Helium liquefaction low-temperature circulating system
By adopting mechanical low-temperature pre-cooling cycle and oil-free suspension centrifugal compressor in the helium liquefaction circulation system, the complex preparation of liquid nitrogen and oil pollution in traditional systems are solved, and an efficient and economical helium liquefaction cycle is achieved.
Patent Information
- Application Number
- CN202421303949.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-07
- Publication Date
- 2025-02-18
- Estimated Expiration
- 2034-06-07
AI Technical Summary
The traditional helium liquefaction circulation system has problems such as complex liquid nitrogen preparation process, low liquefaction rate, poor economy, and the need to spray a large amount of oil into the screw compressor, resulting in oil pollution and freezing.
The mechanical low-temperature pre-cooling circulation system is used to replace traditional liquid nitrogen pre-cooling, and the oil-free suspension centrifugal compressor is used, and the combination of multi-stage heat exchanger and turbine expander is achieved to achieve efficient helium liquefaction cycle.
It improves system efficiency and economy, avoids oil pollution and freezing problems, and mechanical low-temperature pre-cooling circulating working fluids are easy to obtain, cheap and pollution-free.
Smart Images
Figure CN222504672U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of low-temperature refrigeration, in particular to a helium liquefaction low-temperature circulation system. Background Art
[0002] The traditional helium liquefaction cycle is basically based on the Collins cycle. Helium at room temperature is compressed into high-pressure helium by a compressor, and liquid nitrogen is used for pre-cooling at the first cooling stage. After entering the second cooling stage, part of it enters the two-stage turbine expander for adiabatic expansion, and after cooling and reducing pressure, it flows back into the low-temperature helium to cool the high-pressure helium. The other part enters the multi-stage heat exchanger for heat exchange, and finally enters the throttle valve for throttling and liquefaction.
[0003] In this process, liquid nitrogen pre-cooling is used in the first cooling stage with the highest temperature in order to improve the liquefaction coefficient of the cycle. However, traditional liquid nitrogen preparation utilizes gas separation technology, including compression, cooling, drying and separation. The preparation process is complicated and the liquefaction rate is low. The use of liquid nitrogen pre-cooling will reduce the economy of the circulation system.
[0004] Screw compressors are often used in helium liquefaction systems because of their simple and compact structure, few wearing parts, long maintenance-free cycle, high volumetric efficiency, and stepless flow adjustment. In order to obtain higher thermodynamic efficiency, screw compressors use a large amount of oil injection to absorb compression heat and control the temperature rise of the compression process at a relatively low level. Therefore, the system requires precise oil and gas separation technology and supporting complex oil separation, cooling, and filtration equipment. If the oil removal is not precise enough, it may cause oil pollution, oil freezing, and other disasters at low temperatures.
[0005] The traditional helium liquefaction process usually adopts room temperature compression, because helium is difficult to be compressed at room temperature, has a high adiabatic index and a small specific heat capacity. It is easy to generate higher compression heat during the room temperature compression process, causing a large compression temperature rise, consuming more compression work, and resulting in reduced system efficiency. Summary of the invention
[0006] In view of the defects of the prior art, a helium liquefaction cryogenic circulation system is provided which is economical, energy-saving, highly efficient and oil-free.
[0007] In order to achieve the above purpose, the utility model adopts the following technical solutions:
[0008] A helium liquefaction cryogenic circulation system, characterized in that it comprises a helium liquefaction circulation system and a mechanical cryogenic precooling circulation system; the mechanical cryogenic precooling circulation system provides precooling for the helium liquefaction circulation system; the helium liquefaction circulation system comprises a first electromagnetic three-way valve, a helium liquefaction cryogenic compressor unit, a second electromagnetic three-way valve, an expansion pipeline throttle valve, a first turbine expander, a second turbine expander, a third electromagnetic three-way valve, a helium throttle valve, a liquid helium dewar, a liquid storage tank, a gate valve, a heat exchanger, a heat exchanger assembly, and a fourth electromagnetic three-way valve; the heat exchanger The components include a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a fifth heat exchanger, a sixth heat exchanger, and a seventh heat exchanger, which can be increased or decreased according to the scale of the system, and each stage of the heat exchanger is connected in sequence; the first turbine expander and the second turbine expander are connected in sequence to form a two-stage turbine expander; the helium liquefaction cryogenic compressor unit includes a first cryogenic compressor, an intermediate heat exchanger, and a second cryogenic compressor; the mechanical cryogenic precooling circulation system includes a mechanical cryogenic compressor, an aftercooler, a turbine expander, and a regenerator.
[0009] In some preferred embodiments, the high-pressure helium at the outlet of the helium liquefaction cryogenic compressor unit is precooled by the mechanical cryogenic precooling cycle of the second heat exchanger in the heat exchanger assembly and heat exchanged by the third heat exchanger, and then enters the second electromagnetic three-way valve to be divided into two parts. One part enters the fourth-stage heat exchanger in the heat exchanger assembly and is cooled by the reflux cold helium, and then is throttled by the helium throttle valve to produce a saturated gas-liquid mixture of helium, and enters the liquid helium dewar. The liquid helium produced by the liquid helium dewar enters the liquid storage tank for storage, and the gas produced by the liquid helium dewar is merged with the other part of the cold helium that enters the second-stage turbine expander through adiabatic expansion and refrigeration along the reflux pipeline at the third electromagnetic three-way valve, refluxes to the first electromagnetic three-way valve and merges with the helium source that has been precooled by the mechanical cryogenic precooling cycle to enter the helium liquefaction cryogenic compressor unit, completing the entire helium liquefaction cycle.
[0010] Preferably, the helium source is purified helium.
[0011] In some preferred embodiments, the high-pressure gas at the outlet of the mechanical cryogenic compressor enters the aftercooler for cooling, the cooled gas enters the compression end of the turbine expander to increase the pressure, then enters the regenerator for heat exchange with the reflux gas, and then enters the expansion end of the turbine expander for adiabatic expansion refrigeration, the low-temperature gas coming out of the expansion end of the turbine expander is divided into two parts by the fourth electromagnetic three-way valve, one part is the helium source of the helium liquefaction circulation system that is pre-cooled by the first heat exchanger, and the other part is the intermediate heat exchange of the helium liquefaction cryogenic compressor unit in the helium liquefaction circulation system, and the inlet and outlet pipelines of the helium liquefaction cryogenic compressor unit are pre-cooled by the second heat exchanger, the pre-cooled gas converges, passes through the regenerator for heat exchange, and finally enters the mechanical cryogenic compressor, completing the entire mechanical cryogenic precooling cycle.
[0012] In some preferred embodiments, the first electromagnetic three-way valve, the helium liquefaction cryogenic compressor unit, the second electromagnetic three-way valve, the expansion pipeline throttle valve, the first turbine expander, the second turbine expander, the third electromagnetic three-way valve, the helium throttle valve, the heat exchanger assembly, the turbine expander, the regenerator, and the fourth electromagnetic three-way valve are all fixed in the vacuum cold tank.
[0013] In some preferred embodiments, the helium circulation cryogenic compressor unit is an oil-free gas-suspended centrifugal compressor, which is supported by an air-suspended bearing or a magnetic hybrid bearing. Its compression is low-temperature compression. The helium circulation cryogenic compressor unit uses 1-4 centrifugal compressors in series to achieve 1-10 stages of compression. The compressor stages are pre-cooled by a mechanical low-temperature pre-cooling cycle. The compressor inlet temperature is between 10K and 250K, and the working fluid used is helium.
[0014] In some preferred embodiments, the mechanical low-temperature compressor is an oil-free air-suspended centrifugal compressor, which is supported by air-suspended bearings or magnetic hybrid bearings. The compression is room temperature compression, and the compressor inlet temperature is between 230K and 340K.
[0015] In some preferred embodiments, the working fluid of the mechanical low-temperature pre-cooling circulation system is air, nitrogen, neon, argon and helium.
[0016] The advantages of the utility model using the above technical solution are:
[0017] (1) The utility model changes the traditional liquid nitrogen pre-cooling into mechanical low-temperature pre-cooling cycle pre-cooling, so that the two parts of helium entering the helium liquefaction cryogenic compressor unit are pre-cooled by the mechanical low-temperature pre-cooling cycle, and the room temperature helium is converted into low-temperature helium. The low-temperature compression reduces the compression work and effectively improves the system efficiency.
[0018] (2) The utility model adopts a mechanical low-temperature precooling cycle to precool the helium liquefaction system. Compared with liquid nitrogen precooling, the working fluids used in the mechanical low-temperature precooling cycle are air, nitrogen, neon, argon and helium gases, which are easy to obtain, cheap and pollution-free. In addition, the heat recovery cycle is adopted, which effectively reduces the compression work and expansion work, significantly reduces the irreversible loss, and greatly improves the economy of the system.
[0019] (3) The helium liquefaction cryogenic compressor unit and the mechanical cryogenic compressor described in the utility model both adopt an oil-free gas-suspended centrifugal compressor, which has the advantages of being oil-free, having high heat transfer efficiency, being frictionless, having a long service life, having a high speed, having a compact structure, having a simple system, being stable and reliable in operation, and being energy-saving and efficient, thus avoiding the problems of oil pollution and oil freezing and blockage, and significantly improving reliability.
[0020] (4) The helium liquefaction cryogenic compressor unit described in the utility model adopts two two-stage compression type centrifugal compressors connected in series to achieve four-stage compression. A mechanical low-temperature pre-cooling cycle is performed between the two compressors to keep the helium at the inlet of the second compressor in a low-temperature state. Inter-stage cooling effectively reduces the compression heat, and low-temperature compression improves the thermodynamic performance of the system. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 A flow chart of an open helium liquefaction cryogenic circulation system provided in Example 1 of the utility model.
[0022] Figure 2 A flow chart of a closed helium liquefaction cryogenic circulation system provided in Example 2 of the utility model.
[0023] Figure 3 A flow chart of a single-stage expansion helium liquefaction cryogenic circulation system provided in Example 3 of the utility model.
[0024] Figure 4 This is a flow chart of a mechanical low-temperature precooling cycle provided in an embodiment of the utility model.
[0025] Figure 5 This is a schematic diagram of the process flow of the helium liquefaction cryogenic compressor unit provided in an embodiment of the utility model.
[0026] Figure 6 This is a schematic diagram of the process of the helium liquefaction room temperature compressor unit.
[0027] In the figure above, the helium liquefaction circulation system 1, the first electromagnetic three-way valve 101, the second electromagnetic three-way valve 102, the expansion pipeline throttle valve 103, the first turbine expander 104, the second turbine expander 105, the third electromagnetic three-way valve 106, the helium throttle valve 107, the liquid helium dewar 108, the liquid storage tank 109, the gate valve 110, the heat exchanger 111, the fourth electromagnetic three-way valve 112, the heat exchanger assembly 120, the first heat exchanger 121, the second heat exchanger 122, the third heat exchanger 123, the fourth Heat exchanger 124, fifth heat exchanger 125, sixth heat exchanger 126, seventh heat exchanger 127; mechanical low-temperature pre-cooling circulation system 2, mechanical low-temperature compressor 201, aftercooler 202, turbine expander 203, regenerator 204; helium liquefaction low-temperature compressor unit 4, first low-temperature compressor 401, intermediate heat exchanger 402, second low-temperature compressor 403; helium liquefaction normal temperature compressor unit 5, first normal temperature compressor 501, intermediate cooler 502, second normal temperature compressor 503. DETAILED DESCRIPTION
[0028] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.
[0029] Example 1
[0030] The utility model provides an open helium liquefaction low temperature circulation system, please refer to Figure 1 and Figure 4 , including a helium liquefaction circulation system 1 and a mechanical low-temperature precooling circulation system 2, wherein the mechanical low-temperature precooling circulation system 2 provides precooling for the helium liquefaction circulation system 1, and its working mode is as follows:
[0031] The high-pressure helium at the outlet of the helium liquefaction cryogenic compressor unit 4 is precooled by the second heat exchanger 122 in the heat exchanger assembly 120 through the mechanical cryogenic precooling cycle 2 and heat exchanged by the third heat exchanger 123, and then enters the second electromagnetic three-way valve 102 to be divided into two parts. One part enters the heat exchanger assembly 120 and is cooled by the reflux cold helium gas in the fourth-stage heat exchanger, and then is throttled by the helium throttle valve 107 to produce a saturated gas-liquid mixture of helium, and enters the liquid helium dewar 108. The liquid helium produced by the liquid helium dewar 108 enters the liquid storage tank 109 for storage. The gas produced by the liquid helium dewar 108 is merged with the other part of the cold helium gas that enters the second-stage turbine expander through adiabatic expansion and refrigeration along the reflux pipeline at the third electromagnetic three-way valve 106, and then flows back to the first electromagnetic three-way valve 101 and merges with the helium source precooled by the mechanical cryogenic precooling cycle to enter the helium liquefaction cryogenic compressor unit 4, completing the entire helium liquefaction cycle.
[0032] The high-pressure gas at the outlet of the mechanical cryogenic compressor 201 enters the aftercooler 202 for cooling, and the cooled gas enters the compression end of the turbine expander 203 to increase the pressure, and then enters the regenerator 204 for heat exchange with the reflux gas, and then enters the expansion end of the turbine expander 203 for adiabatic expansion refrigeration. The low-temperature gas coming out of the expansion end of the turbine expander 203 is divided into two parts by the fourth electromagnetic three-way valve 112, one part is the helium source of the helium liquefaction circulation system 1, which is pre-cooled by the first heat exchanger 121, and the other part is the intermediate heat exchange of the helium liquefaction cryogenic compressor unit 4 in the helium liquefaction circulation system 1, and the inlet and outlet pipelines of the helium liquefaction cryogenic compressor unit 4 are pre-cooled by the second heat exchanger 122. The pre-cooled gas converges, exchanges heat in the regenerator 204, and finally enters the mechanical cryogenic compressor 201, completing the entire mechanical cryogenic pre-cooling cycle.
[0033] Example 2
[0034] The utility model provides a closed helium liquefaction low temperature circulation system, please refer to Figure 2 and Figure 4 , including a helium liquefaction circulation system 1 and a mechanical low-temperature precooling circulation system 2, wherein the mechanical low-temperature precooling circulation system 2 provides precooling for the helium liquefaction circulation system 1, and its working mode is as follows:
[0035] The high-pressure helium at the outlet of the helium liquefaction cryogenic compressor unit 4 is precooled by the second heat exchanger 122 in the heat exchanger assembly 120 through mechanical cryogenic precooling cycle 2 and heat exchanged by the third heat exchanger 123, and then enters the second electromagnetic three-way valve 102 to be split into two parts. One part enters the heat exchanger assembly 120 and is cooled by the reflux cold helium in the fourth-stage heat exchanger, and then is throttled by the helium throttle valve 107 to produce a saturated gas-liquid mixture of helium, and then enters the liquid helium dewar 108. When the amount of liquid helium stored in the liquid helium dewar 108 meets the requirement, , close the helium source inlet of the first electromagnetic three-way valve 101, and when the gate valve 110 is opened, the stored liquid helium enters the heat exchanger 111 for cooling and heat exchange for other devices. After the heat exchange, the liquid helium is converted into helium, and after merging with the helium generated by the liquid helium Dewar 108, it is gathered at the third electromagnetic three-way valve 106 along the reflux pipeline with another part of the cold helium that enters the second-stage turbine expander for adiabatic expansion and refrigeration, and then flows back to the first electromagnetic three-way valve 101 and enters the helium liquefaction cryogenic compressor unit 4, completing the entire helium liquefaction cycle.
[0036] The high-pressure gas at the outlet of the mechanical cryogenic compressor 201 enters the aftercooler 202 for cooling, and the cooled gas enters the compression end of the turbine expander 203 to increase the pressure, and then enters the regenerator 204 for heat exchange with the reflux gas, and then enters the expansion end of the turbine expander 203 for adiabatic expansion refrigeration. Since the helium liquefaction cycle adopts a closed type, no helium source enters the system, so the pipeline of the fourth electromagnetic three-way valve 112 through the first heat exchanger 121 is closed, and the low-temperature gas coming out of the expansion end of the turbine expander 203 passes through the fourth electromagnetic three-way valve 112 for intermediate heat exchange of the helium liquefaction cryogenic compressor unit 4 in the helium liquefaction cycle system 1, and the inlet and outlet pipelines of the helium liquefaction cryogenic compressor unit 4 are pre-cooled through the second heat exchanger 122. The pre-cooled gas converges and passes through the regenerator 204 for heat exchange, and finally enters the mechanical cryogenic compressor 201, completing the entire mechanical cryogenic precooling cycle.
[0037] Example 3
[0038] The utility model provides a single-stage expansion helium liquefaction low-temperature circulation system, please refer to Figure 3 and Figure 4, including a helium liquefaction circulation system 1 and a mechanical low-temperature precooling circulation system 2, wherein the mechanical low-temperature precooling circulation system 2 provides precooling for the helium liquefaction circulation system 1, and its working mode is as follows:
[0039] The high-pressure helium at the outlet of the helium liquefaction cryogenic compressor unit 4 is precooled by the mechanical cryogenic precooling cycle 2 of the second heat exchanger 122 in the heat exchanger assembly 120 and heat exchanged by the third heat exchanger 123, and then enters the second electromagnetic three-way valve 102 to be divided into two parts. One part enters the heat exchanger assembly 120 and is cooled by the reflux cold helium gas in the three-stage heat exchanger, and then is throttled by the helium throttle valve 107 to produce a saturated gas-liquid mixture of helium, and enters the liquid helium dewar 108. The liquid helium produced by the liquid helium dewar 108 enters the liquid storage tank 109 for storage. The gas produced by the liquid helium dewar 108 is merged with the other part of the cold helium gas that enters the single-stage turbine expander through adiabatic expansion and refrigeration at the third electromagnetic three-way valve 106 along the reflux pipeline, and then flows back to the first electromagnetic three-way valve 101 and merges with the helium source precooled by the mechanical cryogenic precooling cycle to enter the helium liquefaction cryogenic compressor unit 4, completing the entire helium liquefaction cycle.
[0040] The process of the mechanical low-temperature pre-cooling circulation system is the same as that of the first embodiment and will not be repeated here.
[0041] The helium liquefaction cryogenic compressor unit provided by the utility model, please refer to Figure 3 , including a first low-temperature compressor 401, an intermediate heat exchanger 402, and a second low-temperature compressor 403, and its working method is as follows:
[0042] The low-temperature helium at 80K or 120K enters the first low-temperature compressor 401 for two-stage compression, and then is pre-cooled by the mechanical low-temperature pre-cooling cycle in the intermediate heat exchanger 402. After being cooled to 80K or 120K again, the helium enters the second low-temperature compressor 403 for two-stage compression; the helium liquefaction low-temperature compressor unit 4 uses two two-stage compression type centrifugal compressors connected in series to achieve four-stage compression, and intermediate cooling and mechanical low-temperature pre-cooling cycle pre-cooling are performed between the two compressors.
[0043] As a comparison with the helium liquefaction low temperature compressor unit provided by the utility model, please refer to the helium liquefaction normal temperature compressor unit Figure 4 , including a first normal temperature compressor 501, an intercooler 502, and a second normal temperature compressor 503, and its working mode is as follows:
[0044] The 300K normal temperature helium enters the first normal temperature compressor 501 for two-stage compression, and then is cooled by the intermediate cooler 502. After that, the helium is cooled to 300K again and enters the second normal temperature compressor 503 for two-stage compression. The helium liquefaction normal temperature compressor unit 5 uses two two-stage compression type centrifugal compressors connected in series to achieve four-stage compression, and intermediate cooling is performed between the two compressors.
[0045] At the same compressor efficiency, pressure ratio, and helium mass flow rate, the comparison between normal temperature compression and low temperature compression is as follows:
[0046] Among them, the efficiency of the compressor is 75%, the suction pressure of the first compressor is 1.1 bar, the pressure ratio of the first compressor is 3.31, the pressure ratio of the second compressor is 3.31, the total pressure ratio is 12, and the helium mass flow rate is 0.1 kg / s:
[0047] (1) When normal temperature compression and intermediate cooling are adopted, the inlet temperature of the first compressor is 300K, and the temperature of the helium after intermediate cooling is 300K. The calculation results are:
[0048] The power of the first compressor is 127.66kW, the power of the second compressor is 127.3kW, and the total power is 254.96kW.
[0049] (2) When low-temperature compression and intermediate cooling are adopted, the inlet temperature of the first compressor is 80K, and the temperature of the helium after intermediate cooling is 80K. The calculation results are:
[0050] The power of the first compressor is 34.12 kW, the power of the second compressor is 34.19 kW, and the total power is 68.31 kW.
[0051] (3) When low-temperature compression and intermediate cooling are adopted, the inlet temperature of the first compressor is 120K, and the temperature of the helium after intermediate cooling is 120K. The calculation results are:
[0052] The power of the first compressor is 51.13 kW, the power of the second compressor is 51.23 kW, and the total power is 102.36 kW.
[0053] From the above calculation results, we can conclude that:
[0054] Compared with the intermediate cooling measures in normal temperature compression, the compression work of 80K low-temperature compression is reduced by 73.21% compared with the compression work of 300K normal temperature compression, and the compression work of 120K low-temperature compression is reduced by 59.85% compared with the compression work of 300K normal temperature compression; the reduction effect is obvious.
[0055] The utility model provides a helium liquefaction cryogenic circulation system, which changes the traditional liquid nitrogen precooling into a mechanical cryogenic precooling circulation precooling, so that the two parts of helium entering the helium liquefaction cryogenic compressor unit are precooled by the mechanical cryogenic precooling circulation, and the normal temperature helium is converted into low temperature helium. The low temperature compression reduces the compression work, and effectively improves the system efficiency; the mechanical cryogenic precooling circulation is used to precool the helium liquefaction system. Compared with liquid nitrogen precooling, the mechanical cryogenic precooling circulation uses air, nitrogen, neon, argon and helium gas as working fluids, which are easy to obtain, cheap and pollution-free, and adopts a heat recovery circulation, so that the compression work and expansion work are effectively reduced, the irreversible loss is significantly reduced, and the system efficiency is greatly improved. The economy of the system is improved; both the helium liquefaction cryogenic compressor unit and the mechanical cryogenic compressor adopt oil-free gas suspension centrifugal compressor, which has the advantages of oil-free, high heat transfer efficiency, no friction, long service life, high speed, compact structure, simple system, stable and reliable operation, energy saving and high efficiency, etc., avoiding the problems of oil pollution and oil freezing, and the reliability will be significantly improved; the helium liquefaction cryogenic compressor unit adopts two two-stage compression type centrifugal compressors in series to achieve four-stage compression, and mechanical low-temperature pre-cooling cycle pre-cooling is carried out between the two compressors to keep the helium at the inlet of the second compressor in a low-temperature state. The inter-stage cooling effectively reduces the compression heat, and the low-temperature compression improves the thermodynamic performance of the system.
[0056] Of course, the helium liquefaction cryogenic circulation system of the present invention can also have a variety of changes and modifications, and is not limited to the specific structure of the above-mentioned embodiment. In short, the protection scope of the present invention should include those changes or substitutions and modifications that are obvious to ordinary technicians in the field.
Claims
1. A helium liquefaction cryogenic circulation system, characterized in that: Including helium liquefaction circulation system and mechanical low-temperature pre-cooling circulation system; The mechanical low-temperature precooling circulation system provides precooling for the helium liquefaction circulation system; The helium liquefaction circulation system includes a first electromagnetic three-way valve, a helium liquefaction cryogenic compressor unit, a second electromagnetic three-way valve, an expansion pipeline throttle valve, a first turbine expander, a second turbine expander, a third electromagnetic three-way valve, a helium throttle valve, a liquid helium dewar, a liquid storage tank, a gate valve, a heat exchanger, a heat exchanger assembly, and a fourth electromagnetic three-way valve; The heat exchanger assembly includes a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a fifth heat exchanger, a sixth heat exchanger, and a seventh heat exchanger, which can be increased or decreased accordingly according to the scale of the system, and each stage of heat exchangers is connected in sequence; The first turbo expander and the second turbo expander are sequentially connected to form a two-stage turbo expander; The helium liquefaction cryogenic compressor unit comprises a first cryogenic compressor, an intermediate heat exchanger, and a second cryogenic compressor; The mechanical low-temperature precooling circulation system includes a mechanical low-temperature compressor, an aftercooler, a turbine expander, and a regenerator.
2. The helium liquefaction cryogenic circulation system according to claim 1, characterized in that: The high-pressure helium at the outlet of the helium liquefaction cryogenic compressor unit is precooled by the mechanical cryogenic precooling cycle of the second heat exchanger in the heat exchanger assembly and heat exchanged by the third heat exchanger, and then enters the second electromagnetic three-way valve to be divided into two parts. One part enters the fourth-stage heat exchanger in the heat exchanger assembly and is cooled by the reflux cold helium, and then is throttled by the helium throttle valve to produce a saturated gas-liquid mixture of helium, and enters the liquid helium dewar. The liquid helium produced by the liquid helium dewar enters the liquid storage tank for storage. The gas produced by the liquid helium dewar is merged with the other part of the cold helium that enters the second-stage turbine expander through adiabatic expansion and refrigeration at the third electromagnetic three-way valve along the reflux pipeline, and then flows back to the first electromagnetic three-way valve and merges with the helium source that has been precooled by the mechanical cryogenic precooling cycle to enter the helium liquefaction cryogenic compressor unit to complete the entire helium liquefaction cycle.
3. The helium liquefaction cryogenic circulation system according to claim 1, characterized in that: The high-pressure gas at the outlet of the mechanical cryogenic compressor enters the aftercooler for cooling, and the cooled gas enters the compression end of the turbine expander to increase the pressure, and then enters the regenerator for heat exchange with the reflux gas, and then enters the expansion end of the turbine expander for adiabatic expansion refrigeration. The low-temperature gas coming out of the expansion end of the turbine expander is divided into two parts through the fourth electromagnetic three-way valve, one part is the helium source of the helium liquefaction circulation system, which is pre-cooled through the first heat exchanger, and the other part is the intermediate heat exchange of the helium liquefaction cryogenic compressor unit in the helium liquefaction circulation system, and the inlet and outlet pipelines of the helium liquefaction cryogenic compressor unit are pre-cooled through the second heat exchanger. The pre-cooled gas converges, exchanges heat through the regenerator, and finally enters the mechanical cryogenic compressor, completing the entire mechanical cryogenic precooling cycle.
4. The helium liquefaction cryogenic circulation system according to claim 1, characterized in that: The first electromagnetic three-way valve, the helium liquefaction cryogenic compressor unit, the second electromagnetic three-way valve, the expansion pipeline throttle valve, the first turbine expander, the second turbine expander, the third electromagnetic three-way valve, the helium throttle valve, the heat exchanger assembly, the turbine expander, the regenerator, and the fourth electromagnetic three-way valve are all arranged in the vacuum cold tank.
5. The helium liquefaction cryogenic circulation system according to claim 1, characterized in that: The helium circulation cryogenic compressor unit is an oil-free gas suspension centrifugal compressor, which is supported by gas suspension bearings or magnetic hybrid bearings. Its compression is low-temperature compression. The helium circulation cryogenic compressor unit uses 1-4 centrifugal compressors in series to achieve 1-10 levels of compression. The compressor stages are pre-cooled by a mechanical low-temperature pre-cooling cycle. The compressor inlet temperature is between 10K and 250K, and the working fluid used is helium.
6. The helium liquefaction cryogenic circulation system according to claim 1, characterized in that: The mechanical low-temperature compressor is an oil-free gas suspension centrifugal compressor, which is supported by gas suspension bearings or magnetic mixed bearings. The compression is room temperature compression, and the compressor inlet temperature is between 230K and 340K.
7. The helium liquefaction cryogenic circulation system according to claim 1, characterized in that: The working fluid of the mechanical low-temperature precooling circulation system is air, nitrogen, neon, argon and helium.