Hollow fiber membrane module and method for manufacturing hollow fiber membrane module

Abstract

To provide an open hole structure that reduces pressure loss generated in an open hole which is provided in a hollow fiber module adhesion converging part.SOLUTION: In a hollow fiber membrane module comprises: a hollow fiber membrane bundle 6 comprising a plurality of hollow fiber membranes; a cylindrical case for accommodating the hollow fiber membrane bundle; a first adhesion converging part 7a which adheres and converges one end of the hollow fiber membrane bundle and blocks the end of the hollow fiber membrane bundle, a plurality of open holes 10 which are provided in the first adhesion converging part and extend in an axial direction of the hollow fiber membrane bundle, and a second adhesion converging part that adheres and converges the other end of the hollow fiber membrane bundle. The open hole is configured from a first flow channel 11a from an inlet, in which a fluid to be treated is introduced, to a depth H, and a second flow channel 11b from a most downstream part of the first flow channel to an outlet of the open hole. The first flow channel is on the same axis as the second flow channel, and the first flow channel is reduced in a diameter thereof between the inlet, in which the fluid to be processed is introduced, and the second flow channel.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a hollow fiber membrane module and a method for producing the hollow fiber membrane module. [Background technology]

[0002] Hollow fiber membrane modules are generally used for filtering unwanted substances from a fluid to be treated, and are configured such that at least one end of a hollow fiber membrane bundle, which is a bundle of approximately several hundred to several tens of thousands of hollow fiber membranes, is adhesively bundled with an adhesive resin and fixed in a module case. For example, Patent Document 1 discloses a hollow fiber membrane module in which both ends of the hollow fiber membrane bundle are adhesively bundled and one of the adhesively bundled parts has a plurality of through-holes, and these through-holes mainly serve as supply ports for the fluid to be treated.

[0003] Hollow fiber membrane modules are generally operated using either dead-end filtration or cross-flow filtration, taking into account the properties of the fluid being treated. Conventionally, hollow fiber membrane modules have been widely used in applications with relatively low turbidity, such as pretreatment of seawater for desalination, and in disinfection and turbidity control of drinking water and industrial water. Dead-end filtration, which offers superior power costs, has been the preferred method. On the other hand, in applications where the fluid being treated is highly turbid, such as food and beverage applications and sewage and wastewater treatment, cross-flow filtration is often used, which suppresses the deposition of suspended solids on the membrane surface. Furthermore, in recent years, there has been an increasing demand for gas membrane separation technology that can separate and purify only the target substances, with the aim of reducing the environmental impact of manufacturing processes. This has led to an increasing demand for cross-flow filtration in gas separation applications as well. Among these, external pressure crossflow filtration, which generates a parallel flow to the membrane surface around the hollow fiber membrane, is superior to internal pressure crossflow filtration in that it has lower pressure loss and eliminates the risk of clogging of the hollow fiber membrane's hollow space with suspended solids, making it suitable for use with treated fluids containing large amounts of suspended solids. However, operating a hollow fiber membrane module using external pressure crossflow filtration requires continuous circulation of the treated fluid around the membrane surface around the hollow fiber membrane, resulting in higher power costs than dead-end filtration. One way to reduce power costs is to reduce the pressure loss generated in the hollow fiber membrane module. The pressure loss generated in a hollow fiber membrane module varies depending on the filtration operating conditions of the treated fluid and the structure of the hollow fiber membrane module. For example, in food and beverage applications, the treated fluid is often highly viscous and requires filtration operation at a high membrane surface linear velocity, making pressure loss particularly high. In particular, the through-holes in the adhesive converging section experience significant pressure loss when the treated fluid passes through them during filtration, leading to increased power costs. For example, Patent Document 2 discloses the preferred aperture ratio and circular equivalent diameter of the through-holes provided in the adhesive bundling section in order to solve various problems, including not only pressure loss but also poor adhesion of the hollow fiber membrane bundle and accumulation of suspended matter due to stagnation of the treated fluid. Furthermore, the adhesive bundling section has the function of sealing the ends of the hollow fiber membranes to prevent the fluid to be treated from mixing into the permeating fluid flowing through the hollow fiber membranes, and it is necessary to ensure sealing performance when fabricating the adhesive bundling section and through-holes. For example, Patent Document 3 discloses a sealing method in which the ends of the hollow fiber membranes are sealed by enclosing them in the adhesive bundling section, and shows that the inside of the hollow parts of the hollow fiber membranes in the adhesive bundling section are sealed with an adhesive resin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-220446 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-262206 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-205981 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when treating a highly viscous and highly membrane-surface linear velocity fluid using an external pressure cross-flow filtration system, the specifications for the aperture ratio and the equivalent circle diameter of the through-holes shown in Patent Document 2 alone are insufficient to reduce pressure loss. It would be more effective to design the through-holes so that they are less likely to cause pressure loss, but no such prior art documents have been found. In addition, in the sealing method disclosed in Patent Document 3, if the viscosity of the adhesive resin is high, the adhesive resin may not penetrate into the hollow fiber membranes and only the tip portions may be sealed. On the other hand, if the viscosity of the adhesive resin is low or the inner diameter of the hollow fiber membranes is small, the adhesive resin may be sucked up inside the hollow fiber membranes by capillary action to a height above the adhesive bundling section, reducing the effective membrane area. Therefore, in order to prevent the adhesive resin from penetrating into the hollow fiber membranes, the ends of the hollow fiber membranes may be sealed before bonding and bundling. In such cases where the hollow fiber membranes are hollow inside the adhesive bundling section, if an attempt is made to process the through-holes into a structure that is less likely to cause pressure loss after bonding and bundling the hollow fiber membrane bundle, the hollow fiber membranes near the through-holes may be damaged during processing, which could impair sealing properties, posing a problem.

[0006] An object of the present invention is to provide a through-hole structure that reduces pressure loss caused by through-holes provided in an adhesive bundling section of a hollow fiber membrane module, and to provide a method for forming the through-hole structure using an easy method that does not require post-processing. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention has the following configuration. (1) A hollow fiber membrane bundle consisting of a plurality of hollow fiber membranes, a cylindrical case for accommodating the hollow fiber membrane bundle, and a first adhesive for bundling one end of the hollow fiber membrane bundle and closing the end of the hollow fiber membrane bundle. Focusinga first adhesive bundling section having a plurality of through holes extending in the axial direction of the hollow fiber membrane bundle, and a second adhesive bundling section which adhesively bundles the other end of the hollow fiber membrane bundle and opens the end of the hollow fiber membrane bundle, wherein the ratio of the diameter of the through holes to the inner diameter of the cylindrical case is 0.02 or more and 0.1 or less, the ratio of the total cross-sectional area of ​​the through holes to the inner cross-sectional area of ​​the cylindrical case (through-hole opening rate) is 5% or more and 20% or less, and the ratio of the total cross-sectional area of ​​the outer diameter of the hollow fiber membranes to the inner cross-sectional area of ​​the cylindrical case (membrane filling rate) is 30% or more and 60% or less. a hollow fiber membrane module used in an external pressure cross-flow filtration method in which a fluid to be treated passes through the through-holes provided in the first adhesive focusing section housed in the cylindrical case, flows between the hollow fiber membrane bundles, and is separated into a permeated fluid and a concentrated fluid by being partially filtered, wherein the through-holes are composed of a first flow path from an inlet through which the fluid to be treated is introduced to a depth H, and a second flow path from the most downstream part of the first flow path to an outlet of the through-holes, the first flow path being coaxial with the second flow path, and the diameter of the first flow path narrows from the inlet through which the fluid to be treated is introduced to the second flow path. (2) The hollow fiber membrane module according to (1) above, characterized in that the diameter is reduced at a constant gradient. (3) The hollow fiber membrane module according to (2) above, characterized in that in the first flow path, the ratio H / D2 of the depth H of the first flow path to the inlet diameter D2 of the second flow path is 0.25 or more, and the gradient of the first flow path is 10° or more and 45° or less with respect to the direction of travel of the fluid to be treated. (4) The hollow fiber membrane module according to (1) above, characterized in that the diameter is reduced by corner rounding. (5) The hollow fiber membrane module according to (4) above, characterized in that in the first flow path, the radius of the corner R of the first flow path is equal to the depth H of the first flow path, and the ratio H / D2 of the depth H of the first flow path to the inlet diameter D2 of the second flow path is 0.25 or more. (6) A method for operating a hollow fiber membrane module used in an external pressure cross-flow filtration system according to any one of (1) to (5) above, characterized in that the membrane surface linear velocity of the fluid to be treated between the hollow fiber membrane bundles is 1.0 m / s or more. (7) A method for producing a hollow fiber membrane module according to any one of (1) to (5) above, a multi-stage through-hole forming jig having at least two regions: a first region having the same shape as the first flow path of the through-hole; and a second region having the same shape as the second flow path and continuous with the first region; The end of the hollow fiber membrane bundle consisting of a plurality of hollow fiber membranes In this state, the end of the hollow fiber membrane bundle is fixed with an adhesive resin. The adhesive is focused Then, the through-hole forming jig is removed, The aforementioned No. 1 A method for producing a hollow fiber membrane module, wherein the through-holes are formed simultaneously with forming the adhesive bundle portion. [Effects of the Invention]

[0008] According to the present invention, by dividing the through-holes provided in the bonded and gathered section of the hollow fiber membrane module into coaxial first and second flow paths and reducing the diameter of the first flow path, it is possible to reduce the pressure loss occurring in the through-holes and form a through-hole structure easily without damaging the membranes. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view showing one embodiment of a hollow fiber membrane module according to the present invention. [Figure 2] FIG. 1 is a schematic cross-sectional view showing one embodiment of a fluid flow during filtration operation using a hollow fiber membrane module according to the present invention. [Figure 3] FIG. 10 is a schematic cross-sectional view showing the state of separated flow around the through-hole when a fluid to be treated is supplied, which is used in the conventional invention. [Figure 4] 1 is a schematic cross-sectional view showing an example of a through-hole according to the present invention and the flow of a fluid to be treated. [Figure 5] 1 is a schematic cross-sectional view showing an example of a through-hole according to the present invention and the flow of a fluid to be treated. [Figure 6] 1 is a schematic cross-sectional view showing an example of a through-hole according to the present invention and the flow of a fluid to be treated. [Figure 7] Schematic diagram showing an example of the shape and arrangement of through holes according to the present invention. [Figure 8]Schematic cross-sectional view showing an example of a method for forming a through hole according to the present invention. [Figure 9] Schematic cross-sectional view showing an example of a method for forming a through hole according to the present invention. [Figure 10] A diagram showing the relationship between the through-hole shape and the pressure loss of the hollow fiber membrane module when a constant gradient θ is provided in the first flow path. [Figure 11] A diagram showing the relationship between the through-hole shape and the pressure loss of the hollow fiber membrane module when a corner R is provided in the first flow path. [Figure 12] A diagram showing the relationship between the membrane surface linear velocity of the fluid to be treated and the pressure drop of the hollow fiber membrane module. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described below with reference to the drawings, taking as an example a hollow fiber membrane module applied to an external pressure crossflow filtration device in which the fluid to be treated is liquid or gas.

[0011] FIG. 1 is a schematic cross-sectional view showing one embodiment of a hollow fiber membrane module according to the present invention. This hollow fiber membrane module comprises a cylindrical case 1, caps 2a and 2b, a hollow fiber membrane bundle 6, a first adhesive bundling section 7a, and a second adhesive bundling section 7b. The hollow fiber membrane bundle 6, which is composed of several hundred to several tens of thousands of hollow fiber membranes aligned to a fixed length and bundled together, is housed and fixed in the cylindrical case 1, together with the first adhesive bundling section 7a and the second adhesive bundling section 7b, whose both ends are adhesively bundled with an adhesive resin. On the side of the first adhesive bundling section 7a, the hollow fiber membranes of the hollow fiber membrane bundle 6 are adhesively bundled with the adhesive resin, and the end faces of the hollow fiber membranes are enclosed within the first adhesive bundling section 7a and are therefore sealed. In the second adhesive / gathering section 7b, only the hollow fiber membranes are bonded and bundled with adhesive resin, while the end faces of the hollow fiber membranes are open at the downstream end face 9b of the second adhesive / gathering section 7b. The area of ​​the hollow fiber membrane bundle 6 not bonded and bundled with adhesive resin between the downstream end face 8b of the first adhesive / gathering section 7a and the upstream end face 9a of the second adhesive / gathering section 7b constitutes the effective filtration area. A plurality of through-holes 10 are provided between the hollow fiber membranes in the first adhesive / gathering section 7a, penetrating in the axial direction of the hollow fiber membrane module (the Y-axis direction in the figure) from the upstream end face 8a to the downstream end face 8b. Caps 2a and 2b are attached to the ends of the cylindrical case 1. A treated fluid inlet 3 is provided in cap 2a, and a permeated fluid outlet 5 is provided in cap 2b. The cylindrical case 1 is also provided with a concentrated fluid outlet 4.

[0012] FIG. 2 shows, with arrows A, B, C, and D, one embodiment of the fluid flow when a liquid to be treated is filtered by an external pressure cross-flow filtration method using the hollow fiber membrane module of the present invention.

[0013] First, the treated fluid is supplied into the hollow fiber membrane module through the treated fluid supply port 3 in the cap 2a (arrow A). The supplied treated fluid passes through the multiple through-holes 10 in the first adhesive-and-concentrating section 7a and flows into the effective filtration region (arrow B). As the treated fluid flows downstream (in the Y-axis direction in the figure), suspended solids are removed from a portion of the treated fluid at the outer periphery of the membrane, and the portion penetrates into the hollow fiber membrane. The permeated fluid, from which suspended solids have been removed, flows through the hollow fiber membrane in the Y-axis direction and is collected in the cap 2b at the downstream end face 9b of the second adhesive-and-concentrating section 7b, where the hollow fiber membrane ends are open, and is then removed from the permeated fluid outlet 5 (arrow C). The concentrated fluid, which does not permeate the hollow fiber membrane and has an increased concentration of suspended solids, is discharged from the concentrated fluid outlet 4 (arrow D).

[0014] The materials for the cylindrical case 1 and the caps 2a, 2b can be selected as desired, taking into consideration the application and conditions of use of the hollow fiber membrane module. When chemical resistance, light weight, and reduced raw material and processing costs during mass production are required, resin products such as polyvinyl chloride resin, acrylic resin, and polysulfone resin are preferred. On the other hand, when heat resistance, pressure resistance, and durability are required, metal products such as stainless steel and aluminum are preferred.

[0015] The size of the cylindrical case 1 can be selected as desired depending on the intended use and operating conditions. The inner diameter of the cylindrical case 1 is preferably in the range of 70 to 210 mm. This is because this size allows for a large effective membrane area per hollow fiber membrane module while also allowing for relatively easy installation and replacement of the hollow fiber membrane module in the filtration device. Furthermore, for crossflow filtration of highly viscous treated fluids, such as those used in food and beverages, the length of the cylindrical case 1 is preferably 1000 to 1500 mm. This is because if the hollow fiber membrane module is too short, the effective membrane area will be small, and if it is too long, a difference in filtration flow rate will occur due to the pressure difference between the upstream and downstream sides of the hollow fiber membrane bundle 6, resulting in a decrease in filtration flux.

[0016] It is preferable to use a polymeric material such as epoxy resin, urethane resin, or epoxy acrylate resin as the adhesive resin for forming the first adhesive bundling portion 7a and the second adhesive bundling portion 7b, which is a general-purpose product, inexpensive, and has excellent corrosion resistance and chemical resistance.

[0017] There are no particular limitations on the material of the hollow fiber membranes that make up the hollow fiber membrane bundle 6, and any material can be selected depending on the application and conditions of use. Examples of such materials include polysulfone, polyethersulfone, polyacrylonitrile, polyimide, polyetherimide, polyamide, polyethylene, polypropylene, cellulose, cellulose acetate, polyvinylidene fluoride, and composite materials thereof.

[0018] The size of the hollow fiber membrane can be selected arbitrarily depending on the intended use and operating conditions, but the outer diameter is preferably in the range of 0.3 to 3 mm. This is because if the outer diameter of the hollow fiber membrane is too small, problems such as the hollow fiber membrane breaking and being damaged when handling the hollow fiber membrane during the fabrication of the hollow fiber membrane module or during filtration and cleaning operations can occur. Conversely, if the outer diameter is too large, problems such as a reduction in the number of hollow fiber membranes that can be inserted into a cylindrical case 1 of the same size can occur, resulting in a reduced filtration area. Furthermore, the membrane thickness of the hollow fiber membrane is preferably in the range of 0.1 to 1 mm. This is because if the membrane thickness is too small, problems such as the membrane being crushed by external pressure during operation can occur, while if the membrane thickness is too large, problems such as a reduced filtration flux and increased raw material costs can occur. Furthermore, when the membrane filling rate is defined as the proportion of hollow fiber membranes in the cylindrical case 1, the membrane filling rate is 30% to 60%. This is because if the membrane packing rate is too low, the effective membrane area decreases, causing problems such as reduced filtration performance, while if the membrane packing rate is too high, it becomes difficult to insert the hollow fiber membrane bundle 6 into the cylindrical case 1, and the flow resistance of the treated fluid increases, leading to increased pressure loss. The membrane packing rate is expressed by the following equation:

[0019] A2 / A1 x 100(%) A1: Cross-sectional area with the inner diameter of the cylindrical case 1 as the diameter A2: Sum of cross-sectional areas with the outer diameter of the hollow fiber membrane as the diameter When the ratio of the total cross-sectional area of ​​the through holes 10 to the inner diameter cross-sectional area of ​​the cylindrical case 1 is defined as the aperture ratio, the aperture ratio is within the range of 5% to 20%. This is because if the aperture ratio is too large, the hollow fiber membranes in the first adhesive and gathering section 7a will be crowded together, which may result in poor adhesion between the hollow fiber membranes or problems such as retention of the fluid to be treated near the downstream end face 8b. Conversely, if the aperture ratio is too small, the distance between adjacent through holes 10 will be large, which may result in retention of the fluid to be treated near the downstream end face 8b of the first adhesive and gathering section 7a. The aperture ratio is expressed by the following equation.

[0020] A3 / A1 x 100(%) A1: Cross-sectional area with the inner diameter of the cylindrical case 1 as the diameter A3: Sum of cross-sectional areas of the through-holes 10 with the outlet diameter D3 as the diameter The size of the through-holes 10 can be selected arbitrarily depending on the intended use and operating conditions. The ratio of the diameter of the through-holes 10 to the inner diameter of the cylindrical case 1 is in the range of 0.02 to 0.1. This is because if the outlet diameter D3 of the through-holes 10 is too small relative to the inner diameter of the cylindrical case 1, suspended matter contained in the treated fluid may clog the through-holes 10, or the pressure loss of the hollow fiber membrane module during filtration may increase, resulting in increased operating costs. While the pressure loss can be reduced by increasing the number of through-holes 10 and the aperture ratio, this can lead to manufacturing problems, such as an increase in the number of processing steps. Furthermore, if the outlet diameter D3 of the through-holes 10 is too large relative to the inner diameter of the cylindrical case 1, when the aperture ratio of the through-holes 10 is within a certain range, as described above, the number of through-holes 10 decreases, the spacing between the through-holes 10 increases, and problems such as an increase in retention areas arise. Figure 3 shows a schematic cross-sectional view of the separated flow around the through-holes 10 when a treated fluid is supplied in a conventional invention. The treated fluid supplied into the cap 2a from the treated fluid supply port 3 passes through each through-hole 10 and flows into the hollow fiber membrane bundle 6. However, downstream of the first corner 12a of the through-hole 10, the flow path suddenly narrows, causing a rapid decrease in the cross-sectional area of ​​the treated fluid. The treated fluid cannot follow this flow, causing boundary layer separation and generating vortices. The treated fluid then flows along the wall surface of the through-hole 10 and passes through the through-hole 10. This is particularly noticeable when filtration is performed at a high membrane surface linear velocity using an external pressure cross-flow filtration method. In the present invention, a means is provided for suppressing boundary layer separation of the fluid to be treated that occurs at the first corner portion 12a of the through-hole 10 and reducing pressure loss. Figure 4 shows a schematic cross-sectional view of an example of a through-hole according to the present invention, illustrating the flow of a fluid to be treated. The through-hole 10 includes a first flow path 11a extending from the inlet where the fluid to be treated is introduced to a depth H, and a second flow path 11b extending from the most downstream portion of the first flow path 11a to the outlet of the through-hole 10. The first flow path 11a and the second flow path 11b are coaxial. The diameter of the first flow path 11a narrows between the inlet where the fluid to be treated is introduced and the second flow path 11b. This prevents a rapid transition in the cross-sectional area of ​​the fluid to be treated, suppresses boundary layer separation of the fluid to be treated at the first corner 12a of the through-hole 10, and reduces pressure loss. This is particularly effective for hollow fiber membrane modules for food and beverage applications, where the fluid to be treated is operated at a high membrane surface linear velocity and has a high viscosity. For example, in order to suppress the deposition of suspended solids, it is preferable to operate the filtration of a fermented malt beverage concentrate at a high membrane surface linear velocity of 1.0 m / s or higher, and since the pressure loss occurring in the hollow fiber membrane module formed by the through holes 10 of the conventional invention shown in Figure 3 is greater than when operated at a membrane surface linear velocity of 1.0 m / s or less, the present invention can effectively reduce the pressure loss. Furthermore, since the pressure loss occurring in the hollow fiber membrane module tends to increase with increasing viscosity, the present invention can effectively reduce the pressure loss even when a highly viscous fluid to be treated is operated for filtration using an external pressure crossflow filtration method. 4, the diameter of first flow path 11a formed in through hole 10 of the present invention is reduced at a constant gradient θ. Since first flow path 11a is reduced in diameter from the inlet where the fluid to be treated is introduced to second flow path 11b, boundary layer separation occurring at first corner 12a of through hole 10 is suppressed, and the fluid flows along the wall surface of first flow path 11a, thereby reducing pressure loss in through hole 10. In this case, when the depth of first flow path 11a of through hole 10 is H and the inlet diameter of second flow path 11b is D2, the ratio H / D2 is preferably 0.25 or greater, and more preferably 0.5 or greater. This is because a larger depth H of first flow path 11a relative to inlet diameter D2 of second flow path 11b allows for a gradual transition in the flow path cross-sectional area of ​​the fluid to be treated, and effectively suppresses boundary layer separation that occurs at first corner 12a or second corner 12b of through hole 10. Furthermore, the magnitude of gradient θ of first flow path 11a is preferably in the range of 10 to 45° with respect to the traveling direction of the fluid to be treated, i.e., the axial direction of through hole 10. This is because if gradient θ of first flow path 11a is smaller than 10°, the flow path cross-sectional area decreases rapidly from the inlet of through hole 10 to first flow path 11a, causing boundary layer separation at first corner 12a and reducing the effect of reducing pressure loss. Furthermore, when the gradient θ of first flow path 11a is greater than 45°, the aforementioned abrupt decrease in the flow path cross-sectional area from the inlet of through hole 10 to first flow path 11a is mitigated, and boundary layer separation at first corner 12a is suppressed, but the flow path cross-sectional area decreases abruptly from first flow path 11a to second flow path 11b, causing boundary layer separation at second corner 12b and reducing the effect of reducing pressure loss. Further, other means for suppressing boundary layer separation of the treated fluid occurring at first corner 12a of through hole 10 and reducing pressure loss will be described in detail using schematic cross-sectional views of an example of a through hole according to the present invention and the flow of the treated fluid in Figures 5 and 6.

[0021] In the embodiment shown in FIG. 5, the first flow path 11a of the through hole 10 is tapered at a corner R with a constant curvature, where the radius of curvature is equal to the depth H of the first flow path 11a. Boundary layer separation that occurs at the first corner 12a of the through hole 10 is suppressed, and the flow follows the wall surface of the through hole 10, thereby reducing pressure loss in the through hole 10. In this case, it is preferable to set the ratio H / D2, where H is the depth of the first flow path 11a and D2 is the inlet diameter of the second flow path 11b, to 0.25 or greater. This is because, similar to the case where the first flow path 11a is tapered at a constant gradient, a larger depth H of the first flow path 11a relative to the inlet diameter D2 of the second flow path 11b allows for a more gradual transition in the flow path cross-sectional area of ​​the treated fluid, thereby effectively suppressing boundary layer separation that occurs at the first corner 12a or the second corner 12b of the through hole 10. Furthermore, the corner R does not necessarily have to be reduced in diameter at a constant curvature, and the first flow path 11a may be formed by a bell-mouth shape with an inconstant curvature, as in the embodiment shown in FIG.

[0022] FIG. 7 is a schematic diagram showing an example of the shape and arrangement of through holes according to the present invention. The cross-sectional shape of the through holes 10 can be any shape, such as circular, elliptical, or polygonal. However, a circular shape is preferred due to the manufacturing process of the through holes 10 using the through-hole forming jig 20 described below. The second flow path 11b can have any shape from the inlet to the outlet of the second flow path 11b. However, it is preferable to narrow the diameter at a gradient of 1 to 2 degrees, depending on the method for forming the through holes 10 described below. The arrangement of the multiple through holes 10 can be any, such as a parallel arrangement at the intersections of a lattice, a 60° staggered arrangement, or a radial arrangement at the intersections of radial lines centered on the center of the first adhesive focusing section 7a and circles centered on the same axis. However, if the spacing between adjacent through holes 10 varies, the treated fluid is likely to stagnate near the downstream end surface 8b of the first adhesive focusing section 7a where the spacing is larger than others, which can lead to reduced membrane utilization efficiency and the accumulation of suspended solids. Therefore, it is preferable to space the through holes 10 evenly.

[0023] The present invention shows a method for manufacturing a hollow fiber membrane module having through-holes 10 that have the effect of reducing pressure loss. In a hollow fiber membrane module, hollow fiber membranes are inserted at a high packing ratio to maximize membrane utilization efficiency, and many hollow fiber membranes are present around the through-holes 10. It is not easy to form the first flow path 11a and the second flow path 11b by post-processing such as cutting while avoiding damaging these membranes. Therefore, the ends of the hollow fiber membrane bundle 6 are adhesively bundled to form the first adhesive bundle portion 7a, and the through-holes 10 are formed at the same time.

[0024] FIG. 8 shows a schematic cross-sectional view illustrating an example of a method for forming a through hole according to the present invention, illustrating a method for manufacturing a hollow fiber membrane module in which the through hole 10 shown in FIG. 4 is formed. FIG. 9 shows a schematic cross-sectional view illustrating an example of a method for forming a through hole according to the present invention, illustrating a method for manufacturing a hollow fiber membrane module in which the through hole 10 shown in FIG. 5 is formed. A multi-stage through-hole forming jig 20 is used, which has at least two regions: a first region 21a having the same shape as the first flow path 11a of the through hole 10, and a second region 21b having the same shape as the second flow path 11b and continuing from the first region 21a. The jig is positioned in the hollow fiber membrane bundle 6 at the position where the through hole 10 is to be formed before the adhesive resin hardens, so as to push its way through the hollow fiber membrane bundle 6. After the adhesive resin hardens, the jig is removed, thereby easily forming a through hole 10 in the first adhesive gathering section 7a that reduces pressure loss without damaging the hollow fiber membranes. In this case, the through-hole forming jig 20 preferably has a circular cross-sectional shape and a draft angle of 1 to 2° in the second region 21b to facilitate removal after the adhesive resin has hardened. The shape and mounting depth of the through-hole forming jig 20 are adjusted so that the diameter of the through-hole forming jig 20 is D3 at the position corresponding to the outlet of the second flow path 11b of the through-hole 10 formed in the first adhesive focusing section 7a. The material of the through-hole forming jig 20 can be selected arbitrarily depending on the curing conditions of the adhesive resin. However, it is preferable to use low-adhesion polyethylene resin, polytetrafluoroethylene resin, polyacetal resin, or a metal material such as stainless steel plated with Nimflon or Caniflon to facilitate removal after the adhesive resin has hardened. The region of the through-hole forming jig 20 beyond the upstream end face 8a of the first adhesive focusing section 7a but not within the first adhesive focusing section 7a may have any shape as long as it can form a through-hole entrance with diameter D1 at the upstream end face 8a. Furthermore, the region of the through-hole forming jig 20 beyond the downstream end face 8b of the first adhesive concentrating section 7a and within the hollow fiber membrane bundle 6 may have any shape as long as it does not exceed the outlet diameter D3 of the through-hole 10. [Example]

[0025] An example of the present invention will be described in detail below using a hollow fiber membrane module having the configuration shown in Figures 1 and 3 to 5. However, the present invention is not limited to the following example. (Comparative Example 1) In Comparative Example 1, a hollow fiber membrane module having the through-holes 10 of the conventional invention shown in Figure 3 formed in the first adhesive concentrating section 7a of the hollow fiber membrane module shown in Figure 1 was used, and the pressure loss generated in the hollow fiber membrane module was measured. The cylindrical case 1 of the hollow fiber membrane module had an inner diameter of 97.6 mm and a length of 1140 mm. The hollow fiber membranes constituting the hollow fiber membrane bundle 6 were made of polyvinylidene fluoride, and hollow fiber membranes with an outer diameter of 1.3 mm were inserted into the cylindrical case 1 to achieve a packing ratio of 40%. The heights of the first adhesive concentrating section 7a and the second adhesive concentrating section 7b were both 45 mm. 24 through-holes with a diameter of 8 mm were formed in the first adhesive concentrating section 7a in a parallel arrangement with a center-to-center spacing of 16 mm. The ratio of the diameter of the through-holes to the inner diameter of the cylindrical case was 0.08, and the aperture ratio was 16%. The operating conditions were as follows: water at a temperature of 20°C was used as the treated fluid, and the supply flow rate of the treated fluid was adjusted so that the membrane surface linear velocity was 1.5 m / s. At this time, the permeate fluid outlet 4 was sealed and no filtration was performed, and the entire amount of the treated fluid supplied was discharged from the concentrated fluid outlet 6. Pressure gauges (KEYENCE: GP-M010) were installed at one point on the pipe connected to the treated fluid inlet 3 and one point on the pipe connected to the concentrated fluid outlet 6, and the pressure loss occurring in the hollow fiber membrane module was calculated from the difference in the measured pressures. The pressure loss occurring in the hollow fiber membrane module of Comparative Example 1 was 102 kPa. These results are shown in the graphs of Figures 10 and 11. Example 1 In Example 1, all through-holes 10 had the shape shown in FIG. 4 , and the inlet diameter D2 of the second flow path 11b and the outlet diameter D3 of the through-hole 10 were 8 mm. The ratio of the diameter of the through-hole to the inner diameter of the cylindrical case was 0.08, and the aperture ratio was 16%. Pressure loss measurements were performed under the same hollow fiber membrane module structure and operating conditions as in Comparative Example 1, except that the slope θ of the first flow path 11a was fixed at 5° and the depth H of the first flow path 11a was set to 2 mm, 4 mm, and 8 mm, resulting in three conditions (three hollow fiber membrane modules) where H / D2 was 0.25, 0.5, and 1.0. The pressure losses generated in the hollow fiber membrane modules were 96.4 kPa, 93.7 kPa, and 90.8 kPa, respectively. The results are shown in the graph of FIG. 10 as plots and the lines connecting the plots. It can be seen that the pressure loss was reduced compared to the results of Comparative Example 1 (where H / D2 = 0). Example 2 In Example 2, pressure loss measurements were performed using the same hollow fiber membrane module structure and operating conditions as in Example 1, except that the gradient θ of the first flow path 11a was set to 10°. The pressure losses generated in the hollow fiber membrane module were 92.7 kPa, 90.2 kPa, and 87.9 kPa, respectively. The results are shown in the graph of Figure 10 as plots and the broken lines connecting the plots. It can be seen that the pressure loss was reduced compared to the results of Comparative Example 1 (results where H / D2 = 0), and that the pressure loss reduction effect was particularly large in the range of H / D2 ≥ 0.25. Example 3 In Example 3, pressure loss measurements were performed using the same hollow fiber membrane module structure and operating conditions as in Example 1, except that the gradient θ of the first flow path 11a was set to 30°. The pressure losses generated in the hollow fiber membrane module were 87.9 kPa, 86.7 kPa, and 86.2 kPa, respectively. The results are shown in the graph of FIG. 10 as plots and the lines connecting the plots. It can be seen that the pressure loss was reduced compared to the results of Comparative Example 1 (results of H / D2 = 0). The pressure loss reduction effect was particularly significant in the range of H / D2 ≧ 0.25, with a maximum pressure loss reduction of 15%. Example 4 In Example 4, pressure loss measurements were performed using the same hollow fiber membrane module structure and operating conditions as in Example 1, except that the gradient θ of the first flow path 11a was set to 45°. The pressure losses generated in the hollow fiber membrane module were 90.8 kPa, 89.4 kPa, and 89.1 kPa, respectively. The results are shown in the graph of Figure 10 as plots and the broken lines connecting the plots. It can be seen that the pressure loss was reduced compared to the results of Comparative Example 1 (results where H / D2 = 0), and the pressure loss reduction effect was particularly large in the range of H / D2 ≥ 0.25. Example 5 In Example 5, pressure loss measurements were performed using the same hollow fiber membrane module structure and operating conditions as in Example 1, except that the gradient θ of the first flow path 11a was set to 60°. The pressure losses generated in the hollow fiber membrane module were 92.9 kPa, 92.9 kPa, and 92.7 kPa, respectively. The results are shown in the graph of Figure 10 as plots and the broken lines connecting the plots. It can be seen that the pressure loss was reduced compared to the results of Comparative Example 1 (results where H / D2 = 0). Example 6 In Example 6, all through-holes 10 had the shape shown in FIG. 5 , and the inlet diameter D2 of second flow path 11b and the outlet diameter D3 of through-hole 10 were 8 mm. The ratio of the diameter of the through-hole to the inner diameter of the cylindrical case was 0.08, and the aperture ratio was 16%. Pressure loss measurements were performed under the same hollow fiber membrane module structure and operating conditions as in Comparative Example 1, except that the depth H of first flow path 11a was set to 0.5 mm, 2 mm, 4 mm, and 8 mm, resulting in four conditions (four hollow fiber membrane modules) with H / D2 ratios of 0.0625, 0.25, 0.5, and 1.0. The pressure losses in the hollow fiber membrane modules were 88.9 kPa, 86.0 kPa, 85.6 kPa, and 85.4 kPa, respectively. The results are shown in FIG. 11 as plots and the lines connecting the plots. It can be seen that the pressure loss was reduced compared to the results of Comparative Example 1 (results when H / D2 = 0), and the pressure loss reduction effect was particularly large in the range of H / D2 ≧ 0.25, with a maximum pressure loss reduction of 16%. (Comparative Example 2) In Comparative Example 2, pressure drop measurements were performed using the same hollow fiber membrane module structure and operating conditions as in Comparative Example 1, except that the membrane surface linear velocity was set to 0.5 m / s, 1.0 m / s, 1.5 m / s, and 2.0 m / s. The pressure drops generated in the hollow fiber membrane module were 19 kPa, 53 kPa, 102 kPa, and 168 kPa, respectively. The results are shown in the graph of Figure 12 as plots and the broken lines connecting the plots. Example 7 In Example 7, all through-holes 10 had the shape shown in FIG. 4 , and the inlet diameter D2 of second flow path 11b and the outlet diameter D3 of through-hole 10 were 8 mm. The ratio of the diameter of the through-hole to the inner diameter of the cylindrical case was 0.08, and the aperture ratio was 16%. Pressure loss measurements were performed under the same hollow fiber membrane module structure and operating conditions as in Comparative Example 2, except that the gradient θ of first flow path 11a was fixed at 30° and the depth H of first flow path 11a was 8 mm, resulting in an H / D2 ratio of 1.0. The pressure losses in the hollow fiber membrane module were 17.4 kPa, 46.3 kPa, 86.2 kPa, and 140.8 kPa for membrane surface linear velocities of 0.5 m / s, 1.0 m / s, 1.5 m / s, and 2.0 m / s, respectively. The results are shown in the graph of FIG. 12 as plots and the broken lines connecting the plots. It can be seen that the pressure loss was reduced under all conditions compared to the results of Comparative Example 2 (results when H / D2 = 0). Furthermore, as the membrane surface linear velocity increased, the reduction rates of pressure loss also increased to 8.3%, 12.7%, 15.5%, and 16.2%, respectively, demonstrating that the pressure loss occurring in the hollow fiber membrane module in particular was effectively reduced when the membrane surface linear velocity was 1.0 m / s or higher. [Explanation of symbols]

[0026] 1 cylindrical case 2a, 2b cap 3. Treated fluid supply port 4 Concentrated fluid outlet 5 Permeate outlet 6 Hollow fiber membrane bundle 7a 1st adhesive convergence part 7b Second adhesive convergence part 8a, 8b: upstream end surface and downstream end surface of the first adhesive concentrating portion 7a 9a, 9b: upstream end surface and downstream end surface of the second adhesive concentrating portion 7b 10 through holes 11a, 11b: first flow path and second flow path of through-hole 10 12a, 12b: first corner and second corner of the through hole 10 20 Through-hole forming jig 21a, 21b: first region and second region of the through-hole forming jig 20 H Depth of the first flow path 11a D1 entrance diameter of through hole 10 D2: Inlet diameter of second flow path 11b D3 Exit diameter of through hole 10 θ Gradient of first flow path 11a

Claims

1. a hollow fiber membrane bundle consisting of a plurality of hollow fiber membranes, a cylindrical case accommodating the hollow fiber membrane bundle, a first adhesive bundling section that adhesively bundles one end of the hollow fiber membrane bundle and closes the end of the hollow fiber membrane bundle, a plurality of through holes provided in the first adhesive bundling section and extending in the axial direction of the hollow fiber membrane bundle, and a second adhesive bundling section that adhesively bundles the other end of the hollow fiber membrane bundle and opens the end of the hollow fiber membrane bundle, wherein the ratio of the diameter of the through holes to the inner diameter of the cylindrical case is 0.02 or more and 0.1 or less, the ratio of the total cross-sectional area of ​​the through holes to the inner cross-sectional area of ​​the cylindrical case (opening rate of the through holes) is 5% or more and 20% or less, and the ratio of the total cross-sectional area of ​​the outer diameter of the hollow fiber membranes to the inner cross-sectional area of ​​the cylindrical case (membrane filling rate) is 0.02 or more and 0.1 or less. a hollow fiber membrane module used in an external pressure cross-flow filtration system in which a fluid to be treated supplied from a fluid to be treated supply section of the cylindrical case passes through the through-holes provided in the first adhesive focusing section housed in the cylindrical case, flows between the hollow fiber membrane bundles, and is separated into a permeated fluid and a concentrated fluid by being partially filtered, the hollow fiber membrane module being characterized in that the through-holes are composed of a first flow path from an inlet through which the fluid to be treated is introduced to a depth H, and a second flow path from a most downstream part of the first flow path to an outlet of the through-holes, the first flow path being coaxial with the second flow path, and the first flow path narrows in diameter from the inlet through which the fluid to be treated is introduced to the second flow path.

2. 2. The hollow fiber membrane module according to claim 1, wherein the diameter is reduced at a constant gradient.

3. 3. The hollow fiber membrane module according to claim 2, wherein in the first flow path, a ratio H / D2 of a depth H of the first flow path to an inlet diameter D2 of the second flow path is 0.25 or more, and a gradient of the first flow path is 10° or more and 45° or less with respect to a traveling direction of the fluid to be treated.

4. 2. The hollow fiber membrane module according to claim 1, wherein the diameter is reduced by rounding the corners.

5. 5. The hollow fiber membrane module according to claim 4, wherein in the first flow path, a radius of a corner R of the first flow path is equal to a depth H of the first flow path, and a ratio H / D2 of the depth H of the first flow path to an inlet diameter D2 of the second flow path is 0.25 or more.

6. A method for operating a hollow fiber membrane module used in an external pressure cross-flow filtration system according to any one of claims 1 to 5, characterized in that the membrane surface linear velocity of the fluid to be treated between the hollow fiber membrane bundles is 1.0 m / s or more.

7. 6. A method for producing a hollow fiber membrane module according to claim 1, wherein a multi-stage through-hole forming jig having at least two regions, namely, a first region having the same shape as the first flow path of the through-hole and a second region having the same shape as the second flow path and continuous with the first region, is placed at an end of the hollow fiber membrane bundle consisting of a plurality of hollow fiber membranes, and the end of the hollow fiber membrane bundle is adhesively bundled using an adhesive resin, and then the through-hole forming jig is removed, thereby forming the first adhesive bundle region and forming the through-hole at the same time.

Images