Spiral filter

Abstract

[Problem] To provide a spiral filter which is compact, allows filtration fluid to flow out easily, and improves filtration efficiency. [Solution] A spiral filter 10 has an element 22 comprising: an inner tube 21; a leaf 11 in which a stock solution net 13 is interposed between separation membranes 12; and a filtrate net 14. The leaf 11 and the filtrate net 14 are alternately wound on the inner tube 21. When the effective filtration area of the element 22 is Se, the volume of the element 22 is V, the number of leaves 11 is N, the effective length in the winding direction of the leaf 11 is L1, and the effective length in the axial direction of the leaf is L2, P in the following formula (1) is 2.5 or more.　 (1): P = ((Se / V) × N) / (L1 + L2)

Description

Spiral Filter

[0001] The present invention relates to a spiral filter having a spiral membrane element used for solid-liquid separation, and more particularly to a spiral filter suitable for filtering a large amount of low-concentration liquid.

[0002] Spiral filters having spiral membrane elements have been used for membrane filtration of wastewater or clean water, or for recovering valuables by concentrating them. A typical structure of such a spiral filter is shown, for example, in Figures 1 and 2 of Patent Document 4. Specifically, a leaf filter, in which a raw liquid flow path material is sandwiched between two separation membranes, and a permeate flow path material are alternately wound around a hollow inner tube having numerous holes on the side, and the periphery (three sides) of the separation membranes are sealed with an adhesive to prevent mixing of the raw liquid and the permeate.

[0003] It has been known that in a spiral filter having a spiral-wound membrane element, the effective membrane area per element volume can be increased by reducing the thickness of the separation membrane and increasing the number of contained leaves, thereby improving treatment efficiency (see Patent Document 1).

[0004] Patent Document 1 states that "In a typical spiral-type membrane element, about 15 to 30 sets of membrane leaves L are wound, but if the thickness of the composite semipermeable membrane is smaller than the conventional value, it becomes possible to wind 20 to 35 sets of membrane leaves L. This makes it possible to increase the effective membrane area of ​​the composite semipermeable membrane and enable even larger-volume treatment, thereby significantly improving treatment efficiency." (paragraph

[0039] ).

[0005] It is also known that in order to increase the effective membrane area per element volume, the thickness of the separation membrane and the thickness of the feed-side channel material can be reduced, or the winding pressure can be increased, and that the aspect ratio of the leaf can be reduced in order to reduce pressure loss (see Patent Documents 2 and 3). Patent Document 2 states, "Example 1: Using the obtained composite semipermeable membrane B (note: thickness 90 μm), a permeate-side channel material (a tricot knit fabric made of polyethylene terephthalate) having the thickness, density, and membrane support index shown in Table 1, and a feed-side channel material (a polyethylene net) having a thickness of 0.86 mm (34 mil), an adhesive (urethane resin made by Sanyu Rec Co., Ltd.) was applied to form sealed portions with a width of 10 to 30 mm, and the membrane leaves (total number of membrane leaves: 24 leaves) were wound around a central tube (outer diameter 39 mm) with a winding pressure of 8 kgf to produce a spiral-type membrane element with an outer diameter of 8 inches and a length of 40 inches." (paragraph

[0106] ), and Table 1 also states that for Example 1, the effective membrane area was 440 ft ２ (40.88m ２ ), the outer diameter of the element is 8 inches (20.32 cm), and the length of the element is 40 inches (101.6 cm). The outer diameter and length of the element are the same as in Example 1, and the effective membrane area is 635 ft ２ (58.99m ２ Regarding Example 5 of the same publication, it is stated that "Example 5: A membrane element was produced in the same manner as in Example 1, except that in Example 1, a composite semipermeable membrane C (thickness: 80 μm) and a feed-side flow path material (a polyethylene net) having a thickness of 0.43 mm (17 mil) were used and the membrane element was produced at a winding pressure of 15 kgf." (paragraph

[0110] ).

[0006] On the other hand, Patent Document 3 (Japanese Patent Laid-Open Publication No. 61-283307) focuses on the aspect ratio of the leaf shape (length in the winding direction relative to length in the axial direction) as a means for reducing pressure loss in the permeate flow path and increasing the amount of permeate, and describes a "spiral membrane element in which a laminate consisting of a hollow tube having numerous small holes and a semipermeable membrane, a raw water flow path material, and a permeate flow path material is spirally wound around the hollow tube, wherein the shape of a single leaf is characterized by an aspect ratio falling within the range of 0.2 to 0.35" (Claims), and further describes that "it can be seen that the smaller the aspect ratio of the leaf, the smaller the pressure loss in the permeate flow path."

[0007] Patent No. 7089352 Patent No. 7037306 Japanese Patent Application Laid-open No. 1983-283307

[0008] In order to increase the effective membrane area (effective filtration area) per unit volume of a spiral membrane element (hereinafter simply referred to as "element"), it is effective to reduce the thickness of the separation membrane or the thickness of the raw liquid net (feed-side flow path material) to increase the total length in the winding direction of the separation membrane that can be stored in the element (Patent Document 1) or to increase the winding pressure (Patent Document 2). However, Patent Documents 1 and 2 do not disclose how to design a spiral filter so as to suppress flow path resistance and improve treatment efficiency (filtration efficiency) by relating the length of the leaves in the winding direction to the dimensions (outer diameter and axial length) that define the element volume, the effective filtration area, and the number of leaves.

[0009] Patent Document 3 describes a method for reducing pressure loss by reducing the aspect ratio of the leaves (length in the winding direction relative to length in the axial direction) and increasing the number of leaves, but does not specifically disclose the relationship between the aspect ratio of the leaves and the element dimensions, effective filtration area, or number of leaves.

[0010] As described above, the design of a compact spiral filter that increases the effective filtration area per element volume while reducing flow path resistance and improving treatment efficiency (filtration efficiency) has not been considered in the past.

[0011] An object of the present invention is to provide a spiral filter that is compact, allows filtration fluid to easily flow out, and improves filtration efficiency by relating various elements related to the element.

[0012] One aspect of the present invention is a spiral filter having an element including an inner tube, leaves each having a separation membrane with a stock solution net interposed therebetween, and a filtrate net, the leaves and the filtrate net being alternately wound around the inner tube, wherein the effective filtration area of ​​the element is Se, the volume of the element is V, the number of the leaves is N, and the effective length of the leaves in the winding direction is L. １ , the effective length of the leaf in the axial direction is L ２ In this case, the spiral filter has a value P of 2.5 or more in the following formula (1): P = ((Se / V) × N) / (L １ +L ２ ) ... (1) (where V is πr where Le is the axial length of the element and r is the radius of the element. ２ ×Le, and L １ is the effective filtration area per leaf Se / N divided by 2 and then the effective length L of the leaf in the axial direction ２ is the value divided by L ２ is the value obtained by subtracting the width of the sealing portion from Le.)

[0013] According to the present invention, it is possible to provide a spiral filter that is compact, allows filtration fluid to easily flow out, and has high filtration efficiency.

[0014] 1 is a structural diagram of a spiral filter according to an embodiment of the present invention. FIG. 2 is a diagram showing an outline of a test device used in paint filtration tests of Example 1 and Comparative Example 1.

[0015] A spiral filter according to one embodiment of the present invention (hereinafter referred to as "the present embodiment") is a spiral filter having an element including an inner tube, leaves each having a separation membrane with a stock solution net interposed therebetween, and a filtrate net, the leaves and the filtrate net being alternately wound around the inner tube, wherein the effective filtration area of ​​the element is Se, the volume of the element is V, the number of leaves is N, and the effective length of the leaves in the winding direction is L. １, the effective length of the leaf in the axial direction is L ２ In this case, the spiral filter has a value P of 2.5 or more in the following formula (1): P = ((Se / V) × N) / (L １ +L ２ ) ... (1) (where V is πr where Le is the axial length of the element and r is the radius of the element. ２ ×Le, and L １ is the effective filtration area per leaf Se / N divided by 2 and then the effective length L of the leaf in the axial direction ２ is the value divided by L ２ is the value obtained by subtracting the width of the sealing portion from Le.)

[0016] A P value of 2.5 or more can provide a spiral filter that is compact, has reduced flow resistance, facilitates the outflow of filtrate, and has high filtration efficiency. The P value is preferably 3 or more. The upper limit of the P value is preferably about 10.

[0017] In the spiral filter according to this embodiment, in order to make the P equal to or greater than 2.5, the effective filtration area Se of the element is 5 to 38 m ２ It is preferable that the length is 5 to 20 m. ２ It is more preferable that Se is 8 to 16 m ２ When Se is in the above range, a more compact spiral filter can be provided.

[0018] In the spiral filter according to this embodiment, the element volume V is 4000 to 25000 cm ３ It is preferable that the ３ By setting V within the above range, a more compact spiral filter can be provided.

[0019] The spiral filter according to this embodiment has an element volume of 1 cm ３ The effective filtration area per unit area is 14 cm ２ / cm ３ The upper limit of Se / V is 20 cm２ / cm ３ By setting Se / V within the above range, it is possible to provide a spiral filter having higher filtration efficiency even when the filter is made compact as described above.

[0020] The spiral filter according to this embodiment has an effective length L in the winding direction of the leaf. １ is preferably 390 to 800 mm. １ In practice, it is more preferable that L is 390 to 600 mm. １ When the thickness is within the above range, the flow resistance is reduced, and a spiral filter having high filtration efficiency can be provided.

[0021] The spiral filter according to this embodiment has an effective length L in the axial direction of the leaf. ２ is preferably 400 to 800 mm. ２ In practice, it is more preferable that L is 400 to 600 mm. ２ When the thickness is within the above range, the flow resistance is reduced, and a spiral filter having high filtration efficiency can be provided.

[0022] The spiral filter according to this embodiment has an effective length L in the axial direction of the leaf. ２ The effective length L of the leaf in the winding direction １ The ratio L １ / L ２ is preferably 0.5 to 1.9, and more preferably 0.5 to 1.3. １ / L ２ When the diameter of the spiral filter is relatively small, it is possible to provide a spiral filter that is compact, has reduced flow resistance, and has high filtration efficiency.

[0023] In the spiral filter according to this embodiment, the number N of the leaves is preferably 16 to 40, and in practical terms, more preferably 20 to 26. When N is within the above range, the opening area to the inner tube is increased, facilitating the outflow of the filtrate, and a spiral filter with high filtration efficiency can be provided.

[0024] The structure and components of the spiral filter according to this embodiment will be described below with reference to FIG.

[0025] The spiral filter 10 according to this embodiment has the same basic structure and components as the conventional one shown in FIG. 1 . Specifically, the spiral filter 10 includes multiple sets (hereinafter also referred to as "leaf sets"), each set consisting of a leaf 11, each consisting of a stock solution net 13 sandwiched between two separation membranes 12, and a filtrate net 14 laminated on the leaf 11. The multiple leaf sets are wound around a hollow inner tube 21 having multiple holes 21h on its side to form an element, which is housed in a substantially cylindrical outer container (not shown). The stock solution net 13 has a stock solution flow path that communicates with the outside via a stock solution inlet 31 and a concentrated solution outlet 32 ​​at both ends of the spiral filter 10. The filtrate net 14 has a permeate flow path that communicates with the inner tube 21, one end of which is sealed and the other end (the concentrated solution outlet 32 ​​side in the figure) serves as a permeate outlet 33. Sealing portions (not shown) with a width Lp formed by resin potting to prevent leakage of the raw liquid to the permeate side are present at both axial ends of the separation membrane element adjacent to the filtrate net 14. In addition, a sealing resin (not shown) is also applied to the outermost surface of the element.

[0026] The spiral filter 10 according to this embodiment has the separation membrane 12 described above and can be used for membrane filtration of wastewater and clean water, recovery of valuable resources by concentration, etc. The separation membrane 12 can be a flat membrane for various applications such as microfiltration, ultrafiltration, and nanofiltration. One example is one having a chlorinated polyvinyl chloride porous layer on both sides of a polyethylene terephthalate nonwoven fabric layer (support).

[0027] As with conventional spiral filters, various materials and shapes can be used for the stock solution net 13, as long as they can maintain the gap between the two separation membranes 12 and ensure the flow of stock solution. For example, nets made of synthetic resin fibers such as polyolefin, polyester, and polyamide can be used. Among these, it is preferable to use a net with a structure in which the filaments forming the mesh intersect three-dimensionally, as this can reduce the flow resistance of the flushing liquid that washes away deposits from the filtration membrane surface. One example is a polypropylene net manufactured by extruding filamentous resin and intersecting them three-dimensionally.

[0028] The thickness of the stock solution net 13 is preferably 0.5 to 1 mm. In those in which the filaments forming the mesh intersect three-dimensionally, the thickness of the net is slightly less than twice the filament diameter. By making the thickness of the stock solution net 0.5 mm or more, intermembrane blockage due to deposits on the filtration membrane surface does not occur, and flushing cleaning can be easily performed. On the other hand, by making the thickness of the stock solution net 1 mm or less, the stock solution flow path does not become wide, and effective flushing cleaning can be performed.

[0029] The filtrate net 14 can be made of various materials and shapes as long as it can maintain the gap between the two separation membranes 12 and ensure the flow of permeate. For example, a net made of synthetic resin fibers such as polyolefin, polyester, or polyamide can be used. Conventional spiral filtration filters often use woven or knitted fabrics with fine mesh and high flow resistance as the permeate flow path material. In contrast, in the filter of this embodiment, it is desirable to use a filtrate net with a coarser mesh and lower flow resistance so that the permeate flow rate can be increased during high-yield operation or dead-end filtration operation. Therefore, it is preferable to use a net with a structure in which the filaments forming the mesh cross three-dimensionally, similar to the feed net. One example is a long-fiber knitted fabric made of polyethylene terephthalate.

[0030] The thickness of the filtrate net 14 is preferably 0.2 to 1 mm. In those in which the filaments forming the mesh intersect three-dimensionally, the thickness of the net is slightly less than twice the filament diameter. By making the thickness of the filtrate net 0.2 mm or more, the flow of permeate can be ensured without narrowing the permeate flow path, while by making the thickness of the filtrate net 1 mm or less, an increase in the volume of the element can be suppressed. Furthermore, because the thickness of the filtrate net is thin, it is less likely to bite into the membrane when pressure is applied from the raw water side. This prevents the raw liquid flow path from widening and an increase in flow into the raw liquid flow path, thereby ensuring the flow of permeate.

[0031] The mesh size of the net used for the filtrate net 14 is preferably such that the density of parallel filaments (number of filaments per unit length) is 10 to 20 filaments / cm. By setting the filament density to 10 filaments / cm or more, stress concentration on the filtration membrane at the three-dimensional intersection of the filaments is prevented, and the two separation membranes 12 are not placed in close proximity, ensuring the flow of permeate. Furthermore, when pressure is applied from the raw water side, the filtrate net is less likely to bite into the membrane, widening the raw liquid flow path and preventing an increase in flow into the raw liquid flow path, thereby ensuring the flow of permeate. On the other hand, by setting the filament density to 20 filaments / cm or less, high flow resistance in the permeate flow path is prevented when the thickness of the filtrate net is 0.2 to 1 mm.

[0032] The inventors of the present invention have investigated the relationships between the various elements that make up the spiral filter element, and have sought a spiral filter structure that is compact, allows for easy outflow of filtrate, and improves filtration efficiency. As a result, they have found that by increasing the effective filtration area per volume of an element housed in an outer container of limited volume, and by setting the effective length of the leaves in the winding direction and the length in the axial direction of the element within appropriate ranges, it is possible to accommodate a large number of leaves even in a compact size, while suppressing an increase in flow resistance of the permeate liquid due to pressure loss caused by an increase in winding pressure.

[0033] The elements related to the above means are the following five parameters:１ : Effective length of leaf in winding direction L ２ : effective length of leaf in axial direction N: number of leaves Se: effective filtration area of ​​element V: volume of element = [radius of element (r)] ２ ×π × axial length of element (Le), or volume of inner tube ([radius of inner tube] ２ × π × length of element in axial direction (Le)) + volume of one leaf set (actual length of leaf in winding direction (L １ ') × axial length of element (Le) × thickness of leaf set × number of leaf sets

[0034] Axial effective length of leaf L ２ is the axial length Le of the element minus the width Lp of the sealing portion. Lp is set so as to achieve both reliable sealing and a sufficient effective filtration area. For example, the maximum diameter of a currently widely used spiral filter is 8 inches (outer diameter of approximately 200 mm), and in this case, it is preferable that the width be approximately 20 mm on one side (Lp = 40 mm).

[0035] The effective filtration area Se of the element is expressed as the actual length of the leaf in the winding direction L １ ´, then L １ ´×L ２ × N × 2, the resin application area (2rπ × L ２ , r is the radius of the element). Since it is folded in half, the area is the number of leaves times 2, so it is "x 2". That is, Se = L １ ´×L ２ ×N×2−2rπ×L ２ In addition, in this calculation formula, "L １ ´×L ２ × N × 2" is the actual length of the leaf in the winding direction. １ Since it is based on the assumption that the length L is approximately the same for all leaves, "×N" is used. １ If different leaves are included, then each leaf is assigned a L １ ´×L ２ The sum of these is doubled and the value is "L１ ´×L ２ ×N×2".

[0036] By applying resin to the outermost periphery of the element, １ Since it is unknown how much the effective length of ' has decreased, Se is calculated using the above formula, and L １ Furthermore, the effective filtration area Se is originally calculated from the effective length of each filter, so Se = L １ ×L ２ ×N×2, and L １ =(Se / N) / (2L ２ ) That is, the effective length L of the leaf in the winding direction １ is obtained by dividing Se / N by 2 to obtain the effective length L of the leaf in the axial direction. ２ In the case of the spiral filter according to this embodiment, L １ and L １ The difference between the widths ' is preferably about 7 to 12 mm.

[0037] Among the above parameters, "Se / V" is the effective filtration area per unit volume of the element, and is therefore a parameter related to filtration efficiency. １ "," "L ２ The larger " and "N" are, the larger the effective filtration area is. １ " is related to the flow path length of the permeate leading to the inner tube, and "L ２ " is related to the flow path length of the raw water and the flow path length of the permeate in the inner tube, so "L １ +L ２ The smaller " " is, the smaller the flow path resistance can be. Therefore, the following formula (1) was set as an equation expressing the balance between filtration efficiency and flow path resistance, and the lower limit value of P that can achieve an appropriate balance between filtration efficiency and flow path resistance was determined using the following examples and comparative examples. P = ((Se / V) × N) / (L １ +L ２ ) (1) As a result, it was found that when P is 2.5 or more, the above balance is excellent.

[0038] The spiral filter according to the present embodiment is designed to achieve an appropriate balance between filtration efficiency and flow path resistance, and therefore provides the following additional benefits. Specifically, the spiral filter according to the present embodiment provides particularly excellent filtration efficiency when operated at a low supply pressure for the raw liquid, a range not typically used in conventional spiral filters. Specifically, when the spiral filter according to the present embodiment is filtered at a pressure of the raw liquid flowing into the spiral filter (also referred to as the pressure at which the raw liquid is supplied) of less than 0.4 MPa, the spiral filter according to the present embodiment provides a greater amount of water permeation per unit time than conventional spiral filters under the same conditions. This benefit is most pronounced when the supply pressure for the raw liquid is 0.25 MPa or less, and even more pronounced when the supply pressure is 0.15 MPa or less or 0.1 MPa or less.

[0039] The above-described effects are achieved because the spiral module of this embodiment is designed with consideration given to the flow resistance, including the flow resistance of the permeate. When the raw water supply pressure is low, the pressure of the permeate after passing through the permeable membrane becomes even lower. However, in the spiral module of this embodiment, the flow resistance, including the flow resistance of the permeate, is appropriately set, so that the permeate flow is not extremely restricted or stagnant, thereby maintaining a stable permeation rate. In particular, the permeation rate can be maintained even when the raw water supply pressure is 0.25 MPa or less, and a practically sufficient permeation rate can be ensured even when the pressure is 0.15 MPa or less or 0.1 MPa or less. Note that in conventional spiral modules, the flow resistance, including the flow resistance of the permeate, is not appropriately set, resulting in a high permeation rate, particularly for the permeate. Therefore, when the raw water supply pressure is low, the driving force for the filtrate to pass through the membrane due to the pressure difference between the raw water side and the permeate side of the membrane is reduced, and the permeate flow is also significantly restricted. As a result, a stable permeation rate cannot be maintained, and the permeation rate is significantly reduced.

[0040] In the spiral filter according to this embodiment, the pressure of the stock solution flowing into the spiral filter is preferably set to be lower than 0.4 MPa, and more preferably set to 0.25 MPa or less, 0.15 MPa or less, or 0.1 MPa or less. By lowering the pressure of the stock solution flowing into the spiral filter, the power required to pressurize the stock solution can be reduced, thereby reducing the power consumption required for the filtration process.

[0041] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0042] (Example 1) A separation membrane with a length of 985 mm and a width of 460 mm was folded in half (492.5 mm x 2), and a stock solution net was sandwiched between the two. A leaf with a 20 mm sealing portion at each end in the width direction by resin potting was laminated with the filtrate net, and the volume per sheet was 263 cm ３ A leaf set of 125 mm (125.1 mm) was formed, and 20 sets of these leaf sets were wound around an inner tube having an outer diameter of 33 mm (radius of 16.5 mm). Resin was applied to the outermost surface, and an element according to Example 1 having a diameter 2r of 125 mm (125.1 mm) and a length Le of 460 mm was produced.

[0043] The values ​​of the elements of the element according to Example 1 are as follows: Effective length L of the leaf in the axial direction ２ = (axial length of element Le - width of sealing portion Lp) = 460 mm - 20 mm x 2 = 420 mm Effective filtering area of ​​element Se = (actual length of leaf in winding direction L １ ' × 2 × effective leaf axial length L ２ × number of leaves N) - surface area (2πr × effective length of leaf in axial direction L ２ ) = (492.5 mm x 2 x 420 mm x 20 sheets) / 10 ６ - (125.1mm x 3.1416 x 420mm) / 10 ６ = 8.11 m ２ Effective length L of the leaf in the winding direction １ = Effective filtering area of ​​element per leaf Se / N ÷ 2 ÷ Effective length of leaf in axial direction L ２ = (8.11 m ２／ 20 sheets) ÷ 2 ÷ 420 mm x 10 ６= 483 mm Element volume V = πr ２ × Element length Le = 3.1416 × (62.55 mm) ２ ×460mm / 1000=5654cm ３ The volume V of the element can also be calculated by the following method: Volume per leaf set = Actual length of the leaf in the winding direction (L １ ') × axial length of element (Le) × thickness of leaf set = (492.5 mm × 460 mm × 1.161 mm) / 1000 = 263.02 cm ３ Volume V of the element = volume of the inner tube + volume per leaf set x number of leaves = (3.1416 x (16.5 mm) ２ ×460mm) / 1000+263.02cm ３ x20 pieces = 5654cm ３ Effective filtration area per unit volume of element Se / V = 8.11 m ２ ×10000 / 5654cm ３ = 14.34 cm －１ Therefore, P in equation (1) is: P = ((Se / V) × N) / (L １ +L ２ )=(14.34cm －１ × 20 sheets) / (48.3 cm + 42 cm) = 3.18.

[0044] In Example 1, the effective filtration area per unit volume of the element Se / V is large at 14 or more, the number of leaves N is large at 20 or more, and the effective length L in the winding direction of the leaves is large. １ , the effective length L of the leaf in the axial direction ２ However, since the diameter is in the appropriate range of 400 to 800 mm, the P value is large at 2.5 or more, the flow resistance of the permeate is small, and as shown in Table 2, the filtration efficiency (permeation rate) is improved.

[0045] (Comparative Example 1) As Comparative Example 1, the design elements of the spiral filter YSP-100M manufactured by GS Yuasa Membrane, model 3, were examined. The current model 3 has an element length Le of 880 mm, an element diameter 2r of 81 mm, and an element volume V of 4535 cm ３The actual length of the leaf in the winding direction is 2200 mm, and the effective length of the leaf in the winding direction is L １ is 2136 mm, and the effective length in the axial direction L ２ is 800 mm, and the number N is two.

[0046] When comparing Comparative Example 1 with Example 1, the effective length L of the leaf in the winding direction is shorter than that of Example 1. １ and the effective length L of the leaf in the axial direction ２ is large, but the number of leaves N is significantly smaller at 2, so the effective filtration area Se of the element is 6.84 m ２ On the other hand, the element volume V is also smaller than that of Example 1, so the effective filtration area Se / V per unit volume of the element is 15.1 cm －１ , which is similar to that of Example 1. However, the effective length L １ and the effective length L in the axial direction ２ Since the leaf number N is large, the flow resistance of the permeated liquid increases, and since the leaf number N is significantly small at 2, the number of openings in the inner tube also decreases, resulting in a high flow resistance of the permeated liquid. P in formula (1) in Comparative Example 1 was P = (15.1 x 2) / (213.6 + 80) = 0.10. The P value was less than 2.5, resulting in a high flow resistance of the permeated liquid, and as shown in Table 2, the filtration efficiency (permeation rate) was lower than in Example 1. The above results for Example 1 and Comparative Example 1 are shown in Table 1.

[0047]

[0048] For Example 1 and Comparative Example 1, a paint filtration test was carried out under the following conditions.

[0049] The outline of the evaluation coating solutions used in the coating filtration test is as follows: The water-based coatings shown in Table 2 were dissolved in tap water to prepare the coating solutions shown in Table 3, which were used as evaluation coating solutions.

[0050]

[0051]

[0052] Using the coating solutions shown in Table 3, the supply pressure was changed in the test device shown in Figure 2, and the amount of filtrate after 15 minutes of operation was measured. The results of the coating filtration test are shown in Table 4.

[0053]

[0054] (Comparative Example 2) As Comparative Example 2, the design elements of the current spiral filter UFC-150N manufactured by GS Yuasa Membrane were examined. The UFC-150N has an element length Le of 960 mm, an element diameter 2r of 155 mm, and an element volume V of 18114 cm ３ The number of leaf sets is 14, the actual length of the leaf in the winding direction is 760 mm, and the effective length L １ is 743 mm, and the width of the sealing portion of the leaf in the axial direction is 30 mm on each side, so the effective axial length L ２ is 900 mm.

[0055] In Comparative Example 2, the effective length L of the leaf in the winding direction is shorter than that in Example 1. １ and the effective length L of the leaf in the axial direction ２ Therefore, the effective filtration area of ​​the element is 18.7 m ２ However, since the element volume V is about 3.2 times that of Example 1, the effective filtration area Se / V per unit volume of the element is 10.3 cm －１ The effective length L of the leaf in the winding direction is １ and the effective length L in the axial direction ２ is larger than that of Example 1, the flow resistance of the permeated liquid is large, and since the leaf number N is 14, which is smaller than that of Example 1, the number of openings in the inner tube is also smaller than that of Example 1, and as a result, it can be said that the filtration efficiency (water permeation rate) is lower than that of Example 1. P in formula (1) in Comparative Example 2 was P = (10.3 × 14) / (74.3 + 90) = 0.88.

[0056] (Comparative Example 3) As Comparative Example 3, the design elements of the current spiral filter UFC-130N manufactured by GS Yuasa Membrane were examined. The UFC-130N has an element length Le of 960 mm, an element diameter 2r of 125 mm, and an element volume V of 11781 cm３ The actual length of the leaf in the winding direction is 760 mm, and the effective length of the leaf in the winding direction is L １ is 735 mm, and the effective length in the axial direction L ２ is 900 mm, and the number N is 8.

[0057] When comparing Comparative Example 3 with Example 1, the number of leaves N is smaller than that of Example 1, but the effective length L in the winding direction of the leaves is １ and the effective length L of the leaf in the axial direction ２ Because of this, the effective filtration area of ​​the element is 10.6 m ２ However, since the element volume V is more than twice that of Example 1, the effective filtration area Se / V per unit volume of the element is 9.0 cm －１ , which is even smaller than that of Comparative Example 2. In addition, the effective length L １ and the effective length L in the axial direction ２ Since the number of leaflets N is large, the flow resistance of the permeated liquid is large, and since the number of leaflets N is significantly small at 8, the number of openings in the inner tube is also smaller than in Example 1, and as a result, it can be said that the filtration efficiency (permeation rate) is lower than in Example 1. P in formula (1) in Comparative Example 2 was P = (9.0 × 8) / (73.5 + 90) = 0.44.

[0058] From the above results, it can be seen that the effects of the present invention can be obtained when P in formula (1) is approximately 2.5 or more.

[0059] Next, the following simulation was performed for the condition where P in formula (1) was 2.5 or more. The volume of the inner tube, the thickness of the leaf set, and the width Lp of the sealed portion were fixed values ​​similar to those in Example 1.

[0060] (Changing the Number of Leaves) The leaf size was the same as in Example 1 (Pattern 1), and only the number of leaves N was changed from 20 to 1, 16, and 40 (Patterns 2 to 4), respectively. In this case, if the number of leaves was 16 or more, P was 2.5 or more. Since highly versatile spiral filters often have a maximum diameter of 8 inches (approximately 200 mm), N is preferably 16 to 40 leaves, and in consideration of winding pressure and separation filtration thickness, it is more preferable for N to be approximately 20 to 26 leaves in practical use.

[0061] (Effective length L in the leaf winding direction １ Actual length L of the leaf in the winding direction １ ' only 400 mm (effective length L １ In this case, the effective filtration area per element volume is slightly smaller, but the L １ +L ２ Since the value of P is smaller than that of Example 1, it exceeds 3. １ ' are 600 mm (effective length L １ is 589 mm), 800 mm (effective length L １ The length was changed to 788mm and 789mm (patterns 6 to 8). １ +L ２ Therefore, if the number of leaves N is 20, P may be less than 2.5. However, if the number of leaves N is increased, P can be made 2.5 or more. Therefore, the effective length L in the winding direction １ is preferably about 390 mm to 800 mm, and more preferably about 390 to 600 mm in practical terms.

[0062] (Effective length L in the leaf axial direction ２ Change of effective length L of leaf in axial direction ２ When only the length was changed to 400 mm (Pattern 9), the effective filtration area per unit volume of the element was about the same, but P was larger than in Example 1 and exceeded 3. ２When the leaf number N is changed to 600 mm and 800 mm, respectively (patterns 10 to 13), P may be less than 2.5 when the leaf number N is 20, but P can be made 2.5 or more by increasing the leaf number N. Therefore, the effective length L in the leaf axial direction ２ is preferably about 400 mm to 800 mm, and more preferably from a practical standpoint, 400 to 600 mm.

[0063] (Effective length L in the leaf winding direction １ and the effective length L in the axial direction ２ (Change both) Actual length L in the leaf winding direction １ ', effective length L in the leaf axial direction ２ Both are 400 mm (effective length L １ When the length is changed to 391 mm (pattern 14), the number of leaves N is 20 and P exceeds 3. １ ', L ２ Both are 685 mm (effective length L １ 674 mm, 675 mm), or 800 mm (effective length L １ When the leaf length is changed to 788 mm and 790 mm (patterns 15 to 18), P falls below 2.5 when the number of leaves N is 20, but by increasing the number of leaves N to 25 or 30, respectively, P can be made 2.5 or more. From the above, when the leaf size is increased, P can be made 2.5 or more by increasing the number of leaves N.

[0064] The above simulation results are summarized in Table 5.

[0065]

[0066] As a result of the above simulation, the preferable condition for making P in formula (1) 2.5 or more is when V is 4000 to 25000 cm ３ Se / V is 14 cm ２ / cm ３ The length L of each leaf in the winding direction is １ is 390 to 800 mm, and the axial length L per leaf ２ is 400 to 800 mm, L １ / L ２It was found that the value of the leaf number N was 0.5 to 1.9, and the number of leaves N was 16 to 40.

[0067] According to the present invention, it is possible to provide a compact spiral filter that is compact, has improved filtrate efficiency, and can operate with low energy consumption. This makes it possible to perform processing in an energy-saving and space-saving manner in fields such as filtration processing of wastewater or tap water, or recovery of valuable materials by concentration.

[0068] 10 Spiral filter 11 Leaf 12 Separation membrane 13 Stock solution net 14 Filtrate net 21 Inner tube 22 Element 31 Stock solution inlet 32 ​​Concentrate outlet 33 Permeate outlet L １ Effective length of leaf in winding direction L ２ Effective axial length of leaf

Claims

1. A spiral filter having an element comprising an inner tube, a leaf having a separation membrane with a stock solution net interposed therebetween, and a filtrate net, the leaf and the filtrate net being alternately wound around the inner tube, wherein the effective filtration area of ​​the element is Se, the volume of the element is V, the number of the leaves is N, and the effective length of the leaves in the winding direction is L. １ , the effective length of the leaf in the axial direction is L ２ In this case, P in the following formula (1) is 2.5 or more. P=((Se / V)×N) / (L １ +L ２ ) ... (1) (where V is πr where Le is the axial length of the element and r is the radius of the element.) ２ ×Le, and L １ is the effective filtration area per leaf Se / N divided by 2 and then the effective length L of the leaf in the axial direction ２ is the value divided by L ２ is the value obtained by subtracting the width of the sealing portion from Le.) 2. The effective filtration area Se of the element is 5 to 20 m ２ 2. The spiral filter of claim 1, wherein:

3. The element volume V is 4000 to 25000 cm ３ The spiral filter according to claim 1, wherein the spiral filter is as described above.

4. The effective filtration area Se / V per element volume of 1 cm ３ is 14 cm ２ / cm ３ or more. The spiral filter according to any one of claims 1 to 3.

5. Effective length L of the leaf in the winding direction １ The spiral filter according to any one of claims 1 to 3, wherein the diameter of the spiral groove is 390 to 800 mm.

6. The effective axial length L of the leaf ２ The spiral filter according to any one of claims 1 to 3, wherein the diameter of the spiral groove is 400 to 800 mm.

7. The effective axial length L of the leaf ２ The effective length L of the leaf in the winding direction １ The spiral filter according to any one of claims 1 to 3, wherein the ratio of is 0.45 to 1.

30.

8. The spiral filter according to any one of claims 1 to 3, wherein the number N of leaves is 16 to 40.

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