A low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium

Abstract

The present application relates to the technical field of adsorption, and particularly relates to a low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium, comprising the following steps: S1. adsorbing raw gas containing helium and impurity gas in an adsorber; adsorbing the impurity gas on the adsorbent to obtain product helium with low impurity gas content from a non-adsorption phase; S2. sequentially performing regeneration one, regeneration two, regeneration three and regeneration four. Through the method of the present application, the product helium obtained from the non-adsorption phase has low impurity content, wherein the volume concentration of neon is less than 4 ppm, and the volume concentration of hydrogen is less than 1 ppm; and the method has low helium loss rate.

Description

Technical Field

[0001] This invention relates to the field of adsorption technology, specifically to a low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium. Background Technology

[0002] Helium is an indispensable rare strategic material for national defense, military industry, and high-tech industry development. It is widely used in aerospace, military manufacturing, cryogenics, medical applications, superconducting experiments, and optoelectronic product manufacturing, and is known as the "chip" of gases. Helium is mainly found in natural gas reservoirs. In recent years, domestic companies have increased their research and development efforts in helium extraction technology, but the helium concentration in my country's natural gas is extremely low, usually around 0.03%.

[0003] During the helium extraction process, technicians discovered that because the helium content in natural gas is low, trace amounts of neon are also concentrated during helium purification and concentration. This results in the purified helium products often containing several to tens of ppm of neon, which seriously affects the purity of the helium products and may also cause the helium products to fail to meet national standards for high-purity helium and ultra-pure helium.

[0004] Because helium and neon have very similar properties, existing gas separation technologies such as cryogenic distillation, membrane separation, and pressure swing adsorption (PSA) struggle to remove trace amounts of neon from helium. Only at low temperatures, utilizing the difference in adsorption capacity between helium and neon, is it possible to remove these traces. However, even at low temperatures, the difference in adsorption capacity between helium and neon is not significant. During regeneration, helium inevitably escapes along with neon, leading to a high helium loss rate and a substantial waste of helium resources.

[0005] In addition, hydrogen is often removed by catalytic oxidation during helium purification. In order to avoid the risk of overheating due to excessively high hydrogen concentration, and at the same time to achieve the hydrogen removal accuracy requirement of 1 ppm, the technology often adopts a method of two dehydrogenation and two drying. This makes the helium purification process complicated and the helium purification cost high.

[0006] Chinese patent CN 114562852 B discloses "a helium-neon removal system and method," the main idea of ​​which is to perform adsorption at low temperature, followed by regeneration after heating. The heat for regeneration comes from a heater, while the cooling energy during adsorption comes from the neon-containing crude helium gas. Due to the low heat capacity of the gas, this method inevitably requires a long time to achieve the cooling purpose during adsorption, during which time it is impossible to obtain product gas that meets the requirements for neon removal.

[0007] Chinese patent CN 116294435 A discloses "an apparatus and method for large-scale deep removal of neon and hydrogen from helium", but the method does not describe how to regenerate, nor does it describe the specific removal effects such as the neon removal rate and the helium loss rate.

[0008] Chinese patent CN 115404111 A discloses "a helium refining apparatus and method for removing neon", but it provides little description of the specific method for removing neon and does not describe the specific removal effects such as the neon removal rate and the helium loss rate. Summary of the Invention

[0009] The purpose of this invention is to provide a low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium, which can not only solve the problem of high helium impurity content in the product, but also solve the problem of high helium loss rate.

[0010] This invention discloses a low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium, comprising the following steps:

[0011] S1. The raw gas containing helium and impurity gases is adsorbed in an adsorber; the impurity gases are adsorbed onto the adsorbent, and a product gas helium with low impurity gas content is obtained from the non-adsorbed phase.

[0012] S2. Regeneration is performed in the following order:

[0013] Regeneration 1: After adsorption is completed, the residual gas in the adsorber is first released to the intermediate pressure. The released gas is then recycled to the preceding helium purification section for reuse.

[0014] Regeneration 2: The residual gas in the adsorber is released from intermediate pressure to atmospheric pressure. The released gas can be recycled to the preceding helium purification section or discharged outside the helium purification system.

[0015] Regeneration 3: Use a vacuum pump to evacuate the adsorber, and discharge the gas obtained from the evacuation to the outside of the helium purification system;

[0016] Regeneration 4: Use a vacuum pump to evacuate the adsorber. While evacuating, introduce a gas with low impurity content into the adsorber. The resulting gas is then recycled to the preceding helium purification section for reuse.

[0017] In the complete helium purification process, multiple separation and purification sections are used for multi-stage concentration and purification. The gas released during regeneration is recovered to the preceding helium purification section for recycling, which can effectively improve the total helium yield of the complete process.

[0018] Furthermore, the temperature of the adsorber is below -100℃, preferably below -180℃, and more preferably -220℃ to -180℃. At -220℃ to -180℃, liquid nitrogen can be used as a cold source, eliminating the need for heating during regeneration and resulting in low operating energy consumption. In this application, the temperature of the adsorber remains at a relatively stable low temperature, eliminating the need to deliberately introduce materials or energy to raise the temperature of the adsorber.

[0019] Furthermore, the adsorbent in the adsorbent is selected from one or more of activated carbon, molecular sieve or silica gel, and the number of adsorbents is one, two or more, and the adsorption pressure can also be determined according to the specific working conditions.

[0020] Furthermore, the temperature difference between the adsorber during regeneration and the adsorber during adsorption is less than 20°C.

[0021] Furthermore, the intermediate pressure is below 0.5 MPa.

[0022] Furthermore, in the second regeneration process, the residual gas in the adsorber is released from the intermediate pressure to below 50 kPa.

[0023] Furthermore, the impurity gas is neon and / or hydrogen.

[0024] Furthermore, the gas with low impurity content is the product gas or the gas released during regeneration.

[0025] Furthermore, the volume ratio of the gas with low impurity content to the product gas volume is less than 10%. The main purpose is not to raise the temperature of the adsorber, but to reduce the partial pressure of the impurity gas in the adsorber to an extremely low level, thereby achieving the goal of desorbing the impurity gas as thoroughly as possible.

[0026] Furthermore, the gas with low impurity gas content has a temperature below 0°C.

[0027] Furthermore, regeneration 3 is stopped when the minimum pressure inside the vacuum adsorber reaches -50kPa to -90kPa.

[0028] All pressure values ​​mentioned above are gauge pressures.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] 1. The method of the present invention yields a product with low helium impurity content from the non-adsorbed phase, wherein the volume concentration of neon is less than 4 ppm and the volume concentration of hydrogen is less than 1 ppm; and the method has a low helium loss rate.

[0031] 2. The method of the present invention divides the regeneration process into four different stages. During the regeneration process, the part with the highest impurity content is discharged outside the helium purification system, while the rest is recycled. It has the advantages of high precision in removing impurity gases and low helium loss rate.

[0032] 3. The product gas obtained from the non-adsorbed phase by the method of the present invention has high purity, and is high-purity helium with a purity higher than 99.999% or ultra-pure helium with an even higher purity; and the helium loss rate of the method is low, not exceeding 5%. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the process flow used in Embodiment 1 of the present invention.

[0035] Figure 2 This is a schematic diagram of the process flow used in Embodiment 2 of the present invention.

[0036] Figure 3 This is a schematic diagram of the process flow used in Embodiment 3 of the present invention.

[0037] Figure 4 This is a schematic diagram of the process flow used in Embodiment 4 of the present invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0039] Example 1

[0040] The low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium using the above-mentioned apparatus in this embodiment is shown in the process flow diagram below. Figure 1 The specific steps are as follows:

[0041] The feed gas is primarily helium, containing 50 ppm of neon, with a gauge pressure of 1.5 MPa and a temperature of room temperature. It is first cooled to approximately -180°C by a cooler, and then enters a cryogenic adsorption unit consisting of two adsorbers. The adsorbers are filled with activated carbon as the adsorbent. The adsorbers are continuously immersed in a liquid nitrogen container. During regeneration, it is not necessary to remove the liquid nitrogen container, remove the liquid nitrogen, or add external materials or energy to heat the adsorbers.

[0042] Taking adsorber A as an example, when adsorber A is performing adsorption, valves KV-1A and KV-3A are opened, and the cooled raw material gas enters the adsorber from the bottom of adsorber A. The temperature of the adsorber is about -190℃. The neon in the raw material gas is adsorbed on the adsorbent, and high-purity helium with a neon content of ≤4ppm is obtained from the top of the adsorber.

[0043] Regeneration is carried out in four stages:

[0044] Regeneration 1: Close valves KV-1A and KV-3A, open valves KV-2A, KV-10, HV-3 and KV-9, and release the residual gas in the adsorber to a gauge pressure of 0.4MPa. The released gas is recycled to the preceding helium purification section for reuse. After regeneration 1 is completed, close valves KV-2A, KV-10 and KV-9.

[0045] Regeneration 2: Open valves KV-4A and KV-6 to release the residual gas in the adsorber from gauge pressure 0.4MPa to atmospheric pressure. The released gas is discharged outside the helium purification system. After regeneration 2 is completed, close valves HV-3 and KV-6.

[0046] Regeneration 3: Open valves KV-5 and KV-7, use a vacuum pump to evacuate the adsorber, and discharge the gas obtained from evacuation to the outside of the helium purification system. When the pressure inside the adsorber reaches the gauge pressure of -70 kPa, regeneration 3 ends, and valve KV-7 is closed.

[0047] Regeneration 4: Open valves KV-2A and KV-8, and use a vacuum pump to evacuate the adsorber. While evacuating, open valves HV-2 and HV-4, and adjust the opening of valves HV-2 and HV-4 to introduce a small amount of product gas into the adsorber. The amount of product gas introduced accounts for 5% of the total product gas volume. The gas obtained in Regeneration 4 is recycled to the preceding helium purification section for reuse.

[0048] During the vacuum regeneration process, the lowest pressure inside the adsorber is approximately gauge pressure -80 kPa.

[0049] The final product, helium, contains 4 ppm of neon, with a helium loss rate of 3.8%.

[0050] Example 2:

[0051] This embodiment describes a low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium. The process flow diagram is shown below. Figure 2 The specific steps are as follows:

[0052] The feed gas is primarily helium, containing 8 ppm neon and 2 ppm hydrogen, with a gauge pressure of 2.0 MPa and a temperature of -190°C. The feed gas enters a cryogenic adsorption unit comprising four adsorbers. The adsorbent in the adsorbers is molecular sieve. The adsorbers are continuously immersed in liquid nitrogen containers. During regeneration, it is not necessary to remove the liquid nitrogen container, remove the liquid nitrogen, or add external materials or energy to heat the adsorbers.

[0053] Taking adsorber A as an example, when adsorber A is performing adsorption, valves KV-1A and KV-3A are opened, and the raw material gas enters the adsorber from the bottom of adsorber A. The temperature of the adsorber is about -210℃. The neon and hydrogen in the raw material gas are adsorbed on the adsorbent, and ultrapure helium with a neon content ≤1ppm and a hydrogen content ≤0.1ppm is obtained from the top of the adsorber.

[0054] Regeneration is carried out in four stages:

[0055] Regeneration 1: Close valves KV-1A and KV-3A, open valves KV-4A, HV-3 and KV-9, and release the residual gas in the adsorber to a gauge pressure of 0.2MPa. The released gas is recycled to the preceding helium purification section for reuse. After regeneration 1 is completed, close valve KV-9.

[0056] Regeneration 2: Open valve KV-6 to release the residual gas in the adsorber from gauge pressure 0.2MPa to atmospheric pressure. The released gas is discharged outside the helium purification system. After regeneration 2 is completed, close valves HV-3 and KV-6.

[0057] Regeneration 3: Open valves KV-5 and KV-7, use a vacuum pump to evacuate the adsorber, and discharge the gas obtained from evacuation to the outside of the helium purification system. When the pressure inside the adsorber reaches the gauge pressure of -80 kPa, regeneration 3 ends, and valve KV-7 is closed.

[0058] Regeneration 4: Open valves KV-2A and KV-8, and use a vacuum pump to evacuate the adsorber. While evacuating, open valve HV-2 and adjust the opening of valve HV-2 to introduce a small amount of product gas into the adsorber. The amount of product gas introduced accounts for 4% of the total product gas volume. The gas obtained in Regeneration 4 is recycled to the preceding helium purification section for reuse.

[0059] During the vacuum regeneration process, the lowest pressure inside the adsorber is approximately gauge pressure -80 kPa.

[0060] The final product, helium, contains 0.8 ppm of neon and 0.1 ppm of hydrogen, with a helium loss rate of 3.1%.

[0061] Example 3:

[0062] This embodiment describes a low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium. The process flow diagram is shown below. Figure 3 The specific steps are as follows:

[0063] The feed gas is primarily helium, containing 8 ppm neon and 2 ppm hydrogen, with a gauge pressure of 2.0 MPa and a temperature of -190°C. The feed gas enters a cryogenic adsorption unit consisting of two adsorbers. The adsorbers are filled with molecular sieves as adsorbent and are continuously immersed in a liquid nitrogen container. During regeneration, it is not necessary to remove the liquid nitrogen container or remove the liquid nitrogen, nor is it necessary to add external materials or energy to heat the adsorbers.

[0064] Taking adsorber A as an example, when adsorber A is performing adsorption, valves KV-1A and KV-3A are opened, and the raw material gas enters the adsorber from the bottom of adsorber A. The temperature of the adsorber is about -210℃. The neon and hydrogen in the raw material gas are adsorbed on the adsorbent, and ultrapure helium with a neon content ≤1ppm and a hydrogen content ≤0.1ppm is obtained from the top of the adsorber.

[0065] Regeneration is carried out in two stages:

[0066] Regeneration 1: Close valves KV-1A and KV-3A, open valves KV-4A, HV-3 and KV-6 to release the residual gas in the adsorber to atmospheric pressure. The released gas is discharged outside the helium purification system. After regeneration 1 is completed, close valves HV-3 and KV-6.

[0067] Regeneration 2: Open valves KV-2A and KV-5, and use a vacuum pump to evacuate the adsorber. While evacuating, open valve HV-2 and adjust the opening of valve HV-2 to introduce a small amount of product gas into the adsorber. The amount of product gas introduced accounts for 4% of the total product gas volume. The gas obtained from regeneration 2 is discharged outside the helium purification system.

[0068] During the vacuum regeneration process, the lowest pressure inside the adsorber is approximately gauge pressure -80 kPa.

[0069] The final product, helium, contains 0.8 ppm of neon and 0.1 ppm of hydrogen, with a helium loss rate of 10.4%.

[0070] Example 4:

[0071] This embodiment describes a low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium. The process flow diagram is shown below. Figure 4 The specific steps are as follows:

[0072] The feed gas is primarily helium, containing 8 ppm neon and 2 ppm hydrogen, with a gauge pressure of 2.0 MPa and a temperature of room temperature. It is first cooled to approximately -190°C by a cooler, and then enters a cryogenic adsorption unit consisting of two adsorbers. The adsorbent in the adsorbers is molecular sieve. The adsorbers are continuously immersed in a liquid nitrogen container. During regeneration, it is not necessary to remove the liquid nitrogen container, remove the liquid nitrogen, or add external materials or energy to heat the adsorbers.

[0073] Taking adsorber A as an example, when adsorber A is performing adsorption, valves KV-1A and KV-3A are opened, and the raw material gas enters the adsorber from the bottom of adsorber A. The temperature of the adsorber is about -210℃. The neon and hydrogen in the raw material gas are adsorbed on the adsorbent, and ultrapure helium with a neon content ≤1ppm and a hydrogen content ≤0.1ppm is obtained from the top of the adsorber.

[0074] Regeneration is carried out in three stages:

[0075] Regeneration 1: Close valves KV-1A and KV-3A, open valves KV-2A, KV-10, HV-3 and KV-6 to release the residual gas in the adsorber to a gauge pressure of 0.2MPa. The released gas is recycled to the preceding helium purification section for reuse. After regeneration 1 is completed, close valves KV-2A and KV-10.

[0076] Regeneration 2: Open valve KV-4A to release the residual gas in the adsorber from gauge pressure 0.2MPa to atmospheric pressure. The released gas is recycled to the preceding helium purification section for reuse. After regeneration 2 is completed, close valves HV-3 and KV-6.

[0077] Regeneration 3: Open valves KV-5 and KV-2A, and use a vacuum pump to evacuate the adsorber. While evacuating, open valve HV-2 and adjust the opening of valve HV-2 to introduce a small amount of product gas into the adsorber. The amount of product gas introduced accounts for 4% of the total product gas volume. The gas obtained in regeneration 3 is discharged outside the helium purification system.

[0078] During the vacuum regeneration process, the lowest pressure inside the adsorber is approximately gauge pressure -80 kPa.

[0079] The final product, helium, contains 0.8 ppm of neon and 0.1 ppm of hydrogen, with a helium loss rate of 7.2%.

[0080] The above are the embodiments listed in this example. However, this example is not limited to the optional embodiments described above. Those skilled in the art can arbitrarily combine the above methods to obtain other various embodiments. Anyone can derive other various forms of embodiments based on the inspiration of this example. The above specific embodiments should not be construed as limiting the scope of protection of this example. The scope of protection of this example should be determined by the claims, and the specification can be used to interpret the claims.

Claims

1. A low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium, characterized in that: Includes the following steps: S1. The raw material gas containing helium and impurity gases is adsorbed in the adsorber; S2. Regeneration is performed in the following order: Regeneration 1: After adsorption is completed, the residual gas in the adsorber is first released to the intermediate pressure. The released gas is then recycled to the preceding helium purification section for reuse. Regeneration 2: The residual gas in the adsorber is released from intermediate pressure to atmospheric pressure. The released gas is either recycled to the preceding helium purification section or discharged outside the helium purification system. Regeneration 3: Use a vacuum pump to evacuate the adsorber, and discharge the gas obtained from the evacuation to the outside of the helium purification system; Regeneration 4: Use a vacuum pump to evacuate the adsorber. While evacuating, introduce a gas with low impurity content into the adsorber. The resulting gas is recycled to the preceding helium purification section for reuse. The temperature of the adsorber is below -100℃; The impurity gas is neon and / or hydrogen; The intermediate pressure is less than 0.5 MPa; The gas with low impurity content is the product gas or the gas released during regeneration.

2. The low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium according to claim 1, characterized in that: The temperature of the adsorber is below -180°C.

3. The low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium according to claim 2, characterized in that: The temperature of the adsorber is -220℃ to -180℃.

4. The low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium according to claim 1, characterized in that: The temperature difference between the adsorber during regeneration and the adsorber during adsorption is less than 20℃.

5. The low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium according to claim 1, characterized in that: The adsorbent in the adsorber is selected from one or more of activated carbon, molecular sieves, or silica gel.

6. The low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium according to claim 1, characterized in that: The gas with low impurity content has a temperature below 0°C.

7. The low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium according to claim 1, characterized in that: The volume ratio of the gas with low impurity content to the product gas volume is less than 10%.

8. The low-temperature pressure swing adsorption method for efficiently removing neon and hydrogen from helium according to claim 1, characterized in that: The evacuation process described in Regeneration 3 is stopped when the minimum pressure inside the adsorber reaches -50kPa to -90kPa.

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