Separation device and separation device design method

Abstract

Provided are a separation device and a method for designing the separation device, in which the separation device has a good selection ratio with respect to the selection ratio of a separation membrane. The separation device selectively separates carbon dioxide gas from a supply gas, and is provided with: a separation membrane through which carbon dioxide gas included in the supply gas selectively passes; a housing part in which a housing space for housing the permeate gas that permeates the separation membrane is formed; a pipe connected to the housing part; and a pump that reduces the pressure of the accommodation space through the piping and sucks the permeated gas, and (P1 / P2) / (A / B) > = 1, where A is the carbon dioxide gas transmission rate of the separation membrane, B is the nitrogen gas transmission rate of the separation membrane, P1 is the total pressure of the supplied gas, and P2 is the total pressure of the permeated gas in the accommodation space. When the gas transmission rate of the flow path between the separation membrane for transmitting the gas and the pump is set as C, 1 > (B + C) / (A + C) > = 0.8.

Description

TECHNICAL FIELD

[0001] The present application relates to a separation device and a design method of a separation device. BACKGROUND

[0002] In order to achieve carbon neutrality, a technology of taking in and recovering carbon dioxide gas in the atmosphere is being studied. As one of such technologies, a membrane separation method of separating a target gas such as carbon dioxide gas from a mixed gas such as the atmosphere using a separation membrane is known.

[0003] For example, in Patent Literature 1, a separation membrane is disclosed which includes: a porous support; a thin film of a siloxane compound disposed on the porous support, and a surface layer of which is subjected to plasma treatment by a non-polymerizable gas; and a plasma polymerized film disposed on the thin film. The porous support supports the thin film and the polymerized film. A mixed gas is supplied to the thin film and the polymerized film. In the thin film and the polymerized film, the permeation rate of a target gas in the mixed gas is higher than the permeation rate of a non-target gas in the mixed gas. Therefore, the separation membrane can selectively separate the target gas from the mixed gas.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. Sho 60-75320

[0007] The separation membrane is used, for example, assembled into a separation device. The separation device has, for example, a housing portion that houses a gas that has permeated the separation membrane, and a pump that depressurizes the inside of the housing portion and draws the gas that has permeated the separation membrane. The ratio of the permeation rate of a target gas of the separation membrane to the permeation rate of a non-target gas is referred to as a "selectivity ratio". Even if a separation membrane having a good selectivity ratio is assembled into a separation device, the selectivity ratio of the separation device with respect to the separation membrane can be significantly reduced depending on the structure of the portion other than the separation membrane in the separation device. SUMMARY

[0008] The separation device according to an application example of the present application is a separation device that selectively separates carbon dioxide gas from a supply gas including the carbon dioxide gas and nitrogen gas, and includes:

[0009] a separation membrane that includes a porous body and a resin layer disposed on the porous body and that selectively permeates the carbon dioxide gas included in the supply gas to the porous body;

[0010] a housing portion that holds the separation membrane and that is formed with a housing space that houses a permeated gas that has permeated the separation membrane;

[0011] a pipe connected to the housing portion, and

[0012] a pump that depressurizes the housing space via the pipe and draws the permeated gas,

[0013] when the carbon dioxide gas permeability of the separation membrane is set to A,

[0014] 500,000 GPU ≥ A ≥ 1,000 GPU,

[0015] when the nitrogen gas permeability of the separation membrane is set to B, the total pressure of the supply gas is set to P1, and the total pressure of the permeated gas in the housing space is set to P2,

[0016] (P1 / P2) / (A / B) ≥ 1,

[0017] the flow path between the separation membrane of the permeated gas and the pump includes the housing space and the internal space of the pipe,

[0018] when the gas permeability of the flow path is set to C,

[0019] 1 > (B + C) / (A + C) ≥ 0.8.

[0020] The design method of the separation device according to the application example is a design method of a separation device that selectively separates carbon dioxide gas from a supply gas including the carbon dioxide gas and nitrogen gas, and includes:

[0021] a step of selecting a separation membrane including a porous body and a resin layer disposed on the porous body and capable of permeating the carbon dioxide gas included in the supply gas to the porous body, and

[0022] a step of designing a housing portion that holds the separation membrane and forms a housing space that houses a permeated gas permeated through the separation membrane, a pipe connected to the housing portion, and a pump that depressurizes the housing space via the pipe and draws the permeated gas,

[0023] the flow path between the separation membrane of the permeated gas and the pump includes the housing space and the internal space of the pipe,

[0024] in the selecting step,

[0025] when the carbon dioxide gas permeability of the separation membrane is set to A, the separation membrane is selected to be 500,000 GPU ≥ A ≥ 1,000 GPU,

[0026] in the designing step,

[0027] When a nitrogen permeation rate of the separation membrane is set as B, a total pressure of the supply gas is set as P1, and a total pressure of the permeated gas in the housing space is set as P2, the pump capable of reducing the pressure of the housing space is selected so that (P1 / P2) / (A / B) ≥ 1,

[0028] When a gas permeation rate of the flow path is set as C, the flow path is designed so that 1 > (B+C) / (A+C) ≥ 0.8. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a perspective view showing a separation device according to the first embodiment.

[0030] Figure 2 is a cross-sectional view showing a separation device according to the first embodiment.

[0031] Figure 3 is a cross-sectional view showing a part of Figure 2 .

[0032] Figure 4 is a schematic view showing a method of measuring a gas permeation rate of a flow path in the first embodiment.

[0033] Figure 5 is a flowchart showing a design method of a separation device according to the first embodiment.

[0034] Figure 6 is a cross-sectional view showing a separation device according to the second embodiment.

[0035] Figure 7 is a schematic view showing a method of measuring a gas permeation rate of a flow path in the second embodiment.

[0036] Figure 8 is a cross-sectional view showing a separation membrane according to Modification 1.

[0037] Figure 9 is a cross-sectional view showing a separation membrane according to Modification 2.

[0038] Figure 10 is a cross-sectional view showing a separation membrane according to Modification 3.

[0039] Figure 11 is a cross-sectional view showing a separation device according to Comparative Example 1.

[0040] Figure 12 is Table 1 showing structures and evaluation results of the separation devices according to Examples 1 to 3 and the separation devices according to Comparative Examples 1 to 3.

[0041] BRIEF DESCRIPTION OF DRAWINGS

[0042] 10, measuring device; 11, gas supply portion; 12, upstream side pressure gauge; 13, downstream side pressure gauge; 14, flow meter; 15, vacuum pump; 16, concentration meter; 100, separation device; 110, separation membrane; 110a, first surface; 110b, second surface; 111, porous body; 112, resin layer; 113, porous layer; 113h, void; 120, porous plate; 121, through hole; 130, housing portion; 130a, intake port; 130b, discharge port; 130c, step; 130s, housing space; 131, first wall portion; 132, second wall portion; 133, side wall portion; 140, fixing member; 141, fixing tool; 150, pipe; 151, internal space; 160, pump; 200, separation device; 210, other separation membrane; 211, other porous body; 212, other resin layer; 220, other porous plate; 230, other housing portion; 230s, other housing space; 240, other fixing member; 250, other pipe; 270, third pipe; 280, fourth pipe; 310, separation membrane; 311, porous body; 313, porous layer; 313h, void; 314, porous layer; 314h, void; 410, separation membrane; 411, porous body; 413, porous layer; 413h, void; 510, separation membrane; 511, porous body; 513, porous layer; 513h, void; 900, separation device; 930, housing portion; 950, pipe; 952, bent portion; 953, bent portion; C1, central axis; D1, diameter; D2, diameter; FP, flow path; FP1, flow path; FP2, other flow path; FP11, flow inlet portion; G1, supply gas; G2, permeated gas; G3, other permeated gas; P, plane; PS1, pressure gauge; PS2, pressure gauge; S1, selected step; S2, designed step. DETAILED DESCRIPTION

[0043] Hereinafter, a plurality of embodiments of the present application and a plurality of modified examples will be described with reference to the drawings. Note that the following description does not constitute a limitation on the technical scope and the meaning of the terms recited in the claims. Furthermore, the dimensions of the drawings are exaggerated for the purpose of explanation and there are cases in which the actual proportions differ from those depicted in the drawings.

[0044] First Embodiment

[0045] First, the separation device 100 according to the first embodiment will be described.

[0046] Figure 1 is a perspective view showing the separation device 100 according to the present embodiment.

[0047] Figure 2is a cross-sectional view showing the separation device 100 according to the present embodiment.

[0048] Figure 3 is a cross-sectional view showing a part of Figure 2 enlarged.

[0049] In addition, in Figure 1 , the pump 160 described later is schematically shown as a cylindrical shape. Similarly, in Figure 2 , the pump 160 is schematically shown as a circular shape. Further, in Figure 2 , the housing portion 130 and the pipe 150 described later are not shown as cross sections but as end surfaces.

[0050] In each drawing of the present embodiment, three axes orthogonal to each other are set as an X-axis, a Y-axis, and a Z-axis. Each axis is indicated by an arrow, with the leading end side of the arrow as "positive" and the base end side of the arrow as "negative". In the following description, for example, the "X-axis direction" includes both the positive direction and the negative direction of the X-axis. The same applies to the Y-axis direction and the Z-axis direction. Further, in the following description, in particular, the Z-axis positive side is "up" and the Z-axis negative side is "down". The Z-axis does not need to be parallel to the vertical axis and can intersect the vertical axis. Further, hereinafter, the uppermost end of each component is referred to as the "upper end", and a certain range from the upper end downward in the component is referred to as the "upper end portion". Similarly, the lowermost end of each component is referred to as the "lower end", and a certain range from the lower end upward in the component is referred to as the "lower end portion".

[0051] A brief description will be made with reference to Figure 1 and Figure 2 , the separation device 100 is provided with a separation membrane 110, a housing portion 130, a pipe 150, and a pump 160.

[0052] The surface of the separation membrane 110 includes a first surface 110a and a second surface 110b that form opposite faces. A mixed gas is supplied to the first surface 110a of the separation membrane 110. Hereinafter, the mixed gas supplied to the separation membrane 110 is also referred to as "supply gas G1". The supply gas G1 includes carbon dioxide gas and nitrogen gas. The supply gas G1 is not particularly limited and is, for example, air or the like. In the separation membrane 110, the carbon dioxide gas permeability is higher than the nitrogen gas permeability. Therefore, the separation membrane 110 can selectively permeate the carbon dioxide gas included in the supply gas G1. Thus, the separation membrane 110 can selectively separate the carbon dioxide gas from the supply gas G1. Here, the so-called "selectively permeate or separate the carbon dioxide gas" does not mean that only the carbon dioxide gas is permeated or separated and the nitrogen gas is not permeated or separated at all. The so-called "selectively permeate or separate the carbon dioxide gas" means that the carbon dioxide gas is permeated or separated at a higher permeability than the nitrogen gas, that is, the carbon dioxide gas is preferentially permeated or separated than the nitrogen gas.

[0053] The housing portion 130 holds the separation membrane 110. The housing portion 130 is formed with a housing space 130s that houses a gas that has permeated the separation membrane 110. The second surface 110b of the separation membrane 110 faces the housing space 130s. Hereinafter, the gas that has permeated the separation membrane 110 is also referred to as "permeated gas G2". The separation membrane 110 allows carbon dioxide gas to permeate preferentially, while also allowing nitrogen gas to permeate. Therefore, the permeated gas G2 includes carbon dioxide gas as well as nitrogen gas.

[0054] The pipe 150 is connected to the housing portion 130. The pump 160 depressurizes the housing space 130s via the pipe 150. Thereby, the pressure applied to the first surface 110a of the separation membrane 110 becomes higher than the pressure applied to the second surface 110b. As a result, permeation of carbon dioxide gas is promoted in the separation membrane 110. The permeated gas G2 in the housing space 130s is drawn by the pump 160 and recovered.

[0055] In the present embodiment, the separation device 100 further includes a porous plate 120 that supports the separation membrane 110, and a fixing member 140 that fixes the separation membrane 110 and the porous plate 120 to the housing portion 130. Hereinafter, each portion of the separation device 100 will be described in detail.

[0056] First, the separation membrane 110 will be described.

[0057] As shown in FIG. 1, the separation membrane 110 includes a porous body 111 and a resin layer 112 disposed on the porous body 111. Figure 3

[0058] In the present embodiment, the porous body 111 is composed of a porous layer 113 that is formed with a plurality of pores 113h. The porous layer 113 extends in the X-axis direction and the Y-axis direction. In the present embodiment, the shape of the porous layer 113 in plan view is circular. However, the shape of the porous layer in plan view is not limited to the above shape, and can be, for example, a polygon such as a quadrangle. The lower surface of the porous layer 113 corresponds to the second surface 110b of the separation membrane 110.

[0059] Each pore 113h penetrates the porous layer 113 in the thickness direction. In the present embodiment, the thickness direction of the porous layer 113 coincides with the Z-axis direction. The plurality of pores 113h are formed so as to be dispersed in the X-Y plane. Here, the diameter of the inscribed circle of the pore 113h is taken as the "diameter" of the pore 113h. In the present embodiment, the diameter of each pore 113h is substantially constant without changing in the thickness direction.

[0060] ​The average value of the diameters of the upper ends of the plurality of pores 113h is taken as the "average diameter" of the pores 113h. The average diameter of the pores 113h is preferably 0.01 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 500 μm or less, and further preferably 0.5 μm or more and 300 μm or less. In addition, after the resin layer 112 is removed from the separation membrane 110 and the individual porous layer 113 is taken out, the average diameter of the pores 113h can be measured by a through-hole diameter evaluation device. As the through-hole diameter evaluation device, for example, a Perm Porometer manufactured by PMI Co. can be cited. By setting the average diameter of the pores 113h to be the above lower limit value or more, the carbon dioxide gas permeability of the porous layer 113 can be made good. Further, by setting the average diameter of the pores 113h to be the above upper limit value or less, the mechanical strength of the separation membrane 110 can be made good.

[0061] The average value of the thicknesses of a plurality of positions on the X-Y plane of the porous layer 113 is taken as the "average thickness" of the porous layer 113. The average thickness of the porous layer 113 is not particularly limited, and is preferably 1 μm or more and 3000 μm or less, more preferably 5 μm or more and 500 μm or less, and further preferably 10 μm or more and 150 μm or less. The average thickness of the porous layer 113 can be measured by a scanning electron microscope (SEM) or the like, for example. By setting the average thickness of the porous layer 113 to be the above lower limit value or more, the mechanical strength of the separation membrane 110 can be made good. By setting the average thickness of the porous layer 113 to be the above upper limit value or less, the carbon dioxide gas permeability of the separation membrane 110 can be made good.

[0062] The material of the porous body 111 is, for example, a high molecular material, a ceramic material, or a metal material, or the like. As the high molecular material, for example, a polyolefin-based resin such as polyethylene or polypropylene; a fluorine-containing resin such as polytetrafluoroethylene, polyvinyl fluoride, or polyvinylidene fluoride; polystyrene, cellulose, cellulose acetate, polyurethane, polyacrylonitrile, polyphenylene ether, polysulfone, polyethersulfone, polyimide, polyaramide, nylon, or the like can be cited. As the ceramic material, for example, alumina, cordierite, mullite, silicon carbide, zirconia, or the like can be cited. As the metal material, for example, stainless steel or the like can be cited.

[0063] However, the structure of the porous body is not limited to the above structure. For example, as described later, the diameters of the pores formed in the porous body can vary in the thickness direction. In addition, the porous body can be composed of a plurality of porous layers stacked.

[0064] The resin layer 112 is a substantially dense film having a good affinity with molecules of carbon dioxide. Therefore, in the resin layer 112, the carbon dioxide gas permeation rate is higher than the nitrogen gas permeation rate. Thus, the resin layer 112 selectively permeates the carbon dioxide gas in the supply gas G1. In the present embodiment, the resin layer 112 covers substantially the entire region of the upper surface of the porous body 111. Therefore, in the present embodiment, the shape of the resin layer 112 in plan view is circular like the porous body 111. However, the shape of the resin layer in plan view is not limited to the above shape, and can be, for example, a polygon such as a quadrangle. The upper surface of the resin layer 112 corresponds to the first surface 110a of the separation membrane 110.

[0065] The average value of the thicknesses of a plurality of positions on the X-Y plane of the resin layer 112 is taken as the "average thickness" of the resin layer 112. In the present embodiment, the average thickness of the resin layer 112 is smaller than the average thickness of the porous body 111. The average thickness of the resin layer 112 is not particularly limited, and is preferably 10 nm or more and 1000 nm or less, more preferably 10 nm or more and 800 nm or less, and further preferably 30 nm or more and 500 nm or less. The average thickness of the resin layer 112 can be measured by, for example, SEM or the like. By setting the average thickness of the resin layer 112 to be equal to or greater than the lower limit value described above, it is possible to suppress the occurrence of defects or breakage in the resin layer 112. By setting the average thickness of the resin layer 112 to be equal to or less than the upper limit value described above, it is possible to make the carbon dioxide gas permeation rate of the separation membrane 110 good.

[0066] The material of the resin layer 112 is a high molecular material. As the high molecular material, for example, polyolefin-based resins such as polyethylene, polypropylene, and the like; fluorine-containing resins such as polytetrafluoroethylene, polyfluoroethylene, polyvinylidene fluoride, and the like; polystyrene, cellulose, cellulose acetate, polyurethane, polyacrylonitrile, polyphenylene ether, polysulfone, polyethersulfone, polyimide, polyaramid, organopolysiloxane, polyethylene terephthalate (PET), polyoxymethylene (POM), polylactic acid (PLA), and the like can be given. The constituent material of the resin layer 112 can be one of these high molecular materials or a composite material of two or more of these high molecular materials. Furthermore, the high molecular material can be a thermoplastic resin, a thermosetting resin, or a photocurable resin.

[0067] Among them, the constituent material of the resin layer 112 preferably uses organopolysiloxane. The organopolysiloxane has a good affinity with molecules of carbon dioxide.

[0068] Next, the porous plate 120 will be described.

[0069] In the present embodiment, the porous plate 120 is a flat plate shape substantially parallel to the X-Y plane. The shape in plan view of the porous plate 120 is, for example, a circular shape. The separation membrane 110 is disposed on the porous plate 120. A plurality of through holes 121 are formed in the porous plate 120. Each through hole 121 penetrates the porous plate 120 in the thickness direction. In the present embodiment, the thickness direction of the porous plate 120 coincides with the Z-axis direction. The plurality of through holes 121 are formed in a dispersed manner in the X-Y plane.

[0070] The rigidity of the porous plate 120 is higher than that of the separation membrane 110. Therefore, the porous plate 120 can well support the separation membrane 110. As a result, when there is a difference between the pressure applied to the first surface 110a and the pressure applied to the second surface 110b of the separation membrane 110, the deformation and breakage of the separation membrane 110 can be suppressed.

[0071] The shape in plan view of each through hole 121 is, for example, a circular shape or a polygonal shape such as a hexagonal shape. The diameter of the inscribed circle of each through hole 121 is referred to as the "diameter" of each through hole 121. The diameter of each through hole 121 is substantially constant in the thickness direction of the porous plate 120. In addition, the average value of the diameters of the plurality of through holes 121 is referred to as the "average diameter" of the through holes 121. In the present embodiment, the average diameter of the through holes 121 of the porous plate 120 is larger than the average diameter of the voids 113h of the porous body 111. Thus, the gas permeability of the porous plate 120 can be made good.

[0072] The average diameter of the through holes 121 is not particularly limited, and is preferably 0.1 mm or more and 10 mm or less, more preferably 0.5 mm or more and 5 mm or less, and further preferably 0.7 mm or more and 3 mm or less. By setting the average diameter of the through holes 121 to be equal to or greater than the lower limit value described above, the gas permeability of the porous plate 120 can be made good. By setting the average diameter of the through holes 121 to be equal to or less than the upper limit value described above, the rigidity of the porous plate 120 can be made good. In addition, by setting the average diameter of the through holes 121 to be equal to or less than the upper limit value described above, when there is a difference between the pressure applied to the first surface 110a and the pressure applied to the second surface 110b of the separation membrane 110, the separation membrane 110 can be suppressed from being flexed in a manner to fall into the through holes 121.

[0073] The average thickness of the porous plate 120 at multiple locations on the XY plane is used as the "average thickness" of the porous plate 120. In this embodiment, the average thickness of the porous plate 120 is greater than the average thickness of the separation membrane 110. The average thickness of the porous plate 120 is not particularly limited, but is preferably 0.01 mm or more and 50 mm or less, more preferably 0.05 mm or more and 30 mm or less, and even more preferably 0.1 mm or more and 5 mm or less. By setting the average thickness of the porous plate 120 to the lower limit value mentioned above, deformation of the porous plate 120 can be suppressed when the pump 160 depressurizes the receiving space 130s. Furthermore, by setting the average thickness of the porous plate 120 to the upper limit value mentioned above, the pressure loss when the permeable gas G2 flows in each through hole 121 of the porous plate 120 can be reduced.

[0074] The porous plate 120 can be made of ceramic or metallic materials. Examples of ceramic materials include alumina. Examples of metallic materials include stainless steel, titanium, and aluminum. However, the structure of the porous plate is not limited to the above-mentioned structures. Furthermore, a porous plate may not be used in the separation device.

[0075] Next, the Containment Department 130 will be explained.

[0076] like Figure 1 as well as Figure 2 As shown, the receiving portion 130 is a chamber. In this embodiment, the receiving portion 130 is a hollow cylinder. The central axis C1 of the receiving portion 130 extends in the Z-axis direction. An inlet 130a through which gas G2 flows in and an outlet 130b through which gas G2 flows out are formed in the receiving portion 130.

[0077] Specifically, the receiving section 130 includes: a first wall portion 131 having an inlet 130a; a second wall portion 132 located below the first wall portion 131 and having an outlet 130b; and a side wall portion 133 located between the first wall portion 131 and the second wall portion 132. The first wall portion 131 and the second wall portion 132 are flat plates that are substantially parallel to the XY plane. The first wall portion 131 and the second wall portion 132 are circular in plan view. The side wall portion 133 is cylindrical and extends along the Z-axis. The upper end of the side wall portion 133 is connected to the outer periphery of the first wall portion 131 around its entire circumference. The lower end of the side wall portion 133 is connected to the outer periphery of the second wall portion 132 around its entire circumference.

[0078] The receiving space 130s is the internal space of the receiving portion 130 formed by the first wall portion 131, the second wall portion 132, and the side wall portion 133. In this embodiment, the receiving space 130s is cylindrical in shape.

[0079] The inlet 130a extends approximately through the center of the first wall portion 131 in the thickness direction when viewed from above. The shape of the inlet 130a in plan view is, for example, circular. A step 130c is formed around the inlet 130a on the upper surface of the first wall portion 131, allowing a perforated plate 120 to be disposed. The perforated plate 120 is disposed on the step 130c in a manner that covers the inlet 130a.

[0080] The outlet 130b extends approximately to the center of the second wall portion 132 in the thickness direction when viewed from above. The shape of the outlet 130b in plan view is, for example, roughly similar to the shape of the pipe 150 described later, and is circular.

[0081] However, the specific shape of the receiving section is not limited to the shapes described above. For example, the shape of the receiving section may also be a hollow cuboid. Furthermore, for example, a step for arranging the perforated plate may not be formed in the first wall. Furthermore, the shapes of the inlet, the receiving space, and the outlet are not limited to the shapes described above. For example, the top view of the inlet and outlet may be a quadrilateral or other polygon. Furthermore, for example, the shape of the receiving space may be a cuboid. Furthermore, as long as permeable gas can flow into the receiving space and the permeable gas flowing into the receiving space can be discharged to the piping, the positions of the inlet and outlet are not limited to the positions described above.

[0082] Next, the fixing component 140 will be described.

[0083] like Figure 1 as well as Figure 2 As shown, in this embodiment, the fixing member 140 is frame-shaped. With the separation membrane 110 and the outer periphery of the perforated plate 120 covered from above, the fixing member 140 is fixed to the receiving portion 130 by multiple fixing tools 141 such as screws or bolts. Thus, the receiving portion 130 holds the separation membrane 110 and the perforated plate 120. Although not shown in the figure, it is preferable to provide a sealing member to prevent gas leakage from gaps between the separation membrane 110 and the fixing member 140 or between the fixing member 140 and the receiving portion 130. However, the specific shape of the fixing member is not limited to the above shape as long as the separation membrane can be fixed to the receiving portion. Furthermore, the method of fixing the separation membrane and the perforated plate to the receiving portion is not limited to using the fixing member.

[0084] Next, the piping 150 will be described.

[0085] The pipe 150 is cylindrical, and in the present embodiment, extends linearly in the Z-axis direction. Accordingly, the internal space 151 of the pipe 150 also extends linearly in the Z-axis direction. The upper end portion of the pipe 150 is inserted into the discharge port 130b, and the upper end of the pipe 150 is substantially coplanar with the upper surface of the second wall portion 132 of the housing portion 130. The internal space 151 of the pipe 150 communicates with the housing space 130s. The diameter D1 of the upper end portion of the internal space 151 gradually decreases from the upstream to the downstream.

[0086] However, the specific shape of the pipe is not limited to the above-described shape. For example, the pipe can also be curved. In addition, the diameter of the upper end portion of the pipe can also be constant without changing from the upstream to the downstream. Furthermore, instead of inserting the upper end portion of the pipe into the discharge port, the pipe can be connected to the discharge port of the second wall portion with the upper end of the pipe in contact with the lower surface of the second wall portion of the housing portion.

[0087] The arithmetic average roughness of the formation surface of the through holes 121 of the porous plate 120, the housing portion 130, and the inner surface of the pipe 150 is referred to as the surface roughness. The surface roughness is not particularly limited, and is preferably 0.012 μm or more and 6.3 μm or less, more preferably 0.05 μm or more and 6.3 μm or less, and further preferably 0.1 μm or more and 1.6 μm or less. By setting the surface roughness to be equal to or less than the above-described upper limit value, the pressure loss when the permeated gas G2 flows in the plurality of through holes 121, the housing space 130s, and the internal space 151 can be reduced. By setting the surface roughness to be equal to or more than the above-described lower limit value, the manufacturing cost of the porous plate 120, the housing portion 130, and the pipe 150 can be suppressed. The surface roughness is measured using a contact or non-contact surface roughness meter in accordance with the specifications of JIS B 0601:2013.

[0088] Next, the pump 160 will be described.

[0089] The pump 160 is connected to the lower end portion of the pipe 150. The pump 160 depressurizes the housing space 130s via the pipe 150. The pump 160 is, for example, a dry vacuum pump. However, the type of pump is not particularly limited as long as the pressure of the housing space can be depressurized to a desired pressure as described later.

[0090] Next, the flow of the supply gas G1 and the permeated gas G2 will be described.

[0091] First, as shown in FIG. 1, the supply gas G1 is supplied to the housing space 130s via the supply port 130a. Figure 2As shown, the supply gas G1 is supplied to the first surface 110a of the separation membrane 110. In a state where the accommodation space 130s is depressurized by the pump 160, the carbon dioxide gas and a part of the nitrogen gas in the supply gas G1 permeate the separation membrane 110. The permeated gas G2 including the carbon dioxide gas and the nitrogen gas that permeate the separation membrane 110 permeates the plurality of through-holes 121 of the porous plate 120. Then, the permeated gas G2 flows into the internal space 151 of the pipe 150 via the accommodation space 130s. Then, the permeated gas G2 is sucked by the pump 160 and recovered.

[0092] Therefore, in the present embodiment, the flow path FP between the separation membrane 110 and the pump 160 of the permeated gas G2 is constituted by the plurality of through-holes 121 of the porous plate 120, the accommodation space 130s, and the internal space 151 of the pipe 150.

[0093] Further, in the present embodiment, the flow path FP from the separation membrane 110 to the accommodation space 130s of the communication accommodation portion 130 and the internal space 151 of the pipe 150 is constituted to be linear. That is, in a case where the pump 160 is detached from the separation device 100 and the internal space 151 of the pipe 150 is observed from below, the porous plate 120 and the separation membrane 110 can be visually confirmed. In this way, since the flow path FP is linear, it is possible to reduce the pressure loss when the permeated gas G2 flows in the flow path FP.

[0094] Further, in the present embodiment, in a plan view, the center of the separation membrane 110, the center of the porous plate 120, the central axis C1 of the accommodation space 130s, and the center of the internal space 151 of the pipe 150 are located at substantially the same position. Therefore, compared to a case where the positions of these centers are misaligned with each other, it is possible to reduce the pressure loss when the permeated gas G2 flows in the flow path FP.

[0095] Further, in the present embodiment, the upper end portion of the internal space 151 is a portion where the permeated gas G2 flows from the accommodation portion 130 into the pipe 150 in the flow path FP. Hereinafter, the upper end portion of the internal space 151 is also referred to as a "flow inlet portion FP11" of the flow path FP. As described above, the diameter D1 of the flow inlet portion FP11 gradually decreases from the upstream to the downstream. Thereby, the permeated gas G2 is gradually contracted when flowing from the accommodation portion 130 into the pipe 150. Therefore, it is possible to reduce the pressure loss when the permeated gas G2 flows from the accommodation portion 130 into the pipe 150. In addition, in a case where the front end of the pipe is disposed in contact with the lower surface of the second wall portion of the accommodation portion, the discharge port of the accommodation portion corresponds to the flow inlet portion. Therefore, in this case, by making the diameter of the discharge port gradually smaller from the upstream to the downstream, the same effect can be obtained. However, the diameter of the flow inlet portion can also be substantially constant from the upstream to the downstream.

[0096] Next, the parameters of the separation device 100 will be described.

[0097] The carbon dioxide gas permeability of the separation membrane 110 is set to A. The nitrogen gas permeability of the separation membrane 110 is set to B. The "permeability" refers to the amount of gas permeated per unit area, per unit time, and per unit pressure. The carbon dioxide gas permeability A and the nitrogen gas permeability B are each measured by the gas permeability test method (Part 1: pressure difference method) prescribed in JIS K 7126-1:2006, using a gas permeability measuring device. As the gas permeability measuring device, for example, GTR-11A / 31A manufactured by GTR Technology Co., Ltd., or the like can be cited. The unit of the carbon dioxide gas permeability A and the nitrogen gas permeability B is, for example, GPU. In addition, 1 GPU is 3.35 x 10 -10 mol·m -2 ·s -1 ·Pa -1 In this way, the carbon dioxide gas permeability A of the separation membrane 110 and the nitrogen gas permeability B of the separation membrane 110 represent the performance of the separation membrane 110 alone in a state where the separation membrane 110 is not assembled into the separation device 100.

[0098] In the present embodiment, 500,000 GPU ≤ A ≤ 1,000 GPU. Further, it is more preferable that 400,000 GPU ≤ A ≤ 5,000 GPU, and further preferable that 300,000 GPU ≤ A ≤ 7,000 GPU. By making the carbon dioxide gas permeability A be equal to or greater than the lower limit value described above, it is possible to reduce the amount of energy input required for separation. In addition, the "amount of energy input required for separation" specifically refers to the difference between the pressure applied to the first surface 110a of the separation membrane 110 and the pressure applied to the second surface 110b. Further, in the separation membrane 110 including the resin layer 112 composed of a high molecular material, the carbon dioxide gas permeability A and the selectivity of the separation membrane 110 are in a trade-off relationship. Therefore, if the carbon dioxide gas permeability A exceeds the upper limit value described above, it can be difficult to maintain a balance with the selectivity of the separation membrane 110.

[0099] The carbon dioxide gas permeability A of the separation membrane 110 can be controlled by adjusting the material of the resin layer 112, the average diameter of the pores 113h of the porous body 111, and the average thickness of the porous body 111, and the like. Specifically, by using a material having high affinity for carbon dioxide molecules in the material of the resin layer 112, the carbon dioxide gas permeability A of the separation membrane 110 can be increased. Further, by using a material having high gas permeability in the material of the porous body 111, the carbon dioxide gas permeability A of the separation membrane 110 can be increased. Further, by increasing the average diameter of the pores 113h of the porous body 111, the carbon dioxide gas permeability A of the separation membrane 110 can be increased. Further, by reducing the average thickness of the porous body 111, the carbon dioxide gas permeability A of the separation membrane 110 can be increased. The inventors of the present application have confirmed that by configuring the material of the resin layer 112, the average diameter of the pores 113h of the porous body 111, and the average thickness of the porous body 111, and the like as described in the description of the separation membrane 110, a separation membrane 110 having 500,000 GPU ≥ A ≥ 1,000 GPU can be realized.

[0100] As shown in the following (Formula 1), the ratio of the carbon dioxide gas permeability A to the nitrogen gas permeability B is taken as the selectivity of the separation membrane 110.

[0101] Selectivity of the separation membrane 110 = A / B (Formula 1)

[0102] Hereinafter, the selectivity of the separation membrane 110 will also be referred to as "selectivity A / B". The carbon dioxide gas permeability A is larger than the nitrogen gas permeability B. Therefore, the selectivity A / B of the separation membrane 110 is greater than 1.

[0103] However, the inventors of the present application and the like have conducted intensive research, and as a result, it has been found that even if the separation membrane 110 having good selectivity A / B is assembled to the separation device 100, depending on the amount of pressure reduction of the pump 160, the selectivity of the separation device 100 can significantly decrease with respect to the selectivity A / B of the separation membrane 110. Hereinafter, the reason for this will be described.

[0104] The partial pressure of the carbon dioxide gas of the supply gas G1 is set to p1. Further, the partial pressure of the carbon dioxide gas of the permeated gas G2 in the accommodation space 130s is set to p2. In this case, when the following (Formula 2) is satisfied, it is considered that the permeation of the carbon dioxide gas in the separation membrane 110 is performed.

[0105] p1 > p2 (Formula 2)

[0106] Here, let the total pressure of the supply gas G1 be P1, and the total pressure of the permeated gas G2 in the housing space 130s be P2. Also, let the concentration of the carbon dioxide gas of the supply gas G1 be c1, and the concentration of the carbon dioxide gas of the permeated gas G2 in the housing space 130s be c2. At this time, since pi = P1-c1 and p2 = P2-c2, (Formula 2) can be transformed into the following (Formula 3).

[0107] P1-c1 > P2-c2 (Formula 3)

[0108] Further transforming (Formula 3) results in the following (Formula 4).

[0109] (P1 / P2) > c2 / c1 (Formula 4)

[0110] c2 / c1 is the ratio of the concentration c2 of the carbon dioxide gas that has permeated the separation membrane 110 to the concentration c1 of the carbon dioxide gas supplied to the separation membrane 110. Therefore, c2 / c1 will also be referred to as the "concentration ratio c2 / c1" below. The higher the concentration ratio c2 / c1, the more the carbon dioxide gas is recovered by the separation device 100. Also, as is clear from (Formula 4) above, the concentration ratio c2 / c1 is smaller than the ratio of the total pressure P1 of the supply gas G1 to the total pressure P2 of the permeated gas G2. P1 / P2 will also be referred to as the "total pressure ratio P1 / P2" below.

[0111] Also, theoretically, the concentration ratio c2 / c1 is smaller than the selection ratio A / B. Therefore, assuming that the total pressure ratio P1 / P2 is smaller than the selection ratio A / B of the separation membrane 110, the upper limit of the concentration ratio c2 / c1 becomes a value (total pressure ratio P1 / P2) that is further lower than the selection ratio A / B of the separation membrane 110 selected when the separation device 100 is assembled. On the other hand, assuming that the total pressure ratio P1 / P2 is equal to or higher than the selection ratio A / B of the separation membrane 110, the upper limit of the concentration ratio c2 / c1 becomes the selection ratio A / B of the separation membrane 110 selected when the separation device 100 is assembled. That is, the case where the total pressure ratio P1 / P2 is equal to or higher than the selection ratio A / B of the separation membrane 110 enables the concentration ratio c2 / c1 to be improved compared to the case where the total pressure ratio P1 / P2 is smaller than the selection ratio A / B of the separation membrane 110.

[0112] Therefore, if (Formula 5) below is satisfied, it is considered that the concentration ratio c2 / c1 of the separation device 100 can be improved.

[0113] (P1 / P2) ≥ (A / B) (Formula 5)

[0114] Transforming (Formula 5) results in the following (Formula 6).

[0115] (P1 / P2) / A / B ≥ 1 (Formula 6)

[0116] The total pressure ratio P1 / P2 can be controlled by adjusting the pressure reduction of pump 160. Specifically, the more pump 160 reduces the pressure of the containment space 130s, the lower the total pressure P2 and the larger the total pressure ratio P1 / P2.

[0117] However, the larger the total pressure ratio P1 / P2, the more energy is required to drive the pump 160. Furthermore, the larger the total pressure ratio P1 / P2, the greater the difference between the pressure applied to the first surface 110a and the pressure applied to the second surface 110b of the separation membrane 110. As a result, the lifespan of the separation membrane 110, i.e., the period until it breaks due to repeated or continuous pressure application, is shortened. Therefore, although not particularly limited, it is preferable to have a ratio of 15 ≥ (P1 / P2) / (A / B).

[0118] The measurement methods for total pressures P1 and P2 are explained here. Figure 2 As shown, for example, a pressure gauge PS1, such as a barometer, is disposed on the outside of the separation device 100 and around the periphery of the separation membrane 110. Furthermore, for example, a pressure gauge PS2, such as a gauge pressure measuring instrument, is disposed in the through hole formed in the receiving portion 130. The total pressure P1 of the supplied gas G1 can be obtained as absolute pressure using pressure gauge PS1. The total pressure P2 of the permeated gas G2 can be obtained as the sum of the gauge pressure measured by pressure gauge PS2 and atmospheric pressure (absolute pressure). However, the type of pressure gauge used to measure the total pressure P1 of the supplied gas G1 and the total pressure P2 of the permeated gas G2 is not particularly limited, as long as the final total pressures P1 and P2 are obtained according to absolute pressure.

[0119] As explained above, it is assumed that the concentration ratio c2 / c1 decreases significantly due to variations in the pressure reduction of pump 160 (Equation 6). This decrease in concentration ratio c2 / c1 refers to a reduction in the carbon dioxide gas permeation rate of separation device 100. Therefore, it is assumed that the selectivity of separation device 100 decreases significantly relative to the selectivity A / B of separation membrane 110.

[0120] However, the inventors of this application conducted further research and found that even when the separation device 100 is configured in a manner that satisfies (Formula 6), the selectivity of the separation device 100 relative to the selectivity A / B of the separation membrane 110 still decreases significantly. This is believed to be because by configuring the separation device 100 in a manner that satisfies (Formula 6), the flow rate and velocity of the permeate gas G2 increase, leading to an increase in pressure loss in the flow path FP between the separation membrane 110 and the pump 160, making it difficult for the permeate gas G2 to flow. Therefore, the inventors of this application believe that it is important to consider not only the total pressure ratio P1 / P2 but also the gas permeability of the flow path FP.

[0121] Figure 4is a schematic view showing a measurement method of the gas permeability of the flow path FP in the present embodiment. In the figure, a part of the pipe is simplified and indicated by a solid line.

[0122] A gas permeability measuring device 10 is used in the measurement of the gas permeability of the flow path FP. The gas permeability measuring device 10 is provided with a gas supply portion 11, an upstream side pressure gauge 12, a downstream side pressure gauge 13, a flow meter 14, a vacuum pump 15, and a concentration gauge 16. First, the portion that constitutes the flow path FP in the separation device 100, i.e., the porous plate 120, the housing portion 130, and the pipe 150 are arranged between the gas supply portion 11 and the vacuum pump 15. Also, the gas supply portion 11 and the inlet of the flow path FP are connected by a pipe or the like. In addition, the outlet of the flow path FP and the vacuum pump 15 are connected by a pipe or the like.

[0123] The gas supply portion 11 is constituted by, for example, a gas tank and a mass flow controller or the like. The gas supplied by the gas supply portion 11 is a gas that is the main component of the permeated gas G2. In the present embodiment, the supplied gas G1 is air, and the concentration and partial pressure of nitrogen gas in the supplied gas G1 are much higher than the concentration and partial pressure of carbon dioxide gas. Therefore, although the carbon dioxide gas permeability A of the separation membrane 110 is higher than the nitrogen gas permeability B, the permeated amount of nitrogen gas is more than that of carbon dioxide gas. That is, in the present embodiment, the gas that is the main component of the permeated gas G2 is nitrogen gas. Therefore, the gas supply portion 11 supplies a single gas of nitrogen gas. However, in the case where the supplied gas is not air and the concentration and partial pressure of carbon dioxide gas in the supplied gas are higher than those of nitrogen gas, the gas that is the main component of the permeated gas becomes carbon dioxide gas. In this case, the gas supply portion can supply only carbon dioxide gas.

[0124] In the measurement of the gas permeability of the flow path FP, first, the flow path FP is depressurized to 3 kPa by the vacuum pump 15. Next, the gas is supplied to the inlet of the flow path FP at 103 kPa by the gas supply portion 11. In the present embodiment, the inlet of the flow path FP is the porous plate 120. Thereby, the gas starts to flow in the flow path FP. Also, the vacuum pump 15 sucks the gas that permeates the flow path FP. At this time, the absolute pressure of the gas supplied to the inlet of the flow path FP is measured by the upstream side pressure gauge 12. In addition, the absolute pressure of the gas that permeates the outlet of the flow path FP is measured by the downstream side pressure gauge 13. Furthermore, the volume of the gas that permeates the outlet of the flow path FP per unit time is measured by the flow meter 14. Furthermore, the mass of the substance per unit volume of the gas recovered by the vacuum pump 15 is measured by the concentration gauge 16. In addition, other test conditions such as the test temperature are as much as possible in accordance with JIS K 7126-1:2006.

[0125] After the gas is supplied, the flow rate of the gas that permeates the flow path FP and the absolute pressure on the downstream side of the flow path FP gradually increase, and thereafter, the flow rate and the absolute pressure become a substantially constant steady state. The absolute pressure on the upstream side in the steady state is set to P3, and the absolute pressure on the downstream side is set to P4. Further, the amount of substance per unit time of the gas that permeates the outlet of the flow path FP is calculated from the volume per unit time of the gas in the steady state and the amount of substance per unit volume of the gas. This amount of substance per unit time is set to n. Further, the area to which the gas at the inlet of the flow path FP is supplied is set to s1. In the present embodiment, the area s1 to which the gas at the inlet of the flow path FP is supplied corresponds to the area of the upper surface of the porous plate 120.

[0126] The gas permeability of the flow path FP is set to C. By substituting the above-described values into the following (Formula 7), the gas permeability C of the flow path FP can be calculated.

[0127] C = n / {(P3 - P4) • s1} (Formula 7)

[0128] The unit of the above-described gas permeability C is mol · m -2 · s -1 · Pa -1 . The gas permeability C is used together with the carbon dioxide gas permeability A and the nitrogen gas permeability B for the calculation of the parameters described later. Therefore, the unit of the gas permeability C needs to be consistent with the units of the carbon dioxide gas permeability A and the nitrogen gas permeability B. In the case where the GPU is used as the unit of the carbon dioxide gas permeability A and the nitrogen gas permeability B, the value calculated from (Formula 7) is divided by 3.35 x 10 -10 . As a result of the measurement using the gas that is the main component of the permeated gas G2, the gas permeability C can be regarded as the permeability of the flow path FP with respect to the permeated gas G2. In addition, with respect to the measurement of the carbon dioxide gas permeability A and the nitrogen gas permeability B, the gas permeability measuring device 10 can also be used. In this case, as with JIS K 7126-1:2006, it is sufficient to connect the upstream side of the chamber and the gas supply part 11 with a pipe, and to connect the downstream side of the chamber and the vacuum pump 15 with a pipe, in a state where the separation membrane 110 is provided to the chamber. In addition, in the case of measuring the carbon dioxide gas permeability A, the gas supply part 11 supplies a single gas of carbon dioxide gas, and in the case of measuring the nitrogen gas permeability B, the gas supply part 11 supplies a single gas of nitrogen gas.

[0129] In theory, in the case where two gas permeation bodies are arranged in a continuous manner, if the gas permeability of the gas permeation body on the upstream side is set to x, and the gas permeability of the gas permeation body on the downstream side is set to y, it can be considered that the gas permeability z of the entire of the two gas permeation bodies in combination is represented by the following (Formula 8).

[0130] 1 / z = 1 / x + 1 / y (Formula 8)

[0131] By transforming (Formula 8), the following (Formula 9) is obtained.

[0132] z = (xy) / (x+y) (Formula 9)

[0133] The separation membrane 110 can be understood as a gas permeable body on the upstream side, and the flow path FP can be understood as a gas permeable body on the downstream side. Therefore, when the carbon dioxide gas permeability of the separation device 100 is set to zl, it is considered that the carbon dioxide gas permeability zl of the separation device 100 can be represented by the following (Formula 10) by the synthesis of the carbon dioxide gas permeability A of the separation membrane 110 and the gas permeability C of the flow path FP.

[0134] zl = (AC) / (A+C) (Formula 10)

[0135] Similarly, when the nitrogen gas permeability of the separation device 100 is set to z2, it is considered that the nitrogen gas permeability z2 of the separation device 100 can be represented by the following (Formula 11).

[0136] z2 = (BC) / (B+C) (Formula 11)

[0137] The selectivity of the separation device 100 is set to a. In the case based on (Formula 10) and (Formula 11), it is considered that the selectivity a of the separation device 100 can be represented by the following (Formula 12).

[0138] a = zl / z2 = {(B+C) / (A+C)} · (A / B) (Formula 12)

[0139] According to (Formula 12), it is considered that the selectivity a of the separation device 100 is obtained by multiplying the selectivity A / B of the separation membrane 110 by (B+C) / (A+C). Therefore, (B+C) / (A+C) can be understood as a rate of selectivity.

[0140] Hereinafter, (B+C) / (A+C) is also referred to as "a rate of selectivity (B+C) / (A+C)". In the rate of selectivity (B+C) / (A+C), the carbon dioxide gas permeability A and the nitrogen gas permeability B are determined by the performance of the separation membrane 110 assembled in the separation device 100. Moreover, the nitrogen gas permeability B is smaller than the carbon dioxide gas permeability A. Therefore, regardless of the value of the gas permeability C of the flow path FP, the rate of selectivity (B+C) / (A+C) should be less than 1. Moreover, the greater the value of the gas permeability C of the flow path FP, the more the influence of the magnitude of the carbon dioxide gas permeability A and the nitrogen gas permeability B can be reduced, and the closer the rate of selectivity (B+C) / (A+C) to 1.

[0141] Therefore, it is important to increase the gas permeation rate C of the flow path FP in order to increase the selection ratio a of the separation device 100. Further, in a case where only the influence of the gas permeation rate C is considered, if the flow path FP of the separation device 100 is designed in a manner satisfying the following (Formula 13), it can be considered that the selection ratio a of the separation device 100 can be made to be less than 100% of the selection ratio A / B of the separation membrane 110 and 80% or more.

[0142] 1> (B+C) / (A+C) ≥ 0.8 (Formula 13)

[0143] However, in reality, there is a case where the selection ratio a of the separation device 100 does not become 80% or more of the selection ratio A / B of the separation membrane 110 even if the above (Formula 13) is satisfied due to other reasons such as insufficient pressure reduction amount of the pump 160. As described above, (B+C) / (A+C) does not necessarily correspond to the multiple of the selection ratio, however, for convenience of explanation, in the following description, (B+C) / (A+C) is also referred to as the multiple of the selection ratio.

[0144] The gas permeation rate C of the flow path FP can be increased by reducing the pressure loss of the flow path FP. The pressure loss of the flow path FP can be adjusted, for example, in accordance with the area in plan view of the separation membrane 110, the length of the flow path FP, the surface roughness of the flow path FP, the number of curved portions of the flow path FP, and the like. The shorter the length of the flow path FP, the smaller the pressure loss. The length of the flow path FP can be adjusted, for example, in accordance with the thickness of the porous plate 120, the length from the intake port 130a to the discharge port 130b of the housing space 130s, the length of the pipe 150, and the like. The smaller the surface roughness of the flow path FP, the smaller the pressure loss. In the present embodiment, the surface roughness of the flow path FP can be adjusted by the surface roughness of the surface of the through-hole 121 of the porous plate 120, the surface roughness of the inner surface of the housing portion 130, and the surface roughness of the inner surface of the pipe 150. The smaller the number of curved portions of the flow path FP, the smaller the pressure loss. The number of curved portions of the flow path FP can be adjusted in accordance with the shape of the housing space 130s of the housing portion 130 and the internal space 151 of the pipe 150.

[0145] Further, in the flow path FP, the smaller the contraction rate in a case where the permeated gas G2 is contracted, the smaller the pressure loss. In the present embodiment, the permeated gas G2 is contracted when the permeated gas G2 flows from the housing space 130s into the internal space of the pipe 150. Therefore, the smaller the diameter of the internal space 151 of the pipe 150 is made to be in comparison with the diameter of the housing space 130s, the smaller the pressure loss. Further, the pressure loss when the permeated gas G2 is gradually contracted is smaller than the pressure loss when the permeated gas G2 is contracted all at once. Therefore, as described above, by gradually reducing the diameter D1 of the flow inlet portion FP11 of the flow path FP from the upstream to the downstream, it is possible to reduce the pressure loss.

[0146] Further, in the flow path, in a case where there is a portion in which the permeated gas G2 expands, the smaller the expansion rate, the smaller the pressure loss. In the present embodiment, the permeated gas G2 expands when the permeated gas G2 flows from each through-hole 121 of the porous plate 120 into the accommodation space 130s. Therefore, the larger the diameter of each through-hole 121 of the porous plate 120, the smaller the pressure loss.

[0147] Further, by forming the shape of the accommodation space 130s into a shape in which the permeated gas G2 stagnates, it is possible to reduce the pressure loss. In the present embodiment, the shape of the accommodation space 130s is cylindrical. Therefore, compared to a case where the accommodation space 130s is a rectangular parallelepiped or a polyhedral shape, it is possible to reduce the pressure loss.

[0148] In this way, the inventors of the present application have ascertained that, in order to make the selection ratio a of the separation device 100 good with respect to the selection ratio A / B of the separation membrane 110, it is important to consider both the total pressure ratio P1 / P2 and the gas permeation rate C of the flow path FP.

[0149] Next, a design method of the separation device 100 based on the above will be described.

[0150] Figure 5 is a flowchart showing a design method of the separation device 100 according to the present embodiment.

[0151] The design method of the separation device 100 includes a step S1 of selecting a separation membrane 110 and a step S2 of designing an accommodation portion 130, a pipe 150, and a pump 160. Each step will be described in detail below.

[0152] In the selection step S1, a separation membrane that is 500,000 GPU ≥ A ≥ 1,000 GPU is selected as the separation membrane 110 to be assembled in the separation device 100.

[0153] In the design step S2, a pump that can depressurize the accommodation space 130s of the accommodation portion 130 is selected as the pump 160 to be assembled in the separation device 100 so that (P1 / P2) / (A / B) ≥ 1. Further, in the design step S2, the flow path FP between the separation membrane 110 and the pump 160 is designed so that 1 > (B+C) / (A+C) ≥ 0.8.

[0154] In this way, the values of the total pressure ratio P1 / P2 and the gas permeation rate C of the flow path FP required for the separation device 100 are ascertained based on the carbon dioxide gas permeation rate A and the nitrogen gas permeation rate B of the separation membrane 110 selected in the selection step S1. Therefore, the design of the separation device 100 becomes easy. As a result, it is possible to easily obtain a separation device 100 having a good selection ratio a with respect to the selection ratio A / B of the separation membrane 110.

[0155] Next, the effects of the present embodiment will be described.

[0156] The separation device 100 is a separation device that selectively separates carbon dioxide gas from a supply gas G1 including carbon dioxide gas and nitrogen gas. The separation device 100 includes a separation membrane 110, a housing portion 130, a pipe 150, and a pump 160. The separation membrane 110 includes a porous body 111 and a resin layer 112 that is disposed on the porous body 111 and selectively allows carbon dioxide gas included in the supply gas G1 to permeate the porous body 111. The housing portion 130 has a housing space 130s that holds the separation membrane 110 and houses a permeated gas G2 that has permeated the separation membrane 110. The pipe 150 is connected to the housing portion 130. The pump 160 depressurizes the housing space 130s via the pipe 150 and sucks the permeated gas G2. When the carbon dioxide gas permeability of the separation membrane 110 is A, 500,000 GPU ≥ A ≥ 1,000 GPU. When the nitrogen gas permeability of the separation membrane 110 is B, the total pressure of the supply gas G1 is P1, and the total pressure of the permeated gas G2 in the housing space 130s is P2, (P1 / P2) / (A / B) ≥ 1. A flow path FP between the separation membrane 110 and the pump 160 of the permeated gas G2 includes the housing space 130s and an internal space 151 of the pipe 150. When the gas permeability of the flow path FP is C, 1 > (B+C) / (A+C) ≥ 0.8.

[0157] In the separation device 100 described above, (P1 / P2) / (A / B) ≥ 1, and thus the concentration ratio c2 / c1 can be increased. The concentration ratio c2 / c1 being high means that the carbon dioxide gas permeability z1 of the separation device 100 is high. Thus, the selectivity ratio a of the separation device 100 can be increased. Further, by making 1 > (B+C) / (A+C) ≥ 0.8, the ratio (B+C) / (A+C) of the selectivity ratio can be increased. Thus, the separation device 100 having a good selectivity ratio a with respect to the selectivity ratio A / B of the separation membrane 110 can be realized.

[0158] Further, 15 ≥ (P1 / P2) / (A / B). Thus, an increase in the energy required for driving the pump 160 can be suppressed. Further, a reduction in the life of the separation membrane 110 can be suppressed.

[0159] Further, in the flow path FP, the diameter D1 of the permeated gas G2 flowing from the housing portion 130 into the inlet portion FP11 of the pipe 150 gradually decreases from the upstream side to the downstream side. Thus, the pressure loss when the permeated gas G2 is constricted can be reduced. As a result, the gas permeability C of the flow path FP can be increased.

[0160] Further, a flow path FP from the separation membrane 110 to the accommodation space 130s of the communication accommodation portion 130 and the internal space 151 of the pipe 150 is linear. Therefore, it is possible to reduce the pressure loss when the permeated gas G2 flows in the flow path FP. As a result, it is possible to improve the gas permeation rate C of the flow path FP.

[0161] Further, the pipe 150 extends linearly. Therefore, it is possible to reduce the pressure loss when the permeated gas G2 flows in the pipe 150. As a result, it is possible to improve the gas permeation rate C of the flow path FP.

[0162] Further, the porous body 111 includes a high molecular material, a ceramic material, or a metal material. In the case where the porous body 111 includes a high molecular material, it is possible to improve the gas permeation rate of the porous body 111. In the case where the porous body 111 includes a ceramic material or a metal material, it is possible to improve the mechanical strength of the porous body 111.

[0163] Further, the resin layer 112 includes an organopolysiloxane. Thereby, it is possible to improve the carbon dioxide gas permeation rate of the resin layer 112. As a result, it is possible to improve the selectivity ratio A / B of the separation membrane 110.

[0164] Further, the design method of the separation device 100 is a design method of the separation device 100 that selectively separates carbon dioxide gas from a supply gas G1 including carbon dioxide gas and nitrogen gas. The design method of the separation device 100 includes a step S1 of selecting a separation membrane 110 and a step S2 of designing a housing portion 130, a pipe 150, and a pump 160. The separation membrane 110 includes a porous body 111 and a resin layer 112 that is disposed on the porous body 111 and that allows carbon dioxide gas included in the supply gas G1 to permeate toward the porous body 111. The housing portion 130 is formed with a housing space 130s that holds the separation membrane 110 and that houses a permeated gas G2 that has permeated the separation membrane 110. The pipe 150 is connected to the housing portion 130. The pump 160 depressurizes the housing space 130s via the pipe 150 and sucks the permeated gas G2. A flow path FP between the separation membrane 110 and the pump 160 of the permeated gas G2 includes the housing space 130s and an internal space 151 of the pipe 150. In the step S1 of selecting, when a carbon dioxide gas permeability of the separation membrane 110 is set to A, the separation membrane 110 that becomes 500,000 GPU ≥ A ≥ 1000 GPU is selected. In the step S2 of designing, when a nitrogen gas permeability of the separation membrane 110 is set to B, a total pressure of the supply gas G1 is set to P1, and a total pressure of the permeated gas G2 in the housing space 130s is set to P2, the pump 160 that depressurizes the housing space 130s is selected so that (P1 / P2) / (A / B) ≥ 1. Further, in the step S2 of designing, when a gas permeability of the flow path is set to C, the flow path FP is designed so that 1 > (B+C) / (A+C) ≥ 0.8.

[0165] According to the design method of the separation device 100 described above, the designer can easily grasp the total pressure ratio P1 / P2 required for the separation device 100 and the gas permeability C required for the flow path FP on the basis of the carbon dioxide gas permeability A and the nitrogen gas permeability B of the selected separation membrane 110. Therefore, the designer can easily design the separation device 100 that has a good selection ratio a with respect to the selection ratio A / B of the separation membrane 110. Further, since the performance required for the pump 160 and the gas permeability C required for the flow path FP are clear, it is possible to suppress selection of the pump 160 having an excessive performance or excessive reduction of the pressure loss of the flow path FP when designing the separation device 100. Thus, it is possible to reduce the manufacturing cost of the separation device 100.

[0166] Further, in the designing step S2, the shape of the housing space 130s, the inner diameter of the pipe 150, the length of the flow path FP, the surface roughness of the flow path FP, or the number of the curved portions of the flow path FP is adjusted so that 1 > (B + C) / (A + C) ≥ 0.8. Thereby, it is possible to realize the separation device 100 having a good selection ratio a with respect to the selection ratio A / B of the separation membrane 110.

[0167] Second Embodiment

[0168] Next, the separation device 200 according to the second embodiment will be described.

[0169] Figure 6 is a cross-sectional view illustrating the separation device 200 according to the second embodiment.

[0170] The separation device 200 differs from the separation device 100 according to the first embodiment in that the separation device 200 further includes another separation membrane 210, another porous plate 220, another housing portion 230, another fixing member 240, and another pipe 250. Hereinafter, mainly the difference between the second embodiment and the first embodiment will be described, and the description of the same structure as the first embodiment will be appropriately omitted. The same applies to the description of the modified example described later.

[0171] The separation membrane 110 is also referred to as "first separation membrane 110". The porous plate 120 is also referred to as "first porous plate 120". The housing portion 130 is also referred to as "first housing portion 130". The pipe 150 is also referred to as "first pipe 150". The other separation membrane 210 is also referred to as "second separation membrane 210". The other porous plate 220 is also referred to as "second porous plate 220". The other housing portion 230 is also referred to as "second housing portion 230". The fixing member 140 is also referred to as "first fixing member 140". The other fixing member 240 is also referred to as "second fixing member 240". The other pipe 250 is also referred to as "second pipe 250".

[0172] The second separation membrane 210 selectively permeates the carbon dioxide gas included in the supply gas G1. Hereinafter, the gas permeated through the second separation membrane 210 is referred to as "other permeated gas G3". The second separation membrane 210 includes the other porous body 211 and an other resin layer 212 disposed on the other porous body 211 and selectively permeating the carbon dioxide gas included in the supply gas G1 to the other porous body 211. The other porous body 211 is configured in the same manner as the porous body 111 of the first separation membrane 110. The other resin layer 212 is configured in the same manner as the resin layer 112 of the first separation membrane 110. Therefore, the selection ratio of the second separation membrane 210 is substantially the same as the selection ratio A / B of the first separation membrane 110.

[0173] The second porous plate 220 is arranged below the second separation membrane 210 and supports the second separation membrane 210. The second porous plate 220 is configured similarly to the first porous plate 120.

[0174] The second housing portion 230 is formed with a further housing space 230s that houses further permeated gas G3. The second housing portion 230 is configured similarly to the first housing portion 130. In the present embodiment, the second housing portion 230 is partitioned from the first housing portion 130, and the further housing space 230s is partitioned from the housing space 130s. However, the first housing portion and the second housing portion can be in contact, and the first housing portion and the second housing portion can be integrated, as long as the housing space is partitioned from the further housing space.

[0175] The second fixing member 240 fixes the second separation membrane 210 and the second porous plate 220 to the second housing portion 230. The second fixing member 240 is configured similarly to the first fixing member 140. In the present embodiment, the lower end portion of the first pipe 150 is not directly connected to the pump 160. The upper end portion of the second pipe 250 is connected to the second housing portion 230. The second pipe 250 is configured similarly to the first pipe 150.

[0176] The separation device 200 further includes a third pipe 270 connected to the lower end portion of the first pipe 150 and the lower end portion of the second pipe 250, and a fourth pipe 280 connecting the third pipe 270 and the pump 160. The third pipe 270 extends linearly from the lower end portion of the first pipe 150 to the lower end portion of the second pipe 250. The internal space of the third pipe 270 communicates with the internal space 151 of the first pipe 150 and the internal space of the second pipe 250. The fourth pipe 280 extends in the Z-axis direction. The upper end portion of the fourth pipe 280 is connected to the substantially central portion of the third pipe 270 in the longitudinal direction. The internal space of the fourth pipe 280 communicates with the internal space of the third pipe 270. The lower end portion of the fourth pipe 280 is connected to the pump 160.

[0177] The fourth pipe 280 is connected to the third pipe 270 in such a manner that the upper end of the fourth pipe 280 is substantially flush with the inner surface of the third pipe 270. The diameter D2 of the upper end portion of the internal space of the fourth pipe 280 gradually decreases from the upstream to the downstream. Thus, the pressure loss when the permeated gas G2 and the further permeated gas G3 flow from the third pipe 270 into the fourth pipe 280 can be reduced.

[0178] The pump 160 depressurizes the housing space 130s via the first pipe 150, the third pipe 270, and the fourth pipe 280. In addition, the pump 160 depressurizes the further housing space 230s via the second pipe 250, the third pipe 270, and the fourth pipe 280.

[0179] Next, the flow of the permeated gas G2 and the other permeated gas G3 through the separation device 200 will be described.

[0180] The permeated gas G2 that has permeated the first separation membrane 110 is drawn by the pump 160 via the first porous plate 120, the first housing portion 130, the first pipe 150, the third pipe 270, and the fourth pipe 280, and is recovered. The other permeated gas G3 that has permeated the second separation membrane 210 is drawn by the pump 160 via the second porous plate 220, the second housing portion 230, the second pipe 250, the third pipe 270, and the fourth pipe 280, and is recovered.

[0181] The flow path between the first separation membrane 110 of the permeated gas G2 and the pump 160 is set as "flow path FP1". The flow path FP1 includes the plurality of through holes 121 of the first porous plate 120, the housing space 130s of the first housing portion 130, the internal space 151 of the first pipe 150, a part of the internal space of the third pipe 270, and the internal space of the fourth pipe 280. The flow path between the second separation membrane 210 of the other permeated gas G3 and the pump 160 is set as "other flow path FP2". The other flow path FP2 includes the plurality of through holes of the second porous plate 220, the other housing space 230s of the second housing portion 230, the internal space of the second pipe 250, a part of the internal space of the third pipe 270, and the internal space of the fourth pipe 280. With respect to the plane P that is parallel to the Z-X plane and that is positioned between the first housing portion 130 and the second housing portion 230, the shape of the flow path FP1 and the shape of the other flow path FP2 are substantially face symmetrical.

[0182] Figure 7 is a schematic view showing a measurement method of the gas permeability C of the flow path FP1 in the present embodiment. In the drawing, the partial pipes are simplified and are indicated by solid lines.

[0183] First, both the portion that constitutes the flow path FP1 in the separation device 200 and the portion that constitutes the other flow path FP2 are disposed between the gas supply portion 11 and the vacuum pump 15 of the gas permeability measurement device 10. That is, the first porous plate 120, the first housing portion 130, the first pipe 150, the second porous plate 220, the second housing portion 230, the second pipe 250, the third pipe 270, and the fourth pipe 280 are disposed between the gas supply portion 11 and the vacuum pump 15. Moreover, the gas supply portion 11 and the inlet of the flow path FP1 and the gas supply portion 11 and the inlet of the other flow path FP2 are connected by pipes. In addition, the outlets of the flow path FP1 and the other flow path FP2 are connected to the vacuum pump 15 by pipes.

[0184] Next, the flow path FP1 and the other flow path FP2 are depressurized by the vacuum pump 15. Next, the gas is supplied to the inlet of the flow path FP1 and the other flow path FP2 by the gas supply portion 11. The gas that has passed through the flow path FP1 and the other flow path FP2 is sucked by the vacuum pump 15. At this time, the absolute pressure of the gas supplied to the inlet of the flow path FP1 or the other flow path FP2 is measured by the pressure gauge 12 on the upstream side. In addition, the absolute pressure of the gas that has passed through the outlet of the flow path FP1 and the other flow path FP2 is measured by the pressure gauge 13 on the downstream side. In addition, the volume of the gas that has passed through the outlet of the flow path FP1 and the other flow path FP2 per unit time is measured by the flow meter 14. In addition, the mass of the substance per unit volume of the gas recovered by the vacuum pump 15 is measured by the concentration gauge 16.

[0185] The sum of the area to which the gas of the inlet of the flow path FP1 is supplied and the area to which the gas of the inlet of the other flow path FP2 is supplied is set as s1. In the present embodiment, the area s1 corresponds to the sum of the area of the upper surface of the first porous plate 120 and the area of the upper surface of the second porous plate 220. As with the first embodiment, by substituting the absolute pressure P3 on the upstream side, the absolute pressure P4 on the downstream side, the mass of the substance n per unit time, and the area s1 into (Formula 7), the gas permeation rate C can be calculated.

[0186] The gas permeation rate C indicates the mass of the substance of the gas that has permeated per unit time, unit pressure, and unit area. In addition, as described above, the shape of the flow path FP1 and the shape of the other flow path FP2 are substantially symmetrical. Therefore, the calculated gas permeation rate C can be the gas permeation rate of the flow path FP1 or the gas permeation rate of the other flow path FP2. In addition, in a case where a plurality of flow paths are assumed to exist, the gas permeation rates of the plurality of flow paths are different from each other, as long as the above-described measurement method is implemented in a state where the flow paths other than the flow path to be measured are occluded.

[0187] In the present embodiment, the first separation membrane 110 and the second separation membrane 210 are configured similarly. Therefore, if 500,000 GPU ≥ A ≥ 1,000 GPU, (P1 / P2) / (A / B) ≥ 1, and 1 > (B+C) / (A+C) ≥ 0.8 are satisfied, the separation device 200 having a good selection ratio a with respect to the selection ratio A / B of both the first separation membrane 110 and the second separation membrane 210 can be obtained.

[0188] In addition, in a case where a plurality of separation membranes are provided to the separation device and the selection ratios of the plurality of separation membranes are different from each other, it is preferable that the above-described three inequalities are satisfied for all of the separation membranes. However, if the above-described three inequalities are satisfied with respect to the selection ratio of at least one separation membrane, the separation device having a good selection ratio with respect to the selection ratio of at least one separation membrane can be obtained. Note that the number of separation membranes provided to the separation device can be three or more.

[0189] Further, the separation device 200 according to the present embodiment is provided with a further separation membrane 210, a further housing portion 230, and a further pipe 250. The further separation membrane 210 includes a further porous body 211 and a further resin layer 212 that is disposed on the further porous body 211 and allows carbon dioxide gas contained in the supply gas G1 to selectively permeate the further porous body 211. The further housing portion 230 is formed with a further housing space 230s that holds the further separation membrane 210 and houses further permeated gas G3 that has permeated the further separation membrane 210. The further pipe 250 is connected to the further housing portion 230. The pump 160 depressurizes the further housing space 230s via the further pipe 250. Thus, a flow path from the separation membrane 110 to the pipe 150 and a flow path from the further separation membrane 210 to the further pipe 250 can be formed separately. Therefore, the separation device 200 can reduce pressure loss compared to a case in which the permeated gas of a plurality of separation membranes flows into one housing portion and one pipe.

[0190] Modified Example 1

[0191] Next, the separation membrane 310 of Modified Example 1 will be described.

[0192] Figure 8 is a cross-sectional view that shows the separation membrane 310 according to the present modified example.

[0193] The separation membrane 310 differs from the separation membrane 110 of the first embodiment in that the porous body 311 includes a plurality of porous layers 313, 314 that are stacked.

[0194] The porous layer 313 is formed with a plurality of pores 313h. Each of the pores 313h penetrates the porous layer 313 in the thickness direction. The plurality of pores 313h are dispersedly formed on the X-Y plane. The porous layer 314 is disposed on the porous layer 313. The resin layer 112 is disposed on the porous layer 314. The porous layer 314 is formed with a plurality of pores 314h. Each of the pores 314h penetrates the porous layer 314 in the thickness direction. The plurality of pores 314h are formed in a manner of being dispersed on the X-Y plane. The diameter of the pores 313h is larger than the diameter of the pores 314h.

[0195] That is, in each of the plurality of porous layers 313, 314, a hole 313h, 314h is formed that penetrates each of the plurality of porous layers 313, 314 in the thickness direction. Furthermore, the larger the diameter of the hole 313h of the porous layer 313 farther away from the resin layer 112. Thus, the flow of carbon dioxide gas that has passed through the resin layer 112 gradually expands when passing through the porous body 311 and reaches the accommodation space 130s. Therefore, it is possible to reduce the pressure loss. Moreover, since the diameter of the hole 314h of the porous layer 314 closer to the resin layer 112 is smaller, the porous body 311 is able to support the resin layer 112 well. Thus, it is possible to improve the mechanical strength of the separation membrane 310.

[0196] Modified Example 2

[0197] Next, the separation membrane 410 according to the modified example 2 will be described.

[0198] Figure 9 is a cross-sectional view showing the separation membrane 410 according to the present modified example.

[0199] The separation membrane 410 differs from the separation membrane 110 in the first embodiment in terms of the shape of the hole 413h formed in the porous body 411.

[0200] The porous body 411 includes a porous layer 413 that supports the resin layer 112. The porous layer 413 is formed with a hole 413h that penetrates the porous layer 413 in the thickness direction. In the direction from the resin layer 112 toward the porous layer 413, the diameter of the hole 413h continuously increases. That is, the shape of the hole 413h is a frustum. Thus, the flow of carbon dioxide gas that has passed through the resin layer 112 gradually expands when passing through the porous body 411 and reaches the accommodation space 130s. Therefore, it is possible to reduce the pressure loss. Moreover, in the porous layer 413, the smaller the diameter of the hole 413h closer to the resin layer 112, and thus the porous layer 413 is able to support the resin layer 112 well. Thus, it is possible to improve the mechanical strength of the separation membrane 410.

[0201] Modified Example 3

[0202] Next, the separation membrane 510 according to the modified example 3 will be described.

[0203] Figure 10 is a cross-sectional view showing the separation membrane 510 according to the present modified example.

[0204] The separation membrane 510 differs from the separation membrane 410 in the modified example 2 in terms of the shape of the hole 513h formed in the porous body 511.

[0205] The porous body 511 includes a porous layer 513 that supports the resin layer 112. The porous layer 513 is formed with a void 513h that penetrates the porous layer 513 in the thickness direction. The diameter of the void 513h gradually increases in the direction from the resin layer 112 toward the porous layer 513. With this structure, the same effect as in Modification 2 can also be obtained.

[0206] In addition, the shape of the void 413h, 513h in Modification 2 or Modification 3 can also be applied to the void 313h, 314h in Modification 1. That is, the diameter of the void 313h can also continuously or gradually increase away from the resin layer 112. The same applies to the void 314h. In this case, it is preferable that the diameter of the void 313h on the upper surface of the porous layer 313 be larger than the diameter of the void 314h on the lower surface of the porous layer 314.

[0207] Embodiments

[0208] Next, the embodiments will be described.

[0209] Figure 11 is a cross-sectional view showing the separation device 900 related to Comparative Example 1.

[0210] Figure 12 is Table 1 showing the structures of the separation devices of Embodiments 1 to 3 and the separation devices of Comparative Examples 1 to 3 and the evaluation results.

[0211] The selectivity ratio a of the separation device was simulated using a table calculation software, depending on how the amount of pressure reduction of the pump of the separation device and the gas permeability C of the flow path varied.

[0212] The separation devices related to Embodiments 1, 2, 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were set. The atmospheric temperature of each separation device was set to 20°C. In addition, the supply gas supplied to each separation device included carbon dioxide gas and nitrogen gas. The atmosphere was simulated, the total pressure PI of the supply gas was set to 103 kPa, and the concentration of the carbon dioxide gas was set to 400 ppm.

[0213] The separation device related to Embodiment 1 was set to the same structure as the separation device 200 related to the second embodiment. That is, it was assumed that the separation device related to Embodiment 1 was provided with a first separation membrane, a first porous plate, a first housing portion, a first pipe, a second separation membrane, a second porous plate, a second housing portion, a second pipe, a third pipe, a fourth pipe, and a pump. Furthermore, as shown in Table 1, the carbon dioxide gas permeability A and the nitrogen gas permeability B of the separation membrane were set. The selectivity ratio A / B of the separation membrane was calculated from the carbon dioxide gas permeability A and the nitrogen gas permeability B.

[0214] Further, the total pressure immediately before the pump in Example 1 was set to 0.040 kPa. The total pressure immediately before the pump corresponds to the pressure reduction amount of the pump. Further, although not shown in the table, a set value of the flow path based on the loss coefficient of each separation membrane, the opening area and the thickness of each porous plate, the inner diameter and the total length of each housing, the inner diameter and the total length of each pipe, and the shape of each flow inlet portion, and the like was set. In addition, the area of each separation membrane corresponds to the area of the inlet of the flow path. Based on the set value of the flow path and the density of nitrogen and the like, the pressure loss when nitrogen flows in the flow path was simulated using the theoretical formula of the Darcy-Weisbach pressure loss. Further, based on the pressure loss, the gas permeation rate C of the flow path was calculated. Furthermore, the total pressure P2 of the permeated gas in the housing was simulated from the pressure loss and the total pressure immediately before the pump and the like.

[0215] Further, the ratio of the selectivity (B+C) / (A+C) was calculated from the carbon dioxide gas permeation rate A, the nitrogen permeation rate B, and the gas permeation rate C. The total pressure ratio PI / P2 and (PI / P2) / (A / B) were calculated from the total pressure PI of the supplied gas and the total pressure P2 of the permeated gas.

[0216] When (PI / P2) / (A / B) > 1, it was considered that the gas permeation rate C had a dominant influence on the selectivity a of the separation device, and the selectivity a of the separation device was calculated based on (Formula 12). On the other hand, when 1 > (PI / P2) / (A / B), it was considered that the total pressure ratio PI / P2 had a dominant influence on the selectivity a of the separation device, and the total pressure ratio PI / P2 was taken as the selectivity a of the separation device. These results are shown in Table 1.

[0217] The structure of the separation device according to Example 2 was the same as that of the separation device according to Example 1 except that the lengths of the first pipe and the second pipe were lengthened. Therefore, the gas permeation rate C of Example 2 was lower than that of Example 1. Further, in Example 2, the set value of the total pressure immediately before the pump was set to a value smaller than that of Example 1.

[0218] The structure of the separation device according to Example 3 was the same as that of the separation device according to Example 2. Further, in Example 3, the carbon dioxide gas permeation rate A was set to a value larger than that of Example 2, the nitrogen permeation rate B was set to a value larger than that of Example 2, and the total pressure immediately before the pump was set to a value larger than that of Example 2.

[0219] As Figure 11In the separation device 900 related to Comparative Example 1, as shown, the first separation membrane 110 and the second separation membrane 210 are assumed to be fixed to one housing portion 930, and the piping 950 connecting the housing portion 930 and the pump 160 is not linear but has two bent portions 952, 953. In addition, the inner diameter of the piping 950 is set to a value smaller than the inner diameters of the respective pipings of Example 1. Therefore, the gas permeation rate C of Comparative Example 1 is lower than the gas permeation rates C of Examples 1 to 3. In addition, the carbon dioxide gas permeation rate A, the nitrogen gas permeation rate B, and the total pressure before the pump are set to the same values as those of Example 3.

[0220] The separation device related to Comparative Example 2 has the same structure as the separation device related to Comparative Example 1 except that the length of the piping 950 is shortened. Therefore, the gas permeation rate C of Comparative Example 2 is higher than that of Comparative Example 1. In addition, in Comparative Example 2, the carbon dioxide gas permeation rate A is set to a value smaller than that of Comparative Example 1, the nitrogen gas permeation rate B is set to a value smaller than that of Comparative Example 1, and the total pressure before the pump is set to a value smaller than that of Comparative Example 1.

[0221] The separation device related to Comparative Example 3 has the same structure as the separation device related to Example 1 except that the lengths of the first and second pipings are shortened and the inner diameters of the first, second, and fourth pipings are increased. Therefore, the gas permeation rate C of Comparative Example 3 is higher than those of Examples 1 to 3. In addition, in Comparative Example 3, the nitrogen gas permeation rate B is set to a value smaller than that of Example 1, and the total pressure before the pump is set to a value larger than that of Example 1.

[0222] Note that, as with Example 1, for Examples 2 and 3 and Comparative Examples 1 to 3, the selectivity A / B of the separation membranes, the ratio (B+C) / (A+C) of the selectivity, the total pressure P2 of the permeated gas, the total pressure ratio P1 / P2, (P1 / P2) / A / B, and the selectivity a of the separation device were calculated. In addition, for Examples 1 to 3 and Comparative Examples 1 to 3, the reduction rate of the selectivity a of the separation device with respect to the selectivity A / B of the separation membranes was calculated. Moreover, the separation devices were evaluated in accordance with the following evaluation criteria. The results are shown in Table 1.

[0223] S: The reduction rate of the selectivity is 20% or less

[0224] T: The reduction rate of the selectivity exceeds 20%

[0225] In the separation apparatuses of Embodiments 1, 2, and 3, (P1 / P2) / (A / B) ≥ 1 and 1 > (B+C) / (A+C) ≥ 0.8. The reduction rates of the selectivity in these cases were all 20% or less. Thus, it was found that the separation apparatuses of Embodiments 1, 2, and 3 had good selectivity α with respect to the selectivity A / B of the separation membrane. In particular, the reduction rate of the selectivity of Embodiment 1 was smaller than those of Embodiments 2 and 3. This is believed to be because the pressure loss of the flow path of Embodiment 1 was smaller than those of Embodiments 2 and 3.

[0226] In the separation apparatuses of Comparative Examples 1 and 2, (P1 / P2) / (A / B) ≥ 1, but 0.8 > (B+C) / (A+C). The reduction rates of the selectivity in these cases exceeded 20%. This is believed to be because, although the amount of pressure reduction by the pump was sufficient, the pressure loss of the flow path of Comparative Examples 1 and 2 was larger than those of Embodiments 1 to 3.

[0227] In addition, in the separation apparatus of Comparative Example 3, although 1 > (B+C) / (A+C) ≥ 0.8, 1 > (P1 / P2) / (A / B). The reduction rate of the selectivity in this case also exceeded 20%. This is believed to be because, although the pressure loss of the flow path could be reduced, the amount of pressure reduction by the pump was insufficient.

[0228] As described above, when it is desired to increase the selectivity α of the separation apparatus, it is important to satisfy both (P1 / P2) / (A / B) ≥ 1 and 1 > (B+C) / (A+C) ≥ 0.8. In addition, the present inventors and others additionally conducted experiments and confirmed the same tendencies as the simulation results. Furthermore, it was confirmed that the flow path having the gas permeation rate C of Table 1 could be achieved by using the aforementioned method of reducing the pressure loss of the flow path. Likewise, it was also confirmed that the total pressure ratio P1 / P2 of Table 1 could be achieved by adjusting the amount of pressure reduction by the pump.

[0229] The above describes the separation apparatus according to the present application based on the illustrated embodiments and the various modifications, but the present application is not limited thereto.

[0230] For example, the separation apparatus according to the present application can be one in which each part of the aforementioned embodiments and the various modifications is replaced with any structure having the same function, or one in which any structure is added to the aforementioned embodiments and the various modifications. The same applies to the design method of the separation apparatus according to the present application.

Claims

1. A separation device, characterized in that it is A separation apparatus for selectively separating carbon dioxide gas from a supply gas including carbon dioxide gas and nitrogen gas, the separation apparatus comprising: A separation membrane comprising a porous body and a resin layer disposed on the porous body, wherein the resin layer allows carbon dioxide gas included in the supply gas to selectively permeate into the porous body; The receiving section holds the separation membrane and forms a receiving space for receiving the permeated gas that passes through the separation membrane; Piping, connected to the receiving part; and The pump, via the piping, depressurizes the containment space and draws in the permeable gas. When the carbon dioxide gas permeation rate of the separation membrane is set as A, 500,000 GPUs ≥ A ≥ 1,000 GPUs When the nitrogen permeation rate of the separation membrane is set to B, the total pressure of the supplied gas is set to P1, and the total pressure of the permeated gas in the containment space is set to P2, (P1 / P2) / A / B≥1, The flow path between the separation membrane and the pump for the permeated gas includes the containment space and the internal space of the piping. When the gas permeability of the flow path is set to C, 1>(B+C) / (A+C)≥0.

8.

2. The separation device according to claim 1, wherein, 15≥(P1 / P2) / (A / B).

3. The separation device according to claim 1 or 2, wherein, It also has: Other separation membranes, comprising other porous bodies and other resin layers disposed on the other porous bodies, and allowing the carbon dioxide gas included in the supply gas to selectively permeate into the other porous bodies; Other containment sections, which hold the other separation membrane and form other containment spaces for containing other permeable gases that have passed through the other separation membrane; as well as Other piping, which is connected to the other receiving section. The pump depressurizes the other containment spaces via the other piping.

4. The separation device according to claim 1 or 2, wherein, In the flow path, the diameter of the inlet of the gas flowing from the containment section into the pipe gradually decreases from the upstream side to the downstream side.

5. The separation device according to claim 1 or 2, wherein, The flow path from the separation membrane is straight, wherein the flow path is a flow path that connects the receiving space of the receiving part and the internal space of the piping.

6. The separation device according to claim 1 or 2, wherein, The piping extends in a straight line.

7. The separation device according to claim 1 or 2, wherein, The porous material includes a porous layer supporting the resin layer. The porous layer has pores that extend through it in the thickness direction. The diameter of the pores increases continuously or in stages in the direction from the resin layer toward the porous layer.

8. The separation device according to claim 1 or 2, wherein, The porous material comprises multiple stacked porous layers. In each of the plurality of porous layers, a pore is formed that penetrates each of the plurality of porous layers in the thickness direction. The pores in the porous layer that are further away from the resin layer have larger diameters.

9. The separation device according to claim 1 or 2, wherein, The porous material comprises polymeric materials, ceramic materials, or metallic materials.

10. The separation device according to claim 1 or 2, wherein, The resin layer contains organopolysiloxane.

11. A design method for a separation device, characterized in that, This is a method for designing a separation device that selectively separates carbon dioxide gas from a supply gas including carbon dioxide gas and nitrogen gas. The method for designing the separation device comprises: The process of selecting a separation membrane, the separation membrane comprising a porous body and a resin layer, the resin layer being disposed on the porous body and enabling the carbon dioxide gas included in the supply gas to permeate through the porous body. as well as The process involves designing a containment unit, piping, and pump. The containment unit holds the separation membrane and forms a containment space for the permeate gas passing through the separation membrane. The piping is connected to the containment unit, and the pump depressurizes the containment space via the piping and draws in the permeate gas. The flow path between the separation membrane and the pump for the permeated gas includes the containment space and the internal space of the piping. In the selected process, When the carbon dioxide gas permeation rate of the separation membrane is set to A, the separation membrane with a value of 500,000 GPU ≥ A ≥ 1,000 GPU is selected. In the process of the design, When the nitrogen permeation rate of the separation membrane is set to B, the total pressure of the supplied gas is set to P1, and the total pressure of the permeated gas in the containment space is set to P2, a pump capable of depressurizing the containment space is selected such that (P1 / P2) / (A / B)≥1. When the gas permeability of the flow path is set to C, the flow path is designed such that 1 > (B+C) / (A+C) ≥ 0.

8.

12. The design method of the separation device according to claim 11, wherein, In the design process, the shape of the receiving space, the inner diameter of the piping, the length of the flow path, the surface roughness of the flow path, or the number of bends in the flow path are adjusted so that 1 > (B+C) / (A+C) ≥ 0.8.

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