Safe closed purging equipment for disassembling liquid ammonia flange and use method of safe closed purging equipment
By using a safe, enclosed purging device for disassembling liquid ammonia flanges, and combining inert gas replacement with a vacuum pump, the safety risks and pollution problems during liquid ammonia flange disassembly are solved, achieving efficient and safe unloading of liquid ammonia.
Patent Information
- Application Number
- CN202610015680.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-07
- Publication Date
- 2026-02-17
AI Technical Summary
In the semiconductor and photovoltaic industries, when liquid ammonia flanges are disassembled, ammonia gas can easily escape, posing a high risk of poisoning, fire, and explosion. Furthermore, after disassembly, air can mix into the pipeline, causing pollution and affecting the manufacturing process.
Design a safe, enclosed purging device for disassembling liquid ammonia flanges. Through the combination of inert gas replacement, vacuum pump and venturi generator, multiple safety guarantees are achieved to ensure ammonia replacement and vacuuming. A redundant system is set up to improve unloading efficiency.
It effectively eliminates the risks of poisoning, fire, and explosion during the dismantling process, avoids air pollution of pipelines, and improves operational safety and work efficiency.
Smart Images
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of liquid ammonia conveying, in particular to a safe closed purging equipment for liquid ammonia flange dismounting and a use method thereof. BACKGROUND
[0002] In the semiconductor and photovoltaic industry, the core reason for the huge demand for liquid ammonia is that it is the key source of active nitrogen atoms in the nitriding process. In semiconductor manufacturing, ammonia gas formed after the gasification of liquid ammonia is mainly used in chemical vapor deposition (CVD) process to generate the crucial silicon nitride film. As the chip mask layer, passivation layer and dielectric gate, the film's uniformity and purity requirements increase exponentially with the continuous miniaturization of technology nodes, and the manufacturing process is superimposed, resulting in high ammonia gas consumption per unit capacity.
[0003] Due to the need to unload liquid ammonia, every time the tank car is replaced, the flange will be dismounted, and there will be residual gas in the pipeline. Ammonia has a strong irritating odor, even at low concentrations, which can cause serious irritation to the eyes and respiratory mucosa, causing tearing, coughing, and difficulty breathing. The release of residual gas during flange dismounting can easily cause on-site personnel to be poisoned. When ammonia gas and air are mixed to a certain concentration, they may cause burning or explosion when exposed to open flames, high heat or static electricity. During the dismounting process, if the residual gas is released into the air and mixed with air, and there is a source of ignition on site, the risk is extremely high. The residual liquid in the pipeline will rapidly vaporize at ambient temperature, causing a sharp expansion in volume. If the discharge or pressure relief is not properly managed, it may cause a sudden increase in pressure in the pipeline or seal, leading to a physical explosion or jet leak, posing a safety hazard. After dismounting the flange of the tank car, air will mix into the pipeline, causing contamination of the pipeline and having a significant negative impact on the process.
[0004] Therefore, it is necessary to provide a new safe closed purging equipment for liquid ammonia flange dismounting and a use method thereof to solve the above technical problems. SUMMARY
[0005] To solve the above technical problems, the present application provides a safe closed purging equipment for liquid ammonia flange dismounting and a use method thereof.
[0006] The safe closed purging equipment for liquid ammonia flange dismounting provided by the present application comprises a cabinet body and a disc surface pipeline valve installed in the cabinet body, and the disc surface pipeline valve comprises: a liquid ammonia connecting pipe, the two ends of which are respectively connected to the liquid phase outlet of the storage tank truck and the inlet of the conveying pump; an inert gas purging pipe, the two ends of which are respectively connected to an inert gas source and a liquid ammonia connecting unit, for purging and replacing the ammonia gas in the liquid ammonia connecting unit; a vacuum pipe, the two ends of which are respectively connected to a vacuum pump and the liquid ammonia connecting pipe, for vacuumizing the liquid ammonia connecting pipe; The detection piece is installed in the liquid ammonia connecting pipe and used for detecting the ammonia concentration and gas pressure of the liquid ammonia connecting pipe. The Venturi exhaust pipe is connected with the vacuum pipe and the Venturi generator exhaust port respectively and used for exhausting the gas in the liquid ammonia connecting pipe.
[0007] Preferably, the liquid ammonia connecting pipe comprises a main pipe and two auxiliary pipes, the two auxiliary pipes are used for connecting the liquid phase outlet of the tank truck, the two auxiliary pipes are provided with a pressure maintaining valve, the output ends of the two auxiliary pipes are fixedly connected with the main pipe, the end of the main pipe is connected with the inlet of the delivery pump, and the main pipe is provided with an emergency control valve.
[0008] Preferably, the inert gas purging pipe comprises a main pipe and two auxiliary pipes, one end of the main pipe is connected with the inert gas source, the other end of the main pipe is connected with the two auxiliary pipes, the main pipe is provided with a safety valve, a pressure indicator and a gas pressure detector, the two auxiliary pipes are connected with the two auxiliary pipes respectively, and the two auxiliary pipes are provided with a pressure maintaining valve and a pressure regulating valve.
[0009] Preferably, the vacuum pipe comprises a main pipe and two auxiliary pipes, one end of the main pipe is connected with the vacuum pump, the main pipe is provided with a pressure maintaining valve, the other end of the main pipe is connected with the two auxiliary pipes, the two auxiliary pipes are connected with the two auxiliary pipes respectively, and the two auxiliary pipes are provided with a pressure maintaining valve and a pressure regulating valve.
[0010] Preferably, the Venturi exhaust pipe comprises a main pipe, the two ends of the main pipe are connected with the main pipe and the Venturi generator exhaust port respectively, and the main pipe is provided with a pressure maintaining valve and a Venturi generator body.
[0011] Preferably, the Venturi exhaust pipe further comprises a main pipe, the two ends of the main pipe are connected with the inert gas source and the Venturi generator body respectively, and the main pipe is provided with a safety valve and a pressure regulating valve.
[0012] Preferably, the detection piece comprises an ammonia concentration detector and a gas pressure detector, and the ammonia concentration detector and the gas pressure detector are installed on the liquid ammonia connecting pipe.
[0013] Preferably, the detection piece comprises two ammonia concentration detectors and two gas pressure detectors, the two ammonia concentration detectors are installed on the two auxiliary pipes respectively, and the two gas pressure detectors are installed on the two auxiliary pipes respectively.
[0014] Preferably, the detection piece further comprises an intelligent control module, the intelligent control module comprises: The acquisition unit is connected with the detection member and is used for acquiring the ammonia concentration value and the gas pressure value detected by the detection member; The analysis unit is used for comparing the ammonia concentration value with a preset concentration value and comparing the gas pressure value with a preset gas pressure value, and obtaining comparison results of the two comparisons; The control unit is used for controlling the opening and closing states of the inert gas purging pipe, the vacuumizing pipe and the Venturi exhaust pipe according to the comparison results of the two comparisons in the analysis unit.
[0015] A use method of the safety closed purging equipment for liquid ammonia flange dismounting, based on the safety closed purging equipment for liquid ammonia flange dismounting, comprises the following steps: First step: before dismounting the liquid phase port flange of the storage tank tank car, the gas in the liquid ammonia connecting pipe is exhausted through the Venturi exhaust pipe, so that the gas pressure in the liquid ammonia connecting pipe reaches a predetermined negative pressure value one, the pressure in the liquid ammonia connecting pipe is maintained for a predetermined time, and the negative pressure pressure maintaining operation is completed; Second step: inert gas is filled into the liquid ammonia connecting pipe through the inert gas purging pipe, and when the gas pressure value in the liquid ammonia connecting pipe reaches a pressure preset value two, the inert gas purging pipe is closed; Third step: the gas in the liquid ammonia connecting pipe is extracted through the Venturi exhaust pipe, so that the gas in the liquid ammonia connecting pipe reaches a predetermined negative pressure value two; Fourth step: the gas in the liquid ammonia connecting pipe is extracted through the vacuumizing pipe, and a deep vacuumizing operation is performed, and when the gas in the liquid ammonia connecting pipe reaches a predetermined negative pressure value three, the vacuumizing pipe is closed; Fifth step: the operations of the second step to the fourth step are repeated multiple times, until the ammonia concentration in the liquid ammonia connecting pipe is within a safe range, inert gas is filled into the liquid ammonia connecting pipe through the inert gas purging pipe, and the gas pressure in the liquid ammonia connecting pipe is in a positive pressure state; Sixth step: after replacing the storage tank tank car, inert gas is filled into the liquid ammonia connecting pipe through the inert gas purging pipe, and when the gas pressure value in the liquid ammonia connecting pipe reaches a pressure preset value one, the pressure in the liquid ammonia connecting pipe is maintained for a predetermined time, and the positive pressure pressure maintaining operation is completed; Seventh step: inert gas is filled into the liquid ammonia connecting pipe through the inert gas purging pipe, and when the gas pressure value in the liquid ammonia connecting pipe reaches a pressure preset value two, the inert gas purging pipe is closed; Eighth step: the gas in the liquid ammonia connecting pipe is extracted through the Venturi exhaust pipe, so that the gas in the liquid ammonia connecting pipe reaches a predetermined negative pressure value two; Ninth step: the gas in the liquid ammonia connecting pipe is extracted through the vacuumizing pipe, and a deep vacuumizing operation is performed, and when the gas in the liquid ammonia connecting pipe reaches a predetermined negative pressure value three, the vacuumizing pipe is closed; Step 10: Repeat the operations of steps 7 to 9 for several times, and then normally supply liquid ammonia to the pipe through the liquid ammonia.
[0016] Compared with the related art, the safety closed purging equipment for liquid ammonia flange dismounting and the use method thereof have the following beneficial effects: 1. The combustible, explosive and toxic ammonia gas in the pipeline is replaced by inert gas, so that the risk of poisoning, fire and explosion in the dismounting and maintenance is fundamentally eliminated. After purging, the pipeline is filled with inert gas, which provides a safe physical environment for the operator to dismount the flange and replace the equipment, avoids leakage of dangerous residual liquid in the pipeline, and ensures safety during dismounting of the flange. In the specific implementation, the pipeline is evacuated by the high vacuum degree of the vacuum pump and the Venturi generator combined vacuum system, and finally the safety of the pipeline is ensured by repeatedly purging and replacing and vacuumizing.
[0017] 2. After replacing the storage tank tank car, the pipe and the vacuum pipe are purged by inert gas, and the liquid ammonia connecting pipe is continuously purged and vacuumized. Purging (positive pressure replacement) and vacuumizing (negative pressure cleaning) are two kinds of complementary safety measures, and the combination of the two forms multiple safety protection and avoids air pollution in the pipeline and valve.
[0018] 3. Two auxiliary pipes are arranged in the liquid ammonia connecting pipe, so that at least one pipe is always in operation or standby state, the ammonia liquid unloading efficiency is improved, the maintenance time is arranged flexibly, and it is not necessary to wait for the production shutdown window. One pipe can even be used for more complex maintenance, and the other pipe ensures operation. The use of the redundant system effectively improves the work efficiency. BRIEF DESCRIPTION OF DRAWINGS
[0019] Figure 1 The frame schematic diagram of the safety closed purging equipment for liquid ammonia flange dismounting provided by the present application is shown in the figure. Figure 2 The flow frame diagram of the use method of the safety closed purging equipment for liquid ammonia flange dismounting provided by the present application is shown in the figure. DETAILED DESCRIPTION
[0020] The present application will be further described below in combination with the drawings and embodiments.
[0021] Please refer to Figure 1 and Figure 2 , wherein, Figure 1 The frame schematic diagram of the safety closed purging equipment for liquid ammonia flange dismounting provided by the present application is shown in the figure. Figure 2 The flow frame diagram of the use method of the safety closed purging equipment for liquid ammonia flange dismounting provided by the present application is shown in the figure.
[0022] In the specific implementation process, as Figure 1 and Figure 2 shown, including the cabinet and installed in the cabinet plate pipeline valve, the plate pipeline valve includes: Liquid ammonia docking pipe, both ends of which are respectively connected to the liquid phase port outlet of the storage tank tanker and the inlet of the delivery pump; Nitrogen purge pipe, both ends of which are respectively connected to the nitrogen source and the liquid ammonia docking unit, for purging and replacing the ammonia gas in the liquid ammonia docking unit; Vacuum pipe, both ends of which are respectively connected to the vacuum pump and the liquid ammonia docking pipe, for vacuumizing the liquid ammonia docking pipe; Detection, installed in the liquid ammonia docking pipe, for ammonia gas concentration and gas pressure detection of the liquid ammonia docking pipe; Venturi exhaust pipe, both ends of which are respectively connected to the vacuum pipe and the venturi generator exhaust port, for discharging the gas in the liquid ammonia docking pipe; The liquid ammonia docking pipe includes a main pipe and two auxiliary pipes, both of which are used to connect the liquid phase port outlet of the storage tank tanker, both of which are provided with a pressure retaining valve, and the output ends of both auxiliary pipes are fixedly connected to the main pipe, the end of the main pipe is connected to the inlet of the delivery pump, and an emergency control valve is installed on the main pipe. Two auxiliary pipes are provided in the liquid ammonia docking pipe, which ensures that at least one pipeline is in operation or standby state at all times, improves the efficiency of ammonia liquid unloading, arranges the maintenance time flexibly, and does not have to wait for the production shutdown window. One pipeline can even be used for more complex maintenance, and the other pipeline ensures operation. The use of this kind of redundant system effectively improves the work efficiency; The nitrogen purge pipe includes a main pipe and two auxiliary pipes, one end of the main pipe is connected to the nitrogen source, the other end of the main pipe is connected to the two auxiliary pipes, a safety valve and a pressure indicator are installed on the main pipe, the two auxiliary pipes are respectively connected to the two auxiliary pipes, and a pressure retaining valve and a pressure regulating valve are installed on the two auxiliary pipes; The vacuum pipe includes a main pipe and two auxiliary pipes, one end of the main pipe is connected to the vacuum pump, a pressure retaining valve is installed on the main pipe, the other end of the main pipe is connected to the two auxiliary pipes, the two auxiliary pipes are respectively connected to the two auxiliary pipes, and a pressure retaining valve and a pressure regulating valve are installed on the two auxiliary pipes; The venturi exhaust pipe includes a main pipe, both ends of which are respectively connected to the main pipe and the venturi generator exhaust port, a pressure retaining valve and a venturi generator body are installed on the main pipe; The Venturi exhaust pipe also includes a main pipe five, the two ends of which are respectively connected to a nitrogen source and a Venturi generator body. A safety valve two and a pressure regulating valve three are installed on the main pipe five. The detection device includes two ammonia concentration detectors and two gas pressure detectors. The two ammonia concentration detectors are respectively installed on two auxiliary tubes, and the two gas pressure detectors are respectively installed on two auxiliary tubes. It also includes an intelligent control module, which comprises: Acquisition Unit: Connected to the detection element, used to acquire the ammonia concentration and gas pressure values detected by the detection element; Analysis unit: Used to compare the ammonia concentration value with the preset concentration value and the gas pressure value with the preset gas pressure value, and obtain the comparison results; Control unit: Used to control the opening and closing status of nitrogen purging pipe, vacuum pipe and venturi exhaust pipe based on the comparison results of the two in the analysis unit. The intelligent control module can collect the gas pressure and concentration in the pipe in real time, and can adopt the PLC control mode to avoid the risk of human operation error. A method for using a safe, enclosed purging device for disassembling a liquid ammonia flange, based on the aforementioned safe, enclosed purging device for disassembling a liquid ammonia flange, includes the following steps: Step 1: Before disassembling the liquid phase port flange of the storage tank truck, the gas in the liquid ammonia connection fitting is discharged through the Venturi vent fitting, so that the gas pressure in the liquid ammonia connection fitting reaches the predetermined negative pressure value, and the pressure in the liquid ammonia connection fitting is maintained without pressure rise for a predetermined time, thus completing the negative pressure holding operation. Step 2: Inject nitrogen into the liquid ammonia connection fitting through the nitrogen purging fitting. When the gas pressure in the liquid ammonia connection fitting reaches the preset pressure value of two, close the nitrogen purging fitting. Step 3: Extract the gas from the liquid ammonia connection fitting through the venturi exhaust fitting, so that the gas in the liquid ammonia connection fitting reaches the predetermined negative pressure value of two. Step 4: Extract the gas from the liquid ammonia connection fitting through the vacuum fitting to perform a deep vacuum operation. When the gas in the liquid ammonia connection fitting reaches the predetermined negative pressure value of three, close the vacuum fitting. Step 5: Repeat steps 2 to 4 multiple times until the ammonia concentration in the liquid ammonia connection fitting is within a safe range. Purge the fitting with nitrogen to introduce nitrogen into the liquid ammonia connection fitting, so that the gas pressure in the liquid ammonia connection fitting is positive. Establish and maintain a slightly positive nitrogen environment to effectively isolate air (oxygen, water vapor) and prevent it from flowing back into the liquid ammonia connection fitting, thereby improving the safety during replacement. Step 6: After replacing the tank truck, nitrogen is introduced into the liquid ammonia connection fitting through the nitrogen purging pipe fitting. When the gas pressure in the liquid ammonia connection fitting reaches the preset pressure value, it is maintained without pressure drop for a predetermined time to complete the positive pressure holding operation. Step 7: Inject nitrogen into the liquid ammonia connection fitting through the nitrogen purging fitting. When the gas pressure in the liquid ammonia connection fitting reaches the preset pressure value of two, close the nitrogen purging fitting. Step 8: Extract the gas from the liquid ammonia connection fitting through the venturi exhaust fitting, so that the gas in the liquid ammonia connection fitting reaches the predetermined negative pressure value of two. Step 9: Extract the gas from the liquid ammonia connection fitting through the vacuum fitting to perform a deep vacuum operation. When the gas in the liquid ammonia connection fitting reaches the predetermined negative pressure value of three, close the vacuum fitting. Step 10: Repeat steps 7 through 9 multiple times, and then supply liquid normally through the ammonia fittings.
[0023] In the specific implementation of this application, negative pressure holding and positive pressure holding are carried out before disassembling the liquid phase port flange and after changing the storage tank truck, respectively. Then, corresponding purging and vacuuming operations are carried out, which effectively purifies the residual gas in the liquid ammonia connection fittings, improves the safety during operation, and also avoids air mixing in and causing pollution to pipelines and valves. refer to Figure 1 In the diagram, from left to right: H is the process inlet, connected to the liquid phase outlet of the tank truck; D is the purging nitrogen inlet, used for purging process pipelines; A is the process outlet, connected to the transfer pump; E is the vacuum pump inlet, used for deep vacuuming of the process pipelines; C is the vent port of the Venturi generator, used for venting the Venturi generator; and F is the Venturi nitrogen inlet, used to drive the Venturi generator. In practice, the Venturi generator body uses high-pressure driving fluid (nitrogen) to create a high-speed, low-pressure zone at the throat through a constriction, thereby drawing in and mixing the gas in the system. Finally, the gas is discharged from the exhaust port of the Venturi generator. After the nitrogen enters from port F, the vacuum generated by the driving Venturi draws gas from the liquid ammonia connection fitting. The extracted gas mixes with the driving nitrogen inside the Venturi and is discharged from port C, safely sent to the flare or scrubbing tower. The circuits and controls involved in this invention are all existing technologies and will not be described in detail here.
[0024] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.
Claims
1. A safety closed purging apparatus for liquid ammonia flange disassembly, characterized in that, The utility model relates to a kind of liquid ammonia docking pipe fittings, which includes cabinet and installs the disc surface pipeline valve in cabinet, and the disc surface pipeline valve includes: Liquid ammonia docking pipe fittings, which are connected to the liquid phase outlet of the tank truck and the inlet of the delivery pump respectively at both ends; Inert gas purging pipe fittings, which are connected to the inert gas source and the liquid ammonia docking unit respectively at both ends, for purging and replacing ammonia gas in the liquid ammonia docking unit; Vacuum extraction pipe fittings, which are connected to the vacuum pump and the liquid ammonia docking pipe fittings respectively at both ends, for vacuum treatment of the liquid ammonia docking pipe fittings; Detection device, installed in the liquid ammonia docking pipe fittings, for ammonia gas concentration and gas pressure detection of the liquid ammonia docking pipe fittings; Venturi exhaust pipe fittings, which are connected to the vacuum extraction pipe fittings and the venturi generator exhaust port respectively at both ends, for exhausting gas in the liquid ammonia docking pipe fittings.
2. The safety closed purging apparatus for liquid ammonia flange dismounting according to claim 1, characterized in that, The liquid ammonia docking pipe fittings include a main pipe and two auxiliary pipes, both of which are used to connect the liquid phase outlet of the tank truck, and a pressure retaining valve is installed on each of the auxiliary pipes. The output ends of the auxiliary pipes are fixedly connected to the main pipe, the end of the main pipe is connected to the inlet of the delivery pump, and an emergency control valve is installed on the main pipe.
3. The safety closed purging apparatus for liquid ammonia flange dismounting according to claim 2, characterized in that, The inert gas purging pipe fittings include a main pipe and two auxiliary pipes, one end of the main pipe is connected to the inert gas source, the other end of the main pipe is connected to the two auxiliary pipes, a safety valve and a pressure indicator are installed on the main pipe, the two auxiliary pipes are connected to the two auxiliary pipes respectively, and a pressure retaining valve and a pressure regulating valve are installed on each of the auxiliary pipes.
4. The safety closed purging apparatus for liquid ammonia flange dismounting according to claim 2, characterized in that, The vacuum extraction pipe fittings include a main pipe and two auxiliary pipes, one end of the main pipe is connected to the vacuum pump, a pressure retaining valve is installed on the main pipe, the other end of the main pipe is connected to the two auxiliary pipes, the two auxiliary pipes are connected to the two auxiliary pipes respectively, and a pressure retaining valve and a pressure regulating valve are installed on each of the auxiliary pipes.
5. The safety closed purge apparatus for liquid ammonia flange dismounting according to claim 4, characterized in that, The venturi exhaust pipe fittings include a main pipe, which is connected to the main pipe and the venturi generator exhaust port at both ends, and a pressure retaining valve and a venturi generator body are installed on the main pipe.
6. The safety closed purging apparatus for liquid ammonia flange dismounting according to claim 5, characterized in that, The venturi exhaust pipe fittings also include a main pipe, which is connected to the inert gas source and the venturi generator body at both ends, and a safety valve and a pressure regulating valve are installed on the main pipe.
7. The safety closed purge apparatus for liquid ammonia flange dismounting according to claim 1, characterized in that, The detection device includes an ammonia gas concentration detector and a gas pressure detector, which are installed on the liquid ammonia docking pipe fittings.
8. The safety closed purging apparatus for liquid ammonia flange dismounting according to claim 2, characterized in that, The detection device includes two ammonia gas concentration detectors and two gas pressure detectors, which are installed on the two auxiliary pipes respectively.
9. The safety closed purge apparatus for liquid ammonia flange dismounting according to claim 1, characterized in that, It also includes an intelligent control module, which includes: A collection unit connected to the detection device for obtaining the ammonia gas concentration value and the gas pressure value detected by the detection device; An analysis unit for comparing the ammonia gas concentration value with the preset concentration value and comparing the gas pressure value with the preset gas pressure value, and obtaining the comparison results; An alarm unit for alarming when the comparison results do not meet the requirements. The control unit is configured to control the opening and closing of the inert gas purging pipe, the vacuumizing pipe and the Venturi exhaust pipe according to the comparison result of the two analysis units.
10. A method of using a safety closed purge apparatus for liquid ammonia flange disassembly, according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: Step 1: Before disassembling the liquid phase port flange of the storage tank tank car, the gas in the liquid ammonia connecting pipe is exhausted through the Venturi exhaust pipe, so that the gas pressure in the liquid ammonia connecting pipe reaches a predetermined negative pressure value one, and the negative pressure is maintained for a predetermined time without rising, and the negative pressure pressure maintaining operation is completed; Step 2: Inert gas is filled into the liquid ammonia connecting pipe through the inert gas purging pipe, and when the gas pressure value in the liquid ammonia connecting pipe reaches a pressure preset value two, the inert gas purging pipe is closed; Step 3: The gas in the liquid ammonia connecting pipe is extracted through the Venturi exhaust pipe, so that the gas in the liquid ammonia connecting pipe reaches a predetermined negative pressure value two; Step 4: The gas in the liquid ammonia connecting pipe is extracted through the vacuumizing pipe, and a deep vacuumizing operation is performed, and when the gas in the liquid ammonia connecting pipe reaches a predetermined negative pressure value three, the vacuumizing pipe is closed; Step 5: The operations of steps 2 to 4 are repeated multiple times until the ammonia concentration in the liquid ammonia connecting pipe is within a safe range, inert gas is filled into the liquid ammonia connecting pipe through the inert gas purging pipe, and the gas pressure in the liquid ammonia connecting pipe is in a positive pressure state; Step 6: After replacing the storage tank tank car, inert gas is filled into the liquid ammonia connecting pipe through the inert gas purging pipe, and when the gas pressure value in the liquid ammonia connecting pipe reaches a pressure preset value one, the pressure is maintained for a predetermined time without decreasing, and the positive pressure pressure maintaining operation is completed; Step 7: Inert gas is filled into the liquid ammonia connecting pipe through the inert gas purging pipe, and when the gas pressure value in the liquid ammonia connecting pipe reaches a pressure preset value two, the inert gas purging pipe is closed; Step 8: The gas in the liquid ammonia connecting pipe is extracted through the Venturi exhaust pipe, so that the gas in the liquid ammonia connecting pipe reaches a predetermined negative pressure value two; Step 9: The gas in the liquid ammonia connecting pipe is extracted through the vacuumizing pipe, and a deep vacuumizing operation is performed, and when the gas in the liquid ammonia connecting pipe reaches a predetermined negative pressure value three, the vacuumizing pipe is closed; Step 10: The operations of steps 7 to 9 are repeated multiple times, and then the liquid ammonia connecting pipe is used for normal liquid supply.