Permeable membrane elements and permeable membrane modules

Abstract

In the forward osmosis membrane element 3, the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 are wrapped around the main channel 30 such that the direction from the adhesive edge (311A, 312A, 313A) toward the bent portion (311C, 312C, 313C) is the winding direction. The adhesive edge (311A, 312A, 313A), which is a part of the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 that is prone to breakage, is pressed against the main channel 30 and compressed by the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313. Inside each membrane leaf, a first channel 33 partitioned by a first spacer 32 is formed. The second spacer 34 is positioned in a second channel 35 formed in the gap between adjacent first membrane leaf 311 and second membrane leaf 312, or in a second channel 35 formed in the gap between adjacent second membrane leaf 312 and third membrane leaf 313.

Description

Technical Field

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[0001] The present invention relates to a permeable membrane element and a permeable membrane module. More specifically, it relates to a permeable membrane element and a permeable membrane module capable of realizing the forward osmosis phenomenon and the reverse osmosis phenomenon.

Background Art

[0002] In recent years, various global environmental problems such as the consumption of fossil fuels, the depletion of resources, and the increase in greenhouse gas emissions associated with the economic development of the world have become apparent. Under such circumstances, as means of energy production, new decarbonized energy technologies such as solar power generation, wind power generation, and geothermal power generation have been developed.

[0003] Among decarbonized energy technologies, recently, osmotic pressure power generation in which waters with different solute concentrations such as seawater and rivers are brought into contact through a permeable membrane has attracted attention. Specifically, in osmotic pressure power generation, a "forward osmosis phenomenon" occurs in which water permeates through a permeable membrane from a fresh water channel to a seawater channel, and efficient power generation is realized by rotating a prime mover such as a turbine using the energy of the force by which the water moves.

[0004] Therefore, in osmotic pressure power generation, it is necessary to efficiently generate the forward osmosis phenomenon and increase the amount of water that moves, and thus the development of a forward osmosis membrane module for this purpose has been carried out. Therefore, in recent years, as a forward osmosis membrane module with higher permeation ability, a membrane leaf type forward osmosis membrane module in which a forward osmosis membrane element having membrane leaves is installed in a case to increase the permeation ability per unit area has been developed.

[0005] As a forward osmosis membrane element used in such a forward osmosis membrane module, for example, Patent Document 1 describes a forward osmosis membrane element 500 shown in FIG. 7. The forward osmosis membrane element 500 includes a main pipe 501 and a plurality of membrane leaves 504 wound along the outer periphery of the main pipe 501.

[0006] Furthermore, the main pipeline 501 is formed in a cylindrical shape, and an inlet 502 is formed at one end of the main pipeline 501. Furthermore, an outflow hole 503 is formed on the side of the main pipeline 501, which communicates with a second channel 510 formed between the stacked membrane leaves 504.

[0007] Furthermore, the membrane leaf 504 is formed in the shape of a single sheet and is bent in such a way that it sandwiches the first spacer 507. Furthermore, by bonding and sealing the folded and overlapping edges of the membrane leaf 504, a first opening 505 is formed at one end and a second opening 506 at the other end, and a first channel 508 is formed inside, partitioned by a first spacer 507 made of resin material.

[0008] Furthermore, the second spacer 509 is bonded to the side surface of the main conduit 501, and a membrane leaf 504 is laminated on its surface, with the edges of the first opening 505 and the second opening 506 of the membrane leaf 504 being bonded to the second spacer 509. Subsequently, the second spacers 509 and membrane leaves 504 are stacked alternately, and the edges of the first opening 505 and the second opening 506 of the membrane leaves 504 are bonded to the second spacers 509.

[0009] Furthermore, for example, Patent Document 2 describes a forward osmosis membrane element 602 as shown in Figure 8. The forward osmosis membrane element 602 of Patent Document 2 comprises a membrane leaf 623, a central tube 603 around which the membrane leaf 623 is wound, and a plurality of partitions (631, 632) provided inside the central tube 603. Through holes 638 are formed in the partitions 631, except for the terminal partition 632. In Figure 8, the arrows indicate the flow of liquid. The membrane leaf 623 is provided with multiple internal channels 626 arranged in parallel, which are bent from the first opening 626A toward the second opening 626B.

[0010] Furthermore, an inlet 633 is formed at one end of the central pipe 603 and an outlet 634 at the other end. The central pipe 603 also has a supply hole 635 that communicates with the first opening 626A and a recovery hole 636 that communicates with the second opening 626B. Furthermore, the terminal partition wall 632, which is closest to the outlet 634, blocks the inside of the central pipe 603, and through holes 638 are formed in the partition walls 631 other than the terminal partition wall. In other words, a partition 627 is provided inside the bag-shaped membrane leaf 623, causing water to circulate within the membrane leaf 623 via the partition 627, creating a water flow that returns to the outlet of the same central tube 603 from the inlet. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] International Publication No. 2023 / 176647 [Patent Document 2] Japanese Patent Publication No. 2014-23985 [Overview of the project] [Problems that the invention aims to solve]

[0012] However, in the forward osmosis membrane elements described in Patent Documents 1 and 2, the membrane leaf is not wrapped around the main conduit in such a way that the direction from the bonded edge towards the bent portion is the winding direction. Therefore, the bonded edge is not pressed against the main conduit and is not compressed. Furthermore, since each membrane leaf is offset from the others and wrapped around the main conduit, the bonded edges of the inner membrane leaves do not overlap with the outer membrane leaves and are therefore not pressed or compressed by the outer membrane leaves. Therefore, when liquid is supplied to the inside of the membrane leaf and the membrane leaf expands, there is a possibility that the bonded edges may rupture, making it impossible to efficiently permeate the water.

[0013] Furthermore, Patent Document 1 does not specifically describe actively providing a cavity adjacent to the bonded edge. Since the area of ​​the membrane leaf that expands when liquid is supplied is adjacent to the bonded edge, when liquid is supplied to the membrane leaf and the membrane leaf expands, the force due to the expansion is easily transmitted to the bonded edge. If the bonded edge is not compressed, there is a possibility that the bonded edge may break, and it may not be possible to efficiently penetrate water.

[0014] Furthermore, in the forward osmosis membrane element described in Patent Document 2, the partition within the membrane leaf generates water flow to the central tube, which reduces the smoothness of the water flow and causes stagnation within the membrane leaf. As a result, the permeability of the membrane leaf decreases in these stagnant areas (such as the triangular area in Figure 8), and consequently, the overall permeability of the forward osmosis membrane element decreases, potentially preventing efficient water permeation.

[0015] This invention was conceived in view of the above points, and aims to provide a permeable membrane element and a permeable membrane module that can efficiently permeate water. [Means for solving the problem]

[0016] To achieve the above objective, the permeable membrane element of the present invention comprises a plurality of membrane leaves in which the overlapping edges opposite to the bent portion of a folded sheet are bonded together, and a first channel is formed inside through which a predetermined first liquid is supplied; and a main channel in which the membrane leaves are wound so that the direction from the bonded edge of the membrane leaves toward the bent portion is the winding direction, and a second liquid having a different solute concentration from the first liquid is supplied in an axial direction parallel to the first channel, and an outflow hole is formed on the side for the second liquid to flow out, wherein a second channel is formed in the gap between adjacent membrane leaves, with one side communicating with the outflow hole and the other side open, and a cavity is provided in the membrane leaf adjacent to the bonded edge of the membrane leaf.

[0017] In the present invention, the "hollow portion" means a location where no member exists. Also, in the main pipe, the membrane leaf is wound around the main pipe such that the direction from the adhesion edge portion, which is the edge portion to which the membrane leaf is adhered, to the bending portion becomes the winding direction. As a result, the adhesion edge portion, which is a portion of the membrane leaf that is likely to break, is pressed against the main pipe by the membrane leaf and compressed. Therefore, it becomes difficult for the adhesion edge portion to break, and it is possible to prevent the liquid that has entered the membrane leaf from leaking from the adhesion edge portion.

[0018] In addition, since a hollow portion is provided in the membrane leaf adjacent to the adhesion edge portion of the membrane leaf, the hollow portion is more easily compressed than the adhesion edge portion. Therefore, unlike a configuration in which no hollow portion is provided, the portion of the membrane leaf that expands when liquid is supplied can be separated from the adhesion edge portion without being adjacent to the adhesion edge portion, and it becomes difficult for the expanding force to be directly transmitted to the adhesion edge portion, making it difficult for the adhesion edge portion to break.

[0019] Moreover, since a hollow portion is provided in the membrane leaf, the hollow portion is easily compressed. Therefore, it is easier to closely attach the adhesion edge portion together with the hollow portion to the main pipe than in a configuration where no hollow portion is provided.

[0020] Also, when liquid is supplied to the membrane leaf, the pressure in the portion of the membrane leaf that is compressed and difficult for liquid to enter, that is, the "adhesion edge portion and the hollow portion", is lower than the pressure in the portion that is difficult to compress and where liquid enters, that is, the portion other than the "adhesion edge portion and the hollow portion". Therefore, due to this pressure difference, the portion other than the "adhesion edge portion and the hollow portion" presses the "adhesion edge portion and the hollow portion" against the main pipe, further compressing the "adhesion edge portion and the hollow portion". As a result, it becomes even more difficult for the adhesion edge portion to break.

[0021] In the permeable membrane element of the present invention, the position of the adhesion edge portion of the outer membrane leaf can be configured to be shifted in the direction opposite to the winding direction from the position of the adhesion edge portion of the inner membrane leaf.

[0022] In this case, the cross-sectional shape of the plurality of membrane leaves wound around the main pipe is unlikely to be elliptical and can be made substantially circular, so it is easy to accommodate the permeable membrane element in the module case. Also, since each of the adhesion edges of the plurality of membrane leaves can be directly pressed against the main pipe that is harder than the membrane leaves without passing through other membrane leaves, it is easier to further compress the adhesion edges.

[0023] Further, in the permeable membrane element of the present invention, the total length of the adhesion edge and the cavity of the outer membrane leaf in the direction connecting the bent portion and the adhesion edge of the membrane leaf is longer than the total length of the adhesion edge and the cavity of the inner membrane leaf.

[0024] In this case, when winding the outer membrane leaf, even if the length around the main pipe becomes longer by the thickness of the inner membrane leaf, the length of the portion to be compressed can be ensured.

[0025] Further, in the permeable membrane element of the present invention, the ratio of the length of the adhesion edge and the length of the cavity of the membrane leaf in the direction connecting the bent portion and the adhesion edge of the membrane leaf can be configured to be 9:1 to 5:5.

[0026] If the length of the cavity becomes longer than the length of the adhesion edge, the cavity is pressed against the main pipe more strongly than the adhesion edge, and the pressing of the adhesion edge against the main pipe tends to be insufficient. However, when the length of the cavity is the same as or shorter than the length of the adhesion edge, the cavity is not pressed against the main pipe more strongly than the adhesion edge, and both "sufficient pressing of the adhesion edge against the main pipe" and "isolation between the portion where the membrane leaf expands when liquid is supplied and the adhesion edge" can be achieved in a balanced manner.

[0027] Further, in the permeable membrane element of the present invention, a flat plate-shaped first spacer with a mesh formed, which is arranged at a distance corresponding to the length of the cavity from the adhesion edge inside the membrane leaf, and a flat plate-shaped second spacer with a mesh formed, which is arranged between adjacent membrane leaves forming the second flow path, can be provided.

[0028] In this case, the first spacer creates a predetermined space within the membrane leaf, preventing obstruction of the flow of the first liquid through the first channel. This makes it easier for a greater pressure difference to occur between the pressure in the less compressible area where the liquid enters and the pressure in the compressed area where the liquid enters. As a result, the area where the liquid enters further compresses the area where the liquid enters, making the adhesive edge less likely to break. Furthermore, the first spacer creates a predetermined space within the membrane leaf, preventing obstruction of the flow of the first liquid through the first channel, thus allowing the flow rate in the first channel to be kept constant.

[0029] Furthermore, the second spacer increases the shear stress near the membrane leaf in the second channel of the second liquid, promoting the penetration of the second liquid from the second channel to the first channel. As a result, both the first liquid and the second liquid flow into the first channel, and the areas where the liquid enters further compress areas where it is difficult for the liquid to enter, making the adhesive edge less likely to break. Furthermore, the second spacer ensures a gap between adjacent membrane leaves, which acts as a second channel. This prevents obstruction of the flow of the second liquid within the second channel, thus maintaining a constant flow rate within the second channel.

[0030] Furthermore, in order to achieve the above objectives, the permeable membrane module of the present invention comprises a case having a first supply pipe and a second supply pipe positioned at a predetermined location on one end of a cylindrical main body, a first discharge pipe positioned at a predetermined location on the side of the main body, and a second discharge pipe positioned at a predetermined location on the other end of the main body, and a permeable membrane element housed in the case, wherein the permeable membrane element is a folded sheet-like material, with the overlapping edges opposite to the folded portion being bonded together, and a predetermined first liquid flows from a first opening communicating with the first supply pipe toward a second opening communicating with the second discharge pipe. The permeable membrane element comprises a plurality of membrane leaves with a first supply channel formed inside, and a main channel in which the membrane leaves are wound so that the direction from the bonded edge of the membrane leaf toward the bending point is the winding direction, and a second liquid having a different solute concentration from the first liquid is supplied in an axial direction parallel to the first channel, and an outflow hole is formed on the side for the second liquid to flow out, wherein the permeable membrane element has a second channel formed in the gap between adjacent membrane leaves, one side of which communicates with the outflow hole and the other side which is open, and a cavity is provided in the membrane leaf adjacent to the bonded edge of the membrane leaf.

[0031] Here, the membrane leaf is wrapped around the main conduit such that the direction from the bonded edge of the membrane leaf towards the bending point is the wrapping direction. As a result, the bonded edge, which is a part of the membrane leaf that is prone to breaking, is pressed against the main conduit and compressed by the membrane leaf, making the bonded edge less likely to break and preventing the liquid contained in the membrane leaf from leaking out from the bonded edge.

[0032] Furthermore, because a cavity is provided in the membrane leaf adjacent to the adhesive edge of the membrane leaf, the cavity is more easily compressed than the adhesive edge. Unlike configurations without a cavity, the area of ​​the membrane leaf that is supplied with liquid and expands can be kept away from the adhesive edge, making the adhesive edge less likely to break.

[0033] Furthermore, because the membrane leaf has a cavity, the cavity is easily compressed, making it easier to tightly adhere the adhesive edge to the main pipe along with the cavity compared to a configuration without a cavity.

[0034] Furthermore, when liquid is supplied to the membrane leaf, the pressure in the areas of the membrane leaf that are not easily compressed and into which liquid can enter (i.e., areas other than the "adhesive edge and cavity") becomes greater than the pressure in the areas of the membrane leaf that are compressed and into which liquid is difficult to enter (i.e., the "adhesive edge and cavity"). This pressure difference causes the areas other than the "adhesive edge and cavity" to press the "adhesive edge and cavity" against the main pipe, further compressing the "adhesive edge and cavity" area, and as a result, the adhesive edge becomes even less likely to break. [Effects of the Invention]

[0035] The permeable membrane element according to the present invention can efficiently permeate water. The permeable membrane module according to the present invention can efficiently permeate water. [Brief explanation of the drawing]

[0036] [Figure 1] This is a schematic diagram showing an example of a membrane leaf provided by a forward osmosis membrane element to which the present invention is applied. [Figure 2] This is an exploded schematic diagram showing an example of a forward osmosis membrane element to which the present invention is applied. [Figure 3] This is a schematic diagram showing an example of a forward osmosis membrane element to which the present invention is applied, with the membrane leaf wrapped around the main conduit. [Figure 4] This is a schematic diagram showing an example of the internal structure of a forward osmosis membrane module to which the present invention is applied. [Figure 5] Figure (a) shows the permeation rate for a forward osmosis membrane module to which the present invention is applied, and Figure (b) shows the membrane output for a forward osmosis membrane module to which the present invention is applied. [Figure 6] This is a block diagram of an osmotic power generation system based on a permeable membrane module to which the present invention is applied. [Figure 7]This is an exploded schematic diagram showing a conventional forward osmosis membrane element. [Figure 8] This is a schematic cross-sectional view of a conventional center-seal type forward osmosis membrane element. [Modes for carrying out the invention]

[0037] Hereinafter, embodiments of the present invention will be described with reference to the drawings to facilitate understanding of the present invention. Figure 1 is a schematic diagram showing an example of a membrane leaf in a forward osmosis membrane element to which the present invention is applied. Figure 2 is an exploded schematic diagram showing an example of a forward osmosis membrane element to which the present invention is applied. Figure 3 is a schematic diagram showing an example of a forward osmosis membrane element to which the present invention is applied, with the membrane leaf wrapped around the main conduit. Figure 4 is a schematic diagram showing an example of the internal structure of a forward osmosis membrane module to which the present invention is applied.

[0038] Here, we will explain the forward osmosis phenomenon using the permeable membrane element and permeable membrane module of the present invention. Therefore, the permeable membrane element of the present invention will be referred to as the "forward osmosis membrane element," and the permeable membrane module of the present invention will be referred to as the "forward osmosis membrane module."

[0039] As shown in Figure 1, the membrane leaf 31 of the forward permeability membrane element 3 of the present invention is constructed by folding a sheet-like material and bonding the overlapping edges on the opposite side of the folded portion 31C. Here, the bonded edge is the bonded edge 31A.

[0040] Furthermore, as shown in Figure 1, a first channel 33 is formed inside the membrane leaf 31, which is created by folding a sheet-like material, allowing a predetermined first liquid to be supplied and flow through it.

[0041] The membrane leaf 31 is composed of materials that can realize both forward osmosis and reverse osmosis. A single sheet-like material constituting the membrane leaf 31 has a three-layer structure in which a base layer made of a nonwoven fabric material such as polypropylene, a support layer made of a porous material such as polysulfone, and an active layer made of polyamide are laminated in this order.

[0042] Here, the single sheet-like material constituting the membrane leaf 31 can also be a two-layer structure in which, for example, a support layer and an active layer are integrated to form a single layer, and a base layer is combined with this. Furthermore, the materials for the base layer, support layer, and active layer can be appropriately selected from known materials, as long as the membrane leaf 31 is capable of causing forward osmosis or reverse osmosis.

[0043] Furthermore, as shown in Figure 1, a flat first spacer 32 is positioned inside the membrane leaf 31 at a predetermined distance from the adhesive edge 31A, thereby creating a cavity 31B between the adhesive edge 31A and the first spacer 32 where no material exists. In other words, a cavity 31B is provided adjacent to the adhesive edge 31A.

[0044] Furthermore, the first spacer 32 is made of resin material and has a mesh structure. The resin material constituting the first spacer 32 is specifically a thermoplastic resin material such as polypropylene, high-density polyethylene, nylon, polybutylene terephthalate, polyphenylene sulfide, or ethylene vinyl acetate, but it can of course be appropriately selected from known materials.

[0045] Such a sheet-like material is folded so that the active layer faces inward and the first spacer 32 is sandwiched between the folded sheets, and the overlapping edges are bonded together to seal it. In this way, a membrane leaf 31 is obtained in which a first opening 38 is formed at one end and a second opening 39 is formed at the other end opposite to the first end, and a first channel 33 partitioned by a first spacer 32 is formed inside.

[0046] Furthermore, the ratio of the length X of the adhesive edge 31A to the length Y of the cavity 31B of the membrane leaf 31 in the direction connecting the bent portion 31C of the membrane leaf 31 and the adhesive edge 31A is 9:1 to 5:5.

[0047] Furthermore, as shown in Figure 2, the forward osmosis membrane element 3 of the present invention is equipped with a main conduit 30, and a plurality of membrane leaves, namely a first membrane leaf 311, a second membrane leaf 312, and a third membrane leaf 313, are wrapped around the main conduit 30.

[0048] Specifically, as shown in Figure 2, for example, the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 are stacked with a flat plate-shaped second spacer 34. At this time, as shown in Figure 2, the adhesive edges 31A are on the same side and offset from each other, and the first membrane leaf 311, the second membrane leaf 312, the third membrane leaf 313 and the second spacer 34 are stacked on top of each other.

[0049] Then, the edges of the first opening 38 and the edges of the second opening 39 of the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 are bonded to the second spacer 34 to obtain a laminate. Furthermore, the parts other than the edges of the first opening 38 and the edges of the second opening 39 are not bonded to the second spacer 34.

[0050] The laminate obtained in this way is placed on another second spacer 34 such that the third membrane leaf 313 is in contact with another second spacer 34. Then, as shown in Figure 2, on another second spacer 34, the main conduit 30 is rotated in the direction of the arrow from the adhesive edge 31A side of the laminate, and the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 are wrapped around the main conduit 30.

[0051] In this way, the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 are each wrapped around the main conduit 30 such that the direction from the adhesive edge (311A, 312A, 313A) towards the bent portion (311C, 312C, 313C) is the wrapping direction. As a result, the adhesive edges (311A, 312A, 313A), which are the most prone to rupture among the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313, are pressed against the main pipe 30 and compressed by the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313. This makes the adhesive edges (311A, 312A, 313A) less prone to rupture, and prevents the liquid that has entered the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 from leaking from the adhesive edges (311A, 312A, 313A).

[0052] In addition, cavities (311B, 312B, 313B) are provided adjacent to the adhesive edges (311A, 312A, 313A) of the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313, and the cavities (311B, 312B, 313B) are more easily compressed than the adhesive edges (311A, 312A, 313A). Therefore, the first flow channels 33 of the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313, which are supplied with liquid and expand, can be kept away from the adhesive edges (311A, 312A, 313A) without being adjacent to them. This makes it difficult for the expanding force to be directly transmitted to the adhesive edges (311A, 312A, 313A), making it difficult for the adhesive edges (311A, 312A, 313A) to break, and preventing the liquid from leaking from the adhesive edges (311A, 312A, 313A).

[0053] Furthermore, when liquid is supplied to the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313, the pressure at the locations where liquid can enter but is not easily compressed, i.e., the first flow channels 33 of each of the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313, becomes greater than the pressure at the locations where liquid cannot easily enter due to compression, i.e., the "adhesive edges (311A, 312A, 313A) and cavities (311B, 312B, 313B)". Consequently, this pressure difference causes the first flow channels 33 of the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 to press the "adhesive edges (311A, 312A, 313A) and cavities (311B, 312B, 313B)" against the main channel 30, further compressing the "adhesive edges (311A, 312A, 313A) and cavities (311B, 312B, 313B)," and as a result, the adhesive edges (311A, 312A, 313A) become even less likely to break.

[0054] In this case, the first membrane leaf 311 constitutes the inner layer, the second membrane leaf 312 constitutes the intermediate layer, and the third membrane leaf 313 constitutes the outer layer. Furthermore, since the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 are stacked with the second spacer 34, offset from each other, the position of the adhesive edge 312A of the second membrane leaf 312, which constitutes the intermediate layer, is shifted in the opposite direction to the winding direction compared to the position of the adhesive edge 311A ​​of the first membrane leaf 311, which constitutes the inner layer. Furthermore, the position of the adhesive edge 313A of the third membrane leaf 313 constituting the outer layer is shifted in the opposite direction to the winding direction compared to the position of the adhesive edge 312A of the second membrane leaf 312 constituting the intermediate layer.

[0055] Here, the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 are the same size, but the total length of the adhesive edge portions (311A, 312A, 313A) and the void portions (311B, 312B, 313B) in the direction connecting the bent portion (311C, 312C, 313C) and the adhesive edge portion (311A, 312A, 313A) of the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 are different from each other. In other words, the total length of the adhesive edge 312A and cavity 312B of the second membrane leaf 312, which constitutes the intermediate layer, is longer than the total length of the adhesive edge 311A ​​and cavity 311B of the first membrane leaf 311, which constitutes the inner layer. Furthermore, the total length of the adhesive edge portion 313A and the cavity portion 313B of the third membrane leaf 313, which constitutes the outer layer, is longer than the total length of the adhesive edge portion 312A and the cavity portion 312B of the second membrane leaf 312, which constitutes the intermediate layer.

[0056] Furthermore, the ratio of the length X of the adhesive edge 311A ​​of the first membrane leaf 311 to the length Y of the cavity 311B, the ratio of the length X of the adhesive edge 312A of the second membrane leaf 312 to the length Y of the cavity 312B, and the ratio of the length X of the adhesive edge 313A of the third membrane leaf 313 to the length Y of the cavity 313B are all 5:5.

[0057] To make the structure within the membrane leaf easier to understand, the thickness of the membrane leaf is exaggerated and shown as larger in Figures 1 and 2 compared to the diameter of the main conduit.

[0058] Furthermore, the second spacer 34 is made of resin material and has a mesh structure. The resin material constituting the second spacer 34 is, specifically, polyester, but it can of course be appropriately selected from known materials with a certain strength and low water absorption.

[0059] Furthermore, a second channel 35 is formed in the gap between the adjacent first membrane leaf 311 and the second membrane leaf 312. Furthermore, a second channel 35 is also formed in the gap between the adjacent second membrane leaf 312 and the third membrane leaf 313.

[0060] Furthermore, as shown in Figure 3, the main pipeline 30 is formed in a cylindrical shape, with an inlet 301 formed at one end. The inlet 301 is an opening into which a second liquid, having a different solute concentration from the first liquid, is supplied to the interior of the main pipeline 30.

[0061] Furthermore, multiple outlet holes 302 for discharging the second liquid are formed in parallel along the axial direction of the main pipeline 30 on the side surface of the main pipeline 30. Furthermore, one side of the second channel 35 is in communication with the outflow hole 302, while the other side is open. Furthermore, a group of outlet holes 302 formed in parallel in the axial direction of the main pipeline 30 are arranged in a total of four rows at approximately 90° intervals in the circumferential direction of the side surface of the main pipeline 30. Here, it goes without saying that it is possible to form five or more rows of outlet holes 302, which are arranged in parallel in the axial direction of the main pipeline 30.

[0062] Furthermore, as shown in Figure 2, the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 are stacked with the flat second spacer 34. Therefore, the second spacer 34 is positioned in the gaps between adjacent first membrane leaves 311 and second membrane leaves 312, and in the gaps between adjacent second membrane leaves 312 and third membrane leaves 313.

[0063] Furthermore, as shown in Figure 4, the forward osmosis membrane module 1 of the present invention comprises a case 2 and a forward osmosis membrane element 3 of the present invention housed inside the case 2.

[0064] Case 2 has a cylindrical main body 20 made of, for example, FRP (fiber-reinforced plastic). Furthermore, a first supply pipe 21 for supplying the first liquid, saltwater W1, into the main body 20 is provided at a position offset from approximately the center of one end of the main body 20. Furthermore, a second supply pipe 22 is provided at approximately the center of one end of the main body 20. The second supply pipe 22 is in communication with the main pipeline 30 inside the main body 20 and is for supplying the second liquid, fresh water W2, to the main pipeline 30.

[0065] Furthermore, a first discharge pipe 23 is provided at approximately the center of the side surface of the main body 20 for discharging the liquid inside the main body 20 in a direction approximately perpendicular to the axial direction. Furthermore, a second discharge pipe 24 is provided at a position approximately offset from the center on the other end of the main body 20 for discharging the liquid inside the main body 20.

[0066] Furthermore, both ends of the forward osmosis membrane element 3 of the present invention are supported by support members 36 within the case 2. Furthermore, a sealing material 37, such as a packing or O-ring, is placed in the gap between the support member 36 and the inner wall of the case 2.

[0067] Furthermore, as shown in Figures 3 and 4, the support member 36 has multiple through holes 36A, allowing liquid to pass through the through holes 36A. Furthermore, the first openings 38 of the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 are in communication with the through-holes 36A of the support member 36 that supports one end of the forward osmosis membrane element 3 of the present invention. Furthermore, the second openings 39 of the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 are in communication with the through-holes 36A of the support member 36 that supports the other end of the forward osmosis membrane element 3 of the present invention.

[0068] Furthermore, within case 2, compartments A, B, and C are formed independently of each other by the forward osmosis membrane element 3 and support member 36 of the present invention. That is, as shown in Figure 4, the compartment A is formed between one end of the main body 20 and the support member 36 that supports one end of the forward osmosis membrane element 3 of the present invention. Furthermore, compartment B is formed around the forward osmosis membrane element 3 of the present invention, between the side surface of the main body 20 and the forward osmosis membrane element 3 and the support member 36. Furthermore, the compartment C is formed between the other end of the main body 20 and the support member 36 that supports the other end of the forward osmosis membrane element 3 of the present invention.

[0069] Furthermore, the first supply pipe 21, located at one end of the main body 20, is in communication with compartment A. Furthermore, the first discharge pipe 23, located approximately at the center of the axially extending portion of the main body 20, is in communication with the compartment B. Furthermore, the second discharge pipe 24, located at the other end of the main body 20, is in communication with the compartment C.

[0070] Furthermore, since the edges of the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 on the first opening 38 side are bonded to the second spacer 34 without any gaps, the compartment A communicates with the first channel 33 of the forward osmosis membrane element 3 of the present invention via the through hole 36A of the support member 36, but does not communicate with the second channel 35.

[0071] Furthermore, since the other side of the second channel 35 is open, the second channel 35 is in communication with the outflow hole 302 of the main pipeline 30 and also with compartment B.

[0072] Furthermore, since the edges of the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 on the second opening 39 side are also bonded to the second spacer 34 without any gaps, the compartment C communicates with the first channel 33 of the forward osmosis membrane element 3 of the present invention via the through hole 36A of the support member 36, but does not communicate with the second channel 35.

[0073] Furthermore, Figure 4 schematically shows the flow of liquid within the forward osmosis membrane element 3 of the present invention. As shown in Figure 4, saltwater W1 is supplied to compartment A through the first supply pipe 21, and freshwater W2 is supplied to the main pipeline 30 through the second supply pipe 22.

[0074] The saltwater W1 supplied to compartment A passes through the through-hole 36A of the support member 36 and flows through the first channel 33, from the first opening 38 to the second opening 39 of the membrane leaf 31, through the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313.

[0075] Meanwhile, the freshwater W2 supplied to the main pipeline 30 flows out through the outlet hole 302 into the second channel 35. The freshwater W2 that flows into the second channel 35 comes into contact with the membrane reef 31, and due to the forward osmosis phenomenon caused by the concentration difference between the saltwater W1 flowing in the first channel 33 and the freshwater W2 flowing in the second channel 35, the freshwater W2 in the second channel 35 flows into the first channel 33.

[0076] The freshwater W2 that flows into the first channel 33 mixes with the saltwater W1 flowing through the first channel 33 to form an increased volume of mixed water W3. The mixed water W3 flows out from the second opening 39 of the membrane leaf 31 through the through hole 36A of the support member 36 into the compartment C, and is discharged from the case 2 through the second discharge pipe 24 which is in communication with the compartment C.

[0077] Meanwhile, any uninfiltrated freshwater W4 flowing through the second channel 35 that could not enter the first channel 33 flows out into compartment B, which is connected to the second channel 35, and is discharged from case 2 through the first discharge pipe 23, which is connected to compartment B.

[0078] [Other embodiments] An example has been described in which saltwater W1 is supplied to compartment A through the first supply pipe 21 and freshwater W2 is supplied to the main pipeline 30 through the second supply pipe 22. However, it is also possible to supply freshwater W2 to compartment A through the first supply pipe 21 and saltwater W1 to the main pipeline 30 through the second supply pipe 22.

[0079] In this case, the freshwater W2 supplied to compartment A passes through the through-hole 36A of the support member 36 and flows through the first flow path 33, from the first opening 38 of the membrane leaf 31 to the second opening 39, through the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313.

[0080] Meanwhile, the saltwater W1 supplied to the main pipeline 30 flows out through the outlet hole 302 into the second channel 35. Then, the saltwater W1 that flows out into the second channel 35 comes into contact with the membrane leaf 31, and due to the forward osmosis phenomenon caused by the concentration difference between the freshwater W2 flowing in the first channel 33 and the saltwater W1 flowing in the second channel 35, the freshwater W2 in the first channel 33 flows into the second channel 35.

[0081] The freshwater W2 that flows into the second channel 35 mixes with the saltwater W1 flowing through the second channel 35 to form an increased volume of mixed water W3. The mixed water W3 flows out into compartment B, which is connected to the second flow path 35, and is discharged from case 2 through the first discharge pipe 23, which is connected to compartment B.

[0082] Meanwhile, any unpermeated water W4 in the freshwater W2 flowing through the first channel 33 that could not flow into the second channel 35 flows out through the second opening 39 of the membrane leaf 31 and the through-hole 36A of the support member 36 into the compartment C, and is discharged from the case 2 through the second discharge pipe 24 which is in communication with the compartment C.

[0083] In the forward permeability membrane element 3 of the present invention, the total length of the adhesive edge portion 311A ​​and the cavity portion 311B of the first membrane leaf 311 constituting the inner layer, the total length of the adhesive edge portion 312A and the cavity portion 312B of the second membrane leaf 312 constituting the intermediate layer, and the total length of the adhesive edge portion 313A and the cavity portion 313B of the third membrane leaf 313 constituting the outer layer can be approximately the same length.

[0084] However, on the other hand, by making the total length of the adhesive edge 312A and cavity 312B of the second membrane leaf 312 constituting the intermediate layer longer than the total length of the adhesive edge 311A ​​and cavity 311B of the first membrane leaf 311 constituting the inner layer, and by making the total length of the adhesive edge 313A and cavity 313B of the third membrane leaf 313 constituting the outer layer longer than the total length of the adhesive edge 312A and cavity 312B of the second membrane leaf 312 constituting the intermediate layer, when wrapping the outer membrane leaf, even if the length around the main conduit is increased by the thickness of the inner membrane leaf, the length of the compressed area can be secured.

[0085] Furthermore, in the forward osmosis membrane element 3 of the present invention, the ratio of the length X of the adhesive edge portion 311A ​​of the first membrane leaf 311 to the length Y of the cavity portion 311B, the ratio of the length X of the adhesive edge portion 312A of the second membrane leaf 312 to the length Y of the cavity portion 312B, and the ratio of the length X of the adhesive edge portion 313A of the third membrane leaf 313 to the length Y of the cavity portion 313B can be made different from each other, and the length X of the adhesive edge portions (311A, 312A, 313A) can be made shorter than the length Y of the cavity portions (311B, 312B, 313B). For example, the ratio of the length X of the adhesive edge (311A, 312A, 313A) to the length Y of the cavity (311B, 312B, 313B) can be 4:6 to 1:9.

[0086] However, if the length Y of the cavity (311B, 312B, 313B) is the same as or shorter than the length X of the adhesive edge (311A, 312A, 313A), the cavity (311B, 312B, 313B) will not be pressed more strongly against the main conduit 30 than the adhesive edge (311A, 312A, 313A), thus achieving a good balance between "sufficient pressure of the adhesive edge against the main conduit" and "isolation between the area of ​​the membrane leaf that is supplied with liquid and expands and the adhesive edge."

[0087] Furthermore, the forward osmosis membrane element 3 of the present invention can also be configured without the first spacer 32 and the second spacer 34.

[0088] However, on the other hand, because the forward osmosis membrane element 3 of the present invention is equipped with a first spacer 32, a predetermined space is formed within the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313, preventing obstruction of the flow of the first liquid through the first channel 33. As a result, a pressure difference is more likely to occur between the pressure in the area where liquid enters and is not easily compressed, and the pressure in the area where liquid enters and is compressed and is not easily compressed. Consequently, the area where liquid enters further compresses the area where liquid enters and is not easily compressed, making the adhesive edges (311A, 312A, 313A) less likely to break.

[0089] Furthermore, because the forward osmosis membrane element 3 of the present invention is equipped with a first spacer 32, a predetermined space is formed within the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313, preventing obstruction of the flow of the first liquid through the first channel 33, and thus the flow rate in the first channel 33 can be kept constant.

[0090] Furthermore, since the forward osmosis membrane element 3 of the present invention is equipped with a second spacer 34, the penetration of the second liquid from the second channel 35 to the first channel 33 can be promoted. As a result, the second liquid flows in the first channel 33 in addition to the first liquid, and the areas where the liquid enters further compress areas where the liquid does not easily enter, making the adhesive edge less likely to break.

[0091] Furthermore, because the forward osmosis membrane element 3 of the present invention is equipped with a second spacer 34, it is possible to secure gaps that serve as second flow channels 35 formed between adjacent first membrane leaves 311 and second membrane leaves 312, and between adjacent second membrane leaves 312 and third membrane leaves 313. As a result, the flow of the second liquid in the second flow channel 35 is not obstructed, and the flow rate in the second flow channel 35 can be kept constant.

[0092] To evaluate the pressure resistance of the forward osmosis membrane element of the present invention, the following negative pressure test and water flow test were performed.

[0093] [Negative pressure test] A membrane leaf 31, as shown in Figure 1, was wrapped around the main conduit 30 such that the winding direction was from the adhesive edge 31A towards the bent portion 31C, thereby fabricating a forward osmosis membrane element with one layer of membrane leaf 31. At this time, the total length of the adhesive edge 31A and the cavity 31B in the direction connecting the bent portion 31C and the adhesive edge 31A is approximately the same as the length of one full circumference of the main pipe 30. Furthermore, the ratio of the length X of the adhesive edge portion 31A to the length Y of the cavity portion 31B is 5:5.

[0094] In other words, all outflow holes 302 formed in the main pipeline 30 were closed by the portion of the membrane leaf 31 corresponding to the adhesive edge 31A and the cavity 31B.

[0095] Then, the fabricated forward osmosis membrane element was housed in case 2 as shown in Figure 4, and a forward osmosis membrane module 1 as shown in Figure 4 was constructed.

[0096] Next, a vacuum pump was connected to the second supply pipe 22 provided at one end of the main body 20, and the main pipeline 30, which is connected to the second supply pipe 22, was evacuated using the vacuum pump. The vacuum pump was stopped when the vacuum level reached -40kPa.

[0097] We then confirmed that a vacuum of -40kPa could be maintained for 30 seconds.

[0098] [Water flow test] A forward osmosis membrane element similar to the one fabricated in the negative pressure test was manufactured. Furthermore, we fabricated a forward osmosis membrane module similar to the one used in the negative pressure test.

[0099] Next, saltwater W1 was supplied to compartment A through the first supply pipe 21 provided on one end of the main body 20. At this time, the saltwater W1 was pressurized so that its pressure was approximately 1.5 MPa. Furthermore, freshwater W2 was supplied to the main pipeline 30 through a second supply pipe 22 provided on one end of the main body 20. At this time, the freshwater W2 was pressurized so that its pressure was approximately 0.2 MPa. In other words, since the salinity of the freshwater W2 flowing through the main pipe 30 is easier to measure than the saline water W1 flowing through the first channel 33, the pressure of the saline water W1 is made higher than the pressure of the freshwater W2 to cause a "forward osmosis phenomenon" in which the saline water W1 flows into the main pipe 30.

[0100] Then, the salinity of the freshwater W2 flowing through the main pipeline 30 was measured to confirm that the salinity had not increased.

[0101] The negative pressure test and water flow test described above confirmed that the adhesive edge portion 31A and the cavity portion 31B of the membrane leaf 31 of the forward osmosis membrane element of the present invention are in sufficient contact with the main pipeline 30 and adequately block the outflow hole 302 of the main pipeline 30.

[0102] Furthermore, negative pressure tests and water flow tests were conducted by changing the ratio of the length X of the adhesive edge portion 31A and the length Y of the cavity portion 31B of the membrane leaf 31.

[0103] In this negative pressure test, a vacuum of -40kPa was maintained for 30 seconds if it was successful, and unsuccessful if it was not. Furthermore, in the water flow test, the salinity of the freshwater W2 flowing through the main pipe 30 was measured, and if the salinity did not increase, it was judged as "pass." However, for membrane leaves 31 that had a ratio judged as "fail" in the negative pressure test, it was clear that the salinity would increase, so a water flow test was not performed. The results, including the case where the ratio of the length X of the adhesive edge portion 31A to the length Y of the cavity portion 31B is 5:5, are shown in Table 1.

[0104] [Table 1]

[0105] As can be seen from Table 1, the negative pressure test and water flow test were judged as "passed" when the length X of the adhesive edge 31A was longer than the length Y of the cavity 31B, or when the length X of the adhesive edge 31A and the length Y of the cavity 31B were the same. On the other hand, even if the length X of the adhesive edge 31A is longer than the length Y of the cavity 31B, if the cavity 31B is not provided, or if the length X of the adhesive edge 31A is shorter than the length Y of the cavity 31B, the negative pressure test was judged as "failure."

[0106] [Measurement of permeability and membrane output] Two forward osmosis membrane elements 3 of the present invention were fabricated, each comprising a first membrane leaf 311, a second membrane leaf 312, and a third membrane leaf 313, which are wrapped around the main pipeline 30.

[0107] Then, each of the two fabricated forward osmosis membrane elements 3 of the present invention was housed in a case 2 as shown in Figure 4, and two forward osmosis membrane modules 1 of the present invention, as shown in Figure 4, were manufactured.

[0108] Next, saltwater W1 was supplied to compartment A through the first supply pipe 21 provided on one end of the main body 20. At this time, the saltwater W1 was pressurized so that its pressure was approximately 1.5 MPa. Furthermore, the salinity of salt solution W1 was 3.5%, and the flow rate of salt solution W1 was 230 mL / min.

[0109] Furthermore, freshwater W2 was supplied to the main pipeline 30 through a second supply pipe 22 provided on one end of the main body 20. At this time, the freshwater W2 was pressurized so that its pressure was approximately 0.3 MPa. Furthermore, the flow rate of freshwater W2 was 100 mL / min. In other words, a "forward insulation phenomenon" occurred, causing saltwater W1 to flow into the main pipeline 30.

[0110] Then, the amount of infiltration was calculated based on the difference between the amount of saltwater W1 supplied to the first supply pipe 21 and the amount of saltwater W1 discharged from case 2 through the second discharge pipe 24. Figure 5(a) shows the permeation rate for a forward osmosis membrane module to which the present invention is applied, and Figure 5(b) shows the membrane output for a forward osmosis membrane module to which the present invention is applied. The results are shown in Figure 5(a).

[0111] Furthermore, the outlet pressure, which is the pressure when saltwater W1 is discharged from the second discharge pipe 24, was measured, and the membrane output value was calculated based on the formula "permeation rate × outlet pressure × 100 × 9.8 ÷ membrane area". The results are shown in Figure 5(b). Here, the parabola shown in Figure 5(b) represents the predicted membrane output of a flat permeable membrane.

[0112] For comparison, we also fabricated one forward osmosis membrane element with three membrane leaves, which was wrapped around the main conduit 30 as in the conventional method. Here, the forward osmosis membrane element fabricated for comparison differs from the forward osmosis membrane element 3 of the present invention in that the membrane leaf does not have a cavity, the membrane leaf is wrapped around the main channel such that the direction from the bend towards the adhesive edge is the winding direction, and a partition is provided inside the membrane leaf so that moisture moves around the inside of the membrane leaf by the partition. In other words, the forward osmosis membrane element fabricated for comparison does not have its adhesive edge pressed against the main channel by the membrane leaf and compressed.

[0113] Then, a conventional forward osmosis membrane element, fabricated for comparison, was housed in Case 2 as shown in Figure 4, and a conventional forward osmosis membrane module as shown in Figure 4 was constructed.

[0114] Furthermore, saltwater and freshwater were supplied to a conventional forward osmosis membrane module. At this time, the saltwater was pressurized to a pressure of approximately 1.5 MPa, and the freshwater was pressurized to a pressure of approximately 0.2 MPa, so that the "forward osmosis phenomenon" would occur. Then, the permeation rate and membrane output were calculated in the same manner as with the forward osmosis membrane module 1 of the present invention. The results are shown in Figure 5.

[0115] In Figure 5, the symbols "●" and "▲" indicate the results of the forward osmosis membrane module of the present invention, while the symbol "■" indicates the results of a conventional forward osmosis membrane module. As is clear from Figure 5, the forward osmosis membrane module 1 of the present invention showed higher values ​​for both permeation rate and membrane output than the conventional forward osmosis membrane module. In particular, the permeation rate and membrane output of the conventional forward osmosis membrane module were close to zero.

[0116] In other words, conventional forward osmosis membrane modules have partitions within the membrane leaflets, causing water to circulate within the leaflets. This reduces the smoothness of the water flow, resulting in stagnation within the membrane leaflets. Consequently, the permeability of the membrane leaflets decreases in these stagnant areas, and as a result, the overall permeability of the forward osmosis membrane element decreases, making it impossible to efficiently permeate water.

[0117] Furthermore, in conventional forward osmosis membrane modules, the membrane leaves are wrapped around the main channel so that the direction from the bend towards the adhesive edge is the wrapping direction. In other words, the membrane leaves are not wrapped around the main channel so that the direction from the adhesive edge towards the bend is the wrapping direction. Therefore, the adhesive edge is not pressed against the main channel by the membrane leaves and is not compressed. Furthermore, in conventional forward osmosis membrane elements, each membrane leaf is offset from the others and wrapped around the main channel. As a result, the adhesive edges of the inner membrane leaves do not overlap with the outer membrane leaves and are therefore not pressed or compressed by the outer membrane leaves. Therefore, it is thought that in conventional forward osmosis membrane elements, when liquid is supplied to the inside of the membrane leaf and the membrane leaf expands, the adhesive edge ruptures, causing the liquid to leak from the adhesive edge, and thus preventing efficient water infiltration.

[0118] In addition, conventional forward osmosis membrane elements do not have cavities, so the area of ​​the membrane leaf that is supplied with liquid and expands is adjacent to the adhesive edge. As a result, when liquid is supplied to the membrane leaf and it expands, the expansion force is transmitted to the adhesive edge, and combined with the fact that the adhesive edge is not compressed, the adhesive edge ruptures when the membrane leaf expands, causing liquid to leak from the adhesive edge, and thus preventing efficient water infiltration.

[0119] In contrast, the forward osmosis membrane element 3 of the present invention, which is provided in the forward osmosis membrane module 1 of the present invention, is wrapped around the main conduit 30 such that the direction from the adhesive edges (311A, 312A, 313A) toward the bent portions (311C, 312C, 313C) is the winding direction, so that the adhesive edges (311A, 312A, 313A) are pressed against the main conduit 30 and compressed by the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313. Therefore, it is thought that the adhesive edges (311A, 312A, 313A) became less prone to rupture, preventing the liquid contained in the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 from leaking out from the adhesive edges (311A, 312A, 313A), thus allowing water to permeate efficiently.

[0120] In addition, the forward osmosis membrane element 3 of the present invention has cavities (311B, 312B, 313B) adjacent to the adhesive edges (311A, 312A, 313A) of the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313, and the cavities (311B, 312B, 313B) are more easily compressed than the adhesive edges (311A, 312A, 313A). Therefore, it is thought that the first flow channels 33 of the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313, which are supplied with liquid and expand, can be kept away from the adhesive edges (311A, 312A, 313A) without being adjacent to them. As a result, the expanding force is less likely to be directly transmitted to the adhesive edges (311A, 312A, 313A), making it less likely for the adhesive edges (311A, 312A, 313A) to break, preventing the liquid from leaking from the adhesive edges (311A, 312A, 313A), and allowing water to permeate efficiently.

[0121] Furthermore, liquid is supplied to the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313, and the pressure at the first flow path 33 of each of the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 becomes greater than the pressure at the "adhesive edges (311A, 312A, 313A) and cavities (311B, 312B, 313B)". Therefore, it is thought that this pressure difference causes the first flow channels 33 of the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 to press the "adhesive edges (311A, 312A, 313A) and cavities (311B, 312B, 313B)" against the main pipe 30, further compressing the "adhesive edges (311A, 312A, 313A) and cavities (311B, 312B, 313B)," which in turn makes the adhesive edges (311A, 312A, 313A) even less likely to break, preventing liquid from leaking from the adhesive edges (311A, 312A, 313A) and allowing water to permeate efficiently.

[0122] [Osmotic power generation] Figure 6 is a block diagram of an osmotic power generation system based on a permeable membrane module to which the present invention is applied.

[0123] The osmotic power generation system mainly consists of a first liquid tank 4 in which saltwater W1 is stored, a second liquid tank 5 in which freshwater W2 is stored, the forward osmosis membrane module 1 of the present invention, and a water turbine generator 6. Here, the first liquid tank 4 is connected to the first supply pipe 21 of the forward osmosis membrane module 1 of the present invention, and the second liquid tank 5 is connected to the second supply pipe 22 of the forward osmosis membrane module 1 of the present invention, and brine W1 and fresh water W2 are supplied to the forward osmosis membrane module 1 of the present invention, respectively.

[0124] As described above, the flow of saltwater W1 and freshwater W2 within the forward osmosis membrane module 1 of the present invention is as described above, and freshwater W2 flowing through the second channel 35 flows into the first channel 33 within the membrane leaf 31 by the forward osmosis phenomenon, thereby generating a mixed water W3 of saltwater W1 and freshwater W2.

[0125] In the forward osmosis membrane module 1 of the present invention, the mixed water W3 discharged from the case 2 through the second discharge pipe 24 is then supplied to the turbine generator 6. The mixed water W3 supplied to the turbine generator 6 is used to rotate prime movers such as turbines, thereby enabling power generation by the turbine generator 6. Furthermore, the mixed water W3 discharged from the first channel 33 has increased energy due to the inflow of fresh water W2 from the second channel 35, and with this mixed water W3, the turbine generator 6 can generate electricity more efficiently.

[0126] Furthermore, the brine W1 stored in the first liquid tank 4 is generally concentrated brine with a high salt concentration, but it is also possible to use brine concentrated by the forward osmosis phenomenon of the permeable membrane module of the present invention as this concentrated brine.

[0127] Specifically, in the osmotic power generation system shown in Figure 6, the forward osmosis membrane module 1 of the present invention is further placed upstream of the first liquid tank 4, and the first liquid tank 4 is connected to the second discharge pipe 24 of the forward osmosis membrane module 1 of the present invention.

[0128] Furthermore, in the forward osmosis membrane module 1 of the present invention, which is located upstream of the first liquid tank 4, the brine W1 supplied to the compartment A through the first supply pipe 21 is pressurized to make the pressure of the brine W1 higher than the pressure of the fresh water W2 supplied to the main pipeline 30 through the second supply pipe 22, thereby causing a "forward osmosis phenomenon" in which the brine W1 flows into the main pipeline 30.

[0129] The brine W1, concentrated by the forward osmosis phenomenon, is discharged from the case 2 through the second discharge pipe 24 of the forward osmosis membrane module 1 of the present invention and supplied to the first liquid tank 4. As described above, a mixture of saltwater W1 and freshwater W2, W3, is then supplied to the turbine generator 6, enabling power generation by the turbine generator 6.

[0130] Thus, even when seawater is desalined by the forward osmosis phenomenon of the permeable membrane module of the present invention, the concentrated seawater generated can be used for osmotic power generation.

[0131] Furthermore, the mixed water W3 supplied to the turbine generator 6 has its salinity diluted by the inflow of fresh water W2. Therefore, the mixed water W3 can be discharged directly outside the system, for example, into the sea.

[0132] On the other hand, any unpermeated water W4 in the freshwater W2 supplied to the forward osmosis membrane module 1 of the present invention that could not flow into the first channel 33 can be discharged directly outside the system, for example into the sea, through the first discharge pipe 23, or it can be circulated and supplied again to the second liquid tank 5. Furthermore, the water generated by the forward osmosis phenomenon in the forward osmosis membrane module 1 of the present invention, which is located upstream of the first liquid tank 4, is fresh water and can be used for purposes other than osmotic power generation or supplied to the second liquid tank 5.

[0133] As described above, in the forward osmosis membrane element 3 of the present invention, the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 are each wrapped around the main conduit 30 such that the direction from the adhesive edge portions (311A, 312A, 313A) toward the bent portions (311C, 312C, 313C) is the winding direction. As a result, the adhesive edge portions (311A, 312A, 313A) are pressed against the main conduit 30 and compressed by the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313. Therefore, the adhesive edges (311A, 312A, 313A) become less likely to break, and the liquid contained in the first membrane leaf 311, the second membrane leaf 312, and the third membrane leaf 313 can be prevented from leaking from the adhesive edges (311A, 312A, 313A).

[0134] As a result, the forward osmosis membrane element 3 of the present invention can efficiently permeate water. Furthermore, the forward osmosis membrane module 1 of the present invention, which includes such a forward osmosis membrane element 3, can also efficiently permeate water. [Explanation of Symbols]

[0135] 1. Forward Osmosis Membrane Module 2 cases 20 Main body 21 1st supply pipe 22 2nd supply pipe 23 1st discharge pipe 24 2nd discharge pipe 3. Forward Osmosis Membrane Element 30 Main pipeline 301 Inlet 302 Outflow hole 31 Membrane Leaf 31A Adhesive edge 31B Cavity 31C Folding point 311 First membrane leaf 311A Adhesive Edge 311B Cavity 311C Folding point 312 Second membrane leaf 312A Adhesive Edge 312B Cavity 312C Folding point 313 Third membrane leaf 313A Adhesive Edge 313B Cavity 313C Folding point 32. First Spacer 33. First channel 34. Second Spacer 35 Second channel 36 Support Member 36A Through hole 37. Sealant 38 First opening 39. Second opening 4 1st liquid tank 5 Second liquid tank 6. Hydroelectric generator

Claims

1. Multiple membrane leaves are formed in which the overlapping edges opposite to the bent portion of a folded sheet-like material are bonded together, and a first channel into which a predetermined first liquid is supplied is formed inside. The membrane leaf is wound so that the direction from the bonded edge of the membrane leaf toward the bending point is the winding direction, and a second liquid having a different solute concentration from the first liquid is supplied in the axial direction parallel to the first flow path, and an outlet hole for the second liquid is formed on the side surface, the main pipe having A second channel is formed in the gap between adjacent membrane leaves, with one side communicating with the outflow hole and the other side open. A cavity is provided in the aforementioned membrane leaf adjacent to the adhesive edge of the said membrane leaf. Permeable membrane element.

2. The position of the adhesive edge of the outer membrane leaf is shifted in the opposite direction to the winding direction compared to the position of the adhesive edge of the inner membrane leaf. The permeable membrane element according to claim 1.

3. In the direction connecting the bent portion of the membrane leaf and the adhesive edge, the total length of the adhesive edge and the cavity of the inner membrane leaf is longer than the total length of the adhesive edge and the cavity of the outer membrane leaf. The permeable membrane element according to claim 1.

4. The ratio of the length of the adhesive edge of the membrane leaf to the length of the cavity in the direction connecting the bent portion of the membrane leaf and the adhesive edge is 9:1 to 5:

5. The permeable membrane element according to claim 3.

5. Inside the membrane leaf, a flat plate-shaped first spacer is positioned at a distance corresponding to the length of the cavity, away from the adhesive edge, and has a mesh pattern formed on it. The device comprises a flat plate-shaped second spacer, which is positioned between adjacent membrane leaves forming the second channel and has a mesh structure formed on it. The permeable membrane element according to claim 3.

6. A case having a first supply pipe and a second supply pipe positioned at a predetermined location on one end of a cylindrical main body, a first discharge pipe positioned at a predetermined location on the side of the main body, and a second discharge pipe positioned at a predetermined location on the other end of the main body, The case comprises a permeable membrane element housed within the case, The aforementioned permeable membrane element is Multiple membrane leaves are formed in which the overlapping edges opposite to the bent portion of a folded sheet-like material are bonded together, and a predetermined first liquid is supplied from a first opening communicating with the first supply pipe to a second opening communicating with the second discharge pipe. The membrane leaf is wound so that the direction from the bonded edge of the membrane leaf toward the bending point is the winding direction, and a second liquid having a different solute concentration from the first liquid is supplied in the axial direction parallel to the first flow path, and an outlet hole for the second liquid is formed on the side surface, The aforementioned permeable membrane element is A second channel is formed in the gap between adjacent membrane leaves, with one side communicating with the outflow hole and the other side open. A cavity is provided in the aforementioned membrane leaf adjacent to the adhesive edge of the said membrane leaf. Permeable membrane module.

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