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

Abstract

The utility model discloses a process system for separating and purifying helium from helium-containing natural gas. Comprising a pretreatment system, a membrane separation system, a VPSA decarburization system, a TSA refined removal system, a first pressurization system, a first-stage membrane separation system, a second pressurization system, a second-stage 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, and a fourth pressurization system 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. The process system disclosed by the utility model can be used for directly separating and purifying helium from helium-containing natural gas which is exploited from a gas field and is pretreated, the helium recovery rate is high, the process flow is simple, and the energy consumption is low.

Description

Technical Field

[0001] This utility model relates to the field of helium extraction technology, and in particular to a process system for separating and purifying helium from helium-containing natural gas. Background Technology

[0002] Helium, a non-renewable rare gas, plays a crucial role in scientific research, semiconductors, medicine, petrochemicals, aerospace, and maritime industries, with its demand increasing year by year. Helium is primarily derived from air, some natural gas, and associated gas, with helium-rich natural gas (natural gas with a helium content greater than 0.1%) currently being the most stable and reliable source. Nevertheless, most natural gas contains less than 0.05% helium, leading to a major reliance on imports.

[0003] To improve helium extraction efficiency and reduce energy consumption, researchers have explored various technological pathways for helium extraction from natural gas. One common method is extracting helium from the natural gas liquefaction process, such as the method described in patent CN210237128U for extracting high-purity helium from low-helium-content BOG (Big Off Gas, referring to the large amount of mixed gas produced after LNG production). This method is mainly used for tail gas purification during natural gas liquefaction. Another method is a system described in patent CN212538459U for co-producing helium using an LNG production unit. This system utilizes flash vapor generated during LNG production and storage for dehydrogenation and helium purification. However, these methods are limited to recovering and extracting helium during natural gas liquefaction, and such methods are not widely applied in other scenarios such as natural gas chemical industry, power generation, CNG, or vehicle natural gas in the current technology.

[0004] While existing membrane separation, VPSA (Pressure Swing Adsorption) decarbonization, TSA (Temperature Swing Adsorption) fine removal, and alloy dehydrogenation technologies can be used for helium extraction from natural gas, they are mostly applied in liquefied natural gas (LNG) processes. Directly implementing helium extraction technology in natural gas chemical and power generation scenarios faces a series of challenges, including high investment, complex operation, and high energy consumption. The main problem is the lack of sufficient consideration for the efficient removal of various impurities and the efficient recovery of helium during natural gas processing. In particular, the TSA fine removal process has poor adaptability to the impurity content in the feed gas, potentially leading to high operating costs, and the catalytic dehydrogenation process introduces other impurities (such as CO2, Ar, and rare gases), causing additional problems. Furthermore, although cryogenic methods can achieve helium extraction, the equipment is complex, requires high investment, and consumes a lot of energy; the liquefied natural gas produced during the process also needs to be gasified, adding extra operational steps. Utility Model Content

[0005] This invention provides a process system for separating and purifying helium from helium-containing natural gas, which can directly separate and purify helium from helium-containing natural gas extracted from gas fields and after pretreatment.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0007] A process system for separating and purifying helium from helium-containing natural gas includes a pretreatment system A, a membrane separation system B, a VPSA decarbonization system C, a TSA fine decarbonization 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, connected sequentially by pipelines. A fourth pressurization system F4 is located between the PSA purification system H and the TSA fine decarbonization system E. The permeate gas discharged from the membrane separation system B is used to enter the VPSA decarbonization system C, while the non-permeate gas is used to feed into the natural gas pipeline network. The VPSA decarbonization system C... The discharged low-pressure desorbed gas is sent to the fuel pipeline network; the TSA desorbed gas discharged from the TSA fine removal system E is sent to the fuel pipeline network; the primary permeate gas discharged from the primary membrane separation system G1 is sent to the second pressurization system F2, and the primary non-permeate gas is returned to the TSA fine removal system E; the secondary permeate gas discharged from the secondary membrane separation system G2 is sent to the third pressurization system F3, and the secondary non-permeate gas is returned to the primary membrane separation system G1; the crude helium purified by the PSA purification system H is sent to the alloy dehydrogenation system I, and the PSA desorbed gas is pressurized by the fourth pressurization system F4 and then returned to the TSA fine removal system E.

[0008] Preferably, a deoxygenation system D is also included, which is disposed between the VPSA decarbonization system and the TSA fine decarbonization system E, for removing oxygen from helium-containing natural gas.

[0009] Preferably, the pressure of the permeate gas discharged from the membrane separation system B is controlled at 0.05 to 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 organic fiber membranes.

[0011] Preferably, the compressors used in the first pressurization system F1, the second pressurization system F2, the third pressurization system F3, and the fourth pressurization system F4 are reciprocating compressors or diaphragm compressors; the first pressurization system F1 is used to pressurize the natural gas purified by the TSA purification system E to 1.0-2.2 MPa; the second pressurization system F2 is used to pressurize the primary permeate gas (20-100 kPa) to 1.2-2.4 MPa; the third pressurization system F3 is used to pressurize the secondary permeate gas (0.2-0.4 MPa) to 1.6-1.8 MPa; and the fourth pressurization system F4 is used to pressurize the PSA desorption gas to 0.4-0.5 MPa.

[0012] Preferably, the VPSA decarbonization system C includes a connected VPSA adsorption tower group and a VPSA pressure equalization pipeline system. The VPSA adsorption tower group contains 4 to 12 VPSA adsorption towers arranged in parallel. The VPSA pressure equalization pipeline system is arranged between each VPSA adsorption tower.

[0013] Preferably, the PSA purification system H includes a PSA equalization pipeline system, and a precooling heat exchanger, a PSA adsorption tower, a forward venting buffer tank V, and a pressure regulating valve installed on the PSA equalization pipeline system. The precooling heat exchanger is used to cool the gas entering the PSA purification system H; the PSA adsorption tower is used to remove impurities from the cooled gas; and the forward venting buffer tank V is used to temporarily store the gas after impurity removal by the PSA adsorption tower and to provide helium to flush the PSA adsorption tower.

[0014] Preferably, the alloy dehydrogenation system I includes an alloy dehydrogenation pipeline system, an alloy adsorption column and a vacuum pump disposed on the alloy dehydrogenation pipeline system, wherein the alloy adsorption column is used to adsorb hydrogen in the gas; and the vacuum pump is used to extract the hydrogen outward or recover it to the deoxygenation system D for deoxygenation.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) This utility model can directly separate and purify helium from helium-containing natural gas extracted from gas fields and after pretreatment. By setting up a multi-stage coupled process such as a pretreatment system, a membrane separation system, a VPSA decarbonization system, a TSA fine decarbonization system, a PSA purification system and an alloy dehydrogenation system, the helium in helium-containing natural gas can be purified to 99% to 99.999%. The purified helium has high purity and can be widely used for various needs.

[0017] (2) The helium recovery rate of this utility model is as high as 86% or more, which is more efficient and less energy-consuming than traditional methods; the process is simple, the operation is safe and stable, and the risks brought about by complex operation are avoided.

[0018] (3) This utility model adopts an advanced membrane separation system, PSA purification system and alloy dehydrogenation system, which greatly reduces equipment investment and floor space. The miniaturized design makes it easier to apply and maintain. At the same time, the use of alloy dehydrogenation system to achieve efficient separation of H2 and He not only greatly reduces hydrogen consumption, but also improves helium recovery rate. Unlike the traditional catalytic combustion method, it avoids the risk of introducing impurities and generating a large amount of solid waste, making it more environmentally friendly and economical. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process system for separating and purifying helium from helium-containing natural gas in an embodiment of this utility model;

[0020] Figure 2 This is a schematic diagram of the structure of the PSA purification system H in this embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of the alloy dehydrogenation system I in this embodiment of the present invention.

[0022] In the above figures, the component numbers are as follows:

[0023] A. Pretreatment system; B. Membrane separation system; C. VPSA decarbonization system; D. Deoxygenation system; E. TSA fine decarbonization system; F1. First pressurization system; F2. Second pressurization system; F3. Third pressurization system; F4. Fourth pressurization system; G1. Primary membrane separation system; G2. Secondary membrane separation system; H. PSA purification system; I. Alloy dehydrogenation system. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this 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, designed for processing oxygen-free helium-containing natural gas. The system includes a pretreatment system A, a membrane separation system B, a VPSA decarbonization system C, a TSA fine dehydrogenation 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, as well as a fourth pressurization system F4 disposed between the PSA purification system H and the TSA fine dehydrogenation system E.

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

[0028] Please see 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. Based on the hydrogen content in the product gas of the PSA purification system H, the alloy dehydrogenation system I can employ 1 to 3 stages of alloy columns. In the alloy dehydrogenation system I, the hydrogen-helium inlet pipe DP1 is connected to multiple inlet pipes at the top of the primary alloy adsorption column; multiple outlet pipes at the bottom of the primary alloy adsorption column are connected to the main inlet pipe for secondary alloy dehydrogenation; the main inlet pipe for secondary alloy dehydrogenation is connected to multiple inlet pipes at the top of the secondary alloy adsorption column; multiple outlet pipes at the bottom of the secondary alloy adsorption column are connected to the main product helium outlet pipe DP2; multiple outlet pipes at the top of the primary alloy adsorption column are connected to the main product hydrogen outlet pipe DP4; and multiple outlet pipes 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; multiple outlet pipes at the bottom of the secondary alloy adsorption column are connected to the helium recovery main pipe DP3; multiple outlet pipes at the bottom of the primary alloy adsorption column are connected to the inlet main pipe of the primary alloy dehydrogenation vacuum pump; the outlet pipe of the primary alloy dehydrogenation vacuum pump is connected to the alloy dehydrogenation venting main pipe DP5; multiple outlet pipes at the bottom of the secondary alloy adsorption column are connected to the inlet main pipe of the secondary alloy dehydrogenation vacuum pump; the outlet pipe of the secondary alloy dehydrogenation vacuum pump is connected to the alloy dehydrogenation venting main pipe DP5; the filter is installed on the hydrogen-helium inlet pipe DP1.

[0029] The pretreatment system A performs pretreatment such as desulfurization, decarbonization, dehydration, and dehydrocarbonization on the extracted helium-containing raw natural gas to obtain purified natural gas. After pretreatment, the 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%–4% (this data is mainly related to the pressure of the raw natural gas and the helium volume fraction). The permeate is sent to the VPSA decarbonization system C through a pipeline. The non-permeate is returned to the natural gas pipeline network through pipeline 2. The main purpose of this step is to use a membrane separator made of a special polymer material. Based on the differences in the solubility and diffusion coefficient of different gases in the natural gas, the relative permeability of different gases in the material varies. According to this characteristic, gases with relatively fast permeation rates, such as H2, He, CO2, H2O, and H2S, are enriched on the permeate side of the material after passing through it, while gases with relatively slow permeation rates, such as methane (CH4), nitrogen (N2), carbon monoxide (CO), and argon (Ar), are enriched on the stagnation side of the material, thereby achieving the purpose of separating the mixed gases.

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

[0032] The VPSA decarbonization system C removes CO2, H2O, H2S, and C from the permeate gas. 2+ Impurity removal. The main purpose of this step is to remove "fast gas" impurities in the membrane separation system while ensuring a high helium recovery rate, preventing their accumulation in the system during helium recycling and thus avoiding excessive helium impurities in the product. The low-pressure desorbed gas generated by the VPSA decarbonization system C is sent to the fuel pipeline network. The VPSA decarbonization system C employs vacuum pressure swing adsorption, and its process uses 4 to 12 adsorption towers, with 1 to 7 pressure equalization cycles. Adsorbent regeneration is performed using a vacuum method.

[0033] The TSA purification system E removes H2O, CO2, and H2S from natural gas to 1 ppm through temperature-switching adsorption. The TSA purification system E utilizes temperature-switching adsorption (TSA) to deeply remove H2O, CO2, and H2S from natural gas. The regeneration gas is the primary non-permeable gas from the primary membrane separation system G1. The TSA purification system E process uses 2–4 adsorption towers, with a regeneration temperature of 160–220℃.

[0034] The first pressurization system F1 pressurizes the natural gas after deep purification by the TSA fine removal 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 gas separated by the membrane.

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

[0036] The primary membrane separation system G1 further enriches helium in the pressurized purified natural gas through a primary membrane separator. The primary permeate gas is then piped into the second pressurization system F2. The primary non-permeate gas is connected to the TSA purification system E via pipe 5. The main purpose of this step is to further enrich the helium in the natural gas using the primary membrane separator.

[0037] The second pressurization system F2 pressurizes the primary permeate gas from 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, thereby increasing the osmotic pressure of the secondary membrane separator and improving the permeability of the membrane separation gas. The compressor used in the second pressurization system F2 is a reciprocating compressor or a diaphragm compressor. Reciprocating compressors should preferably use a packing leakage recovery system to reduce helium loss.

[0038] The secondary membrane separation system G2 further concentrates the pressurized primary permeate gas through a secondary membrane separator, and the secondary permeate gas is then piped into the third pressurization system F3. The secondary non-permeate gas is connected to the inlet pipe of the primary membrane separation system G1 via pipe 6. This step operates on the same principle as the primary membrane separation system G1, with the main purpose of further concentrating helium in the primary permeate gas using the secondary membrane separator. To improve helium recovery, the secondary non-permeate gas is returned to the primary membrane separator for recovery. The primary permeate gas passes through the secondary membrane separator, concentrating hydrogen and helium in the feed gas to over 85%.

[0039] The membrane separators 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 membranes.

[0040] The third pressurization system F3 pressurizes the secondary permeate gas from 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, ensuring the adsorption effect of impurities other than hydrogen and helium, and the helium recovery rate. The compressor used in the third pressurization system F3 is a diaphragm compressor.

[0041] The PSA purification system H removes N2 to 1.5 ppm and CH4 to 0.4 ppm from the secondary permeate gas via pressure swing adsorption (PSA). The PSA desorbed gas has a high helium content and is recovered to the fourth pressurization system F4, improving the system's helium recovery rate. The PSA product hydrogen and helium are piped to the alloy dehydrogenation system I for hydrogen removal. The PSA purification system desorbed gas enters the fourth pressurization system F4 and is pressurized to 0.4–0.5 MPa, then returns to the inlet of the TSA fine dehydrogenation system E for recovery via pipeline 7.

[0042] Specifically, the process steps of the PSA purification system H include: the secondary permeate gas, pressurized from the third pressurization system F3, enters the precooling heat exchanger for precooling, reducing the temperature of the secondary permeate gas to -10 to -40°C, and then sequentially enters each PSA adsorption tower, with each PSA adsorption tower adsorbing one type of 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 regenerated, lower-pressure PSA adsorption tower for pressure equalization and depressurization operation; after the pressure equalization and depressurization 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 outflow buffer tank V, and these gases will be used as adsorbents. The regeneration gas source is as follows: After the forward release process is completed, the pressure inside the PSA adsorption tower is reduced to 0.03 MPa in the reverse adsorption direction. At this time, impurities in the adsorbent begin to desorb, and the reverse release desorption gas will be sent to the fourth pressurization system F4 to recover helium. Then, helium in the forward release gas buffer tank V is used to flush the PSA adsorption tower in the reverse adsorption direction to ensure that the impurities in the adsorbent are completely desorbed. The flushing desorption gas will also enter the fourth pressurization system F4 to recover helium. After the flushing and regeneration process is completed, H2 and He from other adsorption towers with higher pressure are used to equalize and pressurize the adsorption tower in sequence. After the equalization and pressurization process is completed, the pressure of the adsorption tower is slowly and steadily increased to the adsorption pressure by using the product helium-hydrogen mixed gas through the pressure regulating valve.

[0043] The alloy dehydrogenation system I removes hydrogen from the product gas of the PSA purification system H to <1 ppm. Its principle involves a hydrogen-absorbing alloy material. Once H2 comes into contact with the hydrogen-absorbing material, it decomposes into H atoms on its surface. These H atoms then diffuse into the interior of the material until they react with the material to form hydrides. At this point, H2 is stored in atomic form within the crystallization points of the hydrogen-absorbing material (the interstitial positions between tetrahedrons and octahedrons).

[0044] Specifically, the dehydrogenation process of the alloy dehydrogenation system I includes the following steps: the mixed gas passes through the PSA purification system H to filter out adsorbent dust, and then flows sequentially through the alloy adsorption columns of the primary and secondary alloy dehydrogenation systems; in a low-temperature environment of -10~-40℃, the alloy adsorption column adsorbs H2 but not 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 regenerated by heating; heating regeneration is achieved by heating the alloy adsorption column with heat transfer oil or electric heating to promote the desorption of hydrogen at high temperature, obtaining a high-purity helium product; then, the hydrogen is extracted and sold externally using a vacuum pump; after heating regeneration is completed, cooling regeneration is performed by introducing cold oil or compressed air at a temperature of 0~10℃ from the circulating chiller into the jacket 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 pressure of the alloy adsorption column is slowly increased to the hydrogen adsorption pressure using the raw material low-temperature hydrogen-helium mixed gas.

[0045] The alloy hydrogen absorption system I primarily consists of titanium, manganese, zirconium, nickel, lanthanum, vanadium, and various rare earth / rare metals. The H2 and He separation material is designed for reversible H2 absorption and release. During selective H2 absorption, H2 reacts chemically with the material to form hydrides, thus storing gaseous H2 in a solid form. Once the absorption bed is saturated, it enters a regeneration process. Heating the material releases the absorbed H2, regenerating the H2-absorbing material and achieving H2 and He separation.

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

[0047] 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. In pretreatment system A, impurities such as sulfur and water are removed from the helium-containing natural gas to obtain purified gas. This purified gas then enters the membrane separation system B through a pipeline for coarse helium enrichment. The non-permeable gas discharged from membrane separation system B has a pressure of 63 bar and is sent to the natural gas pipeline network through pipeline 2. The permeable gas discharged from membrane separation system B has a pressure controlled at 4 bar and enters the VPSA decarbonization system C through a pipeline. In the VPSA decarbonization system C, an adsorbent with good selectivity for CO2, H2S, H2O, and heavy hydrocarbons is used to remove CO2, H2S, H2O, and heavy hydrocarbons from the permeable gas, while ensuring a 99.5% recovery rate for H2 and He. The low-pressure desorbed gas discharged from the VPSA decarbonization system C is sent to the fuel pipeline network through pipeline 9. After being treated by the VPSA decarbonization system C, the decarbonized and purified gas enters the TSA fine decarbonization system E through a pipeline. The TSA fine decarbonization system E deeply removes CO2, H2S, H2O and heavy hydrocarbons, reducing the CO2 and H2O content to ≤1ppm. The desorbed gas from the TSA fine decarbonization system E is sent to the fuel pipeline network through pipeline 4.The purified gas, after being treated by the TSA fine-removal system E, is connected to the first pressurization system F1 via a pipeline. The first pressurization system F1 pressurizes the purified gas to 20.4 bar and then connects it to the first-stage membrane separation system G1 via a pipeline. The first-stage membrane separation system G1 continues to coarsely extract helium. The primary non-permeable gas discharged from the first-stage membrane separation system G1 flows back to the TSA fine-removal system E via pipeline 5, serving as the regeneration gas source for the adsorbent. The regenerated gas is then returned to the fuel network via pipeline 4. The primary permeable gas discharged from the first-stage membrane separation system G1 is connected to the second pressurization system F2 via a pipeline. The second pressurization system F2 pressurizes the primary permeable gas to 21.9 bar and then connects it to the second-stage membrane separation system G2 via a pipeline. The second-stage membrane separation system G2 continues to enrich helium. The secondary non-permeable gas discharged from the second-stage membrane separation system G2 flows back to the inlet of the first-stage membrane separation system G1 via pipeline 6 to recover helium. The secondary permeable gas discharged from the second-stage membrane separation system G2 is connected to the third pressurization system F3 via a pipeline. F3 pressurizes the secondary permeate gas to 16 bar and connects it to the PSA purification system H through a pipeline. The PSA purification system H uses multiple adsorbents in the PSA adsorption tower to remove N2 to 1.5 ppm, O2 to 1 ppm, and CH4 to 0.4 ppm from the permeate gas. The desorbed gas from the PSA purification system has a helium content of 31.25% and is connected to the fourth pressurization system F4 through a pipeline. The fourth pressurization system F4 pressurizes the PSA desorbed gas to 3.7 bar and then returns it to the inlet pipeline of the TSA fine desorption system E through pipeline 7 to recover 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 adsorption material, and the hydrogen content of the product helium is controlled to be ≤1 ppm. The product helium with a purity of 99.999% is sent out of the boundary area for external filling through pipeline 8. The hydrogen released by the regeneration of the alloy hydrogen adsorption material is sent to the flare discharge system through pipeline 10 to produce 99.999% high-purity hydrogen for external sale.

[0048] The process parameters and material balances in Example 1 are shown in Tables 1 and 2, where Table 1 shows the process parameters and material content for the initial stage of the process, and Table 2 shows the process parameters and material content for the final stage of the process.

[0049] Table 1. Process parameters and material balance table for the front-end of the process in Example 1

[0050]

[0051] Table 2. Process parameters and material balance table for the later stage of process in Example 1

[0052]

[0053] Example 2

[0054] Unlike Example 1, this example provides a process system for separating and purifying helium from helium-containing natural gas, specifically designed for helium-containing natural gas containing oxygen. This process system further includes a deoxygenation system D, located between the VPSA decarbonization system and the TSA refining system E, for removing oxygen from the helium-containing natural gas. When the helium-containing natural gas contains oxygen, the deoxygenation system D reacts H2 and O2 to generate H2O through a catalytic deoxygenation reaction. When the system lacks hydrogen or has no hydrogen, additional H2 needs to be added to replenish the system.

[0055] The above-mentioned process system is used to purify helium-containing natural gas extracted from the gas field. The specific process flow is as follows:

[0056] 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. In pretreatment system A, sulfur and water are removed from the natural gas, and the purified gas enters the membrane separation system B for coarse helium enrichment. The non-permeable gas pressure of membrane separation system B is 63 bar and is returned to the natural gas transmission pipeline, while the permeable gas pressure discharged from membrane separation system B is controlled at 4 bar and enters the VPSA decarbonization system C through pipeline. In VPSA decarbonization system C, an adsorbent with good selectivity for CO2, H2S, H2O, and heavy hydrocarbons is used to remove CO2, H2S, H2O, and heavy hydrocarbons from the permeable gas, while ensuring a 99.5% recovery rate for H2 and He. The low-pressure desorbed gas discharged from VPSA decarbonization system C is sent to the fuel pipeline network through pipeline 9. The decarbonized gas, after being treated by the VPSA decarbonization system C, enters the deoxidation system D. Through a catalytic deoxidation reaction, H2 and O2 react to produce H2O. The hydrogen required by the deoxidation system D can be supplied from the outside via pipe 3, or the hydrogen separated by the alloy dehydrogenation system I can be returned to the deoxidation system D for recycling via pipe 10. The deoxidation system D removes O2 from the decarbonized gas to ≤1ppm.

[0057] The deoxygenated and decarbonized purified gas enters the TSA fine purification system E, where CO2, H2S, H2O, and heavy hydrocarbons are further removed to obtain TSA finely purified gas, with CO2 and H2O reduced to ≤1ppm. The TSA finely purified gas then enters the first pressurization system F1 and is pressurized to 20.4 bar. After pressurization, it enters the first-stage membrane separation system G1 for further helium extraction. The non-permeable gas from the first-stage membrane separation system G1 enters the TSA fine purification system E through pipe 5, serving as the regeneration gas source for the adsorbent. The regenerated gas is returned to the fuel network through pipe 4. The permeable gas from the first-stage membrane separation system G1 enters the second pressurization system F2 and is pressurized to 21.9 bar. After pressurization, it enters the second-stage membrane separation system G2 for further helium enrichment. The non-permeable gas from the second-stage membrane separation system G2 enters the inlet of the first-stage membrane separation system G1 through pipe 6 to recover helium.

[0058] The permeate gas from the secondary membrane separation system G2 is pressurized to 16 bar in the third pressurization system F3. The pressurized permeate gas then enters the PSA purification system H, where multiple adsorbents in the PSA adsorption tower remove N2 to 1.5 ppm, O2 to 1 ppm, and CH4 to 0.4 ppm. The desorbed gas from the PSA purification system has a helium content of 31.25%. It is pressurized to 3.7 bar in the fourth pressurization system F4 and returned to the TSA fine desorption system E inlet for recovery via pipeline 7. The product gas from the PSA purification system enters the alloy dehydrogenation system I, where hydrogen is adsorbed by the alloy hydrogen-absorbing material, controlling the hydrogen content of the product helium to ≤1 ppm. 99.999% pure product helium is sent for external filling via pipeline 8. The hydrogen released during the regeneration of the alloy hydrogen-absorbing material is returned to the deoxygenation system D via pipeline 10 for further 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 sold 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, externally supplied hydrogen is connected to the deoxygenation system D through pipeline 3, and at the same time, the hydrogen discharged from the alloy dehydrogenation system I is supplied to the deoxygenation system D through pipeline.

[0059] The process parameters and material balances in Example 2 are shown in Tables 3 and 4, where Table 3 shows the process parameters and material content for the initial stage of the process, and Table 4 shows the process parameters and material content for the final stage of the process.

[0060] Table 3. Process parameters and material balance table for the front-end of the process in Example 2

[0061]

[0062] Table 4. Process parameters and material balance table for the later stage of the process in Example 2

[0063]

[0064] This utility model is compared with the prior art in the following aspects:

[0065] 1. Process Flow

[0066] Because natural gas contains very little helium, a processing capacity of tens of thousands of standard cubic meters per hour is required to achieve commercial value. Cryogenic purification is mainly used in the production of LNG from natural gas. However, for applications where natural gas is used as a chemical feedstock, CNG (natural gas for vehicles), power generation, and fuel, using cryogenic purification solely to remove helium would involve large investments, complex operations, and high energy consumption. Furthermore, the liquefied LNG would need to be regasified before use. Therefore, in scenarios where LNG is not produced from natural gas, cryogenic purification for direct helium removal is generally not employed.

[0067] This invention provides a process system for separating and purifying helium from helium-containing natural gas. This system includes 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+ Furthermore, the adsorbent in the VPSA decarbonization system can adsorb a portion of the methane, reducing the processing load on subsequent units and saving energy. Existing technologies involve combined processes, such as MDEA decarbonization, dry desulfurization, and TSA purification. These combined processes are less simple than the VPSA decarbonization system and involve higher investment. In particular, the TSA purification process is primarily used for deep removal of impurities; if the feed gas contains significant amounts of CO2 and H2S impurities, the TSA purification unit requires substantial investment and incurs high operating costs. Additionally, while maintaining a high helium recovery rate, the VPSA decarbonization system exhibits strong adaptability to the composition of natural gas.

[0068] Existing technologies do not include a deep dehydration and decarbonization system before the membrane separation system. Even if the preceding system removes CO2 and H2O to below 10 ppm, CO2 and H2O in the helium-rich gas continuously circulate and accumulate in the recycling system during subsequent membrane separation and PSA purification, ultimately causing the helium quality to fail to meet standards. This invention provides a process system for separating and purifying helium from helium-containing natural gas. This system includes a TSA fine removal system E downstream of the deoxygenation system D. The TSA fine removal system E deeply removes CO2, H2O, and H2S from the natural gas to less than 1 ppm, allowing for the recycling of helium for the downstream membrane separation and PSA purification systems, thus eliminating the impact of CO2, H2O, and H2S impurities accumulation.

[0069] This invention achieves efficient separation of H2 and He, and simultaneously obtains high-purity / electronic-grade He and electronic-grade H2. Compared with traditional chemical methods and other traditional processes, this invention achieves modularity, miniaturization (small footprint), low power consumption, and high efficiency.

[0070] This invention features rapid operation, simple operation, and the ability to obtain qualified product gas within a short time after startup; apart from the compressor, there are no moving parts, resulting in a low failure rate and high operational reliability; it flexibly obtains the maximum recovery rate through a multi-stage approach, achieving optimization and replacement of existing production processes; and the purity, flow rate, and pressure of the product gas exhibit high stability.

[0071] This invention features fewer unit stages, fewer interstage gas circulation cycles, lower energy consumption, and a simpler process. It can purify helium in helium-containing natural gas to 99%–99.999% according to the different purity requirements of the end user.

[0072] 2. Helium recovery rate

[0073] This invention proposes a process system for separating and purifying helium from helium-containing natural gas, achieving a helium recovery rate of over 86%.

[0074] 3. Investment in helium extraction equipment

[0075] Based on the investment situation of existing helium extraction equipment, the process system for separating and purifying helium from helium-containing natural gas proposed in this utility model can save about 35% of the investment compared with cryogenic helium extraction equipment.

[0076] 4. Dehydrogenation and oxygenation issues in the helium extraction unit

[0077] Depending on the conditions of the natural gas, if the natural gas contains hydrogen, the existing technology is to add O2 or air, and then react H2 and O2 to produce H2O through a catalytic deoxygenation reaction. Then, H2O and excess O2 are removed separately, thereby achieving the purpose of purifying H2 in He.

[0078] The catalytic oxidation method for removing H2 from He has the following problems:

[0079] 1) Because air needs to be actively introduced, other trace impurities in the air will be introduced, resulting in the final He concentration not meeting the standard.

[0080] 2) In the catalytic oxidation method, the amount of O2 is calculated based on the amount of H2. Fluctuations in upstream flow rate and content can cause fluctuations in the process, leading to technical and safety issues.

[0081] 3) The process is relatively complex. The O2 catalytic method requires additional equipment such as liquid oxygen storage tanks, deoxygenation towers, and drying and dehydration towers.

[0082] 4) Catalytic oxidation for dehydrogenation and oxygen removal requires a series of auxiliary devices and generates a large amount of solid waste. This not only involves huge investment (especially at low flow rates where economic efficiency is even worse), but also represents a significant waste of resources and energy. Furthermore, the installation of these auxiliary devices occupies a considerable amount of land.

[0083] This novel alloy dehydrogenation system I removes excess H2 after deoxidation using a special alloy material, eliminating the need for reaction. The entire separation process is conducted within the environment and temperature of circulating water, making it safer. The special alloy material separates H2 and He, suitable for any H2 / He ratio, and no other gases are introduced during the process. Even if the upstream gas composition changes or fluctuates, it will not affect the stability and safety of the process.

[0084] This invention uses special alloy materials to separate H2 and He, instead of catalytic combustion to remove H2 from He, achieving perfect separation. The byproduct, ultrapure H2, is both a highly efficient fuel and an important chemical raw material.

[0085] If the natural gas contains oxygen, the existing technology involves adding H2 and then reacting H2 and O2 to produce H2O through a catalytic deoxygenation reaction. Excess hydrogen is separated by a special alloy material, and the separated hydrogen is pressurized and returned to the deoxygenation system inlet to continue reacting with oxygen in the natural gas. Compared with the existing technology, this method has lower hydrogen consumption and higher helium recovery rate.

[0086] Compared to cryogenic technology, this invention reduces investment by approximately 35% for the same gas volume and helium content. Furthermore, it features a smaller footprint, simpler process, and lower energy consumption.

[0087] The membrane separation crude purification system has 1 to N stages (N is a natural number from 1 to 4).

[0088] The membrane material used in membrane separators is mainly polyimide (PI) fiber membrane.

[0089] The outer shell of the membrane separator is similar to that of a shell-and-tube heat exchanger, and it contains tens of thousands of tiny hollow fiber filaments.

[0090] The VPSA decarbonization system C process uses 4–12 adsorption towers, with 1–7 pressure equalization cycles, and adsorbent regeneration is performed under vacuum. The purpose of the VPSA decarbonization system C is to remove CO2, H2O, H2S, and C from natural gas in one step. 2+ Furthermore, the adsorbent in the VPSA decarbonization system can adsorb a portion of the methane, reducing the processing load on subsequent units and saving energy. Existing technologies involve combined processes, such as MDEA decarbonization, dry desulfurization, and TSA purification. These combined processes are less simple than the VPSA decarbonization system and involve higher investment. In particular, the TSA purification process is primarily used for deep removal of impurities; if the feed gas contains significant amounts of CO2 and H2S impurities, the TSA purification unit requires substantial investment and incurs high operating costs. Additionally, while maintaining a high helium recovery rate, the VPSA decarbonization system exhibits strong adaptability to the composition of natural gas.

[0091] The TSA purification system E process uses 2–4 adsorption towers with a regeneration temperature of 160–220°C. TSA purification system E removes H2O to 1 ppm, CO2 to 1 ppm, and H2S to 1 ppm. This deep removal of CO2, H2O, and H2S from natural gas allows for the recycling of helium for downstream membrane separation and PSA purification systems, eliminating the impact of CO2, H2O, and H2S impurity accumulation.

[0092] The PSA purification system uses 4 to 6 adsorption towers, with 1 to 3 pressure equalization cycles. Adsorbent regeneration is achieved through rinsing or vacuuming.

[0093] Alloy dehydrogenation system I removes hydrogen from helium to 1 ppm. The alloy hydrogen-absorbing material is mainly composed of titanium, manganese, zirconium, nickel, vanadium, and various rare earth / rare metals. Like a sponge absorbing water, the hydrogen-absorbing material reversibly absorbs and releases large amounts of H2. Once H2 comes into contact with the alloy hydrogen-absorbing material, it decomposes into H atoms on its surface. These H atoms then diffuse into the material's interior until they react with the material to form hydrides. At this point, H2 is stored in atomic form within the crystallization points of the alloy hydrogen-absorbing material (the interstitial positions between tetrahedrons and octahedrons). The alloy hydrogen-absorbing material is a material that achieves reversible H2 absorption and release, possessing significant advantages such as large H2 storage capacity, low storage pressure, small device size, and convenient use in confined spaces. When external pressure and temperature change, the hydrides decompose reversibly, releasing hydrogen gas with a purity of over 99.999%, and the hydrides then decompose again, returning to the material's intrinsic state.

[0094] The alloy is a substance highly sensitive to H2. At low temperatures (e.g., 10°C), a He / H2 mixture is introduced into the alloy. The alloy adsorbs H2 but not He, and the He is discharged through the exhaust port, achieving separation of H2 and He to obtain high-purity He. Simultaneously, at high temperatures (e.g., 200°C for stage 1, 350°C for stage 2), H2 is desorbed, yielding H2 with a purity exceeding 99.999%.

[0095] The alloy dehydrogenation system (D-regeneration) heats and cools the alloy adsorption column using heat transfer oil. It is equipped with a circulating heat exchanger and a circulating cooler, both using the same heat transfer oil medium. When the alloy adsorption column needs heating, a valve switches to allow high-temperature heat transfer oil (200-220°C) from the circulating heat exchanger to be introduced into the adsorption column jacket for heating. When the alloy adsorption column needs cooling, a valve switches to allow cold oil (0-10°C) from the circulating cooler to be introduced into the adsorption column jacket for rapid cooling. After regeneration, the alloy adsorption column switches back to hydrogen adsorption mode. This alternating switching enables continuous H2 adsorption and release production.

[0096] Compared to existing patented technologies that incorporate O2 or air catalytic dehydrogenation, which introduce other trace impurities from the air (CO2, Ar and rare gases), the device requires additional investment and land use for equipment such as liquid oxygen storage tanks, deoxygenation towers, and drying and dehydration towers. Furthermore, the catalytic dehydrogenation technology generates a large amount of solid waste through regular catalyst replacement, increasing operating costs.

[0097] Alloy Dehydrogenation System I uses a special alloy material to separate H2 and He, rather than removing H2 from He via catalysis. This system can recover the byproduct H2, which can be purified to high purity. Hydrogen is not only a highly efficient fuel and an important chemical raw material, but also a commonly used gas in the electronics industry.

[0098] In summary, domestic helium is mainly obtained from non-condensable gases and BOG gases produced during the natural gas liquefaction process. This invention provides a process system for directly separating and purifying helium from helium-containing natural gas, producing high-purity helium with a purity ≥99.999 vol%, and a helium recovery rate of over 95%.

[0099] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present utility model. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present utility model without departing from the scope of the present utility model shall still fall within the scope of the present utility model.

Claims

1. A process system for separating and purifying helium from a helium-containing natural gas, characterized by, The system comprises a pretreatment system (A), a membrane separation system (B), a VPSA decarburization system (C), a TSA fine removal system (E), a first pressurization system (F1), a first-stage membrane separation system (G1), a second pressurization system (F2), a second-stage membrane separation system (G2), a third pressurization system (F3), a PSA purification system (H) and an alloy dehydrogenation system (I) connected in sequence through pipelines, and a fourth pressurization system (F4) arranged between the PSA purification system (H) and the TSA fine removal system (E). The permeated gas discharged from the membrane separation system (B) is used to enter the VPSA decarburization system (C), and the non-permeated gas is used to be sent to a natural gas pipeline network; the low-pressure desorbed gas discharged from the VPSA decarburization system (C) is used to be sent to a fuel pipeline network; the TSA desorbed gas discharged from the TSA fine removal system (E) is used to be sent to the fuel pipeline network; the first-stage permeated gas discharged from the first-stage membrane separation system (G1) is used to enter the second pressurization system (F2), and the first-stage non-permeated gas is used to be returned to the TSA fine removal system (E); the second-stage permeated gas discharged from the second-stage membrane separation system (G2) is used to enter the third pressurization system (F3), and the second-stage non-permeated gas is used to be returned to the first-stage 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 pressurization system (F4) and then returned to the TSA fine removal system (E).

2. The process system for separating and purifying helium from the helium-containing natural gas according to claim 1, characterized in that, The system further comprises a deoxidation system D arranged between the VPSA decarburization system and the TSA fine removal system E, which is used to remove oxygen in the helium-containing natural gas.

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

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

5. The process system for separating and purifying helium from the helium-containing natural gas according to claim 1, characterized in that, The compressors used in the first pressurization system (F1), the second pressurization system (F2), the third pressurization system (F3) and the fourth pressurization system (F4) are reciprocating compressors or diaphragm compressors; the first pressurization system (F1) is used to pressurize the natural gas purified by the TSA fine removal system (E) to 1.0-2.2 MPa; the second pressurization system (F2) is used to pressurize the first-stage permeated gas at 20-100 kPa to 1.2-2.4 MPa; the third pressurization system (F3) is used to pressurize the second-stage permeated gas at 0.2-0.4 MPa to 1.6-1.8 MPa; and the fourth pressurization system (F4) is used to pressurize the PSA desorbed gas to 0.4-0.5 MPa.

6. The process system for separating and purifying helium from the helium-containing natural gas according to claim 1, wherein, The VPSA decarburization system C comprises a VPSA adsorption tower group and a VPSA pressure equalization pipeline system connected in sequence, the VPSA adsorption tower group comprises 4-12 VPSA adsorption towers arranged in parallel, and the VPSA pressure equalization pipeline system is arranged between the VPSA adsorption towers.

7. The process system for separating and purifying helium from the helium-containing natural gas according to claim 1, wherein, The PSA purification system H comprises a PSA equalizing pipeline system, and a pre-cooling heat exchanger, a PSA adsorption tower, a forward discharge gas buffer tank V and a pressure regulating valve arranged on the PSA equalizing pipeline system, the pre-cooling heat exchanger is used for cooling the gas entering the PSA purification system H; the PSA adsorption tower is used for removing impurities from the cooled gas; the forward discharge gas buffer tank V is used for temporarily storing the gas removed by the PSA adsorption tower and providing helium to flush the PSA adsorption tower.

8. The process system for separating and purifying helium from the helium-containing natural gas according to claim 2, wherein, The alloy dehydrogenation system I comprises an alloy dehydrogenation pipeline system, and an alloy adsorption column and a vacuum pump arranged on the alloy dehydrogenation pipeline system, the alloy adsorption column is used for adsorbing hydrogen in the gas; the vacuum pump is used for pumping out the hydrogen or recycling the hydrogen to the deoxidation system D for deoxidation.

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