Method for synchronously purifying helium-poor and ultra-lean natural gas and extracting high-value substances

Abstract

The invention discloses a method for synchronously purifying helium-poor and ultra-lean natural gas and extracting high-value substances, and belongs to the field of membrane separation. The method comprises the following steps: helium-poor and ultra-poor helium natural gas passes through a helium extraction membrane block to complete helium extraction, and then retentate gas enters a nitrogen removal membrane block to perform nitrogen removal; a helium extraction membrane is used in the helium extraction membrane block, helium is preferentially permeated into the helium extraction membrane, and the He / CH4 selectivity is at least 40; a nitrogen removal membrane is used in the nitrogen removal membrane block, nitrogen is preferentially permeated into the nitrogen removal membrane, and the N2 / CH4 selectivity is at least 4. According to the method disclosed by the invention, the helium concentration in the natural gas can be increased from 0.01-0.1% to not less than 1%, the nitrogen content is reduced to not more than 4%, and the recovery rates of helium and methane are not less than 90%.

Description

Technical Field

[0001] This application relates to a method for simultaneous purification and extraction of high-value substances from helium-poor and ultra-helium-poor natural gas, belonging to the field of membrane separation. Background Technology

[0002] For industrial helium extraction, helium mainly comes from helium-containing natural gas. Conventional helium extraction technologies rely on multi-stage cryogenic condensation and pressure swing adsorption, which are lengthy processes with huge investments, posing challenges to economic efficiency.

[0003] Meanwhile, as an important clean energy source, the efficient purification and component extraction of natural gas are crucial for resource utilization. With the development of unconventional natural gas (such as shale gas and coalbed methane), the nitrogen (N2) content in the feed gas has generally increased (Journal of Chemical Industry and Engineering, 2010, 61(S2):54-57). High N2 content leads to a decrease in calorific value and affects pipeline transportation standards (US 2019 / 0321780 A1 specifies that the N2 content must be less than 4%).

[0004] Traditional denitrification technologies, such as cryogenic distillation, are energy-intensive and require complex equipment, while adsorption methods suffer from capacity limitations and regeneration challenges. There is an urgent need to develop efficient and low-cost denitrification processes.

[0005] Membrane separation technology has shown great potential in the field of gas separation due to its advantages such as low energy consumption, modularity, and no phase change. In existing technologies, polymer membranes have been used for CO2 / CH4 separation, but for the CH4-N2 system, the kinetic diameters of the two are similar (CH4: 0.38 nm; N2: 0.364 nm), and the selectivity of traditional membrane materials is insufficient. Rubber-state materials, such as Pebax, have a CH4 / N2 selectivity of around 3, preferentially permeating methane. For natural gas, methane is the main component, and permeating a large amount of this main component through the membrane requires a larger membrane area and higher energy consumption. Glassy polymers such as polyimide typically have an N2 / CH4 selectivity of around 2, which cannot achieve effective separation. Summary of the Invention

[0006] Based on the above background technology, the present invention provides a method for simultaneous purification and extraction of high-value substances from lean helium and ultra-lean helium natural gas. The method includes a high-value substance extraction block (i.e., a helium extraction membrane block) and a purification block (i.e., a nitrogen removal membrane block). Each block can adopt a multi-stage, multi-segment membrane process, and the blocks are connected and coupled to each other or within the blocks through permeate gas, residual permeate gas, or their reflux phase.

[0007] In particular, this invention proposes a membrane process for simultaneous helium extraction and nitrogen removal from helium-poor and ultra-helium-poor natural gas. Through the separation membrane and process of this invention, nitrogen removal and helium extraction from natural gas can be achieved simultaneously. Compared with traditional processes that first remove nitrogen (such as cryogenic distillation) and then extract helium (such as pressure swing adsorption), the process is simpler, requires less equipment investment, and reduces energy consumption.

[0008] The membrane process for simultaneous nitrogen removal and helium extraction of natural gas proposed in this invention prioritizes helium extraction, followed by nitrogen removal. Natural gas passes through the helium extraction membrane block, while residual gas enters the nitrogen removal block.

[0009] This application provides a method for simultaneous purification and extraction of high-value components from lean and ultra-lean helium natural gas. The method includes the following steps: 1) comprising a high-value resource extraction block and a purification block; 2) each block is implemented using membrane technology; 3) each block can employ a multi-stage, multi-section process; 4) the blocks are connected and coupled to each other or within each block via permeate gas, residual permeate gas, or their reflux phase; the high-value resource extraction is helium extraction, and the purification is nitrogen removal; helium extraction is performed first, followed by nitrogen removal.

[0010] A method for simultaneous purification and extraction of high-value components from helium-poor and ultra-helium-poor natural gas, the method comprising: The helium-poor and ultra-helium-poor natural gas is first extracted through the helium extraction membrane block, and then the residual gas enters the nitrogen removal membrane block for nitrogen removal. The helium extraction membrane block uses a helium extraction membrane, which preferentially permeates with helium, and the He / CH4 selectivity is at least 40. The nitrogen removal membrane block uses nitrogen removal membrane, which preferentially permeates nitrogen, with an N2 / CH4 selectivity of at least 4.

[0011] Preferably, the He / CH4 selectivity of the helium extraction membrane is at least 100; The nitrogen removal membrane has an N2 / CH4 selectivity of at least 6.

[0012] Preferably, the He / CH4 selectivity of the helium extraction membrane is at least 150.

[0013] Optionally, the He / CH4 selectivity of the helium extraction membrane is 40~400.

[0014] Optionally, the N2 / CH4 selectivity of the nitrogen removal membrane is 4~20.

[0015] Preferably, the N2 / CH4 selectivity of the nitrogen removal membrane is 4~10.

[0016] Optionally, the He / CH4 selectivity of the helium extraction membrane is any value among 40, 50, 60, 80, 100, 120, 150, 160, 180, 200, 250, 300, 350, and 400, or a range between any two.

[0017] Optionally, the N2 / CH4 selectivity of the nitrogen removal membrane is any value from 4, 5, 6, 8, 10, 12, 14, 15, 16, 18, 20 or a range between any two.

[0018] Optionally, the helium extraction membrane is at least one of cellulose acetate membrane, polybenzimidazole membrane, polyimide membrane, polyetherimide membrane, polymethyl methacrylate membrane, and perfluorinated copolymer membrane. Polyimide or perfluorinated copolymer is preferred.

[0019] Optionally, the nitrogen removal membrane is at least one of the following: polytetrafluoroethylene membrane, (1,2,2-trifluorovinyl)1,1,2,2,3,4,4-heptafluoro-3-butene ether cyclized polymer membrane, and perfluorinated copolymer membrane. A perfluorinated copolymer membrane is preferred.

[0020] Optionally, the operating temperature of the method is -50 to 150°C; the operating pressure is 10 to 150 bar.

[0021] Optionally, the operating temperature is any value or a range between any two of -50℃, -30℃, -20℃, -10℃, 0℃, 10℃, 20℃, 30℃, 50℃, 60℃, 80℃, 90℃, 100℃, 120℃, 130℃, and 150℃.

[0022] Optionally, the operating pressure is any value among 10 bar, 20 bar, 50 bar, 60 bar, 80 bar, 10 bar, 120 bar, 130 bar, and 150 bar, or a range between any two.

[0023] The method provided by this invention can be adjusted within the wide range described above.

[0024] Optionally, the helium extraction membrane block and / or nitrogen removal membrane block adopt a multi-stage and multi-segment process, and the blocks are connected and coupled to each other or within each block through permeate gas, residual permeate gas or their reflux phase.

[0025] Optionally, the helium extraction membrane block includes one helium extraction membrane separation unit, and the nitrogen removal membrane block includes two nitrogen removal membrane separation units; the process flow includes the following: The raw material gas I enters the helium extraction membrane separation unit to obtain permeate gas I and residual gas I, wherein the permeate gas I is a helium-rich gas; The residual gas I enters the nitrogen removal membrane separation unit I to obtain permeate gas II and residual gas II, wherein the residual gas II is purified gas; The permeate gas II is compressed and then enters the nitrogen removal membrane separation unit II to obtain permeate gas III and residual gas III. The permeate gas III is a high-nitrogen tail gas. The residual gas III is mixed with the raw material gas I and then returned to the helium extraction membrane separation unit, or the residual gas III is mixed with the residual gas I and then returned to the nitrogen removal membrane separation unit I.

[0026] Optionally, the helium extraction membrane block includes one helium extraction membrane separation unit, and the nitrogen removal membrane block includes three nitrogen removal membrane separation units; including process flow a, process flow b, or process flow c; Process flow a: Raw material gas I enters the helium extraction membrane separation unit to obtain permeate gas I and residual gas I, wherein permeate gas I is a helium-rich gas; The residual gas I enters the nitrogen removal membrane separation unit I to obtain permeate gas II and residual gas II, wherein the residual gas II is purified gas; The permeate gas II is compressed and then enters the nitrogen demembrane separation unit II to obtain permeate gas III and residual gas III. The residual gas III is mixed with the residual gas I and then returned to the nitrogen demembrane separation unit I. The permeate gas III is compressed and then enters the nitrogen removal membrane separation unit III to obtain permeate gas IV and residual gas IV. The permeate gas IV is a high-nitrogen tail gas. The residual gas IV and residual gas I are mixed and then returned to the nitrogen removal membrane separation unit I. Process flow b: Raw material gas I enters the helium extraction membrane separation unit to obtain permeate gas I and residual gas I, wherein permeate gas I is a helium-rich gas; The residual gas I enters the nitrogen removal membrane separation unit I to obtain permeate gas II and residual gas II; The permeate gas II is compressed and then enters the nitrogen removal membrane separation unit II to obtain permeate gas III and residual gas III. The permeate gas III is a high-nitrogen tail gas. The residual gas III and residual gas I are mixed and then returned to nitrogen removal membrane separation unit I; The residual gas II enters the nitrogen removal membrane separation unit III to obtain permeate gas IV and residual gas IV, wherein the residual gas IV is purified gas. The permeate gas IV is compressed, mixed with residual permeate gas I, and then returned to the nitrogen removal membrane separation unit I. Option c: The raw material gas I enters the helium extraction membrane separation unit to obtain permeate gas I and residual gas I, wherein the permeate gas I is a helium-rich gas; The residual gas I enters the nitrogen removal membrane separation unit I to obtain permeate gas II and residual gas II; The permeate gas II is compressed and then enters the nitrogen removal membrane separation unit II to obtain permeate gas III and residual gas III. The permeate gas III is a high-nitrogen tail gas. After being mixed with residual gas II, the residual gas III enters nitrogen removal membrane separation unit III to obtain permeate gas IV and residual gas IV, wherein the residual gas IV is purified gas. The permeate gas IV is compressed, mixed with residual permeate gas I, and then returned to the nitrogen removal membrane separation unit I.

[0027] Optionally, the helium extraction membrane block includes two helium extraction membrane separation units, and the nitrogen removal membrane block includes two nitrogen removal membrane separation units; the process flow includes the following: The raw material gas I enters the helium extraction membrane separation unit I to obtain permeate gas I and residual gas I, wherein the permeate gas I is a helium-rich gas. The residual gas I enters the helium extraction membrane separation unit II to obtain permeate gas II and residual gas II; The permeate gas II is compressed, mixed with the raw material gas I, and then returned to the helium extraction membrane separation unit I. The residual gas II enters the nitrogen removal membrane separation unit I to obtain permeate gas III and residual gas III, wherein the residual gas III is purified gas; The permeate gas III is compressed and then enters the nitrogen removal membrane separation unit II to obtain permeate gas IV and residual gas IV. The permeate gas IV is a high-nitrogen tail gas. The residual gas IV and residual gas II are mixed and then returned to the nitrogen removal membrane separation unit I.

[0028] Optionally, the helium extraction membrane block includes three helium extraction membrane separation units, and the nitrogen removal membrane block includes two nitrogen removal membrane separation units; the process flow includes the following: The feed gas I enters the helium extraction membrane separation unit I to obtain permeate gas I and residual gas I; The permeate gas I is compressed and then enters the helium extraction membrane separation unit II to obtain permeate gas II and residual gas II. The permeate gas II is a helium-rich gas. The residual gas I enters the helium extraction membrane separation unit III to obtain permeate gas III and residual gas III; The permeate gas III is compressed, mixed with the raw material gas I, and then returned to the helium extraction membrane separation unit I. After the residual gas II and residual gas III are mixed, they enter the nitrogen removal membrane separation unit I to obtain permeate gas IV and residual gas IV, wherein the residual gas IV is the purified gas. The permeate gas IV is compressed and then enters the nitrogen removal membrane separation unit II to obtain permeate gas V and residual gas V, wherein the permeate gas V is a high-nitrogen tail gas. The residual gas V is mixed with residual gas II and residual gas III and then returned to the nitrogen removal membrane separation unit I.

[0029] The method for simultaneous helium extraction and nitrogen removal from natural gas proposed in this invention can be used for helium extraction and nitrogen removal from natural gas in helium-poor and ultra-helium-poor conditions. It can increase the helium concentration in natural gas from 0.01%-0.1% to no less than 1%, reduce the nitrogen content to no more than 4%, and achieve a helium and methane recovery rate of no less than 90%.

[0030] The beneficial effects that this application can produce include: (1) Through the separation membrane and process of the present invention, the lower limit of industrial grade helium concentration can be reduced to 0.01%-0.1%, which can cover most of my country's helium resources.

[0031] (2) The separation membrane and process of the present invention can simultaneously achieve denitrification and helium extraction of natural gas. Compared with the traditional process of first denitrification (such as low temperature distillation) and then helium extraction (such as pressure swing adsorption), the process is simple, the equipment investment is small, and the energy consumption is greatly reduced.

[0032] (3) The separation membrane and process of the present invention can be operated in a wide range, with a wide range of applications and strong application flexibility, and can be applied to a variety of scenarios.

[0033] (4) The process of the present invention has moderate requirements for membrane performance, which can greatly promote the promotion and application of domestically produced membranes. (5) The separation membrane and process of the present invention can achieve efficient helium enrichment and nitrogen removal under mild temperature and pressure. Attached Figure Description

[0034] Figure 1 The process flow is as described in Example 1; Figure 2 The process flow is as described in Examples 2-9; Figure 3 The process flow is as described in Examples 10-11; Figure 4 The process flow is as described in Example 12; Figure 5 The process flow is as described in Example 13; Figure 6 The process flow is as described in Examples 14-19; Figure 7 The process flow is as described in Examples 20-24; In the attached diagram, area A is the helium extraction block, and area B is the nitrogen removal block. Detailed Implementation

[0035] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0036] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0037] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0038] As a preferred embodiment, the structural formula of the perfluorinated copolymer is: ; in x, y All can be 0, but they cannot all be 0 at the same time. x =0~800, y =0~800.

[0039] The monomers A and B of the perfluorinated copolymer are selected from one of the following structural formulas: , , , , , , , , , ,

[0040] Among them, X and Y are independently selected from F, Cl, Br, I, SO2F; the values ​​of m, n, k, t, d, q, u, and w are integers from 0 to 6.

[0041] As a preferred embodiment, the method for preparing the perfluorinated copolymer membrane includes: (1) The perfluorinated copolymer is dissolved in a fluorinated mixed solvent and dispersed uniformly by ultrasonication to obtain a homogeneous coating liquid, wherein the concentration of the fluorinated polymer is 0.5~10wt%, preferably 0.8~2.0wt%; (2) The above coating liquid is coated on the support base film, dried, and then subjected to plasma treatment to obtain a perfluorinated copolymer film.

[0042] Optionally, the supporting base film is at least one of polysulfone, polyethersulfone, polyimide, polyamide-imide, polyetherimide, polyacrylonitrile, polyvinylidene fluoride, and polyetheretherketone.

[0043] Optionally, the fluorinated mixed solvent is composed of a high-boiling-point fluorinated solvent with a boiling point of 100~250℃ and a low-boiling-point fluorinated solvent with a boiling point below 100℃. The fluorinated solvent is any one of perfluoropolyether, hydrofluoroalkane, hydrofluoroolefin, perfluoroalkane, perfluoroolefin, perfluorobenzene, and perfluoroalcohol, with a mass ratio of 1:9~19.

[0044] Optionally, the gas used for plasma treatment is either CF4 or SF6. The radio frequency of the power supply is one of 40 kHz, 13.56 MHz, or 2.54 GHz, preferably 13.56 MHz; the processing time is 5 to 100 seconds, preferably 15 to 30 seconds.

[0045] The calculation methods for helium recovery rate and methane recovery rate in the embodiments of this application are as follows:

[0046] Example 1 Adopting attachment Figure 1 The process flow is shown below. The feed gas 101 composition is: 15.4% N2, 84.52% CH4, and 0.08% He. The feed gas pressure is 30 bar, and the temperature is 50°C. Membrane separation unit M101 is a polyimide helium extraction membrane with a He / CH4 selectivity of 154 and an N2 / CH4 selectivity of 1.5. M102 and M103 are both perfluorinated nitrogen removal membranes with an N2 / CH4 selectivity of 5 and a He / CH4 selectivity of 200.

[0047] The perfluorinated copolymer was dissolved in a mixed solvent of 9g Solvay Galden® SV135 (boiling point 135℃) and 90g Solvay Galden® SV55 (boiling point 55℃), and the solution was ultrasonically dispersed to obtain a 1wt% coating solution. This coating solution was then applied to a polyetheretherketone (PEEK) substrate film. After drying, plasma treatment was performed for 30s using SF6 as the medium and a 13.56kHz radio frequency power supply to obtain a perfluorinated nitrogen-removed membrane. The monomers of the perfluorinated copolymer were: and ; Raw material gas 101 enters helium extraction block M101, with a permeation side of 0.1 bar. The permeate gas is helium-rich gas 103, and the residual permeate gas 104 enters the denitrification block.

[0048] After passing through the helium extraction block, more than 90% of the helium has been extracted, and the helium content in the stream entering the nitrogen removal block is negligible. At this point, the helium separation performance of the membrane separation unit in the nitrogen removal block is no longer important.

[0049] Both M102 and M103 are at atmospheric pressure on their permeation sides. The permeate gas 105 generated by M102 is purified gas. The permeate gas 106 is compressed and then enters M103. The permeate gas 109 generated by separation is mixed with the raw material gas 101 to form 102, which is returned to M101. The permeate gas 108 is high-nitrogen tail gas.

[0050] Using this process, the helium concentration of helium-rich gas 103 is 1.56%, the nitrogen content of purified gas 105 is less than 4%, the helium recovery rate is 93.51%, the methane recovery rate is 90.17%, and the logistics table is shown in Table 1.

[0051] Table 1

[0052] Example 2 Adopting attachment Figure 2 The process flow is shown below. Feed gas 201 has the following composition: 15.4% N2, 84.5% CH4, and 0.1% He. Feed gas pressure is 30 bar, and temperature is 50°C. Membrane separation unit M201 is a polyimide helium extraction membrane with a He / CH4 selectivity of 154 and an N2 / CH4 selectivity of 1.5. M202 and M203 are both perfluorinated nitrogen removal membranes with an N2 / CH4 selectivity of 6 and a He / CH4 selectivity of 200. All membrane separation units operate at atmospheric pressure on the permeate side.

[0053] The perfluorinated copolymer was dissolved in 6.2 g of 3M Fluorinert FC40 (boiling point 165°C) and 92.8 g of 3M Novec (boiling point 61°C). TM A 1 wt% coating solution was obtained by ultrasonically dispersing the mixture in a 7100 mixed solvent. This coating solution was then coated onto a polysulfone-supported substrate film. After drying, plasma treatment was performed for 20 seconds using CF4 as the medium and a 13.56 kHz power supply to obtain a perfluorinated nitrogen-removed membrane. The monomers of the perfluorinated copolymer were: and ; Raw material gas 201 enters M201 in the helium extraction block, permeate gas is helium-rich gas 202, and residual permeate gas 203 enters the denitrification block. 203 mixes with residual permeate gas 209 from M203 to form 204, which enters M202. Residual permeate gas 205 is purified gas. Permeate gas 206 is compressed and its pressure is increased to 30 bar. 207 is returned to M202 via residual permeate gas 209 generated from M203. Permeate gas 208 is high-nitrogen tail gas.

[0054] Using this process, the helium concentration of helium-rich gas 202 is 1.01%, the nitrogen content of purified gas 205 is less than 4%, the helium recovery rate is 90.15%, the methane recovery rate is 90.15%, and the logistics table is shown in Table 2.

[0055] Table 2

[0056] Example 3 Adopting attachment Figure 2The process is shown below. The composition, temperature, and pressure of the feed gas 201 are the same as in Example 1. The membrane separation unit M201 is a polyimide helium extraction membrane with a He / CH4 selectivity of 154 and an N2 / CH4 selectivity of 1.5. M202 and M203 are both perfluorinated nitrogen removal membranes (same as in Example 2) with an N2 / CH4 selectivity of 6 and a He / CH4 selectivity of 200. The permeate side of M201 is 0.1 bar, while the permeate sides of M202 and M203 are at atmospheric pressure.

[0057] Raw material gas 201 enters M201 in the helium extraction block, permeate gas is helium-rich gas 202, and residual permeate gas 203 enters the denitrification block. 203 mixes with residual permeate gas 209 from M203 to form 204, which enters M202. Residual permeate gas 205 is purified gas. Permeate gas 206 is compressed and its pressure is increased to 30 bar. 207 is returned to M202 via residual permeate gas 209 generated from M203. Permeate gas 208 is high-nitrogen tail gas.

[0058] Using this process, the helium concentration in helium-rich gas 202 is 2.82%, the nitrogen content in purified gas 205 is less than 4%, the helium recovery rate is 91.82%, the methane recovery rate is 90.12%, and the logistics table is shown in Table 3.

[0059] Table 3

[0060] Example 4 Adopting attachment Figure 2 The process is shown below. The composition and temperature of the feed gas 201 are the same as in Example 3, and the pressure is 50 bar. The membrane separation units are the same as in Example 2. M201 is a polyimide helium extraction membrane with a He / CH4 selectivity of 154 and an N2 / CH4 selectivity of 1.5. M202 and M203 are perfluorinated nitrogen removal membranes (same as in Example 2), with an N2 / CH4 selectivity of 6 and a He / CH4 selectivity of 200. The permeate side of all membrane separation units is at atmospheric pressure.

[0061] Raw material gas 201 enters M201 in the helium extraction block. The permeate gas is helium-rich gas 202. The residual gas 203 mixes with the residual gas 209 of M203 to form 204, which enters M202 in the denitrification block. The resulting residual gas 205 is purified gas. The permeate gas 206 is compressed and its pressure is increased to 50 bar. The residual gas 209 generated by M203 is returned to M202. The permeate gas 208 is high-nitrogen tail gas.

[0062] Using this process, the helium concentration in helium-rich gas 202 is 1.12%, the nitrogen content in purified gas 205 is less than 4%, the helium recovery rate is 93.43%, the methane recovery rate is 91.68%, and the logistics table is shown in Table 4.

[0063] Table 4

[0064] Example 5 Adopting attachment Figure 2 The process is shown below. The composition, temperature, and pressure of the feed gas 201 are the same as in Example 4. The membrane separation unit is the same as in Example 2. M201 is a polyimide helium extraction membrane with a He / CH4 selectivity of 154 and an N2 / CH4 selectivity of 1.5. M202 and M203 are perfluorinated nitrogen removal membranes (same as in Example 2) with an N2 / CH4 selectivity of 6 and a He / CH4 selectivity of 200. The permeate side of M201 is at atmospheric pressure, and the permeate side of M202 and M203 is at 0.1 bar.

[0065] Raw material gas 201 enters M201 in the helium extraction block. The permeate gas is helium-rich gas 202. The residual gas 203 mixes with the residual gas 209 of M203 to form 204, which enters M202 in the denitrification block. The resulting residual gas 205 is purified gas. The permeate gas 206 is compressed and its pressure is increased to 50 bar. The residual gas 209 generated by M203 is returned to M202. The permeate gas 208 is high-nitrogen tail gas.

[0066] Using this process, the helium concentration in helium-rich gas 202 is 1.12%, the nitrogen content in purified gas 205 is less than 4%, the helium recovery rate is 93.43%, the methane recovery rate is 92.21%, and the logistics table is shown in Table 5.

[0067] Table 5

[0068] Example 6 Adopting attachment Figure 2 The process is shown below. The composition and temperature of the feed gas 201 are the same as in Example 3, and the pressure is 100 bar. The membrane separation units are the same as in Example 2. M201 is a polyimide helium extraction membrane with a He / CH4 selectivity of 154 and an N2 / CH4 selectivity of 1.5. M202 and M203 are perfluorinated nitrogen removal membranes (same as in Example 2), with an N2 / CH4 selectivity of 6 and a He / CH4 selectivity of 200. The permeate side of all membrane separation units is at atmospheric pressure.

[0069] Raw material gas 201 enters M201 in the helium extraction block. The permeate gas is helium-rich gas 202. The residual gas 203 mixes with the residual gas 209 of M203 to form 204, which enters M202 in the denitrification block. The resulting residual gas 205 is purified gas. The permeate gas 206 is compressed and its pressure is increased to 100 bar. The residual gas 209 generated by M203 is returned to M202. The permeate gas 208 is high-nitrogen tail gas.

[0070] Using this process, the helium concentration in helium-rich gas 202 is 1.62%, the nitrogen content in purified gas 205 is less than 4%, the helium recovery rate is 93.83%, the methane recovery rate is 91.60%, and the logistics table is shown in Table 6.

[0071] Table 6

[0072] Example 7 Adopting attachment Figure 2 The process flow is shown. The composition and pressure of the feed gas 201 are the same as in Example 4, and the temperature is -50°C. Separation unit M201 is a polyimide helium extraction membrane (same as in Example 2, performance changes are caused by temperature variations), with a He / CH4 selectivity of 190 and an N2 / CH4 selectivity of 1.9. M202 and M203 are perfluorinated nitrogen removal membranes (same as in Example 2, performance changes are caused by temperature variations), with an N2 / CH4 selectivity of 7.5 and a He / CH4 selectivity of 225. The permeate side is at atmospheric pressure.

[0073] Raw material gas 201 enters M201 in the helium extraction block. The permeate gas is helium-rich gas 202. The residual permeate gas 203 mixes with the residual permeate gas 209 from the nitrogen-removed membrane M203 to form 204, which enters M202 in the denitrification block. The resulting residual permeate gas 205 is purified gas. The permeate gas 206 is pressurized to 50 bar and cooled to 50°C after passing through a compressor with a cooling system. The residual permeate gas 209 generated by M203 is returned to M202. The permeate gas 208 is high-nitrogen tail gas.

[0074] Using this process, the helium concentration in helium-rich gas 202 is 1.15%, the nitrogen content in purified gas 205 is less than 4%, the helium recovery rate is 92.30%, the methane recovery rate is 92.13%, and the logistics table is shown in Table 7.

[0075] Table 7

[0076] Example 8 Adopting attachment Figure 2 The process is shown below. The composition, temperature, and pressure of the feed gas 201 are the same as in Example 3. Membrane separation unit 201 is a polyimide helium extraction membrane with a He / CH4 selectivity of 40 and an N2 / CH4 selectivity of 1.5. M202 and M203 are both perfluorinated nitrogen removal membranes with an N2 / CH4 selectivity of 6 (same as in Example 2) and a He / CH4 selectivity of 200. The permeate side of M201 is at 0.1 bar, while the permeate sides of M202 and M203 are at atmospheric pressure.

[0077] Raw material gas 201 enters M201 in the helium extraction block. The permeate gas is helium-rich gas 202. The residual permeate gas 203 mixes with the residual permeate gas 209 from the nitrogen-removed membrane M203 to form 204, which enters M202 in the denitrification block. The resulting residual permeate gas 205 is purified gas. After the temperature and pressure of the permeate gas 206 are regulated by a compressor with a cooling system, it enters M203 207. The resulting residual permeate gas 209 is returned to M202. The permeate gas 208 is high-nitrogen tail gas.

[0078] Using this process, the helium concentration of helium-rich gas 202 is 1.04%, the nitrogen content of purified gas 205 is less than 4%, the helium recovery rate is 90.61%, the methane recovery rate is 90.57%, and the logistics table is shown in Table 8.

[0079] Table 8

[0080] Example 9 Adopting attachment Figure 2 The process flow is shown. The composition, temperature, and pressure of the feed gas 201 are the same as in Example 3. Membrane separation units M201, M202, and M203 are all perfluorinated membranes (same as in Example 2), with a He / CH4 selectivity of 200 and an N2 / CH4 selectivity of 6. The permeate side of M201 is 0.1 bar, while the permeate sides of M202 and M203 are at atmospheric pressure.

[0081] Raw material gas 201 enters M201 in the helium extraction block. The permeate gas is helium-rich gas 202. The residual permeate gas 203 mixes with the residual permeate gas 209 from the nitrogen-removed membrane M203 to form 204, which enters M202 in the denitrification block. The resulting residual permeate gas 205 is purified gas. The permeate gas 206 is pressurized to 30 bar and cooled to 50°C after passing through a compressor with a cooling system. The residual permeate gas 209 generated by M203 is returned to M202. The permeate gas 208 is high-nitrogen tail gas.

[0082] Using this process, the helium concentration in helium-rich gas 202 is 1.81%, the nitrogen content in purified gas 205 is less than 4%, the helium recovery rate is 97.39%, the methane recovery rate is 90.61%, and the logistics table is shown in Table 9.

[0083] Table 9

[0084] Example 10 Adopting attachment Figure 3 The process is shown. The composition, temperature, and pressure of the feed gas 301 are the same as in Example 4. Membrane separation units M301, M302, M303, and M304 are all perfluorinated membranes (same as in Example 2), with a He / CH4 selectivity of 200 and an N2 / CH4 selectivity of 6. The permeate side is at atmospheric pressure.

[0085] The raw material gas enters M301 in the helium extraction block. The permeate gas is helium-rich gas 302. The residual permeate gas 303 mixes with the residual permeate gas from nitrogen removal membranes M303 and M304 to form 304, which enters M302 in the denitrification block, producing residual permeate gas 305, which is purified gas. The permeate gas 306 is pressurized to 30 bar and cooled to 50°C after passing through a compressor with a cooling system. The residual permeate gas 309 produced by M303 is returned to M302. The permeate gas 308 is also regulated to 50 bar and 50°C by a compressor with a cooling system. The residual permeate gas 312 produced by M304 is returned to M302. The permeate gas 311 is high-nitrogen tail gas.

[0086] Using this process, the helium concentration of helium-rich gas 302 is 1.08%, the nitrogen content of purified gas 305 is less than 4%, the helium recovery rate is 91.74%, the methane recovery rate is 90.93%, and the logistics table is shown in Table 10.

[0087] Table 10

[0088] Example 11 Adopting attachment Figure 3 The process is shown below. The composition and temperature of the feed gas 301 are the same as in Example 10, and the pressure is 10 bar. The membrane separation unit M301 is a polyimide helium extraction membrane with a He / CH4 selectivity of 154, an N2 / CH4 selectivity of 1.5, and a permeate side pressure of 0.1 bar. M302, M303, and M304 are all perfluorinated membranes (same as in Example 2), with an N2 / CH4 selectivity of 6, a He / CH4 selectivity of 200, and a permeate side pressure of atmospheric pressure.

[0089] The raw material gas enters M301 in the helium extraction block. The permeate gas is helium-rich gas 302. The residual permeate gas 303 mixes with the residual permeate gas from nitrogen removal membranes M303 and M304 to form 304, which enters M302 in the denitrification block, producing residual permeate gas 305, which is purified gas. The permeate gas 306 is regulated to 10 bar and 50°C by a compressor with a cooling system. The residual permeate gas 309 produced by M303 is returned to M302. The permeate gas 308 is also regulated to 10 bar and 50°C by a compressor with a cooling system. The residual permeate gas 312 produced by M304 is returned to M302. The permeate gas 311 is high-nitrogen tail gas.

[0090] Using this process, the helium concentration of helium-rich gas 302 is 2.01%, the nitrogen content of purified gas 305 is less than 4%, the helium recovery rate is 93.88%, the methane recovery rate is 91.46%, and the logistics table is shown in Table 11.

[0091] Table 11

[0092] Example 12 Adopting attachment Figure 4 The process flow is shown. The composition, temperature, and pressure of the feed gas 401 are the same as in Example 3. Membrane separation unit M401 is a polyimide helium extraction membrane with a He / CH4 selectivity of 154 and an N2 / CH4 selectivity of 1.5. M402, M403, and M404 are all perfluorinated nitrogen removal membranes (same as in Example 2), with an N2 / CH4 selectivity of 6 and a He / CH4 selectivity of 200. The permeate side of M401 is at 0.1 bar, while the permeate sides of M402, M403, and M404 are at atmospheric pressure.

[0093] The raw material gas enters M401 in the helium extraction block. The permeate gas is helium-rich gas 402. The residual permeate gas 403 mixes with the permeate gas from nitrogen-removed membrane M403 and the residual permeate gas from M404 to form 404, which enters M402 in the denitrification block. The residual permeate gas 405 enters M403 for further denitrification. The residual permeate gas 406 is purified gas. The permeate gas 407 is regulated by a compressor with a cooling system and then returned to M402. The permeate gas 409 is also regulated by a compressor with a cooling system to 30 bar and 50°C. The regulated 410 is the residual permeate gas 412 generated by M404 and returned to M402. The permeate gas 411 is high-nitrogen tail gas.

[0094] Using this process, the helium concentration of helium-rich gas 402 is 2.82%, the nitrogen content of purified gas 406 is less than 4%, the helium recovery rate is 91.82%, the methane recovery rate is 92.92%, and the logistics table is shown in Table 12.

[0095] Table 12

[0096] Example 13 Adopting attachment Figure 5 The process flow is shown. The composition, temperature, and pressure of the feed gas 501 are the same as in Example 3. Membrane separation unit M501 is a polyimide helium extraction membrane with a He / CH4 selectivity of 154 and an N2 / CH4 selectivity of 1.5. M502, M503, and M504 are all perfluorinated nitrogen removal membranes (same as in Example 2), with an N2 / CH4 selectivity of 6 and a He / CH4 selectivity of 200. The permeate side of M501 is at 0.1 bar, while the permeate sides of M502, M503, and M504 are at atmospheric pressure.

[0097] The raw material gas enters M501 in the helium extraction block. The permeate gas is helium-rich gas 502. The residual permeate gas 503 mixes with the permeate gas from the nitrogen-removed membrane M503 to form 504, which enters M502 in the denitrification block. The permeate gas 510 from M502 enters M504 after its temperature and pressure are regulated by a compressor equipped with a cooling system. The permeate gas 513 is high-nitrogen tail gas. The residual permeate gas 512 mixes with the residual permeate gas 505 from M502 to form 506, which enters M503. The permeate gas 508 is mixed with 503 after its temperature and pressure are regulated by a compressor equipped with a cooling system and returned to M502. The residual permeate gas 507 is purified gas.

[0098] Using this process, the helium concentration of helium-rich gas 502 is 2.82%, the nitrogen content of purified gas 406 is less than 4%, the helium recovery rate is 91.82%, the methane recovery rate is 90.58%, and the logistics table is shown in Table 13.

[0099] Table 13

[0100] Example 14 Adopting attachment Figure 6 The process is shown below. The composition, temperature, and pressure of the feed gas 601 are the same as in Example 3. Membrane separation units M601 and M602 are polyimide helium extraction membranes with a He / CH4 selectivity of 154 and an N2 / CH4 selectivity of 1.5. M603 and M604 are perfluorinated nitrogen removal membranes (same as in Example 2) with an N2 / CH4 selectivity of 6 and a He / CH4 selectivity of 200. The permeate side of the membrane separation units is at atmospheric pressure.

[0101] Raw material gas 601 enters helium extraction block M601, with permeate gas being helium-rich gas 604. To further improve helium recovery, residual permeate gas 603 from M601 re-enters helium extraction membrane M602 for helium extraction. Permeate gas 606, after being regulated in temperature and pressure by a compressor with a cooling system, is mixed with 601 and returned to M601. Residual permeate gas 605 from M602 enters the denitrification block.

[0102] The residual gas 609 after nitrogen removal from membrane M603 is purified gas. The permeate gas 610 is re-entered into nitrogen removal membrane M604 after temperature and pressure adjustment by a compressor with a cooling system. The residual gas 612 is mixed with 605 and returned to M603, achieving a high methane recovery rate. The permeate gas 613 is high-nitrogen tail gas.

[0103] Using this process, the helium concentration of helium-rich gas 604 is 1.31%, the nitrogen content of purified gas 609 is no higher than 4%, the helium recovery rate is 92.48%, the methane recovery rate is 93.16%, and the logistics table is shown in Table 14.

[0104] Table 14

[0105] Example 15 Adopting attachment Figure 6 The process is shown below. The composition and pressure of the feed gas 601 are the same as in Example 3, and the temperature is 120°C. Membrane separation units M601 and M602 are polyimide helium extraction membranes (same as in Example 2, performance changes are caused by temperature changes), with a He / CH4 selectivity of 120 and an N2 / CH4 selectivity of 1.2. M603 and M604 are perfluorinated nitrogen removal membranes (same as in Example 2, performance changes are caused by temperature changes), with an N2 / CH4 selectivity of 4 and a He / CH4 selectivity of 160. The permeate side of the membrane separation units is at atmospheric pressure.

[0106] Raw material gas 601 enters helium extraction block M601, with permeate gas being helium-rich gas 604. To further improve helium recovery, residual permeate gas 603 from M601 re-enters helium extraction membrane M602 for helium extraction. Permeate gas 606, after being regulated in temperature and pressure by a compressor with a cooling system, is mixed with 601 and returned to M601. Residual permeate gas 605 from M602 enters the denitrification block.

[0107] The residual gas 609 after nitrogen removal from membrane M603 is purified gas. The permeate gas 610 is re-entered into nitrogen removal membrane M604 after temperature and pressure adjustment by a compressor with a cooling system. The residual gas 612 is mixed with 605 and returned to M603, achieving a high methane recovery rate. The permeate gas 613 is high-nitrogen tail gas.

[0108] Using this process, the helium concentration of helium-rich gas 604 is 1.24%, the nitrogen content of purified gas 609 is no higher than 4%, the helium recovery rate is 92.07%, the methane recovery rate is 91.22%, and the logistics table is shown in Table 15.

[0109] Table 15

[0110] Example 16 Adopting attachment Figure 6 The process is shown below. The composition, temperature, and pressure of the feed gas 601 are the same as in Example 3. Membrane separation units M601 and M602 are polyimide helium extraction membranes with a He / CH4 selectivity of 200 and an N2 / CH4 selectivity of 1.2. M603 and M604 are perfluorinated nitrogen removal membranes (same as in Example 2) with an N2 / CH4 selectivity of 6 and a He / CH4 selectivity of 200. The permeate side of the membrane separation units is at atmospheric pressure.

[0111] Raw material gas 601 enters helium extraction block M601, with permeate gas being helium-rich gas 604. To further improve helium recovery, residual permeate gas 603 from M601 re-enters helium extraction membrane M602 for helium extraction. Permeate gas 606, after being regulated in temperature and pressure by a compressor with a cooling system, is mixed with 601 and returned to M601. Residual permeate gas 605 from M602 enters the denitrification block.

[0112] The residual gas 609 after nitrogen removal from membrane M603 is purified gas. The permeate gas 610 is re-entered into nitrogen removal membrane M604 after temperature and pressure adjustment by a compressor with a cooling system. The residual gas 612 is mixed with 605 and returned to M603, achieving a high methane recovery rate. The permeate gas 613 is high-nitrogen tail gas.

[0113] Using this process, the helium concentration of helium-rich gas 604 is 1.30%, the nitrogen content of purified gas 609 is no higher than 4%, the helium recovery rate is 94.00%, the methane recovery rate is 92.68%, and the logistics table is shown in Table 16.

[0114] Table 16

[0115] Example 17 Adopting attachment Figure 6 The process is shown below. The composition, temperature, and pressure of the feed gas 601 are the same as in Example 3. Membrane separation units M601 and M602 are polyimide helium extraction membranes with a He / CH4 selectivity of 154 and an N2 / CH4 selectivity of 1.5. M603 and M604 are perfluorinated nitrogen removal membranes with an N2 / CH4 selectivity of 8 and a He / CH4 selectivity of 100. The permeate side of the membrane separation units is at atmospheric pressure.

[0116] The perfluorinated copolymer was dissolved in 6.2 g of 3M Fluorinert FC40 (boiling point 165°C) and 92.8 g of 3M Novec (boiling point 61°C). TM A 1 wt% coating solution was obtained by ultrasonically dispersing the mixture in a 7100 mixed solvent. This coating solution was then coated onto a polysulfone-supported substrate film. After drying, plasma treatment was performed for 20 seconds using CF4 as the medium and a 13.56 kHz power supply to obtain a perfluorinated nitrogen-removed membrane. The monomers of the perfluorinated copolymer were: and ; Raw material gas 601 enters helium extraction block M601, with permeate gas being helium-rich gas 604. To further improve helium recovery, residual permeate gas 603 from M601 re-enters helium extraction membrane M602 for helium extraction. Permeate gas 606, after being regulated in temperature and pressure by a compressor with a cooling system, is mixed with 601 and returned to M601. Residual permeate gas 605 from M602 enters the denitrification block.

[0117] The residual gas 609 after nitrogen removal from membrane M603 is purified gas. The permeate gas 610 is re-entered into nitrogen removal membrane M604 after temperature and pressure adjustment by a compressor with a cooling system. The residual gas 612 is mixed with 605 and returned to M603, achieving a high methane recovery rate. The permeate gas 613 is high-nitrogen tail gas.

[0118] Using this process, the helium concentration of helium-rich gas 604 is 1.31%, the nitrogen content of purified gas 609 is no higher than 4%, the helium recovery rate is 92.48%, the methane recovery rate is 94.11%, and the logistics table is shown in Table 17.

[0119] Table 17

[0120] Example 18 Adopting attachment Figure 6 The process is shown below. The composition, temperature, and pressure of the feed gas 601 are the same as in Example 3. Membrane separation units M601 and M602 are polyimide helium extraction membranes with a He / CH4 selectivity of 200 and an N2 / CH4 selectivity of 1.2. M603 and M604 are perfluorinated nitrogen removal membranes (same as in Example 17) with an N2 / CH4 selectivity of 8 and a He / CH4 selectivity of 100. The permeate side of the membrane separation units is at atmospheric pressure.

[0121] Raw material gas 601 enters helium extraction block M601, with permeate gas being helium-rich gas 604. To further improve helium recovery, residual permeate gas 603 from M601 re-enters helium extraction membrane M602 for helium extraction. Permeate gas 606, after being regulated in temperature and pressure by a compressor with a cooling system, is mixed with 601 and returned to M601. Residual permeate gas 605 from M602 enters the denitrification block.

[0122] The residual gas 609 after nitrogen removal from membrane M603 is purified gas. The permeate gas 610 is re-entered into nitrogen removal membrane M604 after temperature and pressure adjustment by a compressor with a cooling system. The residual gas 612 is mixed with 605 and returned to M603, achieving a high methane recovery rate. The permeate gas 613 is high-nitrogen tail gas.

[0123] Using this process, the helium concentration of helium-rich gas 604 is 1.30%, the nitrogen content of purified gas 609 is no higher than 4%, the helium recovery rate is 94.00%, the methane recovery rate is 93.70%, and the logistics table is shown in Table 18.

[0124] Table 18

[0125] Example 19 Adopting attachment Figure 6The process flow is shown below. The feed gas 601 consists of 15.4% N2, 84.57% CH4, and 0.03% He. The feed gas pressure is 30 bar, and the temperature is 50°C. Membrane separation units M601 and M602 are polyimide helium extraction membranes with a He / CH4 selectivity of 40 and an N2 / CH4 selectivity of 1.5. M603 and M604 are perfluorinated nitrogen removal membranes (same as in Example 2) with an N2 / CH4 selectivity of 6 and a He / CH4 selectivity of 200. The permeate side of membrane separation unit M601 is at 0.1 bar, while the rest are at atmospheric pressure.

[0126] Raw material gas 601 enters helium extraction block M601, with permeate gas being helium-rich gas 604. To further improve helium recovery, residual permeate gas 603 from M601 re-enters helium extraction membrane M602 for helium extraction. Permeate gas 606, after being regulated in temperature and pressure by a compressor with a cooling system, is mixed with 601 and returned to M601. Residual permeate gas 605 from M602 enters the denitrification block.

[0127] The residual gas 609 after nitrogen removal from membrane M603 is purified gas. The permeate gas 610 is re-entered into nitrogen removal membrane M604 after temperature and pressure adjustment by a compressor with a cooling system. The residual gas 612 is mixed with 605 and returned to M603, achieving a high methane recovery rate. The permeate gas 613 is high-nitrogen tail gas.

[0128] Using this process, the helium concentration of helium-rich gas 604 is 1.02%, the nitrogen content of purified gas 609 is no higher than 4%, the helium recovery rate is 91.19%, the methane recovery rate is 95.41%, and the logistics table is shown in Table 19.

[0129] Table 19

[0130] Example 20 Adopting attachment Figure 7 The process flow is shown below. The feed gas 701 composition is: 15.4% N2, 84.57% CH4, and 0.03% He. The feed gas pressure is 30 bar, and the temperature is 50°C. Membrane separation units M701, M702, and M703 are polyimide helium extraction membranes with a He / CH4 selectivity of 154 and an N2 / CH4 selectivity of 1.5. M704 and M705 are perfluorinated nitrogen removal membranes (same as in Example 2), with an N2 / CH4 selectivity of 6 and a He / CH4 selectivity of 200. The permeate side of each membrane separation unit is at atmospheric pressure.

[0131] After the feed gas 701 is mixed with the permeate from M702, it enters the helium extraction block M701. The helium concentration of the permeate 704 is enriched once. After 704 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it enters the helium extraction membrane M703 for further helium enrichment. The permeate 710 is helium-rich. To improve the helium recovery rate, the residual permeate 703 from M701 enters the helium extraction membrane M702. The permeate 706 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it is mixed with the feed gas 701 and then enters M701. The residual permeates from M702 and M703 enter the denitrification block M704. The residual permeate 712 is purified gas. To improve the CH4 recovery rate, the permeate 713 from M704 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it undergoes denitrification again before entering M705. The permeate 716 is high-nitrogen tail gas. The residual permeate 715 is mixed with 705 and 709 and returned to M704.

[0132] Using this process, the helium concentration of helium-rich gas 710 is 1.68%, the nitrogen content of purified gas 712 is no higher than 4%, the helium recovery rate is 98.50%, the methane recovery rate is 96.66%, and the logistics table is shown in Table 20.

[0133] Table 20

[0134] Example 21 Adopting attachment Figure 7 The process flow is shown below. The feed gas 701 composition is: 20.4% N2, 79.57% CH4, and 0.03% He. The feed gas pressure is 30 bar, and the temperature is 50°C. Membrane separation units M701, M702, and M703 are polyimide helium extraction membranes with a He / CH4 selectivity of 154 and an N2 / CH4 selectivity of 1.5. M704 and M705 are perfluorinated nitrogen removal membranes (same as in Example 2), with an N2 / CH4 selectivity of 6 and a He / CH4 selectivity of 200. The permeate side of each membrane separation unit is at atmospheric pressure.

[0135] After the feed gas 701 is mixed with the permeate from M702, it enters the helium extraction block M701. The helium concentration of the permeate 704 is enriched once. After 704 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it enters the helium extraction membrane M703 for further helium enrichment. The permeate 710 is helium-rich. To improve the helium recovery rate, the residual permeate 703 from M701 enters the helium extraction membrane M702. The permeate 706 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it is mixed with the feed gas 701 and then enters M701. The residual permeates from M702 and M703 enter the denitrification block M704. The residual permeate 712 is purified gas. To improve the CH4 recovery rate, the permeate 713 from M704 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it undergoes denitrification again before entering M705. The permeate 716 is high-nitrogen tail gas. The residual permeate 715 is mixed with 705 and 709 and returned to M704.

[0136] Using this process, the helium concentration of helium-rich gas 710 is 1.63%, the nitrogen content of purified gas 712 is no higher than 4%, the helium recovery rate is 98.50%, the methane recovery rate is 96.88%, and the logistics table is shown in Table 21.

[0137] Table 21

[0138] Example 22 Adopting attachment Figure 7 The process flow is shown below. The feed gas 701 composition is: 20.4% N2, 79.59% CH4, and 0.01% He. The feed gas pressure is 30 bar, and the temperature is 50°C. Membrane separation units M701, M702, and M703 are polyimide helium extraction membranes with a He / CH4 selectivity of 154 and an N2 / CH4 selectivity of 1.5. M704 and M705 are perfluorinated nitrogen removal membranes (same as in Example 2), with an N2 / CH4 selectivity of 6 and a He / CH4 selectivity of 200. The permeate side of each membrane separation unit is at atmospheric pressure.

[0139] After the feed gas 701 is mixed with the permeate from M702, it enters the helium extraction block M701. The helium concentration of the permeate 704 is enriched once. After 704 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it enters the helium extraction membrane M703 for further helium enrichment. The permeate 710 is helium-rich. To improve the helium recovery rate, the residual permeate 703 from M701 enters the helium extraction membrane M702. The permeate 706 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it is mixed with the feed gas 701 and then enters M701. The residual permeates from M702 and M703 enter the denitrification block M704. The residual permeate 712 is purified gas. To improve the CH4 recovery rate, the permeate 713 from M704 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it undergoes denitrification again before entering M705. The permeate 716 is high-nitrogen tail gas. The residual permeate 715 is mixed with 705 and 709 and returned to M704.

[0140] Using this process, the helium concentration of helium-rich gas 710 is 1.01%, the nitrogen content of purified gas 712 is no higher than 4%, the helium recovery rate is 97.06%, the methane recovery rate is 96.86%, and the logistics table is shown in Table 22.

[0141] Table 22

[0142] Example 23 Adopting attachment Figure 7 The process flow is shown below. The feed gas 701 has the following composition: 15.4% N2, 84.57% CH4, and 0.03% He. The feed gas pressure is 30 bar, and the temperature is 50°C. Membrane separation units M701, M702, and M703 are polyimide helium extraction membranes with a He / CH4 selectivity of 40 and an N2 / CH4 selectivity of 1.5. M704 and M705 are perfluorinated nitrogen removal membranes (same as in Example 2) with an N2 / CH4 selectivity of 6 and a He / CH4 selectivity of 200. The permeate side of each membrane separation unit is at atmospheric pressure.

[0143] After the feed gas 701 is mixed with the permeate from M702, it enters the helium extraction block M701. The helium concentration of the permeate 704 is enriched once. After 704 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it enters the helium extraction membrane M703 for further helium enrichment. The permeate 710 is helium-rich. To improve the helium recovery rate, the residual permeate 703 from M701 enters the helium extraction membrane M702. The permeate 706 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it is mixed with the feed gas 701 and then enters M701. The residual permeates from M702 and M703 enter the denitrification block M704. The residual permeate 712 is purified gas. To improve the CH4 recovery rate, the permeate 713 from M704 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it undergoes denitrification again before entering M705. The permeate 716 is high-nitrogen tail gas. The residual permeate 715 is mixed with 705 and 709 and returned to M704.

[0144] Using this process, the helium concentration of helium-rich gas 710 is 1.60%, the nitrogen content of purified gas 712 is no higher than 4%, the helium recovery rate is 93.77%, the methane recovery rate is 96.66%, and the logistics table is shown in Table 23.

[0145] Table 23

[0146] Example 24 Adopting attachment Figure 7 The process flow is shown below. The feed gas 701 composition is: 15.4% N2, 84.59% CH4, and 0.01% He. The feed gas pressure is 30 bar, and the temperature is 50°C. Membrane separation units M701, M702, and M703 are polyimide helium extraction membranes with a He / CH4 selectivity of 40 and an N2 / CH4 selectivity of 1.5. M704 and M705 are perfluorinated nitrogen removal membranes (same as in Example 2), with an N2 / CH4 selectivity of 6 and a He / CH4 selectivity of 200. The permeate side of MEM703 is 0.1 bar, while the permeate sides of the other membrane separation units are at atmospheric pressure.

[0147] After the feed gas 701 is mixed with the permeate from M702, it enters the helium extraction block M701. The helium concentration of the permeate 704 is enriched once. After 704 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it enters the helium extraction membrane M703 for further helium enrichment. The permeate 710 is helium-rich. To improve the helium recovery rate, the residual permeate 703 from M701 enters the helium extraction membrane M702. The permeate 706 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it is mixed with the feed gas 701 and then enters M701. The residual permeates from M702 and M703 enter the denitrification block M704. The residual permeate 712 is purified gas. To improve the CH4 recovery rate, the permeate 713 from M704 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it undergoes denitrification again before entering M705. The permeate 716 is high-nitrogen tail gas. The residual permeate 715 is mixed with 705 and 709 and returned to M704.

[0148] Using this process, the helium concentration of helium-rich gas 710 is 1.50%, the nitrogen content of purified gas 712 is no higher than 4%, the helium recovery rate is 91.00%, the methane recovery rate is 97.62%, and the logistics table is shown in Table 24.

[0149] Table 24

[0150] Comparative Example 1 Adopting attachment Figure 2 The process flow is shown. The composition, temperature, and pressure of the feed gas 201 are the same as in Example 9. Except for the denitrification block M202, which is replaced with a polyimide membrane (He / CH4 selectivity 154, N2 / CH4 selectivity 1.5), the setup of the remaining membrane separation units is exactly the same as in Example 9. Membrane separation units M201 and M203 are both perfluorinated membranes with He / CH4 selectivity 200 and N2 / CH4 selectivity 6. The permeate side of M201 is 0.1 bar, while the permeate sides of M202 and M203 are at atmospheric pressure.

[0151] Raw material gas 201 enters M201 in the helium extraction block. The permeate gas is helium-rich gas 202. The residual permeate gas 203 mixes with the residual permeate gas 209 from the nitrogen-removed membrane M203 to form 204, which enters M202 in the denitrification block. The resulting residual permeate gas 205 is purified gas. The permeate gas 206 is pressurized to 30 bar and cooled to 50°C after passing through a compressor with a cooling system. The residual permeate gas 209 generated by M203 is returned to M202. The permeate gas 208 is high-nitrogen tail gas.

[0152] Using this process, the helium concentration of helium-rich gas 202 is 1.81%, the nitrogen content of purified gas 205 is 9.25%, the helium recovery rate is 97.39%, the methane recovery rate is 89.69%, and the logistics table is shown in Table 25.

[0153] Compared with Example 9, Comparative Example 1 reduced the N2 / CH4 selectivity of the M202 nitrogen removal membrane, failing to meet the requirements of methane recovery rate greater than 90% and nitrogen content not exceeding 4%.

[0154] Table 25

[0155] Comparative Example 2 Adopting attachment Figure 7 The process flow is shown. The feed gas composition, temperature, and pressure are the same as in Example 24. Except for membrane separation units M701, M702, and M703, which are polyimide membranes with a He / CH4 selectivity of 20 and an N2 / CH4 selectivity of 1.5, all membrane separation units are configured exactly the same as in Example 24. M704 and M705 are perfluorinated nitrogen removal membranes with an N2 / CH4 selectivity of 6 and a He / CH4 selectivity of 200. The permeate side of MEM703 is 0.1 bar, while the permeate sides of the other units are at atmospheric pressure.

[0156] After the feed gas 701 is mixed with the permeate from M702, it enters the helium extraction block M701. The helium concentration of the permeate 704 is enriched once. After 704 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it enters the helium extraction membrane M703 for further helium enrichment. The permeate 710 is helium-rich. To improve the helium recovery rate, the residual permeate 703 from M701 enters the helium extraction membrane M702. The permeate 706 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it is mixed with the feed gas 701 and then enters M701. The residual permeates from M702 and M703 enter the denitrification block M704. The residual permeate 712 is purified gas. To improve the CH4 recovery rate, the permeate 713 from M704 is regulated by a compressor with a cooling system, its temperature and pressure are adjusted before it undergoes denitrification again before entering M705. The permeate 716 is high-nitrogen tail gas. The residual permeate 715 is mixed with 705 and 709 and returned to M704.

[0157] Using this process, the helium concentration of helium-rich gas 710 is 0.99%, the nitrogen content of purified gas 712 is no more than 4%, the helium recovery rate is 59.54%, the methane recovery rate is 97.63%, and the logistics table is shown in Table 26.

[0158] Compared with Example 24, Comparative Example 2 reduced the He / CH4 selectivity of the helium extraction membrane, failing to meet the requirements of a helium recovery rate greater than 90% and a concentration of not less than 1%.

[0159] Table 26

[0160] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for simultaneous purification and extraction of high-value components from helium-poor and ultra-helium-poor natural gas, characterized in that, The method includes: The helium-poor and ultra-helium-poor natural gas is first extracted through the helium extraction membrane block, and then the residual gas enters the nitrogen removal membrane block for nitrogen removal. The helium extraction membrane block uses a helium extraction membrane, which preferentially permeates with helium, and the He / CH4 selectivity is at least 40. The nitrogen removal membrane block uses nitrogen removal membrane, which preferentially permeates nitrogen, with an N2 / CH4 selectivity of at least 4.

2. The method according to claim 1, characterized in that, The He / CH4 selectivity of the helium extraction membrane is at least 100. The nitrogen removal membrane has an N2 / CH4 selectivity of at least 6.

3. The method according to claim 1, characterized in that, The helium extraction membrane is at least one of the following: cellulose acetate membrane, polybenzimidazole membrane, polyimide membrane, polyetherimide membrane, polymethyl methacrylate membrane, and perfluorinated copolymer membrane. The nitrogen removal membrane is at least one of the following: polytetrafluoroethylene membrane, (1,2,2-trifluorovinyl)1,1,2,2,3,4,4-heptafluoro-3-butene ether cyclized polymer membrane, and perfluorinated copolymer membrane.

4. The method according to claim 1, characterized in that, The operating temperature of the method is -50~150℃; the operating pressure is 10~150 bar.

5. The method according to claim 1, characterized in that, The helium extraction membrane block and / or nitrogen removal membrane block adopt a multi-stage and multi-segment process, and the blocks are connected and coupled to each other or within each block through permeate gas, residual permeate gas or their reflux phase.

6. The method according to claim 5, characterized in that, The helium extraction membrane block includes one helium extraction membrane separation unit, and the nitrogen removal membrane block includes two nitrogen removal membrane separation units. The process includes the following steps: The raw material gas I enters the helium extraction membrane separation unit to obtain permeate gas I and residual gas I, wherein the permeate gas I is a helium-rich gas; The residual gas I enters the nitrogen removal membrane separation unit I to obtain permeate gas II and residual gas II, wherein the residual gas II is purified gas; The permeate gas II is compressed and then enters the nitrogen removal membrane separation unit II to obtain permeate gas III and residual gas III. The permeate gas III is a high-nitrogen tail gas. The residual gas III is mixed with the raw material gas I and then returned to the helium extraction membrane separation unit, or the residual gas III is mixed with the residual gas I and then returned to the nitrogen removal membrane separation unit I.

7. The method according to claim 5, characterized in that, The helium extraction membrane block includes one helium extraction membrane separation unit, and the nitrogen removal membrane block includes three nitrogen removal membrane separation units. This includes process flow a, process flow b, or process flow c; Process flow a: Raw material gas I enters the helium extraction membrane separation unit to obtain permeate gas I and residual gas I, wherein permeate gas I is a helium-rich gas; The residual gas I enters the nitrogen removal membrane separation unit I to obtain permeate gas II and residual gas II, wherein the residual gas II is purified gas; The permeate gas II is compressed and then enters the nitrogen demembrane separation unit II to obtain permeate gas III and residual gas III. The residual gas III is mixed with the residual gas I and then returned to the nitrogen demembrane separation unit I. The permeate gas III is compressed and then enters the nitrogen removal membrane separation unit III to obtain permeate gas IV and residual gas IV. The permeate gas IV is a high-nitrogen tail gas. The residual gas IV and residual gas I are mixed and then returned to the nitrogen removal membrane separation unit I. Process flow b: Raw material gas I enters the helium extraction membrane separation unit to obtain permeate gas I and residual gas I, wherein permeate gas I is a helium-rich gas; The residual gas I enters the nitrogen removal membrane separation unit I to obtain permeate gas II and residual gas II; The permeate gas II is compressed and then enters the nitrogen removal membrane separation unit II to obtain permeate gas III and residual gas III. The permeate gas III is a high-nitrogen tail gas. The residual gas III and residual gas I are mixed and then returned to nitrogen removal membrane separation unit I; The residual gas II enters the nitrogen removal membrane separation unit III to obtain permeate gas IV and residual gas IV, wherein the residual gas IV is purified gas. The permeate gas IV is compressed, mixed with residual permeate gas I, and then returned to the nitrogen removal membrane separation unit I. Option c: The raw material gas I enters the helium extraction membrane separation unit to obtain permeate gas I and residual gas I, wherein the permeate gas I is a helium-rich gas; The residual gas I enters the nitrogen removal membrane separation unit I to obtain permeate gas II and residual gas II; The permeate gas II is compressed and then enters the nitrogen removal membrane separation unit II to obtain permeate gas III and residual gas III. The permeate gas III is a high-nitrogen tail gas. After being mixed with residual gas II, the residual gas III enters nitrogen removal membrane separation unit III to obtain permeate gas IV and residual gas IV, wherein the residual gas IV is purified gas. The permeate gas IV is compressed, mixed with residual permeate gas I, and then returned to the nitrogen removal membrane separation unit I.

8. The method according to claim 5, characterized in that, The helium extraction membrane block includes two helium extraction membrane separation units, and the nitrogen removal membrane block includes two nitrogen removal membrane separation units. The process includes the following steps: The raw material gas I enters the helium extraction membrane separation unit I to obtain permeate gas I and residual gas I, wherein the permeate gas I is a helium-rich gas. The residual gas I enters the helium extraction membrane separation unit II to obtain permeate gas II and residual gas II; The permeate gas II is compressed, mixed with the raw material gas I, and then returned to the helium extraction membrane separation unit I. The residual gas II enters the nitrogen removal membrane separation unit I to obtain permeate gas III and residual gas III, wherein the residual gas III is purified gas; The permeate gas III is compressed and then enters the nitrogen removal membrane separation unit II to obtain permeate gas IV and residual gas IV. The permeate gas IV is a high-nitrogen tail gas. The residual gas IV and residual gas II are mixed and then returned to the nitrogen removal membrane separation unit I.

9. The method according to claim 5, characterized in that, The helium extraction membrane block includes three helium extraction membrane separation units, and the nitrogen removal membrane block includes two nitrogen removal membrane separation units. The process includes the following steps: The feed gas I enters the helium extraction membrane separation unit I to obtain permeate gas I and residual gas I; The permeate gas I is compressed and then enters the helium extraction membrane separation unit II to obtain permeate gas II and residual gas II. The permeate gas II is a helium-rich gas. The residual gas I enters the helium extraction membrane separation unit III to obtain permeate gas III and residual gas III; The permeate gas III is compressed, mixed with the raw material gas I, and then returned to the helium extraction membrane separation unit I. After the residual gas II and residual gas III are mixed, they enter the nitrogen removal membrane separation unit I to obtain permeate gas IV and residual gas IV, wherein the residual gas IV is the purified gas. The permeate gas IV is compressed and then enters the nitrogen removal membrane separation unit II to obtain permeate gas V and residual gas V, wherein the permeate gas V is a high-nitrogen tail gas. The residual gas V is mixed with residual gas II and residual gas III and then returned to the nitrogen removal membrane separation unit I.

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