Helium 3 enrichment system

Abstract

The helium-3 enrichment system comprises a first-stage heat exchanger, a second-stage heat exchanger, a third-stage heat exchanger, a refrigerating device and a helium-3 collecting device, and the refrigerating device comprises a vacuum outer cover body, a refrigerating machine, a first-stage cold head, a second-stage cold head and a third-stage cold head; the first-stage heat exchanger is in hot connection with the first-stage cold head, the second-stage heat exchanger is in hot connection with the second-stage cold head, and the third-stage heat exchanger is in hot connection with the third-stage cold head; a first air inlet pipe and a first air outlet pipe are arranged in the first-stage heat exchanger, a second air inlet pipe and a second air outlet pipe are arranged in the second-stage heat exchanger, and a container is arranged in the third-stage heat exchanger; the container is provided with a liquid inlet and an air outlet, and the air outlet is located at the upper end part of the third-stage heat exchanger; the first gas inlet pipe is communicated with raw gas to be treated, and the first gas outlet pipe is communicated with a helium-3 collecting device. According to the invention, helium-3 with abundance of about 0.5% can be enriched to 20%.

Description

Technical Field

[0001] This invention relates to the field of gas separation, and more particularly to a helium-3 enrichment system. Background Technology

[0002] Helium-3 gas plays a crucial role in fields such as neutron detection and quantum computing. However, with the increasingly severe international situation, the amount of helium-3 that can be imported is extremely limited. The helium gas used in dilution refrigerators has a helium-3 abundance of approximately 20%. One of the main sources of helium-3 in China is nuclear shielding gas, which has a helium-3 abundance of approximately 0.2% to 2%. Therefore, it is necessary to enrich helium-3 gas with these abundances. Due to the influence of chemical potential energy and superfluid transition temperature, existing technologies for enriching helium-3 gas struggle to increase the helium-3 abundance to above 5%. Most existing helium-3 enrichment technologies are based on very low-abundance helium-3; when enriching a gas with a helium-3 abundance of 0.2% to 2%, this exceeds the enrichment range, making it difficult to achieve satisfactory enrichment results.

[0003] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a helium-3 enrichment system that solves the problem that existing helium-3 enrichment systems cannot enrich helium-3 with an abundance of about 0.5%.

[0005] The technical solution of the present invention is as follows:

[0006] A helium-3 enrichment system includes a primary heat exchanger, a secondary heat exchanger, a tertiary heat exchanger, a refrigeration unit, and a helium-3 collection unit.

[0007] The refrigeration device includes a vacuum outer casing, a refrigeration unit, and a primary cold head, a secondary cold head, and a tertiary cold head disposed within the vacuum outer casing and connected in sequence to the refrigeration unit.

[0008] The first-stage heat exchanger is thermally connected to the first-stage cold head and is located inside the vacuum casing; the second-stage heat exchanger is thermally connected to the second-stage cold head and is located inside the vacuum casing; the third-stage heat exchanger is thermally connected to the third-stage cold head and is located inside the vacuum casing.

[0009] The first-stage heat exchanger is provided with a first air inlet pipe and a first air outlet pipe, the second-stage heat exchanger is provided with a second air inlet pipe and a second air outlet pipe, and the third-stage heat exchanger is provided with a container; the container is provided with a liquid inlet and an air outlet, with the air outlet located at the upper end of the third-stage heat exchanger.

[0010] The first inlet pipe is connected to the raw gas to be treated, and the first outlet pipe is connected to the helium-3 collection device.

[0011] The first air inlet pipe and the second air inlet pipe, the second air inlet pipe and the liquid inlet, and the air outlet and the second air outlet pipe are connected by conduits.

[0012] Optionally, the primary heat exchanger enables the gas entering the primary heat exchanger to switch between 300K and 35K.

[0013] And / or, the secondary heat exchanger enables the gas entering the secondary heat exchanger to switch between 35K and 4K;

[0014] And / or, the three-stage heat exchanger enables the gas entering the three-stage heat exchanger to switch between 4K and 0.3 to 2K.

[0015] Optionally, the first-stage cold head is connected to the first-stage heat exchanger via an indium sheet, the second-stage cold head is connected to the second-stage heat exchanger via an indium sheet, and the third-stage cold head is connected to the third-stage heat exchanger via an indium sheet.

[0016] Optionally, the raw gas to be treated is a mixture of helium-3 and helium-4, wherein the abundance of helium-3 in the mixture is 0.2% to 2%.

[0017] Optionally, the continuous helium-3 enrichment system further includes a helium-4 collection device, an entropy filter, an entropy filter-driven heater, a superfluid helium-4 vaporization container, and a vaporization container heater, all located within the vacuum enclosure.

[0018] The container has a liquid outlet at the bottom; one end of the entropy filter is connected to the liquid outlet via a conduit, and the other end is connected to the superfluid helium-4 vaporization container via a conduit; the entropy filter drive heater is located between the entropy filter and the superfluid helium-4 vaporization container to heat the conduit between the entropy filter and the superfluid helium-4 vaporization container; the vaporization container heater is located at the lower end of the superfluid helium-4 vaporization container to heat the superfluid helium-4 vaporization container; and the helium-4 collection device is connected to the superfluid helium-4 vaporization container via a conduit.

[0019] Optionally, when superfluid helium-4 flows through the entropy filter, the flow rate of superfluid helium-4 through the entropy filter is controlled by controlling the heating amount of the entropy filter-driven heater or the temperature of the superfluid helium-4.

[0020] Optionally, the average pore size of the filter medium of the entropy filter is less than 100 nm, and the permeability coefficient is less than 1 × 10⁻⁶. - 14 m 2 .

[0021] Beneficial effects: This innovative invention can enrich domestically available helium-3, which has an abundance of 0.5%, to approximately 20% or even higher. This provides feedstock for dilution refrigerators, solving the problem of domestic helium-3 shortage and the lack of mature purification technology.

[0022] This invention can also achieve the synergistic extraction of helium-3 and helium-4, ensuring the long-term continuous and stable operation of the separation system, and ultimately achieving long-term continuous separation and enrichment of helium-3. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of Example 1.

[0024] Figure 2 This is a schematic diagram of the structure of Example 2. Detailed Implementation

[0025] This invention provides a helium-3 enrichment system. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0026] One of the main sources of helium-3 gas in China is nuclear shielding gas, which contains approximately 0.5% helium-3. Therefore, enrichment of this 0.5% helium-3 gas is necessary. However, due to the influence of chemical potential energy and superfluid transition temperature, existing technologies struggle to increase the helium-3 abundance to above 5%. Most existing helium-3 enrichment techniques are based on very low-abundance helium-3; when enriching a 0.5% helium-3 gas, this exceeds the enrichment range, making it difficult to achieve satisfactory enrichment results.

[0027] Based on this, this embodiment provides a helium-3 enrichment system, including a primary heat exchanger 1, a secondary heat exchanger 2, a tertiary heat exchanger 3, a refrigeration device 4, and a helium-3 collection device 5.

[0028] The refrigeration device 4 includes a vacuum outer casing 4-5, a refrigeration unit 4-1, a primary cold head 4-2, a secondary cold head 4-3, and a tertiary cold head 4-4, which are located inside the vacuum outer casing 4-5 and connected in sequence to the refrigeration unit 4-1.

[0029] The first-stage heat exchanger 1 is thermally connected to the first-stage cold head 4-2 and is located inside the vacuum outer casing 4-5; the second-stage heat exchanger 2 is thermally connected to the second-stage cold head 4-3 and is located inside the vacuum outer casing 4-5; and the third-stage heat exchanger 3 is thermally connected to the third-stage cold head 4-4 and is located inside the vacuum outer casing 4-5.

[0030] The first-stage heat exchanger 1 is provided with a first air inlet pipe 1-1 and a first air outlet pipe 1-2. The second-stage heat exchanger 2 is provided with a second air inlet pipe 2-1 and a second air outlet pipe 2-2. The third-stage heat exchanger 3 is provided with a container 3-1. The container 3-1 is provided with a liquid inlet 3-2 and an air outlet 3-3. The air outlet 3-3 is located at the upper end of the third-stage heat exchanger 3.

[0031] The first inlet pipe 1-1 is connected to the raw gas to be treated, and the first outlet pipe 1-2 is connected to the helium-3 collection device 5.

[0032] The first air inlet pipe 1-1 and the second air inlet pipe 2-1, the second air inlet pipe 2-1 and the liquid inlet 3-2, and the air outlet 3-3 and the second air outlet pipe 2-2 are connected by conduits.

[0033] Optionally, the primary heat exchanger 1 enables the gas entering the primary heat exchanger 1 to switch between 300K and 35K.

[0034] And / or, the secondary heat exchanger 2 enables the gas entering the secondary heat exchanger 2 to switch between 35K and 4K;

[0035] And / or, the three-stage heat exchanger 3 enables the gas entering the three-stage heat exchanger 3 to switch between 4K and 0.3 to 2K.

[0036] It should be noted that the system is cooled by a refrigeration unit 4. The raw gas to be treated, with a low helium-3 abundance of approximately 0.5%, enters sequentially from the first inlet pipe 1-1 into the first-stage heat exchanger 1, the second-stage heat exchanger 2, and the third-stage heat exchanger 3, where it is converted into superfluid helium. Within container 3-1 of the third-stage heat exchanger 3, the vapor pressure of helium-3 is much greater than that of helium-4. Therefore, the helium-3 content in the vapor within container 3-1 is greater than the helium-3 content in the solution. The gas is then extracted from the vapor, thus achieving helium-3 enrichment. Experiments have shown that helium-3 with an abundance of approximately 0.5% can be enriched to an abundance of 20%.

[0037] In one embodiment, the primary cold head 4-2 is connected to the primary heat exchanger 1 via an indium sheet, the secondary cold head 4-3 is connected to the secondary heat exchanger 2 via an indium sheet, and the tertiary cold head 4-4 is connected to the tertiary heat exchanger 3 via an indium sheet. It should be noted that, to increase thermal conductivity, thermal grease should be applied to the surface of the indium sheet during use.

[0038] In one embodiment, the raw gas to be treated is a mixture of helium-3 and helium-4, wherein the abundance of helium-3 in the mixture is 0.2% to 2%, preferably 0.5%. For example, it is 0.2%, 0.5%, 0.7%, 0.9%, 1%, 1.5%, 1.7%, or 2%.

[0039] Currently, enrichment techniques for helium-3 with an abundance of 0.5% include thermal flushing and superleaking. These methods require cooling the helium gas to below 2.17 K. However, below 2.17 K, helium-4 transforms into superfluid helium, a liquid with extremely low viscosity that can pass through very small pores, while helium-3 cannot. An entropy filter is a device with extremely small pores that allows superfluid helium to pass through while blocking helium-3, thus achieving helium-3 enrichment. To enrich helium-3 using this method, the superfluid helium in the containers at both ends of the entropy filter needs to be heated and vaporized after the chemical potential of the superfluid helium at both ends of the filter has reached equilibrium before it can be removed. Therefore, continuous operation is not possible. The vapor pressures of helium-3 and helium-4 differ significantly at low temperatures. At the same temperature, helium-3 evaporates more easily than helium-4, resulting in a higher abundance of helium-3 in the vapor than in the solution. By removing the helium-3 from the vapor, a certain amount of enriched helium-3 gas can be obtained. As helium-3 gas is continuously extracted, the helium-3 in the solution will continuously evaporate into the vapor, and the abundance of helium-3 in the solution will continuously decrease, which in turn will lead to a continuous decrease in the abundance of helium-3 in the vapor. Ultimately, the enrichment effect of helium-3 will deteriorate. Therefore, existing enrichment methods are difficult to operate continuously and cannot achieve continuous purification of helium-3.

[0040] Based on this, the helium-3 enrichment system in this embodiment also includes a helium-4 collection device 10, an entropy filter 6, an entropy filter drive heater 7, an superfluid helium-4 vaporization container 8, and a vaporization container heater 9, all located within the vacuum outer casing 4-5.

[0041] The container 3-1 has a liquid outlet 3-4 at its bottom; one end of the entropy filter 6 is connected to the liquid outlet 3-4 through a conduit, and the other end is connected to the superfluid helium-4 vaporization container 8 through a conduit; the entropy filter drive heater 7 is located between the entropy filter 6 and the superfluid helium-4 vaporization container 8, and is used to heat the conduit between the entropy filter 6 and the superfluid helium-4 vaporization container 8; the vaporization container heater 9 is located at the lower end of the superfluid helium-4 vaporization container 8, and is used to heat the superfluid helium-4 vaporization container 8; the helium-4 collection device 10 is connected to the superfluid helium-4 vaporization container 8 through a conduit.

[0042] In one embodiment, the average pore size of the filter medium of the entropy filter 6 is less than 100 nm, and the permeability coefficient is less than 1 × 10⁻⁶. -14 m 2 .

[0043] It should be noted that the filter medium of the entropy filter 6 of this invention is a porous medium, which is obtained by pressing or sintering alumina powder. This entropy filter only allows superfluids to pass through because superfluids have no viscosity. Driven by the entropy filter drive heater 7, superfluid helium-4 can flow through the entropy filter 6, while helium-3 cannot pass through. After flowing through the entropy filter 6, the superfluid helium-4 flows into the superfluid helium-4 vaporization container 8. Under the action of the vaporization container heater 9, the superfluid helium-4 vaporizes into gas, and finally, under the action of an external pump, the helium-4 gas is collected into the helium-4 collection device 10 through a conduit. With the entropy filter of this embodiment, superfluid helium-4 can be directly extracted from the container in a superfluid helium cryogenic environment, avoiding the damage to the cryogenic environment caused by heating, and thus avoiding the problem of the system being unable to continuously separate.

[0044] It should be noted that by using an external pump to extract the vapor, the amount of helium-3 extracted can be controlled by adjusting the pumping speed and the flow resistance of the extraction pipeline. Then, by dynamically adjusting the flow rate of superfluid helium-4 to match the vapor extraction rate, coordinated extraction of both can be achieved. When the total extracted flow rate equals the total inlet flow rate, the system's internal container remains stable, enabling this separation system to perform continuous and stable separation over extended periods. This method allows for continuous separation and extraction of helium-3, avoiding the drawbacks of systems that cannot operate continuously.

[0045] In one embodiment, when superfluid helium-4 flows through entropy filter 6, the flow rate of superfluid helium-4 flowing through entropy filter 6 is controlled by controlling the heating amount of entropy filter-driven heater 7 or the temperature of superfluid helium-4.

[0046] The present invention will be further described below with reference to specific embodiments.

[0047] Example 1

[0048] like Figure 1 As shown, a helium-3 enrichment system includes a primary heat exchanger 1, a secondary heat exchanger 2, a tertiary heat exchanger 3, a refrigeration device 4, and a helium-3 collection device 5.

[0049] The refrigeration device 4 includes a vacuum outer casing 4-5, a refrigeration unit 4-1, a primary cold head 4-2, a secondary cold head 4-3, and a tertiary cold head 4-4, which are located inside the vacuum outer casing 4-5 and connected in sequence to the refrigeration unit 4-1.

[0050] The first-stage heat exchanger 1 is thermally connected to the first-stage cold head 4-2 and is located inside the vacuum outer casing 4-5; the second-stage heat exchanger 2 is thermally connected to the second-stage cold head 4-3 and is located inside the vacuum outer casing 4-5; and the third-stage heat exchanger 3 is thermally connected to the third-stage cold head 4-4 and is located inside the vacuum outer casing 4-5.

[0051] The first-stage heat exchanger 1 is provided with a first air inlet pipe 1-1 and a first air outlet pipe 1-2. The second-stage heat exchanger 2 is provided with a second air inlet pipe 2-1 and a second air outlet pipe 2-2. The third-stage heat exchanger 3 is provided with a container 3-1. The container 3-1 is provided with a liquid inlet 3-2 and an air outlet 3-3. The air outlet 3-3 is located at the upper end of the third-stage heat exchanger 3.

[0052] The first inlet pipe 1-1 is connected to the raw gas to be treated, and the first outlet pipe 1-2 is connected to the helium-3 collection device 5.

[0053] The first air inlet pipe 1-1 and the second air inlet pipe 2-1, the second air inlet pipe 2-1 and the liquid inlet 3-2, and the air outlet 3-3 and the second air outlet pipe 2-2 are connected by conduits.

[0054] The primary heat exchanger 1 enables the gas entering the primary heat exchanger 1 to switch between 300K and 35K.

[0055] The secondary heat exchanger 2 enables the gas or liquid entering the secondary heat exchanger 2 to switch between 35K and 4K, thereby achieving the liquefaction or vaporization of the gas.

[0056] The three-stage heat exchanger 3 enables the gas entering the three-stage heat exchanger 3 to switch between 4K and 0.3~2K.

[0057] It should be noted that the system is cooled by a refrigeration unit 4. The raw gas to be treated, with a low helium-3 abundance of approximately 0.5%, enters sequentially from the first inlet pipe 1-1 into the first-stage heat exchanger 1, the second-stage heat exchanger 2, and the third-stage heat exchanger 3, where it is converted into superfluid helium. Within container 3-1 of the third-stage heat exchanger 3, the vapor pressure of helium-3 is much higher than that of helium-4. Therefore, the helium-3 content in the vapor within container 3-1 is greater than the helium-3 content in the solution. The gas is then extracted from the vapor, thus achieving helium-3 enrichment. Experiments have shown that a 0.5% helium-3 abundance can be enriched to 20%.

[0058] In this embodiment, the flow rate of gas or liquid flowing through the primary heat exchanger 1, the secondary heat exchanger 2, and the tertiary heat exchanger 3 is 1 SLM.

[0059] The first-stage cold head 4-2 is connected to the first-stage heat exchanger 1 via an indium sheet, the second-stage cold head 4-3 is connected to the second-stage heat exchanger 2 via an indium sheet, and the third-stage cold head 4-4 is connected to the third-stage heat exchanger 3 via an indium sheet.

[0060] The raw gas to be processed is a mixture of helium-3 and helium-4, with the abundance of helium-3 in the mixture being 0.5%. A flow resistance 11 for throttling and pressure reduction is also provided between the second gas inlet pipe 2-1 and the liquid inlet 3-2.

[0061] A helium mixture with low helium-3 abundance enters the primary heat exchanger 1, secondary heat exchanger 2, and tertiary heat exchanger 3 of this embodiment at a certain flow rate. It is ultimately converted into superfluid helium in the tertiary heat exchanger 3. Due to the difference in vapor pressure between helium-3 and helium-4, the helium-3 abundance of the vapor in the tertiary heat exchanger 3 is greater than that of the solution. The vapor is sequentially extracted from the second outlet pipe 2-2 and the first outlet pipe 1-2 by evacuation. Because the helium-3 abundance in the vapor is greater than that in the original gas, the amount of gas extracted is less than the inlet flow rate. Therefore, although this embodiment can effectively enrich helium-3, the liquid level in container 3-1 will continuously increase. When container 3-1 is filled with superfluid helium, the system cannot continue to operate.

[0062] Example 2

[0063] Unlike Example 1, as Figure 2 As shown, the helium-3 enrichment system in this embodiment also includes a helium-4 collection device 10, an entropy filter 6, an entropy filter drive heater 7, a superfluid helium-4 vaporization container 8, and a vaporization container heater 9, all located within the vacuum enclosure 4-5.

[0064] The container 3-1 has a liquid outlet 3-4 at its bottom; one end of the entropy filter 6 is connected to the liquid outlet 3-4 through a conduit, and the other end is connected to the superfluid helium-4 vaporization container 8 through a conduit; the entropy filter drive heater 7 is located between the entropy filter 6 and the superfluid helium-4 vaporization container 8, and is used to heat the conduit between the entropy filter 6 and the superfluid helium-4 vaporization container 8; the vaporization container heater 9 is located at the lower end of the superfluid helium-4 vaporization container 8, and is used to heat the superfluid helium-4 vaporization container 8; the helium-4 collection device 10 is connected to the superfluid helium-4 vaporization container 8 through a conduit.

[0065] The entropy filter 6 in this embodiment uses a filter medium made of pressed and sintered alumina, with an average pore size of 35 nm and a permeability coefficient of 1 × 10⁻⁶. -14 m 2 .

[0066] It should be noted that the entropy filter 6 of this invention is a porous medium. Under the drive of the entropy filter driving heater 7, superfluid helium-4 can flow through the entropy filter 6, while helium-3 cannot pass through the entropy filter. After flowing through the entropy filter 6, the superfluid helium-4 flows into the superfluid helium-4 vaporization container 8. Under the action of the vaporization container heater 9, the superfluid helium-4 vaporizes into gas. Finally, under the action of an external pump, the helium-4 gas is collected in the helium-4 collection device 10 through a conduit.

[0067] When superfluid helium-4 flows through entropy filter 6, the flow rate of superfluid helium-4 through entropy filter 6 is controlled by controlling the heating amount of entropy filter-driven heater 7 or the temperature of superfluid helium-4.

[0068] According to experimental measurements, the relationship between the flow rate and temperature of superfluid helium-4 when using the helium-3 enrichment system of this embodiment is shown in Table 1. The flow rate is measured in standard liters per minute (SLM). As can be seen from Table 1, the greater the heating capacity of the entropy filter-driven heater 7, the lower the temperature of superfluid helium-4, and the greater the flow rate of helium-4 extracted.

[0069] Table 1. Correspondence between temperature and flow rate of superfluid helium-4

[0070] Superfluid Helium-4 temperature Superfluid Helium-4 Flow Rate 1.65K 3.2SLM 1.70K 2.2SLM 1.75K 1.8SLM 1.80K 1.2LSM

[0071] Theoretically, the lower the temperature of the superfluid helium-4, the greater the flow rate through the entropy filter 6. However, when the temperature of the superfluid helium-4 is fixed, the heating amount of the entropy filter-driven heater 7 also affects the flow rate of the superfluid helium-4. Table 2 shows the relationship between the flow rate of the superfluid helium-4 and the heating amount of the entropy filter-driven heater 7 at a temperature of 1.65K. Table 3 shows the relationship between the flow rate of the superfluid helium-4 and the heating amount of the entropy filter-driven heater (7) at a temperature of 1.75K.

[0072] Table 2 shows the correspondence between the superfluid helium-4 flow rate and the heating amount of the entropy filter-driven heater (1.65K).

[0073]

[0074]

[0075] Table 3 shows the correspondence between the superfluid helium-4 flow rate and the heating amount of the entropy filter-driven heater (1.75K).

[0076] Drive heating amount flow 3.8mW 1.95SLM 15mW 2.5SLM 39mW 3SLM

[0077] As can be seen from Tables 1, 2, and 3, the flow rate of superfluid helium-4 can be controlled by adjusting the temperature of the superfluid helium-4 and the heating amount of the entropy filter-driven heater.

[0078] By matching the flow rate of superfluid helium-4 with the extraction rate of helium-3 vapor, coordinated extraction of both can be achieved. When the total extraction flow rate equals the total inlet flow rate, the internal container of the system remains stable, enabling the system to operate continuously and stably for extended periods. Therefore, this device can continuously extract and separate helium-3 and helium-4, avoiding the drawback of not being able to operate continuously.

[0079] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A helium-3 enrichment system, characterized in that, It includes a primary heat exchanger, a secondary heat exchanger, a tertiary heat exchanger, a refrigeration unit, and a helium-3 collection device. The refrigeration device includes a vacuum outer casing, a refrigeration unit, and a primary cold head, a secondary cold head, and a tertiary cold head disposed within the vacuum outer casing and connected in sequence to the refrigeration unit. The first-stage heat exchanger is thermally connected to the first-stage cold head and is located inside the vacuum casing; the second-stage heat exchanger is thermally connected to the second-stage cold head and is located inside the vacuum casing; the third-stage heat exchanger is thermally connected to the third-stage cold head and is located inside the vacuum casing. The first-stage heat exchanger is provided with a first air inlet pipe and a first air outlet pipe, the second-stage heat exchanger is provided with a second air inlet pipe and a second air outlet pipe, and the third-stage heat exchanger is provided with a container; the container is provided with a liquid inlet and an air outlet, with the air outlet located at the upper end of the third-stage heat exchanger. The first inlet pipe is connected to the raw gas to be treated, and the first outlet pipe is connected to the helium-3 collection device. The first air inlet pipe and the second air inlet pipe, the second air inlet pipe and the liquid inlet, and the air outlet and the second air outlet pipe are connected by conduits.

2. The helium-3 enrichment system according to claim 1, characterized in that: The primary heat exchanger enables the gas entering the primary heat exchanger to switch between 300K and 35K. And / or, the secondary heat exchanger enables the gas entering the secondary heat exchanger to switch between 35K and 4K; And / or, the three-stage heat exchanger enables the gas entering the three-stage heat exchanger to switch between 4K and 0.3 to 2K.

3. The helium-3 enrichment system according to claim 1, characterized in that: The first-stage cold head is connected to the first-stage heat exchanger via an indium sheet, the second-stage cold head is connected to the second-stage heat exchanger via an indium sheet, and the third-stage cold head is connected to the third-stage heat exchanger via an indium sheet.

4. The helium-3 enrichment system according to claim 1, characterized in that: The raw gas to be processed is a mixture of helium-3 and helium-4, with the abundance of helium-3 in the mixture ranging from 0.2% to 2%.

5. A helium-3 enrichment system according to claim 1, characterized in that: The continuous helium-3 enrichment system also includes a helium-4 collection device, an entropy filter, an entropy filter-driven heater, a superfluid helium-4 vaporization container, and a vaporization container heater, all located within the vacuum enclosure. The container has a liquid outlet at the bottom; one end of the entropy filter is connected to the liquid outlet via a conduit, and the other end is connected to the superfluid helium-4 vaporization container via a conduit; the entropy filter drive heater is located between the entropy filter and the superfluid helium-4 vaporization container to heat the conduit between the entropy filter and the superfluid helium-4 vaporization container; the vaporization container heater is located at the lower end of the superfluid helium-4 vaporization container to heat the superfluid helium-4 vaporization container; and the helium-4 collection device is connected to the superfluid helium-4 vaporization container via a conduit.

6. A helium-3 enrichment system according to claim 5, characterized in that: The flow rate of superfluid helium-4 flowing through the entropy filter is controlled by adjusting the heating amount of the heater driven by the entropy filter or by adjusting the temperature of the superfluid helium-4.

7. A helium-3 enrichment system according to claim 5, characterized in that: The entropy filter has an average pore size of less than 100 nm and a permeability coefficient of less than 1 × 10⁻⁶. -14 m 2 .

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