Hollow fiber membrane module

Abstract

To provide a hollow fiber membrane module capable of suppressing tangling, damage and the like of a hollow fiber membrane while effectively removing a floating pollutant stuck on the surface of the hollow fiber membrane in a bubbling step.SOLUTION: A hollow fiber membrane module 10 comprises: a housing 13 where a fixing member 3 is fixed inside and an internal space S1 is formed; a plurality of hollow fiber membrane bundles 15 which has a plurality of hollow fiber membranes 14 respectively and which is arranged in the internal space S1 in a state that the upper edge 14B of the hollow fiber membrane 14 is fixed to the fixing member 3; a gas supply part 2 supplying a gas to clean the hollow fiber membrane bundle 15 into the internal space S1; and a suppression member 100 individually arranged at the respective plurality of hollow fiber membrane bundles 15. The suppression member 100 suppresses the splashing of the lower edges 14A of the plurality of hollow fiber membranes 14 while allowing the oscillation of the plurality of hollow fiber membranes 14 by the gas supplied into the internal space S1 from the gas supply part 2 in the corresponding hollow fiber membrane bundle 15.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a hollow fiber membrane module including a plurality of hollow fiber membranes.

Background Art

[0002] Conventionally, in water treatment for removing impurities in water, a hollow fiber membrane module having a bundle of a plurality of hollow fiber membranes has been used. In the filtration step of water treatment, raw water (water before filtration) is supplied into the module through a raw water inlet provided in the hollow fiber membrane module, and the filtered water that has passed through the membrane is discharged outside the module through a filtered water outlet provided in the module.

[0003] In the hollow fiber membrane module, when the filtration step of water treatment is performed, substances removed from the water (suspended contaminants (SS: Suspended Solids)) accumulate on the membrane surface. Thus, efficiently removing the suspended contaminants deposited on the membrane surface is one of the important issues.

[0004] Generally, the removal of suspended contaminants is performed by so-called backwashing (backpressure washing). In the backwashing step, in order to float the suspended contaminants attached to the membrane surface from the membrane, a fluid flow in the opposite direction to the filtration step is formed in the module. That is, a fluid such as gas or liquid is supplied into the module through the filtered water outlet, and the fluid that has passed through the membrane from the inside to the outside is discharged outside the module through the raw water inlet.

[0005] In this way, the suspended contaminants that have become partially floating from the membrane surface by performing the backwashing step are then peeled off from the membrane surface by performing the bubbling step. In this bubbling step, washing gas is supplied in a state where the module is filled with water, and the membrane is shaken by the bubbles of the supplied washing gas, so that the suspended contaminants on the membrane surface are peeled off.

[0006] In the bubbling process, in order to more effectively remove the floating contaminants deposited on the membrane surface, it is necessary to strongly oscillate the hollow fiber membrane. On the other hand, if excessive oscillation occurs, abrasion due to contact between the hollow fiber membranes, breakage near the fixed part of the hollow fiber membrane, entanglement between the hollow fiber membranes, etc. will occur, making stable operation difficult. Patent Document 1 below discloses a hollow fiber membrane module having a configuration for moderately oscillating the hollow fiber membrane in the bubbling process.

[0007] In the hollow fiber membrane module of Patent Document 1 below, a net-like object is provided so as to cover the entire hollow fiber membrane bundle in which a plurality of hollow fiber membranes are fixed in a bundle at the upper end.

Prior Art Document

Patent Document

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] In the above Patent Document 1, all the hollow fiber membranes constituting the hollow fiber membrane module are bundled as one hollow fiber membrane bundle, and the entire one hollow fiber membrane bundle is covered with a net-like object. In this case, since the oscillation of all the hollow fiber membranes is regulated by the same net-like object in the bubbling process, the floating contaminants attached to the membrane surface cannot be effectively removed. Further, in the structure in which the entire hollow fiber membrane bundle is covered with a net-like object, there is a risk that the lower end of the hollow fiber membrane will enter the mesh of the net-like object by oscillating in the bubbling process. In this case, problems such as entanglement between the hollow fiber membrane and the net-like object and damage to the hollow fiber membrane will occur.

[0010] The present invention has been made in view of the above problems, and an object thereof is to provide a hollow fiber membrane module capable of effectively removing floating contaminants attached to the membrane surface of the hollow fiber membrane in the bubbling process while suppressing entanglement and damage of the hollow fiber membrane.

Means for Solving the Problem

[0011] A hollow fiber membrane module according to an aspect of the present invention includes a housing in which a fixing member is fixed inside and which forms an internal space, a plurality of hollow fiber membrane bundles each having a plurality of hollow fiber membranes, and the upper ends of the plurality of hollow fiber membranes are fixed to the fixing member and are arranged in the internal space, a gas supply unit that supplies a gas for cleaning the plurality of hollow fiber membrane bundles into the internal space, and a restraining member provided individually for each of the plurality of hollow fiber membrane bundles. Each of the restraining members is, with the upper end the fixing member being separated from fixed to the side surface of the housing, and in the corresponding hollow fiber membrane bundle, it is configured to allow the plurality of hollow fiber membranes to swing by the gas supplied into the internal space from the gas supply unit, while suppressing the lower ends of the plurality of hollow fiber membranes from rising.

[0012] According to this hollow fiber membrane module, the hollow fiber membranes constituting the hollow fiber membrane module are divided into a plurality of hollow fiber membrane bundles with their upper ends fixed to the fixing member, and a restraining member is provided individually for each of the plurality of hollow fiber membrane bundles. As a result, each hollow fiber membrane bundle is in a state independent of each other by the restraining member. For this reason, in the bubbling process according to the supply of the cleaning gas by the gas supply unit, the plurality of hollow fiber membranes swing within the hollow fiber membrane bundles in a state independent of each other. Thereby, the floating contaminants attached to the membrane surface are peeled off. At this time, since each hollow fiber membrane bundle is in a state independent of each other by the restraining member, the floating contaminants peeled off from the membrane surfaces of the plurality of hollow fiber membranes within each hollow fiber membrane bundle can be discharged through the spaces between the hollow fiber membrane bundles. Thereby, the floating contaminants attached to the membrane surface of the hollow fiber membrane within each hollow fiber membrane bundle can be effectively removed. Moreover, since each hollow fiber membrane bundle is in a state independent of each other by the restraining member, the interference between the hollow fiber membranes belonging to different hollow fiber membrane bundles is suppressed. Thereby, it is possible to suppress the entanglement of the hollow fiber membranes between the hollow fiber membrane bundles and to suppress the accompanying damage to the hollow fiber membranes.

[0013] Further, the restraining member that keeps each hollow fiber membrane bundle in an independent state is configured to allow a plurality of hollow fiber membranes to swing within the hollow fiber membrane bundle while suppressing the upward movement of the lower ends of the plurality of hollow fiber membranes. In this way, by suppressing the upward movement of the lower ends of the plurality of hollow fiber membranes within the hollow fiber membrane bundle, excessive movement of the plurality of hollow fiber membranes within the hollow fiber membrane bundle is restricted. For this reason, it is possible to suppress excessive interference between the hollow fiber membranes, such as entanglement between the hollow fiber membranes belonging to the same hollow fiber membrane bundle, and to suppress damage to the hollow fiber membranes associated therewith.

[0014] In the above hollow fiber membrane module, each of the restraining members may be constituted by a net-like body having a plurality of meshes and extending in the vertical direction so as to cover the side surface of the corresponding hollow fiber membrane bundle. In this case, the lower end of each of the restraining members is positioned at a position where it can suppress the upward movement of the lower ends of the plurality of hollow fiber membranes that swing within the corresponding hollow fiber membrane bundle, and can also suppress the lower ends of the plurality of hollow fiber membranes from entering the meshes.

[0015] In this aspect, the lower end of the restraining member constituted by the net-like body that covers the side surface of the hollow fiber membrane bundle is positioned at a position where it can suppress the upward movement of the lower ends of the plurality of hollow fiber membranes that swing within the hollow fiber membrane bundle, and can also suppress the lower ends of the plurality of hollow fiber membranes from entering the meshes. By suppressing the upward movement of the lower ends of the plurality of hollow fiber membranes within the hollow fiber membrane bundle, it is possible to suppress the entanglement of the hollow fiber membranes within the hollow fiber membrane bundle. Further, by setting the position of the lower end of the restraining member so as to be able to suppress the lower ends of the hollow fiber membranes from entering the meshes of the restraining member, it is possible to regulate the entanglement of the hollow fiber membranes with the restraining member. Thereby, it is possible to suppress damage to the hollow fiber membranes.

[0016] In the above hollow fiber membrane module, the upper end of each of the restraining members may be fixed to the fixing member, and the vertical length of each of the restraining members may be set to satisfy the following formula (1). 0.7 ≦ L1 / L2 ≦ 1.0 ···(1)

[0017] In the above formula (1), "L1" represents the vertical length of the suppression member, and "L2" represents the effective length of the hollow fiber membrane.

[0018] In this aspect, the vertical length of the suppression member constituted by the net-like body covering the side surface of the hollow fiber membrane bundle is set to satisfy the above formula (1). By setting the length of the suppression member to satisfy the left side "0.7 ≦ L1 / L2" of the above formula (1), the lower end of the suppression member can be positioned at a position where it is possible to suppress the upward movement of the lower ends of the plurality of hollow fiber membranes. On the other hand, by setting the length of the suppression member to satisfy the right side "L1 / L2 ≦ 1.0" of the above formula (1), the lower end of the suppression member can be positioned at a position where it is possible to suppress the lower ends of the plurality of hollow fiber membranes from entering the meshes of the suppression member.

[0019] In the above hollow fiber membrane module, each of the suppression members may have a configuration having a function of partitioning between the plurality of hollow fiber membrane bundles so that a gap is formed therebetween.

[0020] In this aspect, since a gap is formed between each hollow fiber membrane bundle by the suppression member, the floating contaminants peeled off in accordance with the swinging of the plurality of hollow fiber membranes in each hollow fiber membrane bundle in the bubbling process can be discharged through the gap between each hollow fiber membrane bundle. Thereby, the removal effect of the floating contaminants adhering to the membrane surface of the hollow fiber membrane can be further enhanced.

[0021] In the above hollow fiber membrane module, the gas supply part may be arranged at a position below the hollow fiber membrane bundle, have a shape that spreads in the radial direction of the hollow fiber membrane bundle, and include a diffuser member in which a plurality of ventilation holes for gas diffusion are formed at intervals in the radial direction. In this case, the diffuser member has a shape that spreads in the radial direction of the hollow fiber membrane bundle, and includes a plate-shaped main body part in which a plurality of ventilation holes for gas diffusion are formed at intervals in the radial direction, and a cylindrical shape in which one end is connected to the lower surface of the main body part and a gas inlet is formed on the other end side, and a gas receiving part in which dispersion holes for guiding the gas accommodated in the cylinder to the ventilation holes for gas diffusion are formed.

[0022] Further, in the above hollow fiber membrane module, the gas receiving part may have a configuration in which the inner diameter expands from the one end toward the other end.

[0023] Further, in the above hollow fiber membrane module, the ventilation holes for gas diffusion may be arranged on a plurality of circumferences spaced apart in the radial direction in the main body part, and the number of the ventilation holes for gas diffusion on each circumference satisfies being a multiple of the number of the hollow fiber membrane bundles.

Advantages of the Invention

[0024] As described above, according to the present invention, it is possible to provide a hollow fiber membrane module capable of effectively removing floating contaminants attached to the membrane surface of the hollow fiber membrane in the bubbling process while suppressing entanglement and damage of the hollow fiber membrane.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Mode for Carrying Out the Invention

[0026] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

[0027] (First Embodiment) [Filtration Device, Hollow Fiber Membrane Module] First, the configuration of the filtration device 1 including the hollow fiber membrane module 10 according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram showing the configuration of the filtration device 1. FIG. 2 is a schematic diagram showing the configuration of the hollow fiber membrane module 10.

[0028] The filtration device 1 includes an outside pressure filtration type hollow fiber membrane module 10, a liquid feed pump 20, an air compressor 30, pipes connecting these components and on-off valves provided in the pipes, and a control device 40. The hollow fiber membrane module 10 is an outside pressure filtration type module that supplies the stock solution to the outer surface side of the hollow fiber membrane and extracts the filtrate from the inner surface side.

[0029] As shown in FIG. 2, the hollow fiber membrane module 10 includes a housing 13 in which a fixing member 3 is fixed inside and forms an internal space S1, a plurality of hollow fiber membrane bundles 15 arranged in the internal space S1, a water conduit (pipe member) 5 for introducing raw water into the internal space S1, a gas supply unit 2 for supplying a gas (washing gas) for washing the plurality of hollow fiber membrane bundles 15 in the internal space S1, and a restraining member 100 provided individually for each of the plurality of hollow fiber membrane bundles 15.

[0030] Each of the plurality of hollow fiber membrane bundles 15 has a plurality of hollow fiber membranes 14. The upper ends 14B of the plurality of hollow fiber membranes 14 are fixed to the fixing member 3 in an open state, and the lower ends 14A of the plurality of hollow fiber membranes 14 are sealed in a state where they are not fixed one by one, which is a one-end free type. The fixing member 3 converges and fixes the upper ends 14B of the plurality of hollow fiber membranes 14 for each hollow fiber membrane bundle 15. The fixing member 3 liquid-tightly partitions the space in the housing 13 into an internal space S1 on the raw water side and a space S2 on the filtrate side in order for the hollow fiber membrane 14 to function as a filtration membrane. Thermosetting resins such as epoxy resin, unsaturated polyester resin, and polyurethane resin are used for the fixing member 3. As the bonding method between each hollow fiber membrane bundle 15 and the fixing member 3, there are a centrifugal bonding method, a static bonding method, and the like.

[0031] As the material of the hollow fiber membrane 14, various materials can be used and it is not particularly limited. For example, it preferably contains at least one selected from the group consisting of polyethylene, polypropylene, polyacrylonitrile, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, polytetrafluoroethylene, polyvinyl fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, chlorotrifluoroethylene-ethylene copolymer, polyvinylidene fluoride, polysulfone, cellulose acetate, polyvinyl alcohol, and polyethersulfone. From the viewpoints of membrane strength and chemical resistance, polyvinylidene fluoride (PVDF) is more preferable.

[0032] The hollow fiber membrane module 10 is of an external pressure filtration type and may be of an external pressure total amount filtration type or an external pressure circulation filtration type according to the conditions of the membrane separation treatment and the required performance. From the viewpoint of membrane life, an external pressure circulation filtration type that can simultaneously perform surface cleaning of the filtration membrane is preferable. From the viewpoints of simplicity of equipment, installation cost, and operation cost, an external pressure total amount filtration type is preferable.

[0033] As the total number of the hollow fiber membranes 14 constituting each hollow fiber membrane bundle 15 in the hollow fiber membrane module 10 increases, the membrane area per module increases, so that it can be operated with a high filtration flow rate. On the other hand, the discharge efficiency of suspended contaminants during cleaning decreases. Therefore, the membrane filling rate 100πndi 2 / 4S (%) calculated by the outer diameter di (m) of the hollow fiber membrane 14, the total number n (pieces) of the hollow fiber membranes 14, and the cross-sectional area S (m 2 ) is preferably 10 to 60%, and more preferably 20 to 50%.

[0034] The housing 13 has a cylindrical shape having an upper surface 13A and a lower surface 13C, and side surfaces 13B connecting them. The housing 13 has an internal space S1 in which a plurality of hollow fiber membrane bundles 15 are accommodated, and the internal space S1 is divided into an upper space S11 where the upper part in the longitudinal direction (vertical direction) of the hollow fiber membrane 14 is located and a lower space S12 where the lower part in the longitudinal direction of the hollow fiber membrane 14 is located.

[0035] A filtrate pipe 51 for taking out the filtrate is connected to the upper surface 13A of the housing 13, and a filtrate outlet 52 and a filtrate-side gas inlet 53 are provided in the filtrate pipe 51. A gas vent 11 for discharging the gas in the internal space S1 to the outside of the system is provided directly below the fixing member 3 on the side surface 13B. The gas vent 11 is an opening of the upper space S11. A drain vent 12 for discharging the liquid in the internal space S1 to the outside of the system is provided directly above the lower surface 13C on the side surface 13B. A diffusing gas inlet 7 for supplying gas into the internal space S1 is provided near the center of the lower surface 13C.

[0036] As shown in FIG. 1, a gas vent pipe 61 is connected to the gas vent 11, and the gas in the housing 13 is discharged to the outside of the system through this. A gas discharge port valve 62 is provided in the gas vent pipe 61, and the gas is evacuated from the housing 13 by opening this. Also, a drain pipe 41 is connected to the drain vent 12, and the liquid in the housing 13 is discharged to the outside of the system through this. A stock solution discharge port valve 42 is provided in the drain pipe 41, and the liquid is discharged from the housing 13 by opening this.

[0037] As the material of the housing 13, SUS, modified PPE, polyvinyl chloride, polysulfone, polycarbonate, polyolefin, ABS resin, etc. are used. By adhesively fixing the fixing member 3 to the inner surface of the housing 13, a so-called integrated module may be configured. Further, an O-ring, packing, etc. may be attached to the outer peripheral portion of the fixing member 3, and the fixing member 3 may be detachably and liquid-tightly attached to the housing 13. In this case, the fixing member 3 can be removed to replace each hollow fiber membrane bundle 15, and the housing 13 can be repeatedly used.

[0038] As shown in FIG. 2, the water conduit 5 is disposed so as to penetrate the center of the lower surface 13C of the housing 13 and extend toward the upper surface 13A, and the upper end is connected to the fixing member 3. The water conduit 5 is provided with a raw liquid inlet 9 on the lower end side and a gas inlet 8 for the water conduit on the side surface. According to the water conduit 5, only the raw water before filtration introduced from the raw liquid inlet 9 can be supplied into the housing 13, only the gas introduced from the gas inlet 8 for the water conduit can be supplied into the housing 13, and both the raw water and the gas can be supplied into the housing 13. The water conduit 5 constitutes a part of the gas supply unit 2.

[0039] The gas supply unit 2 includes the above-described water conduit 5 and a diffusing member 4. The diffusing member 4 is a member for dispersing the gas supplied into the housing 13 from the gas inlet 7 for diffusion provided on the lower surface 13C of the housing 13 so as to spread in the radial direction of each hollow fiber membrane bundle 15. The diffusing member 4 is disposed at a position below the plurality of hollow fiber membrane bundles 15, and the water conduit 5 penetrates through the central portion. The detailed structures of the water conduit 5 and the diffusing member 4 will be described later.

[0040] The restraining member 100 is provided individually for each of the plurality of hollow fiber membrane bundles 15. Each of the restraining members 100 is a member that controls the movement of the plurality of hollow fiber membranes 14 in the corresponding hollow fiber membrane bundle 15 in a state where gas is supplied into the internal space S1 of the housing 13 by the gas supply unit 2. The detailed structure of the restraining member 100 will be described later.

[0041] As shown in FIG. 1, the liquid feed pump 20 is connected to the raw liquid inlet 9 of the water conduit 5 via the raw liquid introduction pipe 21. A raw liquid introduction valve 22 for switching the flow and interruption of the raw water in the pipe is provided in the raw liquid introduction pipe 21. The liquid feed pump 20 supplies raw water into the water conduit 5 via the raw liquid introduction pipe 21.

[0042] The air compressor 30 is connected to the filtrate side gas inlet 53 via the first gas introduction pipe 31, connected to the air diffusing gas inlet 7 via the second gas introduction pipe 32, and connected to the water conduit gas inlet 8 via the third gas introduction pipe 33. A first gas introduction valve 34 for switching the flow and interruption of the gas in the pipe is provided in the first gas introduction pipe 31, and second and third gas introduction valves 35 and 36 are similarly provided in the second and third gas introduction pipes 32 and 33. Thus, in the present embodiment, the third gas introduction pipe 33 and the third gas introduction valve 36 as the gas supply means for the water conduit 5, and the second gas introduction pipe 32 and the second gas introduction valve 35 as the gas supply means for the air diffusing member 4 are separately provided.

[0043] The control device 40 controls the driving of the liquid feed pump 20 and the air compressor 30, and also controls the opening and closing operations of each valve. The control device 40 is constituted by, for example, a personal computer or the like. The control device 40 has a storage unit in which the sequence information of each process (water filling, filtration, backwashing, bubbling, drainage, etc.) sequentially executed in the filtration process is stored, and a control unit that controls the driving of each device and the opening and closing of the valves according to the sequence information.

[0044] [Air diffusing member, water conduit] Next, the detailed structures of the air diffusing member 4 and the water conduit 5 will be described with reference to FIGS. 2 to 5. FIG. 3 shows the planar structure of the air diffusing member 4. FIG. 4 shows the cross-sectional structure of the air diffusing member 4 along the line segment IV-IV in FIG. 3. FIG. 5 shows the cross-sectional structure of the water conduit 5 along the line segment V-V in FIG. 2. In the hollow fiber membrane module 10, the gas supply unit 2 that supplies the cleaning gas (e.g., air) for the hollow fiber membranes 14 while dispersing it in the internal space S1 of the housing 13 has the air diffusing member 4 and the water conduit 5.

[0045] The air diffusing member 4 is disposed below the lower end 14A of the hollow fiber membranes 14 that constitute each hollow fiber membrane bundle 15. The air diffusing member 4 has a shape that spreads in the radial direction of each hollow fiber membrane bundle 15. A plurality of air diffusing vent holes 43 for dispersing gas in the housing 13 are formed at intervals in the radial direction in the air diffusing member 4.

[0046] The air diffusing member 4 has a disk-shaped main body portion 44 in which a plurality of air diffusing vent holes 43 are formed, a peripheral wall portion 47 connected to the peripheral edge of the main body portion 44, and a cylindrical gas receiving portion 45 connected to the lower surface of the main body portion 44, and these are integrally formed.

[0047] The air-diffusing vent hole 43 is formed so as to penetrate the main body portion 44 in the thickness direction. The air-diffusing vent holes 43 are formed at intervals in the radial direction and circumferential direction of the main body portion 44, and a part of them is located radially outside each hollow fiber membrane bundle 15. Thereby, gas can be dispersed in a wide range in the radial direction with respect to each hollow fiber membrane bundle 15. As shown in FIG. 3, the air-diffusing vent holes 43 are arranged on a plurality of circumferences spaced apart in the radial direction in the main body portion 44. In this case, the number of air-diffusing vent holes 43 on each circumference is set so as to satisfy the condition that it is a multiple of the number of hollow fiber membrane bundles 15. Specifically, the number of air-diffusing vent holes 43 on each circumference is set so as to satisfy the condition that it is a multiple of the number of hollow fiber membrane bundles 15 such that the number of air-diffusing vent holes 43 corresponding to each hollow fiber membrane bundle 15 is the same. Further, a through hole 44A through which the water conduit 5 penetrates is formed at the center of the main body portion 44. Note that the main body portion 44 is not limited to a disk shape as shown in FIG. 3, and may have various shapes.

[0048] The gas receiving portion 45 is a portion for temporarily accommodating the gas supplied into the housing 13 from the air-diffusing gas inlet 7. The gas receiving portion 45 has a cylindrical shape, the upper end (one end) thereof is connected to the lower surface of the main body portion 44, and a gas receiving port 45A is formed on the lower end (the other end) side. In the present embodiment, the gas receiving portion 45 is configured such that the inner diameter is substantially constant from the upper end to the lower end. Note that the gas receiving portion 45 may be configured to have a shape in which the inner diameter expands from the upper end to the lower end. The inner diameter of the gas receiving portion 45 is larger than the outer diameter of the water conduit 5, and the gas is accommodated in the gap between the outer peripheral surface of the water conduit 5.

[0049] The gas receiving portion 45 is located radially outside the air-diffusing gas inlet 7, whereby the gas supplied into the housing 13 from the air-diffusing gas inlet 7 can be accommodated in the cylinder. Further, as shown in FIG. 2, a gap is formed between the lower end of the gas receiving portion 45 and the lower wall of the housing 13, and the liquid in the housing 13 can flow through the gap. Thereby, it is possible to prevent liquid accumulation in the lower portion of the housing 13.

[0050] At a portion on the upper end side of the gas receiving portion 45, a plurality of dispersion holes 46 are formed at intervals in the circumferential direction. The dispersion holes 46 are formed so as to penetrate the gas receiving portion 45. The dispersion holes 46 can allow the gas accommodated in the gas receiving portion 45 to escape radially outward of the gas receiving portion 45 and guide it to the gas diffusing vent hole 43. The dispersion holes 46 may be formed at equal intervals in the circumferential direction, or may be formed at different intervals.

[0051] The peripheral wall portion 47 has a cylindrical shape extending downward from the peripheral edge portion of the main body portion 44. The peripheral wall portion 47 can suppress the gas discharged from the dispersion holes 46 to the outside of the gas receiving portion 45 from spreading outside the main body portion 44. Thereby, before the gas is dispersed from the gas diffusing vent hole 43, the gas can be retained on the lower surface of the main body portion 44.

[0052] According to the gas diffusing member 4, in the bubbling step, the gas supplied into the housing 13 from the gas diffusing gas inlet 7 is temporarily accommodated by the gas receiving portion 45, then escaped to the outside from the dispersion holes 46, and then can be dispersed into the lower space S12 from the gas diffusing vent hole 43. That is, in the present embodiment, the gas diffusing vent hole 43 functions as a lower gas supply portion that disperses gas in the housing 13 at a position below the lower space S12.

[0053] The water guide pipe 5 is arranged so as to extend in the vertical direction through the center of the housing 13. The water guide pipe 5 has a cylindrical shape, but is not particularly limited. As shown in FIG. 2, the water guide pipe 5 penetrates the gas diffusing member 4 (main body portion 44), and the lower end is fixed to the stock solution introduction pipe 21 (FIG. 1) via an arbitrary seal member (not shown). The fixing method of the water guide pipe 5 is not limited to this, and a separate pipe protruding upward from the upper surface of the main body portion 44 may be provided, and the water guide pipe 5 may be placed on the upper surface of the main body portion 44 so that the protruding portion is located inside the water guide pipe 5.

[0054] In the water conduit 5, a plurality of tube ventilation holes 54 are formed at intervals over the entire longitudinal direction (vertical direction) at a position protruding above the upper surface of the main body portion 44. More specifically, in the water conduit 5, a plurality of tube ventilation holes 54 are formed at intervals from each other at a position located in the upper space S11, and a plurality of tube ventilation holes 54 are also formed at intervals from each other at a position located in the lower space S12. By these tube ventilation holes 54, the gas for bubbling (cleaning gas) can be supplied into the housing 13, and the raw water filtered by the hollow fiber membrane 14 can be supplied into the housing 13. Note that the tube ventilation holes 54 may be formed at equal intervals in the longitudinal direction, or may be formed at different intervals. Also, the tube ventilation holes 54 are circular in shape, but are not particularly limited.

[0055] The plurality of tube ventilation holes 54 are each formed to have the same size in the longitudinal direction of the water conduit 5. The inner diameter of the tube ventilation hole 54 is preferably designed to be 30 mm or less in order to enhance the bubbling effect. Also, the inner diameter of the tube ventilation hole 54 is preferably designed so that the total discharge flow rate of the raw water from each hole is 4 m / s or less, and more preferably 3 m / s or less, in order to reduce the pressure loss during water flow.

[0056] As shown in FIG. 2, the tube ventilation hole 54A formed at the uppermost part of the water conduit 5 is located above the lower surface 11A of the gas vent 11, and the second tube ventilation hole 54B from the top is located below the lower surface 11A. That is, in the water conduit 5, the tube ventilation holes 54A and 54B are formed at positions sandwiching the lower surface 11A of the gas vent 11 in the vertical direction.

[0057] As shown in FIG. 5, four tube ventilation holes 54 are formed at equal intervals in the circumferential direction of the water conduit 5. In the present embodiment, four tube ventilation holes 54 are formed at 90° intervals in both the portion located in the upper space S11 and the portion located in the lower space S12, but the number and the circumferential interval are not particularly limited. Also, the number and the circumferential interval of the tube ventilation holes 54 may be different between the portion located in the upper space S11 and the portion located in the lower space S12.

[0058] FIG. 6 is an enlarged view of the water conduit 5 in region VI in FIG. 2. The aperture ratio of the pipe ventilation holes 54 in the water conduit 5 can be defined as follows. As shown in the hatched portion of FIG. 6, when the area of the outer peripheral surface of the water conduit 5 in the range from the middle height position of the uppermost pipe ventilation hole 54A to the middle height position of the pipe ventilation hole 54B below it is S1, and the total aperture area of all the pipe ventilation holes 54A and 54B formed on the outer peripheral surface of the said range is S2, the aperture ratio of the pipe ventilation holes can be defined as S2 / S1×100. In the present embodiment, it is preferable that the aperture ratio is designed to be 1% or more and 20% or less.

[0059] According to the water conduit 5, raw water can be supplied into the housing 13 from the pipe ventilation holes 54, and the gas introduced from the gas inlet 8 for the water conduit can be lifted by buoyancy and dispersed into the housing 13 from the pipe ventilation holes 54A and 54B located in the upper space S11. That is, in the present embodiment, the pipe ventilation holes 54A and 54B function as an upper gas supply part for dispersing gas into the housing 13 at the position of the upper space S11.

[0060] The length of the water conduit 5 inserted into the housing 13 is preferably 1 to 2 times, and more preferably 1 to 1.5 times, the length of the hollow fiber membrane 14 in order not to make the hollow fiber membrane module 10 bulky.

[0061] The inner diameter of the water conduit 5 is preferably designed so that the flux during water flow is 4 m / s or less, and more preferably 3 m / s or less, in order to reduce the pressure loss during water flow.

[0062] [Suppressing member] Next, the detailed structure of the suppression member 100 will be described with reference to FIGS. 7 and 8 in addition to FIG. 2. In the hollow fiber membrane module 10 according to the present embodiment, the upper end 14B of the hollow fiber membrane 14 constituting the hollow fiber membrane module 10 is fixed to the fixing member 3 and divided into a plurality of hollow fiber membrane bundles 15. The plurality of hollow fiber membrane bundles 15 are arranged in the internal space S1 of the housing 13 at equal intervals in the circumferential direction so as to surround the water conduit 5. In the example shown in FIG. 8, six hollow fiber membrane bundles 15 are arranged so as to surround the water conduit 5, but the number of arranged hollow fiber membrane bundles 15 is not particularly limited as long as it is a plurality of two or more.

[0063] The suppression member 100 is provided individually for each of the plurality of hollow fiber membrane bundles 15. Thereby, each hollow fiber membrane bundle 15 becomes a state independent of each other by the suppression member 100. For this reason, in the bubbling process in which the cleaning gas is supplied to the internal space S1 of the housing 13 by the gas supply unit 2, the plurality of hollow fiber membranes 14 swing within the hollow fiber membrane bundles 15 in an independent state.

[0064] When the plurality of hollow fiber membranes 14 swing within each hollow fiber membrane bundle 15, the floating contaminants attached to the membrane surface are peeled off. At this time, since each hollow fiber membrane bundle 15 is in an independent state by the suppression member 100, the floating contaminants peeled off from the membrane surfaces of the plurality of hollow fiber membranes 14 within each hollow fiber membrane bundle 15 can be discharged through the spaces between the hollow fiber membrane bundles 15. Thereby, the floating contaminants attached to the membrane surface of the hollow fiber membrane 14 within each hollow fiber membrane bundle 15 can be effectively removed. Moreover, since each hollow fiber membrane bundle 15 is in an independent state by the suppression member 100, the interference between the hollow fiber membranes 14 belonging to different hollow fiber membrane bundles 15 is suppressed. Thereby, it is possible to suppress the entanglement between the hollow fiber membranes 14 between the hollow fiber membrane bundles 15 and to suppress the accompanying damage to the hollow fiber membrane 14.

[0065] Further, the restraining member 100 that keeps each hollow fiber membrane bundle 15 in an independent state is configured to allow the plurality of hollow fiber membranes 14 to swing within the hollow fiber membrane bundle 15 while restraining the lower ends 14A of the plurality of hollow fiber membranes 14 from rising. That is, the bending of the hollow fiber membrane 14 is suppressed to such an extent that the lower end 14A of the hollow fiber membrane 14 is positioned above the lower end 100A of the restraining member 100. By restraining the upward movement of the lower ends 14A of the plurality of hollow fiber membranes 14 within the hollow fiber membrane bundle 15, excessive movement of the plurality of hollow fiber membranes 14 within the hollow fiber membrane bundle 15 is restricted. For this reason, it is possible to suppress excessive interference between the hollow fiber membranes 14, such as entanglement between the hollow fiber membranes 14 belonging to the same hollow fiber membrane bundle 15, and to suppress damage to the hollow fiber membranes 14 associated therewith.

[0066] Moreover, each restraining member 100 has a function of partitioning between the plurality of hollow fiber membrane bundles 15 so that a gap is formed therebetween. By forming a gap between the respective hollow fiber membrane bundles 15 by the restraining member 100 in this way, the floating contaminants peeled off in accordance with the swinging of the plurality of hollow fiber membranes 14 within each hollow fiber membrane bundle 15 in the bubbling process can be discharged through the gap between the hollow fiber membrane bundles 15. Thereby, the removal effect of the floating contaminants adhering to the membrane surface of the hollow fiber membrane 14 can be further enhanced.

[0067] As shown in FIG. 7, each restraining member 100 has a plurality of meshes 101 and is constituted by a net-like body extending in the vertical direction so as to cover the side surface of the corresponding hollow fiber membrane bundle 15. In this case, various materials can be used as the material of the restraining member 100, and it is not particularly limited. For example, polyethylene, polypropylene, etc. can be exemplified. The restraining member 100 constituted by the net-like body has elasticity according to the deformation of the shape of the mesh 101. When the plurality of hollow fiber membranes 14 swing within the hollow fiber membrane bundle 15 in the bubbling process, the restraining member 100 moderately swings the plurality of hollow fiber membranes 14 by deforming and expanding the shape of the mesh 101.

[0068] The lower ends 100A of the restraining members 100 each formed of a reticulated body are each positioned within an appropriate lower end range capable of suppressing the upward movement of the lower ends 14A of the plurality of hollow fiber membranes 14 that swing within the corresponding hollow fiber membrane bundle 15 and capable of suppressing the entry of the lower ends 14A of the plurality of hollow fiber membranes 14 into the meshes 101. The appropriate lower end range is a range in which the lower end 100A of the restraining member 100 is spaced downward from the upper end 14B of the hollow fiber membrane 14 by a range of 0.7 times or more and 1.0 times or less the effective length L2 of the hollow fiber membrane 14. Note that the effective length L2 of the hollow fiber membrane 14 is the vertical length of the portion of the hollow fiber membrane 14 that is exposed in the internal space S1 of the housing 13.

[0069] By suppressing the upward movement of the lower ends 14A of the plurality of hollow fiber membranes 14 within the corresponding hollow fiber membrane bundle 15 by the restraining member 100, it is possible to suppress the entanglement of the hollow fiber membranes 14 with each other within the hollow fiber membrane bundle 15. Furthermore, by setting the position of the lower end 100A of the restraining member 100 so as to be able to suppress the entry of the lower end 14A of the hollow fiber membrane 14 into the mesh 101 of the restraining member 100, it is possible to regulate the entanglement of the hollow fiber membrane 14 with the restraining member 100. Thereby, it is possible to suppress damage to the hollow fiber membrane 14.

[0070] In the present embodiment, the upper ends 100B of the restraining members 100 each formed of a reticulated body are each fixed to the upper ends 14B of the plurality of hollow fiber membranes 14 within the corresponding hollow fiber membrane bundle 15 and are fixed to the fixing member 3. Specifically, the upper end 100B of the restraining member 100 and the upper ends 14B of the plurality of hollow fiber membranes 14 are fixed to the fixing member 3 such that their vertical height positions coincide. By fixing the upper end 100B of the restraining member 100 to the fixing member 3, the side surface of the hollow fiber membrane bundle 15 can be stably covered.

[0071] The vertical length L1 of the restraining member 100 each formed of a reticulated body is preferably set so as to satisfy the following formula (1). In the following formula (1), "L1" indicates the vertical length of the restraining member 100, and "L2" indicates the effective length of the hollow fiber membrane 14. 0.7 ≦ L1 / L2 ≦ 1.0 ···(1)

[0072] By setting the vertical length L1 of the suppression member 100 so as to satisfy the left side of the above formula (1), "0.7 ≦ L1 / L2", the lower end 100A of the suppression member 100 can be positioned within the appropriate lower end range that can suppress the upward movement of the lower ends 14A of the plurality of hollow fiber membranes 14. On the other hand, by setting the vertical length L1 of the suppression member 100 so as to satisfy the right side of the above formula (1), "L1 / L2 ≦ 1.0", the lower end 100A of the suppression member 100 can be positioned within the appropriate lower end range that can suppress the lower ends 14A of the plurality of hollow fiber membranes 14 from entering the mesh 101 of the suppression member 100.

[0073] [Cleaning Method of Hollow Fiber Membrane Module] Next, the filtration operation by the filtration device 1 and the cleaning method of the hollow fiber membrane module 10 performed during the operation will be described with reference to FIG. 9. FIG. 9 shows the relationship between each step and the opening and closing states of the valves regarding the basic operation method of the filtration device 1 shown in FIG. 1. The circles in FIG. 9 mean that the corresponding valves are open.

[0074] First, a water filling step (before filtration) is performed. In this step, from the state where all the valves of the filtration device 1 are closed, the control device 40 opens the raw liquid introduction valve 22 and the gas discharge port valve 62, and the liquid feed pump 20 operates. Thereby, raw water is introduced into the water conduit 5 from the liquid feed pump 20 through the raw liquid introduction pipe 21, and the raw water is supplied into the housing 13 from the pipe vent hole 54. Thereby, the internal space S1 of the housing 13 is filled with water.

[0075] Next, a filtration step is performed. In this step, after the raw water overflows from the gas vent 11, the control device 40 opens the filtrate outlet valve 71 and closes the gas discharge port valve 62. Then, the raw water filled in the internal space S1 penetrates from the outer surface side of the hollow fiber membrane 14 through the wall surface to the inner surface side, and is taken out as filtrate from the space S2 on the filtrate side.

[0076] As the filtration time elapses, suspended contaminants in the raw water adhere to the outer surface of the hollow fiber membrane 14, thereby reducing the filtration capacity. Therefore, after filtration is carried out for a certain period of time, the membrane surface of the hollow fiber membrane 14 is cleaned by implementing the cleaning method of the hollow fiber membrane module 10 described below.

[0077] First, a backwashing process is carried out. In this process, the control device 40 opens the stock solution discharge port valve 42 and the first gas introduction valve 34, and operates the air compressor 30. As a result, gas (for example, air) is introduced into the filtrate side space S2 of the housing 13 from the filtrate side gas inlet 53, and the filtrate is pressurized by the gas. The filtrate is pushed out from the inner surface side to the outer surface side of the hollow fiber membrane 14, and as a result, a part of the liquid in the internal space S1 is discharged to the outside of the system through the drain port 12. In this way, the backwashing of the hollow fiber membrane 14 is performed. Then, by opening the filtrate side pressure relief valve 81, the pressure in the space S2 on the filtrate side is reduced.

[0078] Next, a water filling process (before lower bubbling) is carried out. In this process, in order to raise the liquid level in the internal space S1 that decreased in the above backwashing process, the control device 40 opens the gas discharge port valve 62 and the stock solution introduction valve 22, and operates the liquid feed pump 20. As a result, liquid is introduced into the internal space S1, and the liquid level rises. Then, the liquid feed pump 20 is stopped, the stock solution introduction valve 22 is closed, and the supply of liquid is stopped.

[0079] Next, the lower bubbling process is carried out. In this process, with the internal space S1 filled with water, the control device 40 opens the second gas introduction valve 35 and the air compressor 30 operates. As a result, gas is supplied into the housing 13 from the diffusing gas inlet 7 through the second gas introduction pipe 32. Then, after the gas is received by the gas receiving part 45, it is dispersed from the diffusing vent holes 43 into the lower space S12. And the gas rising from the lower space S12 to the upper space S11 causes the plurality of hollow fiber membranes 14 to swing within each of the hollow fiber membrane bundles 15 in a state independent of each other by the suppressing member 100, and the floating contaminants attached to the membrane surface are peeled off by this action. Thus, in the lower bubbling process, the gas is dispersed in the housing 13 at a position below the plurality of hollow fiber membrane bundles 15, and the gas is raised to the upper space S11, whereby the hollow fiber membranes 14 located in the lower part of the lower space S12 and the lower part of the upper space S11 are cleaned.

[0080] The floating contaminants peeled off from the membrane surfaces of the plurality of hollow fiber membranes 14 within each hollow fiber membrane bundle 15 are discharged through the gaps between the hollow fiber membrane bundles 15. Thereby, the floating contaminants attached to the membrane surfaces of the hollow fiber membranes 14 within each hollow fiber membrane bundle 15 can be effectively removed. Moreover, since each hollow fiber membrane bundle 15 is in a state independent of each other by the suppressing member 100, the interference between the hollow fiber membranes 14 belonging to different hollow fiber membrane bundles 15 is suppressed. Thereby, it is possible to suppress the entanglement of the hollow fiber membranes 14 with each other between the hollow fiber membrane bundles 15, and to suppress the accompanying damage to the hollow fiber membranes 14.

[0081] Further, by suppressing the upward movement of the lower ends 14A of the plurality of hollow fiber membranes 14 in the hollow fiber membrane bundle 15, excessive movement of the plurality of hollow fiber membranes 14 in the hollow fiber membrane bundle 15 is restricted. For this reason, it is possible to suppress excessive interference between the hollow fiber membranes 14, such as the entanglement of the hollow fiber membranes 14 belonging to the same hollow fiber membrane bundle 15, and it is possible to suppress damage to the hollow fiber membranes 14 associated therewith. Furthermore, by setting the position of the lower end 100A of the suppression member 100 so as to suppress the lower end 14A of the hollow fiber membrane 14 from entering the mesh 101 of the suppression member 100, it is possible to regulate the entanglement of the hollow fiber membrane 14 with the suppression member 100. Thereby, it is possible to suppress damage to the hollow fiber membrane 14.

[0082] Next, a drainage step is performed. In this step, the second gas introduction valve 35 is closed by the control device 40 and the stock solution discharge port valve 42 is opened. Thereby, the liquid containing the suspended contaminants peeled from the membrane surface in the lower bubbling step is discharged to the outside of the system through the drain port 12.

[0083] Next, a water filling step (before upper bubbling) is performed. In this step, the gas discharge port valve 62 and the stock solution introduction valve 22 are opened, and the liquid feed pump 20 is operated to fill the internal space S1 with liquid again.

[0084] Next, an upper bubbling step is performed. This step is performed for the purpose of more surely removing the suspended contaminants adhering to the membrane surface at the upper end 14B of the hollow fiber membrane 14 where the cleaning was insufficient in the lower bubbling step.

[0085] First, the control device 40 closes the stock solution introduction valve 22 and opens the third gas introduction valve 36. As a result, gas is introduced into the water conduit 5 from the gas inlet 8 for the water conduit through the third gas introduction pipe 33. Then, the gas rises in the pipe due to buoyancy and is dispersed into the housing 13 from the pipe ventilation holes 54A and 54B located in the upper space S11. Thereby, bubbling cleaning can be performed around the upper end 14B of the hollow fiber membrane 14, and the floating contaminants adhering to the membrane surface around the upper end 14B that could not be sufficiently removed in the lower bubbling process can be more reliably removed. Thus, in the upper bubbling process, the hollow fiber membrane 14 is cleaned by dispersing gas into the housing 13 at the position of the upper space S11.

[0086] Also, in the upper bubbling process, immediately after the start of bubbling, since the entire internal space S1 is filled with water, bubbling cleaning can be performed by the gas discharged from the uppermost pipe ventilation hole 54A and the pipe ventilation hole 54B below it. Then, when a certain period of time has elapsed since the start of bubbling, the liquid containing gas is discharged from the gas vent 11, and the liquid level of the internal space S1 drops to the lower surface 11A. Even in this state, due to the buoyancy of the gas supplied to the water conduit 5, the water in the water conduit 5 can be ejected together with the gas from the pipe ventilation hole 54A above the lower surface 11A of the gas vent 11, and the water in the housing 13 can flow into the water conduit 5 from the pipe ventilation hole 54B below the lower surface 11A of the gas vent 11. Thereby, since the mixed fluid of liquid and gas can be continuously ejected from the pipe ventilation hole 54A above the lower surface 11A of the gas vent 11 for bubbling, the upper end 14B of the hollow fiber membrane 14 can be effectively cleaned.

[0087] Next, the drainage process is performed. In this process, the third gas introduction valve 36 is closed and the stock solution discharge port valve 42 is opened. As a result, the liquid containing the floating contaminants peeled off from the membrane surface in the upper bubbling process is discharged out of the system from the drain port 12. After the hollow fiber membrane module 10 is cleaned as described above, the filtration operation is restarted.

[0088] In both the upper and lower bubbling processes, the supply flow rate of the gas is preferably 12000 NL / h or less, and preferably within the range of 1500 to 12000 NL / h. In the lower bubbling process, if the supply flow rate of the gas becomes excessive, there is a risk that the hollow fiber membranes 14 may become entangled with each other and the membrane surface may be damaged. In contrast, in the present embodiment, in the lower bubbling process, the suppressing member 100 suppresses excessive swaying of the hollow fiber membranes 14 for each hollow fiber membrane bundle 15, so that the upper limit gas supply flow rate in the lower bubbling process can be increased. Generally, such a problem is unlikely to occur in the upper bubbling process. Therefore, in the upper bubbling process, the supply flow rate of the gas may be set higher than that in the lower bubbling process. However, due to the effect of the suppressing member 100, it is possible to supply gas at a flow rate similar to that in the upper bubbling process even in the lower bubbling process.

[0089] (Second Embodiment) Next, the structure of the hollow fiber membrane module 10 according to the second embodiment of the present invention will be described with reference to FIG. 10. The hollow fiber membrane module 10 according to the second embodiment basically has the same configuration as in the case of the first embodiment described above and exhibits the same effects. However, the structure of the suppressing member 100 provided individually for each of the plurality of hollow fiber membrane bundles 15 is different from that of the first embodiment.

[0090] In the hollow fiber membrane module 10 according to the second embodiment, each suppressing member 100 has a plurality of meshes 101, similar to the case of the first embodiment described above, and is constituted by a net-like body extending in the vertical direction so as to cover the side surface of the corresponding hollow fiber membrane bundle 15. In the first embodiment, the upper end 100B of the suppressing member 100 was fixed to the fixing member 3. However, in the second embodiment, the upper end 100B of the suppressing member 100 is located below the upper end 14B of the hollow fiber membrane 14. That is, the upper end 100B of the suppressing member 100 is separated from the fixing member 3. In this case, the suppressing member 100 is, for example, adhesively fixed to the side surface 13B of the housing 13.

[0091] The lower end 100A of the suppression member 100 is located within the appropriate range of the lower end such that, similar to the case of the first embodiment, it can suppress the upward movement of the lower ends 14A of the plurality of hollow fiber membranes 14 that swing within the corresponding hollow fiber membrane bundle 15, and can also suppress the lower ends 14A of the plurality of hollow fiber membranes 14 from entering the mesh 101.

[0092] By suppressing the upward movement of the lower ends 14A of the plurality of hollow fiber membranes 14 within the corresponding hollow fiber membrane bundle 15 by the suppression member 100, it is possible to suppress the entanglement of the hollow fiber membranes 14 with each other within the hollow fiber membrane bundle 15. Further, by setting the position of the lower end 100A of the suppression member 100 so as to suppress the lower end 14A of the hollow fiber membrane 14 from entering the mesh 101 of the suppression member 100, it is possible to regulate the entanglement of the hollow fiber membrane 14 with the suppression member 100. Thereby, it is possible to suppress damage to the hollow fiber membrane 14.

[0093] (Third Embodiment) Next, the structure of the hollow fiber membrane module 10 according to the third embodiment of the present invention will be described with reference to FIG. 11. The hollow fiber membrane module 10 according to the third embodiment basically has the same configuration as in the case of the first embodiment and exhibits the same effects, but the structure of the suppression member 100 provided individually for each of the plurality of hollow fiber membrane bundles 15 is different from that of the first embodiment.

[0094] As shown in FIG. 11, each of the suppression members 100 in the third embodiment is constituted by a cylindrical body 102 in which a plurality of through-holes 103 are formed and which extends in the vertical direction so as to cover the side surface of the corresponding hollow fiber membrane bundle 15. The suppression member 100 of the first embodiment was constituted by a net-like body and had elasticity according to the deformation of the shape of the mesh 101, but the suppression member 100 of the third embodiment has rigidity such that the shape of the through-hole 103 does not deform. Thereby, each of the suppression members 100 can make each hollow fiber membrane bundle 15 more reliably independent of each other. For this reason, in the bubbling process, interference between the hollow fiber membranes 14 belonging to different hollow fiber membrane bundles 15 is more reliably suppressed.

[0095] The upper end 100B of the suppression member 100 of the third embodiment is fixed to the upper ends 14B of a plurality of hollow fiber membranes 14 in the corresponding hollow fiber membrane bundle 15 and is also fixed to the fixing member 3. Further, the lower end 100A of the suppression member 100 is located within the appropriate range of the lower end such that, similar to the case of the first embodiment, it can suppress the upward movement of the lower ends 14A of the plurality of hollow fiber membranes 14 that swing within the corresponding hollow fiber membrane bundle 15 and can also suppress the lower ends 14A of the plurality of hollow fiber membranes 14 from entering the through-hole 103.

[0096] By suppressing the upward movement of the lower ends 14A of the plurality of hollow fiber membranes 14 in the corresponding hollow fiber membrane bundle 15 by the suppression member 100, it is possible to suppress the entanglement of the hollow fiber membranes 14 with each other within the hollow fiber membrane bundle 15. Further, by setting the position of the lower end 100A of the suppression member 100 so as to be able to suppress the lower end 14A of the hollow fiber membrane 14 from entering the through-hole 103 of the suppression member 100, it is possible to regulate the entanglement of the hollow fiber membrane 14 with the suppression member 100. Thereby, it is possible to suppress damage to the hollow fiber membrane 14.

[0097] (Fourth Embodiment) Next, the structure of the hollow fiber membrane module 10 according to the fourth embodiment of the present invention will be described with reference to FIG. 12. The hollow fiber membrane module 10 according to the fourth embodiment basically has the same configuration as in the case of the first embodiment and exhibits the same effects, but the structure of the suppression member 100 provided individually for each of the plurality of hollow fiber membrane bundles 15 is different from that of the first embodiment.

[0098] As shown in FIG. 12, each of the suppression members 100 of the fourth embodiment is constituted by a spiral string-like body wound around the side surface of the corresponding hollow fiber membrane bundle 15. The suppression member 100 constituted by the spiral string-like body keeps each hollow fiber membrane bundle 15 in an independent state while being wound around the side surface of the hollow fiber membrane bundle 15. Thereby, in the bubbling process, interference between the hollow fiber membranes 14 belonging to different hollow fiber membrane bundles 15 is suppressed.

[0099] The upper end 100B of the suppression member 100 of the fourth embodiment is fixed to the upper ends 14B of a plurality of hollow fiber membranes 14 in the corresponding hollow fiber membrane bundle 15 and is also fixed to the fixing member 3. Further, similar to the case of the first embodiment, the lower end 100A of the suppression member 100 is positioned within the appropriate lower end range that can suppress the upward movement of the lower ends 14A of the plurality of hollow fiber membranes 14 that swing within the corresponding hollow fiber membrane bundle 15 and can also suppress the lower ends 14A of the plurality of hollow fiber membranes 14 from getting caught on the suppression member 100.

[0100] By suppressing the upward movement of the lower ends 14A of the plurality of hollow fiber membranes 14 in the corresponding hollow fiber membrane bundle 15 by the suppression member 100, it is possible to suppress the entanglement of the hollow fiber membranes 14 with each other within the hollow fiber membrane bundle 15. Furthermore, by setting the position of the lower end 100A of the suppression member 100 so as to be able to suppress the lower ends 14A of the hollow fiber membranes 14 from getting caught on the suppression member 100, it is possible to regulate the entanglement of the hollow fiber membranes 14 with the suppression member 100. Thereby, it is possible to suppress damage to the hollow fiber membranes 14.

[0101] (Fifth Embodiment) Next, the structure of the hollow fiber membrane module 10 according to the fifth embodiment of the present invention will be described with reference to FIG. 13. The hollow fiber membrane module 10 according to the fifth embodiment basically has the same configuration as in the case of the first embodiment and exhibits the same effects, but the structure of the suppression member 100 provided individually for each of the plurality of hollow fiber membrane bundles 15 is different from that of the first embodiment.

[0102] As shown in FIG. 13, each of the suppression members 100 of the fifth embodiment is constituted by a plurality of belt-like bodies 104 wound around the side surface of the corresponding hollow fiber membrane bundle 15. The plurality of belt-like bodies 104 are arranged at a predetermined interval in the vertical direction of the hollow fiber membrane bundle 15, and are, for example, adhesively fixed to the side surface 13B of the housing 13. The suppression member 100 constituted by the plurality of belt-like bodies 104 makes each hollow fiber membrane bundle 15 independent of each other in a state where each belt-like body 104 is wound around the side surface of the hollow fiber membrane bundle 15. Thereby, in the bubbling process, interference between the hollow fiber membranes 14 belonging to different hollow fiber membrane bundles 15 is suppressed.

[0103] The lowermost belt-like body 104 among the plurality of belt-like bodies 104 is located within the above-described lower end appropriate range that can suppress the upward movement of the lower ends 14A of the plurality of hollow fiber membranes 14 that swing within the corresponding hollow fiber membrane bundle 15. By suppressing the upward movement of the lower ends 14A of the plurality of hollow fiber membranes 14 in the corresponding hollow fiber membrane bundle 15 by the suppression member 100, it is possible to suppress the entanglement of the hollow fiber membranes 14 with each other within the hollow fiber membrane bundle 15.

[0104] [Examples of the Present Invention] Next, examples more specifically showing the present invention will be described.

[0105] (Example 1) As the hollow fiber membrane bundle 15, a single-end free type having a membrane area of 40 m 2 was used. As the hollow fiber membrane 14, a polyvinylidene fluoride-based resin hydrophilized with polyvinyl alcohol was used, having an average pore diameter of 0.02 microns and a vertical length (effective length) L2 of 1035 mm.

[0106] As the suppression member 100, a net-like body made of polypropylene was used. The upper end of the net-like body is fixed to the upper ends 14B of the plurality of hollow fiber membranes 14 in the corresponding hollow fiber membrane bundle 15 and is also fixed to the fixing member 3, and the vertical length L1 of the net-like body is set to 725 mm. In this case, the lower end of the net-like body is positioned within an appropriate lower end range that can suppress the upward movement of the lower end 14A of the hollow fiber membrane 14 and can also suppress the lower end 14A of the hollow fiber membrane 14 from entering the mesh. Also, the ratio (L1 / L2) of the length L1 of the net-like body to the effective length L2 of the hollow fiber membrane 14 is "0.7".

[0107] As the water conduit 5, a cylindrical one with a length of 1090.5 mm and an inner diameter of 48.6 mm was used. The water conduit 5 was arranged at the center of the housing 13 and fixed together with the hollow fiber membrane bundle 15 by the fixing member 3. In this case, the plurality of hollow fiber membrane bundles 15 are arranged so as to surround the water conduit 5. In the water conduit 5, a plurality (a total of 36) of pipe ventilation holes 54 were formed at intervals of 100 mm starting from a position 70 mm below the fixing member 3. The pipe ventilation holes 54 were formed at intervals of 90° in the circumferential direction, and the hole diameter was set to 10 mm.

[0108] The air diffusing member 4 was attached at a position 1060.5 mm below the fixing member 3. The air diffusing member 4 is composed of a disk-shaped main body portion 44 in which a plurality of air diffusing ventilation holes 43 are formed, a gas receiving portion 45, and a peripheral wall portion 47. A gas inlet 8 for the water conduit was provided as a gas supply port to the water conduit 5, and an air diffusing gas inlet 7 was provided as a gas supply port to the gas receiving portion 45 of the air diffusing member 4.

[0109] Using the hollow fiber membrane module 10 configured as described above, with clean water as the raw water, constant flow filtration was performed for 30 seconds under the condition of a flow rate of 4000 L / h by the external pressure total filtration method. Then, after the filtration operation, backwashing was carried out with compressed air at 0.2 MPa from the filtrate side of the hollow fiber membrane module 10, and then bubbling washing was carried out. This operation was repeated 300 times. The flow rate of the air (washing gas) for bubbling on the air diffusing member 4 side was varied in the range of 1500 to 12000 NL / h. The flow rate of the air (washing gas) for bubbling on the water conduit 5 side was kept constant at 10000 NL / h.

[0110] (Example 2) The same procedure as in Example 1 was carried out except that a net-like body with a vertical length L1 of 932 mm was used. In this case, the lower end of the net-like body is located within the appropriate lower end range. Also, the ratio (L1 / L2) of the length L1 of the net-like body to the effective length L2 of the hollow fiber membrane 14 is "0.9".

[0111] (Example 3) The same procedure as in Example 1 was carried out except that a net-like body with a vertical length L1 of 1035 mm was used. In this case, the lower end of the net-like body is located within the appropriate lower end range. Also, the ratio (L1 / L2) of the length L1 of the net-like body to the effective length L2 of the hollow fiber membrane 14 is "1.0".

[0112] (Comparative Example 1) The same procedure as in Example 1 was carried out except that the installation of the net-like body with respect to the hollow fiber membrane bundle 15 was omitted.

[0113] (Comparative Example 2) The same procedure as in Example 1 was carried out except that a net-like body with a vertical length L1 of 518 mm was used. In this case, the lower end of the net-like body is located above the appropriate lower end range. Also, the ratio (L1 / L2) of the length L1 of the net-like body to the effective length L2 of the hollow fiber membrane 14 is "0.5".

[0114] (Comparative Example 3) The same procedure as in Example 1 was carried out except that a net-like body with a vertical length L1 of 1242 mm was used. In this case, the lower end of the net-like body is located below the appropriate lower end range. Also, the ratio (L1 / L2) of the length L1 of the net-like body to the effective length L2 of the hollow fiber membrane 14 is "1.2".

[0115] Regarding the above Examples 1 to 3 and Comparative Examples 1 to 3, the entanglement and damage occurrence status of the hollow fiber membranes 14 within the hollow fiber membrane bundle 15 were visually evaluated. The evaluation results are shown in Table 1. In Table 1, "〇" indicates that there was almost no entanglement or damage occurrence between the hollow fiber membranes 14 within the hollow fiber membrane bundle 15, and stable operation was possible. On the other hand, "×" in Table 1 indicates that the entanglement and damage occurrence between the hollow fiber membranes 14 within the hollow fiber membrane bundle 15 were significantly confirmed, and it became difficult to continue stable operation.

[0116]

Table 1

[0117] As is clear from the results in Table 1, in Examples 1 to 3, within the range where the flow rate of the cleaning gas on the diffuser member 4 side is 1500 to 12000 NL / h, the entanglement and damage occurrence between the hollow fiber membranes 14 within the hollow fiber membrane bundle 15 are suppressed. This is because the reticulated body suppresses the upward movement of the lower ends 14A of the plurality of hollow fiber membranes 14 within the hollow fiber membrane bundle 15, thus restricting the excessive movement of the hollow fiber membranes 14.

[0118] Also, in Examples 1 to 3, the lower end of the reticulated body is located within an appropriate lower end range that can suppress the upward movement of the lower end 14A of the hollow fiber membrane 14 and can also suppress the lower end 14A of the hollow fiber membrane 14 from entering the mesh. It is considered that this regulates the entanglement between the reticulated body and the hollow fiber membrane 14, thereby suppressing the occurrence of damage to the hollow fiber membrane 14.

[0119] On the other hand, in Comparative Example 1, under the condition that the flow rate of the cleaning gas on the diffuser member 4 side is 7000 NL / h or more, the entanglement and damage occurrence between the hollow fiber membranes 14 within the hollow fiber membrane bundle 15 were significantly confirmed. This is because in Comparative Example 1, the installation of the reticulated body was omitted, so the excessive movement of the plurality of hollow fiber membranes 14 within the hollow fiber membrane bundle 15 was not restricted, and upward movement occurred at the lower ends 14A of the plurality of hollow fiber membranes 14.

[0120] In Comparative Example 2, under the condition that the flow rate of the cleaning gas on the side of the air diffusing member 4 is 10,000 NL / h or more, entanglement and damage between the hollow fiber membranes 14 in the hollow fiber membrane bundle 15 were significantly confirmed. This is because in Comparative Example 2, the lower end of the reticulated body is located above the appropriate lower end range that can suppress the upward movement of the lower ends 14A of the plurality of hollow fiber membranes 14 in the hollow fiber membrane bundle 15. For this reason, in Comparative Example 2, under the condition that the flow rate of the cleaning gas on the side of the air diffusing member 4 is 10,000 NL / h or more, the lower ends 14A of the plurality of hollow fiber membranes 14 in the hollow fiber membrane bundle 15 are lifted, and it is considered that entanglement and damage occurred between the hollow fiber membranes 14 accordingly.

[0121] In Comparative Example 3, in the range where the flow rate of the cleaning gas on the side of the air diffusing member 4 is within 1500 to 12000 NL / h, entanglement and damage between the hollow fiber membranes 14 in the hollow fiber membrane bundle 15 were significantly confirmed. This is because in Comparative Example 3, the lower end of the reticulated body is located below the appropriate lower end range that can suppress the entry of the lower end 14A of the hollow fiber membrane 14 into the mesh 101 and is in contact with the air diffusing member 4. For this reason, in Comparative Example 3, the hollow fiber membrane 14 was entangled with the restraining member 100, and the hollow fiber membrane 14 was damaged.

[0122] From the above results, it was found that in the above Examples 1 to 3, compared with Comparative Examples 1 to 3, excessive movement of the hollow fiber membrane 14 in the bubbling process was restricted, and while ensuring the effect of removing floating contaminants attached to the membrane surface of the hollow fiber membrane 14, entanglement and damage between the hollow fiber membranes 14 could be suppressed.

[0123] The embodiments and examples disclosed this time should be construed as illustrative in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and it is intended that all modifications within the meaning and scope equivalent to the scope of claims be included.

Explanation of Reference Numerals

[0124] 2 Gas supply unit 4 Air diffusing member 43 Ventilation holes for air diffusion 44 Main body part 45 Gas receiving part 45A Inlet 46 Dispersion hole 10 Hollow fiber membrane module 13 Housing 14 Hollow fiber membrane 15 Bundle of hollow fiber membranes 100 Suppression member S1 Internal space

Claims

1. A housing in which a fixing member is fixed inside and forms an internal space, A plurality of hollow fiber membrane bundles each having a plurality of hollow fiber membranes, and the plurality of hollow fiber membrane bundles are arranged in the internal space with the upper ends of the plurality of hollow fiber membranes fixed to the fixing member, A gas supply unit for supplying a gas for cleaning the plurality of hollow fiber membrane bundles into the internal space, And a restraining member provided individually for each of the plurality of hollow fiber membrane bundles, The restraining member is fixed to the side surface of the housing with the upper end separated from the fixing member, and in the corresponding hollow fiber membrane bundle, the plurality of hollow fiber membranes are allowed to swing by the gas supplied into the internal space from the gas supply unit, while the lower ends of the plurality of hollow fiber membranes are configured to suppress rising, a hollow fiber membrane module.

2. Each of the restraining members has a plurality of meshes and is constituted by a net-like body extending in the vertical direction so as to cover the side surface of the corresponding hollow fiber membrane bundle, The lower end of each of the restraining members is located at a position where it is possible to suppress the lower ends of the plurality of hollow fiber membranes that swing in the corresponding hollow fiber membrane bundle from rising, and it is also possible to suppress the lower ends of the plurality of hollow fiber membranes from entering the meshes, the hollow fiber membrane module according to claim 1.

3. Each of the restraining members has a function of partitioning between the hollow fiber membrane bundles so that a gap is formed between the plurality of hollow fiber membrane bundles, the hollow fiber membrane module according to claim 1 or 2.

4. The gas supply unit is arranged at a position below the hollow fiber membrane bundle, has a shape that spreads in the radial direction of the hollow fiber membrane bundle, and includes a diffusing member in which a plurality of diffusing ventilation holes are formed at intervals in the radial direction, The diffusing member, A plate-shaped main body portion having a shape that spreads in the radial direction of the hollow fiber membrane bundle and having a plurality of diffusing ventilation holes formed at intervals in the radial direction, A gas receiving portion having a cylindrical shape with one end connected to the lower surface of the main body portion and a gas receiving port formed at the other end side, and having a dispersion hole for guiding the gas accommodated in the cylinder to the diffusing ventilation holes, the hollow fiber membrane module according to any one of claims 1 to 3.

5. The gas receiving portion has a shape in which the inner diameter expands from the one end toward the other end, the hollow fiber membrane module according to claim 4.

6. The diffusing ventilation holes are arranged on a plurality of circumferences spaced apart in the radial direction in the main body portion, The hollow fiber membrane module according to claim 4 or 5, wherein the number of the air diffusing ventilation holes on each of the circumferences satisfies being a multiple of the number of the hollow fiber membrane bundles.

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