Gas separation membrane unit, gas separation system, and, method for producing an enriched gas using the gas separation system

Description

56 GAS SEPARATION MEMBRANE UNIT, GAS SEPARATION SYSTEM, AND METHOD FOR PRODUCING ENRICHED GAS USING A GAS SEPARATION SYSTEM TECHNICAL FIELD

[001] The present invention relates to a gas separation membrane unit including a plurality of modules, a gas separation system that separates a mixed gas using the gas separation membrane unit, and a method for producing an enriched gas using the gas separation system. FUNDAMENTALS OF THE INVENTION

[002] As a method for separating a mixed gas containing two or more different types of gases into respective gases, a membrane separation method is known using a difference in the permeation rate of a gas with respect to a membrane. In this method, a high-purity, high-permeability gas and / or a high-purity, low-permeability gas, which are target gases, can be obtained by collecting the permeated gas and / or the non-permeated gas. The permeation rate, which is the permeation volume per unit area of ​​film, unit time, and unit partial pressure difference of each gas contained in the mixed gas with respect to the film, can be expressed by P' (unit: x10-5cm3(STP) / cm2,s*cmHg). The gas separation selectivity of the membrane can also be expressed as (permeation rate of high-permeability gas / permeation rate of low-permeability gas).

[003] It has been described that a gas separation membrane unit with predetermined gas permeability and gas separation selectivity, in which the gas separation membrane modules are combined in parallel, is used to separate a feedstock gas mixture (e.g., Patent Literature 1 and Patent Literature 2). CITATION LIST Petition 870260061636, dated 06 / 23 / 2026, page 12 / 82 / 56 Patent Literature

[004] Patent Literature 1: JP2013-128868A

[005] Patent Literature 2: US2020 / 0316516A1 SUMMARY OF THE INVENTION Technical Problem

[006] In the related technique, variations in gas permeability and gas separation selectivity in a gas separation membrane module within a gas separation membrane unit are not evaluated absolutely, including a case of gas separation performance evaluation by simulation as described in Patent Literature 2.

[007] However, in a gas separation membrane unit in which a plurality of gas separation membrane modules are combined, the gas permeability and gas separation selectivity actually vary between the modules. The present inventors observed that the conventional gas separation membrane unit does not achieve the product gas purity and / or product gas recovery rate originally considered because of variations in gas permeability and gas separation selectivity between the modules.

[008] Thus, it is an objective of the present invention to provide a gas separation membrane unit, a gas separation system, and a method for producing an enriched gas, which can solve the aforementioned drawbacks of the prior art, and achieve the product gas purity and / or product gas recovery rate originally considered. SOLUTION TO THE PROBLEM

[009] The present invention provides the following configuration.

[0010] [1] A gas separation membrane unit in which a feedstock gas mixture is supplied to concentrate and enrich at least one of the gases contained in the feedstock gas mixture, wherein the gas separation membrane unit Petition 870260061636, dated 06 / 23 / 2026, page 13 / 82 / 56 comprises a plurality of gas separation membrane modules combined in parallel, each of the gas separation membrane modules comprising: a gas inlet; an impermeable gas outlet;and a permeate gas outlet, the gas inlets of each of the gas separation membrane modules are shared to constitute the gas inlet of the gas separation membrane unit, the non-permeate gas outlets of each of the gas separation membrane modules are shared to constitute the non-permeate gas outlet of the gas separation membrane unit, the permeate gas outlets of each of the gas separation membrane modules are shared to constitute the permeate gas outlet of the gas separation membrane unit, and a coefficient of variation of a gas separation selectivity among the plurality of gas separation membrane modules is 0.01 or more and 0.49 or less, or a coefficient of variation of a gas permeability among the plurality of gas separation membrane modules is 0.01 or more and 0.49 or less.

[0011] [2] The gas separation membrane unit according to [1], wherein the gas separation membrane constituting the gas separation membrane module is a hollow fiber membrane with an asymmetric structure made of a polymer.

[0012] [3] The gas separation membrane unit according to [1] or [2], where (1) or (2) is as follows: (1) The feedstock gas mixture contains carbon dioxide (CO2) and methane (CH4), the gas separation selectivity is a permeation rate ratio P'CO2 / P'CH4 of CO2 to CH4, Petition 870260061636, dated 06 / 23 / 2026, page 14 / 82 / 56: gas permeability is a permeation rate P'CÜ2 of CO2, and the unit of permeation rate is cm3(STP) / cm2· s · cmHg; (2) The feedstock gas mixture contains nitrogen (N2) and oxygen (O2), the gas separation selectivity is a P'O2 / P'N2 permeation rate ratio of O2 to N2, the gas permeability is a PO2 permeation rate of O2, and the unit of permeation rate is cm3(STP) / cm2· s · cmHg.

[0013] [4] A gas separation system for supplying a feedstock gas mixture to a gas separation membrane unit for concentrating and enriching at least one of the gases contained in the feedstock gas mixture, wherein the gas separation system comprises at least one first gas separation membrane unit comprising a gas inlet, the gas separation system comprises: a feedstock gas mixture supply line connected to the gas inlet of the first gas separation membrane unit; and a compression means disposed in the feedstock gas mixture supply line; the first gas separation membrane unit comprises the gas separation membrane unit according to any one of [1] to [3].

[0014] [5] A gas separation system for supplying a feedstock gas mixture to a gas separation membrane unit for concentrating and enriching at least one of the gases contained in the gas mixture. Petition 870260061636, dated 06 / 23 / 2026, page 15 / 82 / 56 raw material, wherein the gas separation system comprises: at least one first gas separation membrane unit comprising a gas inlet and a non-permeated gas outlet; and a second gas separation membrane unit comprising a gas inlet and a permeated gas outlet, the gas separation system comprises: a feedstock gas mixture supply line connected to the gas inlet of the first gas separation membrane unit; a compression method installed in the feedstock gas mixture supply line; a first line connecting the non-permeated gas outlet of the first gas separation membrane unit and the gas inlet of the second gas separation membrane unit; and a second line connecting the permeated gas outlet of the second gas separation membrane unit and the feedstock gas mixture supply line, and at least one of the first gas separation membrane unit and the second gas separation membrane unit comprises the gas separation membrane unit according to any one of [1] to [3].

[0015] [6] A gas separation system for supplying a feedstock gas mixture to a gas separation membrane unit for concentrating and enriching at least one of the gases contained in the feedstock gas mixture, wherein the gas separation system comprises: a first gas separation membrane unit comprising a gas inlet, a non-permeated gas outlet and a Petition 870260061636, dated 06 / 23 / 2026, page 16 / 82 / 56 permeate gas outlet; A second gas separation membrane unit comprising a gas inlet and a permeate gas outlet; and a third gas separation membrane unit comprising a gas inlet and a non-permeate gas outlet, the gas separation system comprises: a feedstock gas mixture supply line connected to the gas inlet of the first gas separation membrane unit; a compression method installed in the feedstock gas mixture supply line; a first line connecting the non-permeated gas outlet of the first gas separation membrane unit and the gas inlet of the second gas separation membrane unit; a second line connecting the permeate gas outlet of the second gas separation membrane unit and the feedstock gas mixture supply line; and a third line connecting the permeate gas outlet of the first gas separation membrane unit and the gas inlet of the third gas separation membrane unit; and a fourth line connecting the non-permeate gas outlet of the third gas separation membrane unit and the feedstock gas mixture supply line, and at least one of the first gas separation membrane unit, the second gas separation membrane unit and the third gas separation membrane unit comprises the gas separation membrane unit according to any one of [1] to [3].

[0016] [7] A method for producing an enriched gas using the gas separation system according to [5] or [6], wherein the gas Petition 870260061636, dated 06 / 23 / 2026, page 17 / 82 / 56 enriched is removed from the non-permeated gas outlet of the second gas separation membrane unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Fig. 1 is a schematic diagram showing a configuration of a gas separation system according to a first embodiment of the present invention.

[0018] Fig. 2 is a schematic view showing a structure of an example of a gas separation membrane module used in the gas separation system of the present invention.

[0019] Fig. 3 is a schematic view showing an example of a method for connecting gas separation membrane modules used in the gas separation system of the present invention.

[0020] Fig. 4 is a schematic diagram showing a configuration of a gas separation system according to a second embodiment of the present invention.

[0021] Fig. 5 is a schematic diagram showing a configuration of a gas separation system according to a third embodiment of the present invention. DESCRIPTION OF MODALITIES

[0022] The present invention will now be described based on preferred embodiments thereof with reference to the drawings. In this descriptive report, the term “considered product gas purity and product gas recovery rate” refers to the purity and recovery rate calculated by simulation, for example, on the assumption that the coefficient of variation of the gas permeation rate or gas separation selectivity of the plurality of gas separation membrane modules constituting the gas separation membrane unit is zero, or values ​​close to such calculated purity and recovery rate.

[0023] The upper limit and the lower limit of the numerical values ​​in Petition 870260061636, dated 06 / 23 / 2026, page 18 / 82 / 56, the present descriptive report may be combined without any limitation.

[0024] It should be noted that the expression “connecting A and B by line C” or “line C connecting A and B” encompasses both cases where A, B, and line C are separate members, and cases where A and / or C are integrally formed as a single member. Similarly, the expression “connecting line E to D” also encompasses both cases where D and line E are separate members, and cases where D and line E are formed as a single member.

[0025] Each of the gas separation systems shown in Figs. 1 and 3 includes a first gas separation membrane unit 11 and a second gas separation membrane unit 12. The gas separation system shown in Fig. 4 additionally includes a third gas separation membrane unit 13. The gas separation system shown in Fig. 1 includes a first gas separation membrane unit 11.

[0026] As gas separation membrane units 11, 12 and 13, for example, as shown in Fig. 2, a module 40 in which a gas separation membrane 30 made of a hollow fiber membrane or similar and with selective gas permeability is accommodated in an enclosure 31 can be used. Each of the gas separation membrane units 11, 12 and 13 shown in Figs. 1 and 4 includes, for example, a plurality of gas separation membrane modules 40 shown in Fig. 2 combined in parallel. Two opposite surfaces of the housing 31 of module 40 are opened to form an opening 32. It should be noted that the opening 32 is for inserting the gas separation membrane 30 into the housing 31, and is not an opening of the gas separation membrane 30 itself. The gas separation membrane 30 is accommodated in the housing 31 through the opening 32. In the case where the gas separation membrane 30 is formed from a bundle of hollow fiber membranes, the gas separation membrane 30 is housed in the Petition 870260061636, dated 06 / 23 / 2026, page 19 / 82 / 56 enclosure 31 in the housed state such that each end portion of the hollow fiber membrane is open in the vicinity of each opening 32 of the enclosure 31.

[0027] The hollow fiber gas separation membrane module such as module 40 is obtained, for example, by preferably packing about 100 to 1,000,000 (more preferably about 100 to 200).000) Hollow fiber membranes of a suitable length to obtain a hollow fiber membrane bundle, fixing both end portions of the hollow fiber membrane bundle by a tube sheet made of a thermosetting resin or similar in such a way that at least one end of the hollow fiber is kept in an open state to obtain a hollow fiber membrane element made from the hollow fiber membrane bundle and the tube sheet or similar, and a hollow fiber membrane element made from the hollow fiber membrane bundle obtained, the tube sheet and so forth, and housing and fixing the hollow fiber membrane in a container with at least one mixed gas inlet, one permeate gas outlet, and one non-permeate gas outlet in such a way that a space communicating with the interior of the hollow fiber membrane and a space communicating with the exterior of the hollow fiber membrane are isolated from each other.

[0028] In a state where the gas separation membrane 30 is housed in the enclosure 31, the gas separation membrane 30 is fixed to the inner wall of the enclosure 31 by the tube plates 33 and 34 in positions of both end portions in the Y direction, which is the extension direction of the hollow fiber membrane. Each opening 32 of the enclosure 31 is closed by the covers 35 and 36. Cover 35 is provided with a gas inlet 37. Conversely, cover 36 is provided with an outlet for non-permeated gas 38. The mixed gas to be separated is introduced into the module through the gas inlet 37 of cover 35. Among the gases introduced, the gas that permeated the gas separation membrane 30 is discharged to the outside of the module through a Petition 870260061636, dated 06 / 23 / 2026, p. 20 / 82 / 56 permeate gas outlet 39 provided in the enclosure 31. On the other hand, the non-permeate gas that did not permeate the gas separation membrane 30 is discharged through the non-permeate gas outlet 38 of the cover 36 on the outside of the module.

[0029] As described herein, the gas separation membrane unit 11 (or 12 or 13) in this descriptive report is formed by combining a plurality of gas separation membrane modules 40 in parallel. Each of the gas separation membrane modules 40 has a gas inlet 37, a non-permeated gas outlet 38, and a permeated gas outlet 39. The gas inlets 37 of each of the gas separation membrane modules 40 are shared to constitute a gas inlet 11a (or 12a, 13a) of the gas separation membrane unit, the non-permeated gas outlets 38 of each of the gas separation membrane modules 40 are shared to constitute a non-permeated gas outlet 11b (or 12b, 13b) of the gas separation membrane unit, and the permeated gas outlets 39 of each of the gas separation membrane modules 40 are shared to constitute a permeated gas outlet 11c (or 12c, 13c) of the gas separation membrane unit.

[0030] In some cases, a purge gas supply port (not shown) may be provided in the enclosure 31. Although the separation membrane module of Fig. 2 has been described as an example, the present invention can be applied to separation membrane modules with other configurations, and can be applied, for example, to a shell-type feed module.

[0031] In the present invention, the flow rates of the modules can be the same or different. In the gas separation membrane system of the present invention, the flow rate of each module that constitutes a unit is not controlled by providing a valve or the like. When the entire length of the module is the maximum total length among the modules Petition 870260061636, dated 06 / 23 / 2026, p. 21 / 82 / 56 that constitute the single unit is L1 and the entire length of the module with the minimum total length among the modules that constitute the single unit is L2, {(L1-L2) / L1}^100 [unit: %] is preferably 10% or less, more preferably 5% or less, even more preferably 3% or less, and above all preferably 1% or less. The ratio, S1:S2, between the membrane area S1 of the module with the largest membrane area among the modules that constitute a single unit and the membrane area S2 of the module with the smallest membrane area among the modules is preferably 1:1 to 5, more preferably 1:1 to 3, even more preferably 1:1 to 1.5, and above all preferably 1:1 to 1.1.

[0032] Fig. 3 is a schematic diagram illustrating a gas separation membrane unit in which multiple gas separation membrane modules are connected in parallel. For example, the gas inlet 37 of each module is connected to a main tube that communicates both with the gas outlet of another unit and with the outside of the system by means of a distribution tube dp.

[0033] Also, the non-permeated gas outlet 38 of each module constituting the single unit communicates with a main tube that communicates with a gas inlet of another unit or a main tube that communicates with the outside of the system. For example, in the system of Fig. 1 to be described later, as described in Fig. 3, the non-permeated gas discharged from the non-permeated gas outlet 38 of each module of the first gas separation membrane unit 11 merges into a line 14 by a fusion tube cp1, and is supplied to the second gas separation membrane unit 12. Similarly, the non-permeated gas discharged from the non-permeated gas outlet 38 of each module of the second gas separation membrane unit 12 merges into the line 15 by a fusion tube (not shown), and is supplied to the second gas separation membrane unit 12.

[0034] Similarly, the permeate gas discharged from the gas outlet Petition 870260061636, dated 06 / 23 / 2026, p. 22 / 82 / 56 permeate 39 of each module constituting the single unit communicates with a main tube (not shown) by a fusion tube that merges with a main tube communicating with a gas inlet of another unit or the outside of the system. For example, in the embodiment of Fig. 1 to be described later, as described in Fig. 3, the permeate gas discharged from the permeate gas outlet 39 of each module of the first gas separation membrane unit 11 merges in line 18 by a fusion tube cp2, and is supplied to the outside of the system. Additionally, the permeate gas discharged from the permeate gas outlet 39 of each module of the second gas separation membrane unit 12 is fused into a line 17 by a fusion tube (not shown), is supplied to the suction side of the compressor 21, is compressed and is supplied to the first gas separation membrane unit 11.

[0035] The gas separation membrane module used in the present invention is preferably made of a hollow fiber membrane. In such a gas separation membrane module, in each manufacturing process of packing a bundle of hollow fiber membranes made of a large number of hollow fiber membranes or fixing the bundle of hollow fiber membranes with a tube sheet made of a thermosetting resin, contact occurs between the packed hollow fibers and / or deflection, deformation, yarn breakage, and the like of the hollow fibers themselves. Because of the complicated influence of such a difference in the state of the hollow fibers, the performance of the manufactured hollow fiber gas separation membrane module hardly varies, even if the same number of hollow fibers are manufactured in the same process.Therefore, it is preferable that the gas separation membrane modules used in the present invention be made of hollow fiber membranes, because gas separation membrane modules have excellent technical significance in this coefficient of variation of gas permeability and / or in the gas separation selectivity of the modules. Petition 870260061636, dated 06 / 23 / 2026, p. 23 / 82 / 56 of gas separation membrane is equal to or less than a certain value.

[0036] Furthermore, in the gas separation membrane module used in the present invention, a hollow fiber membrane made of a polymer and with an asymmetric structure can be suitably used as the gas separation membrane. The hollow fiber membrane with an asymmetric structure has a skin layer and a porous layer. The skin layer primarily assumes the task of gas separation and is thinner than the porous layer. The skin layer is a very dense layer compared to the porous layer, and is generally extremely thin, and preferably has a thickness of 1 nm or more and 5 µm or less, and more preferably 10 nm or more and 200 nm or less. The porous layer is a relatively thick porous layer that supports the skin layer, and preferably has a thickness of 10 µm or more and 2,000 µm or less, and more preferably 20 µm or more and 200 µm or less.The diameter of the pores in the porous layer is not particularly limited, but is generally 0.01 to 100 µm in many cases, and more preferably 0.01 to 50 µm. A hollow fiber membrane like this has a large effective surface area, high pressure resistance, and is excellent as a gas separation membrane.

[0037] Additionally, in the hollow fiber membrane made of a polymer and with an asymmetric structure, as described herein, it is necessary to control the matrix of the porous layer and the skin layer on the nm and pm scales, for example, the dry / wet phase inversion method described below, and additionally, since the skin layer that contributes to the gas separation performance is extremely thin, even if the production conditions are rigorously adjusted by the same production method, for example, differences in the presence or absence of fine defects in the skin layer, the thickness and shape of the skin layer, and the like occur at least for each production batch.

[0038] Furthermore, since the purity of the raw material of Petition 870260061636, dated 06 / 23 / 2026, page 24 / 82 / 56 Since the polymer, and / or the amount of impurities contained in the raw material, and the amount of moisture contained in the raw material are not always constant, various properties such as the viscosity of the polymer itself or the concentration of the polymer itself with respect to the solvent obtained by polymerization using these raw materials are hardly the same for each batch. Therefore, in a hollow fiber membrane with an asymmetrical structure manufactured using polymers with different properties for each batch, the above-described factors are intricately affected, and thus the gas separation characteristics will likely vary.Therefore, it is preferable that the gas separation membrane unit used in the present invention be made of gas separation membrane modules manufactured from hollow fiber membranes with an asymmetrical structure, by virtue of the gas separation membrane modules having excellent technical significance in defining the coefficient of variation of gas permeability and / or in the gas separation selectivity up to a certain value or less.

[0039] As a method of making the coefficient of variation of gas separation membrane modules equal to or less than a certain value, there is a method of minimizing variations in the gas separation selectivity and gas permeation performance of hollow fiber membranes and gas separation membrane modules to be manufactured. For example, as described herein, this can be achieved by controlling the purity and / or the amount of impurities in the polymer raw material used to manufacture the hollow fiber membranes to a certain degree, and / or by controlling the polymer polymerization conditions and the manufacturing conditions of the hollow fiber membranes and gas separation membrane modules in detail. Furthermore, a method of measuring the gas separation selectivity and gas permeability of the manufactured modules and selecting a combination in which the coefficient of variation is equal to or less than a certain value. Petition 870260061636, dated 06 / 23 / 2026, page 25 / 82 / 56, the value of the measured data is also available. By simultaneously performing these steps, the coefficient of variation of the gas separation membrane unit can be set at a certain value or less more efficiently.

[0040] The hollow fiber membrane preferably has an inner diameter of about 10 to 3,000 µm, and more preferably 30 to 500 µm. The outer diameter of the hollow fiber membrane is preferably about 30 to 7,000 µm, and more preferably 35 to 700 µm. The thickness of the skin layer and the porous layer, the inner and outer diameter of the hollow fiber membrane, and the hole diameter can be measured using an optical microscope or an electron microscope.

[0041] The gas separation membrane material that constitutes the gas separation membrane module of the present invention is not particularly limited, and examples thereof include polyimide, polyamide, polysulfone, polyether sulfone, polyamideimide, polyetherimide, and polycarbonate. Among these, the gas separation membrane is preferably made of polyimide from the point of view of durability, thermal resistance, separability, and the like.

[0042] When polyimide is used as the gas separation membrane, it can be obtained by dehydration and imidation using a tetracarboxylic acid component and a diamine component.

[0043] As the tetracarboxylic acid component, aliphatic tetracarboxylic acid dianhydride or aromatic tetracarboxylic acid dianhydride can be used. On the other hand, as the diamine component, aliphatic diamine or aromatic diamine can be used.

[0044] Examples of aliphatic tetracarboxylic acid dianhydrides include cyclobutane-1,2,3,4-tetracarboxylic acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride, dicyclohexyl-3,3',4,4'-tetracarboxylic acid dianhydride, 1,2,4,5-dianhydride 1,2,4,5-cyclohexane tetracarboxylic acid, 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, Petition 870260061636, dated 06 / 23 / 2026, page 26 / 82 / 56 bicyclo[2.2.2]oct-7-ene-2,3; 5,6- examples of the same include tetracarboxylic dianhydride.

[0045] Aromatic tetracarboxylic acid dianhydrides preferably have 2 to 3 aromatic rings, and examples thereof include tetracarboxylic acid 3,3',4,4'-biphenyldianhydride, 4,4'(hexafluoroisopropylidene)-bis(phthalic anhydride) (This compound is also referred to as 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride), tetracarboxylic acid 2,3,3',4'-biphenyldianhydride, 2,2', examples thereof include 3,3'-biphenyltetracarboxylic acid dianhydride, pyromellitic dianhydride, benzophenonetetracarboxylic acid dianhydride, 4,4'-oxyphthalic acid dianhydride, diphenylsulfonetetracarboxylic acid dianhydride, p-terphenyltetracarboxylic acid dianhydride, and m-terphenyltetracarboxylic acid dianhydride.

[0046] Examples of aliphatic diamines include trans-1,4-diaminocyclohexane, cis-1,4-diaminocyclohexane, 1,6-hexamethylenediamine, 1,10-decamethylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, and polyoxypropylenediamine with a weight-average molecular weight of 500 or less.

[0047] Examples of aromatic diamines include paraphenylenediamine, metaphenylenediamine, 4,4'-oxydianiline, 3,4'-oxydianiline, 4,4'-diaminodiphenylmethane, 2,4-toluenediamine, 3,3'-dihydroxy-4,4'-diaminobiphenyl, bis(4-amino-3-carboxyphenyl)methane, 2,4-diaminotoluene, and 3,5-diaminobenzoic acid, 3,7-diamino-2,8-dimethyldibenzothiophene=5,5-dioxide as the main component, the isomer 3,7-diamino-2,6-dimethyldibenzothiophene=5,5-dioxide with different positions of the methyl group, 3,7-diamino-4,6-dimethyldibenzothiophene=5,5-dioxide, 2,2',5,5'tetrachlorobenzidine, 3,3',5,5'-tetrachlorobenzidine, 3,3'-dichlorobenzidine, 2,2'dichlorobenzidine, 2,2', examples thereof include 3,3',5,5'hexachlorobenzidine, 2,2',5,5'-tetrabromobenzidine, 3,3',5,5'tetrabromobenzidine, 3,3'-dibromobenzidine, 2,2'-dibromobenzidine, Petition 870260061636, dated 06 / 23 / 2026, page 27 / 82 / 56 2,2',3,3',5,5'-hexachlorobenzidine, 3,3'-diaminodiphenylsulfone, 3,3'-diamino4,4'-dimethyl-diphenylsulfone, and 3,3'-diamino-4,4'-diethyl-diphenylsulfone.

[0048] In the present invention, when polyimide is used as the gas separation membrane material that constitutes the gas separation membrane module, aromatic polyimide can be used in particular. The aromatic polyimide can be obtained using an aromatic tetracarboxylic acid component and an aromatic diamine component. <Método para produzir membrana de separação de gás>

[0049] For example, as a preferred method for producing the gas separation membrane, there is a method for producing the gas separation membrane by a dry / wet phase inversion method using a polymer solution containing a polymer and a solvent.

[0050] As an aspect of the method for preparing a polymer solution used in the present invention, a method for preparing a polyimide solution will be described. The polyimide solution is preferably prepared by a two-stage method or a one-stage method. The two-stage method is carried out by adding a tetracarboxylic acid component and a diamine component to a polar organic solvent at a predetermined composition ratio to polymerize them at a low temperature approximately at room temperature to produce a polyamic acid, and then performing thermal imidation of the polyamic acid or adding pyridine or similar substances to the polyamic acid to chemically imidize the polyamic acid.The one-stage method is carried out by adding a tetracarboxylic acid component and a diamine component to a polar organic solvent at a predetermined composition ratio and polymerizing and imidizing them at a high temperature of about 100 to 250°C, preferably about 130 to 200°C. When the imidization reaction is carried out by heating, it is preferable to carry out the imidization reaction while still removing desorbed water or alcohol. Petition 870260061636, dated 06 / 23 / 2026, page 28 / 82 / 56

[0051] Examples of polar organic solvents include: phenolic solvents such as phenol, cresol and xylenol; catechols such as a catechol with two hydroxyl groups directly on a benzene ring, and resorcinol; halogenated phenols such as 3-chlorophenol, 4-chlorophenol (the same as parachlorophenol described below), 3-bromophenol, 4-bromophenol and 2-chloro-5-hydroxytoluene; amide solvents including amides such as N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, and N,N-diethylacetamide; and a mixed solvent thereof.

[0052] The polyimide solution obtained by imidization polymerization can be used directly for spinning, as described below. In addition, for example, the polyimide solution obtained can be placed in a polyimide-insoluble solvent to precipitate and isolate polyimide, and then dissolved again in a polar organic solvent to a predetermined concentration to prepare an aromatic polyimide solution, which can be used for spinning.

[0053] The hollow fiber membrane with the asymmetric structure can be adequately obtained by a dry / wet phase inversion method using a polymer solution. The dry / wet phase inversion method is a known method in which a polymer solution is contacted with a coagulating liquid to form a film while still undergoing phase transformation. The dry / wet phase inversion method is a phase transformation method in which a dense, thin layer is formed by evaporating a solvent on the surface of a polymer solution in the form of a film, then immersed in a coagulating liquid (a solvent that is compatible with the solvent of the polymer solution and in which the polymer is insoluble), and micropores are formed using a phase separation phenomenon generated at that moment to form a porous layer, and is proposed by Loeb et al. (e.g., US3133132A). Petition 870260061636, dated 06 / 23 / 2026, page 29 / 82 / 56

[0054] Examples of the polymer contained in the polymer solution include the various polymer materials listed here.

[0055] In the present invention, the solvent of the polymer solution used in the dry / wet phase inversion method preferably contains: a solvent capable of dissolving the polymer; and an aliphatic alcohol.

[0056] The solvent capable of dissolving the polymer is preferably a polar organic solvent, and may be the polar organic solvent used to synthesize a polymer by polymerization of a monomer. In one aspect of the present invention, when the polymer is polyimide, the polar organic solvent may be any solvent provided that it can dissolve the polyimide, and examples thereof include the polar organic solvent used in the preparation of the polyimide solution described above.

[0057] The aliphatic alcohol contained as the solvent of the polymer solution preferably has a boiling point of 60°C or higher. The aliphatic alcohol may be a monovalent aliphatic alcohol or a divalent or higher aliphatic polyhydric alcohol.

[0058] The aliphatic monohydric alcohol as the solvent for the polymer solution is preferably acyclic, and may be linear or branched, and, for example, has 1 to 7 carbon atoms. The aliphatic polyhydric alcohol as the solvent for the polymer solution is preferably acyclic, and may be linear or branched, and has carbon atoms, for example, preferably 2 to 10, and more preferably 3 to 8.

[0059] As an aspect of the present invention, a method for producing a hollow fiber membrane by a dry / wet phase inversion method using a polymer solution will be described below.

[0060] First, in the spinning stage (polymer solution discharge stage), the spinning nozzle used to discharge the polymer solution can be any nozzle as long as the polymer solution is extruded into the hollow filament body, and is suitably a tube-type nozzle in Petition 870260061636, dated 06 / 23 / 2026, p. 30 / 82 / 56 hole, or similar. In general, the temperature range of the polymer solution (preferably the polyimide solution) at the time of extrusion is, for example, preferably about 20°C to 150°C, and more preferably 30°C to 120°C, depending on the types of polymer and solvent contained in the polymer solution, viscosity, and the like. Furthermore, spinning is carried out during the supply of gas or liquid to the body of the extruded hollow fiber in the nozzle.

[0061] In the coagulation step continuing from the spinning step, the hollow fiber body discharged from the nozzle is again extruded into air or an inert gas atmosphere such as N2, then it is taken to a coagulation bath and immersed in the coagulation liquid. The coagulation liquid is preferably a liquid that does not substantially dissolve the polymer component and is compatible with the solvent of the polymer component. Although not particularly limited, water, lower alcohols such as methanol, ethanol, and propyl alcohol, ketones with a lower alkyl group such as acetone, diethyl ketone, and methyl ethyl ketone, or mixtures thereof are preferably used as the coagulation liquid. When the polymer solution is a polyimide solution and the solvent of the polyimide solution is an amide solvent, an aqueous solution of the amide solvent is also preferably used as the coagulation liquid.

[0062] The yarn obtained in the coagulation step is optionally washed with a washing solvent such as ethanol, and then an aliphatic hydrocarbon such as isopentane, n-hexane, isooctane, or n-heptane is applied to the yarn to replace the coagulation liquid and / or the washing solvent on the exterior and interior of the hollow fiber with the aliphatic hydrocarbon. Additionally, the hollow fiber is dried at 100 to 200°C to obtain the desired hollow fiber.

[0063] As described herein, in the present invention, in the case where the gas separation membrane that constitutes the membrane module of Petition 870260061636, dated 06 / 23 / 2026, page 31 / 82 / 56. Gas separation is a hollow fiber membrane with an asymmetrical structure made of a polymer. Since the gas separation membrane is obtained through a multi-step spinning process from a polymer solution as described herein, variations in the thickness and / or permeability of the skin layer during production, the shape of the hollow fiber membrane such as thickness and / or length, and the like, increase. Therefore, the technical significance of setting the coefficient of variation of gas permeability and / or gas separation selectivity of gas separation membrane modules to a certain value or less is excellent.

[0064] The present invention can be carried out by selecting the modules to be used so that the coefficient of variation remains below a predetermined value.

[0065] In the gas separation membrane unit of the present invention, a plurality of the gas separation membrane modules 40 described above are combined in parallel, and, in the unit, the coefficient of variation of gas permeability or gas separation selectivity among the plurality of gas separation membrane modules 40 is 0.01 or more and 0.49 or less. When the coefficient of variation among the gas separation membrane modules 40 is 0.49 or less, the recovery rate and purity of the product gas obtained can be increased.It is considered that the reason why the present invention can achieve the above-described effects is that the variation in the flow rate of the supply gas flowing to each module in the same unit can be suppressed, and the gas separation load in each module can be leveraged, whereby a state in which a very high or very low amount of gas flows to a part of the modules with respect to performance such as gas permeability and / or gas separation selectivity of the module can be avoided, and the original permeation performance can be exhibited. From the point of view of further improving the aforementioned effects, the coefficient of variation is preferably... Petition 870260061636, dated 06 / 23 / 2026, p. 32 / 82 / 56 0.45 or less, more preferably 0.40 or less, in particular preferably 0.35 or less, and even more preferably 0.30 or less.

[0066] Furthermore, the coefficient of variation is 0.01 or more, and more preferably 0.015 or more, from the point of view that the effect of improving the recovery rate or purity is not obtained even if the coefficient of variation is further reduced.

[0067] Once a critical point like this is found, it is possible to reduce the manufacturing cost that occurs when the gas separation membrane module is manufactured in exactly the same way down to a fine point. For example, conditions such as a change in temperature conditions in the wiring, and / or a change in conditions such as a solvent to be used, a change in the mode of a manufacturing apparatus to be used can be relaxed, and a minimal difference between batches can be tolerated, so that there is an advantage such as an improvement in yield.

[0068] It should be noted that, in this descriptive report, the expression “gas permeability or gas separation selectivity of the gas separation membrane module” refers to the gas permeability or gas separation selectivity of the gas separation membrane that constitutes the gas separation membrane module. Since there is a correlation between gas permeability and gas separation selectivity, the effect of the present invention can be achieved by defining the coefficient of variation for either gas permeability or gas separation selectivity.

[0069] For example, the coefficient of variation of gas permeability is a numerical value (S / AV) obtained by dividing the standard deviation value S by an average value AV obtained by measuring the gas permeability of each gas separation membrane module. Similarly, the coefficient of variation of gas separation selectivity is a numerical value (S / AV) Petition 870260061636, dated 06 / 23 / 2026, page 33 / 82 / 56 obtained by dividing the standard deviation value S by an average value AV obtained by measuring the gas separation selectivity of each gas separation membrane module.

[0070] Gas permeability is a gas permeation rate of high-permeability gas A. As described herein, the permeation rate, which is the permeation volume per unit membrane area, unit time, and unit partial pressure difference, can be represented by P' (unit: *10-5cm3(STP) / cm2-s-cmHg). The gas separation selectivity of the membrane can be expressed by (permeation rate of high-permeability gas A / permeation rate of low-permeability gas B).

[0071] For each module in the unit of the present invention, gas A is highly permeable and gas B is less permeable. Additionally, in the system of the present invention, each unit and each module that constitutes the unit are normally highly permeable to gas A and poorly permeable to gas B.

[0072] In the gas separation membrane unit of the present invention, both the gas permeability and the gas separation selectivity of the gas separation membrane module preferably satisfy the range of the coefficient of variation from the point of view of further enhancing the recovery rate and purity of the gas obtained.

[0073] In the present invention, it is preferable that the high-permeability gas A be CO2 (carbon dioxide) and the low-permeability gas B be CH4 (methane) or the high-permeability gas A be O2 (oxygen) and the low-permeability gas B be N2 (nitrogen) because the effect of adopting a predetermined coefficient of variation is high. In particular, it is preferable that the high-permeability gas A be CO2 and the low-permeability gas B be CH4 from the point of view of reducing the environmental impact by improving the recovery efficiency of CH4.

[0074] The gas separation selectivity (P'A / P'B) of each module Petition 870260061636, dated 06 / 23 / 2026, p. 34 / 82 / 56, regarding gas separation membranes at 40°C, is preferably 2 or more and 1,000 or less, more preferably 2.5 or more and 800 or less, even more preferably 3 or more and 500 or less.

[0075] In the case where the high permeability gas A is CO2 and the low permeability gas B is CH4, in order to obtain a high purity product gas (CH4) with a higher recovery rate more efficiently, the gas separation selectivity (P'CO2 / P'CH4) of each gas separation membrane module at 40°C is preferably 5 or more and 150 or less, more preferably 10 or more and 130 or less, even more preferably 15 or more and 120 or less, and in particular preferably 20 or more and 110 or less.

[0076] Also, in the case where the high permeability gas A is O2 and the low permeability gas B is N2, in order to obtain a high purity product gas with a higher recovery rate more efficiently, the gas separation selectivity (P'O2 / P'N2) of each gas separation membrane module at 40°C is preferably 2 or more and 10 or less, more preferably 3 or more and 9 or less, even more preferably 4 or more and 8 or less, and in particular preferably 4.5 or more and 7.5 or less.

[0077] In the present invention, in order to obtain high-purity product gas with a higher recovery rate more efficiently, the permeation rate P'A of gas A of each gas separation membrane module at 40°C is preferably 0.1x10⁻⁵ cm³(STP) / cm²,s*cmHg or more and 500x10⁵ cm³(STP) / cm²*s*cmHg or less, more preferably 0.5x10⁵ cm³(STP) / cm²*cmHg or more and 400x10⁻⁵ cm³(STP) / cm²*cmHg or less, even more preferably 0.8x10⁻⁵ cm³(STP) / cm²*s*cmHg or more and 350x10⁻⁵ cm³(STP) / cm²*s*cmHg or less, and in particular preferably 1x10-5cm3(STP) / cm2^cmHg or more and 300x10-5cm3(STP) / cm2^cmHg or less. Petition 870260061636, dated 06 / 23 / 2026, page 35 / 82 / 56

[0078] In the present invention, in order to obtain high-purity product gas with a higher recovery rate more efficiently, the permeation rate P'B of gas B from each gas separation membrane module at 40°C is preferably 0.01*10⁻⁵ cm³(STP) / cm²⁰cmHg or more and 15*10⁵ cm³(STP) / cm²⁰s⁰cmHg or less, more preferably 0.01*10⁵ cm³(STP) / cm²⁰s⁰cmHg or more and 10*10⁻⁵ cm³(STP) / cm²⁰cmHg or less, even more preferably 0.02*10⁻⁵ cm³(STP) / cm²⁰s⁰cmHg or more and 7*10⁻⁵ cm³(STP) / cm²⁰cmHg or less, and in particular preferably 0.02*10-5cm3(STP) / cm2^cmHg or more and 5*10-5cm3(STP) / cm2^cmHg or less.

[0079] In the present invention, in the case where the high-permeability gas A is CO2 and the low-permeability gas B is CH4, in order to obtain a high-purity product gas (CH4) with a higher recovery rate more efficiently, the permeation rate P'CO2 of CO2 of each gas separation membrane module at 40°C is preferably 1.5*10⁵ cm³(STP) / cm²^cmHg or more and 275*10⁻⁵ cm³(STP) / cm²^cmHg or less, more preferably 2*10⁻⁵ cm³(STP) / cm²^cmHg or more and 100*10⁻⁵ cm³(STP) / cm²^cmHg or less, even more preferably 3*10⁻⁵ cm³(STP) / cm²^cmHg or more and 90*10⁻⁵ cm³(STP) / cm²^cmHg or less, and in particular preferably 7*10-5cm3(STP) / cm2^cmHg or more and 80*10-5cm3(STP) / cm2· s · cmHg or less.

[0080] In the present invention, in the case where the high-permeability gas A is CO2 and the low-permeability gas B is CH4, in order to obtain high-purity CH4 with a higher recovery rate more efficiently, the permeation rate P'CH4 of CH4 of each gas separation membrane module at 40°C is preferably 0.03*10⁵ cm³(STP) / cm²^cmHg or more and 3*10⁻⁵ cm³(STP) / cm²^cmHg or less, more preferably 0.05*10⁻⁵ cm³(STP) / cm²^cmHg or more and 2.5*10⁵ cm³(STP) / cm²^cmHg or less, even more preferably 0.05*10⁻⁵ cm³(STP) / cm²^cmHg or more. Petition 870260061636, dated 06 / 23 / 2026, page 36 / 82 / 56 5 cm3(STP) / cm2-s-cmHg or more and 2.0 x 10-5 cm3(STP) / cm2-s-cmHg or less, and in particular preferably 0.08 x 10-5 cm3(STP) / cm2^cmHg or more and 1.5 x 10-5 cm3(STP) / cm2-s-cmHg or less.

[0081] In the present invention, in the case where the high-permeability gas A is O2 and the low-permeability gas B is N2, in order to obtain high-purity product gas (N2) with a higher recovery rate more efficiently, the permeation rate P'O2 of O2 of each gas separation membrane module at 40°C is preferably 0.1*10⁵ cm³(STP) / cm²*s*cmHg or more and 30*10⁻⁵ cm³(STP) / cm²*s*cmHg or less, more preferably 0.5*10⁻⁵ cm³(STP) / cm²*s*cmHg or more and 25*10⁻⁵ cm³(STP) / cm²*s*cmHg or less, even more preferably 0.8*10⁻⁵ cm³(STP) / cm²*s*cmHg or more and 20*10-5cm3(STP) / cm2-s-cmHg or less, and in particular preferably 1*10-5cm3(STP) / cm2^cmHg or more and 18*10-5cm3(STP) / cm2^cmHg or less.

[0082] In the present invention, in the case where the high-permeability gas A is O2 and the low-permeability gas B is N2, in order to obtain high-purity product gas (N2) with a higher recovery rate more efficiently, the permeation rate P'N2 of N2 of each gas separation membrane module at 40°C is preferably 0.03*10⁵ cm³(STP) / cm²*s*cmHg or more and 5*10⁻⁵ cm³(STP) / cm²*s*cmHg or less, more preferably 0.05*10⁻⁵ cm³(STP) / cm²*s*cmHg or more and 4*10⁵ cm³(STP) / cm²*s*cmHg or less, even more preferably 0.05*10⁵ cm³(STP) / cm²*cmHg or more and 3.5*10-5cm3(STP) / cm2^cmHg or less, and in particular preferably 0.08*10-5cm3(STP) / cm2,s*cmHg or more and 3*10-5cm3(STP) / cm2· s · cmHg or less.

[0083] In the present invention, the gas permeability in the gas separation membrane module can be measured, for example, by the following method. Although examples of the method are given below for CH4 and CO2, other gases can be measured in a similar manner. Petition 870260061636, dated 06 / 23 / 2026, page 37 / 82 / 56 (Method for measuring the gas permeability of CH4 and CO2)

[0084] The permeability of CH4 gas in a film is measured by measuring the flow rate of a gas that has passed through a film with a predetermined film area at a temperature of 40°C when a pure CH4 gas is pressurized to a predetermined pressure using a thin-film flowmeter. The gas permeability P'CH4 (unit: x105cm3(STP) / cm2*s*cmHg) to CH4 membranes is calculated from the pressure, membrane area, and permeate gas flow rate.

[0085] The gas permeability of the CO2 membrane is measured by measuring the flow rate of gas that has passed through the membrane with a predetermined membrane area at a temperature of 40°C when pure CO2 gas is pressurized to a predetermined pressure. The gas permeability P'CO2 (unit: x10-5cm3(STP) / cm2-s-cmHg) to the CO2 membrane is calculated from the pressure, membrane area and flow rate of permeated gas.

[0086] During the gas separation operation including CH4 and CO2, the gas flow rates at the gas inlet, permeate gas outlet, and non-permeate gas outlet of each module in the same unit and the concentrations of CH4 and CO2 in the gas can be measured, and the CO2 permeability and gas separation selectivity (P'CO2 / P'CH4) of each module can be calculated from the results using a known flow model. For example, it can be calculated by Expressions (1) to (20) described in THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, VOLUME 90, 2011, p 1253-1268. As the inner diameter and outer diameter of the hollow fiber used for the calculation, for example, the inner diameter and outer diameter of any five hollow fiber membranes of the module are measured by a measuring microscope, and the average value thereof can be used. The inner diameter can be, for example, 50 to 800 μm, and the outer diameter can be, for example, 100 to 1,000 μm.

[0087] Exceptionally, the coefficient of variation during Petition 870260061636, dated 06 / 23 / 2026, p. 38 / 82 / 56: Gas separation including CH4 and CO2 can be measured by a combination of N2 and O2, provided the temperatures are the same. For example, before the CO2 / CH4 separation operation, the module is removed, compressed air is supplied to separate into an O2-enriched gas and an N2-enriched gas, the gas flow rates at the gas inlet, permeate gas outlet and non-permeate gas outlet, and the N2 and O2 concentrations in the gas are measured, and the gas permeability and gas separation selectivity are recalculated from the results using a general formula such as a backflow model.

[0088] In this case, the coefficient of variation of the permeation rate of O2 gas can be considered the coefficient of variation of the permeation rate of CO2, and the coefficient of variation of the gas separation selectivity (P'O2 / P'N2) at 40°C can be considered the coefficient of variation of the gas separation selectivity (P'CO2 / P'CH4) at the same temperature.

[0089] When the coefficient of variation of the gas separation membrane unit falls within the range of 0.01 to 0.49 in any of the plurality of methods, the coefficient of variation among the unit modules falls within a specific range.

[0090] The number of gas separation membrane modules in the gas separation membrane unit of the present invention is preferably 2 to 100, and more preferably 4 to 70. The gas separation membrane module preferably has a membrane area of ​​0.1 to 700 m2, and more preferably 1 to 500 m2. Additionally, the length of the gas separation membrane module is preferably 0.1 to 4 m, and more preferably 0.2 to 3 m. When the gas separation membrane module comprises a hollow fiber membrane, the preferred length of the hollow fiber membrane is also the same as the preferred length of the module.

[0091] Next, the gas separation system of the present Petition 870260061636, dated 06 / 23 / 2026, p. 39 / 82 / 56, the invention will be further described.

[0092] Returning to Fig. 1, as shown in Fig. 1, the first gas separation membrane unit 11 and the second gas separation membrane unit 12 are connected in series. Specifically, the first gas separation membrane unit 11 and the second gas separation membrane unit 12 are connected by connecting the non-permeated gas outlet 11b of the first gas separation membrane unit 11 and the gas inlet 12a of the second gas separation membrane unit 12 via the first line 14.

[0093] The respective gas inlets, outlets, supplied gas, permeate gas, and non-permeate gas of the first gas separation membrane unit 11 and the second gas separation membrane unit 12 can be described using the terms first and second, respectively. The same applies to the configuration related to the third gas separation membrane unit 13 described later. Additionally, the upstream and downstream described below are based on the flow direction of the feedstock gas mixture.

[0094] A raw material gas mixture supply line 26 to supply a raw material gas mixture from a raw material gas mixture source (not shown) to the first gas separation membrane unit 11 is connected to the first gas inlet 11a of the first gas separation membrane unit 11. A compression means 21 is disposed in the middle of the raw material gas mixture supply line 26.

[0095] The permeate gas outlet 12c of the second gas separation membrane unit 12 is connected to the raw material gas mixing supply line 26 by a second line 17. Specifically, the second line 17 is connected to the second permeate gas outlet 12c and to the raw material gas mixing supply line 26 at the position on the suction side of the compression medium 21. Petition 870260061636, dated 06 / 23 / 2026, pages 40 / 82 / 56

[0096] Compression medium 21 is installed for the purpose of pressurizing the raw material gas mixture supplied from the raw material gas source mixture. Additionally, compression medium 21 is installed to pressurize the second permeate gas when the second permeate gas discharged from the second gas separation membrane unit 12 is returned to the first gas separation membrane unit 11 via the second line 17. A compressor may be used as compression medium 21.

[0097] A recovery line 15 for removing non-permeated gas to which concentrated and enriched gas B is connected to the non-permeated gas outlet 12b of the second gas separation membrane unit 12.

[0098] The operation of the gas separation system 10 of the present embodiment with the above-described configuration will be described. The feedstock gas mixture including gas A and gas B to be separated is supplied to the first gas separation membrane unit 11 from the feedstock gas mixture source (not shown) via the feedstock gas mixture supply line 26. The feedstock gas mixture is pressurized by the compression means 21 to increase the pressure of the feedstock gas mixture.

[0099] When the pressurized feedstock gas mixture 21 is supplied to the first gas separation membrane unit 11, the feedstock gas mixture is separated into a first permeate gas, which is a gas that has permeated the gas separation membrane, and a first non-permeate gas, which is a gas that has not permeated the gas separation membrane, due to a difference in the permeation rate with respect to the gas separation membrane.

[00100] The first non-permeated gas discharged from the first gas separation membrane unit 11 is a gas in which gas B is concentrated compared to the feedstock gas mixture. The first Petition 870260061636, dated 06 / 23 / 2026, page 41 / 82 / 56 non-permeated gas is discharged from the non-permeated gas outlet 11b of the first gas separation membrane unit 11, and is supplied to the second gas separation membrane unit 12 through the first line 14.

[00101] On the other hand, in the first permeate gas discharged from the first gas separation membrane unit 11, gas A is concentrated compared to the feedstock gas mixture. The first permeate gas is removed from the system via the third line 18.

[00102] The first non-permeated gas discharged from the first gas separation membrane unit 11 is supplied to the second gas separation membrane unit 12, comes into contact with the gas separation membrane of the second gas separation membrane unit 12, and is separated into the second permeated gas and the second non-permeated gas by the gas separation membrane of the second gas separation membrane unit 12. In the second non-permeated gas discharged from the second gas separation membrane unit 12, gas B is further concentrated and enriched. The second non-permeated gas is removed from the system from the second non-permeated gas outlet 12b of unit 12 via the recovery line 15 as the gas enriched with gas B.

[00103] On the other hand, the second permeate gas is discharged from the second permeate gas outlet 12c of the second gas separation membrane unit 12, and is returned to the raw material gas mixing supply line 26 on the suction side of the compression medium 21 via the second line 17 connected to outlet 12c.

[00104] The second permeate gas discharged from the second gas separation membrane unit 12 and returned via the second line 17 is mixed with the feedstock gas mixture, and then pressurized by the compression medium 21.

[00105] In the present embodiment, the gas separation membrane unit of the present invention is used as one or both of the first unit. Petition 870260061636, dated 06 / 23 / 2026, pp. 42 / 82 / 56 of gas separation membrane 11 and the second gas separation membrane unit. As a result, excellent purity and recovery rate can be obtained. In the present invention, as an advantage of using the unit with a specific coefficient of variation in the system in which the product gas is withdrawn as the second non-permeated gas in two or more stages, it is possible to suppress the amplification of the variation in the flow rate of the supply gas flowing to each module due to the formation of a plurality of units. From the point of view of particularly intensifying the effect, both of the first gas separation membrane unit 11 and the second gas separation membrane unit 12 on the first gas separation membrane unit 11 and the second gas separation membrane unit 12, the gas separation membrane unit of the present invention is preferably used.Furthermore, for example, in the first gas separation membrane unit 11 and in the second gas separation membrane unit 12, the coefficients of variation of gas separation selectivity or gas permeability may be the same or different.

[00106] Next, a gas separation system 10' will be described according to a second embodiment of the present invention with reference to Fig. 4. In the description of the second embodiment, components similar to those of the first embodiment are denoted by the same reference numbers, description of the same is omitted, and differences from the first embodiment will be mainly described.

[00107] In the gas separation system 10' shown in Fig. 4, a first gas separation membrane unit 11 and a third gas separation membrane unit 13 are connected in series. Specifically, the first gas separation membrane unit 11 and the third gas separation membrane unit 13 are connected by connecting the permeate gas outlet 11c of the first gas separation membrane unit 11 and the gas inlet 13a of the third membrane unit. Petition 870260061636, dated 06 / 23 / 2026, page 43 / 82 / 56 of gas separation 13 by the third line 18. As the gas separation membrane module that constitutes the third gas separation membrane unit 13, the same modules of the first gas separation membrane unit 11 and the second gas separation membrane unit 12 can be employed.

[00108] In the third gas separation membrane unit 13, the non-permeated gas outlet 13b is connected to the raw material gas mixture supply line 26 by a fourth line 41. In the embodiment of Fig. 3, the fourth line 41 is connected to the raw material gas mixture supply line 26 in the position on the suction side of the compression medium 21. In the example of Fig. 3, the third permeated gas discharge line 19 is connected to the permeated gas outlet 13c of the third gas separation membrane unit 13.

[00109] Compression medium 21 is installed for the purpose of pressurizing the raw material gas mixture supplied from the gas source, the second permeate gas returned from the second gas separation membrane unit 12, and the third non-permeate gas returned from the third gas separation membrane unit 13.

[00110] A gas path during operation for gas separation in the gas separation system 10' of the present embodiment with the above configuration will be described with reference to Fig. 3. The feedstock gas mixture to be separated is supplied from the mixed gas source (not shown) to the first gas separation membrane unit 11 via the feedstock gas mixture supply line 26. Before supply, the feedstock gas mixture is pressurized by the compression means 21 to increase the pressure of the feedstock gas mixture.

[00111] As in the first embodiment, when the pressurized raw material gas mixture by the compression medium 21 is supplied to the first gas separation membrane unit 11, the raw material gas mixture Petition 870260061636, dated 06 / 23 / 2026, p. 44 / 82 / 56, is separated into the first permeate gas and the first non-permeate gas. The first permeate gas discharged from the first gas separation membrane unit 11 is supplied to the third gas separation membrane unit 13 via the third line 18. The first permeate gas introduced into the third gas separation membrane unit 13 is separated into a third permeate gas and a third non-permeate gas by unit 13. In the third permeate gas, gas A is additionally concentrated and enriched compared to the first permeate gas introduced into the third gas separation membrane unit 13, and is removed from the system by the permeate gas outlet 13c of unit 13 via the third permeate gas discharge line 19.On the other hand, the third non-permeated gas is discharged from the non-permeated gas outlet 13b of the third gas separation membrane unit 13, and is returned to the feedstock gas mixture supply line 26 on the suction side of the compression medium 21 via the fourth line 41 connected to the outlet 13b. The third non-permeated gas returned through line 41 is mixed with the feedstock gas mixture and then pressurized by the compression medium 21.

[00112] The third line 18 may or may not be provided with a second compression means to pressurize and deliver the first permeate gas to the third gas separation membrane unit.

[00113] In the embodiments shown in Figs. 1 and 4, the pressure of the compression medium 21 is generally preferably 0.2 MPaG or more and 3.0 MPaG or less, and more preferably 0.3 MPaG or more and 2.4 MPaG or less, as the pressure of the gas supplied to the first gas separation membrane unit 11.

[00114] The pressure of the gas supplied to the third gas separation membrane unit 13 is preferably 0.05 MPaG or more and 1.2 MPaG or less, and more preferably 0.1 MPaG or more and 1.0 MPaG or less.

[00115] A preferred temperature range of Petition 870260061636, dated 06 / 23 / 2026, p. 45 / 82 / 56 operation (temperature of the gas separation membrane during operation) of each of the separation membrane units 11, 12 and 13 is preferably 0 to 80°C, more preferably 5 to 60°C, and even more preferably 10 to 50°C.

[00116] In the embodiment of Fig. 4, the unit of the present invention is used in any one or more, two or more, or all three of the first gas separation membrane unit 11 to the third gas separation membrane unit 13. As a result, excellent purity and recovery rate can be obtained. From the point of view of particularly intensifying the effect, two or more of the first gas separation membrane unit 11 to the third gas separation membrane unit 13 are preferably the gas separation membrane unit of the present invention, and, more preferably, all three of the first gas separation membrane unit 11 to the third gas separation membrane unit 13 are the gas separation membrane unit of the present invention.

[00117] The feedstock gas mixture used in the present invention is preferably a gas containing at least CO2 and CH4, since the effect of making the coefficient of variation in the present invention equal to or less than a specific value is excellent. Examples of feedstock gas mixtures include biogas, landfill gas, and natural gas. Biogas is a gas generated when a biomass feedstock is brought into contact with a microorganism under anaerobic conditions to carry out a fermentation treatment such as CH4 fermentation by the microorganism. Examples of biomass feedstock include organic substances such as food waste, agricultural waste, sewage sludge, and animal waste. Landfill gas is a gas generated by microbial or similar decomposition of organic substances in a landfill. Typically, biogas and landfill waste mainly include CO2 and CH4. Petition 870260061636, dated 06 / 23 / 2026, pp. 46 / 82 / 56

[00118] In the present invention, when the feedstock gas mixture contains CH4, the feedstock gas mixture preferably contains CH4 in an amount of 30 mol% or more, in particular preferably 40 to 95 mol%. When the feedstock gas mixture in the present invention contains CO2, the feedstock gas mixture preferably contains 3 to 70 mol% of CO2 from the point of view of high technical significance of the gas separation system of the present invention, and in particular preferably contains 5 to 60 mol% of CO2.

[00119] The feedstock gas mixture used in the present invention is preferably a gas containing at least N2 and O2. When the feedstock gas mixture contains N2, the feedstock gas mixture preferably contains N2 in an amount of 1 mol% or more, in particular preferably 5 to 95 mol%. When the feedstock gas mixture in the present invention contains O2, the feedstock gas mixture preferably contains 0.1 to 50 mol% of O2 from the point of view of high technical significance of the gas separation system of the present invention, and in particular preferably contains 0.5 to 30 mol% of O2.

[00120] Although the present invention has been described based on preferred embodiments thereof, the present invention is not limited to those embodiments. For example, in addition to the compression means in the embodiment described above, a decompression means may be provided on either one or both permeation sides of each gas separation membrane unit to apply power to the mixed gas supplied to each gas separation membrane unit to pass through the separation membrane. As such a compression means, a known vacuum pump or the like may be used. Also, the gas separation system of the present invention is not limited to the embodiments of Figs. 1 and 4, and may have only one gas separation membrane unit as described in Fig. 5. The embodiment of Fig. 5 is configured so that the permeated gas is removed from the system at Petition 870260061636, dated 06 / 23 / 2026, p. 47 / 82 / 56 from the first permeate gas discharge line, but the permeate gas from the first permeate gas discharge line can be refluxed to the raw material gas mixture supply line 26. EXAMPLES

[00121] The present invention will now be described in more detail with reference to the Examples. However, the scope of the present invention is not limited by these examples.

[00122] This test is a model experiment to show variations in gas separation selectivity and gas permeability, and was obtained by simulation according to the method described above using the model described in THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING., VOLUME 90, 2011, p 1253-1268.

[00123] The ratio of gas permeability to gas separation selectivity of the gas separation membrane module described below is a ratio of values ​​at 40°C. In each of the gas separation membrane modules used in the Examples and Comparative Examples, the membrane area was 95 m2, and all module lengths were equal. <Módulo de membrana de separação de gás>

[00124] Table 1 shows the gas separation characteristics at 40°C of gas separation membrane modules A and B used as a reference in the Examples and Comparative Examples. A gas separation membrane made of an aromatic polyimide hollow fiber membrane to be housed in an enclosure was considered gas separation membrane module A. The units P'CO2 and P'CH4 in Table 1 are x105cm3(STP) / cm2· s · cmHg. [Table 1]________________________________________________________________ P'CO2 P'CH4 gas separation membrane module P'CO2 / P'CH4 Membrane area per module m2 A 9.9 0.18 55 95 B 5.0 0.18 28 95 Comparative Examples 1 to 5 and Examples 1 to 11 Petition 870260061636, dated 06 / 23 / 2026, pp. 48 / 82 / 56

[00125] Each of the first gas separation membrane unit 11 and the second gas separation membrane unit 12 had a configuration in which four gas separation membrane modules were combined in parallel. The gas permeability at 40°C (CO2 permeation rate (P'CO2)) of each gas separation membrane module shown in Table 2 was the relative value with respect to the gas permeability at the same temperature (CO2 permeation rate) of the reference gas separation membrane module A. The gas separation selectivity (P'CO2 / P'CH4) shown in Table 2 is a value obtained by dividing the average value of the gas separation selectivity (P'CO2 / P'CH4) at 40°C of the four gas separation membrane modules by the gas separation selectivity (P'CO2 / P'CH4) at 40°C of gas separation membrane module A.

[00126] The first gas separation membrane unit 11 and the second gas separation membrane unit 12 were configured in the system of Fig. 1, and a simulation was performed operating the system under the following various conditions and the conditions of Table 2. The flow rate of the feedstock gas mixture described below is the flow rate of the feedstock gas mixture flowing into the system. The operating pressure is the pressure of the gas flowing into the first gas separation membrane unit 11. The operating temperature is the temperature of the gas separation membrane in each gas separation membrane unit. The CO2 concentration and CH4 recovery rate in the product gas are shown in Table 2. (Conditions)

[00127] 'Flow rate (F0) of the raw material gas mixture flowing into the system: 320 Nm3 / h

[00128] 'Composition of the Mixture Gas Matter: 40 mol% CO2, 60 mol% CH4:

[00129] 'Pressure of gas flowing to the first gas separation membrane unit 11 (operating pressure): 1.0 MPaG Petition 870260061636, dated 06 / 23 / 2026, pages 49 / 82 / 56

[00130] -Operating temperature of the first gas separation membrane unit 11: 400C

[00131] -Operating temperature of the second gas separation membrane unit 12: 40C [Table 2] Petition 870260061636, dated 06 / 23 / 2026, pages 50 / 82 / 56 Product gas CH4 recovery rate X© φχ 92.0 92.0 92.1 92.1 92.1 92.0 92.0 92.0 1 92.1 92.1 92.1 92.1 92.1 92.1 92.1 92.1 92.1 CO2 concentration mol% 4.20 3.96 3.65 3.55 3.55 4.38 4.08 3.57 3.24 3.20 3.12 3.07 3.03 2.98 2.92 2.87 2.87 2.87 CO2 concentration Second permeated gas mol% £ £ £ 0 00 5 5 5 5 First non-permeated gas First gas permeate mol% 0 os os os os OS OS OS OS OS OS First gas supply mol% $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ First gas supply mol% 0 0 0 0 0 0 0 0 Flow rate Second gas supply sz 219 219 219 219 219 219 218 216 214 214 213 213 213 212 212 212 212 212 First gas supply Nm3 / h 355 £ 356 £ 356 354 354 $ 351 £ £ £ £ 0 0 0 0 350 Gas permeability 2) Second gas separation membrane unit Coefficient of variation 0SO 0.40 0.20 0.01 00I 0.61 0SO 0.40 0.30 0.28 0.25 0.22 0.20 0.17 0.11 0.02 0.01 00I Total 4.00 4.00 \ 4.00 \ 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 Fourth module 1.50 1.40 1.20 1.02 1.00 1.00 1.50 1.40 1.30 1.125 1.25 1.20 0.90 1 1.05 1.01 1.01 1.00 Third module 1.50 1 1.40 1 1.20 1 1 1.01 1 1.00 0.50 0.50 1 09'0 0.70 1 0.875 1 1 sro | 06'0 0.80 1 0.90 1 1 S6'0 0.99 1 1.00 1 1.00 Second module 0.50 09'0 0.80 \ 1.00 1.00 0.50 0.50 09'0 0.70 0.875 sro 06'0 0.80 0.90 S6'0 0.99 1.00 1.00 First module 0SO 1 09Ό 0.80 1 1 66Ό 1.00 0SO 0SO 1 09Ό 0.70 1 0.625 1 1 sro 0.70 | 0.80 1 0.90 1 0.85 1 0.97 1 0.99 1 1.00 First gas separation membrane unit Coefficient of variation 0.61 0.61 0.61 0.61 0.61 0SO 0.40 1 0.30 1 0.28 1 0.25 0.22 | 0.20 1 0.17 0.11 0.02 1 0.01 00I Total 4.00 4.00 \ 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 Fourth module 2.00 2.00 2.00 1 2.00 1 2.00 2.00 1.50 1.40 1.30 1.375 1 1.25 1.20 1.20 1.30 1.15 1.03 1.02 1.00 Third module 1.00 00'1 1.00 1.00 1.00 1.00 1.50 1.40 1.30 1.125 1.25 1.20 0.90 1 1.05 1.01 1.01 1.00 Second module 0.50 0.50 0.50 0.50 0.50 0.50 0.50 09'0 0.60 0.875 sro 06'0 0.80 0.90 S6'0 0.99 1.00 1.00 First module 0.50 0.50 0.50 0.50 0.50 0.50 0.50 09'0 0.70 0.625 sro 0.70 0.80 0.90 0.85 0.97 0.99 1.00 Gas separation selectivity 1) Second gas separation membrane unit 1.00 1 m 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 First gas separation membrane unit 1.00 1 m 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 Com. Ex. 1 1 1 Ex. 2 Ex. 3 Com. Ex. 2 Com. Ex. 3 Com. Ex. 4 1 Ex. 4 1 Ex. 5 1 Ex. 6 Ex. 7 1 Ex. 8 1 Ex. 9 1 Ex. 10 1 Ex. 11 1 Ex. 12 1 Ex. 13 Com. Ex. 5. the -osoo -oso σ3 6Ó fro o the Petition 870260061636, dated 06 / 23 / 2026, pages 51 / 82 / 56

[00132] As can be seen by comparison with Examples and Comparative Examples 1, 3 and 4 shown in Table 2, when the coefficient of variation of gas permeability between the modules of the first gas separation membrane unit 11 or the second gas separation membrane unit 12 is 0.49 or less, the CO2 concentration in the product is less than 4.0 mol%, which means that the purity can be effectively improved.

[00133] Furthermore, as can be seen from the comparison between Example 3 and Comparative Example 2 and the comparison between Example 13 and Comparative Example 5, when the coefficient of variation decreases to 0.01, the CO2 concentration does not change and the CH4 recovery rate does not increase even if the coefficient of variation decreases further.

[00134] Therefore, by setting the coefficient of variation to 0.01 or more, the uniformity of manufacturing conditions can be improved compared to Comparative Examples 2 and 5, and the manufacturing cost can be reduced. Comparative Examples 6 and 7 and Examples 14 and 15

[00135] Each of the first gas separation membrane unit 11 and the second gas separation membrane unit 12 was configured by combining four gas separation membrane modules in parallel. The gas separation selectivity (P'CO2 / P'CH4) of the four gas separation membrane modules were the relative values ​​shown in Table 3 with respect to the reference gas separation membrane module A. The gas permeability (CO2 permeation rate) shown in Table 3 is a value obtained by dividing the average gas permeability (CO2 permeation rate) at 40°C of the four gas separation membrane modules by the gas permeability (CO2 permeation rate) at 40°C of gas separation membrane module A. Petition 870260061636, dated 06 / 23 / 2026, pages 52 / 82 / 56

[00136] The first gas separation membrane unit 11 and the second gas separation membrane unit 12 were configured in the system of Fig. 1, and a simulation was performed operating the system under the conditions of Table 3. The CO2 concentration and the CH4 recovery rate in the product gas are shown in Table 3. [Table 3] Petition 870260061636, dated 06 / 23 / 2026, page 53 / 82 / 56 Petition 870260061636, dated 06 / 23 / 2026, pages 54 / 82 / 56 Comparative Examples 8 and 9 and Example 16

[00137] Each of the first gas separation membrane unit 11, the second gas separation membrane unit 12, and the third gas separation membrane unit was configured by combining four gas separation membrane modules in parallel. The gas permeability (CO2 permeation rate) of the four gas separation membrane modules at 40°C was a relative value shown in Table 4 with respect to the 40°C value of the reference gas separation membrane module A. The gas separation selectivity (P'CO2 / P'CH4) shown in Table 4 is a value obtained by dividing the average value of the values ​​of the four gas separation membrane modules at 40°C by the gas separation selectivity (P'CO2 / P'CH4) of gas separation membrane module A at 40°C.

[00138] The first gas separation membrane unit 11, the second gas separation membrane unit 12, and the third gas separation membrane unit were configured in the system of Fig. 4, and a simulation was performed operating the system under the conditions of Table 4. The CO2 concentration and CH4 recovery in the product gas are shown in Table 4. (Conditions)

[00139] 'Flow rate (F0) of raw material gas mixture flowing into the system: 320 Nm3 / h

[00140] 'Gas composition of the mixture of matter: 40 mol% CO2, mol% CH4

[00141] 'Pressure of gas flowing to the first gas separation membrane unit 11 (operating pressure): 1.26 MPaG

[00142] 'Pressure of gas flowing to the third gas separation membrane unit 13 (operating pressure): 0.20 MPaG

[00143] 'Operating temperature of the first membrane unit Petition 870260061636, dated 06 / 23 / 2026, pages 55 / 82 / 56, regarding gas separation 11:40C

[00144] •Operating temperature of the second membrane unit gas separation 12: 40C

[00145] •Operating temperature of the third membrane unit gas separation 13: 40C [Table 4] Petition 870260061636, dated 06 / 23 / 2026, page 56 / 82 / 56 Petition 870260061636, dated 06 / 23 / 2026, page 57 / 82 / 56 Comparative Examples 10 and 11 and Example 17

[00146] In each of the first gas separation membrane unit 11, the second gas separation membrane unit 12, and the third gas separation membrane unit, the gas separation selectivity (P'CO2 / P'CH4) of the four gas separation membrane modules at 40°C was the ratio shown in Table 5 with respect to the 40°C value of the reference gas separation membrane module A. The gas permeability (CO2 permeation rate) shown in Table 5 is the ratio of the average value of the four gas separation membrane modules at 40°C to the value of the reference gas separation membrane module A at 40°C.

[00147] The first gas separation membrane unit 11, the second gas separation membrane unit 12, and the third gas separation membrane unit were configured in the system of Fig. 4, and a simulation was performed operating the system under the following conditions and under the conditions of Table 5. The CO2 concentration and CH4 recovery in the product gas are shown in Table 5. (Conditions)

[00148] 'Flow rate (F0) of raw material gas mixture flowing into the system: 320 Nm3 / h

[00149] 'Gas composition of the mixture of matter: 40 mol% CO2, mol% CH4

[00150] 'Pressure of gas flowing to the first gas separation membrane unit 11 (operating pressure): 1.26 MPaG

[00151] 'Pressure of gas flowing to the third gas separation membrane unit 13 (operating pressure): 0.20 MPaG

[00152] 'Operating temperature of the first gas separation membrane unit 11: 40C

[00153] 'Operating temperature of the second membrane unit Petition 870260061636, dated 06 / 23 / 2026, pp. 58 / 82 / 56, regarding gas separation 12:40C

[00154] -Operating temperature of the third gas separation membrane unit 13: 40C [Table 5] Petition 870260061636, dated 06 / 23 / 2026, pp. 59 / 82 / 56 Gas Permeability 2) | Third gas separation membrane unit | Coefficient of variation 0.50 0.01 | 0.00 Total 1.00 1.00 1.00 Fourth module 1.50 1.00 Third module 1.50 1.01 1.00 Second module 0.50 1.00 1.00 First module 0.50 0.99 1.00 Second gas separation membrane unit Coefficient of variation 0.00 0.00 0.00 Total 1.00 1.00 Fourth module 1.00 1.00 | 1.00 Third module 1.00 1.00 1.00 Second module 1.00 1.00 | 1.00 First module 1.00 1.00 | 1.00 First gas separation membrane unit | Coefficient of variation 0.00 | 00'0 0.00 Total 1.00 1.00 1.00 Fourth module 1.00 1.00 | 1.00 Third module 1.00 1.00 1.00 Second module 1.00 1.00 1.00 First module 1.00 1.00 1.00 Ex. Comp. 10 I Ex. 171 Ex. Comp. 11 Petition 870260061636, dated 06 / 23 / 2026, pages 60 / 82 / 56 Comparative Examples 12 and 13 and Example 18

[00155] Each of the first gas separation membrane unit 11 and the second gas separation membrane unit 12 had a configuration in which four gas separation membrane modules were combined in parallel. The gas permeability at 40°C (CO2 permeation rate (P'CO2)) of each gas separation membrane module shown in Table 2 was the relative value with respect to the gas permeability at the same temperature (CO2 permeation rate) of the reference gas separation membrane module B. The gas separation selectivity (P'CO2 / P'CH4) shown in Table 6 is a value obtained by dividing the average value of the gas separation selectivity (P'CO2 / P'CH4) at 40°C of the four gas separation membrane modules by the gas separation selectivity (P'CO2 / P'CH4) at 40°C of gas separation membrane module B.

[00156] The first gas separation membrane unit 11 and the second gas separation membrane unit 12 were configured in the system of Fig. 1, and a simulation was performed operating the system under the following various conditions and the conditions of Table 2. The flow rate of the feedstock gas mixture described below is the flow rate of the feedstock gas mixture flowing into the system. The operating pressure is the pressure of the gas flowing into the first gas separation membrane unit 11. The operating temperature is the temperature of the gas separation membrane in each gas separation membrane unit. The CO2 concentration and the CH4 recovery rate in the product gas are shown in Table 6. (Conditions)

[00157] -Flow rate (F0) of raw material gas mixture flowing into the system: 320 Nm3 / h

[00158] -Gas composition of the mixture of matter: 40 mol% CO2, mol% CH4:

[00159] -Pressure of the gas flowing into the first unit of Petition 870260061636, dated 06 / 23 / 2026, page 61 / 82 / 56 gas separation membrane 11 (operating pressure): 1.0 MPaG

[00160] -Operating temperature of the first gas separation membrane unit 11: 400C

[00161] -Operating temperature of the second gas separation membrane unit 12: 40C [Table 6] Petition 870260061636, dated 06 / 23 / 2026, pages 62 / 82 / 56 Petition 870260061636, dated 06 / 23 / 2026, pp. 63 / 82 / 56

[00162] As can be seen by comparison with Example 18 and Comparative Example 12 shown in Table 6, when the coefficient of variation of gas permeability between the modules of the first gas separation membrane unit 11 or the second gas separation membrane unit 12 is 0.49 or less, the CO2 concentration in the product is significantly reduced, which means that purity can be effectively improved.

[00163] Furthermore, as can be seen from the comparison between Example 18 and Comparative Example 13, when the coefficient of variation decreases to 0.01, the CO2 concentration does not change and the CH4 recovery rate does not increase, even if the coefficient of variation decreases further.

[00164] Therefore, by setting the coefficient of variation to 0.01 or more, the uniformity of manufacturing conditions can be improved compared to Comparative Example 13, and the manufacturing cost can be reduced. <Módulo de membrana de separação de gás>

[00165] Table 7 shows the gas separation characteristics at 40°C of the gas separation membrane module C used as a reference in the Examples and Comparative Examples. A gas separation membrane made of an aromatic polyimide hollow fiber membrane to be housed in a case was considered the gas separation membrane module A. The units P'O2 and P'N2 in Table 1 are x105cm3(STP) / cm2· s · cmHg. [Table 7]___________________________________________________________ P'O2 P'N2 gas separation membrane module. Membrane area per module (m2): C 2.2 0.33 6.6 95 Comparative Examples 14 and 15 and Example 19

[00166] The first gas separation membrane unit 11 had a configuration in which four gas separation membrane modules Petition 870260061636, dated 06 / 23 / 2026, page 64 / 82 / 56 were combined in parallel. The gas permeability at 40°C (O2 permeation rate (PO2)) of each gas separation membrane module shown in Table 8 was the relative value with respect to the gas permeability at the same temperature (O2 permeation rate) of the reference gas separation membrane module C. The gas separation selectivity (P'O2 / P'N2) shown in Table 8 is a value obtained by dividing the average value of the gas separation selectivity (PO2 / PN2) at 40°C of the four gas separation membrane modules by the gas separation selectivity (P'O2 / P'N2) at 40°C of gas separation membrane module C.

[00167] The first gas separation membrane unit 11 was configured in the system of Fig. 5, and a simulation was performed operating the system under the following various conditions and the conditions of Table 8. The flow rate of the feedstock gas mixture described below is the flow rate of the feedstock gas mixture flowing into the system. The operating pressure is the pressure of the gas flowing into the first gas separation membrane unit 11. The operating temperature is the temperature of the gas separation membrane in each gas separation membrane unit. The O2 concentration and the N2 recovery rate in the product gas are shown in Table 8. (Conditions)

[00168] -Flow rate (F0) of raw material gas mixture flowing into the system: 100 Nm3 / h

[00169] -Gas composition of the mixture of matter: 21 mol% O2, mol% N2:

[00170] -Pressure of gas flowing to the first gas separation membrane unit 11 (operating pressure): 1.0 MPaG

[00171] -Operating temperature of the first gas separation membrane unit 11: 40C [Table 8] Petition 870260061636, dated 06 / 23 / 2026, pages 65 / 82 / 56 Petition 870260061636, dated 06 / 23 / 2026, pages 66 / 82 / 56

[00172] As can be seen by comparison with Example 19 and Comparative Example 14 shown in Table 8, when the coefficient of variation of gas permeability between the modules of the first gas separation membrane unit 11 or the second gas separation membrane unit 12 is 0.49 or less, the O2 concentration in the product is significantly reduced, which means that the purity can be effectively improved.

[00173] Furthermore, as can be seen from the comparison between Example 19 and Comparative Example 15, when the coefficient of variation decreases to 0.01, the O2 concentration does not change and the N2 recovery rate does not increase, even if the coefficient of variation decreases further.

[00174] Therefore, by setting the coefficient of variation to 0.01 or more, the uniformity of manufacturing conditions can be improved compared to Comparative Example 15, and the manufacturing cost can be reduced. INDUSTRIAL APPLICABILITY

[00175] According to the present invention, a gas separation membrane unit capable of performing gas separation with an excellent recovery rate and purity of a product gas, and a gas separation system using the same are provided. Petition 870260061636, dated 06 / 23 / 2026, pages 67 / 82

Claims

1 / 5 CLAIMS 1. A gas separation membrane unit to which a feedstock gas mixture is supplied to concentrate and enrich at least one of the gases contained in the feedstock gas mixture, characterized in that the gas separation membrane unit comprises a plurality of gas separation membrane modules combined in parallel, each of the gas separation membrane modules comprising: a gas inlet; an impermeable gas outlet; and a permeate gas outlet, the gas inlets of each of the gas separation membrane modules are shared to constitute the gas inlet of the gas separation membrane unit, the impermeable gas outlets of each of the gas separation membrane modules are shared to constitute the impermeable gas outlet of the gas separation membrane unit,The permeate gas outlets of each of the gas separation membrane modules are shared to constitute the permeate gas outlet of the gas separation membrane unit, and a coefficient of variation of a gas separation selectivity among the plurality of gas separation membrane modules is 0.01 or more and 0.40 or less, or a coefficient of variation of a gas permeability among the plurality of gas separation membrane modules is 0.01 or more and 0.40 or less.

2. Gas separation membrane unit according to claim 1, characterized in that the gas separation membrane constituting the gas separation membrane module is a hollow fiber membrane comprising a polymer and having an asymmetric structure. Petition 870260061636, dated 06 / 23 / 2026, p. 78 / 82 2 / 5 3. Gas separation membrane unit according to claim 1 or 2,characterized by being as follows (1) or (2): (1) the feedstock gas mixture contains CO2 and CH4, the gas separation selectivity is a permeation rate ratio P'CO2 / P'CH4 of CO2 to CH4, the gas permeability is a permeation rate P'CO2 of CO2, and the unit of permeation rate is cm3(STP) / cm2 · s · cmHg; (2) the feedstock gas mixture contains N2 and O2, the gas separation selectivity is a P'O2 / P'N2 permeation rate ratio of O2 to N2, the gas permeability is a P'O2 permeation rate of O2, and the unit of permeation rate is cm3(STP) / cm2 · s · cmHg.

4. Gas separation system for supplying a feedstock gas mixture to a gas separation membrane unit to enrich at least one of the gases contained in the feedstock gas mixture, characterized in that the gas separation system comprises at least one first gas separation membrane unit comprising a gas inlet, the gas separation system comprises: a feedstock gas mixture supply line connected to the gas inlet of the first gas separation membrane unit; and a compression means disposed in the feedstock gas mixture supply line;The first gas separation membrane unit comprises the gas separation membrane unit as defined in Petition 870260061636, dated 06 / 23 / 2026, page 79 / 82 3 / 5 claim 1.

5. Gas separation system for supplying a feedstock gas mixture to a gas separation membrane unit to concentrate and enrich at least one of the gases contained in the feedstock gas mixture, characterized in that the gas separation system comprises: at least one first gas separation membrane unit comprising a non-permeated gas inlet and an impermeable gas outlet; and a second gas separation membrane unit comprising a permeated gas inlet and an impermeable gas outlet, the gas separation system comprises: a feedstock gas mixture supply line connected to the gas inlet of the first gas separation membrane unit; a compression means disposed in the feedstock gas mixture supply line;a first line connecting the non-permeated gas outlet of the first gas separation membrane unit and the gas inlet of the second gas separation membrane unit;and a second line connecting the permeate gas outlet of the second gas separation membrane unit and the feedstock gas mixture supply line, and at least one of the first gas separation membrane unit and the second gas separation membrane unit comprises the gas separation membrane unit as defined in claim 1.

6. Gas separation system for supplying a feedstock gas mixture to a gas separation membrane unit for concentrating and enriching at least one of the gases contained in the feedstock gas mixture, characterized in that the gas separation system comprises: a first gas separation membrane unit comprising a gas inlet, a non-permeate gas outlet and a permeate gas outlet; a second gas separation membrane unit comprising a gas inlet and a permeate gas outlet;and a third gas separation membrane unit comprising a gas inlet and a non-permeated gas outlet, the gas separation system comprises: a feedstock gas mixture supply line connected to the gas inlet of the first gas separation membrane unit; a compression means disposed in the feedstock gas mixture supply line; a first line connecting the non-permeated gas outlet of the first gas separation membrane unit and the gas inlet of the second gas separation membrane unit; a second line connecting the permeated gas outlet of the second gas separation membrane unit and the feedstock gas mixture supply line; and a third line connecting the permeated gas outlet of the first gas separation membrane unit and the gas inlet of the third gas separation membrane unit;and a fourth line connecting the non-permeated gas outlet of the third gas separation membrane unit and the feedstock gas mixture supply line, and at least one of the first gas separation membrane unit, the second gas separation membrane unit and the third gas separation membrane unit comprises the gas separation membrane unit as defined in claim 1.

7. Method for producing an enriched gas using the gas separation system as defined in claim 5 or 6, characterized in that the enriched gas is removed from the non-permeated gas outlet of the second gas separation membrane unit.

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