Flow channel spacer and spiral membrane module

Abstract

To provide a flow channel spacer that can minimize pressure loss while suppressing formation of a concentration polarization layer.SOLUTION: A flow channel spacer 4, which is interposed between separation membranes wound around a water collection pipe in a spiral membrane module, has a diagonal grid-like mesh structure which includes multiple first linear parts 41 that extend such that each of the first linear parts is inclined obliquely upward relative to a flow direction X and are arranged so as to have an interval between each other, multiple second linear parts 42 that extend such that each of the second linear parts is inclined obliquely downward relative to the flow direction X and are arranged so as to have an interval between each other, and in which the multiple first linear parts 41 and the multiple second linear parts 42 intersect each other so as to form multiple openings 43 between the multiple first linear parts 41 and the multiple second linear parts 42. The first linear parts 41 include multiple first arcs 410 segmented for each opening 43. The second linear parts 42 include multiple second arcs 420 segmented for each opening 43. The central angle of the first and second arcs is 10° or more and 50° or less.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a flow path spacer and a spiral wound membrane module. [Background technology]

[0002] Spiral-type membrane modules equipped with spiral separation membranes (reverse osmosis membranes, ultrafiltration membranes, etc.) are used in water treatment processes such as seawater desalination and pure water production. This type of spiral-type membrane module includes a water collection pipe, a plurality of separation membranes wound in a spiral shape around the water collection pipe, and flow path spacers interposed between adjacent separation membranes (e.g., Patent Documents 1 and 2).

[0003] The flow path spacer is a member for securing a flow path for the raw water to be treated between adjacent separation membranes. The flow path spacer generally has a mesh structure in which a plurality of warp threads (vertical threads) and a plurality of weft threads (horizontal threads) are arranged in a crossing manner.

[0004] Such a flow path spacer is required to have low pressure loss in the raw water flow path due to the spacer itself acting as an obstacle. In addition, the flow path spacer is required to suppress the formation of a concentration polarization layer. A concentration polarization layer is a layer containing a high concentration of solutes such as ions and salts that cannot permeate the separation membrane, and is formed when the solutes accumulate near the surface of the separation membrane. The concentration polarization layer increases the osmotic pressure near the surface of the separation membrane, causing a decrease in the amount of permeated water.

[0005] It is known that such a concentration polarization layer is difficult to form when the raw water exerts a large shear stress on the separation membrane. Also, when the magnitude of turbulence (turbulent energy) in the raw water is large, the formation of the concentration polarization layer is suppressed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-198849 A [Patent Document 2] Japanese Patent Application Publication No. 11-235520 Summary of the Invention [Problem to be solved by the invention]

[0007] Suppressing the formation of a concentration polarization layer (i.e., increasing the shear stress and turbulence) and minimizing pressure loss are essentially in a trade-off relationship, and it is not easy to achieve both. Conventionally, in order to achieve both, sufficient consideration has not been given to the relationship between the flow direction of the raw water and the shapes of the warp and weft threads that make up the mesh structure.

[0008] An object of the present invention is to provide a flow path spacer capable of suppressing the formation of a concentration polarization layer while minimizing pressure loss, and a spiral wound membrane module including the flow path spacer. [Means for solving the problem]

[0009] The means for solving the above problems are as follows. <1> A flow path spacer to be interposed between separation membranes wound around a water collection pipe of a spiral-type membrane module, the flow path spacer having a plurality of first linear parts each extending at an angle upward with respect to the flow direction of raw water flowing through the water collection pipe and arranged at intervals from each other, when a positive direction perpendicular to the flow direction of raw water flowing through the water collection pipe is defined as up and a negative direction is defined as down, and a plurality of second linear parts each extending at an angle downward with respect to the flow direction and arranged at intervals from each other, the plurality of first linear parts and the plurality of second linear parts intersecting each other to form a diagonal lattice-like mesh such that a plurality of openings are formed between the plurality of first linear parts and the plurality of second linear parts. the first linear portion includes a plurality of first arcs divided for each of the openings, the second linear portion includes a plurality of second arcs divided for each of the openings, the first arcs extend with a predetermined line width so as to be inclined obliquely upward with respect to the flow direction and are curved to bulge downward with respect to an imaginary line passing through both ends in the extension direction, and the second arcs extend with a predetermined line width so as to be inclined obliquely downward with respect to the flow direction and are curved to bulge upward with respect to an imaginary line passing through both ends in the extension direction, and a central angle between the first arc and the second arc is 10° or more and 50° or less.

[0010] <2> The length of the first circular arc and the length of the second circular arc are equal to each other. <1> The flow path spacer according to claim 1 .

[0011] <3> The pitch of the openings is 5 mm. <1> or <2> The flow path spacer according to claim 1 .

[0012] <4> A flow path spacer includes a water collection pipe extending in one direction, a separation membrane wound around the water collection pipe, and a flow path spacer interposed between the separation membrane, the flow path spacer having a plurality of first linear parts that extend so as to be inclined obliquely upward with respect to the flow direction of raw water flowing through the water collection pipe, the plurality of first linear parts being arranged at intervals from each other, and a plurality of second linear parts that extend so as to be inclined obliquely downward with respect to the flow direction, when a positive direction perpendicular to the flow direction of raw water flowing through the water collection pipe is defined as up and a negative direction perpendicular to the flow direction of raw water flowing through the water collection pipe is defined as down, the plurality of first linear parts and the plurality of second linear parts being arranged at intervals from each other, the plurality of first linear parts and the plurality of second linear parts being arranged at intervals from each other, and a flow path spacer having a diagonal lattice-like mesh structure in which first and second linear portions intersect with each other, the first linear portions including a plurality of first circular arcs divided for each of the openings, the second linear portions including a plurality of second circular arcs divided for each of the openings, the first circular arcs extending with a predetermined line width so as to be inclined obliquely upward with respect to the flow direction and curved to bulge downward with respect to an imaginary line passing through both ends in the extension direction, and the second circular arcs extending with a predetermined line width so as to be inclined obliquely downward with respect to the flow direction and curved to bulge upward with respect to an imaginary line passing through both ends in the extension direction, and a central angle between the first and second circular arcs is 10° or more and 50° or less. Effect of the Invention

[0013] According to the present invention, it is possible to provide a flow path spacer capable of suppressing the formation of a concentration polarization layer and minimizing pressure loss, and a spiral wound membrane module including the flow path spacer. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view of a spiral membrane module according to an embodiment of the present invention. [Diagram 2] Partial plan view of raw water side spacer [Diagram 3] Cross section of line AA in Figure 2 [Figure 4] A partially enlarged plan view of the raw water side spacer shown in FIG. [Diagram 5]FIG. 5 is an explanatory diagram showing the central angle θ (°) of an arc corresponding to the second arc shown in FIG. [Figure 6] An explanatory diagram showing the mesh structures when the central angle θ is ±30° and ±50°. [Figure 7] A graph showing the relationship between the positive and negative central angles θ and the shear stress and pressure loss [Figure 8] A graph showing the relationship between the positive and negative central angles θ and the turbulent energy [Figure 9] A graph showing the relationship between the positive central angle θ and the shear stress and pressure loss [Figure 10] A graph showing the relationship between the positive central angle θ and turbulent energy [Figure 11] A graph showing the relationship between the central angle θ and the shear stress and pressure loss when the pitch is "4mm, 4mm" [Figure 12] A graph showing the relationship between the central angle θ and turbulent energy when the pitch is "4mm, 4mm" [Figure 13] A graph showing the relationship between the central angle θ and the shear stress and pressure loss when the pitch is "6mm, 6mm" [Figure 14] A graph showing the relationship between the central angle θ and turbulent energy when the pitch is "6mm, 6mm" DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] [Spiral-type membrane module] Fig. 1 is a perspective view of a spiral wound membrane module 1 according to one embodiment of the present invention. Fig. 1 shows a part of the structure of the spiral wound membrane module 1 in an unfolded state. The spiral wound membrane module 1 (hereinafter, may be simply referred to as "module 1") is an apparatus for performing water treatment such as desalination of seawater and production of pure water. The module 1 mainly includes a water collection pipe 2, a plurality of separation membranes 3, a raw water side spacer 4, and a permeate side spacer 5.

[0016] The separation membranes 3 are wound around the water collection pipe 2 while overlapping each other, each forming a flat bag-like structure. Inside the bag-like structure, a permeate side spacer 5 is arranged. The permeate side spacer 5 has the function of securing a space as a flow path for the permeated water between the overlapping parts of the bag-like separation membranes 3. Outside the bag-like structure made of the separation membranes 3, a raw water side spacer 4 (an example of a flow path spacer) is arranged between adjacent separation membranes 3. The raw water side spacer 4 secures a space as a flow path for the raw water between adjacent separation membranes 3. The raw water side spacer 4 will be described in detail later.

[0017] The open end of the bag-shaped structure made of the separation membrane 3 is connected to the water collection pipe 2 so that the flow path of the permeate communicates with the water collection pipe 2. The type of raw water is not particularly limited, and may be, for example, seawater, wastewater, or water for producing pure water.

[0018] The water collection pipe 2 has the function of collecting the permeated water that has permeated each separation membrane 3 and directing it to the outside of the module 1. The water collection pipe 2 is a cylindrical pipe that extends in one direction and has multiple holes formed on its circumferential surface. The water collection pipe 2 is, for example, a processed pipe made of synthetic resin such as polyvinyl chloride. Multiple holes are provided at predetermined intervals along the longitudinal direction (one direction) of the water collection pipe 2. The permeated water flows into the water collection pipe 2 through these holes.

[0019] Examples of the separation membrane 3 include a reverse osmosis membrane, a nanofiltration membrane, an ultrafiltration membrane, and a microfiltration membrane.

[0020] The permeate side spacer 5 is a sheet-like member having a mesh structure. The permeate side spacer 5 is made of a molded product of synthetic resin such as polyolefin resin (polypropylene, etc.).

[0021] The module 1 is used, for example, housed in a cylindrical pressure vessel (housing). When raw water to be treated is supplied into the pressure vessel, the raw water flows into the raw water flow path from one end side of the module 1 (the rear side of the paper in FIG. 1). The raw water is filtered and concentrated by the separation membrane 3. As a result, concentrated raw water and permeated water are produced. The concentrated raw water is discharged from the other end side of the module 1 (the front side of the paper in FIG. 1) to the outside of the module 1. The permeated water is discharged to the outside of the module 1 through the permeated water flow path and the water collection pipe 2. The module 1 produces permeated water from which solutes such as ions and salts contained in the raw water have been removed.

[0022] [Raw water side spacer] Next, the raw water side spacer 4 will be described in detail. The raw water side spacer 4 is interposed between the separation membranes 3 wound around the water collection pipe 2 of the spiral membrane module 1, and is sandwiched between adjacent separation membranes 3 to ensure a flow path for the raw water to be treated. Fig. 2 is a partial plan view of the raw water side spacer 4, and Fig. 3 is a cross-sectional view taken along line AA in Fig. 2.

[0023] The raw water side spacer 4 is a sheet-like member having a mesh structure, as shown in Fig. 2. The arrows shown in Fig. 2 indicate the flow direction X of the raw water flowing through the water collection pipe 2. In other words, the raw water flows from the left side to the right side in Fig. 2. For ease of explanation, in this specification, the positive direction perpendicular to the flow direction X of the raw water flowing through the water collection pipe 2 is defined as up, and the negative direction is defined as down.

[0024] The raw water side spacer 4 generally has a diagonal lattice-like mesh structure 40 as shown in Fig. 2. Such a mesh structure 40 has a plurality of first linear portions 41 and a plurality of second linear portions 42. The plurality of first linear portions 41 and the plurality of second linear portions 42 are arranged to intersect with each other so that a plurality of openings 43 are formed between the plurality of first linear portions 41 and the plurality of second linear portions 42.

[0025] In this embodiment, the first linear portions 41 and the second linear portions 42 are integrally formed in such a manner that the second linear portions 42 are placed on the upper side of the first linear portions 41 (the front side of the paper in FIG. 2). The first linear portions 41 and the second linear portions 42 are fixed (fused) to each other at the overlapping portions. In other embodiments, the first linear portions 41 and the second linear portions 42 may be integrally formed in such a manner that the first linear portions 41 are placed on the upper side of the second linear portions 42, as long as the object of the present invention is not impaired.

[0026] The first linear portions 41 are generally arranged at intervals from one another, and each extends at an angle obliquely upward with respect to the flow direction X of the raw water flowing through the water collection pipe 2. Each of the first linear portions 41 is linear and has a predetermined line width (constant line width) and a predetermined thickness (constant thickness). The first linear portions 41 are arranged at equal intervals from one another.

[0027] The second linear portions 42 are generally arranged at intervals from one another, each extending at an angle downward with respect to the flow direction X. Each of the second linear portions is linear and has a predetermined line width (constant line width) and a predetermined thickness (constant thickness). The second linear portions 42 are arranged at equal intervals from one another.

[0028] In this embodiment, the line width of the first linear portion 41 and the line width of the second linear portion 42 are the same. In addition, the thickness of the first linear portion 41 and the thickness of the second linear portion 42 are also the same. FIG. 3 shows a cross section of the first linear portion 41. In FIG. 3, the double arrow in the up-down direction represents the line width W of the first linear portion 41, and the double arrow in the left-right direction represents the thickness (height) D of the first linear portion 41. In this specification, the line widths of the first linear portion 41 and the second linear portion 42 represent the size of the widest part, and the thicknesses represent the size of the thickest part.

[0029] The line width W of each of the first linear portion 41 and the second linear portion 42 is not particularly limited as long as it does not impair the object of the present invention, but is preferably, for example, 0.43 mm or more and 0.63 mm or less. The thickness D of each of the first linear portion 41 and the second linear portion 42 is not particularly limited as long as it does not impair the object of the present invention, but is preferably, for example, 0.33 mm or more and 0.53 mm or less. It is preferable that the line width W is larger than the thickness D.

[0030] The thickness of the raw water side spacer 4 is the total thickness of the first linear portion 41 and the second linear portion 42. However, when the first linear portion 41 and the second linear portion 42 are fused to each other, a reduction of about 0.02 mm occurs in the total thickness thereof.

[0031] 3, the upper surface 41a and the lower surface 41b of the first linear portion 41 are flat, and both side surfaces 41c, 41d are curved outward in an arc shape. The second linear portion 42, like the first linear portion 41, has flat upper and lower surfaces, and both side surfaces curved outward in an arc shape.

[0032] For convenience of explanation, the first linear portion 41 is divided into a plurality of sections for each opening 43 in its length direction (a direction in which it extends while inclining obliquely upward with respect to the flow direction X). In this specification, the divided sections are referred to as "first arcs 410". It can be said that the first linear portion 41 includes a plurality of first arcs 410 divided for each opening 43. The first linear portion 41 is formed by connecting the first arcs 410 in a line. The first arc 410 extends with a predetermined line width so as to incline obliquely upward with respect to the flow direction X, and forms an arc that bulges downward with respect to an imaginary straight line that passes through both ends in the extension direction (length direction of the first arc 410).

[0033] For convenience of explanation, the second linear portion 42 is divided into a plurality of sections for each opening 43 in its length direction (a direction in which it extends while inclining obliquely downward with respect to the flow direction X). In this specification, the divided sections are referred to as "second arcs 420". It can be said that the second linear portion 42 includes a plurality of second arcs 420 divided for each opening 43. The second linear portion 42 is formed by connecting the second arcs 420 in a line. The second arc 420 extends with a predetermined line width so as to incline obliquely downward with respect to the flow direction X, and forms an arc that bulges upward with respect to an imaginary straight line that passes through both ends in the extension direction (length direction of the second arc 420).

[0034] Fig. 4 is an enlarged plan view of a portion of the raw water side spacer 4 shown in Fig. 2. Fig. 4 shows a portion of the raw water side spacer 4 that forms one opening 43 (the portion of the raw water side spacer 4 surrounded by a square frame S in Fig. 2).

[0035] As shown in Fig. 4, one opening 43 is formed by two adjacent first linear portions 41 (two first arcs 410) and two adjacent second linear portions 42 (two second arcs 420). In Fig. 4, of the two first linear portions 41, one first linear portion 41 is disposed on the upper left side, and the other first linear portion 41 is disposed on the lower right side. Also, in Fig. 4, of the two second linear portions 42, one second linear portion 42 is disposed on the upper right side, and the other second linear portion 42 is disposed on the lower left side.

[0036] In FIG. 4, a point where the first linear portion 41 arranged on the upper left side and the second linear portion 42 arranged on the upper right side overlap and intersect with each other is shown as a first intersection point A1. Also, in FIG. 4, a point where the first linear portion 41 arranged on the upper left side and the other second linear portion 42 arranged on the lower left side overlap and intersect with each other is shown as a second intersection point A2. Also, in FIG. 4, a point where the other first linear portion 41 arranged on the lower right side and the one second linear portion 42 arranged on the upper right side overlap and intersect with each other is shown as a third intersection point A3. Also, in FIG. 4, a point where the other first linear portion 41 arranged on the lower right side and the other second linear portion 42 arranged on the lower left side overlap and intersect with each other is shown as a fourth intersection point A4.

[0037] 4, for convenience of explanation, an imaginary straight line L1 passing through the first intersection point A1 and the second intersection point A2, and an imaginary straight line L2 passing through the third intersection point A3 and the fourth intersection point A4 are shown. The straight lines L1 and L2 extend while inclining obliquely upward with respect to the flow direction X. In the case of this embodiment, they extend while inclining obliquely upward at an angle of 45° with respect to the flow direction X.

[0038] 4, for convenience of explanation, an imaginary straight line L3 passing through the first intersection A1 and the third intersection A3, and an imaginary straight line L4 passing through the second intersection A2 and the fourth intersection A4 are shown. The straight lines L3 and L4 extend while inclining obliquely downward with respect to the flow direction X. In the case of this embodiment, they extend while inclining downward at an angle of 45° with respect to the flow direction X.

[0039] The positions of the first intersection A1, the second intersection A2, the third intersection A3 and the fourth intersection A4 correspond to the vertices of an imaginary square formed corresponding to one opening 43, respectively.

[0040] The pitch of the openings 43 is the length B1 between the first intersection A1 and the fourth intersection A4, or the length B1 between the second intersection A2 and the third intersection A3. In this embodiment, the length B1 and the length B2 are the same. The length B1 and the length B2 each correspond to the length of the diagonal of the virtual square described above.

[0041] The size of the pitch of the openings 43 of the raw water side spacer 4 is not particularly limited as long as it does not impair the object of the present invention, but is preferably, for example, 4 mm or more and 6 mm or less, and particularly preferably 5 mm.

[0042] In one of the first linear portions 41 arranged on the upper left side, a portion between the first intersection point A1 and the second intersection point A2 becomes one of the first arcs 410 constituting the opening 43. This one of the first arcs 410 extends with a predetermined line width so as to be inclined obliquely upward with respect to the flow direction X, and one end in the extension direction (length direction) is a place represented by the first intersection point A1, and the other end is a place represented by the second intersection point A2. In this specification, one end of the first arc 410 is represented by the symbol A1, and the other end is represented by the symbol A2. The first arc 410 forms an arc that bulges downward with respect to an imaginary straight line L1 that passes through both end portions A1 and A2.

[0043] In the other first linear portion 41 arranged on the lower right side, a portion between the third intersection A3 and the fourth intersection A4 becomes the other first circular arc 410 constituting the opening 43. This other first circular arc 410 extends with a predetermined line width so as to be inclined obliquely upward with respect to the flow direction X, and one end in the extension direction (length direction) is a place represented by the third intersection, and the other end is a place represented by the fourth intersection A4. In this specification, one end of the first circular arc 410 is represented by the symbol A3, and the other end is represented by the symbol A4. The first circular arc 410 forms an arc that bulges downward with respect to an imaginary straight line L2 that passes through both end portions A3 and A4.

[0044] In one second linear portion 42 arranged on the upper right side, a portion between the first intersection A1 and the third intersection A3 becomes one second arc 420 constituting the opening 43. This one second arc 420 extends with a predetermined line width so as to be inclined obliquely downward with respect to the flow direction X, and one end in the extension direction (length direction) is a place represented by the first intersection A1, and the other end is a place represented by the third intersection A3. In this specification, one end of the second arc 420 is represented by the symbol A1, and the other end is represented by the symbol A3. The second arc 420 forms an arc curved so as to bulge upward with respect to an imaginary straight line L3 passing through both end portions A1 and A3.

[0045] In the other second linear portion 42 arranged on the lower left side, a portion between the second intersection point A2 and the fourth intersection point A4 becomes the other second arc 420 constituting the opening 43. The other second arc 420 extends with a predetermined line width so as to be inclined obliquely downward with respect to the flow direction X, and one end in the extension direction (length direction) is a place represented by the second intersection point A2, and the other end is a place represented by the fourth intersection point A4. In this specification, one end of the second arc 420 is represented by the symbol A2, and the other end is represented by the symbol A4. The second arc 420 forms an arc curved so as to bulge upward with respect to an imaginary straight line L4 passing through both end portions A2 and A4.

[0046] The central angle of the first arc 410 is in the range of 10° to 50° (preferably, 30° to 50°).

[0047] Furthermore, the central angle of the second arc 420 is in the range of 10° to 50° (preferably, 30° to 50°). Note that the central angle of the second arc 420 and the central angle of the first arc 410 are preferably the same as each other.

[0048] Here, referring to FIG. 5, the relationship between the second arc 420 and the central angle (θ) will be briefly described by taking the second arc 420 as an example. FIG. 5 is an explanatory diagram showing the central angle θ (°) of the arc 420a corresponding to the second arc 420 shown in FIG. 4. FIG. 5 shows a triangle (isosceles triangle) with the first intersection A1, the third intersection A3, and the center O of the arc 420a as vertices. Note that in FIG. 5, the length m between the first intersection A1 and the third intersection A3 is shown as a value when the pitch of the opening 43 is 5 mm. Also, the length from the center O to the first intersection A1 and the length from the center O to the third intersection A3 correspond to the radius r of the arc 420a. The relationship between the radius r and the central angle θ (cosθ) can be understood from the cosine theorem that holds for the above-mentioned triangle.

[0049] From this relationship, it can be said that as the central angle θ (°) increases, the degree of bending (curvature = 1 / r) of the second arc 420 increases. Similarly, in the case of the first arc 410, as the central angle increases, the degree of bending (curvature = 1 / r) of the first arc 410 increases.

[0050] A plurality of first arcs 410, each of which has an arc shape, are connected to one another in a line to form one first linear portion 41. A plurality of second arcs 420, each of which has an arc shape, are connected to one another in a line to form one second linear portion 42.

[0051] In addition, the diagonal lattice mesh structure 40 of this embodiment can also be said to be formed overall by a plurality of ripple-shaped portions moving toward the flow direction X (for example, a roughly semicircular arc portion formed by the second arc 420 between the first intersection A1 and the third intersection A3, and the first arc 410 between the third intersection A3 and the fourth intersection A4).

[0052] The raw water side spacer 4 is made of a molded product with synthetic resin as a base material. Examples of synthetic resin include thermoplastic resin and thermosetting resin. As the synthetic resin, thermoplastic resin is preferable from the viewpoint of excellent moldability. Examples of thermosetting resin include phenol resin, epoxy resin, melamine resin, urea resin, etc.

[0053] Examples of the thermoplastic resin include polyolefin resins such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymers, acrylic resins, polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polystyrene resins, acrylonitrile-butadiene-styrene (ABS) resins, modified polyphenylene ether, polyphenylene sulfide, polyamide, polycarbonate, and polyacetal. These may be used alone or in combination of two or more. As the thermoplastic resin, polyolefin resins are preferred.

[0054] The synthetic resin may contain carbon materials such as carbon nanotubes, graphene, and fullerene for the purpose of increasing the hydrophilicity of the surface of the raw water side spacer 4. When a carbon material (carbon nanotubes, etc.) is contained in the synthetic resin, a thin film of water molecules is formed on the surface of the molded product.

[0055] Carbon nanotubes have a structure in which a graphene sheet is rolled up into a cylindrical shape, with a diameter of several nm to several tens of nm and a length of several tens to several thousands of times the diameter. Carbon nanotubes are classified into single-walled carbon nanotubes, which have substantially one graphene sheet layer, and multi-walled carbon nanotubes, which have two or more layers. As long as the object of the present invention is not impaired, either single-walled carbon nanotubes or multi-walled carbon nanotubes may be used as the carbon nanotube.

[0056] Graphene generally refers to a sheet of sp2-bonded carbon atoms having a thickness of one atom (single-layer graphene). However, a material in which single-layer graphene is stacked may also be used as graphene as long as it does not impair the objective of the present invention.

[0057] Fullerene is a carbon cluster having a closed shell structure, and usually has an even number of carbon atoms between 60 and 130. Specific examples of fullerene include C60, C70, C76, C78, ​​C80, C82, C84, C86, C88, C90, C92, C94, C96, and higher-order carbon clusters having more carbon atoms than these. As long as the object of the present invention is not impaired, fullerenes having different carbon numbers may be used in combination, or a single fullerene may be used.

[0058] Among the nanocarbon materials, carbon nanotubes are most preferable from the viewpoints of availability, versatility, and the like.

[0059] The blending ratio of the nanocarbon material to the synthetic resin (e.g., thermoplastic resin such as polyolefin resin) is not particularly limited as long as it does not impair the objective of the present invention, but for example, the nanocarbon material is blended in a ratio of 1 to 30 parts by mass per 100 parts by mass of the synthetic resin.

[0060] In addition to the nanocarbon material, various additives such as ultraviolet protection agents, colorants (pigments, dyes), thickeners, fillers, surfactants, plasticizers, etc. may be appropriately blended into the synthetic resin as long as the objective of the present invention is not impaired.

[0061] The raw water side spacer 4 is appropriately molded using a predetermined mold. For example, when the synthetic resin is made of a thermoplastic resin, the raw water side spacer 4 is appropriately molded by rotary extrusion molding using a predetermined mold. In another embodiment, the raw water side spacer 4 may be manufactured by a molding method that does not use a mold, such as injection molding or 3D printing.

[0062] The raw water side spacer 4 of this embodiment having the above-mentioned structure can suppress the formation of a concentration polarization layer and can keep pressure loss small. If pressure loss is kept small, for example, the power of the pump that sends raw water to the module 1 can be reduced (i.e., power consumption can be reduced). The concentration polarization layer is difficult to form when the shear stress that the raw water applies to the separation membrane 3 is large. Furthermore, if the magnitude of turbulence in the raw water (turbulent energy) is large, the formation of the concentration polarization layer is suppressed. If the formation of the concentration polarization layer is suppressed, it is possible to suppress, for example, a decrease in the separation performance of the separation membrane 3. EXAMPLES

[0063] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples in any way.

[0064] [Verification of differences in central angles of arcs in mesh structure of flow path spacer] A simulation using commercially available fluid analysis software ("Femtet (registered trademark)", Murata Software Co., Ltd.) was performed to obtain the shear stress [Pa], pressure loss [Pa], and turbulent energy (×10 -6 )[m 2 / s 2 ] were determined under the conditions shown below.

[0065] For reference, FIG. 6 illustrates mesh structures in which the central angle θ is +30°, +50°, -30°, and -50°. Note that when the central angle is negative, the direction in which the first linear portion and the second linear portion bulge is opposite to that in the case of a positive central angle. For example, when the central angle θ is +30° as shown in the upper part of FIG. 6, the direction in which the first linear portion and the second linear portion bulge is opposite to that in the case of a central angle of -30° as shown in the lower part of FIG. 6. Also, when the central angle is 0°, the first linear portion and the second linear portion each extend in a straight line (i.e., in the case of a conventional product).

[0066] <Condition> - Thickness of the first and second linear parts: Line width W = 0.53 mm, thickness D = 0.43 mm Total thickness of flow path spacer: 0.84 mm (reduction due to fusion of the first and second linear parts is 0.02 mm) Total thickness of the fluid region: 0.84 mm (the fluid region is the region where the fluid (water) flows, and the total thickness of the fluid region is the same as the total thickness of the flow path spacer) Fluid area: 10mm x 20mm ·Inflow speed: 11.3cm / sec ·Outflow speed: natural outflow - Flow path spacer material: Polyethylene Fluid Type: Water Pitch: B1=5mm, B2=5mm

[0067] The results of the above simulation are shown in Figs. 7 to 10. Fig. 7 is a graph showing the relationship between the positive and negative central angles θ and the shear stress and pressure loss. The horizontal axis of Fig. 7 represents the central angle θ [°], the vertical axis on the left represents the shear stress [Pa], and the vertical axis on the right represents the pressure loss [Pa]. Fig. 8 is a graph showing the relationship between the positive and negative central angles θ and the turbulent energy. The horizontal axis of Fig. 8 represents the central angle θ [°], and the vertical axis represents the turbulent energy (×10 -6 )[m 2 / s 2 ].

[0068] As shown in Figure 7, it was confirmed that when the central angle θ was +30° or +50°, the pressure loss was approximately the same as when the central angle θ was 0° (conventional product). In contrast, when the central angle θ was -30° or -50°, the pressure loss was greater than when the central angle θ was 0°.

[0069] Furthermore, as shown in Figure 7, it was confirmed that when the central angle θ was +30° or +50°, the shear stress was greater than when the central angle θ was 0° or when the central angle θ was -30° or -50°.

[0070] In addition, as shown in FIG. 8, it was confirmed that when the central angle θ was +30° and +50°, the turbulent energy was larger than when the central angle θ was 0°.

[0071] FIG. 9 is a graph showing the relationship between the positive central angle θ and the shear stress and pressure loss. The horizontal axis of FIG. 9 represents the central angle θ [°], the vertical axis on the left represents the shear stress [Pa], and the vertical axis on the right represents the pressure loss [Pa]. FIG. 10 is a graph showing the relationship between the positive central angle θ and turbulent energy. The horizontal axis of FIG. 10 represents the central angle θ [°], and the vertical axis represents the turbulent energy (×10 -6 )[m 2 / s 2 ].

[0072] As shown in FIG. 9, when the central angle θ is in the range of +10° to +50°, the pressure loss is approximately the same as when the central angle θ is 0°, and it was confirmed that the shear stress is greater than when the central angle θ is 0°.

[0073] 10, it was confirmed that the turbulent energy is larger when the central angle θ is +30° to +50° than when the central angle θ is 0°. It was also confirmed that the turbulent energy when the central angle θ is 10° is equivalent to that when the central angle θ is 0°.

[0074] From the above results, it can be said that in a flow path spacer with a mesh structure having a pitch of 5 mm and 5 mm, when the central angle θ is in the range of 10° to 50°, the formation of a concentration polarization layer is suppressed and pressure loss is kept smaller than in the conventional product (when the central angle θ is 0°).

[0075] In particular, when the central angle θ is in the range of 30° or more and 50° or less, it can be said that the formation of the concentration polarization layer is more reliably suppressed and the pressure loss is more reliably suppressed.

[0076] [Verification of differences in pitch in mesh structure of flow channel spacer] Simulations using the above fluid analysis software showed that the shear stress [Pa], pressure loss [Pa], and turbulent energy (×10 -6 )[m 2 / s 2 The simulation conditions other than the pitch were the same as those for the pitch of "5mm, 5mm" described above. The results for the pitch of "4mm, 4mm" are shown in Figures 11 and 12. The results for the pitch of "6mm, 6mm" are shown in Figures 13 and 14.

[0077] FIG. 11 is a graph showing the relationship between the central angle θ and the shear stress and pressure loss when the pitch is "4 mm, 4 mm." The horizontal axis of FIG. 11 represents the central angle θ [°], the vertical axis on the left represents the shear stress [Pa], and the vertical axis on the right represents the pressure loss [Pa]. FIG. 12 is a graph showing the relationship between the central angle θ and turbulent energy when the pitch is "4 mm, 4 mm." The horizontal axis of FIG. 12 represents the central angle θ [°], and the vertical axis represents the turbulent energy (×10 -6 )[m 2 / s 2 ].

[0078] As shown in Fig. 11, when the pitch is "4mm, 4mm", if the central angle θ is +30° or +50°, the pressure loss is larger than when the central angle θ is 0°. As for the shear stress, if the central angle θ is +30° or +50°, it is slightly larger than when the central angle θ is 0°.

[0079] Furthermore, as shown in FIG. 12, when the pitch is "4 mm, 4 mm," if the central angle θ is +30° or +50°, the turbulent energy becomes smaller than when the central angle θ is 0°.

[0080] FIG. 13 is a graph showing the relationship between the central angle θ and the shear stress and pressure loss when the pitch is "6 mm, 6 mm." The horizontal axis of FIG. 13 represents the central angle θ [°], the vertical axis on the left represents the shear stress [Pa], and the vertical axis on the right represents the pressure loss [Pa]. FIG. 14 is a graph showing the relationship between the central angle θ and turbulent energy when the pitch is "6 mm, 6 mm." The horizontal axis of FIG. 14 represents the central angle θ [°], and the vertical axis represents the turbulent energy (×10 -6 )[m 2 / s 2 ].

[0081] As shown in FIG. 13, when the pitch was “6 mm, 6 mm”, even when the central angle θ was +30° or +50°, the results of pressure loss and shear stress were substantially equivalent to those when the central angle θ was 0°.

[0082] As shown in Fig. 14, when the pitch was "6mm, 6mm", when the central angle θ was +30°, the turbulent energy was larger than when the central angle θ was 0°. On the other hand, when the central angle θ was +50°, the magnitude of the turbulent energy was almost the same as when the central angle θ was 0°. [Explanation of symbols]

[0083] 1...spiral membrane module, 2...water collection pipe, 3...separation membrane, 4...raw water side spacer (flow path spacer), 41...first linear portion, 410...first circular arc, 42...second linear portion, 420...second circular arc, 5...permeate side spacer

Claims

1. A flow path spacer to be interposed between separation membranes wound around a water collection pipe of a spiral-type membrane module, When the positive direction perpendicular to the flow direction of the raw water flowing through the water collection pipe is defined as up and the negative direction is defined as down, the mesh structure has a diagonal lattice shape in which the first linear portions and the second linear portions cross each other so that a plurality of openings are formed between the first linear portions and the second linear portions, the first linear portions extending at an angle upward with respect to the flow direction and arranged at intervals from each other, and the second linear portions extending at an angle downward with respect to the flow direction and arranged at intervals from each other, The first linear portion includes a plurality of first arcs each of which is divided for each of the openings, the second linear portion includes a plurality of second arcs each divided for each of the openings, the first circular arc extends with a predetermined line width so as to be inclined obliquely upward with respect to the flow direction, and curves so as to bulge downward with respect to an imaginary straight line passing through both end portions in the extension direction, the second circular arc extends with a predetermined line width so as to be inclined obliquely downward with respect to the flow direction, and curves so as to bulge upward with respect to an imaginary straight line passing through both end portions in the extension direction, A flow path spacer in which a central angle of each of the first and second arcs is 10° or more and 50° or less.

2. 2. The flow path spacer of claim 1, wherein the length of the first arc and the length of the second arc are the same.

3. 3. A flow path spacer according to claim 1, wherein the pitch of the openings is 5 mm.

4. A water collection pipe extending in one direction; A separation membrane wound around the water collection pipe; A flow path spacer interposed between the separation membranes, When the positive direction perpendicular to the flow direction of the raw water flowing through the water collection pipe is defined as up and the negative direction is defined as down, the mesh structure has a diagonal lattice shape in which the first linear portions and the second linear portions cross each other so that a plurality of openings are formed between the first linear portions and the second linear portions, the first linear portions extending at an angle upward with respect to the flow direction and arranged at intervals from each other, and the second linear portions extending at an angle downward with respect to the flow direction and arranged at intervals from each other, The first linear portion includes a plurality of first arcs each of which is divided for each of the openings, the second linear portion includes a plurality of second arcs each divided for each of the openings, the first circular arc extends with a predetermined line width so as to be inclined obliquely upward with respect to the flow direction, and curves so as to bulge downward with respect to an imaginary straight line passing through both end portions in the extension direction, the second circular arc extends with a predetermined line width so as to be inclined obliquely downward with respect to the flow direction, and curves so as to bulge upward with respect to an imaginary straight line passing through both end portions in the extension direction, a flow path spacer, the central angle between the first arc and the second arc being 10° or more and 50° or less.

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