Nitrogen circulation recovery system for rewarming of extremely low temperature refrigeration equipment and rewarming method

Abstract

The invention relates to the technical field of extremely-low-temperature refrigeration, and provides an extremely-low-temperature refrigeration equipment rewarming nitrogen circulation recovery system which comprises a gas storage tank, a gas outlet of the gas storage tank is connected with a gas outlet valve, and a gas inlet of the gas storage tank is connected with a gas inlet valve; the circulating pump is connected with the air inlet valve of the air storage tank; an impurity removal coil pipe is arranged in the cold trap; the air outlet valve is connected with the air storage tank; an air supply pipe and a filling pipe; the heating piece is connected to the outer wall of the filling pipe in a sleeving manner; one end of the air return pipe is connected with the air supply pipe, and the other end is connected with an exhaust port of a vacuum cover of the extremely-low-temperature refrigeration equipment through a first air return valve; the air return pipe is further connected with a second air return valve. Therefore, the heating piece is arranged on the filling pipe to increase the temperature of the nitrogen, and the rewarming process of the extremely-low-temperature refrigeration equipment is accelerated. Compared with the prior art, the rewarming speed is increased by at least three times. And the circulating pump and the gas storage tank are arranged, so that nitrogen can be recycled after rewarming is finished, and waste of high-purity nitrogen is reduced. The invention further provides a rewarming method.

Description

Technical Field

[0001] This invention belongs to the field of cryogenic refrigeration technology, and particularly relates to a nitrogen circulation and recovery system and a rewarming method for cryogenic refrigeration equipment. Background Technology

[0002] Cryogenic refrigerators have the capability to generate temperatures in the mK range. Their structure is located within a vacuum chamber to isolate heat loss caused by convective heat transfer from the external environment. After cooling is complete, the equipment needs to be rewarmed. Because the system is under vacuum, the natural heating rate is slow; therefore, it is usually necessary to inject a certain amount of room temperature gas to enhance heat exchange between the system and the outside environment, thereby accelerating the rewarming process.

[0003] The gas used for reheating is typically a high-purity gas with stable physical and chemical properties (such as nitrogen) to prevent reactions between the gas and internal system components or the formation of impurities such as condensate during the reheating process. Currently, when nitrogen is used for reheating, the reheating rate relies solely on convective heat exchange between the room-temperature nitrogen and the system, resulting in a slow reheating rate. Furthermore, after reheating, the nitrogen in the system is directly discharged, leading to a waste of high-purity nitrogen.

[0004] In conclusion, the existing technology obviously has inconveniences and defects in practical use, so it is necessary to improve it. Summary of the Invention

[0005] To address the aforementioned shortcomings, this invention provides a nitrogen circulation and recovery system for reheating in cryogenic refrigeration equipment, solving the technical problems of low heating efficiency and non-recoverable high-purity nitrogen during the reheating process.

[0006] To solve the above problems, the present invention provides a nitrogen circulation and recovery system for reheating of cryogenic refrigeration equipment, including a gas storage tank, the gas outlet of which is connected to a gas outlet valve and the gas inlet of which is connected to a gas inlet valve. A circulating pump has a pumping pipe; the pumping pipe is connected to the inlet valve of the gas storage tank; The cold trap is equipped with a purification coil inside; the purification coil is connected to the gas outlet valve of the gas storage tank. An air supply pipe is connected to the impurity removal coil of the cold trap via an air supply valve; The charging pipe has one end connected to the suction port of the circulating pump and the other end connected to the charging port of the vacuum hood of the cryogenic refrigeration equipment; the charging pipe is connected to the charging port through a charging valve. A heating element is fitted onto the outer wall of the filling tube; The return gas pipe has one end connected to the gas supply pipe and the other end connected to the exhaust port of the vacuum chamber of the cryogenic refrigeration equipment through a first return gas valve; a second return gas valve is also connected to the return gas pipe. A vacuum pump is connected to a suction pipe; the suction pipe is also connected to the return pipe, and the connection point between the two is located between the first return valve and the second return valve. A bypass pipe is provided, with one end connected to the air supply pipe and the other end connected to the air pumping pipe of the circulating pump; a bypass valve is provided on the bypass pipe.

[0007] According to the nitrogen circulation and recovery system for rewarming in cryogenic refrigeration equipment of the present invention, a rewarming coil is connected between the impurity removal coil and the gas supply valve.

[0008] According to the nitrogen circulation and recovery system for rewarming in the cryogenic refrigeration equipment of the present invention, the heating element is an electric heating wire wound around the outer wall of the filling tube.

[0009] According to the nitrogen circulation and recovery system for rewarming in cryogenic refrigeration equipment of the present invention, a vacuum gauge is installed on the vacuum hood, the extraction pipe and the storage tank respectively.

[0010] According to the cryogenic refrigeration equipment rewarming nitrogen circulation and recovery system of the present invention, the gas supply pipe is also connected to the charging pipe through a short-circuit valve; a straight pipe is connected between the charging pipe and the pumping pipe, and a straight valve is provided on the straight pipe.

[0011] According to the nitrogen circulation and recovery system for rewarming in cryogenic refrigeration equipment of the present invention, the extraction valve, charging valve, first return valve, second return valve, short-circuit valve, supply valve, outlet valve, inlet valve, bypass valve, and straight-through valve are all high-vacuum pneumatic valves.

[0012] A retemperature method based on the aforementioned nitrogen circulation and recovery system, wherein after the cryogenic refrigeration equipment has finished its refrigeration state, the following steps are executed sequentially: S1, pipeline vacuuming process; The first return valve, filling valve, outlet valve, and inlet valve are all closed; all other valves are open; the vacuum pump is started to extract the gas in the pipeline until the vacuum level reaches the predetermined value; then the extraction valve is closed. S2, filling process; The first return valve, the second return valve, the supply valve, the outlet valve, the short-circuit valve, and the straight-through valve are all in the open state, while the remaining valves are in the closed state. Nitrogen gas in the storage tank is injected into the vacuum chamber through the exhaust port and then into the pipeline through the open valve. The filling process ends when the pressure in the vacuum chamber and the storage tank is the same. After the filling process, the pressure value is less than the standard atmospheric pressure. S3, cyclic process; The filling valve, the first return valve, the second return valve, the supply valve, and the bypass valve are all in the open state, while the remaining valves are in the closed state; the circulation pump is running, and the heating element is energized; nitrogen gas circulates into the vacuum chamber through the circulation pump until the preset temperature is reached; during the circulation process, the pressure value inside the vacuum chamber does not exceed the preset value. S4, recycling process; The filling valve and the air inlet valve are in the open state, and all other valves are in the closed state; the circulation pump is running, and the heating element is not powered; the nitrogen in the vacuum chamber is recovered to the storage tank through the circulation pump; After the recycling process is completed, the filling valve and the air inlet valve are switched to the closed state.

[0013] According to the reheating method of the present invention, after the filling process in step S2 is completed, the pressure value is 500~600mBar.

[0014] According to the reheating method of the present invention, an impurity removal process is performed between the filling process in step S2 and the recycling process in step S3. In the impurity removal process, the air extraction valve, short-circuit valve, bypass valve, and straight-through valve are in the closed state, while all other valves are in the open state. The circulation pump is running, but the heating element is not powered. Nitrogen gas circulates through the impurity removal coil of the cold trap via the circulation pump, and impurity gases in the nitrogen gas are liquefied or solidified and separated from the nitrogen gas.

[0015] According to the rewarming method of the present invention, in the cyclic process of step S3, when the pressure value inside the vacuum chamber exceeds the preset value, the process switches to the impurity removal process; until the pressure value inside the vacuum chamber is lower than the predetermined value, the process switches back to the cyclic process.

[0016] In summary, the nitrogen circulation and recovery system for cryogenic refrigeration equipment of the present invention accelerates the rewarming process of the cryogenic refrigeration equipment by increasing the nitrogen temperature through the installation of a heating element on the filling pipe. Compared with existing methods, the rewarming speed is increased by at least three times. By incorporating a circulation pump and a gas storage tank, the nitrogen can be recovered and reused after rewarming, reducing the waste of high-purity nitrogen. The present invention also provides a rewarming method. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the refrigeration state of the ultra-low temperature refrigeration device of the present invention; Figure 2 This is a schematic diagram of the pipeline vacuum state of the recovery system of the present invention; Figure 3 This is a schematic diagram of the charging state of the recycling system of the present invention; Figure 4 This is a schematic diagram of the recycling system of the present invention in a cyclic state. Figure 5 This is a schematic diagram of the gas impurity removal state of the recovery system of the present invention; Figure 6 This is a schematic diagram of the cold trap cleanup state of the recovery system of the present invention; In the diagram: 1-Vacuum hood, 11-Exhaust port, 12-Filling port, 13-Vacuum gauge; 2-Vacuum pump, 21-Evacuation pipe, 22-Evacuation valve; 3-Filling pipe, 31-Heating element, 32-Filling valve; 4-Return pipe, 41-First return valve, 42-Second return valve; 5-Inlet pipe, 51-Short-circuit valve, 52-Inlet valve; 6-Storage tank, 61-Outlet valve, 62-Inlet valve; 7-Circulation pump, 71-Pump pipe, 72-Bypass pipe, 73-Bypass valve, 74-Straight pipe, 75-Straight valve; 8-Cold trap, 81-Impurity removal coil, 82-Return coil. Detailed Implementation

[0018] See Figure 1 This invention provides a nitrogen circulation and recovery system for rewarming in cryogenic refrigeration equipment, comprising: The gas storage tank 6 has an outlet connected to an outlet valve 61 and an inlet connected to an inlet valve 62; the gas storage tank 6 is used to store high-purity nitrogen.

[0019] The circulating pump 7 has a pumping pipe 71; the pumping pipe 71 is connected to the air inlet valve 62 of the air storage tank 6; The cold trap 8 is equipped with a cleaning coil 81 inside; the cleaning coil 81 is connected to the gas outlet valve 61 of the gas storage tank 6. Optionally, the cold trap 8 of the present invention is filled with liquid nitrogen, and the impurity removal coil 81 is immersed in the liquid nitrogen. Nitrogen gas in the gas storage tank 6 enters the impurity removal coil 81, and the impurity gases mixed therein are liquefied or solidified and precipitated.

[0020] The air supply pipe 5 is connected to the impurity removal coil 81 of the cold trap 8 via the air supply valve 52; Furthermore, a reheating coil 82 is connected between the impurity removal coil 81 and the air supply valve 52; as the nitrogen flow after impurity removal passes through the reheating coil 82, it exchanges heat with the outside air, and the temperature rises.

[0021] Optionally, the reheating coil 82 of the present invention can be immersed in a high-temperature liquid, such as water or oil, to promote the temperature recovery of nitrogen.

[0022] The filling pipe 3 is connected at one end to the suction port of the circulating pump 7 and at the other end to the filling port 12 of the vacuum hood 1 of the cryogenic refrigeration equipment; the filling pipe 3 is connected to the filling port 12 through the filling valve 32. Heating element 31 is sleeved on the outer wall of the filling tube 3; used to raise the temperature of nitrogen gas and promote the warming rate inside the vacuum hood 1.

[0023] Optionally, the heating element 31 can be an electric heating wire, which is wound around the outer wall of the filling tube 3.

[0024] The return gas pipe 4 is connected at one end to the supply gas pipe 5 and at the other end to the exhaust port 11 of the vacuum chamber 1 of the cryogenic refrigeration equipment through the first return gas valve 41; the return gas pipe 4 is also connected to the second return gas valve 42. Vacuum pump 2 is connected to suction pipe 21; suction pipe 21 is also connected to return pipe 4, and the connection point of the two is located between first return valve 41 and second return valve 42. A bypass pipe 72 is connected at one end to the air supply pipe 5 and at the other end to the air pumping pipe 71 of the circulating pump 7; a bypass valve 73 is provided on the bypass pipe 72. As one embodiment, the air supply pipe 5 is also connected to the filling pipe 3 via a short-circuit valve 51; a straight pipe 74 is connected between the filling pipe 3 and the pump pipe 71, and a straight pipe valve 75 is provided on the straight pipe 74; As one embodiment, the vacuum valve 22, filling valve 32, first return valve 41, second return valve 42, short-circuit valve 51, air supply valve 52, air outlet valve 61, air inlet valve 62, bypass valve 73, and straight-through valve 75 of the present invention are all high-vacuum pneumatic valves.

[0025] As one embodiment, a vacuum gauge 13 is installed on the vacuum hood 1, the extraction pipe 21 and the gas storage tank 6 respectively.

[0026] A retemperature method based on the aforementioned nitrogen circulation and recovery system, wherein after the cryogenic refrigeration equipment has finished its refrigeration state, the following steps are executed sequentially: See Figure 2 S1, pipeline vacuuming process; The first return valve 41, filling valve 32, outlet valve 61, and inlet valve 62 are all closed; all other valves are open; vacuum pump 2 is started to extract the gas in the pipeline until the vacuum level reaches the predetermined value; then the extraction valve 22 is closed. Optionally, step S1 of the present invention can be performed by detecting the vacuum level in the pipeline using the vacuum gauge 13 of the evacuation pipe 21.

[0027] See Figure 3 S2, filling process; The first return air valve 41, the second return air valve 42, the supply air valve 52, the outlet air valve 61, the short-circuit valve 51, and the straight-through valve 75 are all in the open state, while the remaining valves are in the closed state. Nitrogen gas in storage tank 6 is injected into vacuum chamber 1 through exhaust port 11, and simultaneously injected into pipeline through open valve; when the pressure in vacuum chamber 1 and storage tank 6 is the same, the filling process ends; after the filling process ends, the pressure value is less than 1 standard atmosphere. Preferably, after the filling process in step S2 of the present invention is completed, the pressure value is 500~600 mBar.

[0028] Optionally, step S2 of the present invention can be detected and determined by the vacuum gauge 13 of the vacuum hood 1 and the gas storage tank 6 to determine whether the pressure in the vacuum hood 1 and the gas storage tank 6 is the same.

[0029] During the nitrogen filling process, the nitrogen flows through the impurity removal coil 81 of the cold trap 8 to remove impurities.

[0030] See Figure 4 S3, cyclic process; The filling valve 32, the first return valve 41, the second return valve 42, the supply valve 52, and the bypass valve 73 are all in the open state, while the other valves are in the closed state; the circulation pump 7 is running, and the heating element 31 is energized; nitrogen gas circulates into the vacuum chamber 1 through the circulation pump 7 until the preset temperature is reached; during the circulation process, the pressure value inside the vacuum chamber 1 does not exceed the preset value. Optionally, the vacuum chamber 1 of the present invention is equipped with a temperature sensor for detecting the temperature of the cold plate; based on the feedback value of the vacuum gauge 13 of the vacuum chamber 1 and the temperature sensor, the pressure value inside the vacuum chamber 1 is controlled to be less than 950 mBar. When the temperature of the cold plate inside the vacuum chamber 1 is close to the ambient temperature (ambient temperature ±10℃), the cycle process ends; See Figure 5 As one embodiment, an impurity removal process is performed between the filling process in step S2 and the recycling process in step S3. In the impurity removal process, the air extraction valve 22, short-circuit valve 51, bypass valve 73, and direct-flow valve 75 are in the closed state, while all other valves are in the open state; the circulation pump 7 is running, and the heating element 31 is not powered; nitrogen gas circulates through the impurity removal coil 81 of the cold trap 8 via the circulation pump 7, and impurity gases in the nitrogen gas, such as oxygen, carbon dioxide, and water vapor, are liquefied or solidified and separated from the nitrogen gas.

[0031] Furthermore, the duration of the impurity removal process is 0.5-1.5 hours.

[0032] As one embodiment, in the S3 step, when the pressure inside the vacuum chamber 1 exceeds a preset value, the process switches to the impurity removal step to reduce the pressure inside the vacuum chamber 1. Once the pressure inside the vacuum chamber 1 drops to a predetermined value, the process switches back to the S3 step.

[0033] S4, recycling process; The filling valve 32 and the air inlet valve 62 are in the open state, and the other valves are in the closed state; the circulation pump 7 is running, and the heating element 31 is not powered; the nitrogen in the vacuum hood 1 is recovered to the gas storage tank 6 through the circulation pump 7; After the recycling process is completed, the filling valve 32 and the air inlet valve 62 are switched to the closed state; Optionally, the recovery process ends when the vacuum level of vacuum chamber 1 drops to a predetermined value.

[0034] See Figure 1 As one embodiment, when the cryogenic refrigeration equipment is in the refrigeration state, the first return valve 41 and the extraction valve 22 are in the open state, and the other valves are in the closed state; the vacuum pump 2 operates to reduce the vacuum level inside the vacuum chamber 1.

[0035] As one example, the temperature inside the cold trap 8 is low, and the long-term accumulation of separated impurities can cause pipe blockage. Therefore, it needs to be cleaned regularly (e.g., once a month).

[0036] During cleaning, the suction valve 22, the second return valve 42, and the supply valve 52 are in the open state, while the other valves are in the closed state; the vacuum pump 2 is running; the cold trap 8 is heated to vaporize and extract the impurities.

[0037] Optionally, the heating method can be to use a hot air gun to heat the outer wall of the cold trap 8, thereby raising the internal temperature.

[0038] Optionally, the present invention uses PID control to control the on / off state of each valve and execute each process; the degree of automation is high.

[0039] The gas storage tank 6 of this invention can perform at least 10 reheating cycles after being filled with nitrogen once. Gas can be replenished to the gas storage tank 6 periodically to offset losses and save gas. Compared with existing reheating methods, the reheating speed of this invention is increased by at least three times, saving reheating time and improving reheating efficiency.

[0040] In summary, this invention provides a nitrogen circulation and recovery system for the rewarming of cryogenic refrigeration equipment. By installing a heating element on the filling pipe to increase the nitrogen temperature, the rewarming process of the cryogenic refrigeration equipment is accelerated. Compared with existing methods, the rewarming speed is increased by at least three times. By incorporating a circulation pump and a gas storage tank, the nitrogen can be recovered and reused after rewarming, reducing the waste of high-purity nitrogen. This invention also provides a rewarming method.

[0041] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A nitrogen circulation and recovery system for rewarming in ultra-low temperature refrigeration equipment, characterized in that, include The gas storage tank has an outlet connected to an outlet valve and an inlet connected to an inlet valve. A circulating pump has a pumping pipe; the pumping pipe is connected to the inlet valve of the gas storage tank; The cold trap is equipped with a purification coil inside; the purification coil is connected to the gas outlet valve of the gas storage tank. An air supply pipe is connected to the impurity removal coil of the cold trap via an air supply valve; The charging pipe has one end connected to the suction port of the circulating pump and the other end connected to the charging port of the vacuum hood of the cryogenic refrigeration equipment; the charging pipe is connected to the charging port through a charging valve. A heating element is fitted onto the outer wall of the filling tube; The return gas pipe has one end connected to the gas supply pipe and the other end connected to the exhaust port of the vacuum chamber of the cryogenic refrigeration equipment through a first return gas valve; a second return gas valve is also connected to the return gas pipe. A vacuum pump is connected to a suction pipe; the suction pipe is also connected to the return pipe, and the connection point between the two is located between the first return valve and the second return valve. A bypass pipe is provided, with one end connected to the air supply pipe and the other end connected to the air pumping pipe of the circulating pump; a bypass valve is provided on the bypass pipe.

2. The nitrogen circulation and recovery system for rewarming in cryogenic refrigeration equipment as described in claim 1, characterized in that, A reheating coil is connected between the impurity removal coil and the air supply valve.

3. The nitrogen circulation and recovery system for rewarming in cryogenic refrigeration equipment as described in claim 1, characterized in that, The heating element is an electric heating wire, which is wound around the outer wall of the filling tube.

4. The nitrogen circulation and recovery system for rewarming in cryogenic refrigeration equipment as described in claim 1, characterized in that, A vacuum gauge is installed on the vacuum hood, the extraction pipe, and the gas storage tank, respectively.

5. The nitrogen circulation and recovery system for rewarming in cryogenic refrigeration equipment as described in any one of claims 1 to 4, characterized in that, The air supply pipe is also connected to the filling pipe via a short-circuit valve; a straight pipe is connected between the filling pipe and the pumping pipe, and a straight valve is provided on the straight pipe.

6. The nitrogen circulation and recovery system for rewarming in ultra-low temperature refrigeration equipment as described in claim 5, characterized in that, The air extraction valve, filling valve, first return air valve, second return air valve, short-circuit valve, air supply valve, air outlet valve, air inlet valve, bypass valve, and straight-through valve are all high-vacuum pneumatic valves.

7. A retemperature method based on the nitrogen circulation recovery system as described in claim 5, characterized in that, After the cryogenic refrigeration equipment stops refrigeration, the following steps are performed in sequence: S1, pipeline vacuuming process; The first return valve, filling valve, outlet valve, and inlet valve are all closed; all other valves are open; the vacuum pump is started to extract the gas in the pipeline until the vacuum level reaches the predetermined value; then the extraction valve is closed. S2, filling process; The first return valve, the second return valve, the supply valve, the outlet valve, the short-circuit valve, and the straight-through valve are all in the open state, while the remaining valves are in the closed state. Nitrogen gas in the storage tank is injected into the vacuum chamber through the exhaust port and then into the pipeline through the open valve. The filling process ends when the pressure in the vacuum chamber and the storage tank is the same. After the filling process, the pressure value is less than the standard atmospheric pressure. S3, cyclic process; The filling valve, the first return valve, the second return valve, the supply valve, and the bypass valve are all in the open state, while the remaining valves are in the closed state; the circulation pump is running, and the heating element is energized; nitrogen gas circulates into the vacuum chamber through the circulation pump until the preset temperature is reached; during the circulation process, the pressure value inside the vacuum chamber does not exceed the preset value. S4, recycling process; The filling valve and the air inlet valve are in the open state, and all other valves are in the closed state; the circulation pump is running, and the heating element is not powered; the nitrogen in the vacuum chamber is recovered to the storage tank through the circulation pump; After the recycling process is completed, the filling valve and air inlet valve are switched to the closed state.

8. The rewarming method as described in claim 7, characterized in that, After the filling process in step S2 is completed, the pressure value is 500~600mBar.

9. The retemperature method as described in claim 7, characterized in that, An impurity removal process is performed between the filling process in step S2 and the recycling process in step S3. In the impurity removal process, the air extraction valve, short-circuit valve, bypass valve, and straight-through valve are in the closed state, while all other valves are in the open state. The circulation pump is running, but the heating element is not powered. Nitrogen gas circulates through the impurity removal coil of the cold trap via the circulation pump, and impurity gases in the nitrogen gas are liquefied or solidified and separated from the nitrogen gas.

10. The retemperature method as described in claim 9, characterized in that, In the S3 step, when the pressure inside the vacuum chamber exceeds a preset value, the process switches to the impurity removal process; and then switches back to the cycle process when the pressure inside the vacuum chamber is lower than the preset value.

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