A method and system for extracting helium-3 from heavy water moderator mixed gas

Abstract

The present invention provides a method and system for extracting helium-3 from a heavy water moderator gas mixture. The extraction method includes a purification process, a cryogenic pre-distillation process, a cryogenic distillation process, and a dehydrogenation process. The extraction method of the present invention can extract helium-3 produced by tritium decay in the heavy water moderator, providing a new approach for obtaining helium-3 and thereby increasing helium-3 production. Furthermore, the helium-3 extraction method of the present invention has the advantages of an advanced process, a high degree of separation, and high-quality helium-3 gas. The helium-3 produced during the operation of the heavy water reactor can be fully recovered, thereby improving energy utilization.

Description

Technical Field

[0001] The present application relates to the field of chemical technology, and in particular to a method and system for extracting helium-3 from a heavy water moderator mixed gas. Background Art

[0002] Helium-3 is an isotope of helium with unique physical properties. It is increasingly being used in many fields such as neutron detection, cryogenic engineering, nuclear energy development, medicine, geography, and astronomy. It has become an important strategic material. Helium-3 is known as one of the most precious rare gases. The stable supply of high-quality helium-3 gas is one of the important supporting technologies for the development of quantum technology.

[0003] In the relevant technology, helium-3 is extremely rare, and there are few ways to obtain helium-3 and it is relatively difficult to obtain, which makes the output of helium-3 relatively low. Summary of the Invention

[0004] In view of this, the embodiments of the present application provide a method and system for extracting helium-3 from a heavy water moderator mixed gas, aiming to provide a new way to obtain helium-3 with lower difficulty, thereby increasing the yield of helium-3.

[0005] To achieve the above-mentioned objectives, an embodiment of the present application provides a method for extracting helium-3 from a heavy water moderator mixed gas, wherein the mixed gas includes a cover gas, and the cover gas is helium-4 gas. The method is characterized in that the method comprises:

[0006] Purification treatment: purifying the mixed gas containing helium-3 to remove water, water vapor, CO2, hydrocarbons, part of N2, part of O2 and part of hydrogen isotope combination gas in the mixed gas to obtain the first stage crude helium gas;

[0007] Cryogenic pre-distillation treatment: performing cryogenic pre-distillation treatment on the first-stage crude helium to remove residual N2 and O2 in the first-stage crude helium and obtain the second-stage crude helium;

[0008] Cryogenic distillation treatment: performing cryogenic distillation treatment on the second-stage crude helium to remove helium-4 gas from the second-stage crude helium and obtain third-stage crude helium;

[0009] Dehydrogenation treatment: performing dehydrogenation treatment on the crude helium gas of the third stage to remove the residual hydrogen isotope combination gas in the crude helium gas of the third stage.

[0010] In one embodiment, the helium-4 gas separated in the cryogenic distillation step is returned to the heavy water moderator system.

[0011] In one embodiment, the purification step specifically includes:

[0012] Catalytic oxidation treatment: performing catalytic oxidation treatment on the mixed gas containing helium-3 to remove trace amounts of hydrocarbons and some hydrogen isotope combination gases in the mixed gas and obtain a first mixture;

[0013] Cryogenic cooling treatment: performing a cryogenic cooling treatment on the first mixture to remove water and part of the water vapor in the first mixture and obtain a second mixture;

[0014] Low-temperature adsorption treatment: performing low-temperature adsorption treatment on the second mixture to remove CO2, part of N2, part of O2 and residual water vapor in the second mixture and obtain the first-stage crude helium.

[0015] In one embodiment, the dehydrogenation treatment step specifically includes:

[0016] Palladium membrane permeation treatment: performing palladium membrane permeation treatment on the crude helium gas of the third stage to remove part of the hydrogen isotope combination gas in the crude helium gas of the third stage and obtain the crude helium gas of the fourth stage;

[0017] Ultra-low temperature adsorption treatment: performing ultra-low temperature adsorption treatment on the crude helium gas of the fourth stage to remove residual hydrogen isotope combination gas in the crude helium gas of the fourth stage.

[0018] In one embodiment, the palladium membrane penetration treatment step specifically includes:

[0019] adding a quantitative amount of hydrogen to the crude helium gas in the third stage;

[0020] The third-stage crude helium gas to which a certain amount of hydrogen has been added is subjected to palladium membrane permeation to remove part of the hydrogen isotope combination gas in the third-stage crude helium gas.

[0021] In one embodiment, the low-temperature pre-distillation treatment step specifically includes:

[0022] At liquid nitrogen temperature, the first-stage crude helium is cryogenically pre-rectified using a first adsorption filler.

[0023] In one embodiment, the first adsorption filler includes at least one of a metal triangular spiral filler and a θ-ring filler.

[0024] In one embodiment, the first adsorption filler includes a metal triangular spiral filler, and the material of the metal triangular spiral filler includes at least one of stainless steel and copper.

[0025] In one embodiment, before the low-temperature pre-distillation step, the extraction method further comprises:

[0026] The first adsorption filler is subjected to a hydrophilic treatment.

[0027] In one embodiment, the cryogenic distillation treatment step specifically includes:

[0028] Under the temperature condition of 2K to 4K, the second stage crude helium is cryogenically distilled by using the second adsorption filler.

[0029] Another embodiment of the present application provides a system for extracting helium-3 from a heavy water moderator mixed gas, which is applicable to the method for extracting helium-3 from a heavy water moderator mixed gas described in any of the above embodiments. The extraction system comprises:

[0030] a purification treatment unit, comprising a catalytic oxidation treatment unit, a cryogenic cooling treatment unit, and a cryogenic adsorption treatment unit, wherein the catalytic oxidation treatment unit is used to perform catalytic oxidation treatment on the mixed gas containing helium-3 to remove trace hydrocarbons and some hydrogen isotope combination gases from the mixed gas and obtain a first mixture; the cryogenic cooling treatment unit is used to perform cryogenic cooling treatment on the first mixture to remove water and some water vapor from the first mixture and obtain a second mixture; and the cryogenic adsorption treatment unit is used to perform cryogenic adsorption treatment on the second mixture to remove CO2, some N2, some O2, and residual water vapor from the second mixture and obtain the first-stage crude helium gas;

[0031] a cryogenic pre-distillation treatment unit, configured to perform cryogenic pre-distillation treatment on the first-stage crude helium gas to remove residual N2 and O2 in the first-stage crude helium gas and obtain the second-stage crude helium gas;

[0032] a cryogenic distillation processing unit, configured to perform cryogenic distillation on the second-stage crude helium gas to remove helium-4 gas from the second-stage crude helium gas and obtain third-stage crude helium gas;

[0033] The dehydrogenation treatment unit includes a palladium membrane permeation treatment unit and an ultra-low temperature adsorption treatment unit. The palladium membrane permeation treatment unit is used to perform palladium membrane permeation treatment on the third-stage crude helium gas to remove part of the hydrogen isotope combination gas in the third-stage crude helium gas and obtain the fourth-stage crude helium gas; the ultra-low temperature adsorption treatment unit is used to perform ultra-low temperature adsorption treatment on the fourth-stage crude helium gas to remove residual hydrogen isotope combination gas in the fourth-stage crude helium gas.

[0034] The method for extracting helium-3 from a heavy water moderator gas mixture in an embodiment of the present application uses a mixed gas formed by mixing helium-3 produced by tritium decay in heavy water with a cover gas (helium-4) in a heavy water reactor as raw material. The mixed gas is sequentially subjected to purification, cryogenic pre-distillation, cryogenic distillation, and dehydrogenation treatments to gradually remove water, water vapor, CO2, N2, O2, hydrocarbons, helium-4 gas, and hydrogen isotope combination gas, thereby obtaining high-quality helium-3 gas. During the operation of the heavy water reactor, the mixed gas formed at the top layer can be fully utilized, thereby improving energy utilization. At the same time, the embodiment of the present application provides a new approach for obtaining helium-3, thereby increasing helium-3 production. Furthermore, the helium-3 extraction method of the embodiment of the present application has the advantages of advanced process flow, high separation degree, and high-quality helium-3 gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of a process for extracting helium-3 from a heavy water moderator gas mixture according to an embodiment of the present application;

[0036] Figure 2 This is a schematic flow chart of a method for extracting helium-3 from a heavy water moderator mixed gas according to another embodiment of the present application;

[0037] Figure 3 Schematic diagram of the structure of a system for extracting helium-3 from a heavy water moderator mixed gas according to an embodiment of the present application.

[0038] Description of Reference Numerals

[0039] 10. Purification treatment unit; 11. Catalytic oxidation treatment unit; 12. Cryogenic cooling treatment unit; 13. Cryogenic adsorption treatment unit; 20. Cryogenic pre-distillation treatment unit; 30. Cryogenic distillation treatment unit; 40. Dehydrogenation treatment unit; 41. Palladium membrane permeation treatment unit; 42. Ultra-low temperature adsorption treatment unit; 200. Heavy water moderator system. DETAILED DESCRIPTION

[0040] It should be noted that, unless there is a conflict, the embodiments and technical features in the embodiments of this application can be combined with each other, and the detailed description in the specific implementation method should be understood as an explanation of the purpose of this application and should not be regarded as an improper restriction on this application.

[0041] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] In related technologies, heavy water reactors (HWRs) use heavy water as both a moderator and coolant. During operation, deuterium in the heavy water absorbs neutrons and converts to tritium (tritium in HWRs is primarily contained in the moderator). In a HWR, the heavy water moderator requires helium-4 as a blanket gas. Tritium decays to produce helium-3, which resides in the blanket gas (helium-4), providing an alternative source of helium-3.

[0043] Based on this, Figure 1 As shown, an embodiment of the present application provides a method for extracting helium-3 from a heavy water moderator mixed gas.

[0044] It should be noted that heavy water is a compound composed of deuterium and oxygen, also known as deuterium oxide, with the molecular formula D2O.

[0045] There are three common isotopes of hydrogen in nature: protium (element symbol: H), deuterium (element symbol: D), and tritium (element symbol: T).

[0046] When heavy water is irradiated, deuterium absorbs neutrons to form tritium, which then decays to produce helium-3.

[0047] A gas mixture is formed on the top layer of the heavy water moderator. The gas mixture includes a cover gas, which is helium (helium-4).

[0048] It is understood that the mixed gas of the heavy water moderator includes, in addition to helium (helium-4) as a cover gas, helium-3, water, water vapor, and trace hydrocarbons (C x H y ), O2, H2, CO2, in addition, also includes a certain amount of O2, D2 (DT, HD, HT) produced by the radiolysis of water by tritium.

[0049] Specifically, the method for extracting helium-3 from the mixed gas at the top layer of the heavy water moderator includes:

[0050] S100, purification treatment: purifying the mixed gas containing helium-3 to remove water, water vapor, CO2, hydrocarbons, part of N2, part of O2 and part of hydrogen isotope combination gas in the mixed gas and obtain the first stage crude helium gas.

[0051] Hydrogen isotope combination gases include HD, HT, H2, D2, and DT.

[0052] S200, cryogenic pre-distillation treatment: performing cryogenic pre-distillation treatment on the first-stage crude helium to remove residual N2 and O2 in the first-stage crude helium and obtain the second-stage crude helium.

[0053] Specifically, by utilizing the difference in boiling points of different gases, the first-stage crude helium is cooled and liquefied under high pressure. The residual N2 and O2 in the first-stage crude helium can be liquefied at low temperatures, thereby achieving the purpose of separating them from the first-stage crude helium.

[0054] It is understandable that obtaining high pressure is easier than obtaining ultra-low temperature. Compared with normal pressure, the boiling points of N2 and O2 at high pressure are higher, so they are easier to liquefy.

[0055] After cryogenic pre-distillation, all heavy components relative to helium isotope gas in the first-stage crude helium can be reduced to below 1 ppm (parts per million). At this point, the second-stage crude helium contains relatively high-purity helium isotope gas (i.e., helium-3 gas and helium-4 gas).

[0056] The cryogenic pre-distillation process has the unique advantages of large processing capacity, high separation factor, and continuous operation. Therefore, in the embodiments of the present application, the production of helium-3 can be increased while improving the quality of the obtained helium-3 gas.

[0057] S300, cryogenic distillation treatment: performing cryogenic distillation treatment on the second-stage crude helium gas to remove helium-4 gas in the second-stage crude helium gas and obtain third-stage crude helium gas.

[0058] Helium-4 and helium-3 are isotopes, and it is difficult to separate helium-4 gas and helium-3 gas at one time. By using cryogenic distillation to separate and remove helium-4 gas alone, high-abundance helium-3 gas (abundance ≥ 99.96%) can be obtained.

[0059] S400, dehydrogenation treatment: dehydrogenation treatment is performed on the crude helium gas of the third stage to remove residual hydrogen isotope combination gas in the crude helium gas of the third stage.

[0060] It is understandable that, although the third-stage crude helium gas obtained after step S300 can produce high-abundance helium-3 gas, it is difficult to achieve a tritium concentration of less than 1.0×10 -11 %atom required.

[0061] The dehydrogenation step can remove the residual trace hydrogen isotope combination gas in the third stage crude helium, thereby reducing the tritium concentration in the helium-3 gas to 1.0×10 -11 % atom or less, thus obtaining high-quality helium-3 gas with a purity of ≥99.9999%, an abundance of ≥99.96%, an impurity content of less than 1ppm, and a tritium content of ≤1.0×10 -11 %atom.

[0062] The method for extracting helium-3 from a heavy water moderator gas mixture in an embodiment of the present application uses a mixed gas formed by mixing helium-3 produced by tritium decay in heavy water with a cover gas (helium-4) in a heavy water reactor as raw material. The mixed gas is sequentially subjected to purification, cryogenic pre-distillation, cryogenic distillation, and dehydrogenation treatments to gradually remove water, water vapor, CO2, N2, O2, hydrocarbons, helium-4 gas, and hydrogen isotope combination gas, thereby obtaining high-quality helium-3 gas. During the operation of the heavy water reactor, the mixed gas formed at the top layer can be fully utilized, thereby improving energy utilization. At the same time, the embodiment of the present application provides a new approach for obtaining helium-3, thereby increasing helium-3 production. Furthermore, the helium-3 extraction method of the embodiment of the present application has the advantages of advanced process flow, high separation degree, and high-quality helium-3 gas.

[0063] like Figure 3 As shown, in some embodiments, the helium-4 gas separated in the cryogenic distillation step is returned to the heavy water moderator system 200.

[0064] In this way, the helium-4 gas can return to the heavy water moderator system 200 and be used as a covering gas. During the operation of the heavy water reactor, the covering gas of the heavy water moderator can be replenished, thereby better isolating the air and reducing the entry of oxygen into the heavy water moderator, thereby reducing corrosion of the system.

[0065] In some embodiments, the low-temperature pre-distillation treatment step specifically includes:

[0066] At liquid nitrogen temperature, the first stage crude helium is cryogenically pre-rectified using the first adsorption filler.

[0067] The first adsorption filler can adsorb the target substance and utilize the principle of cryogenic distillation to more thoroughly separate and remove the heavy components (equivalent to helium-3) in the first-stage crude helium gas, thereby obtaining the second-stage crude helium gas.

[0068] It can be understood that the second-stage crude helium gas includes light components of helium-3 gas, helium-4 gas and hydrogen isotope combination gas containing trace amounts of tritium.

[0069] It should be noted that the type of the first adsorption filler is not limited. For example, in some embodiments, the first adsorption filler includes at least one of a metal triangular spiral filler and a θ-ring filler.

[0070] That is to say, the first adsorption filler may be entirely metal triangular spiral fillers, entirely θ-ring fillers, or partially metal triangular spiral fillers and partially θ-ring fillers.

[0071] Of course, the first adsorption filler can also be other fillers with the same characteristics.

[0072] The metal triangular spiral packing has the advantages of being resistant to cold and heat, having a large porosity, a large flux, a low pressure drop, low resistance, a good separation effect, and a long service life. In this way, it can better achieve the separation of helium-3 gas and can be reused repeatedly, thereby reducing the cost of obtaining helium-3 gas.

[0073] Theta ring packing is also known as Dixon packing. Theta ring packing has a large specific surface area and tortuous flow paths, which increase the gas-liquid mass transfer area and evenly distribute the fluid, thereby improving separation efficiency. Furthermore, the high porosity of theta ring packing reduces flow resistance, shortens the fluid's residence time in the packing, and reduces energy consumption, thereby enhancing the extraction efficiency of helium-3.

[0074] In some embodiments, the first adsorption filler includes a metal triangular spiral filler, and the material of the metal triangular spiral filler includes at least one of stainless steel and copper.

[0075] In some embodiments, before the low-temperature pre-distillation step, the extraction method further comprises:

[0076] The first adsorption filler is subjected to a hydrophilic treatment.

[0077] By performing a hydrophilic treatment on the first adsorption filler, the heat transfer, mass transfer and separation effects during the cryogenic pre-distillation process can be enhanced, thereby better removing gases other than helium isotope gas.

[0078] In some embodiments, the cryogenic distillation treatment step specifically includes:

[0079] Under the temperature condition of 2K to 4K, the second stage crude helium is cryogenically distilled using the second adsorption filler.

[0080] The type of the second adsorption filler is not limited and is similar to the first adsorption filler.

[0081] The cryogenic distillation process is primarily used to separate helium-3 from helium-4. Cryogenic distillation of helium isotopes requires low temperatures between 2K and 4K.

[0082] It is understandable that in order to meet the temperature and cooling capacity requirements of cryogenic distillation, GM refrigeration and throttling and decompression technology can be used in combination to provide a cryogenic refrigeration system with a 2K temperature zone and a certain cooling power; thermal insulation protection measures combining a high vacuum cold box with a multi-stage radiation-proof cold screen are used to minimize the impact of heat and cold leakage in the system on the cryogenic distillation process; the helium vapor required for the cryogenic distillation process and the condensation and reflux of the helium vapor will be achieved respectively by superfluid helium condensers.

[0083] Through the low-temperature distillation process at a temperature of 2K to 4K, not only can helium-3 and helium-4 in helium isotope gas be separated, but the low-temperature adsorption function of the second adsorption filler can also be utilized to further remove heavy components and hydrogen isotope combination gases in the helium-3 gas.

[0084] like Figure 2 As shown, in some embodiments, the purification step specifically includes:

[0085] S110, catalytic oxidation treatment: catalytic oxidation treatment is performed on the mixed gas containing helium-3 to remove trace amounts of hydrocarbons and some hydrogen isotope combination gases in the mixed gas and obtain a first mixture.

[0086] It should be noted that the cover gas (helium-4 gas) itself will introduce trace amounts of hydrocarbons (C x H y ), O2, H2, CO2. At the same time, during the operation of the heavy water reactor, a certain amount of O2 and D2 (DT, HD, HT) are generated in the heavy water moderator due to the radiolysis of water by tritium.

[0087] Hydrocarbons and hydrogen isotope combination gases are both organic compounds and are easily catalytically oxidized. Therefore, hydrocarbons and most hydrogen isotope combination gases can be removed through catalytic oxidation treatment steps.

[0088] S120, low-temperature cooling treatment: performing low-temperature cooling treatment on the first mixture to remove water and part of water vapor in the first mixture and obtain a second mixture.

[0089] It can be understood that the boiling point of water vapor is very different from the boiling point of other gases such as CO2 in the first mixture. Therefore, through the low-temperature cooling treatment step, the water vapor can be liquefied relatively easily and condensed with the water in the first mixture in the form of mist to form relatively large liquid droplets, which can then be removed.

[0090] S130, low-temperature adsorption treatment: performing low-temperature adsorption treatment on the second mixture to remove CO2, part of N2 and part of O2, as well as residual water vapor in the second mixture and obtain first-stage crude helium.

[0091] like Figure 2 As shown, in some embodiments, the catalytic oxidation treatment step specifically includes:

[0092] Under high temperature conditions, the mixed gas is controlled to pass into the copper oxide so that the copper oxide and the C x H y , hydrogen isotope combination gas produces redox reaction.

[0093] Copper oxide has strong reducing properties. After the hydrogen isotope combination gas and hydrocarbons produce an oxidation-reduction reaction with copper oxide, the hydrogen isotope combination gas is converted into water or water vapor, and the hydrocarbons are converted into CO2 and H2O. Water, water vapor and CO2 can be removed through subsequent low-temperature cooling treatment steps and low-temperature adsorption treatment steps.

[0094] That is, through the catalytic oxidation treatment step, hydrocarbons and hydrogen isotope combination gases that are difficult to remove can be converted into substances that are easier to remove, thereby reducing the difficulty of obtaining high-quality helium-3 gas.

[0095] In some embodiments, the cryogenic cooling step specifically includes:

[0096] The first mixture is controlled to flow through chilled water for low temperature cooling.

[0097] That is, in the low-temperature cooling step, the cooling source is chilled water, and the temperature of the chilled water can be between -10°C and -5°C, thereby improving the liquefaction efficiency of the water vapor.

[0098] In some embodiments, the low temperature adsorption treatment step specifically includes:

[0099] The second mixture is cryogenically adsorbed by a cryogenic adsorption material at a liquid nitrogen temperature.

[0100] Specifically, the temperature of liquid nitrogen can reach below -196°C, so that CO2, N2, O2 and residual water vapor after the low-temperature cooling treatment step can be better absorbed by the low-temperature adsorption material.

[0101] It should be noted that the type of low-temperature adsorption material is not limited. For example, in some embodiments, the low-temperature adsorption material includes at least one of molecular sieve and activated carbon.

[0102] That is to say, the low-temperature adsorption material can be entirely molecular sieve, entirely activated carbon, or partly molecular sieve and partly activated carbon.

[0103] For example, molecular sieves are used for low-temperature adsorption. Small molecules can pass through the molecular sieve, thereby removing CO2 and water vapor. At the same time, due to the low-temperature adsorption process at liquid nitrogen temperature, the molecular sieve can also filter out some N2 and O2.

[0104] like Figure 2 As shown, in some embodiments, the dehydrogenation treatment step specifically includes:

[0105] S410, palladium membrane permeation treatment: palladium membrane permeation treatment is performed on the third-stage crude helium gas to remove part of the hydrogen isotope combination gas in the third-stage crude helium gas and obtain the fourth-stage crude helium gas.

[0106] Specifically, the hydrogen isotope combination gas in the third stage crude helium gas can penetrate to the other side of the palladium membrane, while helium-3 gas has difficulty passing through the palladium membrane. In this way, most of the hydrogen isotope combination gas can be removed.

[0107] S420, ultra-low temperature adsorption treatment: ultra-low temperature adsorption treatment is performed on the fourth-stage crude helium gas to remove residual hydrogen isotope combination gas in the fourth-stage crude helium gas.

[0108] To improve the quality of helium-3 gas, trace hydrogen isotope combinations may be present in the fourth-stage crude helium gas obtained after palladium membrane permeation treatment. Ultra-low temperature adsorption treatment can further remove these trace hydrogen isotope combinations in the fourth-stage crude helium gas, thereby improving the quality of helium-3 gas.

[0109] In some embodiments, the palladium membrane permeation treatment step specifically includes:

[0110] Adding a certain amount of hydrogen to the crude helium gas in the third stage;

[0111] The third-stage crude helium gas to which a certain amount of hydrogen has been added is subjected to palladium membrane permeation to remove part of the hydrogen isotope combination gas in the third-stage crude helium gas.

[0112] It should be noted that the added hydrogen is H2. In this way, during the palladium membrane permeation treatment step, the gas pressure on both sides of the palladium membrane can be balanced, thereby allowing trace tritium and hydrogen-containing hydrogen isotope combination gases in the third-stage crude helium gas to pass through the palladium membrane and permeate to the other side of the palladium membrane for removal.

[0113] It is understandable that a small amount of the hydrogen added to the crude helium gas of the third stage will remain in the crude helium gas of the fourth stage. Through the ultra-low temperature adsorption treatment step, the residual trace hydrogen in the crude helium gas of the fourth stage can be removed, thereby ultimately obtaining high-quality helium-3 gas.

[0114] In some embodiments, the ultra-low temperature adsorption treatment step specifically includes:

[0115] Under the condition of temperature below 0.1K, ultra-low temperature adsorption material is used to perform ultra-low temperature adsorption on the fourth stage crude helium.

[0116] A temperature below 0.1K, or -273.05°C, is close to the temperature of liquid helium. Under these conditions, the remaining trace hydrogen in the fourth-stage crude helium can be largely removed, while the helium-3 gas is retained, thus improving the quality of the resulting helium-3 gas.

[0117] Another embodiment of the present application provides a system for extracting helium-3 from a heavy water moderator gas mixture. The helium-3 extraction system is applicable to the helium-3 extraction method of any of the above embodiments.

[0118] like Figure 3 As shown, the extraction system includes a purification processing unit 10 , a cryogenic pre-distillation processing unit 20 , a cryogenic distillation processing unit 30 and a dehydrogenation processing unit 40 .

[0119] The purification treatment unit 10 includes a catalytic oxidation treatment unit 11 , a low-temperature cooling treatment unit 12 , and a low-temperature adsorption treatment unit 13 .

[0120] The catalytic oxidation treatment unit 11 is used to perform catalytic oxidation treatment on the mixed gas containing helium-3 to remove trace hydrocarbons and some hydrogen isotope combination gases in the mixed gas and obtain a first mixture.

[0121] Specifically, the catalytic oxidation unit can be a catalytic oxidation column, which contains copper oxide. The mixed gas containing helium-3 passes through the catalytic oxidation column. At high temperature, the copper oxide reacts with the hydrocarbons (C x H y ) and hydrogen isotope combination gas undergo redox reaction, thereby removing hydrocarbons (C x H y ) and hydrogen isotope combination gas (H2, D2, HD, DT, HT), the mixed gas becomes a first mixture after passing through the catalytic oxidation column.

[0122] The low-temperature cooling treatment unit 12 is used to perform low-temperature cooling treatment on the first mixture to remove water and part of water vapor in the first mixture and obtain a second mixture.

[0123] Specifically, the low-temperature cooling treatment unit 12 can be a low-temperature condenser, in which chilled water flows. The temperature of the chilled water can be between -10°C and -5°C. In this way, the water and water vapor in the first mixture can be condensed and separated and removed. The first mixture becomes the second mixture after passing through the low-temperature condenser.

[0124] The low-temperature adsorption processing unit 13 is used to perform low-temperature adsorption processing on the second mixture to remove CO 2 , part of N 2 , part of O 2 and residual water vapor in the second mixture and obtain first-stage crude helium.

[0125] Specifically, the cryogenic adsorption processing unit 13 can be a cryogenic adsorber or a cryogenic adsorption column. Exemplarily, the cryogenic adsorption processing unit 13 is a cryogenic adsorber filled with at least one of a molecular sieve and activated carbon. The cryogenic adsorber utilizes the principle of cryogenic adsorption to further separate and remove water vapor and a portion of N2, O2, and CO2 from the second mixture. After these gases are separated from the second mixture, the second mixture becomes the first-stage crude helium.

[0126] The cryogenic pre-distillation treatment unit 20 is used to perform cryogenic pre-distillation treatment on the first-stage crude helium gas to remove residual N 2 and O 2 in the first-stage crude helium gas and obtain the second-stage crude helium gas.

[0127] Specifically, the cryogenic pre-distillation processing unit 20 can be a cryogenic pre-distillation tower filled with a first adsorbent filler. Using the principle of cryogenic distillation at liquid nitrogen temperatures, the heavy components (relative to helium isotopes) contained in the first-stage crude helium gas are more thoroughly removed, and the second-stage crude helium gas is obtained at the top of the cryogenic pre-distillation tower.

[0128] It can be understood that the second-stage crude helium gas includes light-component helium-3 gas, helium-4 gas, and hydrogen isotope combination gas containing trace amounts of tritium.

[0129] The first adsorption filler may be treated to be hydrophilic, thereby enhancing the heat transfer, mass transfer and separation effects of the low-temperature pre-distillation process.

[0130] It should be noted that the type of the first adsorption filler is not limited, and can be, for example, at least one of a metal triangular spiral filler and a θ-ring filler.

[0131] When the first adsorption filler includes a metal triangular spiral filler, the material of the metal triangular spiral filler includes at least one of stainless steel and copper.

[0132] It should be noted that the heavy component (relative to the helium isotope gas) in the second-stage crude helium gas is below 1 ppm.

[0133] The cryogenic distillation treatment unit 30 is used to perform cryogenic distillation treatment on the second-stage crude helium gas to remove helium-4 gas from the second-stage crude helium gas and obtain third-stage crude helium gas.

[0134] Specifically, the cryogenic distillation processing unit 30 can be a cryogenic distillation tower, which is filled with a second adsorption filler. Under temperature conditions of 2K to 4K, the principle of cryogenic distillation is used to separate helium-3 and helium-4 in the helium isotope gas. The light component helium-3 gas (high-abundance helium-3 product) is obtained at the top of the cryogenic distillation tower, and the heavy component helium-4 gas is obtained at the bottom of the cryogenic distillation tower. The helium-4 gas can be returned to the heavy water moderator to continue to be used as a cover gas.

[0135] The type of the second adsorption filler is not limited and can be selected with reference to the first adsorption filler.

[0136] It should be noted that the cryogenic distillation separation of helium isotope gas needs to be carried out under low temperature conditions of 2K to 4K. In order to meet the temperature and cooling capacity requirements of cryogenic distillation, GM refrigeration and throttling and decompression technology can be comprehensively used to provide a low-temperature refrigeration system with a 2K temperature range and a certain cooling power; an insulation protection measure combining a high vacuum cold box with a multi-stage radiation-proof cold screen is adopted to minimize the impact of heat and cold leakage of the system on the cryogenic distillation process; the helium vapor required for the cryogenic distillation process and the condensation and reflux of the helium vapor will be realized by an electric heating reboiler placed at the bottom of the cryogenic distillation tower and a superfluid helium condenser placed at the top of the cryogenic distillation tower, respectively.

[0137] Through the low-temperature distillation process at a temperature of 2K to 4K, not only can helium-3 and helium-4 in helium isotope gas be separated, but the second adsorption filler in the low-temperature distillation tower can also utilize the low-temperature adsorption function to further remove heavy components and hydrogen isotope combination gas in the helium-3 gas.

[0138] The dehydrogenation treatment unit 40 includes a palladium membrane permeation treatment unit 41 and an ultra-low temperature adsorption treatment unit 42 .

[0139] The palladium membrane permeation treatment unit 41 is used to perform palladium membrane permeation treatment on the third-stage crude helium gas to remove part of the hydrogen isotope combination gas in the third-stage crude helium gas and obtain the fourth-stage crude helium gas.

[0140] Specifically, the type of the palladium membrane permeation treatment unit 41 is not limited, and can be, for example, a self-supporting palladium membrane or a supported palladium membrane.

[0141] A certain amount of hydrogen is added to the third-stage crude helium at the top of the cryogenic distillation tower to maintain the pressure balance during the palladium membrane permeation treatment. The palladium membrane permeation treatment unit 41 can separate and remove trace tritium and hydrogen-containing hydrogen isotope combination gas in the third-stage crude helium.

[0142] The ultra-low temperature adsorption processing unit 42 is used to perform ultra-low temperature adsorption processing on the fourth-stage crude helium gas to remove residual hydrogen isotope combination gas in the fourth-stage crude helium gas.

[0143] Specifically, the ultra-low temperature adsorption processing unit 42 can be an ultra-low temperature adsorption column, which is filled with ultra-low temperature adsorption material. Under the condition of a temperature below 0.1K, the ultra-low temperature adsorption material is used to separate and remove the residual trace hydrogen in the fourth-stage crude helium gas, thereby obtaining high-quality helium-3 gas.

[0144] The helium-3 extraction system of the embodiment of the present application finally obtains helium-3 gas with a purity of ≥99.9999%, an abundance of ≥99.96%, an impurity content of less than 1ppm, and a tritium content of ≤1.0×10 -11 %atom.

[0145] In the description of this application, the descriptions with reference to the terms "in one embodiment", "in some embodiments", "in other embodiments", "in yet other embodiments", or "exemplary" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiments of the present application. In this application, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine different embodiments or examples described in this application and features of different embodiments or examples, unless they are mutually inconsistent.

[0146] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Persons skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application are intended to be within the scope of protection of the present application.

Claims

1. A method for extracting helium-3 from a heavy water moderator mixed gas, wherein the mixed gas includes a cover gas, and the cover gas is helium-4 gas, characterized in that: The extraction method comprises: Purification treatment: purifying the mixed gas containing helium-3 to remove water, water vapor, CO2, hydrocarbons, part of N2, part of O2 and part of hydrogen isotope combination gas in the mixed gas to obtain the first stage crude helium gas; Cryogenic pre-distillation treatment: At liquid nitrogen temperature, the first-stage crude helium gas is cryogenically pre-distilled using a first adsorption filler to remove residual N2 and O2 in the first-stage crude helium gas and obtain the second-stage crude helium gas; Cryogenic distillation: Under the temperature condition of 2K to 4K, the second stage crude helium gas is cryogenically distilled using the second adsorption filler to remove the helium-4 gas in the second stage crude helium gas and obtain the third stage crude helium gas; Palladium membrane permeation treatment: adding a certain amount of hydrogen to the crude helium gas of the third stage, and performing palladium membrane permeation on the crude helium gas of the third stage to which the certain amount of hydrogen has been added, so as to remove part of the hydrogen isotope combination gas in the crude helium gas of the third stage and obtain the crude helium gas of the fourth stage; Ultra-low temperature adsorption treatment: Under the condition of a temperature below 0.1K, ultra-low temperature adsorption material is used to perform ultra-low temperature adsorption on the crude helium gas of the fourth stage to remove the residual hydrogen isotope combination gas in the crude helium gas of the fourth stage.

2. The extraction method according to claim 1, wherein The helium-4 gas separated in the cryogenic distillation step is returned to the heavy water moderator system.

3. The extraction method according to claim 1, wherein The purification step specifically includes: Catalytic oxidation treatment: performing catalytic oxidation treatment on the mixed gas containing helium-3 to remove trace amounts of hydrocarbons and some hydrogen isotope combination gases in the mixed gas and obtain a first mixture; Cryogenic cooling treatment: performing a cryogenic cooling treatment on the first mixture to remove water and part of the water vapor in the first mixture and obtain a second mixture; Low-temperature adsorption treatment: performing low-temperature adsorption treatment on the second mixture to remove CO2, part of N2, part of O2 and residual water vapor in the second mixture and obtain the first-stage crude helium.

4. The extraction method according to claim 1, wherein The first adsorption filler includes at least one of a metal triangular spiral filler and a θ ring filler; and / or, The first adsorption filler includes a metal triangular spiral filler, and the material of the metal triangular spiral filler includes at least one of stainless steel and copper.

5. The extraction method according to claim 1, wherein Before the low-temperature pre-distillation treatment step, the extraction method further comprises: The first adsorption filler is subjected to a hydrophilic treatment.

6. A system for extracting helium-3 from a heavy water moderator mixed gas, to which the method for extracting helium-3 from a heavy water moderator mixed gas according to any one of claims 1 to 5 is applicable, the extraction system comprising: a purification treatment unit, comprising a catalytic oxidation treatment unit, a cryogenic cooling treatment unit, and a cryogenic adsorption treatment unit, wherein the catalytic oxidation treatment unit is used to perform catalytic oxidation treatment on the mixed gas containing helium-3 to remove trace hydrocarbons and some hydrogen isotope combination gases from the mixed gas and obtain a first mixture; the cryogenic cooling treatment unit is used to perform cryogenic cooling treatment on the first mixture to remove water and some water vapor from the first mixture and obtain a second mixture; and the cryogenic adsorption treatment unit is used to perform cryogenic adsorption treatment on the second mixture to remove CO2, some N2, some O2, and residual water vapor from the second mixture and obtain the first-stage crude helium gas; a cryogenic pre-distillation treatment unit, configured to perform cryogenic pre-distillation treatment on the first-stage crude helium gas to remove residual N2 and O2 in the first-stage crude helium gas and obtain the second-stage crude helium gas; a cryogenic distillation processing unit, configured to perform cryogenic distillation on the second-stage crude helium gas to remove helium-4 gas from the second-stage crude helium gas and obtain third-stage crude helium gas; a dehydrogenation treatment unit, comprising a palladium membrane permeation treatment unit and an ultra-low temperature adsorption treatment unit, wherein the palladium membrane permeation treatment unit is used to perform palladium membrane permeation treatment on the crude helium gas of the third stage to remove part of the hydrogen isotope combination gas in the crude helium gas of the third stage and obtain the crude helium gas of the fourth stage; The ultra-low temperature adsorption processing unit is used to perform ultra-low temperature adsorption processing on the fourth-stage crude helium gas to remove residual hydrogen isotope combination gas in the fourth-stage crude helium gas.

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