Hollow fiber membrane module

Abstract

To provide a hollow fiber membrane module that can suppress damage to the hollow fiber membrane due to contact with the sealant when performing filtration using the hollow fiber membrane module or when cleaning the hollow fiber membrane module. [Solution] A hollow fiber membrane module comprising: a hollow fiber membrane bundle having a plurality of hollow fiber membranes, with one end of each hollow fiber membrane sealed with a sealant; and a fixing member for fixing the other ends of the plurality of hollow fiber membranes in an open state, wherein the hollow fiber membrane bundle is of a one-end free type in which the plurality of hollow fiber membranes are not fixed one by one at one end, the coefficient of dynamic friction between the hollow fiber membranes and the sealant is 0.75 or less, and the sealant contains a resin and additives.

Description

Technical Field

[0001] The present invention relates to a hollow fiber membrane module.

Background Art

[0002] Conventionally, in the field of water treatment such as microfiltration and ultrafiltration, a separation technique using a hollow fiber membrane module in which a plurality of hollow fiber membranes are fixed in a bundle shape is known. In such a technical field, usually, a hollow fiber membrane module of an end-fixed type in which both ends (upper end and lower end) of the hollow fiber bundle are adhesively fixed is often used. However, when using a hollow fiber membrane module of the end-fixed type, there is a concern that as filtration progresses, turbidity components accumulate at the lower end, leading to membrane blockage.

[0003] To solve this problem, for example, it is known that a single-end free type hollow fiber membrane module in which one end of the hollow fiber membrane is open and the other end is in a free state sealed with a sealing agent, as described in Patent Document 1, can be used. In particular, Patent Document 2 discloses a method of suppressing the sealing agent from protruding outside the hollow fiber membrane and maintaining the hollow fiber membranes in a state of contact with each other, reducing the water flow resistance, and improving the effective membrane utilization rate.

[0004] Furthermore, as a method for removing turbidity components accumulated as filtration progresses, a cleaning method by supplying gas is known. For example, Patent Document 3 describes a method in which, in a state where the internal space of a container housing a hollow fiber membrane module is filled with water, gas is supplied and dispersed from below, and the gas rises from the lower end of the hollow fiber membrane to vibrate the hollow fiber membrane, thereby peeling off the turbidity components adhering to the membrane surface.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] In the single-ended hollow fiber membrane modules described in Patent Documents 1 and 2, as mentioned above, a sealant remains on the outside of the hollow fiber membrane. When such a hollow fiber membrane module is used in the manner described in Patent Document 3, there is a problem that the hollow fiber membrane vibrates during the washing or filtration process, causing contact between the hollow fiber membrane and the sealant, and damaging the hollow fiber membrane.

[0007] The present invention has been made in view of these problems, and aims to provide a hollow fiber membrane module that can suppress damage to the hollow fiber membrane due to contact with a sealant when performing filtration using the hollow fiber membrane module or when cleaning the hollow fiber membrane module. [Means for solving the problem]

[0008] As a result of various studies, the inventors have found that the above objective can be achieved by the following invention.

[0009] A hollow fiber membrane module according to one aspect of the present invention comprises a hollow fiber membrane bundle having a plurality of hollow fiber membranes, with one end of each hollow fiber membrane sealed with a sealant, and a fixing member for fixing the other ends of the plurality of hollow fiber membranes in an open state, wherein the hollow fiber membrane bundle is of a one-end free type in which the plurality of hollow fiber membranes are not fixed one by one at one end, the coefficient of dynamic friction between the hollow fiber membranes and the sealant is 0.75 or less, and the sealant contains a resin and additives. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a hollow fiber membrane module that can suppress damage to the hollow fiber membrane due to contact with a sealant when performing filtration using the hollow fiber membrane module or when cleaning the hollow fiber membrane module. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic diagram showing the configuration of a hollow fiber membrane module in Embodiment 1 of the present invention. [Figure 2] Figure 2 is a schematic diagram showing the configuration of a hollow fiber membrane module in Embodiment 2 of the present invention. [Figure 3] Figure 3 is a schematic diagram showing the configuration of a hollow fiber membrane module in Embodiment 3 of the present invention. [Figure 4] Figure 4 is a schematic diagram showing the hollow fiber membrane and protrusions provided in the hollow fiber membrane module in Embodiment 3 of the present invention. [Figure 5] Figure 5 is a schematic diagram of the abrasion test machine used in the evaluation test of the embodiment. [Modes for carrying out the invention]

[0012] The hollow fiber membrane module in this embodiment comprises a bundle of hollow fiber membranes having a plurality of hollow fiber membranes, with one end of each hollow fiber membrane sealed with a sealant, and a fixing member that fixes the other ends of the plurality of hollow fiber membranes in an open state, wherein the bundle of hollow fiber membranes is a one-end free type in which the plurality of hollow fiber membranes are not fixed one by one at one end, the coefficient of dynamic friction between the hollow fiber membranes and the sealant is 0.75 or less, and the sealant contains a resin and additives. With such a configuration, it is possible to provide a hollow fiber membrane module that can suppress damage to the hollow fiber membranes due to contact between the hollow fiber membranes and the sealant when performing filtration using the hollow fiber membrane module or when cleaning the hollow fiber membrane module.

[0013] As long as the hollow fiber membrane module in the present embodiment has the above configuration, other configurations are not particularly limited. However, several embodiments for implementing the present invention will be specifically described below with reference to the drawings.

[0014] <Embodiment 1> The configuration of the hollow fiber membrane module 10 according to Embodiment 1 of the present invention will be described with reference to FIG. 1. FIG. 1 is a schematic diagram showing the configuration of the hollow fiber membrane module 10 in Embodiment 1 of the present invention.

[0015] (Overall configuration) As shown in FIG. 1, the hollow fiber membrane module 10 mainly includes a hollow fiber membrane bundle 12 having a plurality of hollow fiber membranes 11, and a housing 13 in which an internal space for accommodating the hollow fiber membrane bundle 12 is formed. The hollow fiber membrane module 10 is installed in a posture in which the longitudinal direction of the hollow fiber membrane 11 is along the vertical direction (vertical direction).

[0016] In the hollow fiber membrane module 10, the upper end portion of the hollow fiber membrane 11 is fixed by a fixing member 14. The upper end portion of the hollow fiber membrane 11 is open, and this opening communicates with the upper space S2 through a through hole 14a formed in the fixing member 14. On the other hand, the lower end portion of the hollow fiber membrane 11 is blocked by a sealing agent 15, but is not fixed anywhere and is in a free state one by one. As the fixing member 14, a thermosetting resin such as an epoxy resin, an unsaturated polyester resin, or a polyurethane resin can be used. As a method of adhering the hollow fiber membrane bundle 12 and the fixing member 14, there are a centrifugal adhesion method, a static adhesion method, and the like.

[0017] The housing 13 has a sealed structure having a vertically long internal space in the vertical direction. The fixing member 14 in the housing 13 partitions the internal space of the housing 13 into an accommodation space S1 in which the hollow fiber membrane bundle 12 is accommodated and an upper space S2 located above the accommodation space S1.

[0018] (Hollow fiber membrane bundle) The hollow fiber membrane bundle 12 has a plurality of hollow fiber membranes 11, and these plurality of hollow fiber membranes 11 are arranged in a bundle shape. It is preferable that the outer diameter of the hollow fiber membrane bundle 12 is such that a plurality of hollow fiber membranes 11 are arranged in the range of 5 to 200 cm, more preferably 5 to 100 cm, and even more preferably 5 to 50 cm.

[0019] (Hollow fiber membrane) The material of the hollow fiber membrane 11 is not particularly limited. For example, it is preferably 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. Among these, from the viewpoints of membrane strength and chemical resistance, polyvinylidene fluoride (PVDF) is more preferable as the material of the hollow fiber membrane 11.

[0020] When the hollow fiber membrane module has a one-end free structure, the hollow fiber membrane 11 preferably has a certain flexibility in order to swing during physical cleaning (bubbling cleaning). Specifically, the elongation of the hollow fiber membrane 11 is not particularly limited, but it is preferably 20% or more. When the elongation of the hollow fiber membrane 11 is 20% or more, the hollow fiber membrane 11 can maintain sufficient strength even when vibrating during physical cleaning, and the breakage of the hollow fiber membrane 11 can be suppressed. Also, the upper limit value of the elongation of the hollow fiber membrane 11 is not particularly limited, but for example, it may be less than 500%.

[0021] The effective length of the hollow fiber membrane 11 is preferably 0.3m to 2.5m, more preferably 0.3m to 2.0m, and even more preferably 0.3m to 1.8m. By having a hollow fiber membrane 11 of 0.3m or more, the relative ratio of the sealing area by the sealing agent 15 does not increase too much, and the effective length of the hollow fiber membrane 11 does not become too short, thereby ensuring a sufficient treatment flow rate. Furthermore, by having an effective length of 2.5m or less, the hollow fiber membranes 11 are less likely to entangle with each other, improving the turbidity discharge performance.

[0022] The outer diameter of the hollow fiber membrane 11 is not particularly limited, but is preferably 0.5 mm or more and less than 5.0 mm, more preferably 0.5 mm or more and less than 4.0 mm, and even more preferably 0.5 mm or more and less than 3.0 mm.

[0023] (Sealant) Each hollow fiber membrane 11 is individually sealed with a sealant 15 at one end (lower end). In the longitudinal direction of the hollow fiber membrane 11, it is preferable to seal the portion from 5 mm to 1000 mm from the lower end of the hollow fiber membrane 11 with the sealant 15, and more preferably from 5 mm to 500 mm. By sealing the portion from which the sealant 15 is applied to the hollow fiber membrane 11 up to 1000 mm from the lower end, the effective length of the hollow fiber membrane 11 is not shortened too much, and a decrease in processing flow rate can be suppressed. On the other hand, by sealing the portion from which the sealant 15 is applied to the portion from which the hollow fiber membrane 11 is applied to the lower end, the anchoring effect of the sealant is excellent, resulting in superior durability.

[0024] The coefficient of dynamic friction between the hollow fiber membrane 11 and the sealant 15 shall be 0.75 or less. By having a coefficient of dynamic friction between the hollow fiber membrane 11 and the sealant 15 of 0.75 or less, when filtration is performed using the hollow fiber membrane module 10 and when the hollow fiber membrane module 10 is cleaned, the friction generated when the hollow fiber membrane 11 shakes and the hollow fiber membrane 11 and the sealant 15 come into contact and separate can be reduced, and damage to the hollow fiber membrane 11 can be prevented. The coefficient of dynamic friction between the hollow fiber membrane 11 and the sealant 15 is preferably 0.60 or less, and more preferably 0.50 or less. On the other hand, the lower limit of the coefficient of dynamic friction between the hollow fiber membrane 11 and the sealant 15 is not particularly limited, and the lower the better, but it may be 0.25 or more for industrial reasons.

[0025] The coefficient of dynamic friction between the hollow fiber membrane 11 and the sealant 15 is the value obtained by measuring the coefficient of dynamic friction of the sealant relative to the hollow fiber membrane in accordance with JIS K 7125. Specifically, as described in the examples below, the hollow fiber membrane is evenly arranged on the base side and the sealant is placed on the sliding side for measurement.

[0026] The encapsulant 15 is not particularly limited as long as it contains a resin and additives and the coefficient of dynamic friction between the hollow fiber membrane 11 and the encapsulant 15 is 0.75 or less. By having the encapsulant 15 contain a resin and additives and the coefficient of dynamic friction between the hollow fiber membrane 11 and the encapsulant 15 is 0.75 or less, it is possible to suppress damage to the hollow fiber membrane 11 due to contact between the hollow fiber membrane 11 and the encapsulant 15 during filtration and washing, etc.

[0027] The resin is not particularly limited, but it is preferable to include at least one thermosetting resin selected from the group consisting of epoxy resins, unsaturated polyester resins, and polyurethane resins. It is more preferable that the resin includes a polyurethane resin. Furthermore, it is preferable that the resin further includes a curing agent. In other words, it is preferable that the resin is a two-component thermosetting resin (thermosetting resin + curing agent).

[0028] The aforementioned additive is not particularly limited, but it is preferable that it contains at least one selected from the group consisting of kaolin, talc, molybdenum disulfide, and starch. Furthermore, it is more preferable that the aforementioned additive contains at least one of kaolin and talc.

[0029] The weight ratio of the hollow fiber membrane 11 at the end sealed by the sealant 15 to the sealant 15 is preferably 1:2.2 to 1:5. More preferably, the weight ratio of the hollow fiber membrane 11 at the end sealed by the sealant 15 to the sealant 15 is 1:2.2 to 1:3. By ensuring that the weight of the sealant 15 is 5 times or less the weight of the hollow fiber membrane 11 at the end sealed by the sealant 15, the outer diameter of the sealed portion does not become too large. As a result, the hollow fiber membrane 11 does not shake during filtration and washing, and the contact area with the sealant 15 when it moves is reduced, thus suppressing the possibility of damage to the hollow fiber membrane 11. In addition, the sealed portion is less likely to cause snagging and entanglement of the hollow fiber membranes 11 with each other, thus reducing the frequency of contact with the sealant 15. Furthermore, the number of hollow fiber membranes 11 that can be relatively contained within the module is not reduced too much, ensuring a sufficient processing flow rate. On the other hand, if the weight of the sealant 15 is 2.2 times or more than that of the hollow fiber membrane 11 at the end sealed by the sealant 15, the anchoring effect of the sealant 15 is achieved, and excellent durability can be obtained.

[0030] Furthermore, it is preferable that the weight ratio of the hollow fiber membrane 11 at the end sealed by the sealant 15 to the resin is 1:1.5 to 1:4.0, and the weight ratio of the hollow fiber membrane 11 at the end sealed by the sealant 15 to the additive is 1:0.7 to 1:1. It is even more preferable that the weight ratio of the hollow fiber membrane 11 at the end sealed by the sealant 15 to the resin is 1:1.5 to 1:2.0, and the weight ratio of the hollow fiber membrane 11 at the end sealed by the sealant 15 to the additive is 1:0.7 to 1:0.9. By ensuring that the weight of the resin is four times or less the weight of the hollow fiber membrane 11 at the end sealed by the sealant 15, and that the weight of the additive is one time or less the weight of the hollow fiber membrane 11 at the end sealed by the sealant 15, the outer diameter of the sealed portion does not become too large. As a result, the hollow fiber membrane 11 does not shake during filtration and washing, and the contact area with the sealant 15 when it moves is reduced, thus suppressing the possibility of damage to the hollow fiber membrane 11. Furthermore, the sealed portion does not cause the hollow fiber membranes 11 to become entangled with each other, reducing the frequency of contact with the sealant 15. In addition, the number of hollow fiber membranes 11 that can be relatively contained within the module is not reduced too much, ensuring a sufficient processing flow rate. On the other hand, by ensuring that the weight of the resin is 1.5 times or more the weight of the hollow fiber membrane 11 at the end sealed by the sealant 15, and that the weight of the additive is 0.7 times or more the weight of the hollow fiber membrane 11 at the end sealed by the sealant 15, the anchoring effect of the sealant 15 is achieved, resulting in excellent durability.

[0031] The method for mixing the resin and the additive contained in the sealing agent 15 is not particularly limited, but for example, one method is to first seal the hollow fiber membrane 11 with the resin alone, and then add the additive on top of that to seal the hollow fiber membrane 11, thereby mixing the resin and the additive. The method for mixing the resin and the additive can be appropriately adjusted so that the coefficient of dynamic friction between the hollow fiber membrane 11 and the sealing agent 15 is 0.75 or less.

[0032] The shape of the sealant 15 is not particularly limited, but a shape without corners is preferred. This prevents the sealant 15 from cutting or damaging the hollow fiber membrane 11 when it comes into contact with it.

[0033] (Method for sealing hollow fiber membranes) The method for sealing the lower end of the hollow fiber membrane 11 (the method for filling with the sealant 15) is not particularly limited, but examples include filling the hollow fiber membrane 11 with the sealant 15 by capillary action, filling the hollow fiber membrane 11 by allowing the sealant 15 to flow towards the hollow fiber membrane module side by its own weight, filling the hollow fiber membrane 11 by applying centrifugal force to the sealant 15, and filling the hollow fiber membrane 11 by pressing the sealant 15. By such methods, the inside and outside of the hollow fiber membrane 11 can be sealed.

[0034] A specific example of a method for filling the hollow fiber membrane 11 with a sealant 15 by capillary action is as follows: First, the opening of the hollow fiber membrane 11 is immersed in uncured resin. At this time, the resin is filled into the interior by utilizing the fact that the resin rises up between the hollow fiber membrane 11 due to surface tension. The filling of the hollow fiber membrane 11 with resin can be done by adjusting the pressure from the opening side opposite to the side to be sealed. The amount of resin filled can be adjusted by adjusting the pressure, and in particular, the amount of resin filled can be increased by suction from the opening side opposite to the side to be sealed. After filling the inside of the hollow fiber membrane with resin as described above, the lower end of the hollow fiber membrane 11 can be sealed by adding an additive to cover the resin on the outside of the hollow fiber membrane and curing it.

[0035] A specific example of a method for filling the hollow fiber membrane 11 by allowing the sealing agent 15 to flow into the hollow fiber membrane module by its own weight is as follows: First, a bundle of open hollow fiber membranes 11 is fixed to a container with a hole in the bottom so as to leave no gaps. Next, another container with a hole is prepared, and the holes of the two containers are connected with a tube. The container without the hollow fiber membrane is placed at a high position, and uncured resin is placed in this container, so that the resin moves to the container with the hollow fiber membrane 11 fixed by its own weight, and the inside of the hollow fiber membrane 11 is filled with resin. After the resin has been filled inside the hollow fiber membrane 11 as described above, an additive is added to cover the resin on the outside of the hollow fiber membrane 11, and the lower end of the hollow fiber membrane 11 can be sealed by curing the additive.

[0036] A specific example of a method for filling the hollow fiber membrane 11 by applying centrifugal force to the sealant 15 is as follows: First, the opening of the hollow fiber membrane 11 is immersed in uncured resin. Next, centrifugal force is applied to fill the hollow fiber membrane 11 with resin. After filling the inside of the hollow fiber membrane 11 with resin as described above, an additive is added to cover the resin on the outside of the hollow fiber membrane 11, and the lower end of the hollow fiber membrane 11 can be sealed by curing the additive.

[0037] The method of filling the hollow fiber membrane 11 with the sealant 15 by pressure can be specifically described as follows: First, the bundle of hollow fiber membranes 11 is held in an extended position. With the opening of the hollow fiber membrane 11 facing downwards, the hollow fiber membrane 11 is lowered using a drive source such as a motor and introduced into a container containing uncured resin. The pressure applied at that time fills the inside of the hollow fiber membrane 11 with resin. After filling the inside of the hollow fiber membrane 11 with resin as described above, an additive is added to cover the resin on the outside of the hollow fiber membrane 11 and cured, thereby sealing the lower end of the hollow fiber membrane 11.

[0038] (Filtration operation and cleaning of hollow fiber membrane modules) At the lower end of the housing 13, a raw water pipe 22 to which a pump 21 supplying raw water is connected, and an air pipe 26 to which a compressor 25 supplying compressed air is connected are connected. The raw water pipe 22 and the air pipe 26 are connected separately to the housing 13. Alternatively, the raw water pipe 22 and the air pipe 26 may be connected to each other to form a single pipe, which is then connected to the lower end of the housing 13.

[0039] By opening the on-off valve 22a provided in the raw water piping 22, raw water is introduced into the containment space S1. In the hollow fiber membrane module 10, the raw water introduced into the containment space S1 is filtered by permeating from the outside to the inside of the hollow fiber membrane 11. That is, the hollow fiber membrane module 10 of this embodiment is configured as an external pressure filtration type hollow fiber membrane module in which pressure is applied to the hollow fiber membrane 11 from the outside. In this embodiment, a configuration is adopted in which the outside of the hollow fiber membrane 11 is actively pressurized, but this is not the only configuration. With the hollow fiber membrane module 10 of this embodiment, it is possible to suppress damage to the hollow fiber membrane 11 due to contact between the hollow fiber membrane 11 and the sealant 15 during the raw water filtration operation.

[0040] By opening the on-off valve 26a provided in the air piping 26, compressed air for bubbling cleaning is introduced into the containment space S1. The air rising from the lower end of the hollow fiber membrane 11 to the boundary between the containment space S1 and the upper space S2 located above the containment space S1 causes the hollow fiber membrane 11 to vibrate, and this action causes suspended pollutants attached to the membrane surface to peel off. With the hollow fiber membrane module 10 in this embodiment, it is possible to suppress damage to the hollow fiber membrane 11 due to contact between the hollow fiber membrane 11 and the sealant 15 during bubbling cleaning.

[0041] The housing 13 is provided with a raw water discharge section 28 that communicates with the containment space S1. A return pipe 29 is connected to this discharge section 28 to return the raw water to the raw water supply destination. The housing 13 is also provided with a filtered water discharge section 31 that communicates with the upper space S2. A filtered water delivery pipe 32 is connected to this discharge section 31. A back pressure pipe 34 for back pressure washing is connected to the filtered water delivery pipe 32, and compressed air can be sent into the upper space S2 from a compressor 35 connected to the back pressure pipe 34.

[0042] <Embodiment 2> Next, a hollow fiber membrane module according to Embodiment 2 of the present invention will be described. The hollow fiber membrane module according to Embodiment 2 basically has the same configuration as Embodiment 1 described above, but it differs in that it further includes a gas dispersing member 40 for dispersing gas in the internal space (containment space S1) in which the hollow fiber membrane bundle 12 is housed. Below, only the differences from Embodiment 1 described above will be explained.

[0043] As shown in Figure 2, the hollow fiber membrane module 10A in Embodiment 2 further includes a diffuser member 40 in addition to the hollow fiber membrane bundle 12 and housing 13. Furthermore, a gas supply unit 26A for supplying gas to the containment space S1 is provided at the lower end of the housing 13. One end of the air pipe 26 is connected to this gas supply unit 26A.

[0044] The aeration member 40 is positioned below the lower end of the hollow fiber membrane 11 (in the space below the containment space S1). The aeration member 40 has a shape that extends radially from the hollow fiber membrane bundle 12, and its peripheral edge is located radially outward from the hollow fiber membrane bundle 12. The aeration member 40 has multiple aeration vents formed radially spaced apart to disperse gas within the housing 13.

[0045] With the aeration member 40, during physical cleaning (bubbling cleaning), the gas supplied from the gas supply unit 26A into the housing 13 can be temporarily contained below the lower end of the hollow fiber membrane 11, and then dispersed toward the containment space S1 through the aeration vent. At this time, an upward bubble flow is generated in the containment space S1 along the longitudinal direction of the hollow fiber membrane 11. As a result, the gas can be dispersed over a wide area in the radial direction of the hollow fiber membrane bundle 12, and the hollow fiber membrane bundle 12 can be uniformly bubbling cleaned in the radial direction. During this cleaning, the hollow fiber membrane 11 vibrates, and the hollow fiber membrane 11 and the sealant 15 come into contact with each other, but with the hollow fiber membrane module 10A, damage to the hollow fiber membrane 11 due to contact with the sealant 15 can be suppressed.

[0046] <Embodiment 3> Next, a hollow fiber membrane module according to Embodiment 3 of the present invention will be described. The hollow fiber membrane module according to Embodiment 3 basically has the same configuration as Embodiment 1 and Embodiment 2 described above, but differs in that it further includes a protruding portion. Below, only the differences from Embodiment 1 and Embodiment 2 will be described.

[0047] As shown in Figures 3 and 4, in the hollow fiber membrane module 10B of Embodiment 3, each end of the hollow fiber membrane 11 is individually sealed with a sealant 15, and the sealant 15 protrudes to the outside of the hollow fiber membrane 11, so that a protruding portion 16 is provided at one end of the hollow fiber membrane 11, protruding from the outer surface of the hollow fiber membrane 11. That is, the protruding portion 16 is provided integrally with the sealant 15 that seals the end of the tubular hollow fiber membrane 11. The protruding portion 16 is positioned to contact a protruding portion provided on an adjacent hollow fiber membrane. Because the protruding portion 16 is provided at the lower end of the hollow fiber membrane 11, the protruding portions 16 come into contact with each other, thus preventing the hollow fiber membranes from remaining in contact with each other. By preventing the hollow fiber membranes from remaining in contact with each other, the effective utilization rate of the membrane can be increased, and furthermore, the turbidity discharge performance can also be improved.

[0048] The width of the protrusion 16 is greater than the width of the hollow fiber membrane 11. Specifically, the ratio of the maximum width (Dmax) of the protrusion 16 to the outer diameter (OD) of the hollow fiber membrane 11 is preferably greater than 1 and less than 3. If the ratio Dmax / OD is 3 or more, the width at one end of the hollow fiber membrane bundle 12 will differ too much from the other, which may cause problems such as the hollow fiber membrane 11 bending or breaking during physical cleaning.

[0049] The length of the protrusions 16 in the longitudinal direction of the hollow fiber membrane 11 is preferably 0.05 cm to 15 cm. If the protrusions 16 are too long, the effective length of the hollow fiber membrane 11 will be shortened, resulting in a decrease in the processing flow rate. On the other hand, if the protrusions 16 are too short, the anchoring effect of the sealant 15 constituting the protrusions 16 will decrease, resulting in a decrease in durability.

[0050] The shape of the protrusion 16 is not particularly limited, but a shape without corners is preferred. This prevents the protrusion 16 from cutting or damaging the hollow fiber membrane 11, even if it comes into contact with it.

[0051] <Applications of hollow fiber membrane modules> The hollow fiber membrane module according to the embodiment of the present invention described above can be incorporated into a water treatment system and used for various applications such as water purification, drinking water production, industrial water production, and wastewater treatment. An example of a water treatment method using the water treatment system is a method that includes a filtration step of filtering the liquid to be treated using the hollow fiber membrane, a backwashing step of washing the hollow fiber membrane with backflow, and a bubbling step of washing the hollow fiber membrane with bubbling, and the filtration step, backwashing step and bubbling step are repeated.

[0052] As described above, this specification discloses various aspects of technology, the main technologies among them are summarized below.

[0053] A hollow fiber membrane module according to a first aspect of the present invention comprises a hollow fiber membrane bundle having a plurality of hollow fiber membranes, with one end of each hollow fiber membrane sealed with a sealant, and a fixing member for fixing the other ends of the plurality of hollow fiber membranes in an open state, wherein the hollow fiber membrane bundle is of a one-end free type in which the plurality of hollow fiber membranes are not fixed one by one at one end, the coefficient of dynamic friction between the hollow fiber membranes and the sealant is 0.75 or less, and the sealant contains a resin and additives.

[0054] A hollow fiber membrane module according to a second aspect of the present invention is a hollow fiber membrane module according to a first aspect, wherein the resin comprises at least one thermosetting resin selected from the group consisting of epoxy resin, unsaturated polyester resin, and polyurethane resin.

[0055] A hollow fiber membrane module according to a third aspect of the present invention is a hollow fiber membrane module according to a first or second aspect, wherein the additive includes at least one selected from the group consisting of kaolin, talc, molybdenum disulfide, and starch.

[0056] A hollow fiber membrane module according to a fourth aspect of the present invention comprises, in any of the first to third aspects of the hollow fiber membrane module, a housing having an internal space in which the hollow fiber membrane bundle is housed, a gas supply unit for supplying gas to the internal space, and a gas dispersing member for dispersing gas in the internal space.

[0057] A hollow fiber membrane module according to a fifth aspect of the present invention is a hollow fiber membrane module according to any of the first to fourth aspects, wherein the weight ratio of the hollow fiber membrane at the end sealed with the sealant to the sealant is 1:2.2 to 1:5.

[0058] A hollow fiber membrane module according to a sixth aspect of the present invention is a hollow fiber membrane module according to any of the first to fifth aspects, wherein the weight ratio of the hollow fiber membrane at the end sealed with the sealant to the resin is 1:1.5 to 1:4.0, and the weight ratio of the hollow fiber membrane at the end sealed with the sealant to the additive is 1:0.7 to 1:1.

[0059] A hollow fiber membrane module according to a seventh aspect of the present invention is a hollow fiber membrane module according to any of the first to sixth aspects, wherein each of the plurality of hollow fiber membranes is provided with a projection that protrudes from the outer surface of the hollow fiber membrane, and the projection is positioned to contact a projection provided on an adjacent hollow fiber membrane.

[0060] The hollow fiber membrane module according to the eighth aspect of the present invention is the hollow fiber membrane module according to the seventh aspect, wherein the protruding portion has a shape without corners. [Examples]

[0061] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0062] (Example 1) First, a hollow fiber membrane with an effective length of 200 mm and an outer diameter (OD) of 1.25 mm was fabricated. The composition of this hollow fiber membrane is polyvinylidene fluoride (PVDF). Next, a sealant was filled into the hollow fiber membrane by pressure. Specifically, the lower end of the hollow fiber membrane was sealed with a two-component polyurethane resin, and then talc was applied on top and hardened to obtain a hollow fiber membrane sealed with a sealant. At this time, the portion of the hollow fiber membrane up to 50 mm from the lower end was sealed with the sealant. That is, the lower end of the hollow fiber membrane in Example 1 (the portion up to 50 mm from the lower end) is sealed with a two-component polyurethane resin and talc. The upper end of the hollow fiber membrane in Example 1 is open, and the effective length of the hollow fiber membrane is 150 mm.

[0063] As the two-component polyurethane resin, Tosoh Corporation's Coronate 4403 (main component) and Nipponan 4221 (curing agent) were used. The resin was applied in a weight ratio of (hollow fiber membrane at the sealed end):(resin + talc) = 1:2.2. Furthermore, the coefficient of dynamic friction between the hollow fiber membrane body and the sealant was 0.55.

[0064] (Example 2) Using the same hollow fiber membrane as in Example 1, a sealant was pressed into the hollow fiber membrane. Specifically, the lower end of the hollow fiber membrane was sealed with a two-component polyurethane resin, and kaolin was applied on top and hardened to obtain a hollow fiber membrane sealed with a sealant. At this time, the portion of the hollow fiber membrane up to 50 mm from the lower end was sealed with the sealant. That is, the lower end of the hollow fiber membrane in Example 2 (the portion 50 mm from the lower end) is sealed with a two-component polyurethane resin and kaolin. The upper end of the hollow fiber membrane in Example 2 is open, and the effective length of the hollow fiber membrane is 150 mm.

[0065] As the two-component polyurethane resin, the same two-component polyurethane resin used in Example 1 was used. The resin was applied in a weight ratio of (hollow fiber membrane at the sealed end):(resin + kaolin) = 1:2.2. The coefficient of dynamic friction between the hollow fiber membrane body and the sealant was 0.55.

[0066] (Comparative Example 1) Using the same hollow fiber membrane as in Example 1, a sealant was pressed into the hollow fiber membrane. Specifically, the lower end of the hollow fiber membrane was sealed with a two-component polyurethane resin and solidified to obtain a hollow fiber membrane sealed with the sealant. At this time, the sealant was applied to a portion of the hollow fiber membrane up to 50 mm from the lower end. That is, the lower end of the hollow fiber membrane in Comparative Example 1 (the portion 50 mm from the lower end) is sealed with a two-component polyurethane resin. The upper end of the hollow fiber membrane in Comparative Example 1 is open, and the effective length of the hollow fiber membrane is 150 mm.

[0067] As the two-component polyurethane resin, the same two-component polyurethane resin used in Example 1 was used. The resin was applied in a weight ratio of (hollow fiber membrane at the sealed end):(resin) = 1:1.5. The coefficient of dynamic friction between the hollow fiber membrane body and the sealant was 0.77.

[0068] (Measurement of the coefficient of kinetic friction) In Example 1, Example 2, and Comparative Example 1, the coefficient of dynamic friction between the hollow fiber membrane body and the sealant was measured in accordance with JIS K 7125, with the hollow fiber membrane evenly distributed on the base side and the sealant placed on the sliding side.

[0069] Specifically, first, an aluminum plate (65mm x 65mm, 3mm thick, 34.3g in weight) was prepared as a sliding piece, and the sealant was placed on the aluminum plate. More specifically, in Example 1, a two-component polyurethane resin (11.78g) was applied to the sliding piece, and talc was sprinkled evenly on top and hardened to form the sealant (resin + talc: 12.86g). In Example 2, a two-component polyurethane resin (11.78g) was applied to the sliding piece, and kaolin was sprinkled evenly on top and hardened to form the sealant (resin + kaolin: 12.41g). In Comparative Example 1, the sealant was placed by applying a two-component polyurethane resin (11.78g) to the sliding piece.

[0070] Next, an aluminum plate (100mm x 200mm, 3mm thick, weighing 162.4g) was prepared as a base. Then, the hollow fiber membranes were placed on the base parallel to the long side of the base without any gaps and secured with double-sided tape (total weight 170.5g).

[0071] As the testing machine, an INSTRON 5966 universal material testing machine was used, and the dynamic friction coefficient between the hollow fiber membrane body and the sealant was measured in accordance with JIS K 7125 under the following test conditions: test speed: 100 mm / min, thread weight: 200 gf, test environment: 23℃±2℃·50%RH±10%RH, and number of measurements: n=3.

[0072] (Evaluation test) In the hollow fiber membranes of Example 1, Example 2, and Comparative Example 1 (hollow fiber membranes sealed with a sealant), the portion sealed with the sealant and the hollow fiber membrane body not sealed with the sealant (outer diameter (OD): 1.25 mm, material: PVDF) were brought into contact 1 million times, and the condition of the hollow fiber membrane body after contact was observed. For the evaluation test, a scraping test machine 100 as shown in Figure 5 was used.

[0073] Specifically, an unsealed hollow fiber membrane 110 was fixed to the stationary side 101, and the hollow fiber membranes 120 (sealed with an agent) of Example 1, Example 2, and Comparative Example 1 were fixed to the driving side 102. A core rod 111 was inserted into the hollow fiber membrane 110 on the stationary side 101 to prevent breakage. The hollow fiber membrane 110 on the stationary side 101 was fixed by placing 0.6g weights 112 on both sides, and the hollow fiber membrane 120 on the driving side 102 was fixed on one side to the agitator 121 of the driving mechanism, and on the other side, a pulley 122 was passed through to allow smooth movement, and a weight 123 was attached to apply tension and fix it in place. At the contact point 103, the hollow fiber membrane 110 on the stationary side 101 was positioned above, and the hollow fiber membrane 120 on the driving side 102 was positioned below.

[0074] The hollow fiber membrane 120 on the drive side 102 was driven by a stirrer 121. As it rotated, the hollow fiber membrane 120 on the drive side 102 moved approximately 7 mm back and forth and came into contact with the hollow fiber membrane 110 on the stationary side 101. At this time, since the hollow fiber membrane 120 was sealed with a sealant for 50 mm from the bottom end, only the portion of the hollow fiber membrane 120 sealed with the sealant came into contact with the hollow fiber membrane 110. In other words, even though the hollow fiber membrane 120 moved approximately 7 mm back and forth, the portion of the hollow fiber membrane 120 not sealed with the sealant did not come into contact with the hollow fiber membrane 110 on the stationary side 101. The rotation speed of the stirrer 121 was set to 450 rpm, and the portion of the hollow fiber membrane 110 on the stationary side 101 and the portion of the hollow fiber membrane 120 on the drive side 102 sealed with the sealant came into contact 1 million times. The reason for setting the number of contacts at 1 million is that, in actual use, physical cleaning results in approximately 5,760 contacts per day, which is equivalent to a usage period of six months.

[0075] Furthermore, to simulate actual usage conditions, the tests were conducted by supplying water to both the hollow fiber membrane 110 on the fixed side 101 and the hollow fiber membrane 120 on the drive side 102 to create a wet state.

[0076] The test results showed that in Examples 1 and 2, the hollow fiber membrane did not rupture even after 1 million contacts between the hollow fiber membrane and the portion sealed with the sealant. On the other hand, in Comparative Example 1, the hollow fiber membrane ruptured after 1 million contacts between the hollow fiber membrane and the sealant.

[0077] These results indicate that the dynamic friction coefficient between the hollow fiber membrane and the sealant is 0.75 or less, and that the sealant contains resin and additives, thereby suppressing damage to the hollow fiber membrane due to contact with the sealant. [Explanation of symbols]

[0078] 10 Hollow fiber membrane modules 11 Hollow fiber membrane 12 Hollow fiber membrane bundle 13 Housing 14 Fixing member 15. Sealing agent 16 Protrusion 21 pumps 22 Raw water piping 25 Compressor 26 Air Piping 28. Raw water discharge section 29 Return tube 31. Discharge section of filtered water 32 Delivery pipe 34 Reverse pressure pipe 35 Compressor 100 Abrasion Testing Machine

Claims

1. A bundle of hollow fiber membranes having multiple hollow fiber membranes, with one end of each hollow fiber membrane sealed with a sealant, The system comprises a fixing member for fixing the other ends of the plurality of hollow fiber membranes in an open state, The hollow fiber membrane bundle is of the one-end free type, in which the plurality of hollow fiber membranes are not fixed one by one at one end. The coefficient of dynamic friction between the hollow fiber membrane and the sealant is 0.75 or less. A hollow fiber membrane module in which the sealing agent comprises a resin and additives.

2. The hollow fiber membrane module according to claim 1, wherein the resin comprises at least one thermosetting resin selected from the group consisting of epoxy resin, unsaturated polyester resin, and polyurethane resin.

3. The hollow fiber membrane module according to claim 1, wherein the additive comprises at least one selected from the group consisting of kaolin, talc, molybdenum disulfide, and starch.

4. A housing having an internal space formed in which the hollow fiber membrane bundle is housed, A gas supply unit that supplies gas to the internal space, The hollow fiber membrane module according to claim 1, comprising a gas dispersing member for dispersing gas in the internal space.

5. The hollow fiber membrane module according to claim 1, wherein the weight ratio of the hollow fiber membrane at the end sealed with the sealant to the sealant is 1:2.2 to 1:

5.

6. The weight ratio of the hollow fiber membrane at the end sealed with the sealant to the resin is 1:1.5 to 1:4.0, and The hollow fiber membrane module according to claim 1, wherein the weight ratio of the hollow fiber membrane at the end sealed with the sealant to the additive is 1:0.7 to 1:

1.

7. Each of the aforementioned hollow fiber membranes is provided with a protruding portion that extends from the outer surface of the hollow fiber membrane. The hollow fiber membrane module according to claim 1, wherein the protrusion is positioned to contact a protrusion provided on an adjacent hollow fiber membrane.

8. The hollow fiber membrane module according to claim 7, wherein the protruding portion has a shape without corners.

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