CN111810832B - Vacuum multi-layer thermal insulation cryogenic container interlayer nitrogen flushing replacement system and method - Google Patents

Abstract

The invention discloses a nitrogen flushing and replacing system and a nitrogen flushing and replacing method for an interlayer of a vacuum multilayer heat-insulating low-temperature container, wherein the system comprises a nitrogen charging device, an automatic air outlet control valve, a vacuumizing device and a control system; the nitrogen charging device, the automatic air outlet control valve and the vacuumizing device are communicated with an interlayer of the vacuum multilayer heat insulation low-temperature container; the nitrogen charging device comprises a nitrogen source, a nitrogen heater and an air inlet control valve, wherein the nitrogen source is provided with an air supply valve, the air outlet end of the nitrogen source is connected with the air inlet end of the nitrogen heater, the air outlet end of the nitrogen heater is connected with the air inlet end of the air inlet control valve, and the air outlet end of the air inlet control valve is communicated with the interlayer; the air supply valve, the nitrogen heater, the air inlet control valve, the vacuumizing device and the automatic air outlet control valve are all in communication connection with the control system. By adopting the technical scheme, the invention has good interlayer gas replacement effect, is beneficial to improving the pumping efficiency of the replaced nitrogen, and can further obtain durable high-vacuum life.

Description

Vacuum multi-layer thermal insulation cryogenic container interlayer nitrogen flushing replacement system and method

Technical Field

The present invention belongs to the technical field of vacuum evacuation of interlayers of vacuum multi-layer thermal insulation cryogenic containers, and in particular relates to a nitrogen flushing and replacement system and method for interlayers of vacuum multi-layer thermal insulation cryogenic containers, which can completely replace moisture and other non-condensable gas molecules in the interlayers, and is used for replacing gas in the interlayers of cryogenic containers before vacuum evacuation.

Background technique

As the application scope of refrigerated liquefied gases becomes wider and wider, the requirements for thermal insulation performance of equipment for storing and transporting refrigerated liquefied gases are also getting higher and higher, especially for containers for storing and transporting deep-cold liquids such as liquid oxygen, liquid nitrogen, liquid hydrogen, liquid argon, and LNG. Generally, only high-vacuum multi-layer insulation structures can meet the thermal insulation requirements. This type of container has extremely high requirements for interlayer vacuum. The cold working interlayer vacuum degree needs to be better than 0.03Pa (absolute pressure) during the entire interlayer vacuum life cycle (5 years) of the container. It can be seen that interlayer vacuum is one of the important indicators that affect the thermal insulation performance of low-temperature containers, and it is an important technical link in the manufacturing and maintenance of vacuum multi-layer insulation containers.

Under the condition of structural solidification, interlayer vacuum is the only indicator that affects the insulation performance of vacuum multilayer insulated cryogenic containers. The traditional interlayer vacuuming process has the defects of high energy consumption, long time consumption, high labor consumption, and short vacuum life; in addition, the multilayer insulated container is coated with multiple layers of insulation materials on the inner container. The insulation material is composed of dozens or even hundreds of layers of film materials stacked and wound on the inner container. It has the characteristics of low thermal conductivity, many layers, large surface area, and close arrangement. These characteristics lead to the multilayer insulation material having problems such as poor heat transfer, large amount of adsorbed gas, and difficulty in desorption of adsorbed gas.

In response to the above problems, patent CN101021209A discloses a vacuum pumping method and device, including: a first gas conveying device having an air outlet; a first gas heater, an inlet of which is connected to the air outlet of the first gas conveying device, and an outlet of which is connected to the air inlet of the inner tube; a vacuum pumping unit, which is connected to the interlayer; a second gas conveying device having an air outlet; a second gas heater, an inlet of which is connected to the air outlet of the second gas conveying device, and an outlet of which is connected to the interlayer.

Patent No. CN102913749A discloses a vacuum pumping system and method for a large-volume low-temperature insulated container, which includes an air supply device, a vacuum pumping device and a heating device; the heating device includes an outer tank heating device and an inner tank heating device; the insulated container to be vacuum pumped includes an outer tank, an inner tank and an interlayer formed by the outer tank and the inner tank; the outer tank heating device is arranged on the outside of the outer tank of the insulated container to be vacuum pumped; the inner tank heating device is arranged on the inside of the inner tank of the insulated container to be vacuum pumped; the air supply device is connected with the inner tank of the insulated container to be vacuum pumped and the interlayer through pipelines; the vacuum pumping device is connected with the inner tank of the insulated container to be vacuum pumped and the interlayer through pipelines.

The solutions involved in the above patents all require flushing the gas in the interlayer through a gas supply device (or a gas delivery device) to replace the gas that is not easy to escape from the interlayer, and then use a vacuum device to extract the flushing gas to put the interlayer in a vacuum state, thereby improving the thermal insulation performance. However, in the above two technical solutions, the interlayer replacement adopts a closed inflation method, which is prone to overfilling or underfilling in actual operation. The replacement method is not ideal, which affects the vacuum degree of the interlayer and ultimately leads to poor thermal insulation performance of the container.

Summary of the invention

The purpose of the present invention is to address the problem that in the prior art, when the interlayer of a vacuum multi-layer insulated cryogenic container is replaced with nitrogen, overfilling and underfilling easily occur, resulting in poor vacuum degree of the interlayer and poor insulation performance of the container. A system and method for nitrogen flushing and replacement of the interlayer of a vacuum multi-layer insulated cryogenic container is proposed.

To achieve the above object, the present invention adopts the following technical solutions:

The present invention relates to a nitrogen flushing and replacement system for an interlayer of a vacuum multi-layer thermal insulation cryogenic container, which comprises a nitrogen charging device, an automatic gas outlet control valve, a vacuum pumping device and a control system; the nitrogen charging device, the automatic gas outlet control valve and the vacuum pumping device are all in communication with the interlayer of the vacuum multi-layer thermal insulation cryogenic container; the nitrogen charging device comprises a nitrogen source, a nitrogen heater and an air intake control valve, the nitrogen source is provided with an air supply valve, the air outlet end of the nitrogen source is connected to the air intake end of the nitrogen heater, the air outlet end of the nitrogen heater is connected to the air intake end of the air intake control valve, and the air outlet end of the air intake control valve is in communication with the interlayer; the air supply valve, the nitrogen heater, the air intake control valve, the vacuum pumping device and the automatic gas outlet control valve are all in communication connection with the control system.

Preferably, the nitrogen charging device also includes a first temperature sensor and a pressure sensor, the first temperature sensor is connected between the nitrogen heater and the air intake control valve, the pressure sensor is connected between the air intake control valve and the interlayer, and both the first temperature sensor and the pressure sensor are communicatively connected to the control system.

Preferably, the nitrogen charging device further comprises a pressure limiting valve and a flow limiting valve, the pressure limiting valve and the flow limiting valve are sequentially connected between the gas supply valve and the nitrogen heater, and the flow limiting valve is communicatively connected with the control system.

Preferably, the nitrogen charging device further comprises a safety valve, and the safety valve is connected between the nitrogen heater and the first temperature sensor.

Preferably, the vacuum pumping device is equipped with a vacuum pumping valve for controlling its switch, and the vacuum pumping device is connected between the air intake control valve and the pressure sensor, so that the vacuum pumping device and the nitrogen filling device are connected at the same connection port of the interlayer, and the vacuum pumping valve is communicatively connected with the control system.

Preferably, the vacuum pumping device further comprises an interlayer vacuum pumping valve, and the interlayer vacuum pumping valve is connected between the pressure sensor and the interlayer.

Preferably, the vacuum pumping device further comprises a vacuum gauge for detecting the vacuum degree of the interlayer, the vacuum gauge is connected between the air intake control valve and the pressure sensor, and the vacuum gauge is communicatively connected with the control system.

Preferably, a second temperature sensor for detecting the temperature of the gas discharged from the interlayer is connected between the automatic gas outlet control valve and the interlayer, and the second temperature sensor is in communication connection with the control system.

The present invention also relates to a nitrogen flushing and replacement method based on the above-mentioned vacuum multi-layer thermal insulation cryogenic container interlayer nitrogen flushing and replacement system, which comprises the following steps:

S1. Set the vacuum threshold, and the control system starts the vacuum device to evacuate the interlayer;

S2. When the vacuum degree of the interlayer reaches a value lower than the vacuum degree threshold, the control system turns off the vacuum pumping device and stops pumping the interlayer. At the same time, the control system opens the gas supply valve, the nitrogen heater and the gas inlet control valve. The nitrogen source provides nitrogen, which is heated and filled into the interlayer. When the pressure of the interlayer reaches ~110KPa, the control system further opens the automatic gas outlet control valve to continuously fill and discharge nitrogen, thereby replacing the original gas in the interlayer.

S3. The control system closes the automatic gas outlet control valve, closes the gas supply valve and the gas inlet control valve, and at the same time, the control system starts the vacuum pump to extract the nitrogen in the interlayer;

S4. Repeat steps S2 and S3 several times until the original gas in the interlayer is completely exhausted and the nitrogen is completely pumped out.

Preferably, step S2 also includes setting a nitrogen temperature range, the nitrogen temperature is controlled within the nitrogen temperature range, the temperature of the nitrogen filled into the interlayer is measured by a first temperature sensor and the temperature information is transmitted to the control system, and the control system controls the switch of the nitrogen heater according to the temperature measured by the first temperature sensor.

Compared with the prior art, the technical solution provided by the present invention has the following technical effects:

The vacuum multi-layer insulated cryogenic container interlayer nitrogen flushing and replacement system of the present invention comprises a nitrogen filling device, an automatic gas outlet control valve and a vacuum pumping device. When replacing the gas in the interlayer, heated nitrogen is filled in while the replacement gas is released, and the pressure of the interlayer is controlled at a slightly positive pressure, and overfilling or underfilling will not occur. When evacuating, a negative pressure is formed in the interlayer space relative to the insulation material layer, so that the vaporized moisture and non-condensable gas adsorbed by the deep insulation material can be desorbed. Flushing the interlayer with flowing hot nitrogen is conducive to entraining and flushing the moisture and non-condensable gas components desorbed from the interlayer material out of the interlayer, so that the replacement effect is thorough, and the vacuum degree and insulation of the cryogenic container are improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a structural diagram of a nitrogen flushing and replacement system for an interlayer of a vacuum multi-layer thermally insulated cryogenic container according to an embodiment of the present invention;

FIG2 is a structural diagram of a nitrogen flushing and replacement system for an interlayer of a vacuum multilayer thermally insulated cryogenic container according to a second embodiment;

FIG3 is a structural diagram of the inner container heating device in Example 2;

FIG4 is a structural diagram of the outer container heating device in Example 2;

FIG5 is a graph showing the change in vacuum degree of the interlayer of a cryogenic container over time after the interlayer is flushed and evacuated using the present invention.

Among them: 1. nitrogen source; 2. gas supply valve; 3. pressure limiting valve; 4. current limiting valve; 5. nitrogen heater; 6. safety valve; 7. first temperature sensor; 8. air intake control valve; 9. vacuum gauge; 10. vacuum valve; 11. pressure sensor; 12. interlayer vacuum valve; 13. insulation layer; 14. outer container heating device; 15. outer container; 16. inner container; 17. second temperature sensor; 18. automatic gas outlet control valve; 19. inner container heating device; 20. vacuum device; 21. control system; 22. first circulation fan; 23. first gas heater; 24. inner container air intake valve; 25. inner container air outlet valve; 26. drying room; 27. second circulation fan, 28. second gas heater; 29. bottom gas channel; 30. top gas channel.

Detailed ways

In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with embodiments and drawings. The embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

Embodiment 1

The present embodiment relates to a vacuum multi-layer insulated cryogenic container interlayer nitrogen flushing and replacement system, which is used to evacuate the interlayer of the vacuum multi-layer insulated cryogenic container. The vacuum multi-layer insulated cryogenic container includes an outer container 15 and an inner container 16. An interlayer is formed between the outer container 15 and the inner container 16. An insulating layer 13 is provided on the periphery of the inner container 16. The insulating layer 13 is composed of dozens or even hundreds of layers of thin film materials stacked and then wound on the inner container 7. It has the characteristics of small thermal conductivity and large number of layers, so that the vacuum multi-layer insulated cryogenic container has better insulation performance.

1 , the above-mentioned vacuum multi-layer insulated cryogenic container interlayer nitrogen flushing and replacement system includes a nitrogen filling device, an automatic gas outlet control valve, a vacuum pumping device and a control system. The nitrogen filling device, the automatic gas outlet control valve and the vacuum pumping device are all connected to the interlayer of the vacuum multi-layer insulated cryogenic container.

The nitrogen charging device comprises a nitrogen source 1, a pressure limiting valve 3, a flow limiting valve 4, a nitrogen heater 5, a safety valve 6, a first temperature sensor 7, an air intake control valve 8 and a pressure sensor 11. The nitrogen source 1 is provided with a gas supply valve 2. The outlet end of the nitrogen source 1 is connected to the inlet end of the nitrogen heater 5. The pressure limiting valve 3 and the flow limiting valve 4 are connected between the nitrogen source 1 and the nitrogen heater 5. The pressure limiting valve 3 can limit the nitrogen pressure to ≤0.2MPa. The flow limiting valve 4 can adjust the valve opening according to the size of the pumped space to realize the function of adjusting the gas flow. The outlet of the nitrogen heater 5 is connected to the inlet end of the nitrogen heater 5. The gas end is connected to the gas inlet end of the gas inlet control valve 8, and the first temperature sensor 7 is connected between the nitrogen heater and the gas inlet control valve to measure the temperature of the output nitrogen; the safety valve 6 is connected between the nitrogen heater 5 and the first temperature sensor 7, and the set pressure of the safety valve is ≤0.2MPa. When the nitrogen filling device has safety problems such as blockage, the safety valve 6 automatically opens to release the nitrogen in the nitrogen filling device; the gas outlet end of the gas inlet control valve 8 is connected to the interlayer, and the pressure sensor 11 is connected between the gas inlet control valve 8 and the interlayer to measure the gas pressure of the output nitrogen.

The above-mentioned first temperature sensor 7 and pressure sensor 11 are both communicatively connected to the control system 21, and the measured nitrogen output temperature and pressure values are transmitted to the control system 21; the above-mentioned gas supply valve 2, pressure limiting valve 3, flow limiting valve 4, nitrogen heater 5, safety valve 6 and intake control valve 7 are all communicatively connected to the control system 21, and the control system 21 controls the switching states of the gas supply valve 2, nitrogen heater 5 and intake control valve 7 through the measured values of the first temperature sensor 7 and the pressure sensor 11, and adjusts the flow limiting value of the flow limiting valve 4 through the control system 21.

The vacuum pumping device 20 is equipped with a vacuum pumping valve 10 for controlling its switch. The vacuum pumping device is connected between the air intake control valve 8 and the pressure sensor 11, so that the vacuum pumping device 20 and the nitrogen charging device are connected at the same connection port of the interlayer. The vacuum pumping valve 10 is communicated with the control system 21, and the switch state of the vacuum pumping valve 10 is controlled by the control system 21; the vacuum pumping device 20 also includes an interlayer vacuum valve 12, which is connected between the pressure sensor 11 and the interlayer, and the interlayer vacuum valves are all communicated with the control system; the vacuum pumping device 21 also includes a vacuum gauge 9 for detecting the vacuum degree of the interlayer, the vacuum gauge 9 is connected between the air intake control valve 8 and the pressure sensor 11, the vacuum gauge 9 is communicated with the control system 21, and the vacuum degree detected is transmitted to the control system 21 for display.

A second temperature sensor 17 for detecting the temperature of the interlayer exhaust gas is also connected between the automatic gas outlet control valve 18 and the interlayer. Both the automatic gas outlet control valve 18 and the second temperature sensor 17 are communicatively connected to the control system 21. The interlayer exhaust gas temperature measured by the second temperature sensor 17 is transmitted to the control system 21 for display. The automatic gas outlet control valve 18 controls the air pressure value during its exhaust through the control system 21.

The nitrogen flushing method based on the above-mentioned vacuum multi-layer thermal insulation cryogenic container interlayer nitrogen flushing replacement system comprises the following steps:

S1. The control system 21 is used to set the vacuum threshold (the range of the vacuum threshold is 10Pa to 300Pa), the control system 21 starts the vacuum pumping device 20, specifically, the vacuum valve 10 and the interlayer evacuation valve 12 are opened to evacuate the interlayer, and the vacuum is detected by the vacuum gauge 9 during the evacuation process;

S2. When the vacuum degree of the interlayer is lower than the vacuum degree threshold, the control system 21 turns off the vacuum pumping device 20, that is, turns off the vacuum pumping valve 10, stops pumping the interlayer, and at the same time, sets the nitrogen temperature range (nitrogen temperature range is 100°C to 250°C) through the control system 21, opens the gas supply valve 2, the nitrogen heater 5 and the air intake control valve 8, and the nitrogen source 1 provides nitrogen, which is heated by the nitrogen heater 5 and then filled into the interlayer; sets the pressure threshold of the interlayer (for example, 110KPa micro-positive pressure), and when the pressure of the interlayer rises to the pressure threshold, the control system 21 further opens the automatic air outlet control valve 18, and continues to fill and exhaust nitrogen for a period of time, generally for 1 to 12 hours, so that the interlayer There is always flowing nitrogen in the interlayer, which replaces the original gas in the interlayer. The nitrogen temperature is controlled within the nitrogen temperature range. The temperature of the nitrogen filled into the interlayer is measured by the first temperature sensor 7 and the temperature information is transmitted to the control system. The temperature of the gas discharged from the interlayer is measured by the second temperature sensor 17. The control system 21 controls the switch of the nitrogen heater 5 according to the temperatures measured by the first temperature sensor 7 and the second temperature sensor 17, thereby controlling the nitrogen temperature in the interlayer. In the above process, the opening of the flow limiting valve 4 is adjusted at different stages. When the interlayer pressure does not reach the pressure threshold during the nitrogen filling stage, the flow limiting valve 4 opens at a large opening to maintain a large flow rate. In the stage where nitrogen filling and nitrogen exhaust are carried out simultaneously, the opening of the flow limiting valve 4 needs to be closed to maintain a small flow rate.

S3. The control system 21 closes the automatic gas outlet control valve 18, closes the gas supply valve 2 and the gas inlet control valve 8, and at the same time, the control system 21 starts the vacuum pump 20 to extract the nitrogen in the interlayer;

S4. Set the number of nitrogen flushing and replacement times (the number of nitrogen flushing and replacement times is generally 4 to 15 times), repeat steps S2 and S3 to the number of nitrogen flushing and replacement times, until the original gas in the interlayer is completely exhausted and all the nitrogen is extracted.

Embodiment 2:

2 , the vacuum multi-layer insulated cryogenic container interlayer nitrogen flushing and replacement system of this embodiment is additionally provided with an inner container heating device 19 and an outer container heating device 14 compared with the first embodiment.

In this embodiment, the structures of the nitrogen filling device, the automatic gas outlet control valve 18, the vacuum device 20 and the control system 21 and the connection relationship with the vacuum multi-layer insulated low-temperature container are the same as those in Example 1, and will not be elaborated in this embodiment; the inner container heating device 19 can provide circulating clean air or nitrogen at room temperature to 300°C, and is controlled by the control system 21, so as to achieve a cyclic stable heating condition, thereby heating the inner container; the outer container heating device 14 can accommodate the evacuated container, can provide circulating clean air at room temperature to 250°C, and is controlled by the control system, so as to achieve a cyclic stable heating condition, thereby heating the outer container.

3 , the inner container heating device 19 includes a first circulation fan 22, a first gas heater 23, an inner container air inlet valve 24 and an inner container air outlet valve 25. The air inlet end and the air outlet end of the inner container heating device 19 are respectively connected to the inner container air inlet and outlet.

4 , the outer container heating device 14 includes a drying room 26, a second circulation fan 27, and a second gas heater 28. The drying room 26 can accommodate the evacuated container. A bottom gas channel 29 is provided near the bottom plate inside the drying room 26, and a top gas channel 30 is provided near the top plate inside the drying room 26. The air outlet ends of the second circulation fan 27 and the second gas heater 28 are connected to the bottom gas channel 29, and the air inlet ends of the second circulation fan 27 and the second gas heater 28 are connected to the top gas channel 30.

The steps of flushing the interlayer of the vacuum multi-layer thermally insulated cryogenic container using the interlayer nitrogen flushing and replacement system of the present embodiment include:

S0. Set the inner circulation heating temperature range (the inner circulation heating temperature range is 100℃～300℃) and the outer circulation heating temperature range (the outer circulation heating temperature range is 100℃～200℃), turn on the inner container heating device 19 to heat the inner container circulation, and control the inner circulation gas temperature within the inner circulation heating temperature range; turn on the outer container heating device 14 to heat the outer container circulation, and control the outer circulation gas temperature within the outer circulation heating temperature range.

S1. Use the control system to set the upper limit of the inner circulation heating temperature (the upper limit of the inner circulation heating temperature is 300°C), the lower limit of the inner circulation heating (the lower limit of the inner circulation heating is 100°C), the upper limit of the outer circulation heating temperature (the upper limit of the outer circulation heating temperature is 200°C), the lower limit of the outer circulation heating (the lower limit of the outer circulation heating is 100°C) and the vacuum threshold (the vacuum threshold range is 10Pa to 300Pa). When the outlet gas temperature of the inner container reaches the lower limit of the inner circulation heating, the control system 21 starts the vacuum pumping device 20, specifically, opens the vacuum pumping valve 10 and the interlayer evacuation valve 12 to evacuate the interlayer. During the evacuation process, the vacuum gauge 9 detects the vacuum degree. In the project of arrangement 20, when the temperature of the gas discharged from the exhaust port of the inner container reaches the upper limit of the inner circulation heating temperature, the inner drying gas heater stops heating; when the temperature of the gas discharged from the exhaust port of the inner container is lower than the lower limit of the inner circulation heating, the inner drying gas heater starts heating to maintain the temperature of the discharged gas between the lower limit of the inner circulation heating and the upper limit of the inner circulation heating temperature; when the gas temperature in the drying room reaches the upper limit of the outer circulation heating temperature, the outer drying gas heater stops heating; when the gas temperature in the drying room is lower than the lower limit of the outer circulation heating, the outer drying gas heater starts heating to maintain the gas temperature in the drying room between the lower limit of the outer circulation heating and the upper limit of the outer circulation heating temperature;

S2. Use the control system to set the nitrogen temperature range (nitrogen temperature range is 100°C ~ 250°C). When the vacuum degree of the interlayer reaches the vacuum degree threshold, the control system 21 closes the vacuum device 20, that is, closes the vacuum valve 10, and stops vacuuming the interlayer. At the same time, the control system 21 opens the gas supply valve 2, the nitrogen heater 5 and the air intake control valve 8. The nitrogen source 1 provides nitrogen, and the nitrogen is heated by the nitrogen heater 5 and then filled into the interlayer; set the pressure threshold of the interlayer (for example, 110KPa micro-positive pressure). When the pressure of the interlayer rises to the pressure threshold, the control system 21 further opens the automatic air outlet control valve 18, and continues to fill and exhaust nitrogen for a period of time, generally 1 to 12 hours, so that the interlayer begins to be filled with nitrogen. There is always flowing nitrogen, which replaces the original gas in the interlayer. The nitrogen temperature is controlled within the nitrogen temperature range. The temperature of the nitrogen filled into the interlayer is measured by the first temperature sensor 7 and the temperature information is transmitted to the control system. The temperature of the gas discharged from the interlayer is measured by the second temperature sensor 17. The control system 21 controls the switch of the nitrogen heater 5 according to the temperatures measured by the first temperature sensor 7 and the second temperature sensor 17, thereby controlling the nitrogen temperature in the interlayer. In the above process, the opening of the limiting valve 4 is adjusted at different stages. When the interlayer pressure does not reach the pressure threshold during the nitrogen filling stage, the limiting valve 4 opens at a large opening to maintain a large flow rate. In the stage where nitrogen filling and nitrogen exhaust are carried out simultaneously, the opening of the limiting valve 4 needs to be closed to maintain a small flow rate.

S3. The control system 21 closes the automatic gas outlet control valve 18, closes the gas supply valve 2 and the gas inlet control valve 8, and at the same time, the control system 21 starts the vacuum pump 20 to extract the nitrogen in the interlayer;

S4. Set the number of nitrogen flushing and replacement times (the number of nitrogen flushing and replacement times is generally 4 to 15 times), repeat steps S2 and S3 to the number of nitrogen flushing and replacement times, until the original gas in the interlayer is completely exhausted and all the nitrogen is extracted.

Effect Example 1

From 2002 to 2019, a company in Lanzhou carried out this test on 36 cryogenic containers of a new type of submarine with a volume of 20m ³ to 32m ^3. The effective volume of the interlayer of the vacuum multilayer insulated cryogenic container is 6 to 8m ³ ; the achieved interlayer sealing vacuum degree is 1.5×10 ^-4 Pa to 3.3×10 ^-3 Pa, and the achieved interlayer cryogenic pressure is 6×10 ^-5 Pa to 3×10 ^-4 Pa. No significant change was found in the retest of the interlayer cryogenic pressure after 4 to 14 years, as shown in Figure 5.

Effect Example 2

In November 2017, a vacuum effect demonstration was carried out in a company in Nantong: a 40-foot LNG container with an effective vacuum interlayer space of ^8.5m3 was jointly tested by the two parties. The effective vacuum time was 6 days. When the vacuum was completed, the sealing vacuum was 3.1E-3Pa, see Table 1; after the liquid nitrogen was added for thermal equilibrium, the cold vacuum was 1.8E-4Pa, see Table 2; 2 years later, in October 2019, the two parties conducted a tracking test on the interlayer vacuum, and the data is shown in Table 3; the data showed that the interlayer vacuum decreased by 2E-4Pa in 2 years, and it can be expected that the interlayer vacuum will still be at the E-3 level 20 years later.

Table 1: Sealing vacuum test table

Table 2: Initial cold vacuum test table

Table 3: Cold vacuum test table after 2 years

Effect Example 3

In February 2019, a company in Wuxi implemented a 40-foot LNG tank container with an effective vacuum interlayer space of 8.5m ^3. The effective replacement + evacuation took a total of 6 days. When sealing, the inner tank outlet temperature was 52°C, and the interlayer vacuum degree was 9.5×10 ^-4 Pa (directly measured by installing the interlayer gauge). The current national standard NB/T47059-2017 requires that the sealing vacuum degree index of the same type of product be 8×10 ^-2 Pa at room temperature. The sealing data is excellent and unique in the industry.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (8)

1. A vacuum multilayer heat insulation low temperature container interlayer nitrogen flushing replacement system is characterized in that: the device comprises a nitrogen charging device, an automatic air outlet control valve, a vacuum pumping device and a control system; the nitrogen charging device, the automatic air outlet control valve and the vacuumizing device are communicated with an interlayer of the vacuum multilayer heat insulation low-temperature container; the nitrogen charging device comprises a nitrogen source, a nitrogen heater and an air inlet control valve, wherein the nitrogen source is provided with an air supply valve, the air outlet end of the nitrogen source is connected with the air inlet end of the nitrogen heater, the air outlet end of the nitrogen heater is connected with the air inlet end of the air inlet control valve, and the air outlet end of the air inlet control valve is communicated with the interlayer; the air supply valve, the nitrogen heater, the air inlet control valve, the vacuumizing device and the automatic air outlet control valve are all in communication connection with the control system;

The nitrogen charging device also comprises a first temperature sensor and a pressure sensor, wherein the first temperature sensor is connected between the nitrogen heater and the air inlet control valve, the pressure sensor is connected between the air inlet control valve and the interlayer, and the first temperature sensor and the pressure sensor are both in communication connection with the control system;

and a second temperature sensor for detecting the temperature of the exhaust gas of the interlayer is also connected between the automatic air outlet control valve and the interlayer, and the second temperature sensor is in communication connection with the control system.

2. The vacuum multi-layer insulated cryogenic vessel sandwich nitrogen flush replacement system of claim 1, wherein: the nitrogen charging device also comprises a pressure limiting valve and a flow limiting valve, wherein the pressure limiting valve and the flow limiting valve are sequentially connected between the air supply valve and the nitrogen heater, and the flow limiting valve is in communication connection with the control system.

3. The vacuum multi-layer insulated cryogenic vessel sandwich nitrogen flush replacement system of claim 1, wherein: the nitrogen charging device also comprises a safety valve which is connected between the nitrogen heater and the first temperature sensor.

4. The vacuum multi-layer insulated cryogenic vessel sandwich nitrogen flush replacement system of claim 1, wherein: the vacuum device is provided with a vacuum valve for controlling the switch of the vacuum device, the vacuum device is connected between the air inlet control valve and the pressure sensor, and then the vacuum device and the nitrogen charging device are connected at the same connecting port of the interlayer, and the vacuum valve is in communication connection with the control system.

5. The vacuum multi-layer insulated cryogenic vessel sandwich nitrogen flush replacement system of claim 4, wherein: the vacuum pumping device also comprises an interlayer evacuating valve which is connected between the pressure sensor and the interlayer.

6. The vacuum multi-layer insulated cryogenic vessel sandwich nitrogen flush replacement system of claim 4, wherein: the vacuumizing device also comprises a vacuum gauge pipe for detecting the vacuum degree of the interlayer, wherein the vacuum gauge pipe is connected between the air inlet control valve and the pressure sensor, and the vacuum gauge pipe is in communication connection with the control system.

7. A nitrogen flushing method based on the vacuum multi-layer heat-insulating low-temperature container interlayer nitrogen flushing displacement system as claimed in claim 1, which is characterized in that: which comprises the following steps:

S1, setting a vacuum degree threshold value, and starting a vacuum pumping device by a control system to pump down the interlayer;

S2, when the vacuum degree of the interlayer is lower than a vacuum degree threshold value, the control system closes the vacuumizing device, vacuumizing the interlayer is stopped, meanwhile, the control system opens the air supply valve, the nitrogen heater and the air inlet control valve, the nitrogen source supplies nitrogen, the nitrogen is heated and then is filled into the interlayer, and when the pressure of the interlayer reaches 110KPa, the control system further opens the automatic air outlet control valve, and continuously fills and discharges nitrogen, so that the original gas in the interlayer is replaced;

S3, the control system closes the automatic air outlet control valve, closes the air supply valve and the air inlet control valve, and simultaneously starts the vacuumizing device to pump out nitrogen in the interlayer;

S4, repeating the steps S2 and S3 for a plurality of times until the raw gas in the interlayer is completely discharged and the nitrogen is completely extracted.

8. The nitrogen flush replacement method of a vacuum multi-layer insulated cryogenic vessel sandwich nitrogen flush replacement system of claim 7, wherein: the step S2 further comprises setting a nitrogen temperature range, controlling the nitrogen temperature within the nitrogen temperature range, measuring the temperature of the nitrogen filled in the interlayer by the first temperature sensor, transmitting temperature information to the control system, and controlling the switch of the nitrogen heater by the control system according to the temperature measured by the first temperature sensor.