Laminate of ion exchange membrane and gasket, ion dialysis tank, and gasket

Abstract

To provide a laminate of an ion exchange membrane and a gasket used for an ion dialysis tank, an ion dialysis tank having the laminate and a gasket used for the laminate that solve the problem of reduced efficiency as an ion dialysis tank.SOLUTION: Gaskets G1, G2 include: a processing portion G2a that forms a space for performing diffusion or dialysis in a diffusion dialysis tank and forms a space for performing ion exchange in an ion exchange dialysis tank: and a gasket frame surrounding the processing portion. A flow distribution portion G2c connecting the processing portion with communication holes Aa, Ka formed in the ion exchange membrane is formed in the gasket frame. A spacer 20 of a network structure is arranged in the processing portion, and a flow distribution plate 30 of a network structure is arranged in the flow distribution portion. An opening of the network structure of the flow distribution plate is formed smaller than an opening of the network structure of the spacer. A pitch in a liquid flowing direction in the flow distribution portion of the opening of the network structure of the flow distribution plate is longer than a pitch in a width direction orthogonal to the liquid flowing direction in the flow distribution portion.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a laminate of an ion exchange membrane and a gasket used in an ion dialysis cell which is an ion exchange dialysis cell or a diffusion dialysis cell, an ion dialysis cell including the laminate of an ion exchange membrane and a gasket, and a gasket used in the laminate. [Background technology]

[0002] Ion dialysis cells composed of a stack equipped with a laminate of ion exchange membranes and gaskets are known. The ion dialysis cells include at least an ion exchange dialysis cell that performs desalination, concentration, purification, recovery, etc. of ionic substances in a solution by electrodialysis using ion exchange membranes and the action of electricity, and a diffusion dialysis cell that recovers acids or alkalis from waste liquids by utilizing the concentration difference between the liquids on both sides of an ion exchange membrane without the action of electricity.

[0003] The desalination technology of electrolyte solutions by electrodialysis using ion exchange dialysis cells was first developed in the 1950s for the purpose of desalinizing brine. Since then, it has been used in a variety of fields, including concentrating seawater to produce table salt, desalinizing soy sauce and whey, streamlining various chemical manufacturing processes, wastewater treatment, and separating impurities from wine.

[0004] A typical electrodialysis device using the above-mentioned ion exchange dialysis tank has a stack of many ion exchange membranes (anion exchange membranes, cation exchange membranes) and gaskets stacked between a pair of electrodes, with the anion exchange membranes and cation exchange membranes alternately stacked between adjacent gaskets to form a stack. Each gasket is formed with a processing section that functions as an ion exchange chamber sandwiched between the anion exchange membrane and the cation exchange membrane and where ion exchange takes place, and a gasket frame surrounding the processing section, and the gasket frame is formed with a distribution section that connects the processing section to a communication hole formed in the ion exchange membrane (see, for example, Patent Document 1).

[0005] As ion exchange dialysis cells that enable electrodialysis, in addition to the above-mentioned configuration in which a stack is formed by laminating a large number of anion exchange membranes, cation exchange membranes, and gaskets to perform ion exchange, other known configurations include a configuration in which an ion exchange membrane (bipolar membrane) having a structure in which an anion exchange layer and a cation exchange layer are bonded together is combined with the above-mentioned anion exchange membrane, cation exchange membrane, and gasket to perform ion exchange, a configuration in which the bipolar membrane, anion exchange membrane, and gasket are combined and laminated to perform ion exchange, and a configuration in which the bipolar membrane, a cation exchange membrane, and gasket are combined and laminated to perform ion exchange, and a configuration in which the bipolar membrane, a cation exchange membrane, and gasket are combined and laminated to perform ion exchange.

[0006] In addition, when recovering an acid from a waste liquid using a diffusion dialysis tank, anion exchange membranes and gaskets are laminated to form a stack, and when recovering an alkali from a waste liquid, cation exchange membranes and gaskets are laminated to form a stack, and a chamber for supplying an acid or alkali waste liquid and water is formed in a treatment section having the same configuration as the gasket in the ion exchange dialysis tank described above, and by supplying the waste liquid or water to this treatment section, the acid or alkali contained in the waste liquid permeates the anion exchange membrane or cation exchange membrane and moves to the water side due to the concentration difference, and the acid or alkali is recovered (see, for example, Patent Document 2). The gasket used in this diffusion dialysis tank, like the gasket used in the ion exchange dialysis tank described above, is formed with a treatment section that functions as a chamber sandwiched between anion exchange membranes or cation exchange membranes to perform diffusion, and a gasket frame surrounding the treatment section, and the gasket frame is formed with a distribution section that connects the treatment section to a communication hole formed in the ion exchange membrane (anion exchange membrane or cation exchange membrane). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2014-14776 A [Patent Document 2] JP 2016-221507 A Summary of the Invention [Problem to be solved by the invention]

[0008] In any of the ion dialysis tanks described above, one or more stacks each having a laminate formed of an ion exchange membrane and a gasket are disposed, and the stack is held in place by applying a pressing force using a press machine that presses the stack from the side, while a space is formed by the treatment section and the distribution section of the gasket, through which the liquid to be treated flows, thereby carrying out ion exchange, diffusion, or dialysis.

[0009] In the treatment section and distribution section of the gasket sandwiched between the ion exchange membranes, sheet-like members are arranged to secure space for the liquid to be treated to flow and be processed. This sheet-like member is composed of a resin sheet with a mesh structure so that the raw liquid to be desalted, which is supplied to the treatment section, acid and alkaline waste liquid, etc., flow through the treatment section and distribution section.

[0010] Here, the thickness of the ion exchange membrane is generally thinner than that of the gasket, and when a stack is formed by laminating a plurality of ion exchange membranes and gaskets, and a pressing force is applied by a press machine to maintain the shape of the stack, and the raw liquid to be desalted, acid waste liquid, alkaline waste liquid, etc. are supplied to the above-mentioned treatment unit, the ion exchange membrane laminated on the gasket may fall toward the distribution unit formed in the gasket frame, and a gap may be generated on the side of the adjacent gasket facing each other across the ion exchange membrane in the distribution unit. As a result, the liquid flowing through the treatment unit of the adjacent gasket leaks out between the gasket frame and the ion exchange membrane of the adjacent gasket where no distribution unit is formed and no liquid normally flows (hereinafter referred to as "internal leakage"). In the ion exchange dialysis tank, liquids in independent circulation systems that would not normally mix (for example, concentrated liquid and desalted liquid) mix together, causing a problem of reduced efficiency as an ion dialysis tank.

[0011] Here, in order to prevent the ion exchange membrane from collapsing, it is conceivable to provide a plate-like member (a mesh-structured sheet) that is sufficiently thick and sturdy in the distribution section formed in the gasket frame. However, in that case, even if the internal leakage is suppressed, the pressure loss of the liquid flowing through the distribution section in which the plate-like member is provided increases, resulting in a problem of reduced efficiency as an ion dialysis cell. Furthermore, the increased pressure loss in the distribution section will cause liquid leakage at the side of the distribution section (the mating surface between the ion exchange membrane and the gasket frame). In the case of an electrodialysis cell, the electricity (stray current) flowing through the part where the liquid leakage occurs will burn and deteriorate the ion exchange membrane, resulting in irreversible damage.

[0012] The present invention has been made in view of the above-mentioned circumstances, and its main technical object is to provide a laminate of an ion exchange membrane and a gasket for use in an ion dialysis cell, which is an ion exchange dialysis cell or a diffusion dialysis cell, which can solve the problem that liquids in independent paths that would not normally mix (for example, a concentrated liquid and a desalted liquid) mix together due to sagging of the ion exchange membrane in the distribution section of the gasket frame, thereby reducing the efficiency of the ion dialysis cell, an ion dialysis cell including the laminate of an ion exchange membrane and a gasket, and a gasket for use in the laminate. [Means for solving the problem]

[0013] In order to solve the above-mentioned main technical problems, according to the present invention, there is provided a laminate of an ion exchange membrane and a gasket for use in an ion dialysis tank which is an ion exchange dialysis tank or a diffusion dialysis tank, the gasket comprising: a processing section which forms a space where ion exchange takes place in the ion exchange dialysis tank and a space which forms a space where diffusion or dialysis takes place in the diffusion dialysis tank; and a gasket frame surrounding the processing section, the gasket frame having a distribution section which connects the processing section with a through hole formed in the ion exchange membrane, a mesh-structured spacer is disposed in the processing section, a mesh-structured distribution plate is disposed in the distribution section, the openings of the mesh structure which constitutes the distribution plate are formed smaller than the openings of the mesh structure which constitutes the spacer, and the laminate of an ion exchange membrane and a gasket is formed so that the pitch of the openings of the mesh structure which constitutes the distribution plate in the liquid flow direction in the distribution section is longer than the pitch in the width direction perpendicular to the liquid flow direction in the distribution section.

[0014] It is preferable that the boundary between the processing section and the distribution section is an adjacent side, one end of the adjacent side is a starting point and an oblique side is formed at an angle with respect to the adjacent side of the strand constituting the mesh structure of the distribution plate, the end point of the oblique side reaching the side of the distribution plate and the other end of the adjacent side form an opposite side, the distribution plate is formed with dimensions that include a right triangle formed by the adjacent side, the oblique side, and the opposite side, and the angle formed by the adjacent side and the strand is set so that the right triangle does not overlap with the through holes of the ion exchange membrane. Also, it is preferable that the distribution plate has a woven structure.

[0015] According to the present invention, there is also provided an ion dialysis cell comprising the above-mentioned laminate of an ion exchange membrane and a gasket.

[0016] Furthermore, according to the present invention, there is provided a gasket to be laminated together with an ion exchange membrane in an ion dialysis tank which is an ion exchange dialysis tank or a diffusion dialysis tank, the gasket comprising: a processing section which forms a space in which ion exchange takes place in the ion exchange dialysis tank, and which forms a space in which diffusion or dialysis takes place in the diffusion dialysis tank; and a gasket frame surrounding the processing section, the gasket frame having a distribution section which connects the processing section with a through hole formed in the ion exchange membrane laminated to the gasket, a mesh-structured spacer is disposed in the processing section, a mesh-structured distribution plate is disposed in the distribution section, the openings of the mesh structure which constitutes the distribution plate are formed smaller than the openings of the mesh structure which constitutes the spacer, and the gasket is formed so that the pitch of the openings of the mesh structure which constitutes the distribution plate in the liquid flow direction in the distribution section is longer than the pitch in the width direction perpendicular to the liquid flow direction in the distribution section. Effect of the Invention

[0017] The laminate of an ion exchange membrane and a gasket of the present invention is a laminate of an ion exchange membrane and a gasket used in an ion dialysis tank which is an ion exchange dialysis tank or a diffusion dialysis tank, the gasket comprises a processing section which forms a space where ion exchange takes place in an ion exchange dialysis tank and a space where diffusion or dialysis takes place in a diffusion dialysis tank, and a gasket frame surrounding the processing section, the gasket frame is formed with a distribution section which connects the processing section with a communication hole formed in the ion exchange membrane, a mesh-structured spacer is disposed in the processing section, and a mesh-structured distribution plate is disposed in the distribution section, and the openings of the mesh structure constituting the distribution plate are spaced apart from the openings of the mesh structure constituting the spacer. Since the pitch of the openings of the mesh structure constituting the distribution plate in the liquid flow direction in the distribution section is also small, and the pitch of the openings in the mesh structure constituting the distribution plate in the liquid flow direction in the distribution section is longer than the pitch in the width direction perpendicular to the liquid flow direction in the distribution section, it is possible to reduce the wavy depressions formed along the distribution plate and reduce or eliminate the above-mentioned internal leakage, and since the pitch of the openings of the mesh structure constituting the distribution plate in the liquid flow direction in the distribution section is longer than the pitch in the width direction perpendicular to the liquid flow direction in the distribution section, it is possible to reduce the pressure loss in the distribution section and simultaneously solve the problems of internal leakage and increased pressure loss.

[0018] Furthermore, the ion dialysis cell of the present invention is provided with the above-mentioned laminate of ion exchange membranes and gaskets, thereby making it possible to reduce the wavy depressions formed along the distribution plate and to reduce or eliminate the above-mentioned internal leakage. At the same time, the pitch of the openings of the mesh structure constituting the distribution plate in the liquid flow direction in the distribution section is longer than the pitch in the width direction perpendicular to the liquid flow direction in the distribution section, thereby making it possible to reduce pressure loss in the distribution section and simultaneously solve the problems of internal leakage and increased pressure loss.

[0019] Furthermore, the gasket of the present invention comprises a processing section which forms a space in an ion exchange dialysis cell where ion exchange takes place, and which forms a space in a diffusion dialysis cell where diffusion or dialysis takes place, and a gasket frame surrounding the processing section, and the gasket frame is formed with a distribution section which connects the processing section with a through hole formed in the ion exchange membrane laminated to the gasket, a mesh-structured spacer is disposed in the processing section, and a mesh-structured distribution plate is disposed in the distribution section, the openings of the mesh structure which constitutes the distribution plate are formed smaller than the openings of the mesh structure which constitutes the spacer, and the openings of the mesh structure which constitutes the distribution plate are formed larger ... Since the pitch in the liquid flow direction in the distribution section is longer than the pitch in the width direction perpendicular to the liquid flow direction in the distribution section, the wavy depressions formed along the distribution plate can be made smaller, and the above-mentioned internal leakage can be reduced or eliminated.Furthermore, since the pitch in the liquid flow direction of the openings of the mesh structure that constitutes the distribution plate in the distribution section is longer than the pitch in the width direction perpendicular to the liquid flow direction in the distribution section, the pressure loss in the distribution section can be reduced, and the above-mentioned problems of internal leakage and increased pressure loss can be simultaneously solved. [Brief description of the drawings]

[0020] [Figure 1] FIG. 2 is a schematic side view of an ion exchange dialysis cell constituting the electrodialysis apparatus of the present embodiment. [Diagram 2] FIG. 2 is an exploded perspective view including a gasket, an anion exchange membrane, a gasket, and a cation exchange membrane which constitute a unit constituting the ion exchange dialysis tank shown in FIG. 1, as well as a gasket laminated on the cation exchange membrane. [Diagram 3] 3(a) is an enlarged front view of the region of the gasket shown in FIG. 2 in which a flow distribution portion is formed, and FIG. 3(b) is a further enlarged front view of a portion of the front view shown in (a). [Figure 4] FIG. 2(a) is a conceptual diagram showing the flow of liquid and the state of internal leakage when electrodialysis is performed using the ion exchange dialysis tank shown in FIG. 1, (b) is a cross-sectional view taken along line AA in (a), and (c) is a cross-sectional view taken along line BB in (a). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, a laminate of an ion exchange membrane and a gasket used in an ion dialysis cell constructed according to the present invention, an ion dialysis cell equipped with the laminate of the ion exchange membrane and the gasket, and an embodiment of a gasket used in the laminate will be described in detail with reference to the attached drawings. Note that the ion dialysis cell described below is an example of an ion exchange dialysis cell that performs desalting and concentration of ionic substances in a solution by the action of an ion exchange membrane and electricity, but the present invention is not limited thereto, and can also be applied to a diffusion dialysis cell that recovers an acid or alkali from a waste liquid by utilizing the concentration difference between the liquids on both sides of an ion exchange membrane, without relying on the action of electricity.

[0022] FIG. 1 is a schematic side view of an ion exchange dialysis cell 1 constituting the electrodialysis device of this embodiment, and for convenience of explanation, the ion exchange dialysis cell 1 is shown exploded. The ion exchange dialysis cell 1 shown in the figure constitutes a so-called filter press type electrodialysis device. This ion exchange dialysis cell 1 is formed by stacking a plurality of laminates of ion exchange membranes and gaskets between an anode chamber 10a including an anode plate and a cathode chamber 10b including a cathode plate. More specifically, as shown in the figure, a large number of gaskets G1 and G2 are arranged in layers, and cation exchange membranes K and anion exchange membranes A, which are ion exchange membranes, are alternately arranged between these gaskets. As such cation exchange membranes K and anion exchange membranes A, well-known ones are used. As shown in the figure, the gasket G1, anion exchange membrane A, gasket G2, and cation exchange membrane K surrounded by dashed lines are formed as one unit U, and a plurality of units U (for example, 60 units) are stacked to form one stack S. Electrode diaphragms N1 and N2 made of ion exchange membranes are disposed between the anode chamber 10a and the cathode chamber 10b at both ends of the stack S. The stack S is sandwiched between a pair of clamping plates 12 and 14 shown in Fig. 1, and is held in place by applying a horizontal pressing force by a press device (not shown). Note that Fig. 1 is a side view showing an outline of the ion exchange dialysis tank 1, and does not show the entire configuration. Configurations other than those shown, including flow paths through which the raw solution, concentrated solution, and desalted solution flow, pumps, and the like, are omitted as appropriate.

[0023] FIG. 2 shows a perspective view of the gasket G1 laminated on the cation exchange membrane K in addition to the gasket G1, anion exchange membrane A, gasket G2, and cation exchange membrane K constituting the unit U of the ion exchange dialysis tank 1 described above. The gasket G1 sandwiched between the electrode diaphragm N1 made of the ion exchange membrane and the anion exchange membrane A includes a processing section G1a where ion exchange is performed and a gasket frame G1b surrounding the processing section G1a. The gasket frame G1b has four upper and lower flow distribution sections G1c connecting the communication holes of the ion exchange membrane laminated on the gasket G1, more specifically, the communication holes Ab of the anion exchange membrane A, and the processing section G1a. In addition, the gasket frame G1b also has four upper and lower communication holes G1d that are independent of the processing section G1a and communicate with the communication holes Aa of the anion exchange membrane A laminated on the gasket G1.

[0024] The gasket G2 is laminated on the gasket G1 through the anion exchange membrane A and sandwiched between the anion exchange membrane A and the cation exchange membrane K. The gasket G2 includes a processing section G2a that forms a space (demineralization chamber) for producing a desalted liquid from a raw liquid by ion exchange, and a gasket frame G2b that surrounds the processing section G2a. The gasket frame G2b has four distribution sections G2c formed on the top and bottom that connect the communication holes Aa of the anion exchange membrane A that sandwiches the gasket G2 and the communication holes Ka formed in the cation exchange membrane K, and the processing section G2a. The gasket frame G2b also has four communication holes G2d formed on the top and bottom that are independent of the processing section G2a and connect the communication holes Ab formed in the anion exchange membrane A that sandwiches the gasket G2 and the communication holes Kb formed in the cation exchange membrane K. The gasket G2 is laminated on the gasket G1 similar to the above through the cation exchange membrane K. The gasket G1 is further laminated with an anion exchange membrane A (not shown) similar to that described above. In this manner, the ion exchange dialysis tank 1 of this embodiment is formed by laminating a plurality of units U each including the gasket G1, the anion exchange membrane A, the gasket G2, and the cation exchange membrane K. The processing portion G1a of the gasket G1 sandwiched between the cation exchange membrane K and the anion exchange membrane A forms a space (concentration chamber) in which a concentrated liquid is produced by ion exchange.

[0025] As shown in FIG. 2, a mesh-structured spacer 20 is disposed in the processing portion G1a of the gasket G1 and the processing portion G2a of the gasket G2, and a mesh-structured distribution plate 30 is disposed in the flow distribution portion G1c of the gasket G1 and the flow distribution portion G2c of the gasket G2.

[0026] Fig. 3(a) shows an enlarged view of the area where the flow distribution section G2c is formed in the front view of the gasket G2. As can be seen from Fig. 2 and Fig. 3(a), the spacer 20 is formed over the entire area of ​​the processing section G2a, and a single mesh-structured sheet is used in which strands of molten plastic resin, such as polyolefins such as polyethylene and polypropylene, are formed into threads and then woven into a biaxial fabric structure. By disposing this spacer 20, it is possible to form a desalting compartment in the processing section G2a without contacting the anion exchange membrane A and the cation exchange membrane K that face each other.

[0027] 3(a), the flow distribution plate 30 is formed with a size corresponding to the width dimension of the flow distribution section G2c indicated by the arrow X1-X2, and with a size extending from the boundary between the processing section G2a and the flow distribution section G2c to the through holes Aa of the anion exchange membrane A and the through holes Ka (indicated by the dashed line) of the cation exchange membrane K sandwiching the gasket G2, and is inserted between the anion exchange membrane A and the cation exchange membrane K sandwiching the flow distribution section G2c of the gasket G2 to secure a space for flowing liquid in the flow direction indicated by the arrow Y1-Y2. Like the spacer 20, the flow distribution plate 30 is formed from a sheet of a mesh structure in which strands of molten plastic resin, such as polyolefins such as polyethylene and polypropylene, formed into threads are not woven but are woven into a biaxial fabric structure.

[0028] Here, the electrodialysis apparatus is of a commercially practical size, that is, the area of ​​the treatment section G2a (effective current passing area) is 50 to 14,000 cm 2 , more preferably 55 to 6,000 cm 2 In the case of the above, the width of the distribution section G2c indicated by the arrow X1-X2 is generally 0.5 to 10 cm, preferably 0.8 to 5 cm. The length of the distribution section G2c (the length from the boundary between the treatment section G2a and the distribution section G2c to the communication hole Ka indicated by the dashed line) is generally 1.5 to 5.5 cm, preferably 1.7 to 5.0 cm.

[0029] The thickness of the spacer 20 and the flow distribution plate 30 is set corresponding to the thickness of the gasket, and the thickness of the spacer 20 and the flow distribution plate 30 is determined by the thickness of two strands when the spacer 20 and the flow distribution plate 30 are formed in a woven structure, so that typically, the strands forming the mesh structure of the spacer 20 arranged in the gaskets G1 and G2 of this embodiment and the strands forming the mesh structure of the flow distribution plate 30 have the same thickness. Here, the wire diameter of the strands forming the mesh structures of the spacer 20 and the flow distribution plate 30 is generally 0.25 to 0.50 mm, and more preferably 0.28 to 0.45 mm.

[0030] As shown in Fig. 3(a), the openings of the mesh structure constituting the distribution plate 30 of this embodiment are formed smaller than the openings of the mesh structure constituting the spacer 20. Furthermore, the openings of the mesh structure constituting the distribution plate 30 are formed so that the pitch in the liquid flow direction of the distribution section G2c indicated by the arrow Y1-Y2 is longer than the pitch in the width direction indicated by the arrow X1-X2 perpendicular to the liquid flow direction. This point will be described in more detail with reference to Fig. 3(b) in addition to Fig. 3(a).

[0031] FIG. 3(b) shows an enlarged view of the area of ​​the dashed line R in the distribution plate 30 shown in FIG. 3(a). In FIG. 3(b), the direction indicated by the arrow Y1-Y2 is the flow direction of the liquid in the distribution section G2c, and the direction indicated by the arrow X1-X2 is the width direction of the distribution section G2c. As shown in FIG. 3(b), the distribution plate 30 is a sheet having a woven structure formed by welding strands 31, 31 inclined to the left in the figure and strands 32, 32 inclined to the right in the figure. Openings P1'P2'P3'P4' are formed by points P1', P2', P3', P4' inside the quadrangle P1P2P3P4 formed by the intersection points P1, P2, P3, P4 of the strands 31 and 32. In this embodiment, the openings P1'P2'P3'P4' shown in the figure are formed so that the pitch P1'P3' (=a) in the liquid flow direction indicated by the arrow Y1-Y2 is longer than the pitch P2'P4' (=b) in the width direction indicated by the arrow X1-X2 perpendicular to the liquid flow direction. The effects of forming them in this way will be described later.

[0032] The size of the openings formed by the flow distribution plate 30 can generally be explained by the ratio (opening ratio) of the area of ​​the openings P1'P2'P3'P4' to the area of ​​the quadrangle P1P2P3P4 formed by the intersection of the strands 31, 31 and the strands 32, 32 shown in Fig. 3(b). In this embodiment, the spacer 20 is also formed with a mesh structure, and the opening ratio of the spacer 20 is calculated in the same manner as described above. A suitable value for this opening ratio will be described later.

[0033] The flow of liquid when desalting and concentrating ionic substances in a solution using the above-mentioned ion exchange dialysis tank 1 will be described with reference to FIG.

[0034] Fig. 4(a) shows a region corresponding to the flow distribution portion G2c of the gasket G2 described based on Fig. 3(a), and the gasket G2 is sandwiched and laminated between anion exchange membrane A and cation exchange membrane K, and as shown in Fig. 4(b) and (c), gasket G1 is laminated on the anion exchange membrane A side and gasket G1 is laminated on the cation exchange membrane K side. Fig. 4(b) is a cross-sectional view taken along line AA in Fig. 4(a), and Fig. 4(c) is a cross-sectional view taken along line BB in Fig. 4(a).

[0035] The arrow F1 shown in FIG. 4(a) indicates the flow of the desalted liquid from the processing section G2a of the gasket G2 through the distribution section G2c toward the region where the through holes Aa of the anion exchange membrane A and the through holes Ka of the cation exchange membrane K are formed when electrodialysis is performed in the ion exchange dialysis tank 1 described above, and this flow F1 of the desalted liquid indicates the flow through the distribution section G2c shown in FIG. 4(b) and (c). In this embodiment, as can be understood from FIG. 4(b) and (c), in the region corresponding to the distribution section G2c of the anion exchange membrane A laminated on the gasket G2, the anion exchange membrane A is sunk in a wavy shape along the strand 31 of the distribution plate 30. As a result, a gap M is generated between the gasket G1 in contact with the anion exchange membrane A and the anion exchange membrane A. For convenience of explanation, the sagging of the anion exchange membrane A shown in FIG. 4(b) and (c) is depicted as being sunk larger than it actually is.

[0036] In the gasket frame G1b of the gasket G1, no distribution portion is formed in the region corresponding to the distribution portion G2c of the gasket G2, and if there is no sag, no liquid will flow from the processing portion G1a of the gasket G1 to the through holes Aa of the anion exchange membrane A and the through holes Ka of the cation exchange membrane K. However, as described above, if the anion exchange membrane A sags in the region corresponding to the distribution portion G2c and a gap M is generated, as shown by the arrow F2 in FIG. 4(a), the liquid in the processing portion G1a (not shown) of the gasket G1 flows into the above-mentioned gap M, causing internal leakage W. If the internal leakage W reaches the region corresponding to the through holes Aa of the anion exchange membrane A and the through holes Ka of the cation exchange membrane K, it will mix with the desalted liquid flowing from the processing portion G2a of the gasket G2 via the distribution portion G2c, causing a problem of reduced processing efficiency as the ion exchange dialysis tank 1.

[0037] Here, in this embodiment, as described above, the openings P1'P2'P3'P4' of the mesh structure constituting the distribution plate 30 disposed in the distribution section G2c are formed smaller than the openings of the mesh structure constituting the spacer 20. As a result, compared to a case in which the openings P1'P2'P3'P4' of the mesh structure of the distribution plate 30 are made to have a mesh structure of the same size as the openings of the mesh structure of the spacer 20, it is possible to reduce the wavy depressions formed along the strands 31 of the distribution plate 30, and it is possible to reduce or eliminate the above-mentioned internal leakage W.

[0038] Here, if the openings P1'P2'P3'P4' of the mesh structure constituting the distribution plate 30 are made small, the strands 31 and 32 of the distribution plate 30 will act as resistance, increasing the pressure loss in the distribution section G2c and raising concerns about liquid leakage to the sides of the distribution section G2c. Therefore, in this embodiment, as described above, the pitch a of the openings P1'P2'P3'P4' of the mesh structure constituting the distribution plate 30 in the liquid flow direction (the direction of the arrow Y1-Y2) in the distribution section G2c is formed to be longer than the pitch b in the width direction X1-X2 perpendicular to the liquid flow direction Y1-Y2 in the distribution section G2c. Since the flow F1 in the distribution section G2c flows along the strands 31 and 32, the pitch a in the liquid flow direction (the direction of the arrow Y1-Y2) of the openings P1'P2'P3'P4' in the distribution section G2c is longer than the pitch b in the width direction X1-X2 perpendicular to the liquid flow direction Y1-Y2 in the distribution section G2c. This makes the flow F1 in the distribution section G2c smoother than when the pitch a is shorter than the pitch b, and reduces the pressure loss in the distribution section G2c. Therefore, by adopting the laminate of the ion exchange membrane and the gasket disclosed in this embodiment, the ion dialysis tank including the laminate of the ion exchange membrane and the gasket, and the gasket, it is possible to simultaneously solve the problems of the internal leakage W and the increased pressure loss.

[0039] Furthermore, in the distribution plate 30, the boundary line between the processed portion G2a and the distribution portion G2c of the gasket G2 (the line connecting points Q1 and Q2 in Figure 4(a)) is the adjacent side Q1Q2, and a hypotenuse Q2Q3 is formed with one end Q2 of the adjacent side Q1Q2 as the starting point and an angle θ with respect to the adjacent side Q1Q2 of the strands 31 that constitute the mesh structure of the distribution plate 30, and the opposite side Q3Q1 is formed by the end point Q3 of the hypotenuse Q2Q3 reaching the opposite side of the distribution plate 30 and the other end Q1 of the adjacent side Q1Q2. The flow distribution plate 30 is formed with dimensions that include the right-angled triangle Q1Q2Q3 formed by the adjacent side Q1Q2, the hypotenuse Q2Q3, and the opposite side Q3Q1, and the angle θ formed by the adjacent side Q1Q2 and the strand is set so that the right-angled triangle Q1Q2Q3 does not overlap the communicating hole Aa of the anion exchange membrane A and the communicating hole ka of the cation exchange membrane K that are laminated to the gasket G2.

[0040] Here, if the anion exchange membrane A falls into the distribution portion G2c between the gasket G1 and the anion exchange membrane A in the region corresponding to the distribution portion G2c, and a gap M occurs, as shown in FIG. 4(b) showing the AA cross section of FIG. 4(a), an internal leakage W may occur from the processing portion G1a of the gasket G1 in the region near the boundary line (the line connecting points Q1 and Q2 in FIG. 4(a)). However, even if such an internal leakage W occurs, in this embodiment, the right triangle Q1Q2Q3 formed in the distribution plate 30 is set so as not to overlap with the communication holes Aa and Ka, so that the internal leakage W flowing through the gap M along the angle θ of the strand 31 forming the distribution plate 30 can be contained within the right triangle Q1Q2Q3, and as shown in FIG. 4(c) showing the BB cross section of FIG. 4(a), the internal leakage W does not occur in the gap M and does not reach the communication holes Aa and Ka.

[0041] That is, as described above, in addition to the effect obtained by forming the openings P1'P2'P3'P4' of the mesh structure constituting the distribution plate 30 smaller than the openings of the mesh structure constituting the spacer 20 and by forming the pitch a of the openings of the mesh structure constituting the distribution plate 30 in the liquid flow direction Y1-Y2 in the distribution section G2c to be longer than the pitch b of the openings in the width direction X1-X2 perpendicular to the liquid flow direction Y1-Y2 in the distribution section G2c, it becomes possible to more reliably prevent internal leakage W.

[0042] As described above, the openings P1'P2'P3'P4' in the mesh structure of the distribution plate 30 are preferably small to suppress the sagging of the ion exchange membrane. However, if the aperture ratio of the distribution plate 30 is too small, the pressure loss in the distribution section tends to increase. In particular, if the ratio of the aperture ratio of the distribution plate 30 to the aperture ratio of the spacer 20 is less than 0.50, the sagging of the ion exchange membrane can be suppressed, but the pressure loss increases excessively, which is not preferable. Therefore, the ratio of the aperture ratio of the distribution plate 30 to the aperture ratio of the spacer 20 is preferably 0.50 to 0.99, more preferably 0.65 to 0.99, even more preferably 0.65 to 0.90, and most preferably 0.70 to 0.80. This suppresses the sagging of the ion exchange membrane toward the distribution plate 30 and suppresses the excessive increase in pressure loss in the distribution section.

[0043] The opening ratio of the flow distribution plate 30 is typically selected from the range of 40 to 80%, more preferably 50 to 60%, and it is preferable that the value in this range satisfies the requirement of the ratio of the opening ratio of the flow distribution plate 30 to the opening ratio of the spacer 20.

[0044] Furthermore, as described above, the pitch a of the openings P1'P2'P3'P4' in the liquid flow direction (the direction of the arrow Y1-Y2) in the distribution section G2c is preferably formed to be longer than the pitch b in the width direction X1-X2 perpendicular to the liquid flow direction Y1-Y2 in the distribution section G2c. If the pitch a is shorter than the pitch b, the smoothness of the flow F1 in the distribution section G2c is impaired, and the pressure loss in the distribution section G2c is increased, which is not preferable. Therefore, the pitch a is preferably 1.1 times or more longer than the pitch b, more preferably 1.1 to 2.2 times, more preferably 1.3 to 2.2 times, and particularly preferably 1.5 to 2.2 times. In addition, the pitch a is generally 0.25 to 0.50 mm, more preferably 0.28 to 0.45 mm, when the wire diameter of the strand formed as the network structure is the general one.

[0045] It is further preferable that the distribution plate 30 is formed with dimensions included within the right triangle Q1Q2Q3 formed by the adjacent side Q1Q2, the hypotenuse Q2Q3, and the opposite side Q3Q1, as described above, and if this is to be achieved in a manner that satisfies the requirements for the preferred opening ratio and the length of the pitch a relative to the pitch b, the angle θ of the hypotenuse Q2Q3 with respect to the adjacent side Q1Q2 of the strand 31 is generally selected to be 45 to 70°, and more preferably 50 to 65°.

[0046] The present invention is not limited to the above-mentioned embodiment, and may include various modified examples. In the above-mentioned embodiment, an example was shown in which the laminate of the ion exchange membrane and the gasket constructed based on the present invention was applied to an ion exchange dialysis tank capable of electrodialysis, but for example, it is also possible to apply it to a configuration in which an ion exchange membrane (bipolar membrane) having a structure in which an anion exchange layer and a cation exchange layer are bonded together, the above-mentioned anion exchange membrane, the cation exchange membrane, and the gasket are combined and laminated to form a stack to perform ion exchange, a configuration in which the bipolar membrane, the anion exchange membrane, and the gasket are combined and laminated to form a stack to perform ion exchange, a configuration in which the bipolar membrane, the cation exchange membrane, and the gasket are combined and laminated to form a stack to perform ion exchange, and further, an ion exchange membrane and a gasket are laminated to form a stack to perform diffusion dialysis.

[0047] In the above embodiment, the ion exchange membranes (anion exchange membrane A, cation exchange membrane K) have a total of four communicating holes (Aa, Ab, Ka, Kb) formed on the top and bottom, but the present invention is not limited to this, and other numbers may be used, and the size may be set as necessary. In the above embodiment, the communicating holes Aa, Ab, Ka, Kb of the anion exchange membrane A and the cation exchange membrane K are substantially rectangular, but the present invention is not limited to this, and they may be round. Even if the communicating holes Aa and Ka are round, the present invention can achieve the same effects as the above embodiment. [Explanation of symbols]

[0048] 1: Ion exchange dialysis tank 10a:Anode chamber 10b: Cathode chamber 12, 14: Clamping plate 20: Spacer 30: Distribution plate 31, 32: Strand A: Anion exchange membrane K: Cation exchange membrane G1, G2, G3~Gn: Gaskets G1a: Processing section G1b: Gasket frame G1c: Distribution section G1d: Communication hole G2a: Processing section G2b: Gasket frame G2c: Distribution section G2d: Communication hole N1, N2: Electrode diaphragm

Claims

1. A laminate of an ion exchange membrane and a gasket for use in an ion dialysis cell which is an ion exchange dialysis cell or a diffusion dialysis cell, comprising: The gasket comprises a treatment section which forms a space where ion exchange is performed in an ion exchange dialysis tank and a space where diffusion or dialysis is performed in a diffusion dialysis tank, and a gasket frame which surrounds the treatment section; a flow distribution section that connects the processing section and a communication hole formed in the ion exchange membrane is formed in the gasket frame; A spacer having a mesh structure is disposed in the processing section, and a flow plate having a mesh structure is disposed in the flow distribution section, A laminate of an ion exchange membrane and a gasket, in which the openings of the mesh structure constituting the distribution plate are formed smaller than the openings of the mesh structure constituting the spacer, and the pitch of the openings of the mesh structure constituting the distribution plate in the liquid flow direction in the distribution section is longer than the pitch in the width direction perpendicular to the liquid flow direction in the distribution section.

2. 2. A gasket laminate as described in claim 1, wherein the boundary line between the processing section and the distribution section is an adjacent side, one end of the adjacent side is the starting point and an oblique side is formed at an angle with respect to the adjacent side of the strands that constitute the mesh structure of the distribution plate, and an opposite side is formed by the end point of the oblique side reaching the side of the distribution plate and the other end of the adjacent side, and the distribution plate is formed with dimensions that include a right triangle formed by the adjacent side, the oblique side, and the opposite side, and the angle formed by the adjacent side and the strands is set so that the right triangle does not overlap with the communicating holes of the ion exchange membrane.

3. 2. The ion exchange membrane and gasket laminate according to claim 1, wherein the flow plate has a woven structure.

4. An ion dialysis cell comprising a laminate of the ion exchange membrane and gasket according to claim 1.

5. A gasket laminated together with an ion exchange membrane in an ion dialysis cell which is an ion exchange dialysis cell or a diffusion dialysis cell, The gasket comprises a treatment section which forms a space where ion exchange is performed in an ion exchange dialysis tank and a space where diffusion or dialysis is performed in a diffusion dialysis tank, and a gasket frame which surrounds the treatment section; a flow distribution section that connects the processing section and a communication hole formed in the ion exchange membrane laminated on the gasket is formed in the gasket frame; A spacer having a mesh structure is disposed in the processing section, and a flow plate having a mesh structure is disposed in the flow distribution section, A gasket in which the openings of the mesh structure constituting the distribution plate are formed smaller than the openings of the mesh structure constituting the spacer, and the pitch of the openings of the mesh structure constituting the distribution plate in the liquid flow direction in the distribution section is longer than the pitch in the width direction perpendicular to the liquid flow direction in the distribution section.

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