Hydrogen and helium separation and purification process

Abstract

The invention relates to the technical field of helium purification, in particular to a hydrogen and helium separation and purification process. Separating and purifying by adopting a rotating wheel type adsorber, wherein a rotating wheel area of the rotating wheel type adsorber is divided into a dehydrogenation area, an oxygenating area and a replacement area; a rotating wheel area of the rotating wheel type adsorber is filled with a dehydrogenation material; the hydrogen and helium separation and purification process comprises the following steps: preheating hydrogen-containing helium-rich gas, enabling the preheated helium-rich gas to enter a dehydrogenation zone, enabling hydrogen and oxygen in the helium-rich gas to react on a reaction bed layer, dehydrating generated tail gas, and collecting the dehydrated tail gas as dehydrogenated helium; a reaction bed layer of the dehydrogenation area is transferred to an oxygen supplementing area, helium containing oxygen is used, and waste heat of a dehydrogenation material is used for supplementing oxygen on the surface; the reaction bed layer is further transferred to a replacement area, and regeneration is completed. According to the separation and purification process, a rotating wheel type adsorber is utilized to adopt a chemical circulation mode, the reduction process and the oxidation process are mutually independent, no oxygen enters in the dehydrogenation process, subsequent treatment is not needed, and the technological process is simplified.

Description

Technical Field

[0001] This invention relates to the field of helium purification technology, and more particularly to a hydrogen-helium separation and purification process. Background Technology

[0002] Helium (He) is a rare monatomic inert gas widely used in aerospace, medical, refrigeration, and welding fields. However, helium is extremely rare in nature, accounting for only 0.0005% of the total atmospheric content, and mainly exists as a dissolved component in natural gas, typically below 0.05% (v / v). Therefore, separating and extracting helium from natural gas requires complex processes and incurs high investment costs. With the rapid development of the liquefied natural gas (LNG) industry, LNG has become an important source of helium. During storage and transportation, LNG generates cryogenic flash gas (BOG), a component in LNG that is not easily liquefied and gradually accumulates within the LNG. The main components of BOG are methane, nitrogen, helium, and hydrogen. To separate and extract He from BOG, CH4 and N2 can be removed from the BOG using cryogenic distillation or membrane separation methods, and then He can be separated and purified from the remaining He- and H2-rich tail gas. Because CH4 and some H2 in BOG undergo complete combustion with O2 from the purified air obtained through air separation, producing water and carbon dioxide, the H2 content in BOG is relatively high, typically exceeding 4%. To separate and extract high-purity He from BOG, the H2 in the H2-rich He tail gas needs to be removed first. A common method is to add excess O2 to catalytically convert H2 to H2O. However, this method carries certain safety risks because the reaction between H2 and O2 is exothermic; when the H2 content is high, the reaction temperature rises, potentially leading to catalyst deactivation or an explosion. Therefore, safely and effectively removing H2 from H2-rich He tail gas and purifying it to high-purity He remains a significant technical challenge.

[0003] To address this technical challenge, relevant literature and patents have proposed different methods and apparatuses. Patent document CN118371098A discloses a helium extraction system, comprising a membrane separation helium enrichment system, an LNG plant, and a helium purification system connected sequentially via pipelines. The problem with this method is the need for high-pressure, multi-stage separation; therefore, higher gas purity results in higher energy consumption. Patent document CN115872371A proposes a method and system for purifying ultrapure helium. The raw material gas is contacted with oxygen to allow hydrogen in the raw material gas to react with oxygen, yielding a catalytically dehydrogenated gas. This gas is then subjected to cryogenic separation and membrane separation sequentially to obtain a membrane-separated gas. This membrane-separated gas is then chemically dehydrogenated, followed by temperature-switched adsorption to obtain ultrapure helium. However, this method is overly complex in terms of process flow, and the subsequent oxygen replenishment process using metal oxides increases unnecessary energy consumption. Summary of the Invention

[0004] This invention provides a hydrogen-helium separation and purification process to solve the aforementioned technical problems existing in existing hydrogen-helium separation and purification processes.

[0005] According to a first aspect of the present invention, the present invention provides a hydrogen-helium separation and purification process, which employs a rotary adsorber for separation and purification. The rotor of the rotary adsorber is divided into a dehydrogenation zone, an oxygen replenishment zone, and a displacement zone; the rotor of the rotary adsorber is equipped with a dehydrogenation material. The hydrogen-helium separation and purification process includes the following steps: Step (1): After preheating, the hydrogen-rich helium gas is introduced into the dehydrogenation zone, so that the hydrogen and oxygen in the helium-rich gas react on the reaction bed. The tail gas produced is dehydrated and collected as dehydrogenated helium. Step (2): Transfer the reaction bed in the dehydrogenation zone to the oxygen replenishment zone, and use helium containing oxygen to replenish the surface oxygen using the residual heat of the dehydrogenation material; Step (3): The reaction bed is further transferred to the replacement zone, and the air on the surface of the material is replaced by dehydrogenated helium to complete the regeneration.

[0006] Furthermore, the dehydrogenation material includes a support and a bimetallic carbide supported on the support.

[0007] Furthermore, the carrier is a carbon-based material that has undergone oxidation treatment. Preferably, the specific surface area of ​​the carrier is 800–2000 m². 2 / g; the bulk density of the support is 0.2-0.4 kg / L. The support can be modified graphene, modified carbon nanotubes, modified carbon black, and modified biochar, etc.

[0008] Surface oxidation treatment of carbon-based materials is mainly aimed at improving their surface properties and enhancing their interactions with other substances. Oxidation methods include hot air oxidation, nitric acid oxidation, and chemical treatment.

[0009] Hot air oxidation method: Taking carbon nanotubes as an example, air oxidation is used for treatment at a temperature of 140-160℃ (preferably 150℃) and a treatment time of 12-36h (preferably 24h) to obtain surface-oxidized carbon nanotubes. The treated sample shows a significant increase in the content of oxygen-containing functional groups in air, with each carbon atom containing an average of 0.27 hydroxyl groups, 0.49 carbonyl groups, and 0.51 aldehyde groups.

[0010] Nitric acid oxidation method: Taking multi-walled carbon nanotubes as an example, a mild oxidation treatment is carried out using a 3-8% (preferably 5%) nitric acid solution at a treatment temperature of 70-90℃ (preferably 80℃) and a treatment time of 1-3 hours (preferably 2 hours) to obtain surface-oxidized multi-walled carbon nanotubes.

[0011] Chemical treatment method: Taking carbon black as an example, oxidation treatment is carried out by immersion. The carbon black is immersed in potassium permanganate solution at a treatment temperature of 80-100℃ (preferably 90℃) and a treatment time of 1-3 hours (preferably 2 hours) to obtain surface oxidized carbon black.

[0012] After the above surface oxidation treatment, an oxide layer will be formed on the surface of the carbon-based material.

[0013] Then, bimetallic carbides such as NiMoC and CoMoC are loaded onto the support as active centers for the dissociation and adsorption of H2, accounting for 5-15% of the total mass fraction of the dehydrogenation material. In some specific embodiments, the bimetallic carbides account for 7-9% of the total mass of the dehydrogenation material.

[0014] Taking NiMoC as an example, NiMoC / C dehydrogenation materials are prepared using the gas-phase carbothermal reduction method: First, nickel nitrate and ammonium molybdate are dissolved in water, and then they are loaded onto a carrier using an impregnation method.

[0015] Impregnation methods are generally conventional methods such as equal-volume impregnation. Taking equal-volume impregnation as an example, a noble metal solution with a volume equal to the pore volume of the carrier (measured) is prepared. The amount of noble metal to be added is calculated according to the mass ratio of the carrier to the noble metal. The solution is then evenly dripped onto the carrier, allowing the impregnation solution to uniformly enter the pores.

[0016] The drying temperature is 100-150℃ and the time is 12-24 hours; the calcination temperature is 200-300℃ and the time is 2-4 hours.

[0017] The precursor-loaded material was then placed in a high-temperature reactor and subjected to a carbothermic reduction reaction under a hydrogen atmosphere and high temperature to obtain bimetallic carbide catalyst powder. The hydrogen concentration was 10%–20% of the total volume, with the remainder being inert gases. The high temperature was increased from room temperature to 600–750°C at a rate of 1–2°C per minute and maintained for 1–2 hours.

[0018] Further, in step (1), the concentration of hydrogen in the helium-rich gas is 1000-1200 ppmv; the concentration of hydrogen in the dehydrogenated helium is less than 1 ppmv.

[0019] Furthermore, in step (1), the space velocity of the helium-rich gas entering the dehydrogenation zone is 200-300 h⁻¹. -1 By setting an appropriate space velocity, the reaction can be ensured to proceed fully, thus guaranteeing a high conversion rate of hydrogen.

[0020] Furthermore, in step (1), the preheating temperature is 150–200°C. By setting a suitable preheating temperature, it is possible to ensure that the reaction is triggered as soon as the reactant gas comes into contact with the bed, thereby improving the reaction efficiency.

[0021] Furthermore, the dehydrogenation zone occupies 65-75% of the rotor area; the oxygen replenishment zone occupies 15-20% of the rotor area; and the displacement zone occupies 10-15% of the rotor area. Reasonably allocating the area proportions of each zone helps to improve the dehydrogenation efficiency.

[0022] Furthermore, the rotating wheel of the rotary adsorber rotates at a speed of 2-4 revolutions per hour.

[0023] Furthermore, in step (2), the oxygen-containing helium gas is introduced into the oxygen replenishment zone at a rate of 50-150 m / s. 3 / h. By limiting the rate at which oxygen-containing helium gas is introduced into the oxygen replenishment zone within a reasonable range, the surface of the dehydrogenated material after the reaction can be more effectively replenished with oxygen.

[0024] Furthermore, in step (2), the oxygen concentration in the helium containing oxygen is 1000-1200 ppmv. By limiting the oxygen concentration in the helium containing oxygen to a reasonable range, the surface of the dehydrogenated material after the reaction can be more effectively replenished with oxygen.

[0025] Furthermore, in step (3), the dehydrogenated helium gas is introduced into the displacement zone at a rate of 20-40 m / s. 3 / h. By limiting the rate at which helium gas is introduced into the replacement zone after dehydrogenation to a reasonable range, the air on the surface of the dehydrogenated material can be replaced more effectively, thus completing the regeneration.

[0026] This invention provides a hydrogen-helium separation and purification process employing a chemical cycle. A dehydrogenation material with a large amount of surface-active oxygen is packed into the reaction bed. Helium containing hydrogen, after preheating, enters the bed and reacts with the dehydrogenation material. The hydrogen is consumed by the abundant surface-active oxygen in the dehydrogenation material, and the resulting tail gas is dehydrated and collected as purified helium. The bed regeneration process involves directly introducing air to oxidize the material, enriching the surface-active oxygen and restoring it to its pre-reduction state, thus forming a closed-loop chemical cycle.

[0027] The present invention discloses a hydrogen-helium separation and purification process. First, the oxidation-reduction reaction is carried out stepwise on a solid reaction bed composed of dehydrogenation material with a high specific heat capacity (>700 J / Kg·K), which makes it less likely to overheat or experience a sudden temperature rise. Second, the reduction and oxidation processes are independent of each other, and there is no exchange between the gases. Therefore, no oxygen enters during the dehydrogenation process, eliminating the need for subsequent oxygen removal treatment, simplifying the process flow and reducing operating costs. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in this invention 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 invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the structure of a rotary adsorber used in a hydrogen-helium separation and purification process provided in an embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] Example 1

[0032] This embodiment provides a hydrogen-helium separation and purification process, such as... Figure 1 As shown, a rotary adsorber is used for separation and purification. The rotor of the rotary adsorber is divided into a dehydrogenation zone, an oxygen replenishment zone, and a displacement zone. The areas of the dehydrogenation zone, the oxygen replenishment zone, and the displacement zone are 70%, 20%, and 10%, respectively. The three zones are isolated from each other by the conventional sealing structure of the rotor, and there is no exchange between the gases.

[0033] The rotor section of the rotary adsorber is filled with dehydrogenation material. The dehydrogenation material includes a support and a bimetallic carbide supported on the support. The bimetallic carbide accounts for 8% of the total mass of the dehydrogenation material. The support is biochar treated by air oxidation at 150°C for 24 hours to obtain oxidized biochar with a specific surface area of ​​1500 m². 2 / g, the H2 reduction consumption of this biochar below 100℃ is 300umol / g, and the bulk density of the biochar is 0.3kg / L. 2m 3 Biochar is made into granular packing material, which can be spherical, cylindrical, or other shapes, with a diameter of 0.5–3 cm. The bimetallic carbide is NiMoC. The bimetallic carbide is loaded onto a support via gas-phase carbothermal reduction to form a dehydrogenation material, which is then loaded into the rotor of the rotary adsorber.

[0034] The hydrogen-helium separation and purification process includes the following steps: Step (1): Preheat a helium-rich gas containing 1000 ppmv hydrogen to 150°C, then spray it at 500 m 3 The gas enters the dehydrogenation zone at a velocity of 250 h⁻¹, allowing hydrogen and oxygen in the helium-rich gas to react on the reaction bed. The resulting tail gas is dehydrated and collected as dehydrogenated helium. Oxygen on the dehydrogenation material in the dehydrogenation zone is consumed, resulting in a total reaction space velocity of 250 h⁻¹. -1 .

[0035] Step (2): The rotor rotates at 3 revolutions per hour, transferring the reaction bed from the dehydrogenation zone to the oxygen replenishment zone. The oxygen replenishment zone has circulating helium containing oxygen, with a concentration maintained at 1000 ppmv. The residual heat of the dehydrogenation material is used to replenish the surface oxygen. The circulating gas velocity is 100 m / s. 3 / h.

[0036] Step (3): The reaction bed is further transferred to the displacement zone, where the air on the material surface is displaced using dehydrogenated helium gas, completing the regeneration. The introduction rate of the dehydrogenated helium gas is 30 m / s. 3 / h. The gas exiting the displacement zone enters a processing unit containing dehydrogenation material to obtain purified helium with an oxygen concentration of less than 1 ppmv. This purified helium is then combined with the dehydrogenated helium obtained in step (1) to obtain the outlet purified helium.

[0037] Example 2

[0038] This embodiment provides a hydrogen-helium separation and purification process, such as... Figure 1As shown, a rotary adsorber is used for separation and purification. The rotor of the rotary adsorber is divided into a dehydrogenation zone, an oxygen replenishment zone, and a displacement zone. The areas of the dehydrogenation zone, the oxygen replenishment zone, and the displacement zone are 75%, 15%, and 10%, respectively. The three zones are isolated from each other by the conventional sealing structure of the rotor, and there is no exchange between the gases.

[0039] The rotor section of the rotary adsorber is filled with dehydrogenation material. The dehydrogenation material includes a support and a bimetallic carbide supported on the support. The bimetallic carbide accounts for 9% of the total mass of the dehydrogenation material. The support is prepared by a mild oxidation method to obtain oxidized modified multi-walled carbon nanotubes. The preparation method is as follows: nitric acid oxidation is performed using a 5% nitric acid solution at a temperature of 80°C for 2 hours to obtain surface-oxidized multi-walled carbon nanotubes. XPS analysis of the treated sample showed that the atomic content containing oxidized functional groups increased from the initial 2.15% to 18.25%, of which the content of oxidized carbon atoms was 15.73%. The specific surface area of ​​the modified multi-walled carbon nanotubes is 1300 m². 2 / g, the H2 reduction consumption of this modified multi-walled carbon nanotube below 100℃ is 500umol / g, and the bulk density is 0.3kg / L. 2m 3 Modified multi-walled carbon nanotubes are used to prepare granular fillers, which can be spherical, cylindrical, or other shapes with a diameter of 0.5–3 cm. The bimetallic carbide is NiMoC. The bimetallic carbide is loaded onto a support via a gas-phase carbothermal reduction method to form a dehydrogenation material. This dehydrogenation material is then loaded into the rotor of a rotary adsorber.

[0040] The hydrogen-helium separation and purification process includes the following steps: Step (1): After preheating the helium-rich gas containing 1200 ppmv hydrogen to 150°C, it is then subjected to a flow rate of 400 m 3 The gas enters the dehydrogenation zone at a velocity of 200 h⁻¹, causing hydrogen and oxygen in the helium-rich gas to react with each other on the reaction bed. The resulting tail gas is dehydrated and collected as dehydrogenated helium. Oxygen on the dehydrogenation material in the dehydrogenation zone is consumed, resulting in a total reaction space velocity of 200 h⁻¹. -1 .

[0041] Step (2): The rotor rotates at 3 revolutions per hour, transferring the reaction bed from the dehydrogenation zone to the oxygen replenishment zone. The oxygen replenishment zone has circulating helium containing oxygen, with a concentration maintained at 1200 ppmv. The residual heat of the dehydrogenation material is used to replenish the surface oxygen. The circulating gas velocity is 100 m / s. 3 / h.

[0042] Step (3): The reaction bed is further transferred to the displacement zone, where the air on the material surface is displaced using dehydrogenated helium gas, completing the regeneration. The introduction rate of the dehydrogenated helium gas is 30 m / s. 3 / h. The gas exiting the displacement zone enters a processing unit containing dehydrogenation material to obtain purified helium with an oxygen concentration of less than 1 ppmv. This purified helium is then combined with the dehydrogenated helium obtained in step (1) to obtain the outlet purified helium.

[0043] Example 3

[0044] This embodiment provides a hydrogen-helium separation and purification process, such as... Figure 1 As shown, a rotary adsorber is used for separation and purification. The rotor of the rotary adsorber is divided into a dehydrogenation zone, an oxygen replenishment zone, and a displacement zone. The areas of the dehydrogenation zone, the oxygen replenishment zone, and the displacement zone are 65%, 20%, and 15%, respectively. The three zones are isolated from each other by the conventional sealing structure of the rotor, and there is no exchange between the gases.

[0045] The rotor section of the rotary adsorber is filled with dehydrogenation material. The dehydrogenation material includes a support and a bimetallic carbide supported on the support. The bimetallic carbide accounts for 7% of the total mass of the dehydrogenation material. The support is prepared by a solution treatment method to obtain oxidized modified carbon black. The modified carbon black is prepared by chemical oxidation treatment, in which the carbon black is immersed in a potassium permanganate solution at 90°C for 2 hours to obtain surface-oxidized carbon black. The surface of the treated sample contains oxidized functional groups such as carbonate, carbonyl, and ketone groups. XPS analysis shows that the atomic content containing oxidized functional groups is approximately 11%. The specific surface area of ​​the modified carbon black is 900 m². 2 The modified carbon black has an H2 reduction consumption of 600 μmol / g below 100℃ and a bulk density of 0.3 kg / L. (The last sentence appears to be incomplete and possibly refers to a separate, unrelated statement.) 3 Modified multi-walled carbon nanotubes are used to prepare granular fillers, which can be spherical, cylindrical, or other shapes with a diameter of 0.5–3 cm. The bimetallic carbide is NiMoC. The bimetallic carbide is loaded onto a support via a gas-phase carbothermal reduction method to form a dehydrogenation material. This dehydrogenation material is then loaded into the rotor of a rotary adsorber.

[0046] The hydrogen-helium separation and purification process includes the following steps: Step (1): After preheating the helium-rich gas containing 1200 ppmv hydrogen to 150°C, it is then subjected to a flow rate of 450 m 3 The gas enters the dehydrogenation zone at a velocity of 225 h⁻¹, allowing hydrogen and oxygen in the helium-rich gas to react on the reaction bed. The resulting tail gas is dehydrated and collected as dehydrogenated helium. Oxygen on the dehydrogenation material in the dehydrogenation zone is consumed, resulting in a total reaction space velocity of 225 h⁻¹. -1 .

[0047] Step (2): The rotor rotates at 3 revolutions per hour, transferring the reaction bed from the dehydrogenation zone to the oxygen replenishment zone. The oxygen replenishment zone has circulating helium containing oxygen, with a concentration maintained at 1200 ppmv. The residual heat of the dehydrogenation material is used to replenish the surface oxygen. The circulating gas velocity is 100 m / s. 3 / h.

[0048] Step (3): The reaction bed is further transferred to the displacement zone, where the air on the material surface is displaced using dehydrogenated helium gas, completing the regeneration. The introduction rate of the dehydrogenated helium gas is 30 m / s. 3 / h. The gas exiting the displacement zone enters a processing unit containing dehydrogenation material to obtain purified helium with an oxygen concentration of less than 1 ppmv. This purified helium is then combined with the dehydrogenated helium obtained in step (1) to obtain the outlet purified helium.

[0049] Comparative Example 1

[0050] This comparative example provides a hydrogen-helium separation and purification process, which differs from Example 1 in that: the biochar is replaced with ordinary activated carbon, and the hydrogen concentration in the purified helium at the outlet is greater than 200 ppmv.

[0051] Comparative Example 2

[0052] This comparative example provides a hydrogen-helium separation and purification process, which differs from Example 1 in that the helium-rich gas velocity in step (1) reaches 2000 m / s. 3 / h, the hydrogen concentration in the purified helium at the outlet is greater than 50ppmv.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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; and these 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 the present invention.

Claims

1. A hydrogen-helium separation and purification process, characterized in that, A rotary adsorber is used for separation and purification. The rotor of the rotary adsorber is divided into a dehydrogenation zone, an oxygen replenishment zone, and a displacement zone. The rotor of the rotary adsorber is filled with dehydrogenation material. The hydrogen-helium separation and purification process includes the following steps: Step (1): After preheating, the hydrogen-rich helium gas is introduced into the dehydrogenation zone, so that the hydrogen and oxygen in the helium-rich gas react on the reaction bed. The tail gas produced is dehydrated and collected as dehydrogenated helium. Step (2): Transfer the reaction bed in the dehydrogenation zone to the oxygen replenishment zone, and use helium containing oxygen to replenish the surface oxygen using the residual heat of the dehydrogenation material; Step (3): The reaction bed is further transferred to the replacement zone, and the air on the surface of the material is replaced by dehydrogenated helium to complete the regeneration.

2. The hydrogen-helium separation and purification process according to claim 1, characterized in that, The dehydrogenation material includes a support and a bimetallic carbide supported on the support.

3. The hydrogen-helium separation and purification process according to claim 2, characterized in that, The carrier is a carbon-based material that has undergone oxidation treatment; preferably, the specific surface area of ​​the carrier is 800–2000 m². 2 / g; preferably, the bulk density of the carrier is 0.2-0.4 kg / L.

4. The hydrogen-helium separation and purification process according to claim 2, characterized in that, The bimetallic carbide includes one or more of NiMoC, CoMoC, NiWC, and CoWC; the bimetallic carbide accounts for 5-15 wt% of the total mass of the dehydrogenation material.

5. The hydrogen-helium separation and purification process according to claim 1, characterized in that, In step (1), the hydrogen concentration in the helium-rich gas is 1000-1200 ppmv; the hydrogen concentration in the dehydrogenated helium is less than 1 ppmv.

6. The hydrogen-helium separation and purification process according to claim 1, characterized in that, In step (1), the flow rate of the helium-rich gas entering the dehydrogenation zone is 400-500 m / s. 3 / h.

7. The hydrogen-helium separation and purification process according to claim 1, characterized in that, In step (1), the preheating temperature is 150-200℃.

8. The hydrogen-helium separation and purification process according to claim 1, characterized in that, The dehydrogenation zone occupies 65-75% of the rotor area; the oxygen replenishment zone occupies 15-20% of the rotor area; and the displacement zone occupies 10-15% of the rotor area.

9. The hydrogen-helium separation and purification process according to claim 1, characterized in that, The rotor of the rotary adsorber rotates at a speed of 2-4 revolutions per hour.

10. The hydrogen-helium separation and purification process according to claim 1, characterized in that, In step (2), the oxygen-containing The rate at which helium gas is introduced into the oxygen replenishment zone is 50-150 m / s. 3 / h; In step (2), the oxygen concentration in the helium containing oxygen is 1000-1200 ppmv; And / or, in step (3), the dehydrogenated helium gas is introduced into the displacement zone at a rate of 20-40 m / s. 3 / h.

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