Process system for separating and purifying helium from helium-containing natural gas

Abstract

The invention discloses a process system for separating and purifying helium from helium-containing natural gas, which comprises a pretreatment system, a membrane separation system, a VPSA decarburization system, a TSA refined removal system, a first pressurization system, a primary membrane separation system, a second pressurization system, a secondary membrane separation system, a third pressurization system, a PSA purification system and an alloy dehydrogenation system which are sequentially connected step by step through pipelines, the fourth pressurization system is arranged between the PSA purification system and the TSA refined removal system; the impermeable gas discharged by the membrane separation system is fed into a natural gas pipeline network; low-pressure desorbed gas discharged by the VPSA decarburization system and desorbed gas discharged by the TSA fine desorption system are used for being fed into a fuel pipe network; and impermeable gas discharged by the first-stage membrane separation system and desorbed gas discharged by the PSA purification system are used for refluxing to the TSA fine removal system. According to the process system, helium can be directly separated and purified from the helium-containing natural gas which is exploited from a gas field and pretreated, the helium recovery rate is high, the process flow is simple, and the energy consumption is low.

Description

Technical Field

[0001] The invention relates to the technical field of helium extraction, and in particular to a process system for separating and purifying helium from helium-containing natural gas. Background Art

[0002] As a non-renewable rare gas, helium plays a vital role in scientific research, semiconductors, medical treatment, petrochemicals, aerospace, and navigation, and its demand is increasing year by year. Helium mainly comes from air, some natural gas, and associated gas. Among them, helium-rich natural gas (natural gas with a helium content greater than 0.1%) is currently the most stable and reliable source of helium. However, the helium content in most natural gases is less than 0.05%, resulting in helium mainly relying on imports.

[0003] In order to improve the extraction efficiency of helium and reduce energy consumption, researchers have explored a variety of technical paths for helium extraction from natural gas. A technology for extracting helium from the natural gas liquefaction process is a commonly used method, such as a method for extracting high-purity helium from low-helium BOG (BOG is the abbreviation of Big Off Gas, which refers to a large amount of mixed gas produced after the production of LNG) described in the patent with publication number CN210237128U. This method is mainly used for tail gas purification in the natural gas liquefaction process. Another is a system for co-producing helium using an LNG production device described in the patent with publication number CN212538459U. The system uses flash steam generated during the production and storage of liquefied natural gas for dehydrogenation and helium purification. However, these methods are limited to the recovery and extraction of helium in the natural gas liquefaction process, and such methods have not been widely used in other scenarios such as natural gas chemical industry, power generation, CNG or natural gas for vehicles in the prior art.

[0004] Although the existing membrane separation technology, VPSA (pressure swing adsorption) decarbonization technology, TSA (temperature swing adsorption) fine decarbonization technology and alloy dehydrogenation technology can be used for natural gas helium extraction, they are mostly used in the liquefied natural gas process. The direct implementation of helium extraction technology in natural gas chemical industry, power generation and other scenarios faces a series of challenges such as large investment, complex operation and high energy consumption. The main problem is that the efficient removal of various impurities and the efficient recovery of helium in the natural gas processing process are not fully considered. In particular, the TSA fine decarbonization process has poor adaptability to the impurity content in the raw gas, which may lead to high operating costs, and other impurities (such as CO2, Ar and rare gases) will be introduced during the catalytic dehydrogenation process, causing additional troubles. In addition, although the cryogenic method can achieve helium extraction, the equipment is complex, the investment is large, the energy consumption is high, and the liquefied natural gas produced during the processing process needs to be gasified and used, which adds additional operating steps. Summary of the invention

[0005] The invention provides a process system for separating and purifying helium from helium-containing natural gas, which can separate and purify helium from the helium-containing natural gas that has been directly mined from a gas field and pretreated.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A process system for separating and purifying helium from helium-containing natural gas, comprising a pretreatment system A, a membrane separation system B, a VPSA decarburization system C, a TSA fine decarburization system E, a first pressurizing system F1, a primary membrane separation system G1, a second pressurizing system F2, a secondary membrane separation system G2, a third pressurizing system F3, a PSA purification system H and an alloy dehydrogenation system I, and a fourth pressurizing system F4 arranged between the PSA purification system H and the TSA fine decarburization system E; the permeate gas discharged from the membrane separation system B is used to enter the VPSA decarburization system C, and the non-permeate gas is used to be sent to the natural gas pipeline network; the VPSA decarburization system C The discharged low-pressure desorbed gas is used to be fed into the fuel pipeline network; the TSA desorbed gas discharged from the TSA fine desorption system E is used to be fed into the fuel pipeline network; the primary permeate gas discharged from the primary membrane separation system G1 is used to enter the second pressurizing system F2, and the primary non-permeate gas is used to flow back to the TSA fine desorption system E; the secondary permeate gas discharged from the secondary membrane separation system G2 is used to enter the third pressurizing system F3, and the secondary non-permeate gas is used to flow back to the primary membrane separation system G1; the crude helium purified by the PSA purification system H is used to enter the alloy dehydrogenation system I, and the PSA desorbed gas is pressurized by the fourth pressurizing system F4 and then flows back to the TSA fine desorption system E.

[0008] Preferably, a deoxygenation system D is further included. When the helium-containing natural gas entering the pretreatment system A does not contain oxygen, the purified natural gas discharged from the VPSA decarbonization system C directly enters the TSA fine decarbonization system E; when the helium-containing natural gas entering the pretreatment system A contains oxygen, the purified natural gas discharged from the VPSA decarbonization system C is passed into the deoxygenation system D, and the purified natural gas is deeply treated to remove oxygen through the deoxygenation system D before entering the TSA fine decarbonization system E; when the helium-containing natural gas entering the pretreatment system A contains oxygen but does not contain hydrogen, or the amount of hydrogen produced by the reaction of oxygen and hydrogen is insufficient, hydrogen is supplemented from the outside to the deoxygenation system D through a pipeline, and at the same time, the hydrogen discharged from the alloy dehydrogenation system I is supplemented to the deoxygenation system D through a pipeline.

[0009] Preferably, the pressure of the permeate gas discharged from the membrane separation system B is controlled at 0.05-0.4 MPa.

[0010] Preferably, the membrane separator materials of the membrane separation system B, the primary membrane separation system G1 and the secondary membrane separation system G2 are all made of organic fiber membranes.

[0011] Preferably, the TSA fine removal system E removes H2O to ≤3 ppm, CO2 to ≤3 ppm, and H2S to ≤3 ppm in natural gas by temperature swing adsorption.

[0012] Preferably, the compressors used in the first pressurizing system F1, the second pressurizing system F2, the third pressurizing system F3 and the fourth pressurizing system F4 are reciprocating compressors or diaphragm compressors; the first pressurizing system F1 is used to pressurize the natural gas purified by the TSA degassing system E to 1.0-2.2 MPa; the second pressurizing system F2 is used to pressurize the primary permeate gas of 20-100 kPa to 1.2-2.4 MPa; the third pressurizing system F3 is used to pressurize the secondary permeate gas of 0.2-0.4 MPa to 1.6-1.8 MPa; the fourth pressurizing system F4 is used to pressurize the PSA desorption gas to 0.4-0.5 MPa.

[0013] Preferably, the PSA purification system H removes N2 to 1.5 ppm and CH4 to 0.4 ppm in the secondary permeate gas by pressure swing adsorption.

[0014] Preferably, the VPSA decarbonization system C adopts vacuum pressure swing adsorption, and its process flow adopts 4 to 12 adsorption towers and the number of pressure equalization is 1 to 7 times.

[0015] Preferably, the adsorption towers of the PSA purification system H adopt 4 to 6 adsorption towers, the pressure equalization times are 1 to 3 times, and the adsorbent is regenerated by flushing or vacuuming; the PSA purification system H comprises a precooling heat exchanger, a downstream gas buffer tank V and several PSA adsorption towers filled with different adsorbents; the process steps of the PSA purification system H comprise: the secondary permeate gas pressurized by the third pressurization system F3 enters the precooling heat exchanger for precooling, and the temperature of the secondary permeate gas is reduced to -10 to -40°C, and then enters each PSA adsorption tower in turn, and each PSA adsorption tower adsorbs the impurity gas. The present invention also provides an impurity gas; for a certain PSA adsorption tower, its working process comprises: after the adsorption process is completed, according to the adsorption direction, H2 and He with higher internal pressure are recovered to the PSA adsorption tower with lower pressure that has been regenerated for pressure equalization and pressure reduction operation; the pressure equalization and pressure reduction operation is ended After that, first, according to the adsorption direction, the helium-hydrogen mixed gas at the top of the PSA adsorption tower is quickly put into the downstream gas buffer tank V, and these gases will be used as the regeneration gas source for the adsorbent; after the downstream process is completed, the pressure in the PSA adsorption tower is reduced to 0.03MPa in the opposite direction of the adsorption, at this time, the impurities in the adsorbent begin to be desorbed, and the reverse desorbed gas will be sent to the fourth pressurization system F4 to recover helium; then, the helium in the downstream gas buffer tank V is used to flush the PSA adsorption tower in the opposite direction of the adsorption to ensure that the impurities in the adsorbent are completely desorbed, and the flushing desorbed gas will also enter the fourth pressurization system F4 to recover helium; after the flushing regeneration process is completed, the adsorption tower is pressure-equalized and boosted in turn using H2 and He with higher pressures from other adsorption towers; after the pressure-equalizing and boosting process is completed, the pressure of the adsorption tower is slowly and steadily increased to the adsorption pressure using the product helium-hydrogen mixed gas through the boost regulating valve.

[0016] Preferably, the alloy hydrogen absorption material of the alloy hydrogen absorption system I is mainly composed of titanium, manganese, zirconium, nickel, lanthanum, vanadium and various rare earths / rare metals; the alloy dehydrogenation system I is composed of a primary alloy dehydrogenation system and a secondary alloy dehydrogenation system, the primary alloy dehydrogenation system includes a filter and an alloy adsorption column, and the secondary alloy dehydrogenation system includes an alloy adsorption column; the dehydrogenation process steps of the alloy dehydrogenation system I include: the mixed gas passes through the filter of the PSA purification system H to filter out the adsorbent dust, and then flows through the alloy adsorption columns of the primary and secondary alloy dehydrogenation systems in sequence; in a low temperature environment of -10 to -40°C, the alloy adsorption column adsorbs H2 but not He, thereby achieving H2 and H e is effectively separated to produce a high-purity helium product; after the alloy adsorption column adsorbs hydrogen, it needs to be heated and regenerated; heating regeneration is to heat the alloy adsorption column by heat-conducting oil or electric heating, and high temperature is used to promote hydrogen desorption to obtain a high-purity helium product; then the hydrogen is extracted by a vacuum pump for export or recovered to the deoxidation system D for deoxidation; after the heating regeneration is completed, cooling regeneration is performed, and cold oil or compressed air with a temperature of 0 to 10°C in the circulating refrigerator is introduced into the interlayer of the alloy adsorption column through valve switching to achieve rapid cooling of the alloy adsorption column; after the alloy adsorption column is cooled to a low-pressure state, the raw material low-temperature hydrogen and helium mixed gas is used to slowly increase the pressure of the alloy adsorption column to the hydrogen absorption pressure.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention can directly separate and purify helium from helium-containing natural gas mined from a gas field and pretreated. By setting up a multi-stage coupling process such as a pretreatment system, a membrane separation system, a VPSA decarburization system, a TSA fine decarburization system, a PSA purification system and an alloy dehydrogenation system, the helium in the helium-containing natural gas can be purified to 99% to 99.999%. The purified helium has a high purity and can be widely used in various needs.

[0019] (2) The helium recovery rate of the present invention is as high as over 86%, which has higher efficiency and lower energy consumption compared with traditional methods; the process flow is simple, the operation is safe and stable, and the risks brought by complex operations are avoided.

[0020] (3) The present invention adopts advanced membrane separation technology, pressure swing adsorption technology and alloy dehydrogenation technology, which greatly reduces equipment investment and floor space. The miniaturized design makes it easier to use and maintain. At the same time, the use of special alloy materials to achieve efficient separation of H2 and He not only greatly reduces hydrogen consumption, but also improves helium recovery rate. Different from the traditional catalytic combustion method, it avoids the risk of introducing impurities and generating a large amount of solid waste, and is more environmentally friendly and economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1This is a process flow chart of a process system for separating and purifying helium from helium-containing natural gas in an embodiment of the present invention;

[0022] Figure 2 is a process flow chart of a PSA purification system H in an embodiment of the present invention;

[0023] Figure 3 1 is a process flow chart of the alloy dehydrogenation system I in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0025] Example 1

[0026] like Figure 1-3 As shown, this embodiment provides a process system for separating and purifying helium from helium-containing natural gas, which is designed for processing oxygen-free helium-containing natural gas. The system includes a pretreatment system A, a membrane separation system B, a VPSA decarburization system C, a TSA fine decarburization system E, a first pressurizing system F1, a primary membrane separation system G1, a second pressurizing system F2, a secondary membrane separation system G2, a third pressurizing system F3, a PSA purification system H and an alloy dehydrogenation system I, and a fourth pressurizing system F4 arranged between the PSA purification system H and the TSA fine decarburization system E.

[0027] See also Figure 2The PSA purification system H includes a precooling heat exchanger, a PSA adsorption tower A, a PSA adsorption tower B, a PSA adsorption tower C, a PSA adsorption tower D, a PSA adsorption tower E and a PSA adsorption tower F arranged in parallel, a gas discharge buffer tank V, pipelines CP1, CP2, CP3, EP1, EP2, EP3 and EP4, and a pressure regulating valve arranged on the pipeline; one end of the pipeline CP1 is connected to the third pressurizing system F3, and the other end is respectively connected to multiple inlet pipelines at the bottom of the PSA adsorption towers A to F; the precooling heat exchanger is arranged on the pipeline CP1; one end of the pipeline CP2 is respectively connected to the outlet pipelines of the PSA adsorption towers A to F, and the other end is connected to the alloy dehydrogenation system I; one end of the pipeline CP3 is ... The outlet pipes of the PSA adsorption towers A~F are respectively connected to multiple inlet pipes at the bottom of the PSA adsorption towers A~F, and the other end is connected to the fourth pressurization system F4; the outlet pipes of the PSA adsorption towers A~F are connected to the first equalizing pressure mechanism and the final rising pipe EP1; the outlet pipes of the PSA adsorption towers A~F are connected to the flushing inlet pipe EP2; the outlet pipes of the PSA adsorption towers A~F are connected to the second equalizing pressure mechanism and the forward release pipe EP3; the inlet of the forward release buffer tank V is connected to the second equalizing pressure mechanism and the forward release pipe EP3; the outlet of the forward release buffer tank V is connected to the flushing inlet pipe EP2; the inlet pipes of the PSA adsorption towers A~F are connected to the reverse release pipe EP4, and the other end of the pipe EP4 is connected to the pipe CP3.

[0028] See also Figure 3The alloy dehydrogenation system I includes a primary alloy dehydrogenation system and a secondary alloy dehydrogenation system. The primary alloy dehydrogenation system includes a filter and an alloy adsorption column, and the secondary alloy dehydrogenation system includes an alloy adsorption column. According to the hydrogen content in the product gas of the PSA purification system H, the process flow of the alloy dehydrogenation system I can adopt 1 to 3 levels of alloy columns. In the alloy dehydrogenation system I, the hydrogen and helium inlet pipeline DP1 is connected to the multiple inlet pipelines at the top of the primary alloy adsorption column; the multiple outlet pipelines at the bottom of the primary alloy adsorption column are connected to the inlet main pipe of the secondary alloy dehydrogenation; the inlet main pipe of the secondary alloy dehydrogenation is connected to the multiple inlet pipelines at the top of the secondary alloy adsorption column; the multiple outlet pipelines at the bottom of the secondary alloy adsorption column are connected to the product helium outlet main pipe DP2; the multiple outlet pipelines at the top of the primary alloy adsorption column are connected to the product hydrogen outlet main pipe DP4; the multiple outlet pipelines at the bottom of the primary alloy adsorption column are connected to the main pipe for secondary alloy recovery; The main pipe for secondary alloy recovery is connected to the helium recovery main pipe DP3; the multiple outlet pipes at the bottom of the secondary alloy adsorption column are connected to the helium recovery main pipe DP3; the multiple outlet pipes at the bottom of the primary alloy adsorption column are connected to the primary alloy dehydrogenation vacuum pump inlet main pipe; the primary alloy dehydrogenation vacuum pump outlet pipe is connected to the alloy dehydrogenation venting main pipe DP5; the multiple outlet pipes at the bottom of the secondary alloy adsorption column are connected to the secondary alloy dehydrogenation vacuum pump inlet main pipe; the secondary alloy dehydrogenation vacuum pump outlet pipe is connected to the alloy dehydrogenation venting main pipe DP5; the filter is arranged on the hydrogen and helium inlet pipe DP1.

[0029] The pretreatment system A performs desulfurization, decarbonization, dehydration, dehydrocarbonization and other pretreatments on the mined helium-containing raw natural gas to obtain purified natural gas. The pretreated natural gas is pressurized to 2-10 MPa and transported out through pipelines.

[0030] The membrane separation system B initially concentrates the volume fraction of helium in the purified natural gas to 1% to 4% (this data is mainly related to the pressure of the raw natural gas and the helium gas volume fraction), and the permeated gas is sent to the VPSA decarbonization system C through a pipeline. The non-permeated gas returns to the natural gas network through pipeline 2. The main purpose of this step is to use a special polymer material membrane separator, according to the difference in solubility and diffusion coefficient of different gases in the natural gas in the material, resulting in different relative permeabilities of different gases in the material. According to this characteristic, gases with relatively fast permeation rates such as H2, He, CO2, H2O, H2S, etc. are enriched on the permeation side of the material after passing through the material, while gases with relatively slow permeation rates such as methane (CH4), nitrogen (N2), carbon monoxide (CO) and argon (Ar) are enriched on the retention side of the material, thereby achieving the purpose of separating the mixed gas.

[0031] The pressure of the permeate gas discharged from the membrane separation system B is controlled at 0.05-0.4 MPa.

[0032] The VPSA decarbonization system C removes CO2, H2O, H2S and C 2+ Impurity removal. The main purpose of this step is to remove "fast gas" impurities in the membrane separation system while meeting the high recovery rate of helium, so as to avoid accumulation in the system during helium recycling, resulting in excessive impurities in the product helium. The low-pressure desorbed gas generated by the VPSA decarbonization system C is sent to the fuel pipeline network. The VPSA decarbonization system C adopts vacuum pressure swing adsorption, and its process flow adopts 4 to 12 adsorption towers, the number of pressure equalization is 1 to 7 times, and the adsorbent is regenerated by vacuum method.

[0033] The TSA fine removal system E removes H2O to 1ppm, CO2 to 1ppm, and H2S to 1ppm from natural gas through temperature swing adsorption. The TSA fine removal system E uses temperature swing adsorption (TSA) to deeply remove H2O, CO2, and H2S from natural gas. The regenerated gas uses the primary non-permeate gas of the primary membrane separation system G1. The process flow of the TSA fine removal system E uses 2 to 4 adsorption towers, and the regeneration temperature is 160 to 220°C.

[0034] The first pressurizing system F1 is used to pressurize the natural gas deeply purified by the TSA fine separation system E to 1.0-2.2 MPa. Similarly, the main purpose of this step is to increase the pressure of the purified natural gas, increase the osmotic pressure of the first-stage membrane separator, and improve the permeability of the membrane-separated fast gas.

[0035] The compressor used in the first pressurizing system F1 is a reciprocating compressor or a diaphragm compressor. The reciprocating compressor is preferably equipped with a packing leakage recovery system to reduce helium loss.

[0036] The primary membrane separation system G1 further concentrates helium in the pressurized purified natural gas through the primary membrane separation, and the primary permeate gas is sent to the second pressurization system F2 through the pipeline. The primary non-permeate gas is connected to the TSA fine removal system E through the pipeline 5. The main purpose of this step is to continue to concentrate helium in the natural gas using the primary membrane separator.

[0037] The second pressurizing system F2 is to pressurize the primary permeate gas of 20-100 kPa to 1.2-2.4 MPa. The main purpose of this step is to increase the pressure of the primary permeate gas, increase the osmotic pressure of the secondary membrane separator, and improve the permeability of the membrane separation fast gas. The compressor used in the second pressurizing system F2 is a reciprocating compressor or a diaphragm compressor. The reciprocating compressor is preferably equipped with a packing leakage recovery system to reduce helium loss.

[0038] The secondary membrane separation system G2 further concentrates the pressurized primary permeate gas through secondary membrane separation, and the secondary permeate gas is sent to the third pressurization system F3 through a pipeline. The secondary non-permeate gas is connected to the inlet pipeline of the primary membrane separation system G1 through a pipeline 6. The principle of this step is the same as that of the primary membrane separation system G1, and the main purpose is to use the secondary membrane separator to continue to concentrate the helium in the primary permeate gas. In order to improve the helium recovery rate, the secondary non-permeate gas is returned to the primary membrane separator for recovery. The primary permeate gas passes through the secondary membrane separator to concentrate the hydrogen and helium in the raw gas to more than 85%.

[0039] The membrane separator materials of the membrane separation system B, the primary membrane separation system G1 and the secondary membrane separation system G2 are all made of polyimide (PI) fiber membrane.

[0040] The third pressurizing system F3 pressurizes the secondary permeate gas of 0.2-0.4 MPa to 1.6-1.8 MPa. The main purpose of this step is to increase the adsorption pressure of the PSA purification system H, to ensure the adsorption effect of impurities other than hydrogen and helium and the recovery rate of helium. The compressor used in the third pressurizing system F3 is a diaphragm compressor.

[0041] The PSA purification system H can remove N2 to 1.5ppm and CH4 to 0.4ppm in the secondary permeate gas through pressure swing adsorption. The pressure swing adsorption desorbed gas has a high helium content and is recycled to the fourth pressurization system F4 to improve the helium recovery rate of the system. The pressure swing adsorption product hydrogen and helium are sent to the alloy dehydrogenation system I through a pipeline to remove hydrogen. The desorbed gas of the PSA purification system enters the fourth pressurization system F4 and is pressurized to 0.4-0.5MPa, and returns to the inlet of the TSA fine desorption system E through pipeline 7 for recovery.

[0042] Specifically, the process steps of the PSA purification system H include: the secondary permeate gas from the third pressurizing system F3 after pressurization enters the precooling heat exchanger for precooling, and the temperature of the secondary permeate gas is reduced to -10 to -40°C, and then enters each PSA adsorption tower in turn, and each PSA adsorption tower adsorbs one impurity gas; for a certain PSA adsorption tower, its working process includes: after the adsorption process is completed, according to the adsorption direction, the H2 and He with higher internal pressure are transferred to the PSA adsorption tower with lower pressure that has been regenerated for equalization and pressure reduction operation; after the equalization and pressure reduction operation is completed, firstly, according to the adsorption direction, the helium-hydrogen mixed gas at the top of the PSA adsorption tower is quickly recovered to the downstream gas buffer tank V, and these gases will be used as adsorbents regeneration gas source; after the forward discharge process is completed, the pressure in the PSA adsorption tower is reduced to 0.03MPa in the opposite direction of adsorption, at which time the impurities in the adsorbent begin to be desorbed, and the reversed desorbed gas will be sent to the fourth pressurization system F4 to recover helium; then, the helium in the forward discharge buffer tank V is used to flush the PSA adsorption tower in the opposite direction of adsorption to ensure that the impurities in the adsorbent are completely desorbed, and the flushing desorbed gas will also enter the fourth pressurization system F4 to recover helium; after the flushing regeneration process is completed, the adsorption tower is pressure-equalized and boosted in turn using H2 and He with higher pressures from other adsorption towers; after the pressure-equalizing and boosting process is completed, the pressure of the adsorption tower is slowly and steadily increased to the adsorption pressure using the product helium-hydrogen mixed gas through the boost regulating valve.

[0043] The alloy dehydrogenation system I is used to remove hydrogen from the product gas of the PSA purification system H to less than 1ppm. The principle is that once H2 contacts the hydrogen absorbing material, it can be decomposed into H atoms on its surface, and then the H atoms diffuse into the material until they react with the material to form hydrides. At this time, H2 is stored in the atomic state in the crystallization point of the hydrogen absorbing material (the gap between the tetrahedron and the octahedron).

[0044] Specifically, the dehydrogenation process steps of the alloy dehydrogenation system I include: the mixed gas passes through the PSA purification system H to filter out the adsorbent dust, and then flows through the alloy adsorption columns of the primary and secondary alloy dehydrogenation systems in sequence; in a low temperature environment of -10 to -40°C, the alloy adsorption column adsorbs H2 but does not adsorb He, thereby achieving effective separation of H2 and He and producing a high-purity helium product; after the alloy adsorption column adsorbs hydrogen, it needs to be heated and regenerated; the heating regeneration is to heat the alloy adsorption column by heat transfer oil or electric heating, and the high temperature promotes the desorption of hydrogen to obtain a high-purity helium product; then the hydrogen is extracted and exported by a vacuum pump; after the heating regeneration is completed, cooling regeneration is performed, and the cold oil or compressed air with a temperature of 0 to 10°C in the circulating refrigeration machine is introduced into the interlayer of the alloy adsorption column by valve switching, so as to achieve rapid cooling of the alloy adsorption column; after the alloy adsorption column is cooled to a low pressure state, the raw material low-temperature hydrogen and helium mixed gas is used to slowly increase the pressure of the alloy adsorption column to the hydrogen absorption pressure.

[0045] The alloy hydrogen absorption material of the alloy hydrogen absorption system I is mainly composed of titanium, manganese, zirconium, nickel, lanthanum, vanadium and various rare earths / rare metals; the H2 and He separation material is a material that can achieve reversible absorption and release of H2. When selectively absorbing H2, H2 reacts chemically with the material to generate hydride, thereby storing gaseous H2 in solid form. The saturated material bed is switched to the regeneration process, and the absorbed H2 can be released by heating the material to achieve regeneration of the H2 absorption material, thereby achieving separation of H2 and He.

[0046] The above process system is used to purify helium from the helium-containing natural gas produced from the gas field. The specific process flow is as follows:

[0047] First, the helium-containing natural gas produced from the gas field is pressurized to 63.5 bar and then enters the pretreatment system A through pipeline 1. After impurities such as sulfur and water in the helium-containing natural gas are removed in the pretreatment system A, purified gas is obtained. The purified gas enters the membrane separation system B through a pipeline for crude helium extraction. The non-permeate gas pressure discharged from the membrane separation system B is 63 bar, which is sent to the natural gas pipeline network through pipeline 2; while the permeate gas pressure discharged from the membrane separation system B is controlled at 4 bar and enters the VPSA decarbonization system C through a pipeline. In the VPSA decarbonization system C, CO2, H2S, H2O and heavy hydrocarbons in the permeate gas are removed by using an adsorbent with good adsorption selectivity for CO2, H2S, H2O and heavy hydrocarbons, while ensuring that the recovery rate of H2 and He reaches 99.5%. The low-pressure desorbed gas discharged from the VPSA decarbonization system C is sent to the fuel pipeline network through pipeline 9. The decarbonized purified gas treated by the VPSA decarbonization system C enters the TSA fine decarbonization system E through a pipeline. The TSA fine decarbonization system E deeply removes CO2, H2S, H2O and heavy hydrocarbons therein, and removes the content of CO2 and H2O to ≤1ppm. The desorbed gas of the TSA fine decarbonization system E is sent to the fuel pipeline network through pipeline 4.The purified gas treated by the TSA fine degassing system E is connected to the first pressurizing system F1 through a pipeline. The first pressurizing system F1 pressurizes the purified gas to 20.4 bar and then connects to the primary membrane separation system G1 through a pipeline. The primary membrane separation system G1 continues to roughly extract helium. The primary non-permeate gas discharged from the primary membrane separation system G1 flows back to the TSA fine degassing system E through a pipeline 5 as a regeneration gas source for the adsorbent. The regenerated regeneration gas returns to the fuel pipeline network through a pipeline 4; the primary permeate gas discharged from the primary membrane separation system G1 is connected to the second pressurizing system F2 through a pipeline. The second pressurizing system F2 pressurizes the primary permeate gas to 21.9 bar and then connects to the secondary membrane separation system G2 through a pipeline. The secondary membrane separation system G2 continues to concentrate helium. The secondary non-permeate gas discharged from the secondary membrane separation system G2 flows back to the inlet of the primary membrane separation system G1 through a pipeline 6 to recover helium; the secondary permeate gas discharged from the secondary membrane separation system G2 is connected to the third pressurizing system F3 through a pipeline. F3 pressurizes the secondary permeate gas to 16 bar and then connects it to the PSA purification system H through a pipeline. The PSA purification system H can remove N2 to 1.5ppm, O2 to 1ppm, and CH4 to 0.4ppm in the permeate gas through various adsorbents in the PSA adsorption tower. The desorbed gas of the PSA purification system has a helium content of 31.25%. It is connected to the fourth pressurizing system F4 through a pipeline. The fourth pressurizing system F4 pressurizes the PSA desorbed gas to 3.7bar and then refluxes it to the inlet pipeline of the TSA fine desorption system E through a pipeline 7 to recover the helium; the crude helium purified by the PSA purification system H is connected to the alloy dehydrogenation system I through a pipeline. The alloy dehydrogenation system I adsorbs hydrogen through alloy hydrogen absorbing materials, and the hydrogen content of the product helium is controlled to be ≤1ppm. The product helium with a purity of 99.999% is sent out of the boundary area through a pipeline 8 for external filling, and the hydrogen released by the regeneration of the alloy hydrogen absorbing material is sent to the flare discharge system through a pipeline 10 to produce 99.999% high-purity hydrogen for export.

[0048] The process parameters and material balance in Example 1 are shown in Tables 1 and 2, wherein Table 1 shows the process parameters and material contents of the front stage of the process, and Table 2 shows the process parameters and material contents of the back stage of the process:

[0049] Table 1 Process parameters and material balance table of the front stage of the process of Example 1

[0050]

[0051] Table 2 Process parameters and material balance table of the latter stage of the process of Example 1

[0052]

[0053]

[0054] Example 2

[0055] Different from Example 1, this embodiment provides a process system for separating and purifying helium from helium-containing natural gas, which is designed for helium-containing natural gas containing oxygen. The process system for separating and purifying helium from helium-containing natural gas also includes a deoxygenation system D, which is arranged between the VPSA decarbonization system and the TSA fine decarbonization system E, and is used to remove oxygen from the helium-containing natural gas. The deoxygenation system D is to react H2 and O2 to generate H2O through a catalytic deoxygenation reaction when the helium-containing natural gas contains oxygen. When the system is short of hydrogen or there is no hydrogen, additional H2 needs to be added to the system.

[0056] The above process system is used to purify helium from the helium-containing natural gas produced in the gas field. The specific process flow is as follows:

[0057] First, the helium-containing natural gas extracted from the gas field is pressurized to 63.5 bar and then enters the pretreatment system A through pipeline 1. After the sulfur and water in the natural gas are removed in the pretreatment system A, the purified gas enters the membrane separation system B for crude extraction of concentrated helium. The non-permeate gas pressure of the membrane separation system B is 63 bar and returns to the natural gas transmission pipeline, while the permeate gas pressure discharged from the membrane separation system B is controlled at 4 bar and enters the VPSA decarbonization system C through the pipeline. In the VPSA decarbonization system C, the CO2, H2S, H2O and heavy hydrocarbons in the permeate gas are removed by using an adsorbent with good adsorption selectivity for CO2, H2S, H2O and heavy hydrocarbons, while ensuring that the recovery rate of H2 and He reaches 99.5%. The low-pressure desorbed gas discharged from the VPSA decarbonization system C is sent to the fuel pipeline network through pipeline 9. The decarburized purified gas treated by the VPSA decarburization system C enters the deoxidation system D, where H2 and O2 react to generate H2O through a catalytic deoxidation reaction. The hydrogen required by the deoxidation system D can be supplemented from the outside through pipeline 3, or the hydrogen separated by the alloy dehydrogenation system I can be returned to the deoxidation system D for recycling through pipeline 10. The deoxidation system D removes O2 from the decarburized purified gas to ≤1ppm.

[0058] The decarbonized purified gas after deoxygenation enters the TSA fine degassing system E, and deeply removes CO2, H2S, H2O and heavy hydrocarbons therein to obtain TSA fine degassing purified gas, in which CO2 and H2O are both removed to ≤1ppm. The TSA fine degassing purified gas enters the first pressurizing system F1 and is pressurized to 20.4bar. After pressurization, it enters the primary membrane separation system G1 to continue to roughly extract helium. The non-permeate gas of the primary membrane separation system G1 enters the TSA fine degassing system E through pipeline 5 as the regeneration gas source for the adsorbent, and the regenerated gas after regeneration returns to the fuel pipeline network through pipeline 4. The permeate gas of the primary membrane separation system G1 enters the second pressurizing system F2 and is pressurized to 21.9bar. After pressurization, it enters the secondary membrane separation system G2 to continue to extract concentrated helium. The non-permeate gas of the secondary membrane separation system G2 enters the inlet of the primary membrane separation system G1 through pipeline 6 to recover helium.

[0059] The permeate gas from the secondary membrane separation system G2 enters the third pressurizing system F3 and is pressurized to 16 bar. The pressurized permeate gas enters the PSA purification system H. Through the various adsorbents in the PSA adsorption tower, the N2 in the secondary permeate gas is removed to 1.5ppm, the O2 is removed to 1ppm, and the CH4 is removed to 0.4ppm. The desorbed gas from the PSA purification system has a helium content of 31.25%. It is pressurized to 3.7bar by the fourth pressurizing system F4 and returned to the entrance of the TSA fine desorption system E through pipeline 7 for recovery. The product gas from the PSA purification system enters the alloy dehydrogenation system I, where hydrogen is adsorbed by the alloy hydrogen absorbing material, and the hydrogen content of the product helium is controlled to ≤1ppm. The product helium with a purity of 99.999% is sent out for filling through pipeline 8. The hydrogen released by the regeneration of the alloy hydrogen absorbing material is returned to the deoxygenation system D through pipeline 10 for recovery and continued deoxygenation. When the helium-containing natural gas introduced into the system contains hydrogen and the amount of hydrogen produced by the reaction of oxygen and hydrogen is sufficient, the high-purity hydrogen separated by the alloy dehydrogenation system I is sent out for sale through pipeline 10. When the helium-containing natural gas introduced into the system does not contain hydrogen, or the amount of hydrogen produced by the reaction of oxygen and hydrogen is insufficient, the hydrogen supplemented from the outside is connected to the deoxidation system D through pipeline 3, and the hydrogen discharged from the alloy dehydrogenation system I is supplemented to the deoxidation system D through the pipeline.

[0060] The process parameters and material balance in Example 2 are shown in Tables 3 and 4, wherein Table 3 shows the process parameters and material contents of the front stage of the process, and Table 4 shows the process parameters and material contents of the back stage of the process:

[0061] Table 3 Process parameters and material balance table of the front stage of the process of Example 2

[0062]

[0063] Table 4 Process parameters and material balance table of the latter stage of the process of Example 2

[0064]

[0065] The present invention is compared with the prior art in the following aspects:

[0066] 1. Process flow

[0067] Since the helium content in natural gas is very low, in order to obtain a certain commercial value, the natural gas processing volume per hour must reach tens of thousands of standard cubic meters. The cryogenic method is mainly used in the scene of natural gas production of LNG. For natural gas used in chemical raw materials, natural gas for vehicles (CNG), power generation and fuel, if only the cryogenic method is used to purify helium in natural gas, the device investment is large, the operation is complicated, and the energy consumption is high. At the same time, the liquefied LNG needs to be gasified into gaseous state for use. Therefore, in the scene where natural gas does not produce LNG, the cryogenic method is generally not used to directly purify helium.

[0068] The present invention provides a process system for separating and purifying helium from helium-containing natural gas. The process system is provided with a VPSA decarbonization system C downstream of a membrane separation system B. The purpose of the VPSA decarbonization system C is to remove CO2, H2O, H2S and C from the natural gas in one step. 2+ . Moreover, the adsorbent of the VPSA decarbonization system can absorb part of the methane, reduce the processing load of subsequent units, and save energy. The existing technology is a process combination removal, such as: MDEA decarbonization, dry desulfurization, TSA purification and other process combinations. This process combination is not as simple as the VPSA decarbonization system process flow and has high investment. In particular, the TSA purification process is mainly used for the deep removal of impurities. If the raw gas contains more CO2 and H2S impurities, the TSA purification device has a large investment and high operating cost. In addition, under the premise of meeting the high recovery rate of helium, the VPSA decarbonization system has strong adaptability to the components of natural gas.

[0069] In the prior art, no deep dehydration and decarbonization system is set before the membrane separation system. Even if the previous system removes CO2 and H2O to less than 10ppm, during the subsequent membrane separation and PSA purification, CO2 and H2O in the helium-rich gas will continue to circulate and accumulate in the circulation system, eventually causing the helium index to be unqualified. The present invention provides a process system for separating and purifying helium from helium-containing natural gas. The process system sets a TSA fine removal system E downstream of the deoxygenation system D. The TSA fine removal system E deeply removes CO2, H2O and H2S in the natural gas to less than 1ppm, and recycles helium for the two downstream membrane separation and PSA purification systems, eliminating the impact of the accumulation of CO2, H2O and H2S impurities.

[0070] The present invention realizes efficient separation of H2 and He, and simultaneously obtains high-purity / electronic-grade He and electronic-grade H2; compared with traditional processes such as traditional chemical methods, the present invention realizes modularization, miniaturization (small footprint), low power consumption, and high efficiency.

[0071] The present invention has the advantages of rapid action and simple operation, and qualified product gas can be obtained within a short time after startup; except for the compressor, there are no moving parts, the failure rate is low, and the operation reliability is high; the maximum recovery rate can be flexibly obtained in a multi-stage manner to achieve the optimization and replacement of the existing production process; the purity, flow rate and pressure of the product gas are highly stable.

[0072] The present invention has a small number of stages in each unit, a small number of inter-stage circulating gas cycles, low energy consumption, and a simple process. The helium in the helium-containing natural gas can be purified to 99% to 99.999% according to the different purity requirements of the terminal for helium.

[0073] 2. Helium recovery rate

[0074] The invention provides a process system for separating and purifying helium from helium-containing natural gas, and the helium recovery rate can reach more than 86%.

[0075] 3. Investment in helium extraction equipment

[0076] According to the investment situation of existing helium extraction devices, the process system for separating and purifying helium from helium-containing natural gas proposed in the present invention can save about 35% of investment compared with cryogenic helium extraction devices.

[0077] 4. Issues of dehydrogenation and oxygen removal in helium extraction equipment

[0078] According to the conditions of natural gas, if the natural gas contains hydrogen, the existing technology is to add additional O2 or air, and then react H2 and O2 to generate H2O through a catalytic deoxygenation reaction, and then remove H2O and excess O2 separately, thereby achieving the purpose of purifying H2 in He.

[0079] The catalytic oxidation method to remove H2 from He will have the following problems:

[0080] 1) Since air needs to be actively introduced, other trace impurities in the air will be brought in, resulting in the final He concentration not meeting the standard.

[0081] 2) Catalytic oxidation method: the amount of O2 is calculated based on the amount of H2. Fluctuations in upstream flow and content will cause fluctuations in the process, bringing about technical and safety problems.

[0082] 3) The process is more complicated. The O2 catalytic method requires additional equipment such as liquid oxygen storage tanks, deoxygenation towers, and drying and dehydration towers.

[0083] 4) Catalytic oxidation dehydrogenation and oxygenation requires the configuration of a series of auxiliary devices and produces a large amount of solid waste, which not only requires huge investment (especially the economic efficiency is worse at small flow rates), but also is a huge waste of resources and energy. At the same time, due to the laying of auxiliary devices, a large amount of land resources will be occupied.

[0084] The alloy dehydrogenation system I of the present invention removes excess H2 after deoxidation by using special alloy materials for separation, and no reaction is required. The entire separation process is carried out in the environment and temperature of circulating water, which is safer. Special alloy materials separate H2 and He, and are suitable for any ratio of H2 / He. In addition, no other gases are introduced during the entire process, and even if the upstream gas composition changes or fluctuates, it will not affect the stability and safety of the process.

[0085] The present invention uses special alloy materials to separate H2 and He, rather than using catalytic combustion to remove H2 from He, but achieves perfect separation. The by-product ultra-pure H2 is both a highly efficient fuel and an important chemical raw material.

[0086] If the natural gas contains oxygen, the existing technology is to add additional H2, and then react H2 and O2 to generate H2O through a catalytic deoxygenation reaction. The excess hydrogen is separated by special alloy materials, and the separated hydrogen is pressurized and returned to the inlet of the deoxygenation system to continue to react with the oxygen in the natural gas. Compared with the existing technology, the hydrogen consumption is low and the helium recovery rate is high.

[0087] Compared with the cryogenic technology, the invention can save about 35% of investment under the condition of the same gas volume and helium content. In addition, it has the advantages of small footprint, simple process and low energy consumption.

[0088] The number of stages of the membrane separation crude purification system is 1 to N (N is a natural number from 1 to 4).

[0089] The membrane material in the membrane separator is mainly polyimide (PI) fiber membrane.

[0090] The outer shell of the membrane separator is similar to a shell and tube heat exchanger, which contains tens of thousands of tiny hollow fiber filaments.

[0091] The VPSA decarbonization system C process uses 4 to 12 adsorption towers, the pressure equalization times are 1 to 7 times, and the adsorbent is regenerated by vacuum pumping. The purpose of the VPSA decarbonization system C is to remove CO2, H2O, H2S and C from natural gas in one step. 2+ . Moreover, the adsorbent of the VPSA decarbonization system can absorb part of the methane, reduce the processing load of subsequent units, and save energy. The existing technology is a process combination removal, such as: MDEA decarbonization, dry desulfurization, TSA purification and other process combinations. This process combination is not as simple as the VPSA decarbonization system process flow and has high investment. In particular, the TSA purification process is mainly used for the deep removal of impurities. If the raw gas contains more CO2 and H2S impurities, the TSA purification device has a large investment and high operating cost. In addition, under the premise of meeting the high recovery rate of helium, the VPSA decarbonization system has strong adaptability to the components of natural gas.

[0092] The process flow of TSA fine desorption system E uses 2 to 4 adsorption towers with a regeneration temperature of 160 to 220°C. TSA fine desorption system E removes H2O to 1ppm, CO2 to 1ppm, and H2S to 1ppm. TSA fine desorption system E deeply removes CO2, H2O and H2S from natural gas, and recycles helium for the downstream membrane separation and PSA purification systems, eliminating the impact of CO2, H2O and H2S impurity accumulation.

[0093] The H adsorption tower of the PSA purification system uses 4 to 6 adsorption towers, the pressure equalization times are 1 to 3 times, and the adsorbent is regenerated by flushing or vacuuming.

[0094] Alloy dehydrogenation system I removes hydrogen from helium to 1ppm. Alloy hydrogen absorbing materials are mainly composed of titanium, manganese, zirconium, nickel, vanadium and a variety of rare earths / rare metals. Hydrogen absorbing materials can reversibly absorb and release a large amount of H2 just like a sponge absorbs water. Once H2 comes into contact with the alloy hydrogen absorbing material, it can be decomposed into H atoms on its surface, and then the H atoms diffuse into the interior of the material until they react with the material to form hydrides. At this time, H2 is stored in the crystallization point of the alloy hydrogen absorbing material in an atomic state (the gap between the tetrahedron and the octahedron). Alloy hydrogen absorbing material is a material that can achieve reversible absorption and release of H2, and has significant advantages such as large H2 storage capacity, low storage pressure, small device size, and convenient use in limited space. When the external pressure and temperature change, the hydride will decompose and reversibly release hydrogen with a purity of more than 99.999%, and the hydride will decompose again to react back to the intrinsic state of the material.

[0095] The alloy is a material that is highly sensitive to H2. When He / H2 mixed gas is passed into the alloy at low temperature (e.g. 10°C), the alloy adsorbs H2 but not He, and He is discharged through the exhaust port, achieving the separation of H2 and He to obtain high-purity He. At the same time, H2 is desorbed at high temperature (e.g. 200°C for the first stage and 350°C for the second stage) to obtain H2 with a purity of more than 99.999%.

[0096] Alloy dehydrogenation system D regeneration heats and cools the alloy adsorption column through heat transfer oil. It is equipped with a circulating heat engine and a circulating cold machine, using the same heat transfer oil medium. When the alloy adsorption column needs to be heated, the high-temperature heat transfer oil of 200-220℃ in the circulating heat engine is passed into the adsorption column interlayer through valve switching to heat the adsorption column; when the alloy adsorption column needs to be cooled, the cold oil of 0-10℃ in the circulating cold machine is passed into the adsorption column interlayer through valve switching to quickly cool the adsorption column. After the alloy adsorption column is regenerated, it is switched to hydrogen absorption state through valve switching. Alternating switching realizes continuous H2 absorption and release production.

[0097] Compared with the existing patented technology of adding O2 or air catalytic dehydrogenation technology, other trace impurities (CO2, Ar and rare gases) in the air will be introduced, and the device will increase the investment and land occupation of equipment such as liquid oxygen storage tanks, deoxygenation towers, and drying and dehydration towers. The regular replacement of catalysts in catalytic dehydrogenation technology will produce a large amount of solid waste and increase operating costs.

[0098] Alloy dehydrogenation system I is a special alloy material that separates H2 and He, rather than removing H2 from He by catalysis. The alloy dehydrogenation system can recover byproduct H2, which can be converted into high-purity hydrogen. Hydrogen is not only an efficient fuel, but also an important chemical raw material, and also a gas commonly used in the electronics industry.

[0099] In summary, domestic helium is mainly obtained from non-condensable gas and BOG gas in the natural gas liquefaction process. The present invention provides a process system for directly separating and purifying helium from helium-containing natural gas to produce high-purity helium with a purity of ≥99.999 vol%, and the helium recovery rate reaches more than 95%.

[0100] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A process system for separating and purifying helium from helium-containing natural gas, characterized in that: It includes a pretreatment system A, a membrane separation system B, a VPSA decarburization system C, a TSA fine decarburization system E, a first pressurization system F1, a primary membrane separation system G1, a second pressurization system F2, a secondary membrane separation system G2, a third pressurization system F3, a PSA purification system H and an alloy dehydrogenation system I, which are sequentially connected through pipelines, and a fourth pressurization system F4 arranged between the PSA purification system H and the TSA fine decarburization system E; The permeate gas discharged from the membrane separation system B is used to enter the VPSA decarbonization system C, and the non-permeate gas is used to be sent to the natural gas pipeline network; the low-pressure desorbed gas discharged from the VPSA decarbonization system C is used to be sent to the fuel pipeline network; the TSA desorbed gas discharged from the TSA fine decarbonization system E is used to be sent to the fuel pipeline network; the primary permeate gas discharged from the primary membrane separation system G1 is used to enter the second pressurization system F2, and the primary non-permeate gas is used to flow back to the TSA fine decarbonization system E; The secondary permeate gas discharged from the secondary membrane separation system G2 is used to enter the third pressurization system F3, and the secondary non-permeate gas is used to flow back to the primary membrane separation system G1; the crude helium gas purified by the PSA purification system H is used to enter the alloy dehydrogenation system I, and the PSA desorption gas is pressurized by the fourth pressurization system F4 and then flows back to the TSA fine dehydrogenation system E.

2. The process system for separating and purifying helium from helium-containing natural gas according to claim 1, characterized in that: It also includes a deoxygenation system D. When the helium-containing natural gas entering the pretreatment system A does not contain oxygen, the purified natural gas discharged from the VPSA decarbonization system C directly enters the TSA fine decarbonization system E; when the helium-containing natural gas entering the pretreatment system A contains oxygen, the purified natural gas discharged from the VPSA decarbonization system C is passed into the deoxygenation system D, and the purified natural gas is deeply deoxygenated through the deoxygenation system D before entering the TSA fine decarbonization system E; when the helium-containing natural gas entering the pretreatment system A contains oxygen but does not contain hydrogen, or the amount of hydrogen produced by the reaction of oxygen and hydrogen is insufficient, hydrogen is supplemented from the outside to the deoxygenation system D through a pipeline, and at the same time, the hydrogen discharged from the alloy dehydrogenation system I is supplemented to the deoxygenation system D through a pipeline.

3. The process system for separating and purifying helium from helium-containing natural gas according to claim 1, characterized in that: The pressure of the permeate gas discharged from the membrane separation system B is controlled at 0.05-0.4 MPa.

4. The process system for separating and purifying helium from helium-containing natural gas according to claim 1, characterized in that: The membrane separator materials of the membrane separation system B, the primary membrane separation system G1 and the secondary membrane separation system G2 are all made of organic fiber membranes.

5. The process system for separating and purifying helium from helium-containing natural gas according to claim 1, characterized in that: The TSA fine removal system E removes H2O to ≤3ppm, CO2 to ≤3ppm, and H2S to ≤3ppm in natural gas through temperature swing adsorption.

6. The process system for separating and purifying helium from helium-containing natural gas according to claim 1, characterized in that: The compressors used in the first pressurizing system F1, the second pressurizing system F2, the third pressurizing system F3 and the fourth pressurizing system F4 are reciprocating compressors or diaphragm compressors; the first pressurizing system F1 is used to pressurize the natural gas purified by the TSA degassing system E to 1.0-2.2 MPa; the second pressurizing system F2 is used to pressurize the primary permeate gas of 20-100 kPa to 1.2-2.4 MPa; the third pressurizing system F3 is used to pressurize the secondary permeate gas of 0.2-0.4 MPa to 1.6-1.8 MPa; the fourth pressurizing system F4 is used to pressurize the PSA desorption gas to 0.4-0.5 MPa.

7. The process system for separating and purifying helium from helium-containing natural gas according to claim 1, characterized in that: The PSA purification system H removes N2 to 1.5 ppm and CH4 to 0.4 ppm in the secondary permeate gas by pressure swing adsorption.

8. The process system for separating and purifying helium from helium-containing natural gas according to claim 1, characterized in that: The VPSA decarbonization system C adopts vacuum pressure swing adsorption, and its process flow adopts 4 to 12 adsorption towers, and the number of pressure equalization is 1 to 7 times.

9. The process system for separating and purifying helium from helium-containing natural gas according to claim 1, characterized in that: The PSA purification system H uses 4 to 6 adsorption towers, the pressure equalization times are 1 to 3 times, and the adsorbent is regenerated by flushing or vacuuming; the PSA purification system H includes a precooling heat exchanger, a downstream gas buffer tank V and several PSA adsorption towers filled with different adsorbents; The process steps of the PSA purification system H include: the secondary permeate gas from the third pressurizing system F3 after being pressurized enters the precooling heat exchanger for precooling, reducing the temperature of the secondary permeate gas to -10 to -40°C, and then enters each PSA adsorption tower in turn, and each PSA adsorption tower adsorbs one impurity gas; For a PSA adsorption tower, its working process includes: After the adsorption process is completed, H2 and He with higher internal pressure are recovered to the regenerated PSA adsorption tower with lower pressure according to the adsorption direction for equalization and pressure reduction operation; After the pressure equalization and pressure reduction operation is completed, first, the helium-hydrogen mixed gas at the top of the PSA adsorption tower is quickly put into the downstream gas buffer tank V according to the adsorption direction. These gases will be used as the regeneration gas source for the adsorbent; After the forward release process is completed, the pressure in the PSA adsorption tower is reduced to 0.03MPa in the reverse direction of adsorption. At this time, the impurities in the adsorbent begin to be desorbed, and the reverse release desorbed gas will be sent to the fourth pressurization system F4 to recover helium; Next, the PSA adsorption tower is flushed with helium in the forward-degassing buffer tank V in the opposite direction of adsorption to ensure that the impurities in the adsorbent are completely desorbed. The flushing desorbed gas will also enter the fourth pressurizing system F4 to recover the helium; After the flushing and regeneration process is completed, the pressure of the adsorption tower is evenly increased in sequence using H2 and He with higher pressure from other adsorption towers; After the pressure equalization and pressure boosting process is completed, the pressure of the adsorption tower is slowly and steadily increased to the adsorption pressure using the product helium-hydrogen mixed gas through the pressure boost regulating valve.

10. The process system for separating and purifying helium from helium-containing natural gas according to claim 2, characterized in that: The alloy hydrogen absorption material of the alloy hydrogen absorption system I is mainly composed of titanium, manganese, zirconium, nickel, lanthanum, vanadium and various rare earths / rare metals; the alloy dehydrogenation system I is composed of a primary alloy dehydrogenation system and a secondary alloy dehydrogenation system, the primary alloy dehydrogenation system includes a filter and an alloy adsorption column, and the secondary alloy dehydrogenation system includes an alloy adsorption column; The dehydrogenation process steps of the alloy dehydrogenation system I include: (1) The mixed gas passes through the filter of the PSA purification system H to remove the adsorbent dust, and then flows through the alloy adsorption columns of the primary and secondary alloy dehydrogenation systems in sequence; In a low temperature environment of -10 to -40°C, the alloy adsorption column adsorbs H2 but not He, thereby achieving effective separation of H2 and He and producing high-purity helium products; (2) After the alloy adsorption column adsorbs hydrogen, it needs to be heated and regenerated; heating and regeneration is to heat the alloy adsorption column by means of heat transfer oil or electric heating to promote the desorption of hydrogen at high temperature to obtain a high-purity helium product; then, the hydrogen is extracted by a vacuum pump for export or recycled to the deoxidation system D for deoxidation; (3) After the heating regeneration is completed, cooling regeneration is performed. By switching the valve, cold oil or compressed air with a temperature of 0 to 10° C. in the circulating cooler is introduced into the interlayer of the alloy adsorption column to achieve rapid cooling of the alloy adsorption column; (4) After the alloy adsorption column is cooled to a low pressure state, the pressure of the alloy adsorption column is slowly increased to the hydrogen absorption pressure using the raw material low-temperature hydrogen-helium mixed gas.

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