Gas separation apparatus and gas separation method

Abstract

A gas separation device (3) includes a gas supply portion (36), a first separation membrane (310), and a second separation membrane (320). The gas supply portion (36) supplies a mixed gas. The first separation membrane (310) is a separation membrane whose permeability to a third gas is higher than that to a first gas and a second gas. The first separation membrane (310) removes the third gas in the mixed gas supplied from the gas supply portion (36) by permeation. The second separation membrane (320) is a separation membrane whose permeability to the first gas is higher than that to the second gas. The second separation membrane (320) is supplied with a first non-permeated gas in the mixed gas that is not permeated through the first separation membrane (310). The second separation membrane (320) separates the first gas in the first non-permeated gas by permeation. Thus, the size of the device related to separation of the mixed gas can be reduced.

Description

Technical Field

[0001] This invention relates to a technique for separating mixed gases.

[0002] [Reference to relevant applications]

[0003] This application claims priority to Japanese Patent Application JP2024-51751, filed on March 27, 2024, the entire disclosure of which is incorporated herein by reference. Background Technology

[0004] Previously, techniques such as pressure swing adsorption and chemical absorption were used to separate a portion of gases from a mixture containing multiple gases. However, the regeneration of the adsorbent and absorbent in pressure swing adsorption and chemical absorption methods involves significant energy consumption. Therefore, in recent years, membrane separation methods using separation membranes such as zeolite membranes have attracted considerable attention for the separation of mixed gases.

[0005] However, the aforementioned gas mixtures often contain impurities such as water. If membrane separation is used to separate such gas mixtures, these impurities may adsorb onto the pores of the membrane, hindering the permeation of the gas to be separated and reducing separation performance. International Publication No. 2018 / 180210 (Document 1) discloses a technique that involves exposing a separation membrane whose separation performance has been reduced due to contact with a hydrocarbon mixture to an inactive gas atmosphere and heating the inactive gas atmosphere, thereby regenerating the membrane and improving its separation performance.

[0006] Furthermore, in the carbon dioxide separation and recovery system disclosed in Japanese Patent Application Publication No. 2012-236134 (Document 2), a mixed gas is first introduced into an impurity removal device (i.e., a pretreatment device) equipped with an adsorbent such as zeolite to remove impurities from the mixed gas. Then, the mixed gas with removed impurities is introduced into a primary carbon dioxide separator equipped with a zeolite membrane for carbon dioxide separation, where carbon dioxide is separated. Subsequently, it is introduced into a secondary carbon dioxide separator utilizing amine absorption or pressure swing adsorption methods for carbon dioxide separation, where carbon dioxide is separated again. Accordingly, contamination and deterioration of the zeolite membrane for carbon dioxide separation due to impurities are suppressed.

[0007] It should be noted that Japanese Patent No. 6351508 (Document 3), Japanese Patent No. 6400017 (Document 4), Japanese Patent Application Publication No. 2011-184283 (Document 5), Japanese Patent No. 7365453 (Document 6), and Japanese Patent Application Publication No. 2020-163250 (Document 7) propose technologies in which multiple separation membrane modules are connected in series, and in each separation membrane module, the target gas (e.g., carbon dioxide, methane, helium, etc.) contained in the mixed gas is separated from and recovered from the mixed gas. In these technologies, if the mixed gas contains impurities, the impurities need to be removed from the mixed gas using a pretreatment device such as an impurity remover as described in Document 2 before the mixed gas is introduced into the aforementioned multiple separation membrane modules.

[0008] However, the membrane regeneration method in Reference 1 requires the use of inactive gas for regeneration and heating, thus increasing the operating costs for separating the mixed gas. Furthermore, if the membrane performance recovery rate from the regeneration process decreases over time, the membrane needs to be replaced.

[0009] In the carbon dioxide separation and recovery system described in Reference 2, pretreatment equipment such as an impurity remover needs to be installed upstream of the primary and secondary carbon dioxide separators, potentially leading to a larger system size. Furthermore, the adsorbent in the impurity remover needs to be replaced or regenerated periodically, increasing the operating costs for carbon dioxide separation and recovery. References 3-7 also follow the same principle, as they require pretreatment equipment such as impurity removers as described above. Summary of the Invention

[0010] This invention relates to a technique for separating mixed gases, with the aim of preventing the scaling up of equipment associated with the separation of mixed gases.

[0011] The invention of Scheme 1 is a gas separation device that separates a mixture of gas comprising at least a first gas, a second gas, and a third gas as a polar gas. The gas separation device includes: a gas supply unit that supplies the mixture; a first separation membrane that has a higher permeability of the third gas than the first gas and the second gas, allowing the third gas in the mixture supplied from the gas supply unit to pass through and be removed; and a second separation membrane that has a higher permeability of the first gas than the second gas, supplied with a non-permeable gas in the mixture that does not pass through the first separation membrane, allowing the first gas in the non-permeable gas to pass through and be separated.

[0012] According to the present invention, it is possible to suppress the large-scale development of equipment related to the separation of mixed gases.

[0013] The invention of Scheme 2 is based on the gas separation device of Scheme 1, wherein the ratio of silicon content to aluminum content in the first separation membrane is less than 100.

[0014] The invention of Scheme 3 is based on the gas separation device of Scheme 1 (which can be Scheme 1 or 2), wherein the ratio of silicon content to aluminum content in the second separation membrane is greater than 100.

[0015] The invention of Scheme 4 is based on the gas separation device of Scheme 1 (which can be any one of Schemes 1 to 3), wherein the concentration of the third gas in the mixed gas supplied from the gas supply unit is less than 1% by volume.

[0016] The invention of Scheme 5 is based on the gas separation device of Scheme 1 (which can be any of Schemes 1 to 4), wherein the third gas is water or ammonia.

[0017] The invention of Scheme 6 is based on the gas separation device of Scheme 1 (which can be any one of Scheme 1 to 5), wherein the dynamic molecular diameters of the first gas and the second gas are respectively less than 0.4 nm.

[0018] The invention of Scheme 7 is based on the gas separation device of Scheme 6, wherein the dynamic molecular diameter of the first gas is less than 0.3 nm.

[0019] The invention of Scheme 8 is based on the gas separation device of any one of Schemes 1 to 7, wherein the first separation membrane is a zeolite membrane.

[0020] The invention of Scheme 9 is a gas separation method for separating a mixture of gases comprising at least a first gas, a second gas, and a third gas as a polar gas. The gas separation method includes the following steps: a) supplying the mixture of gases to a first separation membrane in which the permeability of the third gas is higher than that of the first gas and the second gas, so that the third gas passes through and is removed; and b) supplying a non-permeable gas in the mixture of gases that does not pass through the first separation membrane to a second separation membrane in which the permeability of the first gas is higher than that of the second gas, so that the first gas in the non-permeable gas passes through and is separated.

[0021] The above-mentioned objectives, as well as other objectives, features, solutions, and advantages, will become clear from the following detailed description of the invention with reference to the accompanying drawings. Attached Figure Description

[0022] Figure 1 This is a diagram illustrating the configuration of a separation device according to one embodiment.

[0023] Figure 2This is a cross-sectional view showing the configuration of the first separation membrane assembly.

[0024] Figure 3 This is a cross-sectional view of the separation membrane complex.

[0025] Figure 4 This is a magnified cross-sectional view showing a portion of the separation membrane complex.

[0026] Figure 5 This is a cross-sectional view showing the configuration of the second separation membrane assembly.

[0027] Figure 6 This is a diagram illustrating the separation process of a mixed gas.

[0028] Figure 7 This is a diagram showing the configuration of the separation device.

[0029] Figure 8 This is a diagram showing the configuration of the separation device. Detailed Implementation

[0030] Figure 1 This is a diagram illustrating the configuration of a gas separation device 3 according to one embodiment of the present invention. Figure 1 The components of the gas separation device 3 are schematically depicted. The gas separation device 3 is a device that separates the first gas from a mixture of a first gas, a second gas, and a third gas after removing the third gas, which is a polar gas.

[0031] The first and second gases are the main components of the gas mixture. The first and second gases are, for example, nonpolar gases. The dynamic molecular diameter of the first gas is, for example, less than 0.4 nm, preferably less than 0.3 nm. The dynamic molecular diameter of the second gas is, for example, less than 0.4 nm. The third gas is a polar gas. The concentration of the third gas in the gas mixture is greater than 0.0% by volume, for example, less than 1% by volume. It should be noted that the first and / or second gases may also be polar gases. Furthermore, the gas mixture may contain at least the first, second, and third gases, or it may contain gases other than the first, second, and third gases.

[0032] The aforementioned gas mixture may be, for example, a biogas comprising carbon dioxide (CO2) as the first gas, methane (CH4) as the second gas, and water (H2O) as the third gas. Alternatively, the gas mixture may comprise hydrogen (H2) as the first gas, nitrogen (N2) as the second gas, and water (H2O) and / or ammonia (NH3) as the third gas. It should be noted that the first, second, and third gases are not limited to the above examples and various modifications may be made.

[0033] The gas separation device 3 includes: a first separation membrane assembly 31, a second separation membrane assembly 32, a first recovery unit 33, a second recovery unit 34, a third recovery unit 35, and a gas supply unit 36. In addition, the gas separation device 3 includes: a first permeable gas flow path 311, a first non-permeable gas flow path 312, a second permeable gas flow path 321, and a second non-permeable gas flow path 322.

[0034] The gas supply unit 36 ​​is connected to the first separation membrane assembly 31. The gas supply unit 36 ​​supplies mixed gas to the first separation membrane assembly 31. The gas supply unit 36 ​​may include, for example, a pressure conveying mechanism such as a blower or pump that pressurizes the mixed gas toward the first separation membrane assembly 31. This pressure conveying mechanism may include, for example, a temperature regulating unit and a pressure regulating unit that regulate the temperature and pressure of the mixed gas supplied to the first separation membrane assembly 31, respectively.

[0035] The first separation membrane assembly 31 and the first recovery unit 33 are connected via a first permeable gas flow path 311. The first separation membrane assembly 31 and the second separation membrane assembly 32 are connected via a first non-permeable gas flow path 312. The second separation membrane assembly 32 and the second recovery unit 34 are connected via a second permeable gas flow path 321. The second separation membrane assembly 32 and the third recovery unit 35 are connected via a second non-permeable gas flow path 322.

[0036] The first separation membrane assembly 31 includes a first separation membrane 310. The specific structure of the first separation membrane assembly 31 will be described below. The permeability of a third gas (e.g., H2O) to the first separation membrane 310 is higher than that of a first gas (e.g., H2) and a second gas (e.g., N2). The first separation membrane 310 selectively allows the third gas in the mixed gas supplied from the gas supply unit 36 ​​to permeate through, removing the third gas as an impurity from the mixed gas. In the first separation membrane assembly 31, the first separation membrane 310 can remove approximately the total amount of the third gas in the mixed gas, or it can remove only a portion of the third gas in the mixed gas.

[0037] The third gas / first gas selectivity of the first separation membrane 310 is preferably 10 or more, more preferably 50 or more. The third gas / first gas selectivity refers to the ratio of the permeation rate (permeability) of the third gas per unit membrane area and per unit pressure difference to the permeation rate of the first gas per unit membrane area and per unit pressure difference. There is no particular upper limit to the third gas / first gas selectivity of the first separation membrane 310; considering practical applications, it is 10,000 or less. It should be noted that the permeation rates of the third gas and the first gas in the first separation membrane 310 are the permeation rates when the partial pressure difference between the supply side and the permeation side of the first separation membrane 310 is 0.1 MPa.

[0038] The gas that has permeated through the first separation membrane 310 in the mixed gas supplied to the first separation membrane assembly 31 is guided to the first recovery unit 33 via the first permeate gas flow path 311. In the following description, the gas that has permeated through the first separation membrane 310 will also be referred to as the "first permeate gas". The first permeate gas is mainly composed of a third gas. The first permeate gas may contain gases other than the third gas (e.g., the first gas and / or the second gas). The first recovery unit 33 is a storage container for storing the first permeate gas or a blower or pump for transferring the first permeate gas.

[0039] Gas that does not permeate through the first separation membrane 310 in the mixed gas supplied to the first separation membrane assembly 31 is supplied to the second separation membrane assembly 32 via the first non-permeable gas flow path 312. In the following description, the gas that does not permeate through the first separation membrane 310 will also be referred to as the "first non-permeable gas". The first non-permeable gas is a gas obtained by removing part or all of the third gas contained in the mixed gas supplied to the first separation membrane assembly 31 through the gas supply section 36. The first non-permeable gas is mainly composed of the first gas and the second gas, which are the main components of the aforementioned mixed gas. The first non-permeable gas may contain gases other than the first gas and the second gas (e.g., the third gas that does not permeate through the first separation membrane 310). The concentration of the third gas in the first non-permeable gas is lower than the concentration of the third gas in the mixed gas fed from the gas supply section 36 toward the first separation membrane assembly 31 (e.g., less than 1% by volume).

[0040] The second separation membrane assembly 32 includes a second separation membrane 320. The specific structure of the second separation membrane assembly 32 will be described below. The permeability of a first gas (e.g., H2) to the second separation membrane 320 is higher than that of a second gas (e.g., N2) to the second separation membrane 320. The second separation membrane 320 selectively allows the first gas in the first non-permeable gas supplied from the first separation membrane assembly 31 to the second separation membrane assembly 32 to pass through and be separated from the first non-permeable gas.

[0041] The first gas / second gas selectivity of the second separation membrane 320 is preferably 50 or more, more preferably 100 or more. The first gas / second gas selectivity refers to the permeation rate ratio obtained by dividing the permeation rate of the first gas per unit membrane area and per unit pressure difference by the permeation rate of the second gas per unit membrane area and per unit pressure difference. There is no particular upper limit to the first gas / second gas selectivity of the second separation membrane 320; considering practical applications, it is 10,000 or less. It should be noted that the permeation rates of the first gas and the second gas in the second separation membrane 320 are the permeation rates when the partial pressure difference between the supply side and the permeation side of the second separation membrane 320 is 0.1 MPa.

[0042] The gas that has passed through the second separation membrane 320 in the first non-permeable gas supplied to the second separation membrane assembly 32 (mainly the first gas) is guided to the second recovery unit 34 via the second permeable gas flow path 321. The gas that has not passed through the second separation membrane 320 in the gas supplied to the second separation membrane assembly 32 (mainly the second gas) is guided to the third recovery unit 35 via the second non-permeable gas flow path 322.

[0043] Gas that has permeated through the second separation membrane 320 in the first non-permeable gas supplied to the second separation membrane assembly 32 is guided to the second recovery unit 34 via the second permeable gas flow path 321. In the following description, the gas that has permeated through the second separation membrane 320 will also be referred to as the "second permeable gas". The second permeable gas is mainly composed of the first gas. The second permeable gas may contain gases other than the first gas (e.g., a second gas and / or a third gas). The second recovery unit 34 is a storage container for storing the second permeable gas or a blower or pump for transferring the second permeable gas.

[0044] Gas that does not permeate through the second separation membrane 320 in the first non-permeable gas supplied to the second separation membrane assembly 32 is guided to the third recovery section 35 via the second non-permeable gas flow path 322. In the following description, the gas that does not permeate through the second separation membrane 320 will also be referred to as the "second non-permeable gas". The second non-permeable gas is the gas obtained by removing part or all of the first gas from the first non-permeable gas supplied to the second separation membrane assembly 32 from the first separation membrane assembly 31. The second non-permeable gas is mainly composed of a second gas, or a first gas and a second gas. The second non-permeable gas may contain gases other than the first and second gases (e.g., a third gas). The concentration of the first gas in the second non-permeable gas is lower than the concentration of the first gas in the first non-permeable gas discharged from the first separation membrane assembly 31 toward the second separation membrane assembly 32.

[0045] Next, refer to Figures 2 to 4 An example of the specific structure of the first separation membrane assembly 31 will be described. Figure 2 This is a cross-sectional view showing the configuration of the first separation membrane assembly 31. Figure 3 This is a cross-sectional view of the separation membrane composite 1 of the first separation membrane assembly 31. Figure 4 This is a cross-sectional view showing a portion of the separation membrane composite 1.

[0046] The first separation membrane assembly 31 includes: a separation membrane composite 1, a sealing part 21, a housing 22, and two sealing components 23. The separation membrane composite 1, the sealing part 21, and the sealing components 23 are housed within the internal space of the housing 22.

[0047] The separation membrane composite 1 comprises: a porous support 11 and a first separation membrane 310 formed on the support 11. Figure 3 In the middle, the first separation membrane 310 is drawn with thick lines. Figure 4 In the diagram, the first separation membrane 310 is marked with parallel oblique lines. Additionally, Figure 4 In the process, the thickness of the first separation membrane 310 is depicted as thicker than it actually is.

[0048] The support 11 is a porous component that allows gas to pass through. Figure 2 In the example shown, the support 11 is provided along the length direction (i.e.,) of the integrally formed, connected columnar body. Figure 2 An integral support body with multiple through holes 111 extending in the left and right directions. Figure 2 and Figure 3 In the example shown, the support 11 is generally cylindrical. The cross-section of each through hole 111 (i.e., compartment) perpendicular to the length direction is, for example, generally circular. Figure 2 and Figure 3 In the diagram, the diameter of the through hole 111 is depicted as larger than it actually is, and the number of through holes 111 is depicted as fewer than it actually is. The first separation membrane 310 is formed on the inner surface of the through hole 111, and the inner surface of the through hole 111 is covered almost entirely.

[0049] The length of the support 11 (i.e., Figure 2 The length (in the left-right direction) of the support 11 is, for example, 10cm to 200cm. The outer diameter of the support 11 is, for example, 0.5cm to 30cm. The distance between the central axes of adjacent through holes 111 is, for example, 0.3mm to 10mm. The surface roughness (Ra) of the support 11 is, for example, 0.1μm to 5.0μm, preferably 0.2μm to 2.0μm. It should be noted that the shape of the support 11 can be, for example, honeycomb, flat, tubular, cylindrical, prismatic, or polygonal. When the shape of the support 11 is tubular or cylindrical, the thickness of the support 11 is, for example, 0.1mm to 10mm.

[0050] The material of the support 11 only needs to be chemically stable during the process of forming the first separation film 310 on the surface, and various substances (such as ceramics or metals) can be used. In this embodiment, the support 11 is formed from a ceramic sintered body. Examples of ceramic sintered bodies selected as the material of the support 11 include: alumina, silicon dioxide, andalusite, zirconium oxide, titanium dioxide, yttrium oxide, silicon nitride, silicon carbide, etc. In this embodiment, the support 11 includes at least one of alumina, silicon dioxide, andalusite.

[0051] The support 11 may contain an inorganic binder. As an inorganic binder, at least one of the following can be used: titanium dioxide, andalusite, easily sinterable alumina, silica, glass frit, clay minerals, and easily sinterable cordierite.

[0052] The average pore size of the support 11 near the surface where the first separation membrane 310 is to be formed is preferably smaller than the average pore size of other parts of the support 11. To achieve such a structure, the support 11 has a multilayer structure. When the support 11 has a multilayer structure, the materials of each layer can be the materials described above, and they can be the same or different. The average pore size of the support 11 can be measured using a mercury porosimeter, a pore size distribution measuring instrument, a nanoscale pore size distribution measuring instrument, or the like.

[0053] The average pore size of the support 11 is, for example, 0.01 μm to 70 μm, preferably 0.05 μm to 25 μm. The average pore size of the support 11 near the surface where the first separation membrane 310 is to be formed is 0.01 μm to 1 μm, preferably 0.05 μm to 0.5 μm. Regarding the overall pore size distribution of the support 11, including the surface and interior, D5 is, for example, 0.01 μm to 50 μm, D50 is, for example, 0.05 μm to 70 μm, and D95 ​​is, for example, 0.1 μm to 2000 μm. The porosity of the support 11 near the surface where the first separation membrane 310 is to be formed is, for example, 25% to 50%.

[0054] The first separation membrane 310 is a porous membrane with fine pores. The first separation membrane 310 is a gas separation membrane that separates a third gas by allowing it to permeate from a mixed gas obtained by mixing multiple gases, as described above. It should be noted that separating the third gas means allowing at least a portion of the third gas in the mixed gas to permeate through the first separation membrane 310 and the support 11, and there is no limitation on the concentration of the third gas in the first permeated gas.

[0055] The thickness of the first separation membrane 310 is, for example, 0.05 μm to 30 μm, preferably 0.1 μm to 20 μm, and more preferably 0.5 μm to 10 μm. Increasing the thickness of the first separation membrane 310 improves selectivity. Decreasing the thickness of the first separation membrane 310 increases the permeation rate. The surface roughness (Ra) of the first separation membrane 310 is, for example, 5 μm or less, preferably 2 μm or less, more preferably 1 μm or less, and even more preferably 0.5 μm or less.

[0056] The average pore size of the first separation membrane 310 is 1 nm or less. This improves the selectivity of the third gas in the first separation membrane 310. The lower limit of the average pore size of the first separation membrane 310 is not particularly limited, as long as it allows the third gas to pass through; for example, it can be 0.2 nm or more. The average pore size of the first separation membrane 310 is preferably 0.2 nm or more and 0.8 nm or less, more preferably 0.3 nm or more and 0.6 nm or less, and even more preferably 0.3 nm or more and 0.5 nm or less. If the average pore size of the first separation membrane 310 is reduced, the selectivity is improved. If the average pore size of the first separation membrane 310 is increased, the permeation rate is increased. The average pore size of the first separation membrane 310 is smaller than the average pore size at the surface of the support 11 on which the first separation membrane 310 is disposed.

[0057] The first separation membrane 310 is preferably an inorganic membrane, and in this embodiment, it is a zeolite membrane (i.e., a membrane-like zeolite). As a zeolite membrane, it is a membrane obtained by forming zeolite in a membrane-like form on at least the surface of the support 11, etc., and does not include membranes obtained simply by dispersing zeolite particles in an organic membrane. It should be noted that the zeolite membrane may include two or more types of zeolite with different structures and compositions, and may also contain a portion of substances other than zeolite through surface treatment or the like.

[0058] The zeolite constituting the first separation membrane 310 can be: zeolite whose T atoms (atoms) at the center of the oxygen tetrahedron (TO4) constituting the zeolite consist only of Si; zeolite whose T atoms include Si and Al; AlPO-type zeolite whose T atoms include Al and P; SAPO-type zeolite whose T atoms include Si, Al, and P; MAPSO-type zeolite whose T atoms include magnesium (Mg), Si, Al, and P; and ZnAPSO-type zeolite whose T atoms include zinc (Zn), Si, Al, and P. A portion of the T atoms can be replaced by other elements.

[0059] When the maximum number of rings in the zeolite constituting the first separation membrane 310 is n, the arithmetic mean of the minor and major axes of the n-membered ring pores is taken as the average pore diameter (the same applies to the second separation membrane 320). An n-membered ring pore refers to a pore in which n oxygen atoms are bonded to T atoms to form a ring structure. When the zeolite has multiple n-membered ring pores of equal size, the arithmetic mean of the minor and major axes of all the n-membered ring pores is taken as the average pore diameter of the zeolite. In this way, the average pore diameter of the zeolite membrane is uniquely determined by the zeolite's framework structure and can be solved using values ​​published in the International Zeolite Society's "Database of Zeolite Structures" [online], URL <URL: http: / / www.iza-structure.org / databases / >.

[0060] The type of zeolite constituting the first separation membrane 310 is not particularly limited, and can be, for example, AEI type, AEN type, AFN type, AFV type, AFX type, BEA type, CHA type, DDR type, ERI type, ETL type, FAU type (X type, Y type), GIS type, LEV type, LTA type, MEL type, MFI type, MOR type, PAU type, RHO type, SAT type, SOD type, etc. From the viewpoint of increasing the permeation rate of the third gas and improving selectivity, the maximum number of ring elements of the zeolite is preferably 8 or less (e.g., 6 or 8). The first separation membrane 310 is, for example, an LTA type zeolite. In other words, the first separation membrane 310 is a zeolite membrane composed of zeolite with the structure code "LTA" specified by the International Zeolite Institute. In this case, the inherent pore size of the zeolite constituting the first separation membrane 310 is 0.41 nm × 0.41 nm, and the average pore size is 0.41 nm.

[0061] The first separation membrane 310 may contain silicon (Si). The first separation membrane 310 may contain any two or more of Si, aluminum (Al), and phosphorus (P). The first separation membrane 310 may contain an alkali metal, such as sodium (Na) or potassium (K).

[0062] When the first separation membrane 310 contains both Si and Al, the ratio of Si content to Al content (hereinafter also referred to as the "Si / Al ratio") in the first separation membrane 310 is, for example, 100 or less, preferably 50 or less, and more preferably 30 or less. Accordingly, the polarity of the first separation membrane 310 increases, and the hydrophilicity of the first separation membrane 310 increases. As a result, the third gas, being a polar gas, is easily adsorbed onto the first separation membrane 310, thereby increasing the permeation rate of the third gas in the first separation membrane 310. It should be noted that the Si / Al ratio in the first separation membrane 310 is, for example, 1 or more.

[0063] The Si / Al ratio in the first separation membrane 310 can be adjusted, for example, by adjusting the ratio of Si source and Al source in the feed solution when the first separation membrane 310 is formed by hydrothermal synthesis (the same applies to the Si / Al ratio in the second separation membrane 320).

[0064] The sealing part 21 is: provided in the longitudinal direction of the support 11 (i.e., Figure 2The sealing part 21 is a component that covers and seals the two ends of the support body 11 in the left-right direction and the two end faces and the outer surfaces near the end faces in the longitudinal direction. The sealing part 21 prevents gas from flowing in and out relative to the two end faces of the support body 11. The sealing part 21 is, for example, a plate-shaped component made of glass or resin. The material and shape of the sealing part 21 can be appropriately changed. It should be noted that the sealing part 21 is provided with multiple openings that coincide with the multiple through holes 111 of the support body 11. Therefore, the two ends in the longitudinal direction of each through hole 111 of the support body 11 are not covered by the sealing part 21. Therefore, gas can flow in and out from the two ends through the through holes 111.

[0065] The outer casing 22 is a generally cylindrical cylindrical component. The outer casing 22 is formed of, for example, stainless steel or carbon steel. The length direction of the outer casing 22 is generally parallel to the length direction of the separation membrane composite 1. At one end of the outer casing 22 in the length direction (i.e., Figure 2 A supply port 221 is provided at the left end of the housing 22, and a first outlet 222 is provided at the other end. A second outlet 223 is provided on the side of the housing 22. A gas supply unit 36 ​​is connected to the supply port 221. A second separation membrane assembly 32 is connected to the first outlet 222 via a first non-permeable gas flow path 312. A first recovery unit 33 is connected to the second outlet 223 via a first permeable gas flow path 311. The internal space of the housing 22 is a sealed space isolated from the space surrounding the housing 22.

[0066] Two sealing components 23 are arranged circumferentially near both ends of the separation membrane composite 1 along its length, between the outer surface of the separation membrane composite 1 (i.e., the outer surface of the support 11) and the inner surface of the housing 22. Each sealing component 23 is a generally annular component formed of a gas-impermeable material. For example, the sealing component 23 is an O-ring formed of a flexible resin. The sealing components 23 are tightly fitted circumferentially to the outer surface of the separation membrane composite 1 and the inner surface of the housing 22. Figure 2 In the example shown, the sealing member 23 is sealed to the outer side of the sealing part 21 and indirectly sealed to the outer side of the separation membrane composite 1 by sandwiching the sealing part 21. The sealing member 23 is sealed between the outer side of the separation membrane composite 1 and the inner side of the housing 22, so that gas can hardly or completely pass through.

[0067] Figure 5 This is a cross-sectional view showing an example of the specific structure of the second separation membrane assembly 32. In this embodiment, regarding the structure of the second separation membrane assembly 32, a second separation membrane 320 is provided in the separation membrane composite 1 instead of the first separation membrane 310; otherwise, it is similar to... Figure 2 The structure of the first separation membrane assembly 31 shown is roughly the same. Figure 5In the figure, the components of the second separation membrane assembly 32 are labeled with the same reference numerals as the components of the first separation membrane assembly 31.

[0068] Like the first separation membrane 310, the second separation membrane 320 is a generally cylindrical thin film disposed on the inner surface of the through hole 111 of the support 11, covering a generally entire inner surface. The second separation membrane 320 is a porous membrane with fine pores. As described above, the second separation membrane 320 is a gas separation membrane that separates the first gas by allowing the first gas to permeate through the first non-permeable gas. It should be noted that separating the first gas means allowing at least a portion of the first gas in the first non-permeable gas to permeate through the second separation membrane 320 and the support 11; there is no limitation on the concentration of the first gas in the second permeable gas.

[0069] The thickness of the second separation membrane 320 is, for example, 0.05 μm to 30 μm, preferably 0.1 μm to 20 μm, and more preferably 0.5 μm to 10 μm. Increasing the thickness of the second separation membrane 320 improves selectivity. Decreasing the thickness of the second separation membrane 320 increases the permeation rate. The surface roughness (Ra) of the second separation membrane 320 is, for example, 5 μm or less, preferably 2 μm or less, more preferably 1 μm or less, and even more preferably 0.5 μm or less.

[0070] The average pore size of the second separation membrane 320 is 1 nm or less. This improves the selectivity of the first gas in the second separation membrane 320. The lower limit of the average pore size of the second separation membrane 320 is not particularly limited, as long as it allows the first gas to pass through; for example, it can be 0.2 nm or more. The average pore size of the second separation membrane 320 is preferably 0.2 nm or more and 0.8 nm or less, more preferably 0.3 nm or more and 0.6 nm or less, and even more preferably 0.3 nm or more and 0.5 nm or less. If the average pore size of the second separation membrane 320 is reduced, the selectivity is improved. If the average pore size of the second separation membrane 320 is increased, the permeation rate is increased. The average pore size of the second separation membrane 320 is smaller than the average pore size at the surface of the support 11 on which the second separation membrane 320 is disposed.

[0071] The second separation membrane 320 is preferably an inorganic membrane, and in this embodiment, it is a zeolite membrane. As the zeolite constituting the second separation membrane 320, it can be substantially the same as that of the first separation membrane 310, including zeolites whose T atoms at the center of the oxygen tetrahedron (TO4) constituting the zeolite consist only of Si, zeolites whose T atoms include both Si and Al, AlPO type zeolites, SAPO type zeolites, MAPSO type zeolites, ZnAPSO type zeolites, etc.

[0072] The type of zeolite constituting the second separation membrane 320 is not particularly limited, and can be, for example, AEI type, AEN type, AFN type, AFV type, AFX type, BEA type, CHA type, DDR type, ERI type, ETL type, FAU type (X type, Y type), GIS type, LEV type, LTA type, MEL type, MFI type, MOR type, MTN type, PAU type, RHO type, SAT type, SOD type, etc. From the viewpoint of increasing the permeation rate of the first gas and improving selectivity, the maximum number of ring elements of the zeolite is preferably 8 or less (e.g., 6 or 8). The second separation membrane 320 is, for example, a DDR type zeolite. In this case, the inherent pore size of the zeolite constituting the second separation membrane 320 is 0.36 nm × 0.44 nm, and the average pore size is 0.40 nm.

[0073] The second separation membrane 320 may contain, for example, silicon (Si). The second separation membrane 320 may contain, for example, any two or more of Si, aluminum (Al), and phosphorus (P). The second separation membrane 320 may contain an alkali metal, such as sodium (Na) or potassium (K).

[0074] When the second separation membrane 320 contains both Si and Al, the Si / Al ratio in the second separation membrane 320 is, for example, greater than 100, preferably 150 or more, and more preferably 200 or more. Accordingly, the polarity of the second separation membrane 320 decreases, and its hydrophobicity increases. Therefore, even if a third gas, which is a polar gas, remains in the first non-permeable gas, the adsorption of the third gas on the second separation membrane 320 can be suppressed. As a result, the decrease in the permeability of the second separation membrane 320 caused by the adsorption of the third gas (e.g., a decrease in the permeation rate of the first gas in the second separation membrane 320) can be suppressed.

[0075] The aforementioned mixed gas includes, for example, one or more of the following gases: hydrogen (H2), helium (He), nitrogen (N2), oxygen (O2), carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides, ammonia (NH3), sulfur oxides, hydrogen sulfide (H2S), sulfur fluoride, mercury (Hg), arsine (AsH3), hydrogen cyanide (HCN), carbonyl sulfide (COS), C1-C8 hydrocarbons, organic acids, alcohols, thiols, esters, ethers, ketones, and aldehydes.

[0076] Nitrogen oxides refer to compounds of nitrogen and oxygen. Examples of nitrogen oxides include nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (also known as dinitrogen monoxide) (N2O), dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4), and dinitrogen pentoxide (N2O5), all collectively referred to as NO. X (NOx) gas.

[0077] Sulfur oxides are compounds of sulfur and oxygen. Examples of sulfur oxides include sulfur dioxide (SO2) and sulfur trioxide (SO3), collectively referred to as SO42-SO ... X (Sox) gas.

[0078] Sulfur fluoride refers to compounds of fluorine and sulfur. Examples of sulfur fluoride include disulfur difluoride (F-S-S-F, S=SF2), sulfur difluoride (SF2), sulfur tetrafluoride (SF4), sulfur hexafluoride (SF6), or disulfur decafluoride (S2F). 10 )wait.

[0079] Hydrocarbons with C1 to C8 carbon atoms are defined as hydrocarbons with one or more but fewer than eight carbon atoms. Hydrocarbons with C3 to C8 carbon atoms can be any of the following: straight-chain compounds, side-chain compounds, and cyclic compounds. Additionally, hydrocarbons with C2 to C8 carbon atoms can be any of the following: saturated hydrocarbons (i.e., hydrocarbons without double or triple bonds in the molecule) and unsaturated hydrocarbons (i.e., hydrocarbons with double and / or triple bonds in the molecule). Examples of hydrocarbons with C1 to C4 carbon atoms include methane (CH4), ethane (C2H6), ethylene (C2H4), propane (C3H8), propylene (C3H6), n-butane (CH3(CH2)2CH3), isobutane (CH(CH3)3), 1-butene (CH2=CHCH2CH3), 2-butene (CH3CH=CHCH3), or isobutene (CH2=C(CH3)2).

[0080] The organic acids mentioned above are carboxylic acids or sulfonic acids, etc. Examples of carboxylic acids include formic acid (CH2O2), acetic acid (C2H4O2), oxalic acid (C2H2O4), acrylic acid (C3H4O2), or benzoic acid (C6H5COOH), etc. Examples of sulfonic acids include ethanesulfonic acid (C2H6O3S), etc. These organic acids can be chain compounds or cyclic compounds.

[0081] The alcohols mentioned above include, for example, methanol (CH3OH), ethanol (C2H5OH), isopropanol (2-propanol) (CH3CH(OH)CH3), ethylene glycol (CH2(OH)CH2(OH)) or butanol (C4H9OH), etc.

[0082] Thiols are organic compounds with hydrogenated sulfur (SH) at their terminals, also known as Thiol or Thioalcohol. Examples of thiols include methanethiol (CH3SH), ethanethiol (C2H5SH), and 1-propanethiol (C3H7SH).

[0083] The esters mentioned above are, for example, formate esters or acetate esters.

[0084] The ethers mentioned above are, for example, dimethyl ether ((CH3)2O), methyl ethyl ether (C2H5OCH3), or diethyl ether ((C2H5)2O), etc.

[0085] The ketones mentioned above include acetone ((CH3)2CO), methyl ethyl ketone (C2H5COCH3), or diethyl ketone ((C2H5)2CO), etc.

[0086] The aldehydes mentioned above include acetaldehyde (CH3CHO), propionaldehyde (C2H5CHO), or butylaldehyde (C3H7CHO).

[0087] Figure 6 This is a diagram illustrating the separation process of a mixed gas based on the gas separation device 3. As described above, in the gas separation device 3, firstly, using the gas supply unit 36, gas is separated via the first separation membrane assembly 31 (see reference 31). Figure 2 The mixed gas is supplied to the internal space of the housing 22 through the supply port 221. The pressure of the mixed gas supplied to the first separation membrane assembly 31 is, for example, 0.1 MPaG to 10 MPaG, preferably 0.3 MPaG or more. The temperature of the mixed gas is, for example, 10°C to 250°C.

[0088] The first, second, and third gases contained in the gas mixture are, for example, H2, N2, and H2O, respectively. The concentration of the first gas in the gas mixture is, for example, 20% to 80% by volume. The concentration of the second gas in the gas mixture is, for example, 80% to 20% by volume. The combined concentration of the first and second gases in the gas mixture is, for example, 99% to 99.9% by volume. The concentration of the third gas in the gas mixture is, for example, 0.001% to 1% by volume.

[0089] The mixed gas supplied from the gas supply unit 36 ​​to the housing 22 of the first separation membrane assembly 31 is supplied to the separation membrane composite 1 as indicated by arrow 251, and from the separation membrane composite 1... Figure 2 The left end of the gas is introduced into each through hole 111 of the support 11. The first permeate gas, which is mainly composed of the aforementioned third gas (e.g., H2O), permeates through the first separation membrane 310 provided on the inner side of each through hole 111 and the support 11, and is discharged from the outer side of the support 11. Accordingly, the third gas in the mixed gas is separated from the mixed gas and removed as an impurity (step S11). The first permeate gas, as shown by arrow 253, is guided to the first recovery unit 33 through the second outlet 223 and the first permeate gas flow path 311, and is recovered by the first recovery unit 33. The third gas in the first permeate gas recovered by the first recovery unit 33 can be returned to the gas supply unit 36, or it can be discarded, or it can be used for various purposes.

[0090] The concentration of the third gas in the first permeate gas is higher than the concentration of the third gas in the mixed gas. The concentrations of the first and second gases in the first permeate gas are lower than the concentrations of the first and second gases in the mixed gas, respectively. The concentration of the third gas in the first permeate gas is, for example, 90% to 100% by volume, preferably 95% by volume or more. The concentration of the first gas in the first permeate gas is, for example, 0% to 10% by volume. The concentration of the second gas in the first permeate gas is, for example, 0% to 10% by volume. The pressure of the first permeate gas is, for example, -0.09 MPaG to 1 MPaG.

[0091] The recovery rate of the third gas by the first separation membrane 310 is, for example, 50% to 90%, preferably 70% or more. The recovery rate of the third gas by the first separation membrane 310 is calculated by dividing the mass of the third gas that has passed through the first separation membrane 310 in the first separation membrane assembly 31 (i.e., the mass of the third gas in the first permeate gas) by the mass of the third gas in the mixed gas supplied from the gas supply unit 36 ​​(i.e., (mass of the third gas in the first permeate gas) / (mass of the third gas in the mixed gas)).

[0092] The first non-permeable gas in the first separation membrane assembly 31 that does not permeate from the first separation membrane 310 flows through each through hole 111 of the support 11. Figure 2 As shown by arrow 252, the gas flows from the left to the right and is supplied to the second separation membrane assembly 32 via the first outlet 222 and the first non-permeable gas flow path 312.

[0093] The concentrations of the first and second gases in the first non-permeable gas are higher than those in the mixed gas, respectively. The concentration of the third gas in the first non-permeable gas is lower than that in the mixed gas. The concentration of the first gas in the first non-permeable gas is, for example, 20% to 80% by volume. The concentration of the second gas in the first non-permeable gas is, for example, 80% to 20% by volume. The concentration of the third gas in the first non-permeable gas is, for example, 0.001% to 0.1% by volume. The pressure of the first non-permeable gas is, for example, 0.1 MPaG to 10 MPaG.

[0094] The material is supplied from the first separation membrane assembly 31 to the housing 22 (see reference 221) via the supply port 221 of the second separation membrane assembly 32. Figure 5 The first non-permeable gas within the membrane is supplied to the separation membrane composite 1 as indicated by arrow 251, and from the separation membrane composite 1... Figure 5The left end of the gas is introduced into each through hole 111 of the support 11. The second permeable gas, mainly composed of the first gas (e.g., H2), permeates through the second separation membrane 320 disposed on the inner side of each through hole 111 and the support 11, and is discharged from the outer side of the support 11. Accordingly, the first gas in the first non-permeable gas is separated from the first non-permeable gas (step S12). The second permeable gas, as shown by arrow 253, is guided to the second recovery unit 34 through the second outlet 223 and the second permeable gas flow path 321, and is recovered by the second recovery unit 34. The first gas in the second permeable gas recovered by the second recovery unit 34 can be used for various applications.

[0095] The concentration of the first gas in the second permeate gas is higher than the concentration of the first gas in the first non-permeate gas. The concentration of the second gas in the second permeate gas is lower than the concentration of the second gas in the first non-permeate gas. The concentration of the first gas in the second permeate gas is, for example, 90% to 100% by volume, preferably 95% by volume or more. The concentration of the second gas in the second permeate gas is, for example, 0% to 10% by volume. The pressure of the second permeate gas is, for example, 0 MPaG to 1 MPaG.

[0096] The second non-permeable gas in the second separation membrane assembly 32, which does not permeate from the second separation membrane 320, flows through each through hole 111 of the support 11. Figure 5 The gas flows from left to right, as indicated by arrow 252, and is guided to the third recovery section 35 via the first outlet 222 and the second non-permeable gas flow path 322, where it is recovered. The second gas in the second non-permeable gas recovered by the third recovery section 35 can be used for various applications. Alternatively, the second non-permeable gas recovered by the third recovery section 35 can be fed to the supply port 221 of the first separation membrane assembly 31 (see reference). Figure 2 It guides and supplies into the housing 22 of the first separation membrane assembly 31.

[0097] As explained above, the gas separation apparatus 3 is an apparatus for separating a mixture of gases, including at least a first gas, a second gas, and a third gas that is a polar gas. The gas separation apparatus 3 includes a gas supply unit 36, a first separation membrane 310, and a second separation membrane 320. The gas supply unit 36 ​​supplies the mixed gas. The first separation membrane 310 is a membrane in which the permeability of the third gas is higher than that of the first and second gases. The first separation membrane 310 removes the third gas from the mixed gas supplied from the gas supply unit 36 ​​by allowing it to pass through. The second separation membrane 320 is a membrane in which the permeability of the first gas is higher than that of the second gas. The second separation membrane 320 is supplied with a non-permeable gas (i.e., a first non-permeable gas) from the mixed gas that does not pass through the first separation membrane 310. The second separation membrane 320 separates the first gas from the first non-permeable gas by allowing it to pass through.

[0098] In the gas separation apparatus 3, the third gas is removed from the mixed gas by the first separation membrane 310, thereby reducing the concentration of the third gas in the first non-permeable gas supplied to the second separation membrane 320. Accordingly, it is possible to suppress or prevent a decrease in the permeation performance of the second separation membrane 320 (e.g., the permeation rate of the first gas in the second separation membrane 320) due to the adsorption of the third gas on the second separation membrane 320. As a result, the separation of the first gas based on the second separation membrane 320 can be performed effectively. Furthermore, the deterioration of the permeation performance of the second separation membrane 320 over time can be suppressed.

[0099] Furthermore, in the gas separation device 3, the third gas (i.e., impurities) in the mixed gas is removed by the first separation membrane 310. Therefore, it is not necessary to install pretreatment equipment such as an impurity remover with adsorbent upstream of the gas separation device 3 as in the past. This reduces the need for large-scale equipment related to the separation of the mixed gas. In addition, the replacement and regeneration of the adsorbent required in the aforementioned pretreatment equipment is eliminated, thus reducing the maintenance frequency of equipment related to the separation of the mixed gas.

[0100] As described above, the ratio of Si content to Al content in the first separation membrane 310 (i.e., the Si / Al ratio) is preferably 100 or less. Accordingly, the polarity of the first separation membrane 310 increases, and its hydrophilicity also increases. As a result, the third gas, being a polar gas, readily adsorbs onto the first separation membrane 310, increasing the permeation rate of the third gas within the first separation membrane 310. Therefore, the third gas can be effectively removed from the mixed gas.

[0101] As described above, the first gas and the second gas are preferably non-polar gases. Accordingly, the permeation of the first gas and the second gas through the first separation membrane 310, which is a polar gas, can be suppressed. As a result, the separation of the third gas based on the first separation membrane 310 can be performed effectively. Furthermore, the amount of the first gas separated and recovered through the second separation membrane 320 can be increased.

[0102] As described above, the ratio of Si content to Al content in the second separation membrane 320 (i.e., the Si / Al ratio) is preferably greater than 100. Accordingly, the polarity of the second separation membrane 320 decreases, and its hydrophobicity increases. Therefore, even if a third gas, which is a polar gas, remains in the first non-permeable gas, adsorption of the third gas into the second separation membrane 320 can be suppressed. As a result, the decrease in permeability of the second separation membrane 320 caused by the adsorption of the third gas (e.g., a decrease in the permeation rate of the first gas in the second separation membrane 320) can be suppressed.

[0103] As described above, the concentration of the third gas in the mixed gas supplied from the gas supply unit 36 ​​is preferably 1% by volume or less. Even such trace amounts of impurities can be effectively removed by providing the first separation membrane 310 in the gas separation device 3.

[0104] In the gas separation device 3, as described above, it is possible to suppress the large-scale operation of equipment related to the separation of the mixed gas and to effectively remove the third gas, which is a polar gas, from the mixed gas. Therefore, the gas separation device 3 is particularly suitable for situations where the third gas is water or ammonia. In the gas separation device 3, it is possible to suppress or prevent the adsorption of water or ammonia onto the second separation membrane 320, which would lead to a decrease in the permeability of the second separation membrane 320.

[0105] As described above, the dynamic molecular diameters of the first gas and the second gas are preferably less than 0.4 nm. In the gas separation apparatus 3, even when the dynamic molecular diameters of the first gas and the second gas are relatively small, the first gas can be well separated by using the second separation membrane 320 by removing the third gas in advance using the first separation membrane 310.

[0106] As described above, the dynamic molecular diameter of the first gas is preferably less than 0.3 nm. In the gas separation apparatus 3, even when the dynamic molecular diameter of the first gas is small, the first gas can be well separated by the second separation membrane 320 by removing the third gas beforehand using the first separation membrane 310.

[0107] In the gas separation apparatus 3, the first separation membrane 310 is preferably a zeolite membrane. Zeolite membranes have inherently fine pore sizes, thus allowing specific impurities (i.e., the third gas) to permeate effectively and be removed from the mixed gas. Furthermore, the maximum number of rings in the zeolite constituting the first separation membrane 310 is preferably 8 or less. Accordingly, even when the dynamic molecular diameter of the third gas is relatively small, selective permeation (i.e., removal from the mixed gas) of the third gas can be effectively achieved.

[0108] In the gas separation apparatus 3, the second separation membrane 320 is preferably a zeolite membrane. As described above, the zeolite membrane has an inherently fine pore size, thus allowing the first gas to permeate well and be separated from the first non-permeable gas. Furthermore, the maximum number of rings in the zeolite constituting the second separation membrane 320 is preferably 8 or less. Accordingly, even when the dynamic molecular diameters of the first and second gases are relatively small, selective permeation of the first gas (i.e., separation of the first and second gases) can be effectively achieved.

[0109] The gas separation method described above is a method for separating a mixture of gases containing at least a first gas, a second gas, and a third gas as a polar gas. This gas separation method includes the following steps: supplying the mixed gas to a first separation membrane 310, where the permeability of the third gas is higher than that of the first and second gases, allowing the third gas to pass through and be removed (step S11); and supplying a non-permeable gas (i.e., a first non-permeable gas) from the mixed gas that has not passed through the first separation membrane 310 to a second separation membrane 320, where the permeability of the first gas is higher than that of the second gas, allowing the first gas in the first non-permeable gas to pass through and be separated (step S12).

[0110] Accordingly, similarly as described above, it is possible to suppress or prevent the adsorption of a third gas onto the second separation membrane 320, thereby reducing the permeation performance of the second separation membrane 320. Furthermore, it is possible to suppress the need for large-scale equipment related to the separation of mixed gases. In addition, it is possible to reduce the maintenance frequency of equipment related to the separation of mixed gases.

[0111] Next, referring to Tables 1 and 2, embodiments and comparative examples related to the separation of mixed gases based on the gas separation device 3 will be described.

[0112] [Table 1]

[0113]

[0114] [Table 2]

[0115]

[0116] In Examples 1-4, the following methods were adopted: Figure 1 The gas separation device 3 shown separates the mixed gas. Additionally, in Comparative Examples 1-3, a gas separation device is used... Figure 1 The gas separation device 3 shown is a comparative example gas separation device that omits the first separation membrane assembly 31 and the first recovery unit 33, and performs the separation of mixed gases. In the comparative example gas separation device, the gas supply unit 36 ​​is connected to the supply port 221 of the second separation membrane assembly 32 without passing through the first separation membrane assembly 31.

[0117] In Comparative Example 1, the first separation membrane assembly 31 is omitted, and the second separation membrane 320 in the second separation membrane assembly 32 is a zeolite membrane composed of DDR type zeolite. The Si / Al ratio in the second separation membrane 320 is greater than 100.

[0118] The separation membrane composite 1, comprising a second separation membrane 320 as a DDR-type zeolite membrane, is manufactured according to the method described in International Publication No. 2017 / 169591. First, a support 11 is immersed in a solution obtained by dispersing seed crystals, causing the seed crystals to adhere to the support 11. Next, the support 11 with the attached seed crystals is immersed in a raw material solution for hydrothermal synthesis. Accordingly, zeolite is grown using the seed crystals as nuclei, forming the second separation membrane 320 on the support 11.

[0119] In Comparative Example 1, the mixed gas supplied from the gas supply unit 36 ​​to the second separation membrane assembly 32 contains CO2 as the first gas, CH4 as the second gas, and H2O as the third gas. The composition of this mixed gas (CO2 / CH4 / H2O) is 50 vol% / 49.6 vol% / 0.4 vol%. The pressure and temperature of the mixed gas supplied from the gas supply unit 36 ​​are 0.5 MPaG and 30°C, respectively. The pressure of the second permeate gas in the second separation membrane assembly 32 is 0 MPaG.

[0120] In Comparative Example 1, the first separation membrane assembly 31 was omitted as described above; therefore, the third gas was not recovered in the first separation membrane assembly 31. Consequently, the concentration of the third gas in the supply gas supplied to the second separation membrane assembly 32 was the same as the concentration in the aforementioned mixed gas, which was 0.4% by volume.

[0121] In Comparative Example 1, CH4, as the second gas, is the gas to be recovered in the second separation membrane assembly 32 (hereinafter also referred to as "recovered gas"). Therefore, this recovered gas is recovered in the third recovery section 35 as the second non-permeable gas in the second separation membrane assembly 32. The "recovery rate" and "recovered gas amount" in Table 2 represent: the area of ​​the second separation membrane 320 required to achieve a purity of 95% (i.e., a concentration of 95% by volume) in the second non-permeable gas, the recovery rate of the recovered gas recovered using the second separation membrane 320 with that area, and the amount of recovered gas recovered. The recovery rate of the recovered gas (i.e., the value obtained by dividing the amount of recovered gas recovered in the third recovery section 35 by the amount of recovered gas in the mixed gas) is 86.9%. In Comparative Example 1 and Example 1, regarding the amount of recovered gas, the amount of recovered gas in Comparative Example 1 is set as a baseline (i.e., 1), expressed as a ratio. Therefore, the amount of recovered gas in Comparative Example 1 is 1.

[0122] In Example 1, a first separation membrane assembly 31 is provided; otherwise, it is the same as in Comparative Example 1. In Example 1, the first separation membrane 310 in the first separation membrane assembly 31 is a zeolite membrane made of LTA-type zeolite. The Si / Al ratio in the first separation membrane 310 is 2.

[0123] The separation membrane composite 1, comprising a first separation membrane 310 as an LTA-type zeolite membrane, is prepared in the following order: Sodium hydroxide (manufactured by Sigma-Aldrich) as the Na source and sodium aluminate powder (manufactured by Sigma-Aldrich) as the Al source are mixed in pure water. After stirring the mixture at room temperature for 1 hour, colloidal silica (SNOWTEX-50T: manufactured by Nissan Chemical Co., Ltd.) as the Si source is added to obtain a raw material solution. Assuming that the Si source, Al source, and Na source are all present in the form of oxides, the molar ratios of SiO2 / Al2O3, H2O / Na2O, and Na2O / SiO2 in the raw material solution are set to 4.85, 729, and 0.25, respectively. Next, the raw material solution is stirred at room temperature for 12 hours. 70 minutes after the stirring of the raw material solution ends, a support 11 with LTA-type zeolite seed crystals attached is immersed in the raw material solution, and heating of the raw material solution (hydrothermal synthesis) is started. The hydrothermal synthesis was carried out at 80°C for 100 hours. After the hydrothermal synthesis, the support 11 and the first separation membrane 310, which serves as a zeolite membrane, were thoroughly washed with pure water and then dried at 80°C.

[0124] In Example 1, the mixed gas supplied from the gas supply unit 36 ​​to the first separation membrane assembly 31 is the same as the mixed gas supplied from the gas supply unit 36 ​​in Comparative Example 1. The pressure of the first permeate gas in the first separation membrane assembly 31 is -0.09 MPaG.

[0125] In Example 1, the recovery rate of the third gas (i.e., H2O) in the first separation membrane module 31 (i.e., the value obtained by dividing the amount of the third gas recovered in the first recovery section 33 by the amount of the third gas in the mixed gas) is 88.1%. Furthermore, the concentration of the third gas in the supply gas supplied to the second separation membrane module 32 is 0.05% by volume.

[0126] In Example 1, similarly to Comparative Example 1, CH4, as the second gas, was a recovered gas and was recovered in the third recovery section 35. The recovery rate of the recovered gas in Example 1 was 87.3%, which was higher than that in Comparative Example 1. The amount of recovered gas in Example 1 was 1.1, which was higher than that in Comparative Example 1. Therefore, the performance of the gas separation device 3 in Example 1 was "good", while the performance of the gas separation device in Comparative Example 1 was "poor". This performance difference is considered to be because, as described above, the third gas in the mixed gas is removed by the first separation membrane 310, and the decrease in the permeation performance of the second separation membrane 320 caused by the adsorption of the third gas is suppressed.

[0127] In Comparative Example 2, the type of the second separation membrane 320 is different, and the first gas in the mixed gas is different; otherwise, it is the same as Comparative Example 1. In Comparative Example 2, the second separation membrane 320 is a zeolite membrane composed of amorphous silica and MTN-type zeolite. The Si / Al ratio in the second separation membrane 320 is greater than 100.

[0128] The separation membrane composite 1, comprising a second separation membrane 320 consisting of amorphous silica and MTN-type zeolite, was manufactured as follows. First, a support 11, prepared similarly to Comparative Example 1, was immersed in an aqueous solution containing silica for pretreatment at 50°C for 1 hour, and then dried at 100°C. The silica concentration in the aqueous solution was 50% by mass. Next, the pretreated support 11 was immersed in a raw material solution for hydrothermal synthesis to form a second separation membrane 320 consisting of amorphous silica mixed with MTN-type zeolite particles. The hydrothermal synthesis time was 8 hours, and the hydrothermal synthesis temperature was 180°C. In preparing the raw material solution, 6.28 g of a 30% by mass tetramethylammonium hydroxide solution (manufactured by SACHEM) was mixed with 146.8 g of distilled water. Next, approximately 30% by mass of silica sol (trade name: SNOWTEXS, manufactured by Nissan Chemical Co., Ltd.) 14.8g was added, and the mixture was stirred with a magnetic stirrer (room temperature, 30 minutes) to obtain a raw material solution. The hydrothermally synthesized second separation membrane 320 and support 11 were immersed in a post-treatment solution for 1 day for post-treatment. This post-treatment solution was prepared by mixing sodium hydroxide in distilled water and adjusting the pH to above 9. Then, the second separation membrane 320 and support 11 were washed with distilled water, dried at 80°C for 12 hours, and then kept at 450°C for 50 hours to remove SDA by combustion, thereby obtaining the separation membrane composite 1.

[0129] In Comparative Example 2, the first gas in the gas mixture is H2. The composition of this gas mixture (H2 / CH4 / H2O) is 50 vol% / 49.6 vol% / 0.4 vol%. The pressure and temperature of the gas mixture supplied from the gas supply unit 36 ​​are 0.5 MPaG and 30°C, respectively. The pressure of the second permeate gas in the second separation membrane assembly 32 is 0 MPaG.

[0130] In Comparative Example 2, the first separation membrane assembly 31 was omitted as described above; therefore, the third gas was not recovered in the first separation membrane assembly 31. Consequently, the concentration of the third gas in the supply gas supplied to the second separation membrane assembly 32 was the same as the concentration in the aforementioned mixed gas, which was 0.4% by volume.

[0131] In Comparative Example 2, CH4, as the second gas, is the gas to be recovered (i.e., the recovered gas) in the second separation membrane assembly 32. Therefore, this recovered gas is recovered in the third recovery section 35 as the second non-permeable gas in the second separation membrane assembly 32. The "recovery rate" and "amount of recovered gas" in Table 2 are calculated in the same manner as in Comparative Example 1. The recovery rate of the recovered gas is 75.0%. In Comparative Example 2, Example 2, and Example 3, the amount of recovered gas in Comparative Example 2 is set as a baseline (i.e., 1) and expressed as a ratio. Therefore, the amount of recovered gas in Comparative Example 2 is 1.

[0132] In Example 2, a first separation membrane assembly 31 is provided; otherwise, it is the same as in Comparative Example 2. In Example 2, the first separation membrane 310 in the first separation membrane assembly 31 is a zeolite membrane composed of LTA-type zeolite, similar to that in Example 1. The Si / Al ratio in the first separation membrane 310 is 2.

[0133] In Example 2, the mixed gas supplied from the gas supply unit 36 ​​to the first separation membrane assembly 31 is the same as the mixed gas supplied from the gas supply unit 36 ​​in Comparative Example 2. The pressure of the first permeate gas in the first separation membrane assembly 31 is -0.09 MPaG.

[0134] In Example 2, the recovery rate of the third gas (i.e., H2O) in the first separation membrane module 31 was 88.1%. Furthermore, the concentration of the third gas in the supply gas supplied to the second separation membrane module 32 was 0.05% by volume.

[0135] In Example 2, similarly to Comparative Example 2, CH4, as the second gas, was a recovered gas and was recovered in the third recovery section 35. The recovery rate of the recovered gas in Example 2 was 88.0%, which was higher than that in Comparative Example 2. The amount of recovered gas in Example 2 was 2.7, which was also higher than that in Comparative Example 2. Therefore, the performance of the gas separation device 3 in Example 2 was rated as "good," while the performance of the gas separation device in Comparative Example 2 was rated as "poor." This performance difference is considered to be because, as described above, the third gas in the mixed gas is removed by the first separation membrane 310, and the decrease in the permeation performance of the second separation membrane 320 caused by the adsorption of the third gas is suppressed.

[0136] In Example 3, the type of the first separation membrane 310 is different; otherwise, it is the same as in Example 2. In Example 3, the first separation membrane 310 in the first separation membrane assembly 31 is a zeolite membrane composed of CHA-type zeolite. The Si / Al ratio in the first separation membrane 310 is 20.

[0137] The separation membrane composite 1, comprising a first separation membrane 310 as a CHA-type zeolite membrane, is manufactured in the following order. The feed solution for the first separation membrane 310 is prepared based on the method for preparing the membrane synthesis solution described in Japanese Patent Application Publication No. 2011-16123. Specifically, the feed solution is a liquid obtained by mixing silica sol (industrially produced "Cataloid SI-30" through catalytic chemical synthesis) and a 50% aqueous solution of aluminum nitrate (Al(NO3)3) at a Si / Al ratio of 20 in the first separation membrane 310 after hydrothermal synthesis. Next, a support 11 with CHA-type zeolite seed crystals attached is immersed in this feed solution, and heating (hydrothermal synthesis) of the feed solution is initiated. This hydrothermal synthesis is carried out at 120°C for 10 days. After hydrothermal synthesis, the first separation membrane 310 and the support 11 are cooled, thoroughly cleaned, and then dried at 70°C for 16 hours. Then, the first separation membrane 310 and the support 11 were fired at 550°C for 10 hours.

[0138] In Example 3, the recovery rate of the third gas (i.e., H2O) in the first separation membrane module 31 was 88.1%. Furthermore, the concentration of the third gas in the supply gas supplied to the second separation membrane module 32 was 0.05% by volume.

[0139] In Example 3, similar to Comparative Example 2 and Example 2, CH4, as the second gas, was recovered as a recycled gas and was recovered in the third recovery section 35. The recovery rate of the recycled gas in Example 3 was 88.0%, which was increased compared to Comparative Example 2. The amount of recycled gas in Example 3 was 2.7, which was increased compared to Comparative Example 2. Therefore, the performance of the gas separation device 3 in Example 3 was rated as "good". This is believed to be because, as described above, the third gas in the mixed gas is removed by the first separation membrane 310, and the decrease in the permeation performance of the second separation membrane 320 caused by the adsorption of the third gas is suppressed.

[0140] In Comparative Example 3, the second and third gases in the gas mixture are different; otherwise, it is the same as Comparative Example 2. In Comparative Example 3, the second and third gases in the gas mixture are N2 and NH3, respectively. The composition (H2 / N2 / NH3) of the gas mixture is 50% by volume / 49.6% by volume / 0.4% by volume. The pressure and temperature of the gas mixture supplied from the gas supply unit 36 ​​are 0.5 MPaG and 30°C, respectively. The pressure of the second permeate gas in the second separation membrane assembly 32 is 0 MPaG.

[0141] In Comparative Example 3, the first separation membrane assembly 31 was omitted as described above; therefore, the third gas was not recovered in the first separation membrane assembly 31. Consequently, the concentration of the third gas in the supply gas supplied to the second separation membrane assembly 32 was the same as the concentration in the aforementioned mixed gas, which was 0.4% by volume.

[0142] In Comparative Example 3, H2, as the first gas, is the gas to be recovered (i.e., the recovered gas) in the second separation membrane assembly 32. Therefore, this recovered gas is recovered in the second recovery section 34 as the second permeate gas in the second separation membrane assembly 32. The "Recovery Rate" and "Amount of Recovered Gas" in Table 2 represent: the area of ​​the second separation membrane 320 required to achieve a purity of 90% (i.e., a concentration of 90% by volume) in the second permeate gas, the recovery rate of the recovered gas recovered using the second separation membrane 320 with that area, and the amount of recovered gas recovered. The recovery rate of the recovered gas (i.e., the amount of recovered gas recovered in the second recovery section 34 divided by the amount of recovered gas in the mixed gas) is 85.6%. In Comparative Example 3 and Example 4, regarding the amount of recovered gas, the amount of recovered gas in Comparative Example 3 is set as a baseline (i.e., 1), expressed as a ratio. Therefore, the amount of recovered gas in Comparative Example 3 is 1.

[0143] In Example 4, a first separation membrane assembly 31 is provided, otherwise it is the same as in Comparative Example 3. In Example 4, the first separation membrane 310 in the first separation membrane assembly 31 is a zeolite membrane composed of CHA-type zeolite, just like in Example 3. The Si / Al ratio in the first separation membrane 310 is 20.

[0144] In Example 4, the mixed gas supplied from the gas supply unit 36 ​​to the first separation membrane assembly 31 is the same as the mixed gas supplied from the gas supply unit 36 ​​in Comparative Example 3. The pressure of the first permeate gas in the first separation membrane assembly 31 is -0.09 MPaG.

[0145] In Example 4, the recovery rate of the third gas (i.e., NH3) in the first separation membrane module 31 was 82.5%. Furthermore, the concentration of the third gas in the supply gas supplied to the second separation membrane module 32 was 0.1% by volume.

[0146] In Example 4, similarly to Comparative Example 3, H2, as the first gas, was the recovered gas and was recovered in the second recovery section 34. The recovery rate of the recovered gas in Example 4 was 40.2%. This is believed to be because, in the first separation membrane assembly 31, the first gas (H2) in the mixed gas permeates through the first separation membrane 310 and is recovered by the first recovery section 33. The amount of recovered gas in Example 4 was 7.6, which is increased compared to Comparative Example 3. Therefore, the performance of the gas separation device 3 in Example 4 is "good", while the performance of the gas separation device in Comparative Example 3 is "poor". This performance difference is believed to be because, as described above, the third gas in the mixed gas is removed by the first separation membrane 310, and the decrease in the permeation performance of the second separation membrane 320 caused by the adsorption of the third gas is suppressed.

[0147] Various modifications can be made to the gas separation device 3 and the gas separation method described above.

[0148] In the gas separation device 3 of the above example, one first separation membrane 310 and one second separation membrane 320 are provided. However, multiple first separation membranes 310 and / or second separation membranes 320 may also be provided.

[0149] For example, Figure 7 In the illustrated gas separation device 3a, a second separation membrane assembly 32a with the same structure as the second separation membrane assembly 32 is provided between the second separation membrane assembly 32 and the third recovery unit 35. The two second separation membrane assemblies 32 and 32a are connected in series in the gas separation device 3a. In the gas separation device 3a, the second non-permeable gas discharged from the second separation membrane assembly 32 on the upstream side (i.e., the side closer to the first separation membrane assembly 31) is supplied to the second separation membrane assembly 32a via the second non-permeable gas flow path 322. In the second separation membrane assembly 32a, the first gas remaining in the second non-permeable gas permeates through the second separation membrane 320, thereby separating from the second non-permeable gas. The gas that has permeated through the second separation membrane 320 of the second separation membrane assembly 32a is guided to the second recovery unit 34 via the second permeable gas flow path 321a. On the other hand, the gas that has not permeated through the second separation membrane 320 of the second separation membrane assembly 32a is guided to the third recovery unit 35 via the second non-permeable gas flow path 322a.

[0150] or, Figure 8 In the illustrated gas separation device 3b, a second separation membrane assembly 32b having the same structure as the second separation membrane assembly 32 is arranged in parallel with the second separation membrane assembly 32 between the first separation membrane assembly 31 and the third recovery unit 35. The two second separation membrane assemblies 32 and 32b are connected in parallel in the gas separation device 3b. In the gas separation device 3b, a first non-permeable gas discharged from the first separation membrane assembly 31 is supplied in parallel to the second separation membrane assembly 32 and the second separation membrane assembly 32b. In the second separation membrane assembly 32b, similarly to the second separation membrane assembly 32, a first gas in the first non-permeable gas permeates through the second separation membrane 320 and is separated from the first non-permeable gas. The gas that has permeated through the second separation membrane 320 of the second separation membrane assembly 32b is guided to the second recovery unit 34 via the second permeable gas flow path 321b. On the other hand, the gas that has not permeated through the second separation membrane 320 of the second separation membrane assembly 32b is guided to the third recovery unit 35 via the second non-permeable gas flow path 322b.

[0151] In the gas separation devices 3, 3a, and 3b described above, the first separation membrane 310 and / or the second separation membrane 320 can be a laminated membrane obtained by stacking multiple zeolite membranes formed from different types of zeolites in the thickness direction, or it can be a zeolite membrane that has undergone surface treatment. In addition, in the gas separation devices 3, 3a, and 3b, a membrane of a different type from the zeolite membrane (e.g., an inorganic membrane other than a zeolite membrane, such as a silica membrane) can be provided on the first separation membrane 310 and / or the second separation membrane 320.

[0152] In the gas separation devices 3, 3a, and 3b described above, the first separation membrane 310 and / or the second separation membrane 320 do not necessarily need to be zeolite membranes; they can be various separation membranes (such as inorganic membranes other than zeolite membranes).

[0153] When the first separation membrane 310 is a zeolite membrane, the maximum number of elements in the zeolite rings constituting the first separation membrane 310 can be greater than 8. Similarly, when the second separation membrane 320 is a zeolite membrane, the maximum number of elements in the zeolite rings constituting the second separation membrane 320 can be greater than 8.

[0154] The Si / Al ratio in the first separation membrane 310 can be greater than 100. Conversely, the Si / Al ratio in the second separation membrane 320 can be less than 100.

[0155] The structures of the first separation membrane assembly 31 and the second separation membrane assembly 32 are not necessarily limited to the examples described above, and various modifications can be made. For example, in the first separation membrane assembly 31, the first separation membrane 310 does not necessarily need to be supported on the support body 11, and can be arranged in various ways. In addition, in the second separation membrane assembly 32, the second separation membrane 320 does not necessarily need to be supported on the support body 11, and can be arranged in various ways.

[0156] The first separation membrane 310 and the second separation membrane 320 do not necessarily need to be housed in the outer shell 22 of the first separation membrane assembly 31 and the outer shell 22 of the second separation membrane assembly 32 respectively; they can be housed in one outer shell.

[0157] The dynamic molecular diameter of the first gas can be greater than 0.3 nm or greater than 0.4 nm. The dynamic molecular diameter of the second gas can be greater than 0.4 nm.

[0158] The third gas can be a polar gas other than water and ammonia. Furthermore, the concentration of the third gas in the mixed gas supplied from the gas supply unit 36 ​​can be higher than 1% by volume.

[0159] In the gas separation device 3, a pretreatment device, such as an impurity remover, can be provided between the gas supply unit 36 ​​and the first separation membrane assembly 31, or between the first separation membrane assembly 31 and the second separation membrane assembly 32, to adsorb and remove a third gas from the mixed gas. In this case, since the pretreatment device is designed with the separation and removal of the third gas in the first separation membrane assembly 31 as the premise, the pretreatment device can be miniaturized. As a result, the large-scale construction of equipment related to the separation of the mixed gas can be prevented.

[0160] The components in the above-described embodiments and their variations can be appropriately combined as long as they do not contradict each other.

[0161] Although the invention has been described in detail, the above description is exemplary and not limiting. Therefore, it can be said that numerous modifications and solutions can be adopted without departing from the scope of the invention.

[0162] Industrial availability

[0163] This invention can be used for the separation of various mixed gases.

[0164] Explanation of reference numerals in the attached figures

[0165] 1 Separation Membrane Complex

[0166] 3. Gas separation devices, 3a, 3b

[0167] 310 First Separation Membrane

[0168] 320 Second Separation Membrane

[0169] 36 Gas Supply Department

[0170] Steps S11~S12

Claims

1. A gas separation apparatus for separating a mixture of gases comprising at least a first gas, a second gas, and a third gas as a polar gas. The gas separation device is characterized by having: A gas supply unit that supplies the mixed gas; A first separation membrane, wherein the permeability of the third gas is higher than that of the first gas and the second gas, allows the third gas to pass through and be removed from the mixed gas supplied from the gas supply unit; and A second separation membrane, wherein the permeability of the first gas is higher than that of the second gas, is supplied with a non-permeable gas in the mixed gas that does not pass through the first separation membrane, thereby allowing the first gas in the non-permeable gas to pass through and be separated.

2. The gas separation device according to claim 1, characterized in that, The ratio of silicon content to aluminum content in the first separation membrane is less than 100.

3. The gas separation device according to claim 1, characterized in that, The ratio of silicon content to aluminum content in the second separation membrane is greater than 100.

4. The gas separation device according to claim 1, characterized in that, The concentration of the third gas in the mixed gas supplied from the gas supply unit is less than 1% by volume.

5. The gas separation device according to claim 1, characterized in that, The third gas is water or ammonia.

6. The gas separation device according to claim 1, characterized in that, The dynamic molecular diameters of the first gas and the second gas are both less than 0.4 nm.

7. The gas separation device according to claim 6, characterized in that, The dynamic molecular diameter of the first gas is less than 0.3 nm.

8. The gas separation apparatus according to any one of claims 1 to 7, characterized in that, The first separation membrane is a zeolite membrane.

9. A gas separation method for separating a mixture of gases comprising at least a first gas, a second gas, and a third gas as a polar gas. The gas separation method is characterized by including the following steps: a) The mixed gas is supplied to a first separation membrane, the permeability of which is higher than that of the first gas and the second gas, so that the third gas passes through and is removed; and b) Supply a non-permeable gas from the mixed gas that does not pass through the first separation membrane to a second separation membrane, which has a higher permeability to the first gas than to the second gas, so that the first gas in the non-permeable gas passes through and is separated.

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