Cryogenic rectification system for helium isotope separation

Abstract

The utility model provides a kind of for helium isotope separation's low-temperature rectification system, low-temperature rectification system includes: refrigeration plant, including refrigerator, heat exchanger assembly, superfluid helium cavity and condenser, refrigerator and heat exchanger assembly are used to change cold source medium into superfluid helium and store in superfluid helium cavity, superfluid helium cavity provides cold quantity for work area by condenser, wherein, cold source medium is helium gas;Rectification device, the top of rectification device is connected with condenser, for by condenser the ascending gas phase is condensed as liquid phase;Reboiler, the bottom of rectification device is connected with reboiler, for by reboiler heating liquid phase generates ascending gas phase;Feed unit and discharge unit, feed unit and discharge unit are connected with rectification device respectively, for feeding to rectification device, and discharge recovery is carried out.The utility model can handle low-abundance helium-3 raw gas and high-concentration helium-3 waste gas by developing a set of efficient, continuous, low-cost rectification system and process.

Description

Technical Field

[0001] This utility model relates to the field of cryogenic distillation technology, and in particular to a cryogenic distillation system for helium isotope separation. Background Technology

[0002] Helium is primarily composed of two isotopes: helium-3 (He-3) and helium-4 (He-4), with He-3 having an extremely low natural abundance. However, due to its unique physical properties, He-3 has significant applications in neutron detection, cryogenic refrigeration, medical imaging, and nuclear fusion research. Currently, the main industrial sources of He-3 are natural gas and nuclear waste gas. The He-3 content in natural gas is typically between 0.1 and 1.0 ppm, while the abundance of He-3 in nuclear waste gas varies, commonly ranging from 0.01% to 2%.

[0003] Currently, cryogenic distillation, as a highly efficient method for separating helium isotopes, has been widely studied by researchers. However, conventional laboratory methods primarily utilize cryogenic distillation to separate helium isotopes with a He⁻ abundance of 0.1% or higher. This approach is limited to source gases with high He⁻ abundance and often uses liquid helium as a cooling source, lacking a process design for continuous He⁻ recovery, thus failing to meet the demands of commercial production. For example, in related technologies, small packed towers using liquid helium as a cooling source for total reflux processing of mixtures with a He⁻ abundance of 1-2% cannot achieve continuous operation, and exhibit low He⁻ recovery rates, large residues, and high costs. Furthermore, related technologies typically employ over-leakage methods to treat the source gas mixture in natural gas before purifying He⁻ through distillation. This method usually suffers from small processing capacity, low separation efficiency, and inability to operate continuously, making it difficult to achieve efficient and economical He⁻ recovery on an industrial scale.

[0004] It is worth noting that customers using high-purity helium-3 generate contaminated helium-3 waste gas after use. Although the concentration of helium-3 in this waste gas decreases, it is usually still at a high level (e.g., 60%-90%). For the re-enrichment and recovery of such high-concentration helium-3 waste gas, the ultraleak method is no longer effective due to physical limitations. Feasible technical approaches mainly include adsorption and distillation; however, adsorption is generally inferior to distillation in terms of throughput, separation efficiency, and scalability, facing challenges such as small throughput and relatively low efficiency. Therefore, researching how to efficiently, continuously, and cost-effectively treat low-abundance helium-3 feed gas and high-concentration helium-3 waste gas is the direction the applicant is committed to researching. Utility Model Content

[0005] This invention provides a cryogenic distillation system for helium isotope separation, which addresses the shortcomings of existing technologies in achieving low-cost and efficient recovery of low-abundance helium-3 feed gas and high-concentration helium-3 waste gas. By developing a high-efficiency, continuous, and low-cost distillation system and process, it can not only handle low-abundance helium-3 feed gas but is also suitable for high-concentration helium-3 waste gas, providing a reliable means for the recycling of high-concentration helium-3 waste gas.

[0006] This invention provides a cryogenic distillation system for helium isotope separation, comprising:

[0007] A refrigeration device includes a refrigerator, a heat exchanger assembly, a superfluid helium chamber, and a condenser. The refrigerator and heat exchanger assembly are used to convert a cold source medium into superfluid helium and store it in the superfluid helium chamber. The superfluid helium chamber provides cooling to the working area through the condenser. The cold source medium is helium.

[0008] A distillation apparatus, the top of which is connected to the condenser for condensing rising gas phase into liquid phase via the condenser;

[0009] A reboiler, the bottom of the distillation unit is connected to the reboiler, for heating the liquid phase through the reboiler to generate a rising gas phase;

[0010] The feeding unit and the discharging unit are respectively connected to the distillation apparatus for feeding materials into the distillation apparatus and for discharging and recovering materials.

[0011] The cryogenic distillation system for helium isotope separation provided by this utility model further includes a feed precooling device disposed between the feed unit and the distillation device, for precooling the feed mixture so that the feed mixture enters the distillation device at a preset temperature.

[0012] According to the present invention, a cryogenic distillation system for helium isotope separation is provided, wherein the reboiler is provided with a bottom discharge connector, and the feed precooling device is connected to the bottom discharge connector via a pipeline. The feed precooling device is configured to exchange heat between the bottom discharge gas of the distillation unit and the feed mixture in the feed precooling device.

[0013] According to the present invention, a cryogenic distillation system for helium isotope separation is provided, wherein the feed precooling device includes multiple regenerating heat exchangers and multiple precooling heat exchangers, the regenerating heat exchangers and the precooling heat exchangers being arranged alternately.

[0014] According to the present invention, a cryogenic distillation system for helium isotope separation is provided, wherein the feed precooling device includes a filter disposed upstream of the regenerating heat exchanger for filtering and removing impurities from the feed mixture.

[0015] According to the present invention, a cryogenic distillation system for helium isotope separation is provided, wherein the feed precooling device includes a feed temperature control tank, which is located downstream of the precooling heat exchanger and connected to the middle part of the distillation device.

[0016] According to the present invention, a cryogenic distillation system for helium isotope separation is provided, wherein both the condenser and the reboiler are equipped with heating elements and temperature sensors.

[0017] According to the present invention, a cryogenic distillation system for helium isotope separation is provided, wherein the feeding unit includes a feeding tank and a first helium isotope analyzer connected to the feeding tank. The feeding tank is used to receive raw material gas, and the first helium isotope analyzer is used to detect the abundance of helium-3 in the raw material gas.

[0018] According to the present invention, a cryogenic distillation system for helium isotope separation is provided, wherein the discharge unit includes a gas mixer and a second helium isotope analyzer, the condenser is provided with a top discharge connector, the reboiler is provided with a bottom discharge connector, and both the top discharge connector and the bottom discharge connector are connected to the gas mixer.

[0019] The second helium isotope analyzer is installed on the connecting pipeline between the top discharge joint of the tower and the gas mixer, and is used to detect the abundance of helium-3 in the top discharge gas.

[0020] According to the present invention, a cryogenic distillation system for helium isotope separation is provided, wherein the feed unit includes a feed tank disposed downstream of the gas mixer, and the feed tank is disposed on the connecting pipeline between the feed tank and the distillation apparatus.

[0021] The cryogenic distillation system for helium isotope separation provided by this invention is suitable for processing low-abundance helium-3 feed gas and high-concentration helium-3 waste gas, and can achieve efficient, continuous, and large-volume helium-3 extraction. It uses helium as the cold source medium to prepare superfluid helium to provide cooling for the distillation unit. Compared with the existing technology that directly uses liquid helium as the cold source, it can effectively reduce costs and provide favorable conditions for continuous operation and large-scale production, thereby ensuring the continuous and stable operation of the system. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a simplified structural diagram of the cryogenic distillation system for helium isotope separation provided by this utility model.

[0024] Figure 2 This is a schematic diagram of the feeding precooling device provided by this utility model.

[0025] Figure 3 This is a schematic flowchart of the cryogenic distillation method for helium isotope separation provided by this utility model.

[0026] Figure label:

[0027] 10. Distillation column; 11. Reboiler; 12. Refrigeration unit; 13. Superfluid helium chamber; 14. Condenser; 15. First-stage cold shield; 16. Helium cold trap; 17. First-stage helium heat exchanger; 18. Second-stage helium heat exchanger; 19. Helium regenerative heat exchanger; 20. Throttling valve; 21. Helium pump; 22. Cooling inlet pipeline; 23. Feed precooling device; 231. First-stage regenerative heat exchanger; 232. First-stage precooling heat exchanger; 233. Second-stage regenerative heat exchanger; 234. Second-stage precooling heat exchanger; 235. Third-stage regenerative heat exchanger; 236. Filter; 237. Feed temperature control tank; 238. Feed valve; 24. Feed mixture; 25. Top gas; 26. Bottom gas; 27. 28. Feed tank; 29. ​​First helium isotope analyzer; 30. Raw material gas; 31. Gas mixer; 32. Second helium isotope analyzer; 33. Helium-3 product tank; 34. Helium-4 product tank; 35. Feed tank; 36. First switching valve; 37. Feed circulation pump; 38. Pressure reducing valve; 39. Feed flow meter; 40. Top heating resistor; 41. Bottom heating resistor; 42. Top sampling bottle; 43. Bottom sampling bottle; 44. Top discharge circulation pump; 45. Top discharge flow meter; 46. Second switching valve; 47. First check valve; 48. Bottom discharge circulation pump; 49. Bottom discharge flow meter; 50. Third switching valve; 51. Second check valve; 52. Fourth switching valve. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0029] In the description of this utility model, it should be understood that the terms "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0030] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0031] In this utility model, unless otherwise expressly specified and limited, the first feature "on" or "below" the second feature may be in direct contact with the first and second features, or indirect contact through an intermediate medium. In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0032] The following is combined with Figure 1 and Figure 2 The present invention describes a cryogenic distillation system for helium isotope separation, comprising: a refrigeration unit, a distillation unit, a reboiler 11, a feeding unit, and a discharging unit.

[0033] The refrigeration device includes a refrigerator 12, a heat exchanger assembly, a superfluid helium chamber 13, and a condenser 14. The refrigerator 12 and heat exchanger assembly convert the cold source medium into superfluid helium and store it in the superfluid helium chamber 13. The superfluid helium chamber 13 provides cooling to the working area through the condenser 14. The cold source medium is helium gas. Using helium gas as the working medium to form superfluid helium and provide cooling to the working area, while ensuring the condenser 14 reaches a certain operating temperature to improve helium-3 separation, effectively reduces costs compared to the conventional use of liquid helium as a cold source. This is particularly suitable for the continuous operation of the system in this application, significantly saving costs while improving system stability and reliability. Furthermore, the helium gas is recyclable, further controlling costs.

[0034] A distillation apparatus is included, with its top connected to a condenser 14 for condensing the rising gas phase into a liquid phase. A reboiler 11 is connected to the bottom of the distillation apparatus for heating the liquid phase to generate a rising gas phase. The distillation apparatus is a distillation column 10. When the distillation column 10 is a packed column, it includes a column body and packing material disposed within the column body. The packing material can be high-efficiency Helipak packing or other packing materials with similar mass transfer efficiency. The specific specifications are set according to the specifications of the column body to improve mass transfer efficiency and shorten separation time. The column body can be made of, for example, sanitary stainless steel or other equivalent cryogenic materials. The inner wall of the column is polished smooth and ultrasonically cleaned to ensure stable operation of gas-liquid countercurrent mass transfer under cryogenic conditions. For example, a feed inlet is provided in the middle of the column body for introducing the feed mixture 24, which can reduce column pressure drop, improve flow stability, reduce energy consumption, and improve the purity and recovery rate of helium-3.

[0035] The system includes a feed unit and a discharge unit, both connected to the distillation apparatus for feeding the raw material and recovering the discharged product. By providing these feed and discharge units, the system achieves fully automated control from feed to final product gas discharge, ensuring continuous system operation and meeting the needs of industrial production. The feed unit is equipped with a detector for the raw material gas 29, and the discharge unit is equipped with a detector for the discharged product gas. This allows for better optimization of operating parameters based on the detection results, ultimately achieving efficient separation of Helium-3.

[0036] In specific application scenarios, such as Figure 1As shown, the refrigeration device includes a refrigerator 12, a primary cold shield 15, a helium cold trap 16, a primary helium heat exchanger 17, a secondary helium heat exchanger 18, a helium regenerative heat exchanger 19, an overfluidized helium chamber 13, a condenser 14, a throttling valve 20, and a helium pump 21. In operation, the overfluidized helium chamber 13 is pre-cooled to a specified temperature using the cooling capacity of the primary cold head of the refrigerator 12. High-purity helium is then introduced through the cooling inlet pipe 22. The helium first enters the helium cold trap 16 installed on the primary cold shield 15 for impurity removal. The purified helium then enters the primary helium heat exchanger 17, where it undergoes the first stage of cooling using the cooling capacity provided by the primary cold head of the refrigerator 12. Subsequently, it enters the secondary helium heat exchanger 18, where it is cooled and liquefied using the cooling capacity of the secondary cold head of the refrigerator 12. After successful liquefaction, the throttle valve 20 is opened, and the helium pump 21 is turned on simultaneously. Cold helium (which is vaporized when liquid helium first enters the superfluid helium chamber 13) is used to flush the superfluid helium chamber 13, further reducing its temperature. Then, the throttle valve 20 and helium pump 21 are closed, and helium continues to be introduced into the cryogenic system. After successful liquid replenishment in the secondary helium heat exchanger 18 for a period of time, the inlet flow rate is kept constant. The throttle valve 20 and helium pump 21 are then opened. The liquid helium first passes through the helium regeneration heat exchanger 19, where the cold helium extracted from the superfluid helium chamber 13 further cools it. Then, through the throttling effect of the throttle valve 20, the liquid helium is throttled and cooled, transforming into superfluid helium before entering the superfluid helium chamber 13. Combined with the evacuation and depressurization, this continuously provides the superfluid temperature zone working environment to the condenser 14. By setting up a helium regenerative heat exchanger 19, the cold helium extracted from the superfluid helium cavity 13 is used to further cool the liquid helium, thereby achieving efficient recovery and utilization of the internal cooling capacity of the system. This helps to reduce the load on the refrigerator 12, reduce overall energy consumption, and maximize the utilization of the system's cooling capacity.

[0037] As a preferred embodiment of the present invention, the cryogenic distillation system for helium isotope separation further includes a feed precooling device 23, which is disposed between the feed unit and the distillation device, for precooling the feed mixture 24 so that the feed mixture 24 enters the distillation device at a preset temperature.

[0038] like Figure 1 As shown, the refrigeration unit, the feed precooling unit 23, the distillation column 10, and the reboiler 11 together constitute a cryogenic system. This system operates in a vacuum environment, which is beneficial for improving the accuracy of operating parameter control and ensuring stable system operation. By setting up the feed precooling unit 23, it is ensured that the feed mixture 24 enters the distillation column 10 at a preset temperature, thereby improving the separation efficiency. The precooling process can reduce the heat load of the distillation column 10, reduce the overall energy consumption of the system, and avoid the impact of temperature fluctuations on the distillation process, thus making the separation process more stable.

[0039] In some embodiments, the reboiler 11 is provided with a bottom discharge connector, and the feed precooling device 23 is connected to the bottom discharge connector via a pipeline. The feed precooling device 23 is configured to exchange heat between the bottom discharge gas 26 of the distillation unit and the feed mixture 24 in the feed precooling device 23.

[0040] like Figure 2 As shown, the feed mixture 24 of the feeding unit and the bottom discharge gas 26 flowing out from the bottom discharge connector exchange heat in the feed precooling device 23, which can maximize the recovery of the cold energy of the discharge, realize the heat exchange inside the system, reduce the system energy consumption, improve the system economy, provide technical support for continuous operation, and enable the system to work stably for a long time.

[0041] The feed precooling device 23 includes multiple regenerating heat exchangers and multiple precooling heat exchangers, which are arranged alternately. By setting up multi-stage heat exchange, the heat exchange efficiency can be improved, the feed temperature gradient can be precisely controlled, and the separation effect can be optimized.

[0042] For example, such as Figure 2 As shown, the feed precooling device 23 includes a first-stage regenerative heat exchanger 231, a first-stage precooling heat exchanger 232, a second-stage regenerative heat exchanger 233, a second-stage precooling heat exchanger 234, and a third-stage regenerative heat exchanger 235 connected in sequence. In a specific application scenario, after the feed mixture 24 enters the cryogenic system, it first enters the optimized feed precooling device 23. The feed mixture 24 and the bottom discharge gas 26 first undergo a first-stage regenerative heat exchange in the first-stage regenerative heat exchanger 231 to achieve the first feed precooling. Then it enters the first-stage precooling heat exchanger 232, which can precool the feed mixture 24 to below 40K. The feed mixture 24 continues to undergo secondary heat exchange with the bottom discharge gas 26 in the secondary heat exchanger 233, and then enters the secondary precooling heat exchanger 234. The cooling capacity of the secondary cold head of the refrigerator 12 is used to continue cooling the feed mixture 24. At this time, the pressure and temperature changes are observed to determine whether the feed mixture 24 has been successfully liquefied. The liquefied mixture enters the tertiary heat exchanger 235.

[0043] Furthermore, the feed precooling device 23 includes a filter 236, located upstream of the regenerating heat exchanger, for filtering and removing impurities from the feed mixture 24. Specifically, the feed mixture 24 enters the filter 236 for impurity removal before entering the primary regenerating heat exchanger 231. This impurity removal function ensures the purity of the feed mixture 24, avoids the influence of impurities on the distillation process, prevents solid particles from entering the system, protects the heat exchanger and distillation unit, and reduces the risk of contamination of the final product by impurities, thereby improving product purity.

[0044] Furthermore, the feed precooling device 23 includes a feed temperature control tank 237, which is located downstream of the precooling heat exchanger and connected to the middle of the distillation unit. The feed temperature control tank 237 can precisely adjust the feed temperature and optimize separation conditions; as an intermediate container, it balances feed flow fluctuations, making the distillation process more stable; and the feed temperature can be adjusted according to different raw material characteristics to adapt to various separation requirements.

[0045] Specifically, a feed valve 238 is also provided on the connecting pipeline between the three-stage regenerative heat exchanger 235 and the feed temperature control tank 237. After the liquefied mixture enters the three-stage regenerative heat exchanger 235, the feed valve 238 controls the valve opening to reduce the throttled raw material pressure to the feed pressure, and finally enters the feed temperature control tank 237. The feed temperature control tank 237 is equipped with a heating resistor to control the change of the feed temperature (for example, 2.0-2.7K), so that the feed mixture 24 enters from the middle of the distillation column 10 under a specific thermal condition.

[0046] In a preferred embodiment of this invention, both the condenser 14 and the reboiler 11 are equipped with heating elements and temperature sensors. By providing heating elements and temperature sensors, the temperatures of the condenser 14 and reboiler 11 can be monitored in real time, enabling precise control of the operating temperature and thus improving the extraction efficiency of helium-3.

[0047] This system can process both low-abundance Helium-3 feed gas and high-concentration Helium-3 waste gas. For natural gas sources, where He-3 abundance is extremely low, to prevent the influence of superfluid helium climbing over the membrane, the temperature of condenser 14 can be designed and controlled at 2.2-3.0 K, and the temperature of reboiler 11 at 2.3-4.2 K. For nuclear waste gas sources, based on the phase diagram analysis of the He-3 / He-4 mixture, the temperature of condenser 14 can be designed and controlled at 1.4-2.2 K, and the temperature of reboiler 1132 at 2.2-4.2 K. The lower the temperature of condenser 14, the higher the He-3 abundance of the feed gas, thus balancing the suppression of superfluidity with efficient separation. For a helium-3 / helium-4 mixture with a He-3 content of 60% or more, there will be no effect of superfluid helium above 1.0K. Therefore, according to the theory that the lower the temperature, the higher the relative volatility of helium-3 and helium-4, the lower the operating temperature of the distillation helium-3 / helium-4 mixture, the better the enrichment effect. At the same time, sufficient cooling capacity needs to be ensured at this temperature to support the operation of distillation column 10.

[0048] In a preferred embodiment of the present invention, the feeding unit includes a feeding tank 27 and a first helium isotope analyzer 28 connected to the feeding tank 27. The feeding tank 27 is used to receive raw material gas 29, and the first helium isotope analyzer 28 is used to detect the helium-3 abundance in the raw material gas 29.

[0049] The feed gas 29 can be natural gas, nuclear waste gas, or high-concentration helium-3 waste gas, making the system of this invention applicable to the separation of various feed gases 29 and improving the system's versatility. The first helium isotope analyzer 28 can monitor the helium-3 abundance in the feed gas 29 online, providing a basis for adjusting process parameters and ensuring separation effectiveness.

[0050] In some embodiments, the discharge unit includes a gas mixer 30 and a second helium isotope analyzer 31, the condenser 14 is provided with a top discharge connector, the reboiler 11 is provided with a bottom discharge connector, and both the top discharge connector and the bottom discharge connector are connected to the gas mixer 30.

[0051] The second helium isotope analyzer 31 is installed on the connecting pipeline between the top discharge joint of the tower and the gas mixer 30, and is used to detect the helium-3 abundance in the top discharge gas 25.

[0052] This system enables a complete process flow from refrigeration and feeding to product collection. The discharge unit, combined with discharge purity detection, ensures that the final product has the required helium-3 abundance, achieving efficient and high-purity helium-3 extraction. The gas mixer 30 can mix and recover gases from the top and bottom discharges that have not yet reached the required purity, enabling material recycling.

[0053] Furthermore, the discharge unit also includes a helium-3 product tank 32 for collecting the product gas at the top of the column, and a helium-4 product tank 33 for collecting the product gas at the bottom of the column.

[0054] In some embodiments, the feeding unit includes a feed tank 34, located downstream of the gas mixer 30, and the feed tank 34 is disposed on the connecting pipeline between the feed tank 27 and the distillation unit. The feed tank 34 can receive substandard products from the gas mixer 30, enabling material recycling, and can also work in conjunction with the feed tank 27 to regulate the concentration of the feed material entering the distillation column 10. When the pressure in the feed tank 27 is insufficient, it continuously supplies feed gas 29 to the distillation unit to ensure production continuity.

[0055] refer to Figure 1 and Figure 2 The working principle and operation process of the cryogenic distillation system for helium isotope separation of this utility model are as follows.

[0056] The first stage is pre-cooling: After pre-cooling the superfluid helium cavity 13 to a specified temperature using the cooling capacity of the first-stage cold head of the refrigerator 12, high-purity helium is introduced through the cooling inlet pipe 22. It first enters the helium cold trap 16 installed on the first-stage cold screen 15 for impurity removal. The purified helium then enters the first-stage helium heat exchanger 17, where it receives initial cooling from the cooling capacity of the first-stage cold head of the refrigerator 12. It then enters the second-stage helium heat exchanger 18, where it is cooled and liquefied using the cooling capacity of the second-stage cold head of the refrigerator 12. After successful liquefaction, the throttle valve 20 is opened, and the helium pump 21 is activated. Cold helium (which may vaporize upon initial entry into the superfluid helium cavity 13) is used to flush the superfluid helium cavity 13, further reducing its temperature. Afterwards, the throttle valve 20 and helium pump 21 are closed, and helium continues to be introduced into the cryogenic system. After the liquid is successfully replenished in the secondary helium heat exchanger 18 for a period of time, the inlet flow rate is kept constant, and the throttle valve 20 and helium pump 21 are opened. The liquid helium first passes through the helium regeneration heat exchanger 19, and the cold helium extracted from the superfluid helium chamber 13 can further cool the liquid helium. Then, through the throttling effect of the throttle valve 20, the liquid helium can be throttled and cooled, and then converted into superfluid helium and enter the superfluid helium chamber 13. Combined with the gas extraction and pressure reduction, the superfluid temperature zone working environment can be continuously provided to the condenser 14.

[0057] Next is the feeding stage: the raw material gas 29 first enters the feed tank 27 under the control of the first switching valve 35, and the He-3 abundance in the raw material gas 29 is monitored online by the first helium isotope analyzer 28. After the system is successfully pre-cooled, the feed circulation pump 36 and the pressure reducing valve 37 on the feed pipeline are opened, which controls the raw material gas 29 to enter the cryogenic system at a specified pressure. The flow rate of the raw material gas 29 is controlled by the feed flow meter 38 on the pipeline.

[0058] After the feed mixture 24 enters the cryogenic system, it first enters the optimized feed precooling device 23. After the feed mixture 24 is filtered and impurities are removed in the filter 236, it undergoes a first-stage regenerative heat exchange with the bottom discharge gas 26 in the first-stage regenerative heat exchanger 231 to achieve the first feed precooling. Then it enters the first-stage precooling heat exchanger 232, which can precool the feed mixture 24 to below 40K. The feed mixture 24 continues to undergo secondary heat exchange with the bottom gas 26 in the secondary regenerative heat exchanger 233, and then enters the secondary precooling heat exchanger 234. The cooling capacity of the secondary cold head of the chiller 12 further cools the feed mixture 24. At this point, pressure and temperature changes are observed to determine if the feed mixture 24 has successfully liquefied. The liquefied mixture enters the tertiary regenerative heat exchanger 235, and then the feed valve 238 controls the valve opening to reduce the throttled feed pressure to the feed pressure. Finally, it enters the feed temperature control tank 237, which is equipped with a heating resistor to control the feed temperature (e.g., 2.0-2.7K). Ultimately, the feed mixture 24 enters the distillation column 10 from the middle under specific thermal conditions. This regenerative effect only applies during continuous operation and when the bottom gas is continuously discharged.

[0059] Next is the temperature control stage of distillation column 10: the top of condenser 14 is connected to the bottom of superfluid helium chamber 13, either integrally welded or bolted together. The cooling capacity provided by superfluid helium chamber 13 condenses the gas at the top of the column into liquid, providing reflux. Heating elements, such as the top heating resistor 39, are installed on condenser 14 to control its temperature and reflux ratio. Heating elements, such as the bottom heating resistor 40, are installed on reboiler 11 to control its temperature and liquid evaporation rate, ensuring that a portion of the liquid helium vaporizes and enters distillation column 10 for gas-liquid mass transfer separation with the reflux. The two heating resistors jointly regulate and control the operating pressure of distillation column 10. The pressure of distillation column 10 decreases as the temperature drops. To prevent negative pressure within distillation column 10, the feed flow rate needs to be controlled to replenish the raw material gas 29.

[0060] For the natural gas source gas, the He-3 abundance is extremely low. To prevent the influence of superfluid helium climbing over the film, the temperature of condenser 14 can be designed and controlled at 2.2-3.0K, and the temperature of reboiler 11 at 2.3-4.2K. For the nuclear waste gas source gas, based on the phase diagram analysis of the He-3 / He-4 mixture, the temperature of condenser 14 can be designed and controlled at 1.4-2.2K, and the temperature of reboiler 1132 at 2.2-4.2K. The lower the temperature of condenser 14, the higher the He-3 abundance of the feedstock, thus balancing the suppression of superfluidity and efficient separation. For helium-3 / helium-4 mixtures with a He-3 content of over 60%, there is no influence of superfluid helium above 1.0K. Therefore, according to the theory that the lower the temperature, the higher the relative volatility of helium-3 and helium-4, the lower the operating temperature of the distillation of the helium-3 / helium-4 mixture, the better the enrichment effect. At the same time, sufficient cooling capacity needs to be ensured at this temperature to support the operation of distillation column 10.

[0061] Total reflux stage: After a certain amount of liquid accumulates in the reboiler 11, the maximum heat is first added to perform a pre-overflow operation to fully wet the packing by controlling the heating amount of the bottom heating resistor 40. Then, a total reflux experiment is conducted under the specified output of the bottom heating resistor 40, while the heating power of the condenser 14 is reduced accordingly to ensure the stability of the pressure in the distillation column 10. Because the reboiler 11 is heated, the liquid helium at the bottom of the distillation column 10 continues to vaporize, while the He-3 gas continuously liquefies due to the continuous cooling of the top condenser 14. Finally, gas-liquid and heat balances are achieved within the distillation column 10. After the total reflux stabilizes, the top sampling bottle 41 and the bottom sampling bottle 42 can be opened, and the He-3 / He-4 gas in the column enters the sampling bottles under the pressure difference.

[0062] Continuous operation phase: After the total reflux is completed, the feed activation is started, and the flow rate is set for sampling. The product gas in condenser 14—the top discharge gas 25—is pumped out by the top discharge circulation pump 43, reheated through the top pipeline of distillation column 10, and then led out. Its flow rate is controlled by the top discharge flow meter 44 on the pipeline, and then connected to the second helium isotope analyzer 31 to monitor the He-3 abundance of the top discharge gas 25 online. Due to the sudden disturbance, the continuous operation of distillation requires a certain amount of time to reach a steady state. Therefore, the He-3 abundance of the top discharge gas 25 cannot meet the product requirements at the beginning. At this time, the second switching valve 45 is closed and the first one-way valve 46 is opened, and the top discharge gas 25 is recovered through the gas mixer 30. Meanwhile, the product gas from reboiler 11—the bottom discharge gas 26—is pumped out by the bottom discharge circulation pump 47, reheated through the bottom pipeline of distillation column 10, and its flow rate is controlled by the bottom discharge flow meter 48 on this pipeline. Since the He-3 abundance of the top discharge cannot meet the product requirements at this time, and according to the law of conservation of mass, it can be determined that the bottom product gas also does not meet the design requirements, the third switch valve 49 is closed, and the second one-way valve 50 is opened. The bottom discharge gas 26 is then mixed and recovered with the top discharge gas 25 via the gas mixer 30. To make rational use of energy, the bottom discharge is used to cool the feed mixture 24 via a counter-current primary regenerative heat exchanger 231, a secondary regenerative heat exchanger 233, and a tertiary regenerative heat exchanger 235. The recovered gas concentration is detected by the first helium isotope analyzer 28 before entering the feed tank 34. When the pressure in the feed tank 27 does not meet the feed requirements, the feed tank 34 continues to supply raw materials. Feed tank 27 and replenishment tank 34 operate alternately until the He-3 abundance of the top product reaches the required level. Then, the first check valve 46 and the second check valve 50 are closed, the second switch valve 45 is opened to collect the top product gas into the Helium-3 product tank 32, and the third switch valve 49 is opened to collect the bottom product gas into the Helium-4 product tank 33. This process can directly enrich and recover over 99% He-3 from nuclear waste gas sources. With secondary recycling, ultra-high purity He-3 can be obtained. For natural gas sources, after setting a specific operating temperature and undergoing a single distillation, Helium-3 can be enriched to 10%. 5 To achieve high-concentration He-3 product purification, the helium isotope gas collected in the helium-3 product tank 32 needs to be circulated 2 to 3 times. The helium isotope gas collected in the helium-3 product tank 32 can be introduced into the feed tank 27 through the fourth switch valve 51. By repeating the above operation, a high-concentration He-3 product can be obtained.

[0063] Shutdown recovery phase: After the continuous operation phase ends, first shut off the feed, then stop the precooling of the refrigeration unit 12, and close the second switch valve 45 and the third switch valve 49. During the reheating process, the discharge flow from the top and bottom of the column is not closed, so that almost all the mixed gas in the distillation column 10 can be collected into the feed tank 27 or the replenishment tank 34.

[0064] By using the aforementioned cryogenic distillation system for helium isotope separation, this invention also provides a cryogenic distillation method for helium isotope separation, such as... Figure 3 As shown, it includes the following steps:

[0065] S100. Superfluid helium is prepared by the refrigeration device to provide cooling for the operation of the distillation device;

[0066] S200, Feeding the distillation unit through the feeding unit;

[0067] S300, The top discharge gas separated from the top of the distillation unit and the bottom discharge gas separated from the bottom of the distillation unit are collected through the discharge unit.

[0068] In step S100, the process of the pre-cooling stage described above can be referenced, and the condenser 14 continuously provides the working environment for the superfluid temperature zone. In step S200, the process of the feeding stage and the temperature control stage of the distillation column 10 can be referenced to optimize the feed gas 29 while precisely controlling the operating parameters of the distillation unit. In step S300, the process of the continuous operation stage can be referenced to realize the detection, recycling, and recovery of qualified product gas from the output, achieving full-process operation from feed to output.

[0069] The cryogenic distillation system and method for helium isotope separation provided by this utility model are suitable for processing low-abundance helium-3 feed gas and high-concentration helium-3 waste gas, and can achieve efficient, continuous, and large-volume helium-3 extraction. Helium is used as the cold source medium to prepare superfluid helium to provide cooling for the operation of the distillation device. Compared with the existing technology that directly uses liquid helium as the cold source, it can effectively reduce costs and provide favorable conditions for continuous operation of the system to achieve large-scale production, thereby ensuring the continuous and stable operation of the system.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A cryogenic distillation system for helium isotope separation, characterized in that, include: The refrigeration device includes a refrigerator (12), a heat exchanger assembly, a superfluid helium chamber (13), and a condenser (14). The refrigerator (12) and the heat exchanger assembly are used to convert the cold source medium into superfluid helium and store it in the superfluid helium chamber (13). The superfluid helium chamber (13) provides cooling to the working area through the condenser (14). The cold source medium is helium. A distillation apparatus, the top of which is connected to the condenser (14) for condensing the rising gas phase into a liquid phase through the condenser (14); A reboiler (11) is connected to the bottom of the distillation unit for heating the liquid phase through the reboiler (11) to generate a rising gas phase. The feeding unit and the discharging unit are respectively connected to the distillation apparatus for feeding materials into the distillation apparatus and for discharging and recovering materials.

2. The cryogenic distillation system for helium isotope separation according to claim 1, characterized in that, Also includes: A feed precooling device (23) is provided between the feed unit and the distillation unit for precooling the feed mixture (24) so ​​that the feed mixture (24) enters the distillation unit at a preset temperature.

3. The cryogenic distillation system for helium isotope separation according to claim 2, characterized in that, The reboiler (11) is provided with a bottom discharge connector. The feed precooling device (23) is connected to the bottom discharge connector via a pipeline. The feed precooling device (23) is configured to exchange heat between the bottom discharge gas (26) of the distillation unit and the feed mixture (24) in the feed precooling device (23).

4. The cryogenic distillation system for helium isotope separation according to claim 3, characterized in that, The feed precooling device (23) includes multiple regenerating heat exchangers and multiple precooling heat exchangers, which are arranged alternately.

5. The cryogenic distillation system for helium isotope separation according to claim 4, characterized in that, The feed precooling device (23) includes a filter (236) located upstream of the regenerating heat exchanger for filtering and removing impurities from the feed mixture (24).

6. The cryogenic distillation system for helium isotope separation according to claim 4, characterized in that, The feed precooling device (23) includes a feed temperature control tank (237), which is located downstream of the precooling heat exchanger and connected to the middle of the distillation unit.

7. The cryogenic distillation system for helium isotope separation according to any one of claims 1-6, characterized in that, Both the condenser (14) and the reboiler (11) are equipped with heating elements and temperature sensors.

8. The cryogenic distillation system for helium isotope separation according to any one of claims 1-6, characterized in that, The feeding unit includes a feeding tank (27) and a first helium isotope analyzer (28) connected to the feeding tank (27). The feeding tank (27) is used to receive raw material gas (29), and the first helium isotope analyzer (28) is used to detect the helium-3 abundance in the raw material gas (29).

9. The cryogenic distillation system for helium isotope separation according to claim 8, characterized in that, The discharge unit includes a gas mixer (30) and a second helium isotope analyzer (31). The condenser (14) is provided with a top discharge connector, and the reboiler (11) is provided with a bottom discharge connector. Both the top discharge connector and the bottom discharge connector are connected to the gas mixer (30). The second helium isotope analyzer (31) is installed on the connecting pipeline between the top discharge joint of the tower and the gas mixer (30) to detect the helium-3 abundance in the top discharge gas (25).

10. The cryogenic distillation system for helium isotope separation according to claim 9, characterized in that, The feeding unit includes a feed tank (34) located downstream of the gas mixer (30), and the feed tank (34) is located on the connecting pipeline between the feed tank (27) and the distillation unit.

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