CN111810832A - System and method for interlayer nitrogen flushing and replacement of vacuum multi-layer adiabatic cryogenic container - Google Patents

Abstract

The invention discloses a nitrogen flushing replacement system and method for the interlayer of a vacuum multi-layer heat-insulated low-temperature container. The system includes a nitrogen charging device, an automatic gas outlet control valve, a vacuum pumping device and a control system; The vacuum devices are all communicated with the interlayer of the vacuum multilayer heat-insulated cryogenic container; the nitrogen charging device includes a nitrogen source, a nitrogen heater and an intake control valve, the nitrogen source is equipped with an air supply valve, and the outlet end of the nitrogen source is connected to the nitrogen heater. The air inlet 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 connected with the interlayer; the air supply valve, the nitrogen heater, the air inlet control valve, Both the vacuuming device and the automatic air outlet control valve are connected with the control system by communication. Adopting the technical solution involved in the present invention, the interlayer gas replacement effect is good, which helps to improve the extraction efficiency of the replacement nitrogen gas, and thus can obtain a long-lasting high-vacuum lifespan.

Description

System and method for interlayer nitrogen flushing and replacement of vacuum multi-layer adiabatic cryogenic container

technical field

The invention belongs to the technical field of vacuum evacuation of the interlayer of a vacuum multi-layer adiabatic low temperature container, and in particular relates to a vacuum multi-layer adiabatic low temperature container interlayer nitrogen flushing replacement system and method capable of completely replacing the moisture and other non-condensable gas molecules in the interlayer, which is used for evacuation Before replacing the gas in the interlayer of the cryogenic vessel.

Background technique

As the application of refrigerated liquefied gas becomes wider and wider, the requirements for the thermal insulation performance of devices for storing and transporting refrigerated liquefied gas are also getting higher and higher, especially for the storage and transportation of liquid oxygen, liquid nitrogen, liquid hydrogen, liquid argon, LNG and other deep For containers of cold and cryogenic liquids, generally only a high-vacuum multi-layer thermal insulation structure can be used to meet the thermal insulation requirements. Such containers have extremely high requirements on the interlayer vacuum, and the cold working interlayer vacuum in the entire interlayer vacuum life cycle of the container (5 years) needs to be better than 0.03Pa (absolute pressure). It can be seen that the interlayer vacuum is one of the important indicators affecting the thermal insulation performance of cryogenic vessels, and is an important technical link in the manufacturing and maintenance of vacuum multilayer thermal insulating vessels.

In the case of structural solidification, the interlayer vacuum is the only indicator that affects the thermal insulation performance of the vacuum multi-layer thermally insulated cryogenic vessel. The traditional interlayer vacuuming process has the defects of high energy consumption, long time consumption, high labor consumption, and short life of the obtained vacuum; Layers or even hundreds of layers of film materials are stacked and wound on the inner container, which has the characteristics of small thermal conductivity, many layers, large surface area, and tight arrangement. , the problem of difficult desorption of adsorbed gas.

In view of the above problems, patent CN101021209A discloses a vacuuming method and a device thereof, including: a first gas conveying device, which has an air outlet; a first gas heater, whose inlet is communicated with the air outlet of the first gas conveying device , its outlet is communicated with the air inlet of the inner cylinder; the vacuuming unit is communicated with the interlayer; the second gas conveying device has an air outlet; the second gas heater, its inlet is connected with the second gas conveying The air outlet of the device is communicated, and the outlet is communicated with the interlayer.

Patent No. CN102913749A discloses a vacuuming system and method for a large-volume low-temperature insulating container, including an air supply device, a vacuuming device and a heating device; the heating device includes an outer tank heating device and an inner tank heating device; The tank, the inner tank and the interlayer formed by the outer tank and the inner tank; the heating device of the outer tank is arranged outside the outer tank of the container to be evacuated and insulated; the heating device of the inner tank is arranged inside the inner tank of the container to be evacuated and insulated; the air supply device The inner tank and the interlayer of the to-be-evacuated and insulated container are respectively communicated through the pipeline;

The solutions involved in the above-mentioned patents all need to flush the gas in the interlayer through a gas supply device (or a gas delivery device), so as to replace the gas that is not easily detached in the interlayer, and then use a vacuum device to extract the flushing gas. The interlayer is in a vacuum state, thereby improving thermal insulation properties. However, in the above two technical solutions, the interlayer replacement adopts the closed inflation method, which is prone to overcharge or undercharge during actual operation.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problems of overcharging and undercharging when the interlayer of the vacuum multi-layer thermal insulation low temperature container is replaced by nitrogen gas in the prior art, resulting in poor vacuum degree of the interlayer and poor thermal insulation performance of the container, and proposes a vacuum multilayer A system and method for flushing and replacing interlayer nitrogen in adiabatic cryogenic vessels.

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

The invention relates to a vacuum multi-layer thermal insulation low temperature container interlayer nitrogen flushing and replacement system, which comprises 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 Both are connected with the interlayer of the vacuum multi-layer adiabatic low temperature container; the nitrogen filling device includes a nitrogen source, a nitrogen heater and an inlet control valve, the nitrogen source is equipped with a gas supply valve, and the outlet end of the nitrogen source is connected with the inlet of the nitrogen heater. The air end is connected, the air outlet end of the nitrogen heater is connected with the air inlet end of the air intake control valve, and the air outlet end of the air intake control valve is connected with the interlayer; the air supply valve, the nitrogen heater, the air intake control valve, the vacuum pump Both the device and the automatic air outlet control valve are connected in communication with the control system.

Preferably, the nitrogen charging device further comprises a first temperature sensor and a pressure sensor, the first temperature sensor is connected between the nitrogen heater and the intake control valve, the pressure sensor is connected between the intake control valve and the interlayer, and the first temperature sensor is connected between the nitrogen heater and the intake control valve, and the pressure sensor is connected between the intake control valve and the interlayer. A temperature sensor and pressure sensor are both connected in communication with the control system.

Preferably, the nitrogen charging device further includes 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 connected in communication with the control system.

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

Preferably, the vacuuming device is equipped with a vacuuming valve for controlling its opening and closing, and the vacuuming device is connected between the intake control valve and the pressure sensor, so that the vacuuming device and the nitrogen filling device are connected to the same one of the interlayer. At the connection port, the vacuum pumping valve is communicated with the control system.

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

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

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

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

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

S2. When the vacuum degree of the interlayer reaches lower than the vacuum degree threshold, the control system closes the vacuuming device and stops the vacuuming of the interlayer. At the same time, the control system opens the gas supply valve, nitrogen heater and intake control valve, and the nitrogen source provides nitrogen, After the nitrogen is heated, it is 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 charge and discharge nitrogen, and then replace the original gas in the interlayer;

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

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

Preferably, the step S2 also includes setting a nitrogen temperature range, the nitrogen temperature is controlled within the nitrogen temperature range, the temperature of the nitrogen charged into the interlayer is measured by the first temperature sensor and the temperature information is transmitted to the control system, and the control system is based on The temperature measured by the first temperature sensor controls the switching of the nitrogen heater.

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

The nitrogen flushing and replacement system for the interlayer of the vacuum multi-layer adiabatic low-temperature container involved in the present invention includes a nitrogen filling device, an automatic gas outlet control valve and a vacuum pumping device. The pressure is controlled at a slightly positive pressure, and there will be no overcharging or undercharging. When the interlayer space is evacuated, a negative pressure is formed between the layers of the insulating material, which can desorb the vaporized moisture and non-condensable gas adsorbed by the deep insulating material. The interlayer is flushed by the flowing hot nitrogen gas, which is conducive to the desorption of moisture and non-condensable gas components from the interlayer material and flushing out of the interlayer, so that the replacement effect is complete, and the vacuum degree and thermal insulation of the cryogenic container are improved.

Description of drawings

Fig. 1 is the structure diagram of the nitrogen flushing replacement system of the vacuum multilayer thermal insulation cryocontainer interlayer in the embodiment 1;

Fig. 2 is the structural diagram of the nitrogen flushing replacement system of the vacuum multilayer thermal insulation cryocontainer interlayer in the second embodiment;

Fig. 3 is the structural diagram of the inner container heating device in the second embodiment;

Fig. 4 is the structural diagram of the outer container heating device in the second embodiment;

Fig. 5 is a graph showing the variation of the vacuum degree of the interlayer of the cryogenic vessel with time after flushing the interlayer and evacuating the interlayer according to the present invention.

Among them: 1. Nitrogen source; 2. Air supply valve; 3. Pressure limiting valve; 4. Current limiting valve; 5. Nitrogen heater; 6. Safety valve; 7. First temperature sensor; 8. Intake control valve; 9. Vacuum gauge; 10. Evacuation valve; 11. Pressure sensor; 12. Interlayer evacuation 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, vacuuming device; 21, control system; 22, first circulation fan; 23, first gas heater; 24, inner container inlet valve; 25. Outlet valve of inner container; 26. Drying room; 27. Second circulating 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 described in further detail below with reference to the embodiments and the accompanying 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.

Example 1

This embodiment relates to a vacuum multi-layer thermal insulation cryogenic container interlayer nitrogen flushing and replacement system, which is used to evacuate the interlayer of the vacuum multi-layer thermal insulation low temperature container. The vacuum multi-layer thermal insulation low temperature container includes an outer container 15 and an inner container 16. The outer container An interlayer is formed between 15 and the inner container 16, and the outer periphery of the inner container 16 is provided with a thermal insulation layer 13. The thermal insulation layer 13 is made of dozens or even hundreds of layers of film materials stacked and wound on the inner container 7, which has a small thermal conductivity, The number of layers and other characteristics make the thermal insulation performance of the vacuum multi-layer thermal insulation cryogenic container better.

Referring to Figure 1, the above-mentioned vacuum multi-layer adiabatic low temperature container interlayer nitrogen flushing replacement system includes a nitrogen filling device, an automatic gas outlet control valve, a vacuum pumping device and a control system. The interlayer communication of the multi-layer thermally insulated cryogenic vessel.

The nitrogen filling device includes 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 intake control valve 8 and a pressure sensor 11. The nitrogen source 1 is equipped with There is 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, and the pressure limiting valve 3 can be used. The nitrogen pressure is limited to ≤0.2MPa, and the valve opening of the restrictor valve 4 can be adjusted according to the size of the pumped space to realize the function of adjusting the gas flow. The outlet end of the nitrogen heater 5 is connected to the inlet end of the intake control valve 8 , the first temperature sensor 7 is connected between the nitrogen heater and the intake 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 there is a safety problem such as blockage of the nitrogen charging device, the safety valve 6 is automatically opened to release the nitrogen in the nitrogen charging device; the outlet end of the intake control valve 8 is connected to the interlayer, and the pressure sensor 11 is connected to the intake control valve 8 Between the interlayer and the interlayer, it is used to measure the gas pressure of the output nitrogen.

The above-mentioned first temperature sensor 7 and pressure sensor 11 are all connected to the control system 21 in communication, and the measured nitrogen output temperature and air pressure value are transmitted to the control system 21; the above-mentioned gas supply valve 2, pressure limiting valve 3, flow limiting valve 4, The nitrogen heater 5, the safety valve 6 and the intake control valve 7 are all connected in communication with the control system 21, and the control system 21 controls the gas supply valve 2, the nitrogen heater 5 and the intake through the measured values of the first temperature sensor 7 and the pressure sensor 11. The on/off state of the gas control valve 7 is adjusted through the control system 21 to adjust the current limiting value of the limiting valve 4 .

The vacuuming device 20 is equipped with a vacuuming valve 10 for controlling its switch, and the vacuuming device is connected between the intake control valve 8 and the pressure sensor 11, so that the vacuuming device 20 and the nitrogen filling device are connected to the same connection of the interlayer. At the mouth, the vacuum valve 10 is connected in communication with the control system 21, and the switch state of the vacuum valve 10 is controlled by the control system 21; the vacuum device 20 also includes an interlayer vacuum valve 12, which is connected between the pressure sensor 11 and the interlayer. In between, the interlayer evacuation valves are all connected in communication with the control system; the evacuation device 21 also includes a vacuum gauge 9 for detecting the vacuum degree of the interlayer, and the vacuum gauge 9 is connected between the intake control valve 8 and the pressure sensor 11. The tube 9 is connected in communication with the control system 21, and the detected vacuum degree is transmitted to the control system 21 for display.

A second temperature sensor 17 for detecting the temperature of the gas discharged from the interlayer 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 connected in communication with the control system 21, and the second temperature sensor 17 measures The temperature of the obtained gas discharged from the interlayer is transmitted to the control system 21 for display, and the automatic gas outlet control valve 18 controls the gas pressure value when the gas is discharged through the control system 21 .

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

S1. use the control system 21 to set the vacuum degree threshold (the value range of the vacuum degree threshold is 10Pa～300Pa), the control system 21 starts the vacuum device 20, specifically opens the vacuum valve 10 and the interlayer vacuum valve 12, and performs the interlayer Evacuation, the vacuum degree is detected by the vacuum gauge 9 during the evacuation process;

S2. After the vacuum degree of the interlayer is lower than the vacuum degree threshold, the control system 21 closes the vacuuming device 20, that is, closes the vacuum valve 10, and stops the vacuuming of the interlayer. Meanwhile, the nitrogen temperature range (the nitrogen temperature range) is set by the control system 21. 100 ° C ~ 250 ° C), the control system 21 opens the gas supply valve 2, the nitrogen heater 5 and the intake control valve 8, the nitrogen source 1 provides nitrogen, and the nitrogen is heated by the nitrogen heater 5 and then charged into the interlayer; set the interlayer When the interlayer pressure rises and reaches the pressure threshold, the control system 21 further opens the automatic gas outlet control valve 18, and continues to charge and discharge nitrogen for a period of time, usually 1 to 12 hours, so that the There is always flowing nitrogen in the interlayer, and then the original gas in the interlayer is replaced. The nitrogen temperature is controlled within the nitrogen temperature range. The temperature of the nitrogen charged into the interlayer is measured by the first temperature sensor 7, and the temperature information is transmitted to the control system, and discharged from the interlayer. The temperature of the gas is measured by the second temperature sensor 17, and the control system 21 controls the switch of the nitrogen heater 5 according to the temperature measured by the first temperature sensor 7 and the second temperature sensor 17, and then controls the nitrogen temperature in the interlayer; in the above process, different stages Adjust the different opening degrees of the restrictor valve 4. When the interlayer pressure does not reach the pressure threshold during the nitrogen charging stage, the restrictor valve 4 opens a large opening to maintain a large flow; in the phase of nitrogen charging and nitrogen exhausting, it is necessary to close the small limit Flow valve 4 is opened to maintain a small flow.

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, at the same time, the control system 21 starts the vacuum device 20 to extract the nitrogen in the interlayer;

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

Embodiment 2:

Referring to FIG. 2 , compared with the first embodiment, the vacuum multi-layer thermal insulation cryogenic container interlayer nitrogen flushing replacement system involved in this embodiment has an inner container heating device 19 and an outer container heating device 14 added.

In this embodiment, the structures of the nitrogen filling device, the automatic gas outlet control valve 18, the vacuum pumping device 20 and the control system 21, as well as the connection relationship with the vacuum multilayer adiabatic cryogenic container are the same as those in the first embodiment, and will not be described in this embodiment; The inner container heating device 19 can provide circulating clean air or nitrogen gas from room temperature to 300°C, and is controlled by the control system 21 to achieve a cyclic and stable heating condition, thereby heating the inner container; the outer container heating device 14 It can accommodate the evacuated container, can provide circulating clean air from room temperature to 250 ℃, and is controlled by the control system, which can realize the circulating and stable heating condition, and then heat the outer container.

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

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

The steps of flushing the interlayer by using the vacuum multi-layer adiabatic cryogenic container interlayer nitrogen flushing replacement system involved in this 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℃), and open the inner container heating device 19 to the content The temperature of the inner circulation gas is controlled within the temperature range of the inner circulation heating; the outer container heating device 14 is turned on to circulate and heat the outer container, and the temperature of the outer circulation gas is controlled within the temperature range of the outer circulation heating.

S1. Use the control system to set the upper limit of the heating temperature of the inner circulation (the upper limit of the heating temperature of the inner circulation is 300°C), the lower limit of the heating of the inner circulation (the lower limit of the heating of the inner circulation is 100°C), and the upper limit of the heating temperature of the outer circulation (the upper limit of the heating temperature of external circulation is 200℃), the lower limit of heating of external circulation (the lower limit of heating of external circulation is 100℃), and the threshold of vacuum degree (the range of vacuum degree threshold is 10Pa～300Pa), when the inner container When the outlet air temperature reaches the lower limit value of the inner circulation heating, the control system 21 starts the vacuuming device 20, specifically opens the vacuuming valve 10 and the interlayer vacuuming valve 12, and evacuates the interlayer, and the vacuum gauge is detected by the vacuum gauge 9 during the vacuuming process. In the process of the vacuuming device 20, when the temperature of the gas discharged from the exhaust port of the inner container reaches the upper limit value of the heating temperature of the inner circulation, the heating of the inner drying gas heater is stopped. When the temperature of the gas discharged from the exhaust port of the inner container When it is lower than the lower limit value of the inner circulation heating, the inner drying gas heater starts to heat, so that the temperature of the discharged gas is maintained between the lower limit value of the inner circulation heating temperature and the upper limit value of the inner circulation heating temperature. When the temperature reaches the upper limit of the heating temperature of the external circulation, the external drying gas heater stops heating. When the gas temperature in the drying room is lower than the lower limit of the external circulation heating, the external drying gas heater starts to heat, so as to make the drying process. The room gas temperature is maintained between the lower limit value of external circulation heating and the upper limit value of external circulation heating temperature;

S2. Use the control system to set the nitrogen temperature range (the nitrogen temperature range is 100°C to 250°C). When the vacuum degree of the interlayer reaches the vacuum degree threshold, the control system 21 closes the vacuum pumping device 20, that is, closes the vacuum pumping valve 10, and stops the The interlayer is evacuated, and at the same time, the control system 21 opens the gas supply valve 2, the nitrogen heater 5 and the intake control valve 8, the nitrogen source 1 provides nitrogen, and the nitrogen is heated by the nitrogen heater 5 and then charged into the interlayer; set the pressure of the interlayer Threshold value (such as 110KPa slight positive pressure), when the interlayer pressure rises to reach the pressure threshold, the control system 21 further opens the automatic gas outlet control valve 18, and continues to charge and discharge nitrogen for a period of time, usually 1 to 12 hours, so that the interlayer There is always flowing nitrogen, and then the original gas in the interlayer is replaced. The nitrogen temperature is controlled within the nitrogen temperature range. The temperature of the nitrogen charged into the interlayer is measured by the first temperature sensor 7 and the temperature information is transmitted to the control system. The gas discharged from the interlayer The temperature is measured by the second temperature sensor 17, and the control system 21 controls the switch of the nitrogen heater 5 according to the temperature measured by the first temperature sensor 7 and the second temperature sensor 17, and then controls the nitrogen temperature in the interlayer; in the above process, the adjustment limit at different stages is adjusted. Different openings of flow valve 4, when the interlayer pressure does not reach the pressure threshold in the nitrogen charging stage, the restrictor valve 4 is opened to a large opening to maintain a large flow; in the stage of nitrogen charging and nitrogen exhausting, the flow restrictor valve needs to be closed. 4 degrees of opening to maintain a small flow.

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, at the same time, the control system 21 starts the vacuum device 20 to extract the nitrogen in the interlayer;

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

Effect Example 1

From 2002 to 2019, a company in Lanzhou implemented 36 cryogenic vessels for a new type of submarine of 20m ³ ~ 32m ³ . The effective volume of the interlayer of the vacuum multi-layer thermal insulation low temperature container is 6～8m ³ ; the realized interlayer sealing vacuum degree is 1.5×10 ^-4 Pa～3.3×10 ^-3 Pa, and the realized interlayer low temperature pressure is 6×10 ^-5 Pa～3 ×10 ^-4 Pa. After 4 to 14 years, there was no obvious change in the interlayer low temperature pressure, as shown in Figure 5.

Effect Example 2

In November 2017, the evacuation effect was demonstrated in a company in Nantong: a 40-foot LNG container with a vacuum interlayer effective space of 8.5m ³ , the two parties conducted joint tests, and the effective evacuation time was 6 days. At the end of the evacuation, the sealing vacuum degree was 3.1E- 3Pa, see Table 1; after adding liquid nitrogen thermal balance, the cold state vacuum degree is 1.8E-4Pa, see Table 2; 2 years later, in October 2019, the two sides conducted the interlayer vacuum degree tracking test, and the data is shown in Table 3; the data shows that The interlayer vacuum degree decreases by 2E-4Pa in 2 years, and it can be expected that the interlayer vacuum will still be in the order of E-3 after 20 years.

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

1. The utility model provides a vacuum multilayer thermal insulation cryogenic container intermediate layer nitrogen gas washes replacement system which characterized in that: the device 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 all communicated with an interlayer of the vacuum multi-layer 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.

2. The nitrogen flushing and replacing system for the vacuum multilayer heat-insulating cryogenic container interlayer of claim 1 is characterized in that: the nitrogen charging device further comprises a first temperature sensor and a pressure sensor, 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.

3. The nitrogen flushing and replacing system for the vacuum multilayer heat-insulating cryogenic container interlayer as claimed in claim 2, 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 gas supply valve and the nitrogen heater, and the flow limiting valve is in communication connection with the control system.

4. The nitrogen flushing and replacing system for the vacuum multilayer heat-insulating cryogenic container interlayer as claimed in claim 2, wherein: the nitrogen charging device further comprises a safety valve, and the safety valve is connected between the nitrogen heater and the first temperature sensor.

5. The nitrogen flushing and replacing system for the vacuum multilayer heat-insulating cryogenic container interlayer as claimed in claim 2, wherein: the vacuumizing device is provided with a vacuumizing valve for controlling the opening and closing of the vacuumizing device, the vacuumizing device is connected between the air inlet control valve and the pressure sensor, the vacuumizing device and the nitrogen filling device are further connected to the same connecting port of the interlayer, and the vacuumizing valve is in communication connection with the control system.

6. The nitrogen flushing and replacing system for the vacuum multilayer heat-insulating cryogenic container interlayer of claim 5 is characterized in that: the vacuum pumping device further comprises an interlayer evacuating valve, and the interlayer evacuating valve is connected between the pressure sensor and the interlayer.

7. The nitrogen flushing and replacing system for the vacuum multilayer heat-insulating cryogenic container interlayer of claim 5 is characterized in that: the vacuum pumping device further comprises a vacuum gauge pipe used for detecting the vacuum degree of the interlayer, 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.

8. The nitrogen flushing and replacing system for the vacuum multilayer heat-insulating cryogenic container interlayer of claim 1 is characterized in that: and a second temperature sensor for detecting the temperature of the gas discharged from the interlayer is also connected between the automatic gas outlet control valve and the interlayer, and the second temperature sensor is in communication connection with a control system.

9. A nitrogen flushing method based on the vacuum multilayer heat insulation cryogenic container interlayer nitrogen flushing replacement system of claim 1, characterized in that: which comprises the following steps:

s1, setting a vacuum degree threshold value, and starting a vacuumizing device by a control system to vacuumize an 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 of 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 provides nitrogen, the nitrogen is heated and then filled into the interlayer, when the pressure of the interlayer reaches 110KPa, the control system further opens the automatic air outlet control valve, the nitrogen is continuously filled and exhausted, and then 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 original gas in the interlayer is removed completely and the nitrogen is completely pumped out.

10. The nitrogen flushing and replacing method based on the vacuum multilayer heat-insulation cryogenic container interlayer nitrogen flushing and replacing system according to claim 9, characterized in that: the step S2 further includes setting a nitrogen temperature range, controlling the nitrogen temperature within the nitrogen temperature range, measuring the temperature of the nitrogen filled into the interlayer by the first temperature sensor, transmitting the temperature information to the control system, and controlling the nitrogen heater to be turned on or off by the control system according to the temperature measured by the first temperature sensor.

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