is installed on the extrusion pipeline 13. All the solenoid valves are connected to the liquid level recording interlock alarm instrument LRSA01 and the pressure recording control instrument PRC01. A gas sealing bottom valve 3 is installed at the connection position between the extrusion pipeline 13 and the underground vent tank 1. An equipment interface, a flange and a blind plate 12 are installed at the lower part of the underground vent tank 1. The flange of the equipment interface is closed with a blind plate, and a hole is opened in the blind plate. The steel pipe of the valve seat 21 is inserted into the equipment interface and is welded to the blind plate. After the underground vent tank 1 is emptied of liquid, the gas sealing bottom valve 3 can be automatically closed to prevent the discharge of nitrogen as back pressure.

[0034] Furthermore, the asphalt venting system also includes a circulation pipeline 18 and a bypass pipeline 16. One end of the circulation pipeline 18 is connected to the outlet end of the solenoid valve 58 on the extrusion pipeline 13, and the other end is connected to the underground venting tank 1. A gate valve 19 is set on the circulation pipeline 18. When the liquid level recording interlock alarm instrument LRSA01 shows that it is at the lower limit, the interlock control solenoid valve 58 on the extrusion pipeline 13 is closed, and the underground venting tank 1 no longer stores asphalt into the asphalt storage tank 2. At this time, the gate valve 210 on the extrusion pipeline 13 is closed, the gate valve 19 on the circulation pipeline 18 is opened, and the extrusion pipeline 13 is connected to the nitrogen purge 25. The residual asphalt in the extrusion pipeline 13 will be sent back to the underground venting tank 1 through the circulation pipeline 18. The bypass pipeline 16 and the breathing pipeline 1 5 is arranged in parallel between the underground venting tank 1 and the diffused gas main pipe 19, the bypass pipeline 16 can quickly exhaust gas, so that the underground venting tank 1 is in a normal pressure state, the bypass pipeline 16 and the breathing pipeline 15 are both connected to the underground venting tank 1 and the diffused gas main pipe 19, when the solenoid valve 25 on the breathing pipeline 15 is opened, the solenoid valve 36 of the bypass pipeline 16 is closed, and the nitrogen in the underground venting tank 1 enters the diffused gas main pipe 19 with a very small flow rate to prevent the expansion of nitrogen from causing safety hazards to the system, when the system pressure drops to 50Kpa, the solenoid valve 25 is closed, the solenoid valve 36 is opened, and the bypass pipeline 16 is opened to transport the nitrogen in the underground venting tank to the diffused gas main pipe 19, and the bypass pipeline 16 has no throttling orifice plate 11, which speeds up the transportation speed and improves the working efficiency of the system.

[0035] Furthermore, a throttling orifice 11 is provided at the outlet end of the solenoid valve 25 on the breathing line 15, and the throttling orifice 11 controls the nitrogen flow in the breathing line 15, so that the nitrogen in the breathing line 15 returns to the gas main pipe 19 at a small flow rate.

[0036] Furthermore, a solenoid valve 3 6 is provided on the bypass pipeline 16, and the solenoid valve 3 6 on the bypass pipeline 16 is connected to the liquid level recording interlock alarm instrument LRSA01 and the pressure recording control instrument PRC01. When the pressure before the valve is reduced to 50 kPa, the solenoid valve 2 5 is closed, and the solenoid valve 3 6 on the bypass pipeline 16 is opened to speed up the transportation of nitrogen in the underground vent tank 1 to the gas main 19.

[0037] Furthermore, a gate valve 10 is provided on the extrusion pipeline 13. The gate valve 10 is closed when the residual asphalt in the extrusion pipeline 13 is purged to prevent the nitrogen used for purging from entering the asphalt storage tank 2, thereby improving the safety of the system.

[0038] Furthermore, the air sealing bottom valve 3 is composed of a valve core 20 and a valve seat 21; the valve core 20 is a section of steel pipe, the top end of which is welded to a buoy 22, the buoy 22 can generate buoyancy, and a strip-shaped hole is opened on the side wall of the steel pipe; the valve seat 21 is a section of steel pipe, the lower end of which is welded to a flange 23 for connecting the extrusion pipeline 13, and a small hole is opened on the side wall of the upper end, and a restraining bolt 24 is fixed to each small hole; the outer diameter of the steel pipe of the valve core 20 is slightly smaller than the inner diameter of the steel pipe of the valve seat 21, and the steel pipe of the valve core 20 is inserted into the steel pipe of the valve seat 21 Internally, the float 22 of the valve core 20 falls on the upper end of the steel pipe mouth of the valve seat 21, and the restraining bolt 24 on the valve seat 21 is installed through the strip hole on the side wall of the valve core 20. When the float 22 of the valve core 20 is located at the pipe mouth of the steel pipe of the valve seat 21, the air sealing bottom valve 3 is in a closed state. When there is liquid around, the valve core 20 rises due to buoyancy until it is restrained by the restraining bolt 24 and stops rising. The air sealing bottom valve 3 is in a fully open state, and the liquid enters through the strip hole and flows into the extrusion pipeline 13 from the lower part of the valve seat 21.

[0039] Furthermore, the asphalt venting method of the asphalt venting system has the following specific steps:

[0040] S1. Initially, gate valve 1 9 is in a closed state, gate valve 2 10 is in an open state, all solenoid valves are in a closed state, solenoid valve 3 6 on bypass pipeline 16 and solenoid valve 4 7 on asphalt venting main pipe 17 are opened, underground venting tank 1 is in a normal pressure state, liquid asphalt venting liquid can be sent into underground venting tank 1 through asphalt venting main pipe 17, with the inflow of liquid asphalt, the float 22 on the valve core 20 of the air sealing bottom valve 3 rises under the action of buoyancy, and the air sealing bottom valve 3 is in an open state;

[0041] S2. When the liquid level recording interlock alarm instrument LRSA01 shows that the liquid level is at the high limit H, the solenoid valve 3 6 on the bypass pipeline 16 and the solenoid valve 4 7 on the asphalt venting main pipe 17 are interlocked to close, and the solenoid valve 1 4 on the nitrogen pipeline 14 and the solenoid valve 5 8 on the extrusion pipeline 13 are opened, the nitrogen pipeline 14 is in the open state, and the extrusion pipeline 13 is in the open state;

[0042] S3, nitrogen pipeline 14 fills nitrogen into underground vent tank 1, and liquid asphalt in the tank enters extrusion pipeline 13 through the strip hole of the air sealing bottom valve 3 under the action of nitrogen, and asphalt is sent to asphalt storage tank 2 through extrusion pipeline 13;

[0043] S4. When the liquid level recording interlock alarm instrument LRSA01 shows that the liquid level is at the lower limit L, the solenoid valve 14 on the nitrogen pipeline 14 and the solenoid valve 58 on the extrusion pipeline 13 are interlocked and closed, and the solenoid valve 25 on the breathing pipeline 15 is opened. Under the control of the nitrogen throttling orifice 11 in the underground venting tank 1, a small flow rate is returned to the venting gas main pipe 19. When the pressure displayed by the pre-valve pressure recording control instrument PRC01 is reduced to 50kPa, the solenoid valve 25 on the breathing pipeline 15 is closed, and the solenoid valve 36 on the bypass pipeline 16 and the solenoid valve 47 on the asphalt venting main pipe 17 are opened. The nitrogen in the underground venting tank 1 is quickly transported to the gas main pipe 19, and the underground venting tank 1 is in a normal pressure state;

[0044] S5, open gate valve 19, open the circulation pipeline 18, close gate valve 210, close the asphalt passage from the extrusion pipeline 13 to the asphalt storage tank 2, introduce nitrogen purge 25 into the extrusion pipeline 13 on the side of the gate valve 210 leading to the underground vent tank 1, use nitrogen to purge the asphalt in the extrusion pipeline 13 from the circulation pipeline 18 back to the underground vent tank 1, then close gate valve 19, and open gate valve 210;

[0045] S6. During steps S1 to S5, the air sealing bottom valve 3 is always in an open state. If the solenoid valve 58 of the extrusion pipeline 13 fails to close, or the liquid level measurement is wrong and the solenoid valve 58 on the extrusion pipeline 13 is not closed, the liquid asphalt in the underground vent tank 1 will continue to be squeezed out until the air sealing bottom valve 3 is closed due to the lack of buoyancy of the valve core 20 and the float 22, and is closed under the pressure of nitrogen to prevent the discharge of high-pressure nitrogen and improve safety.

[0046] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An asphalt venting system, comprising an underground venting tank, an asphalt storage tank, a nitrogen pipeline, a breathing pipeline and an asphalt venting main pipe, characterized in that: A nitrogen pipeline, a breathing pipeline and an asphalt venting main pipe are arranged on the upper part of the underground venting tank, and the other end of the breathing pipeline is connected to the gas main pipe. An extrusion pipeline is arranged on the lower part of the underground venting tank, and the other end of the extrusion pipeline is connected to the asphalt storage tank. The nitrogen pipeline, the breathing pipeline, the asphalt venting main pipe and the extrusion pipeline are all provided with solenoid valves, and all the solenoid valves are connected to a liquid level recording interlocking alarm instrument and a pressure recording control instrument. A gas sealing bottom valve is arranged at the connection position between the extrusion pipeline and the underground venting tank.

2. The asphalt venting system according to claim 1, characterized in that: The asphalt venting system also includes a circulation pipeline and a bypass pipeline. One end of the circulation pipeline is connected to the outlet end of the solenoid valve on the extrusion pipeline, and the other end is connected to the underground venting tank. A gate valve is arranged on the circulation pipeline. The bypass pipeline is arranged in parallel with the breathing pipeline between the underground venting tank and the gas main pipe.

3. The asphalt venting system according to claim 1, characterized in that: A throttling orifice plate is arranged at the outlet end of the electromagnetic valve on the breathing pipeline.

4. The asphalt venting system according to claim 2, characterized in that: A solenoid valve is arranged on the bypass pipeline, and the solenoid valve on the bypass pipeline is connected to a liquid level recording interlock alarm instrument and a pressure recording control instrument.

5. The asphalt venting system according to claim 1, characterized in that: A second gate valve is arranged on the extrusion pipeline.

6. The asphalt venting system according to claim 1, characterized in that: The air sealing bottom valve includes a valve core and a valve seat. The valve core is a steel pipe with a strip-shaped hole on the side wall and a buoy on the top. The valve seat is a steel pipe with a flange on the bottom. The flange is connected to the extrusion pipeline. Constraint bolts are arranged on the side wall of the valve seat steel pipe. The valve core steel pipe is inserted into the valve seat steel pipe. The valve core buoy falls on the upper end of the top of the valve seat steel pipe, and the constraint bolts are arranged in the strip-shaped hole.

7. An asphalt venting method for an asphalt venting system according to claim 1, characterized in that: The specific steps of the asphalt venting method are as follows: S1. Initially, gate valve 1 is in a closed state, gate valve 2 is in an open state, all solenoid valves are in a closed state, the solenoid valve on the bypass pipeline and the solenoid valve on the asphalt venting main pipe are opened, the underground venting tank is in a normal pressure state, and liquid asphalt can be sent into the underground venting tank through the asphalt venting main pipe. With the inflow of liquid asphalt, the valve core of the air sealing bottom valve rises under the action of buoyancy, and the air sealing bottom valve is in an open state; S2. When the liquid level recording interlock alarm instrument shows that the liquid level is at the high limit, the interlock closes the solenoid valve on the bypass pipeline and the solenoid valve on the asphalt venting main pipe, opens the solenoid valve on the nitrogen pipeline and the solenoid valve on the extrusion pipeline, and the nitrogen pipeline is in the open state, and the extrusion pipeline is in the open state; S3. The nitrogen pipeline fills nitrogen into the underground vent tank. Under the action of nitrogen, the liquid asphalt in the tank enters the extrusion pipeline through the strip hole of the gas sealing bottom valve, and the asphalt is sent to the asphalt storage tank through the extrusion pipeline; S4. When the liquid level recording interlock alarm instrument shows that the liquid level is at the lower limit, the interlock closes the solenoid valve on the nitrogen pipeline and the solenoid valve on the extrusion pipeline, opens the solenoid valve on the breathing pipeline, and the nitrogen in the underground vent tank returns to the venting gas main pipe at a small flow rate under the control of the throttling orifice plate. When the pressure displayed by the pressure recording control instrument PRC01 before the valve is reduced to 50kPa, close the solenoid valve on the breathing pipeline, open the solenoid valve on the bypass pipeline and the solenoid valve on the asphalt venting main pipe, and the underground vent tank is in a normal pressure state; S5, open gate valve 1, open the circulation pipeline, close gate valve 2, close the asphalt passage from the extrusion pipeline to the asphalt storage tank, introduce nitrogen purge into the extrusion pipeline from gate valve 2 to the underground vent tank, use nitrogen to purge the asphalt in the extrusion pipeline from the circulation pipeline back to the underground vent tank, then close gate valve 1 and open gate valve 2; S6. During steps S1 to S5, the air sealing bottom valve is always in the open state. If the solenoid valve of the extrusion pipeline fails to close, or the liquid level measurement is wrong and the solenoid valve on the extrusion pipeline is not closed, the liquid asphalt in the underground vent tank will continue to be squeezed out until the air sealing bottom valve is closed due to the lack of buoyancy of the valve core float, and is closed under the pressure of nitrogen to prevent the discharge of high-pressure nitrogen.

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