Mixed gas separation method

Abstract

To improve a mixed gas separation performance.SOLUTION: A plurality of first cells (111a) are each opened in longitudinal both ends and are provided with a separation membrane (12) in an inside surface thereof. Second cells (111b) are opened in longitudinal both ends. In both end portions in the longitudinal direction of a support body (11), a slit (117) extending from an outside surface (112) of the support body (11) to the second cell (111b) is further provided. Mixed gas is supplied to one end surface (114) in the longitudinal direction of a separation membrane composite (1). Sweep gas is supplied to the slit (117) opened in the outside surface (112) of the support body (11) in one end portion of the longitudinal direction and flows through the second cell (111b). The sweep gas is discharged from the slit (117) opened in the outside surface (112) of the support body (11) in the other end portion of the longitudinal direction with a pressure loss of 100 kPa or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for separating a mixed gas. [Reference to Related Application] This application claims the benefit of priority from Japanese Patent Application JP2022-017639, filed February 8, 2022, the entire disclosure of which is incorporated herein by reference. [Background technology]

[0002] Currently, various research and development efforts are being conducted on the separation and adsorption of specific molecules using separation membranes such as zeolite membranes.

[0003] For example, WO 2016 / 104048 (Reference 1) and WO 2016 / 104049 (Reference 2) disclose gas separation modules that separate specific gases from a mixed gas using a gas separation membrane structure in which a gas separation membrane is formed on a porous support. In these gas separation modules, the internal space of a housing is divided into two spaces by a plate-like gas separation membrane structure, and a mixed gas is supplied to one space (i.e., the supply space). A specific gas in the mixed gas (hereinafter referred to as the "target gas to permeate") permeates through the gas separation membrane structure and moves to the other space (i.e., the permeate space) where it is separated from the mixed gas. In these gas separation modules, when the concentration of the target gas to permeate in the mixed gas is low, a sweep gas is passed through the permeate space to reduce the partial pressure of the target gas to permeate in the permeate space, thereby promoting permeation of the target gas.

[0004] A monolithic separation membrane composite is known as one type of separation membrane structure that separates a specific gas from a mixed gas. In this separation membrane composite, multiple cells that penetrate a cylindrical porous support in the longitudinal direction are arranged in a matrix, and the separation membrane is provided on the inner surface of the cell. This increases the separation membrane area per unit volume of the separation membrane composite, thereby improving the separation performance of the separation membrane composite.

[0005] In a mixed gas separation device using such a monolithic separation membrane composite, when separating a mixed gas with a low concentration of the target gas to be permeated, it is possible to flow a sweep gas into the space outside the columnar porous support. However, in cells that are far from the space through which the sweep gas flows (for example, cells located near the center in a cross section perpendicular to the longitudinal direction of the porous support), the permeation-promoting effect of the sweep gas is not very strong, which limits the improvement in the separation performance of the mixed gas separation device. Summary of the Invention

[0006] The present invention is directed to a mixed gas separation method, and aims to improve the performance of separating mixed gases.

[0007] The present invention is also directed to a mixed gas separation method. A preferred embodiment of the mixed gas separation method of the present invention comprises the steps of: (a) preparing a separation membrane composite including a separation membrane and a porous support; and (b) supplying a mixed gas containing multiple gases to the separation membrane and separating a highly permeable gas from the mixed gas by permeating the separation membrane. The support is cylindrical and extends longitudinally. The support is provided with a plurality of cells arranged in a matrix in the vertical and horizontal directions. The plurality of cells includes a plurality of membrane formation cells, each of which is open at both longitudinal ends and has the separation membrane provided on its inner surface, and discharge cells, each of which is closed at both longitudinal ends. Side flow paths are further provided at both longitudinal ends of the support, extending from the outer surface of the support to the discharge cells. In step b), the mixed gas is supplied to one longitudinal end face of the separation membrane composite, and the sweep gas is supplied to the side flow path that opens onto the outer surface of the support at the one longitudinal end, flows through the discharge cell, and is discharged from the side flow path that opens onto the outer surface of the support at the other longitudinal end with a pressure loss of 100 kPa or less. Preferably, a catalyst for promoting a chemical reaction of the source materials is disposed in each of the film-forming cells, and the mixed gas is a gas produced by chemically reacting the source materials in the presence of the catalyst.

[0008] The above and other objects, features, aspects and advantages will become more apparent from the following detailed description of the invention which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of a separation device according to a first embodiment. [Figure 2] FIG. 2 is a perspective view of a separation membrane composite. [Figure 3] FIG. 2 is a view showing an end face of a separation membrane composite. [Figure 4] FIG. 2 is an enlarged view of a portion of a longitudinal cross section of a separation membrane composite. [Figure 5] FIG. 2 is a view showing an end face of a separation membrane composite. [Figure 6] FIG. 1 is a diagram showing a flow of manufacturing a separation membrane composite. [Figure 7] FIG. [Figure 8] FIG. 1 is a diagram showing the flow of separation of a mixed gas. [Figure 9] FIG. [Figure 10] FIG. 10 is a side view of a separation device according to a second embodiment. [Figure 11] FIG. [Figure 12] FIG. 1 is a side view of a mixed gas separation system. [Figure 13] FIG. 1 is a cross-sectional view of a membrane reactor. [Figure 14] FIG. 1 is a diagram showing a method of operating a membrane reactor. [Figure 15] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] 1 is a side view showing a mixed gas separation apparatus 2 according to a first embodiment of the present invention. The mixed gas separation apparatus 2 (hereinafter also simply referred to as "separation apparatus 2") is an apparatus that separates a specific type of gas from a mixed gas containing multiple types of gases.

[0011] The separation device 2 includes a separation membrane composite 1 and a housing 22 that houses the separation membrane composite 1. In Figure 1, the housing 22 of the separation device 2 is depicted in cross section to show the internal configuration of the housing 22. In the separation device 2, a gas with high permeability in a mixed gas is separated from the mixed gas by passing the gas through the separation membrane composite 1.

[0012] Fig. 2 is a perspective view of the separation membrane composite 1. Fig. 2 also shows part of the internal structure of the separation membrane composite 1. Fig. 3 is a diagram showing one end surface 114 in the longitudinal direction (i.e., approximately the left-right direction in Fig. 2) of the separation membrane composite 1. Fig. 4 is an enlarged view of part of the longitudinal cross section of the separation membrane composite 1, showing the vicinity of cells 111, which will be described later.

[0013] The separation membrane composite 1 includes a porous support 11 and a separation membrane 12 (see FIG. 4) formed on the support 11. In FIG. 4, the separation membrane 12 is indicated by diagonal lines. The support 11 is a porous member that is permeable to gas and liquid. In the example shown in FIG. 2, the support 11 is a monolithic support having an integrally molded, continuous columnar body with a plurality of through-holes 111 (hereinafter also referred to as "cells 111") extending in the longitudinal direction of the body. In the support 11, a plurality of cells 111 are formed (i.e., partitioned) by porous partition walls. In the example shown in FIG. 2, the outer shape of the support 11 is approximately cylindrical. The cross-sectional shape of each cell 111 perpendicular to the longitudinal direction is, for example, approximately circular. Note that the term "approximately circular" is a concept that includes not only a perfect circle but also an ellipse or a distorted circle. The cross-sectional shape of each cell 111 is preferably, but not necessarily, a perfect circle. In FIG. 2, the diameter of the cells 111 is drawn larger than in reality, and the number of the cells 111 is drawn smaller than in reality (the same applies to FIG. 3).

[0014] The multiple cells 111 include first cells 111a and second cells 111b. In the example shown in FIGS. 2 and 3, the first cells 111a and the second cells 111b have approximately the same shape. At both longitudinal end faces 114 of the support body 11, the openings of the second cells 111b are plugged with plugging members 115. In other words, the second cells 111b are closed at both longitudinal ends. In FIGS. 2 and 3, the plugging members 115 are indicated by diagonal lines. On the other hand, at both longitudinal end faces 114 of the support body 11, the openings of the first cells 111a are not plugged and are open.

[0015] The above-mentioned separation membrane 12 (see FIG. 4) is disposed on the inner surface of each first cell 111a, which is open at both longitudinal ends. The separation membrane 12 is preferably provided so as to cover the entire inner surface of each first cell 111a. That is, the first cell 111a is a membrane cell on the inside of which the separation membrane 12 is provided. In the separation membrane composite 1, the second cell 111b does not have a separation membrane 12 provided on the inside. As will be described later, the second cell 111b is an exhaust cell used to exhaust the permeation gas that has permeated the separation membrane 12.

[0016] 2 and 3, the plurality of cells 111 are arranged in a matrix on the end surface 114 of the support 11 in the vertical direction (i.e., the up-and-down direction in FIG. 3) and the horizontal direction. In the following description, a group of cells 111 arranged in a row in the horizontal direction (i.e., the left-and-right direction in FIG. 3) is also referred to as a "cell row." The plurality of cells 111 include multiple rows of cell rows arranged in the vertical direction. In the example shown in FIG. 3, each row of cell rows is composed of multiple first cells 111a or multiple second cells 111b.

[0017] In the example shown in Fig. 3, in the multiple cell rows, a cell row of second cells 111b in one row (hereinafter also referred to as "second cell row 116b") and a cell row of first cells 111a in two rows (hereinafter also referred to as "first cell row 116a") are alternately arranged adjacent to each other in the vertical direction. In Fig. 3, each first cell row 116a and each second cell row 116b are indicated by being surrounded by a two-dot chain line (the same applies to Fig. 5 described later). The second cell row 116b is a plugged cell row in which both ends in the longitudinal direction are plugged.

[0018] The second cells 111b in the second cell row 116b are connected to each other by slits 117 (see FIG. 2) extending along the horizontal direction. The slits 117 extend to the outer surface 112 of the support 11 on both sides of the second cell row 116b in the horizontal direction, and the second cells 111b in the second cell row 116b are connected to the space outside the support 11 through the slits 117. In other words, the slits 117 are side flow passages that extend from the outer surface of the support 11 to the second cells 111b, laterally penetrate the second cell row 116b (i.e., the second cells 111b arranged in the horizontal direction), and reach the outer surface of the support 11. In other words, the slits 117 connect the second cells 111b in the second cell row 116b to portions of the outer surface of the support 11 on both sides of the second cell row 116b in the horizontal direction.

[0019] The cross-sectional shape of the slit 117 perpendicular to the horizontal direction is, for example, approximately rectangular. The cross-sectional shape of the slit 117 may be variously changed, such as approximately circular. The cross-sectional area of ​​the slit 117 is much larger than the cross-sectional area of ​​the pores of the support 11. The area of ​​the cross-section of the slit 117 perpendicular to the horizontal direction is, for example, 5 to 100 times the area of ​​the cross-section of the second cell 111b perpendicular to the longitudinal direction.

[0020] In the separation membrane composite 1, three slits 117 are provided near one longitudinal end of the support 11. Each slit 117 opens to the outer surface of the support 11 on both lateral sides, so six openings (hereinafter also referred to as "slit openings") are provided near the corresponding end on the outer surface of the support 11. In the example shown in FIG. 2, the six slit openings have approximately the same shape and are located at approximately the same longitudinal position. In the separation membrane composite 1, three slits 117 are also provided near the other longitudinal end of the support 11 (i.e., at a different longitudinal position from the three slits 117 described above), so that six slit openings are provided near the corresponding end on the outer surface of the support 11. The six slit openings also have approximately the same shape and are located at approximately the same longitudinal position. Note that the shapes and positions of some or all of the slit openings (the six slit openings described above) may be different near both longitudinal ends of the support 11.

[0021] The first cell row 116a is an open cell row with both longitudinal ends open, and is also a deposition cell row with a separation film 12 (see FIG. 4) provided inside. The two rows of first cells 111a adjacent to one side of the second cell row 116b in the vertical direction constitute an open cell row group. In other words, the open cell row group is the two rows of first cells 116a sandwiched between the two second cell rows 116b positioned closest to each other in the vertical direction.

[0022] The number of rows of the first cell rows 116a constituting the open cell row group is not limited to two and may be varied in various ways. Preferably, the number of rows of the first cell rows 116a constituting the open cell row group is one or more and six or less, and more preferably one or two. Figure 5 shows an example in which the number of rows of the first cell rows 116a constituting the open cell row group sandwiched between two second cell rows 116b is five.

[0023] Furthermore, the number of second cell rows 116b is not limited to three and may be one, two or more. Furthermore, in the separation membrane complex 1, the second cells 111b do not necessarily need to be arranged in the horizontal direction, and the second cells 111b may be arranged randomly. Alternatively, the number of second cells 111b provided in the separation membrane complex 1 may be one.

[0024] The length of the support 11 in the longitudinal direction is, for example, 100 mm to 2000 mm. The outer diameter of the support 11 is, for example, 5 mm to 300 mm. The distance between adjacent cells 111 (i.e., the thickness of the support 11 between the closest portions of the adjacent cells 111) is, for example, 0.3 mm to 10 mm. The surface roughness (Ra) of the inner surface of the first cell 111a of the support 11 is, for example, 0.1 μm to 5.0 μm, and preferably 0.2 μm to 2.0 μm. The area of ​​the cross section perpendicular to the longitudinal direction of each cell 111 is, for example, 2 mm 2 Over 300mm 2 The following is an example. As described above, when the cross section of each cell 111 is substantially circular, the diameter of the cross section is preferably 1.6 mm to 20 mm. The shapes and sizes of the support 11 and the cells 111 may be changed in various ways. For example, the shape of the cross section perpendicular to the longitudinal direction of the cells 111 may be substantially polygonal. The shapes and sizes of the first cells 111a and the second cells 111b may be different. Furthermore, the shapes and sizes of some or all of the first cells 111a may be different from each other, and the shapes and sizes of some or all of the second cells 111b may be different from each other.

[0025] Various substances (for example, ceramics or metals) can be used as the material of support 11, as long as they are chemically stable in the process of forming separation membrane 12 on the surface. In this embodiment, support 11 is formed of a ceramic sintered body. Examples of ceramic sintered bodies selected as the material of support 11 include alumina, silica, mullite, zirconia, titania, yttria, silicon nitride, and silicon carbide. In this embodiment, support 11 contains at least one of alumina, silica, and mullite.

[0026] The support 11 may contain an inorganic binder for binding aggregate particles of the ceramic sintered body, which may be at least one of titania, mullite, sinterable alumina, silica, glass frit, clay minerals, and sinterable cordierite.

[0027] The support 11 has a multilayer structure in which multiple layers with different average pore sizes are stacked in the thickness direction near the inner surface of each of the first cells 111a, which are open cells (i.e., near the separation membrane 12). In the example shown in FIG. 4, the support 11 includes a porous substrate 31, a porous intermediate layer 32 formed on the substrate 31, and a porous surface layer 33 formed on the intermediate layer 32. That is, the surface layer 33 is indirectly provided on the substrate 31 via the intermediate layer 32. The intermediate layer 32 is also provided between the substrate 31 and the surface layer 33. The surface layer 33 constitutes the inner surface of each of the first cells 111a of the support 11, and the separation membrane 12 is formed on the surface layer 33. The thickness of the surface layer 33 is, for example, 1 μm to 100 μm. The thickness of the intermediate layer 32 is, for example, 100 μm to 500 μm. The intermediate layer 32 and the surface layer 33 may or may not be provided on the inner surface of each second cell 111b. The intermediate layer 32 and the surface layer 33 may or may not be provided on the outer surface 112 and the end surface 114 of the support 11.

[0028] The average pore diameter of the surface layer 33 is smaller than the average pore diameter of the intermediate layer 32 and the average pore diameter of the substrate 31. The average pore diameter of the intermediate layer 32 is also smaller than the average pore diameter of the substrate 31. The average pore diameter of the substrate 31 is, for example, 1 μm or more and 70 μm or less. The average pore diameter of the intermediate layer 32 is, for example, 0.1 μm or more and 10 μm or less. The average pore diameter of the surface layer 33 is, for example, 0.005 μm or more and 2 μm or less. The average pore diameters of the substrate 31, intermediate layer 32, and surface layer 33 can be measured, for example, by a mercury porosimeter, a perm porometer, or a nanoperm porometer.

[0029] The surface layer 33, the intermediate layer 32, and the substrate 31 have substantially the same porosity. The porosity of the surface layer 33, the intermediate layer 32, and the substrate 31 is, for example, 15% or more and 70% or less. The porosity of the surface layer 33, the intermediate layer 32, and the substrate 31 can be measured by, for example, the Archimedes method, the mercury porosity method, or an image analysis method.

[0030] The substrate 31, intermediate layer 32, and surface layer 33 may be formed of the same material or different materials. For example, the substrate 31 and surface layer 33 contain Al2O3 as a main material. The intermediate layer 32 contains aggregate particles mainly made of Al2O3 and an inorganic binder mainly made of TiO2. In this embodiment, the aggregate particles of the substrate 31, intermediate layer 32, and surface layer 33 are formed substantially only from Al2O3. The substrate 31 may contain an inorganic binder such as glass.

[0031] The average particle size of the aggregate particles in the surface layer 33 is smaller than the average particle size of the aggregate particles in the intermediate layer 32. The average particle size of the aggregate particles in the intermediate layer 32 is also smaller than the average particle size of the aggregate particles in the base material 31. The average particle sizes of the aggregate particles in the base material 31, intermediate layer 32, and surface layer 33 can be measured by, for example, laser diffraction.

[0032] The plugging member 115 can be formed from the same material as the base material 31, the intermediate layer 32, and the surface layer 33. The porosity of the plugging member 115 is, for example, 15% to 70%.

[0033] As described above, the separation membrane 12 is formed on the inner surface of each first cell 111a, which is an open cell (i.e., on the surface layer 33), and covers the inner surface over substantially the entire surface. The separation membrane 12 is a porous membrane having micropores. The separation membrane 12 separates a specific substance from a mixture of multiple types of substances.

[0034] Separation membrane 12 is preferably an inorganic membrane formed from an inorganic material, more preferably a zeolite membrane, silica membrane, carbon membrane, or MOF (metal-organic composite) membrane, and particularly preferably a zeolite membrane. A zeolite membrane is at least a membrane of zeolite formed on the surface of support 11, and does not include an organic membrane in which zeolite particles are simply dispersed. In this embodiment, separation membrane 12 is a zeolite membrane. Separation membrane 12 may also be a zeolite membrane containing two or more types of zeolites with different structures and compositions.

[0035] The thickness of the separation membrane 12 is, for example, 0.05 μm or more and 50 μm or less, preferably 0.1 μm or more and 20 μm or less, and more preferably 0.5 μm or more and 10 μm or less. Increasing the thickness of the separation membrane 12 improves separation performance. Reducing the thickness of the separation membrane 12 increases the permeation rate. The surface roughness (Ra) of the separation membrane 12 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. The pore diameter of the separation membrane 12 is, for example, 0.2 nm to 1 nm. The pore diameter of the separation membrane 12 is smaller than the average pore diameter of the surface layer 33 of the support 11.

[0036] When the maximum number of rings in the zeolite constituting the separation membrane 12 is n, the minor axis of the n-membered ring pore is defined as the pore diameter of the separation membrane 12. When the zeolite has multiple types of n-membered ring pores with the same n, the minor axis of the n-membered ring pore with the largest minor axis is defined as the pore diameter of the separation membrane 12. Note that an n-membered ring refers to a portion in which the number of oxygen atoms constituting the skeleton forming the pore is n, and each oxygen atom is bonded to a T atom (described below) to form a ring structure. Note that an n-membered ring refers to a ring that forms a through-hole (channel), and does not include a ring that does not form a through-hole. An n-membered ring pore is a pore formed by an n-membered ring. From the viewpoint of improving selectivity, the maximum number of rings in the zeolite constituting the separation membrane 12 is preferably 8 or less (for example, 6 or 8).

[0037] The pore size of the separation membrane 12 is primarily determined by the framework structure of the zeolite.<URL:http: / / www.iza-structure.org / databases / > The values ​​can be obtained from the values ​​disclosed in

[0038] The type of zeolite constituting separation membrane 12 is not particularly limited, and may be, for example, AEI, AEN, AFN, AFV, AFX, BEA, CHA, DDR, ERI, ETL, FAU (X, Y), GIS, IHW, LEV, LTA, LTJ, MEL, MFI, MOR, PAU, RHO, SOD, or SAT zeolite. When the zeolite is an eight-membered ring zeolite, it may be, for example, AEI, AFN, AFV, AFX, CHA, DDR, ERI, ETL, GIS, IHW, LEV, LTA, LTJ, RHO, or SAT zeolite. In this embodiment, the type of zeolite constituting separation membrane 12 is DDR zeolite.

[0039] The zeolite constituting the separation membrane 12 contains at least one of silicon (Si), aluminum (Al), and phosphorus (P) as a T atom (i.e., an atom located at the center of an oxygen tetrahedron (TO4) constituting the zeolite). Zeolites constituting the separation membrane 12 include zeolites in which the T atom is Si only or contains Si and Al, AlPO zeolites in which the T atom is Al and P, SAPO zeolites in which the T atom is Si, Al, and P, MAPSO zeolites in which the T atom is magnesium (Mg), Si, Al, and P, and ZnAPSO zeolites in which the T atom is zinc (Zn), Si, Al, and P. Some of the T atoms may be substituted with other elements. The zeolite constituting the separation membrane 12 may contain an alkali metal. The alkali metal is, for example, sodium (Na) or potassium (K).

[0040] When the zeolite constituting separation membrane 12 contains Si atoms and Al atoms, the Si / Al ratio in the zeolite constituting separation membrane 12 is, for example, 1 or more and 100,000 or less. The Si / Al ratio is the molar ratio of Si element to Al element contained in the zeolite constituting separation membrane 12. The Si / Al ratio is preferably 5 or more, more preferably 20 or more, and even more preferably 100 or more; the higher the Si / Al ratio, the higher the heat resistance and acid resistance of separation membrane 12, which is preferable. The Si / Al ratio can be adjusted by adjusting the compounding ratio of the Si source and Al source in the raw material solution, which will be described later.

[0041] When the partial pressure difference of CO2 between the supply side and the permeation side of the separation membrane 12 is 1.5 MPa, the permeation rate (permeance) of CO2 through the separation membrane 12 at 20°C to 400°C is, for example, 100 nmol / m 2 sec·Pa or more, and the ratio of the CO2 permeation rate / CH4 leakage rate (permeance ratio) of the separation membrane 12 at 20°C to 400°C is, for example, 25 or more. When the partial pressure difference of CO2 is 0.2 MPa, the permeance is, for example, 200 nmol / m 2 ·sec·Pa or more, and the permeance ratio is, for example, 60 or more.

[0042] Next, with reference to FIG. 6, an example of the flow of manufacturing the separation membrane composite 1 will be described. When manufacturing the separation membrane composite 1, first, seed crystals to be used in forming the separation membrane 12 are generated and prepared (step S11). In generating the seed crystals, raw materials such as a Si source and a structure-directing agent (hereinafter also referred to as "SDA") are dissolved or dispersed in a solvent to prepare a raw material solution of the seed crystals. Next, hydrothermal synthesis is performed on the raw material solution, and the obtained crystals are washed and dried to obtain zeolite powder. The zeolite powder may be used as the seed crystals as is, or the seed crystals may be obtained by processing the powder by pulverization or the like.

[0043] Next, a dispersion liquid in which seed crystals are dispersed in a solvent (e.g., water) is brought into contact with the inner surfaces of the first cells 111a of the support 11, thereby attaching the seed crystals in the dispersion liquid to the inner surfaces of the first cells 111a (step S12). Note that the seed crystals may also be attached to the inner surfaces of the first cells 111a by other methods. When step S12 is performed, for example, both longitudinal ends of the second cells 111b are plugged in advance.

[0044] Next, the support 11 with the seed crystal attached thereto is immersed in a raw material solution. The raw material solution is prepared by dissolving, for example, a Si source and SDA in a solvent. The solvent for the raw material solution is, for example, water or an alcohol such as ethanol. The SDA contained in the raw material solution is, for example, an organic substance. For example, 1-adamantanamine can be used as the SDA.

[0045] Then, zeolite is grown by hydrothermal synthesis using the seed crystals as nuclei, thereby forming separation membrane 12 on the inner surface of each first cell 111a of support 11 (step S13). The temperature during hydrothermal synthesis is preferably 120 to 200°C, for example, 160°C. The hydrothermal synthesis time is preferably 5 to 100 hours, for example, 30 hours.

[0046] After the hydrothermal synthesis is complete, the support 11 and the separation membrane 12 are washed with pure water. After the washing, the support 11 and the separation membrane 12 are dried, for example, at 80°C. After the support 11 and the separation membrane 12 are dried, the separation membrane 12 is heat-treated (i.e., calcined) to almost completely burn off the SDA in the separation membrane 12 and penetrate the micropores in the separation membrane 12. This results in the above-described separation membrane composite 1 (step S14).

[0047] Next, separation of a mixed gas using the separation membrane composite 1 will be described with reference to Figures 1, 7, and 8. Figure 7 is a cross-sectional view showing a separation device 2. To facilitate understanding of the drawing, Figure 7 shows a simplified conceptual cross-section of the separation membrane composite 1. Figure 8 is a diagram showing the flow of separation of a mixed gas by the separation device 2.

[0048] In the separation device 2, a mixed gas containing multiple types of gases is supplied to the separation membrane composite 1, and highly permeable substances in the mixed gas are separated from the mixed gas by permeating through the separation membrane composite 1. Separation in the separation device 2 may be performed, for example, for the purpose of extracting a highly permeable gas (hereinafter also referred to as a "highly permeable gas") from the mixed gas, or for the purpose of concentrating a lowly permeable gas (hereinafter also referred to as a "lowly permeable gas").

[0049] The mixed gas may contain one or more substances selected from the group consisting of hydrogen (H), helium (He), nitrogen (N), oxygen (O), water (H), O, carbon monoxide (CO), carbon dioxide (CO), nitrogen oxides, ammonia (NH), sulfur oxides, hydrogen sulfide (H), sulfur fluoride, mercury (Hg), arsine (AsH), hydrogen cyanide (HCN), carbonyl sulfide (COS), C to C hydrocarbons, organic acids, alcohols, mercaptans, esters, ethers, ketones, and aldehydes. The highly permeable gas may be one or more substances selected from the group consisting of CO, NH, and H. The mixed gas and highly permeable gas may be substances other than those listed above.

[0050] Nitrogen oxides are compounds of nitrogen and oxygen. Examples of the nitrogen oxides include nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (also called dinitrogen monoxide) (N2O), dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4), dinitrogen pentoxide (N2O5), etc. X It is a substance called NOX.

[0051] Sulfur oxides are compounds of sulfur and oxygen. Examples of sulfur oxides include sulfur dioxide (SO2), sulfur trioxide (SO3), and other sulfur compounds. X It is a substance called SOX.

[0052] Sulfur fluoride is a compound of fluorine and sulfur. The sulfur fluoride may be, for example, disulfur difluoride (FSSF, S=SF), sulfur difluoride (SF), sulfur tetrafluoride (SF), sulfur hexafluoride (SF), or disulfur decafluoride (SF). 10 ) etc.

[0053] C1-C8 hydrocarbons are hydrocarbons with one or more carbon atoms and eight or less. C3-C8 hydrocarbons may be straight-chain compounds, branched-chain compounds, or cyclic compounds. C2-C8 hydrocarbons may be saturated hydrocarbons (i.e., those without double or triple bonds in the molecule) or unsaturated hydrocarbons (i.e., those with double and / or triple bonds in the molecule). Examples of C1-C4 hydrocarbons include methane (CH4), ethane (C2H6), ethylene (C2H4), propane (C3H8), propylene (C3H6), normal butane (CH3(CH2)2CH3), isobutane (CH(CH3)3), 1-butene (CH2=CHCH2CH3), 2-butene (CH3CH=CHCH3), and isobutene (CH2=C(CH3)2).

[0054] The organic acid may be a carboxylic acid or a sulfonic acid. Examples of the carboxylic acid include formic acid (CHO), acetic acid (CHO), oxalic acid (CHO), acrylic acid (CHO), or benzoic acid (CHCOOH). Examples of the sulfonic acid include ethanesulfonic acid (CHOS). The organic acid may be a chain compound or a cyclic compound.

[0055] The alcohols mentioned above are, for example, methanol (CH3OH), ethanol (C2H5OH), isopropanol (2-propanol) (CH3CH(OH)CH3), ethylene glycol (CH2(OH)CH2(OH)) or butanol (C4H9OH).

[0056] Mercaptans are organic compounds with hydrogenated sulfur (SH) at the end, also known as thiols or thioalcohols. Examples of the mercaptans include methyl mercaptan (CHSH), ethyl mercaptan (CHSH), and 1-propanethiol (CHSH).

[0057] The esters mentioned above are, for example, formates or acetates.

[0058] The ethers mentioned above are, for example, dimethyl ether ((CH3)2O), methyl ethyl ether (C2H5OCH3) or diethyl ether ((C2H5)2O).

[0059] The ketone may be, for example, acetone ((CH3)2CO), methyl ethyl ketone (C2H5COCH3), or diethyl ketone ((C2H5)2CO).

[0060] The aldehydes mentioned above are, for example, acetaldehyde (CH3CHO), propionaldehyde (C2H5CHO) or butanal (butyraldehyde) (C3H7CHO).

[0061] As shown in FIGS. 1 and 7, the separation device 2 includes a separation membrane composite 1, a sealing unit 21, a housing 22, and three sealing members 23. The separation membrane composite 1, the sealing unit 21, and the sealing members 23 are housed within the housing 22. In FIG. 7, the separation membrane 12 of the separation membrane composite 1 is indicated by hatching. The interior space of the housing 22 is a sealed space isolated from the space surrounding the housing 22. A mixed gas supply unit 26, a first recovery unit 27, a second recovery unit 28, and a sweep gas supply unit 29 are connected to the housing 22.

[0062] The sealing portions 21 are attached to both longitudinal end portions of the support 11 (i.e., the left-right direction in FIG. 7 ) and are members that cover and seal both longitudinal end faces 114 of the support 11 and parts of the outer surfaces 112 near the both end faces 114. The sealing portions 21 prevent gas from flowing in and out from the both end faces 114 of the support 11. The sealing portions 21 are, for example, sealing layers made of glass or resin. In this embodiment, the sealing portions 21 are glass seals with a thickness of 10 μm to 50 μm. The material and shape of the sealing portions 21 may be changed as appropriate. Note that the sealing portions 21 have multiple openings that overlap with the multiple first cells 111a of the support 11, and therefore both longitudinal end portions of each first cell 111a are not covered by the sealing portions 21. Therefore, fluid can flow in and out of the first cells 111a from the both ends.

[0063] The housing 22 is a substantially cylindrical tubular member. The housing 22 is formed of, for example, stainless steel or carbon steel. The longitudinal direction of the housing 22 is substantially parallel to the longitudinal direction of the separation membrane composite 1. A first supply port 221 is provided at one longitudinal end of the housing 22 (i.e., the left end in FIG. 7 ), and a first discharge port 222 is provided at the other end. The first supply port 221 is connected to the mixed gas supply unit 26. The first discharge port 222 is connected to the first recovery unit 27.

[0064] A second discharge port 223 and a second supply port 224 are provided on the side surface of the housing 22. In the example shown in FIG. 7, the second discharge port 223 is disposed near the longitudinal center of the housing 22, and the second supply port 224 is disposed between the second discharge port 223 and the first supply port 221 in the longitudinal direction of the housing 22. The second supply port 224 is located at approximately the same longitudinal position as the slit 117 located near one longitudinal end of the separation membrane composite 1. The second discharge port 223 and the second supply port 224 may be located at the same or different circumferential positions around the central axis of the separation membrane composite 1 (i.e., an imaginary line extending longitudinally through the center of both end faces 114 of the separation membrane composite 1). A second recovery section 28 is connected to the second discharge port 223. A sweep gas supply section 29 is connected to the second supply port 224. The shape and material of the housing 22 may be changed in various ways.

[0065] The three seal members 23 are arranged side by side in the longitudinal direction between the outer surface 112 of the separation membrane composite 1 and the inner surface of the housing 22. Each seal member 23 is a substantially annular member made of a material that is impermeable to gases and liquids. The seal members 23 are, for example, O-rings or packings made of flexible resin. The seal members 23 are in close contact with the outer surface 112 of the separation membrane composite 1 and the inner surface of the housing 22 over the entire circumferential direction (hereinafter simply referred to as the "circumferential direction") about the central axis of the separation membrane composite 1. The seal members 23 may be made of a material other than resin, such as carbon, metal, or other inorganic materials.

[0066] Of the three seal members 23, the two seal members 23 located at both ends in the longitudinal direction are arranged around the entire periphery of the separation membrane composite 1 near both longitudinal ends of the separation membrane composite 1. At each longitudinal end of the separation membrane composite 1, the seal members 23 are located longitudinally between the slit 117 and the end face 114 of the separation membrane composite 1. Of the three seal members 23, the seal member 23 located between the two seal members 23 is located longitudinally between the second supply port 224 and the second discharge port 223. In addition, this seal member 23 is located between the slit 117, which is located at approximately the same position as the second supply port 224 in the longitudinal direction, and the second discharge port 223.

[0067] 7, of the three seal members 23, two seal members 23 at both ends in the longitudinal direction are in close contact with the outer surface of the sealing portion 21 between the end face 114 of the support 11 and the slit 117 in the longitudinal direction, and are indirectly in close contact with the outer surface 112 of the separation membrane composite 1 via the sealing portion 21. The remaining seal member 23 of the three seal members 23 is in direct contact with the outer surface 112 of the separation membrane composite 1 between the slit 117 and the second discharge port 223 in the longitudinal direction. A seal is formed between each seal member 23 and the outer surface 112 of the separation membrane composite 1, and between the seal member 23 and the inner surface of the housing 22, and gas passage is substantially impossible.

[0068] The mixed gas supply unit 26 supplies the mixed gas to the internal space of the housing 22 via the first supply port 221. The mixed gas supply unit 26 includes a pressure-feeding mechanism such as a blower or a pump that pressure-feeds the mixed gas toward the housing 22. The pressure-feeding mechanism includes, for example, a temperature adjustment unit and a pressure adjustment unit that respectively adjust the temperature and pressure of the mixed gas supplied to the housing 22. The first recovery unit 27 and the second recovery unit 28 include, for example, a storage container that stores the gas discharged from the housing 22, or a blower or pump that transfers the gas. The sweep gas supply unit 29 supplies a sweep gas to the internal space of the housing 22 via the second supply port 224. The sweep gas supply unit 29 includes, for example, a pressure-feeding mechanism such as a blower or a pump that pressure-feeds the sweep gas toward the housing 22.

[0069] When separating a mixed gas, first, a separation membrane composite 1 is prepared (FIG. 8: step S21). Specifically, the separation membrane composite 1 is attached inside the housing 22. Next, a mixed gas containing multiple types of gases with different permeabilities to the separation membrane 12 is supplied by the mixed gas supply unit 26 into the interior of the housing 22 (specifically, into the space to the left of the left end face 114 of the separation membrane composite 1) as indicated by arrow 251 in FIG. 7. For example, the main components of the mixed gas are CO2 and CH4. The mixed gas may contain gases other than CO2 and CH4. The pressure of the mixed gas supplied from the mixed gas supply unit 26 to the interior of the housing 22 (i.e., the introduction pressure) is, for example, 0.1 MPa to 20.0 MPa. The temperature of the mixed gas supplied from the mixed gas supply unit 26 is, for example, 10°C to 250°C.

[0070] In the separation device 2, while the mixed gas supply unit 26 supplies the separation membrane composite 1 with the mixed gas, the sweep gas supply unit 29 supplies a sweep gas used for separating the mixed gas into the interior of the housing 22, as indicated by arrow 255. Specifically, the space to which the sweep gas is supplied is a substantially cylindrical space located radially outward from the outer surface 112 of the separation membrane composite 1 (i.e., radially from the central axis), i.e., the space between the first and second seal members 23 from the left of the three seal members 23 in FIG. 7. Various gases can be used as the sweep gas. The sweep gas may be a single-component gas or a mixture of multiple gases. The sweep gas may include, for example, at least one of H2O, air, N2, O2, and CO2. The sweep gas may also be a substance other than these.

[0071] The sweep gas supplied from the sweep gas supply unit 29 into the housing 22 flows through each slit 117 located between the first and second seal members 23 from the left in FIG. 7 and into the second cells 111b penetrated by the slits 117, as indicated by arrow 256a. In each second cell 111b, the sweep gas flows to the right in FIG. 7 as indicated by arrow 256b. The sweep gas then flows out through each slit 117 located between the first and second seal members 23 from the right in FIG. 7 and into the separation space 220 around the separation membrane composite 1, as indicated by arrow 256c. The separation space 220 is a substantially cylindrical space located radially outside the outer surface 112 of the separation membrane composite 1 (i.e., around the separation membrane composite 1) and is the space between the first and second seal members 23 from the right of the three seal members 23 in FIG. 7. In addition, some of the sweep gas flowing through the second cell 111b also flows from the second cell 111b into the pores of the surrounding support 11, passes through the support 11, and flows out from the outer surface 112 of the support 11 and other second cells 111b into the separation space 220.

[0072] Meanwhile, the mixed gas supplied into the housing 22 from the mixed gas supply unit 26 flows into each first cell 111a of the separation membrane composite 1. As indicated by arrow 252a, the highly permeable gas in the mixed gas permeates from the first cell 111a through the separation membrane 12 and the support 11 and is discharged from the outer surface 112 of the separation membrane composite 1 into the separation space 220. As indicated by arrow 252b, the highly permeable gas that permeates from the first cell 111a through the separation membrane 12 and the support 11 and flows into the second cell 111b flows to the right as indicated by arrow 256b together with the sweep gas flowing to the right in the second cell 111b and then flows out into the separation space 220 through each slit 117 located between the first and second seal members 23 from the right in FIG. 7 as indicated by arrow 256c. The highly permeable gas that has flowed from the first cell 111a into the second cell 111b may be led to the separation space 220 by passing through the support 11 without passing through the slit 117.

[0073] In the separation membrane composite 1, as described above, the sweep gas flows through the second cells 111b and the pores of the support 11 toward the separation space 220. In other words, the sweep gas flows around the first cells 111a near the first cells 111a toward the separation space 220 and flows around the outer surface 112 of the support 11. As a result, the highly permeable gas that has permeated the separation membrane 12 from the first cells 111a is carried by the sweep gas and quickly discharged into the separation space 220. This reduces the partial pressure of the highly permeable gas on the permeate side of the separation membrane 12 (i.e., the side opposite to the internal space of the first cells 111a), accelerating the movement of the highly permeable gas from the supply side of the separation membrane 12 (i.e., the internal space of the first cells 111a) to the permeate side.

[0074] In this way, the high permeable gas permeates through the separation membrane 12 and is led to the separation space 220, whereby the high permeable gas (e.g., CO2) is separated from other substances in the mixed gas, such as the low permeable gas (e.g., CH4) (step S22). As described above, in the separation device 2, the sweep gas flowing near the first cell 111a promotes permeation of the high permeable gas through the separation membrane 12, thereby promoting separation of the high permeable gas from the mixed gas.

[0075] Here, the sum of the cross-sectional areas of all first cells 111a perpendicular to the longitudinal direction is defined as A, the sum of the cross-sectional areas of all second cells 111b perpendicular to the longitudinal direction is defined as B, and the sum of the areas of the slit openings of all slits 117 at one end in the longitudinal direction (in this embodiment, the sum of the areas of the six slit openings near one end on the outer surface 112 of the support 22) is defined as C. A, B, and C have the same units. In this case, A / C is 1 or more and 50 or less, and B / C is 0.5 or more and 20 or less. By having A / C 1 or more and 50 or less, it is possible to supply the sweep gas to the separation membrane 12 arranged in the first cells 111a without excess or deficiency. Furthermore, by having B / C 0.5 or more and 20 or less, it is possible to flow the sweep gas into the second cells 111b while maintaining a small pressure loss.

[0076] As described above, the number of stages of the first cell rows 116a constituting the open cell row group sandwiched between the two second cell rows 116b positioned closest in the vertical direction is preferably 1 to 6, more preferably 1 or 2. By having the number of stages of the first cell rows 116a constituting the open cell row group be 1 to 6, the sweep gas can be efficiently supplied to the vicinity of each first cell 111a (i.e., the vicinity of the separation membrane 12).

[0077] Furthermore, since the number of stages of the first cell rows 116a constituting the open cell row group is one or two, all of the first cells 111a are adjacent to the second cells 111b or the outer surface 112 of the support 11. This allows the sweep gas to be supplied more efficiently to the vicinity of each first cell 111a (i.e., the vicinity of the separation membrane 12). As a result, permeation of the highly permeable gas through the separation membrane 12 is further promoted. Note that "the first cell 111a is adjacent to the second cell 111b" means that the first cell 111a is disposed near the second cell 111b without any other first cell 111a sandwiched between the first cell 111a and the second cell 111b. Furthermore, "the first cell 111a is adjacent to the outer surface 112 of the support 11" means that the first cell 111a is disposed near the outer surface 112 of the support 11 without any other first cell 111a sandwiched between the first cell 111a and the outer surface 112 of the support 11.

[0078] In the separation membrane composite 1, as described above, the end face 114 of the support 11 is covered with the sealing portion 21, which prevents or suppresses the mixed gas containing the low-permeable gas from entering the inside of the support 11 through the end face 114 and entering the separation space 220 without permeating the separation membrane 12. The gas discharged into the separation space 220 (hereinafter referred to as the "permeate gas") is guided to and recovered in the second recovery section 28 via the second discharge port 223, as shown by arrow 253 in FIG. 7. The second recovery section 28 is a permeate gas recovery section that recovers the permeate gas of the mixed gas that has permeated the separation membrane 12. The permeate gas may include the low-permeate gas that has permeated the separation membrane 12, in addition to the high-permeability gas described above.

[0079] Furthermore, the gas mixture excluding the gas that has permeated separation membrane 12 and support 11 (hereinafter referred to as "non-permeated gas") flows from left to right in FIG. 7 within first cell 111a and is guided to first recovery section 27 via first discharge port 222 as indicated by arrow 254 and recovered. First recovery section 27 is a non-permeated gas recovery section that recovers the non-permeated gas of the mixed gas that has not permeated separation membrane 12. The non-permeated gas recovered by first recovery section 27 may include, in addition to the low-permeability gas described above, a high-permeability gas that has not permeated separation membrane 12. The non-permeated gas recovered by first recovery section 27 may be circulated to mixed gas supply section 26 and supplied again into housing 22, for example.

[0080] In the following description, the left side in FIG. 7, which is the upstream side of the flow of the mixed gas and non-permeate gas in the first cell 111a, will be simply referred to as the "upstream side." Similarly, the right side in FIG. 7, which is the downstream side of the flow of the mixed gas and non-permeate gas in the first cell 111a, will be simply referred to as the "downstream side." In the separation device 2 illustrated in FIG. 7, the sweep gas is supplied to three slits 117, which are side flow paths, on the upstream side of the separation membrane composite 1, flows from the upstream side to the downstream side within the second cell 111b, passes through the three downstream slits 117 (i.e., the other three side flow paths), and is discharged into the separation space 220. In other words, the flow direction of the sweep gas in the second cell 111b is the same as the flow direction of the mixed gas and non-permeate gas in the first cell 111a. In this way, by supplying the sweep gas from the upstream side where the partial pressure of the highly permeable gas in the mixed gas is relatively high, the permeation of the highly permeable gas on the upstream side can be favorably promoted, and the amount of highly permeable gas that permeates the separation membrane 12 can be increased.

[0081] The number, shape, and arrangement of the slits 117 may be modified in various ways in the separation membrane composite 1. For example, the slits 117 do not necessarily need to open to the outer surface 112 of the support body 11 on both lateral sides of the second cell row 116b, but may open to the outer surface 112 of the support body 11 on only one lateral side of the second cell row 116b. In other words, the slits 117 only need to extend from the outer surface 112 of the support body 11 to the second cells 111b.

[0082] Furthermore, the slits 117 do not need to be provided in each second cell row 116b, and only some of the second cell rows 116b may be provided with slits 117. In other words, the separation membrane complex 1 may have second cell rows 116b that are not connected by slits 117.

[0083] The slits 117 do not necessarily have to be provided on both the upstream and downstream sides of the separation membrane composite 1; for example, the downstream slit 117 may be omitted. In this case, the sweep gas supplied to the upstream slit 117 flows from the upstream side to the downstream side within the second cell 111b, passes through the pores of the support 11 together with the permeate gas, and is led to the separation space 220.

[0084] As shown in FIG. 9 , the separation device 2 may further be provided with a covering portion 13 that covers the outer surface 112 of the support 11. The covering portion 13 is a substantially cylindrical film-like or thin-plate-like portion that is in direct contact with the outer surface 112 of the support 11 over the entire circumferential direction. The covering portion 13 is a layer that is denser than the support 11. The covering portion 13 is, for example, a non-porous member that is substantially free of pores. The covering portion 13 is disposed between the upstream slit 117 and the downstream slit 117. In the example shown in FIG. 9 , the covering portion 13 is disposed between the central seal member 23 of the three seal members 23 in the longitudinal direction and the downstream slit 117, and covers the entire outer surface 112 of the support 11 over substantially the entire length between the seal member 23 and the slit 117.

[0085] The covering portion 13 is formed of, for example, glass, ceramic, metal, resin, or the like. The covering portion 13 is, for example, a glass film formed on the surface of the support 11 by firing. The covering portion 13 is formed, for example, by attaching glass frit to the surface of the support 11 and firing it together with the support 11. The covering portion 13 may be formed in parallel with the formation of the separation membrane 12 (see FIG. 7), or may be formed before or after the formation of the separation membrane 12. The material and shape of the covering portion 13 may be changed as appropriate. For example, the covering portion 13 may be formed of a resin adhesive tape wound around the outer surface 112 of the support 11. Alternatively, the covering portion 13 may be a porous member having pores with an average pore diameter smaller than that of the support 11.

[0086] In this way, in the separation device 2, by providing the covering portion 13 that covers the outer surface 112 of the support 11 in the separation space 220, the sweep gas flowing through the second cells 111b (see FIG. 7) from the upstream slits 117 toward the downstream slits 117 is prevented from passing through the pores of the support 11 and flowing out from the outer surface 112 into the separation space 220 before reaching the downstream slits 117. This increases the amount of sweep gas flowing in the longitudinal direction along the first cells 111a (see FIG. 7), further promoting the movement of the high-permeability gas from the supply side to the permeation side of the separation membrane 12.

[0087] As described above, the separation device 2 includes the separation membrane composite 1 and the housing 22. The separation membrane composite 1 includes a separation membrane 12 and a porous support 11. The housing 22 accommodates the separation membrane composite 1. The support 11 is a columnar member extending in the longitudinal direction. The support 11 is provided with a plurality of cells 111 arranged in a matrix in the vertical and horizontal directions. The plurality of cells 111 includes a plurality of membrane formation cells (i.e., a plurality of first cells 111a) and discharge cells (i.e., second cells 111b). Each of the plurality of first cells 111a is open at both ends in the longitudinal direction. A separation membrane 12 is provided on the inner surface of each of the plurality of first cells 111a. The second cells 111b are closed at both ends in the longitudinal direction. At both ends of the support 11 in the longitudinal direction, side flow paths (ie, slits 117) are further provided that extend from the outer surface 112 of the support 11 to the second cells 111b.

[0088] The housing 22 is connected to a mixed gas supply unit 26, a permeate gas recovery unit (i.e., second recovery unit 28), a non-permeate gas recovery unit (i.e., first recovery unit 27), and a sweep gas supply unit 29. The mixed gas supply unit 26 supplies a mixed gas containing multiple types of gases to the separation membrane composite 1. The second recovery unit 28 recovers permeate gas from the mixed gas that has permeated through the separation membrane 12. The first recovery unit 27 recovers non-permeate gas from the mixed gas that has not permeated through the separation membrane 12. The sweep gas supply unit 29 supplies a sweep gas. The mixed gas is supplied to one end face 114 in the longitudinal direction of the separation membrane composite 1. The sweep gas is supplied to a slit 117 opening in the outer surface 112 of the support 11.

[0089] If the sum of the cross-sectional areas of all first cells 111a perpendicular to the longitudinal direction is A, the sum of the cross-sectional areas of all second cells 111b perpendicular to the longitudinal direction is B, and the sum of the opening areas of all slits 117 on the outer surface 112 of the support 11 at one end in the longitudinal direction is C, A / C is 1 or more and 50 or less, and B / C is 0.5 or more and 20 or less. As described above, this allows the sweep gas to be efficiently supplied to the vicinity of each first cell 111a (i.e., the vicinity of the separation membrane 12) around the plurality of first cells 111a. This promotes the movement of the high permeable gas from the supply side to the permeation side of the separation membrane 12, thereby improving the separation performance of the mixed gas in the separation device 2. Therefore, even when the partial pressure of the high permeable gas in the mixed gas delivered from the mixed gas supply unit 26 to the housing 22 is relatively low, the high permeable gas can be suitably separated from the mixed gas.

[0090] As described above, the support 11 preferably has another side flow path (e.g., downstream slit 117) extending from the outer surface 112 of the support 11 to the second cell 111b at a longitudinal position different from the above-described side flow path (e.g., upstream slit 117). The sweep gas supplied to the slit 117 preferably passes through the second cell 111b and the other slits 117 and is discharged to the periphery of the separation membrane composite 1. This increases the amount of sweep gas flowing through the second cell 111b between the slit 117 and the other slits 117. Increasing the amount of sweep gas flowing longitudinally along the first cell 111a in this way further promotes the movement of the high-permeability gas from the supply side to the permeation side of the separation membrane 12. As a result, the separation performance of the mixed gas in the separation device 2 can be further improved.

[0091] More preferably, the separation membrane composite 1 further includes a covering portion 13 that covers the outer surface 112 of the support 11 between the above-mentioned slits 117 and other slits 117 and is denser than the support 11. This further increases the amount of sweep gas flowing longitudinally along the first cells 111a, as described above, and further promotes the movement of the highly permeable gas from the supply side to the permeation side of the separation membrane 12. As a result, the mixed gas separation performance of the separation device 2 can be further improved.

[0092] As described above, it is preferable that all of the first cells 111a are adjacent to the outer surface 112 of the support 11 or the second cells 111b. This allows the sweep gas to be more efficiently supplied to the vicinity of each first cell 111a (i.e., the vicinity of the separation membrane 12) around the plurality of first cells 111a. This further promotes the movement of the highly permeable gas from the supply side to the permeation side of the separation membrane 12, thereby further improving the mixed gas separation performance in the separation device 2.

[0093] As described above, the sweep gas preferably contains at least one of HO, air, N, O, and CO. By using a gas that is relatively easy to treat as the sweep gas in this way, it is possible to easily treat the permeable gas and sweep gas recovered by the second recovery section 28 (for example, by disposing of the recovered gas or separating the high permeable gas from the sweep gas).

[0094] As described above, the separation membrane 12 is preferably a zeolite membrane. By forming the separation membrane 12 from zeolite crystals with uniform pore diameters, selective permeation of highly permeable gases can be suitably achieved. As a result, highly permeable gases can be efficiently separated from mixed gases.

[0095] More preferably, the maximum number of ring members of the zeolite constituting the zeolite membrane is 8 or less. This allows for more favorable selective permeation of highly permeable gases with relatively small molecular diameters, such as CO. As a result, highly permeable gases can be separated from mixed gases more efficiently.

[0096] Such a separator 2 is particularly suitable for use in a gas mixture containing one or more of the following substances: hydrogen, helium, nitrogen, oxygen, water, carbon monoxide, carbon dioxide, nitrogen oxides, ammonia, sulfur oxides, hydrogen sulfide, sulfur fluoride, mercury, arsine, hydrogen cyanide, carbonyl sulfide, C1-C8 hydrocarbons, organic acids, alcohols, mercaptans, esters, ethers, ketones, and aldehydes.

[0097] The mixed gas separation method described above includes the steps of: preparing a separation membrane composite 1 including a separation membrane 12 and a porous support 11 (step S21); and supplying a mixed gas containing multiple gases to the separation membrane 12 and separating a highly permeable gas from the mixed gas by permeating the separation membrane 12 (step S22). The support 11 has a columnar shape extending in the longitudinal direction. The support 11 is provided with a plurality of cells 111 arranged in a matrix in the vertical and horizontal directions. The plurality of cells 111 includes a plurality of membrane formation cells (i.e., a plurality of first cells 111a) and discharge cells (i.e., second cells 111b). Each of the plurality of first cells 111a is open at both ends in the longitudinal direction. A separation membrane 12 is provided on the inner surface of each of the plurality of first cells 111a. The second cells 111b are closed at both ends in the longitudinal direction. Side flow paths (i.e., slits 117) extending from the outer surface 112 of the support 11 to the second cells 111b are further provided at both longitudinal ends of the support 11. In step S22, the mixed gas is supplied to one longitudinal end face of the separation membrane composite 1, and a sweep gas is supplied to the slits 117 opening in the outer surface 112 of the support 11.

[0098] If the sum of the cross-sectional areas of all first cells 111a perpendicular to the longitudinal direction is A, the sum of the cross-sectional areas of all second cells 111b perpendicular to the longitudinal direction is B, and the sum of the opening areas of all slits 117 on the outer surface 112 of the support 11 at one end in the longitudinal direction is C, then A / C is 1 or more and 50 or less, and B / C is 0.5 or more and 20 or less. As a result, similar to the above, the sweep gas can be efficiently supplied to the vicinity of each first cell 111a (i.e., the vicinity of the separation membrane 12) around the plurality of first cells 111a. This promotes the movement of the highly permeable gas from the supply side to the permeation side of the separation membrane 12, thereby facilitating the separation of the mixed gas.

[0099] Next, a mixed gas separation apparatus 2a according to a second embodiment of the present invention will be described with reference to Fig. 10. Fig. 10 is a side view showing the mixed gas separation apparatus 2a (hereinafter also simply referred to as "separation apparatus 2a"). The separation apparatus 2a has substantially the same structure as the separation apparatus 2, except that the second supply port 224a is arranged in a position different from the second supply port 224 of the separation apparatus 2 shown in Fig. 1, and the arrangement of the three seal members 23 is different from that of the separation apparatus 2. In the following description, the same reference numerals will be used to designate components of the separation apparatus 2a that correspond to the components of the separation apparatus 2.

[0100] 10, the second supply port 224a is disposed between the first discharge port 222 and the second discharge port 223 in the longitudinal direction of the housing 22. In the example shown in FIG. 10, the second supply port 224a is located at approximately the same position in the longitudinal direction as the three slits 117 on the downstream side of the separation membrane composite 1. The second supply port 224a may be disposed at the same position in the circumferential direction as the second discharge port 223, or may be disposed at a different position. A sweep gas supply unit 29 is connected to the second supply port 224a.

[0101] Of the three seal members 23, the positions of the two seal members 23 located at both ends in the longitudinal direction are the same as in the above-described separation device 2. Of the three seal members 23, the seal member 23 located between the two seal members 23 is located between the second discharge port 223 and the second supply port 224a in the longitudinal direction. In addition, this seal member 23 is located between the second discharge port 223 and the slit 117 located at approximately the same position as the second supply port 224a in the longitudinal direction.

[0102] 11 is a cross-sectional view showing a separation device 2a. In the separation device 2a, the sweep gas supply unit 29 supplies the above-mentioned sweep gas into the housing 22 as indicated by arrow 255, in parallel with the supply of the mixed gas to the separation membrane composite 1 by the mixed gas supply unit 26. Specifically, the space to which the sweep gas is supplied is a substantially cylindrical space located radially outward from the outer surface 112 of the separation membrane composite 1, and is the space between the first and second seal members 23 from the right of the three seal members 23 in FIG. 11.

[0103] The sweep gas supplied from the sweep gas supply unit 29 into the housing 22 flows into the second cells 111b through the slits 117 on the downstream side of the separation membrane composite 1, as shown by arrow 256a. In each second cell 111b, the sweep gas flows leftward in FIG. 11 (i.e., from downstream to upstream), as shown by arrow 256b. The sweep gas then flows out through the slits 117 on the upstream side of the separation membrane composite 1, as shown by arrow 256c, into a separation space 220 around the separation membrane composite 1. The separation space 220 is a substantially cylindrical space located radially outward from the outer surface 112 of the separation membrane composite 1 (i.e., around the separation membrane composite 1), and is the space between the first and second seal members 23 from the left of the three seal members 23 in FIG. 11. The sweep gas flowing through the second cells 111b also flows from the second cells 111b into the pores of the surrounding support 11, passes through the support 11, and flows out from the outer surface 112 of the support 11 into the separation space 220.

[0104] In the separation device 2a, similar to the separation device 2 described above, the sweep gas flows around the first cells 111a and near the first cells 111a toward the separation space 220. This reduces the partial pressure of the high-permeability gas on the permeation side of the separation membrane 12 (i.e., the side opposite the internal space of the first cells 111a), thereby facilitating the movement of the high-permeability gas from the supply side of the separation membrane 12 (i.e., the internal space of the first cells 111a) to the permeation side. As a result, the separation performance of the mixed gas in the separation device 2a can be improved. Therefore, even when the partial pressure of the high-permeability gas in the mixed gas delivered from the mixed gas supply unit 26 to the housing 22 is relatively low, the high-permeability gas can be suitably separated from the mixed gas.

[0105] In the separation device 2a, the sweep gas is supplied to the three slits 117, which are the side flow paths on the downstream side of the separation membrane composite 1, and flows from downstream to upstream within the second cell 111b, passing through the three upstream slits 117 (i.e., the other three side flow paths) and being discharged into the separation space 220. In other words, the flow direction of the sweep gas within the second cell 111b is opposite to the flow direction of the mixed gas and non-permeable gas within the first cell 111a. In this way, by supplying the sweep gas from the downstream side, where the partial pressure of the highly permeable gas in the mixed gas is relatively low, the separation membrane 12 can function properly even on the downstream side, and the amount of highly permeable gas that permeates the separation membrane 12 can be increased.

[0106] The separator 2a may further be provided with the above-described covering portion 13 (see FIG. 9) that covers the outer surface 112 of the support 11, similarly to the separator 2. When the separator 2a illustrated in FIG. 10 is provided with the covering portion 13, the covering portion 13 is disposed between the central sealing member 23 in the longitudinal direction of the three sealing members 23 and the upstream slit 117, and covers the entire outer surface 112 of the support 11 over substantially the entire length between the sealing member 23 and the slit 117. This further increases the amount of sweep gas flowing in the longitudinal direction along the first cell 111a, as described above, thereby further improving the mixed gas separation performance of the separator 2a.

[0107] In the above description, the separation device 2, 2a is disposed singly between the mixed gas supply unit 26 and the first recovery unit 27, but, for example, a plurality of separation devices 2 may be connected in series between the mixed gas supply unit 26 and the first recovery unit 27. Also, a plurality of separation devices 2a may be connected in series between the mixed gas supply unit 26 and the first recovery unit 27. Alternatively, one or more separation devices 2 and one or more separation devices 2a may be connected in series between the mixed gas supply unit 26 and the first recovery unit 27. In this case, the order in which the separation devices 2 and separation devices 2a are arranged may be determined appropriately.

[0108] In the mixed gas separation system 20 illustrated in FIG. 12, one separation device 2 and one separation device 2a are connected in series between a mixed gas supply unit 26 and a first recovery unit 27. Specifically, the separation device 2a is connected in series downstream of the separation device 2. The mixed gas supply unit 26 is connected to a first supply port 221 of the separation device 2, and the first supply port 221 of the separation device 2a is connected to a first discharge port 222 of the separation device 2. The first discharge port 222 of the separation device 2a is connected to a first recovery unit 27. The second discharge port 223 of each of the separation devices 2 and 2a is connected to a second recovery unit 28, and the second supply port 224 of each of the separation devices 2 and 2a is connected to a sweep gas supply unit 29.

[0109] In the upstream separation device 2, the flow direction of the sweep gas in the second cell 111b (see FIG. 7) is substantially the same as the flow direction of the mixed gas and non-permeable gas in the first cell 111a (see FIG. 7). As described above, this effectively promotes permeation of the high-permeable gas upstream of the separation device 2, thereby increasing the amount of the high-permeable gas that permeates the separation membrane 12. In the downstream separation device 2a, the flow direction of the sweep gas in the second cell 111b (see FIG. 11) is opposite to the flow direction of the mixed gas and non-permeable gas in the first cell 111a (see FIG. 11). As described above, this effectively enables the separation membrane 12 downstream of the separation device 2a to function as well, increasing the amount of the high-permeable gas that permeates the separation membrane 12. As a result, the separation performance of the mixed gas separation system 20 can be improved.

[0110] Next, a membrane reactor 2b according to a third embodiment of the present invention will be described with reference to FIG. 13. FIG. 13 is a cross-sectional view of the membrane reactor 2b. The membrane reactor 2b includes the separation device 2 shown in FIG. 1 and a catalyst 41 supported on the separation membrane composite 1 of the separation device 2. In the following description, the separation membrane composite 1 and the catalyst 41 are collectively referred to as the "membrane reactor 4." In FIG. 13, to facilitate understanding of the drawing, the cross section of the membrane reactor 4 is simplified and conceptually shown. Furthermore, the same reference numerals are used to designate components of the membrane reactor 2b that correspond to the components of the separation device 2.

[0111] In the membrane reactor 2b, a large number of catalysts 41 are disposed in the first cells 111a of the separation membrane composite 1. The catalysts 41 may have a variety of shapes. Examples of the shape of the catalyst 41 include a sphere, an ellipsoid, a cylinder (a circular cylinder, a rectangular prism, an oblique cylinder, an oblique rectangular prism, etc.), and a pyramidal shape (a cone, a pyramid, etc.). In this embodiment, the catalyst 41 is substantially spherical. The catalyst 41 is granular, with a particle size smaller than that of the first cells 111a when viewed along the longitudinal direction of the separation membrane composite 1. The catalyst 41 is a substance that promotes the chemical reaction of the raw materials. In other words, the chemical reaction of the raw materials is promoted by being carried out in the presence of the catalyst 41. Known catalysts suitable for each reaction can be used as the catalyst 41. For example, a zirconia-supported nickel catalyst (i.e., a catalyst in which nickel (Ni) is supported on stabilized zirconia) for methanation is used. The type of catalyst 41 is not limited to this example and may be variously modified. The catalyst 41 is not disposed in the second cell 111b.

[0112] In the membrane reactor 2b, a filler that does not plug the opening of the first cell 111a may be provided at both ends or one end of the first cell 111a in the longitudinal direction to prevent or suppress particles of the catalyst 41 from falling out of the first cell 111a. The filler is made of a flexible material such as heat-resistant wool, and partially blocks the opening of the first cell 111a without substantially impeding the passage of gas.

[0113] Next, a method for operating the membrane reactor 2b will be described with reference to Fig. 14. Fig. 14 is a diagram showing the operation flow of the membrane reactor 2b. In the following description, it is assumed that methanation (i.e., a reaction for producing CH4 from CO2 and H2) is performed in the membrane reactor 2b.

[0114] In operating the membrane reactor 2b, first, the membrane reactor 4 (i.e., the separation membrane composite 1 and the catalyst 41) is prepared (step S31). Specifically, the membrane reactor 4 is attached inside the housing 22. Subsequently, the raw material gas supply unit 26b supplies a raw material gas containing raw materials (i.e., CO2 and H2) into the housing 22 (specifically, into the space to the left of the left end face 114 of the separation membrane composite 1) as shown by arrow 251. The raw material gas may contain gases other than the raw materials. In the membrane reactor 2b, the inside of the housing 22 is preheated, and the membrane reactor 4 is heated to a temperature (e.g., 150°C to 500°C) suitable for the chemical reaction of the raw materials. The temperature of the membrane reactor 4 is maintained at that temperature while the chemical reaction of the raw materials is taking place.

[0115] The sweep gas supply unit 29 supplies the above-described sweep gas into the housing 22 as indicated by arrow 255. The sweep gas flows into the second cells 111b through the upstream slits 117 as indicated by arrow 256a, and then flows to the right in FIG. 13 within the second cells 111b as indicated by arrow 256b. The sweep gas flows into the separation space 220 through the downstream slits 117 as indicated by arrow 256c. The sweep gas flowing through the second cells 111b also flows from the second cells 111b into the pores of the surrounding support 11, passes through the support 11, and flows out from the outer surface 112 of the support 11 into the separation space 220.

[0116] The raw material gas supplied from the raw material gas supply unit 26b to the housing 22 flows into each first cell 111a of the separation membrane composite 1. In each first cell 111a, the raw material undergoes a chemical reaction in the presence of the catalyst 41 to produce a mixed gas containing reactants (i.e., CH4 and HO). The highly permeable gas (i.e., HO) in the mixed gas permeates from the first cell 111a through the separation membrane 12 and the support 11, as indicated by arrow 252a, and is discharged from the outer surface 112 of the separation membrane composite 1 to the separation space 220. The highly permeable gas that permeates from the first cell 111a through the separation membrane 12 and the support 11 and flows into the second cell 111b, as indicated by arrow 252b, flows to the right within the second cell 111b together with the sweep gas flowing to the right, as indicated by arrow 256b, and then flows out into the separation space 220 through the downstream slits 117, as indicated by arrow 256c. The highly permeable gas that has flowed from the first cell 111a to the second cell 111b may be passed through the support 11 and led to the separation space 220 without passing through the slit 117. The permeable gas led to the separation space 220 is led to the second recovery section 28 and recovered, as shown by the arrow 253 in Fig. 13. In addition to the highly permeable gas described above, the permeable gas may also include the raw material gas that has permeated the separation membrane 12, a low permeable gas (i.e., CH4), and the like.

[0117] In the separation membrane composite 1, as described above, the sweep gas flows through the second cells 111b and the pores of the support 11 toward the separation space 220. In other words, the sweep gas flows around the first cells 111a and near the first cells 111a toward the separation space 220. As a result, the highly permeable gas (i.e., HO) that has permeated the separation membrane 12 from the first cells 111a is carried by the sweep gas and quickly discharged into the separation space 220. This reduces the partial pressure of the highly permeable gas on the permeate side of the separation membrane 12, accelerating the movement of the highly permeable gas from the supply side to the permeate side of the separation membrane 12. As a result, separation of the highly permeable gas from the mixed gas in the first cells 111a is accelerated, and the chemical reaction of the raw materials in the first cells 111a is accelerated (step S32).

[0118] In the membrane reactor 2b, the non-permeable gas excluding the permeable gas from the mixed gas flows through the first cell 111a from left to right in FIG. 13 and is guided to the first recovery section 27 and recovered, as indicated by the arrow 254. The non-permeable gas may include not only the low-permeable gas described above but also a highly permeable gas that did not permeate the separation membrane 12. The non-permeable gas recovered by the first recovery section 27 may be circulated to the raw material gas supply section 26b, for example, and supplied again into the housing 22.

[0119] As described above, the membrane reactor 2b includes a separation membrane composite 1, a catalyst 41, and a housing 22. The separation membrane composite 1 includes a separation membrane 12 and a porous support 11. The catalyst 41 promotes chemical reactions of the raw materials. The housing 22 accommodates the separation membrane composite 1 and the catalyst 41. The support 11 is cylindrical and extends in the longitudinal direction. The support 11 is provided with a plurality of cells 111 arranged in a matrix in the vertical and horizontal directions. The plurality of cells 111 includes a plurality of membrane formation cells (i.e., a plurality of first cells 111a) and discharge cells (i.e., second cells 111b). Each of the plurality of first cells 111a is open at both ends in the longitudinal direction. A separation membrane 12 is provided on the inner surface of each of the plurality of first cells 111a. The second cells 111b are closed at both ends in the longitudinal direction. Side flow paths (i.e., slits 117) extending from the outer surface 112 of the support 11 to the second cells 111b are further provided at both longitudinal ends of the support 11. The catalyst 41 is disposed in the plurality of first cells 111a of the separation membrane composite 1.

[0120] The housing 22 is connected to a raw material gas supply unit 26b, a permeable gas recovery unit (i.e., second recovery unit 28), a non-permeable gas recovery unit (i.e., first recovery unit 27), and a sweep gas supply unit 29. The raw material gas supply unit 26b supplies a raw material gas containing raw materials to the separation membrane composite 1. The second recovery unit 28 recovers the permeable gas that has permeated the separation membrane 12 from the mixed gas produced by the chemical reaction of the raw materials in the presence of the catalyst 41. The first recovery unit 27 recovers the non-permeable gas that has not permeated the separation membrane 12 from the mixed gas. The sweep gas supply unit 29 supplies a sweep gas. The raw material gas is supplied to one end face 114 of the separation membrane composite 1 in the longitudinal direction. The sweep gas is supplied to a slit 117 opening in the outer surface 112 of the support 11.

[0121] If the sum of the cross-sectional areas of all first cells 111a perpendicular to the longitudinal direction is A, the sum of the cross-sectional areas of all second cells 111b perpendicular to the longitudinal direction is B, and the sum of the opening areas of all slits 117 on the outer surface 112 of the support 11 at one end in the longitudinal direction is C, then A / C is 1 or more and 50 or less, and B / C is 0.5 or more and 20 or less. As a result, as described above, the sweep gas can be efficiently supplied to the vicinity of each first cell 111a (i.e., the vicinity of the separation membrane 12) around the plurality of first cells 111a. This can promote the movement of the highly permeable gas from the supply side to the permeation side of the separation membrane 12, and can accelerate the chemical reaction of the raw materials in the membrane reactor 2b.

[0122] Next, the performance of the separation membrane composite 1 of Samples 1 to 6 will be described with reference to Table 1. Samples 2 to 4 are examples of the present invention, and Samples 1, 5, and 6 are comparative examples.

[0123] [Table 1]

[0124] For Samples 1 to 6 in Table 1, a monolithic support 11 made of alumina with an outer diameter of 180 mm and a length of 1000 mm was produced by a method similar to that used in the examples of WO 2010 / 134514. By adjusting the number of stages in the first cell row 116a and the length and width of the slit openings, the support 11 having A / C and B / C shown in Samples 1 to 6 was obtained. Slits 117 of the same shape were provided near both ends of the support 11 in the longitudinal direction.

[0125] Next, by the same manufacturing method as in steps S11 to S13 described above, a DDR zeolite membrane (i.e., separation membrane 12) was synthesized inside the first cells 111a of the support 11 of samples 2 to 6, thereby obtaining a separation membrane composite 1. Note that, in order to accurately measure the pressure loss described below, step S14 (removal of SDA) was not performed in the manufacture of the support 11. In other words, the pressure loss described below was measured in a state where gas was not permeating the DDR zeolite membrane.

[0126] In the support 11 of Sample 1, A / C was 0.8 and B / C was 0.4. The support 11 of Sample 1, in which A / C was less than 1, had low strength due to the large slit openings, and could not be used to synthesize a DDR-type zeolite membrane.

[0127] Next, as shown in FIG. 9 , a resin adhesive tape (i.e., covering portion 13) was wrapped around the outer surface of the support 11 of the separation membrane composite 1 of Samples 2 to 6, and the composite was attached to the inside of the housing 22. With the second collection section 28 open to the atmosphere, a fixed amount of nitrogen gas was introduced through the sweep gas supply section 29, and the pressure difference between the sweep gas supply section 29 and the second collection section 28 was measured to measure the pressure loss. Also, with the second collection section 28 open to the atmosphere, nitrogen gas was introduced through the sweep gas supply section 29 at 500 kPa, and the amount of nitrogen gas recovered in the second collection section 28 (i.e., the amount of recovered gas) was measured. For Samples 2 to 6, the amount of recovered gas divided by the membrane area of ​​the DDR zeolite membrane was used to determine the sweep gas sufficiency (%). The sweep gas sufficiency of Sample 2 was set to 100%, and the sweep gas sufficiency of the other samples was calculated.

[0128] For the support 11 of Sample 2, A / C was 1.1 and B / C was 0.5. The pressure loss was 0.2 kPa, and the sweep gas filling rate was 100% as described above. For the support 11 of Sample 3, A / C was 7.9 and B / C was 1.6. The pressure loss was 2.3 kPa, and the sweep gas filling rate was 80%. For the support 11 of Sample 4, A / C was 48.2 and B / C was 9.6. The pressure loss was 98.8 kPa, and the sweep gas filling rate was 64%.

[0129] For the support 11 of sample 5, A / C was 48.5 and B / C was 24.3. The pressure loss was 157.4 kPa and the sweep gas sufficiency was 69%. For the support 11 of sample 6, A / C was 67.0 and B / C was 33.5. The pressure loss was 302.0 kPa and the sweep gas sufficiency was 40%.

[0130] Comparing Samples 2 to 4 with Samples 5 and 6, Samples 2 to 4, in which the B / C ratio was 0.5 or more and 20 or less, had a low pressure drop of 100 kPa or less. Furthermore, Samples 2 to 5, in which the A / C ratio was 1 or more and 50 or less, had a sweep gas sufficiency of 60% or more. Thus, Samples 2 to 4, in which the A / C ratio was 1 or more and 50 or less and the B / C ratio was 0.5 or more and 20 or less, were able to flow a sufficient amount of sweep gas relative to the membrane area while maintaining a low pressure drop. Therefore, when a separation membrane composite 1 having a separation membrane 12 (e.g., a DDR-type zeolite membrane produced by a manufacturing method similar to the above-mentioned steps S11 to S14) provided on the support 11 of Samples 2 to 4 is used to separate a mixed gas by flowing a sweep gas in the separator 2, the permeation of the target gas can be more efficiently promoted.

[0131] 1, the resin adhesive tape (i.e., covering portion 13) that had been wrapped around separation membrane composite 1 was removed, and pressure loss measurements were performed on Samples 2 to 6 in the same manner as above. The pressure loss values ​​showed the same tendency as in Table 1, but it was found that some of the nitrogen gas passed through the pores of support 11 without passing through second cell 111b and flowed out to second recovery section 28. In this way, by providing covering portion 13 on the outer surface of support 11, the amount of sweep gas flowing longitudinally along first cell 111a can be increased.

[0132] Furthermore, when pressure loss was measured in the same manner as above for separation membrane composites 1 of samples 2 to 6, with resin adhesive tape wrapped only around the locations of slits 117 at the ends farthest from sweep gas supply unit 29, it was confirmed that the pressure loss values ​​were greater than those shown in Table 1. Thus, by providing slits 117 near both longitudinal ends of support 11, sweep gas can be made to flow into second cell 111b while maintaining low pressure loss.

[0133] As described above, the separation performance of mixed gases can be improved in a separation membrane composite 1 in which A / C is 1 or more and 50 or less and B / C is 0.5 or more and 20 or less. In addition, by providing slits 117 at both ends of the support 11 or by covering the outer surface of the support 11 with a dense covering portion 13, the separation performance of mixed gases can be further improved.

[0134] The separation devices 2, 2a, the mixed gas separation method, and the membrane reactor 2b described above can be modified in various ways.

[0135] For example, as in a separation apparatus 2c shown in Fig. 15, the longitudinal length of the covering portion 13 may be changed from that of the covering portion 13 of the separation apparatus 2 shown in Fig. 9. In the example shown in Fig. 15, the upstream edge of the covering portion 13 is located near the upstream slit 117. In this case, the seal member 23, which is located downstream of the second supply port 224 to which the sweep gas supply unit 29 is connected and close to the upstream slit 117, indirectly contacts the outer surface 112 of the support body 11 via the covering portion 13.

[0136] 15, the second discharge port 223 to which the second recovery section 28 is connected may be located at approximately the same longitudinal position as the downstream slit 117. Furthermore, in the separation device 2c, a seal member 23 may be newly provided upstream of the second discharge port 223 and adjacent to the downstream slit 117. In this case, the seal member 23 indirectly contacts the outer surface 112 of the support 11 via the covering portion 13. In the separation device 2c, almost all of the permeation gas that has permeated the separation membrane 12 (see FIG. 7) flows into the second cell 111b (see FIG. 7), passes through the downstream slit 117 together with the sweep gas, and is recovered by the second recovery section 28. In the separation device 2c, in the region sandwiched between two of the four seal members 23 excluding both longitudinal ends, the outer surface 112 of the support 11 is covered with the covering portion 13 over substantially the entire surface. Therefore, in this region, the permeate gas and the sweep gas are substantially not led out from the outer surface 112 of the support 11 to the periphery of the separation membrane composite 1. In the separation device 2c, the positions of the second recovery section 28 and the sweep gas supply section 29 may be reversed.

[0137] In the separation membrane composite 1 of the separation device 2 shown in FIG. 7, the maximum number of rings of the zeolite constituting the separation membrane 12, which is a zeolite membrane, may be greater than 8. Furthermore, the separation membrane 12 is not limited to a zeolite membrane and may be an inorganic membrane such as a silica membrane or a carbon membrane, or an organic membrane such as a polyimide membrane or a silicone membrane. In addition to the separation membrane 12, the separation membrane composite 1 may further include a functional membrane or a protective membrane laminated on the separation membrane 12. Such a functional membrane or protective membrane may be a zeolite membrane, an inorganic membrane other than a zeolite membrane, or an organic membrane. The same applies to the separation devices 2a, 2c and the membrane reactor 2b.

[0138] Of the three sealing members 23 of the separation device 2 shown in Figure 7, in one sealing member 23 other than those at both ends in the longitudinal direction, a small amount of gas may pass between the sealing member 23 and the outer surface 112 of the separation membrane composite 1, and between the sealing member 23 and the inner surface of the housing 22.

[0139] In the membrane reactor 2b, a chemical reaction other than methanation may be carried out, such as a reverse shift reaction, a methanol synthesis reaction, or a Fischer-Tropsch synthesis reaction.

[0140] The configurations in the above-described embodiment and each modification may be combined as appropriate as long as they are not mutually contradictory.

[0141] While the invention has been particularly illustrated and described, it should be understood that the foregoing description is illustrative and not restrictive, and that numerous modifications and variations are possible without departing from the scope of the invention. [Industrial Applicability]

[0142] The separation device of the present invention can be used, for example, in the separation of various mixed gases. Also, the membrane reactor of the present invention can be used in producing various reactants from various raw materials through chemical reactions in the presence of a catalyst. [Explanation of symbols]

[0143] 1 Separation membrane complex 2,2a,2c Separation device 2b Membrane reactor 11 Support 12 Separation membrane 13 Covering part 22 Housing 26 Mixed gas supply unit 26b Raw material gas supply unit 27 First Recovery Section 28 Second Recovery Section 29 Sweep gas supply section 41 Catalyst 111 cells 111a Cell 1 111b Second Cell 112 External surface 114 End face 117 Slit S11~S14, S21~S22, S31~S32 steps

Claims

1. A method for separating a mixed gas, comprising: a) providing a separation membrane composite comprising a separation membrane and a porous support; b) supplying a mixed gas containing a plurality of gases to the separation membrane and separating a highly permeable gas in the mixed gas from the mixed gas by allowing the highly permeable gas to permeate through the separation membrane; Equipped with the support is a columnar member extending in the longitudinal direction, The support is provided with a plurality of cells arranged in a matrix in the vertical and horizontal directions, The plurality of cells include: a plurality of film-forming cells each having openings at both ends in the longitudinal direction and each having the separation membrane provided on an inner surface thereof; a discharge cell that is closed at both longitudinal ends; Including, At both longitudinal ends of the support, side flow paths are further provided from the outer surface of the support to the discharge cells, a mixed gas separation method in which, in step b), the mixed gas is supplied to one longitudinal end face of the separation membrane composite, and a sweep gas is supplied to the side flow path that opens into the outer surface of the support at the one longitudinal end, flows through the discharge cells, and is discharged from the side flow path that opens into the outer surface of the support at the other longitudinal end with a pressure drop of 100 kPa or less.

2. 2. The mixed gas separation method according to claim 1, a catalyst for promoting a chemical reaction of a source material is disposed in each of the plurality of film-forming cells; The mixed gas separation method, wherein the mixed gas is a gas produced by a chemical reaction of the raw material in the presence of the catalyst.

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