JP2010119959A - Hollow fiber membrane module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hollow fiber membrane module which efficiently prevents adhesion or deposition of suspended substances to or on hollow fiber membranes, is provided with durability by obtaining an excellent air-scrubbing effect and at the same time lessening the impact to the hollow fiber membranes in membrane face washing by bubbles or the like, keeps high filtration flow speed especially in water treatment containing suspended substances at a high concentration, and has stable filtration capability for a long time. <P>SOLUTION: The hollow fiber membrane module comprises hollow fiber membrane element, wherein the hollow fiber membrane element has a plurality of hollow fiber membrane bundles which are gathered and fixed in a rectangular case with an adhesive while at least one end of hollow fiber membranes is opened, which have a length d of 1 to 5 cm in the longitudinal direction of the case, and which satisfy the relation 1/20≤s/d≤1/1 wherein s is the interval between hollow fiber membrane bundles in the longitudinal direction of the case and d is the length of the hollow fiber membrane bundles. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hollow fiber membrane module for water treatment. More specifically, it effectively prevents the suspended matter from adhering to and accumulating on the hollow fiber membrane, providing an excellent air scrubbing effect when cleaning the membrane surface with bubbles and reducing the impact on the hollow fiber membrane. In order to improve the durability of the hollow fiber membrane module, a hollow fiber membrane module that maintains a high filtration flow rate and has stable filtration performance for a long period of time, particularly in water treatment containing a high concentration of suspended solids. It is to provide.

  In recent years, the development of separation technology using hollow fiber membranes made of polymer materials has progressed, and hollow fiber membrane modules are widely used in various applications such as water purification treatment, industrial wastewater treatment, and sewage treatment. Among them, in particular, in recent years, hollow fiber membrane modules have been used for water treatment containing suspended solids of high concentration such as sewage treatment. This is generally called a membrane separation activated sludge method.

  In general, filtration with a submerged hollow fiber membrane used for drainage uses membrane separation as compared with a general precipitation method, so that the quality of treated water is good and the treated water can be reused. Moreover, the quality of treated water is better when the hollow fiber membrane to be used is the ultrafiltration membrane (UF membrane) than the microfiltration membrane (MF membrane). In general, an MF membrane is often used.

  On the other hand, in water treatment using a hollow fiber membrane module containing high-concentration suspended material, the suspended material adheres and accumulates on the surface of the hollow fiber membrane over time, resulting in an increase in transmembrane pressure difference. The filtration performance was lowered, and in particular, there was a tendency for many suspended substances to adhere and accumulate at the roots of the hollow fiber membranes near the dense part of the membrane bundle or the fixed part.

  In order to suppress the adhesion and accumulation of suspended substances due to such filtration, an air diffuser that generates bubbles or the like is usually provided below the hollow fiber membrane module. Bubbles generated from the air diffuser become a gas-liquid mixed flow, vibrates the membrane surface, peels and cleans the suspended matter adhering to and depositing on the hollow fiber membrane, and obtains an air scrubbing effect.

  However, if excessive air bubbles are generated from the air diffuser to prevent the adhering of a large amount of suspended matter, the impact on the hollow fiber membrane bundle becomes large, especially the burden on the membrane bundle near the lower end is large, In the worst case, it causes damage to the membrane.

  Furthermore, the larger the hollow fiber membrane module is, or the higher the flow rate of the raw water is, the more noticeably the suspended matter adheres and accumulates and the filtration performance decreases.

The hollow fiber membrane has a fine particle diameter of 1 to 10 μm and a pure water permeation rate of 30000 L / m ² / hr / 100 kPa or more, and the hollow fiber membrane has a pore diameter larger than that of a general UF / MF membrane. While it was large and had high filtration performance, there was a significant tendency for a large amount of suspended matter to adhere to and accumulate on the root of the hollow fiber membrane in the vicinity of the fixed part.

  The U-shaped hollow fiber membrane is fixed in the housing by a fixing member while maintaining its end in an open state, and filtration is performed by making the shape of the cross-section perpendicular to the hollow fiber membrane of the fixing member into a substantially rectangular shape. At this time, it is known that the hollow fiber membranes in the module are not easily fixed and integrated, and the recovery function of the filtration function which has been lowered by use can be easily and efficiently implemented. (For example, refer to Patent Document 1).

  In addition, a plurality of sheet-like hollow fiber membrane elements obtained by arranging a large number of porous hollow fiber membranes in parallel are arranged in parallel at predetermined intervals with the fiber direction of the porous hollow fibers perpendicular. The hollow fiber membrane module is arranged below the hollow fiber membrane module, emits microbubbles toward the lower end of the hollow fiber membrane module, and moves up and down between the internal space and the external space of the hollow fiber membrane module. An air diffuser for generating a gas-liquid mixed flow swirling in a direction, and this membrane filtration unit includes a part of the mixed flow between the porous hollow fiber membranes of the hollow fiber membrane module and a sheet-like hollow fiber. By forming a forced flow between the membrane elements, and removing the residue mixed in the gas-liquid mixed flow from the hollow fiber membrane module and having a residue removal mechanism, hair and fibers in the waste water, Bundles of film such as paper pieces and entanglement or entanglement with frame materials To prevent hunting, it is known that can secure durability. (For example, refer to Patent Document 2).

Prior art documents related to the present invention include the following.
JP-A-5-220356 JP 2007-152179 A JP 2005-125198 A

However, in Patent Document 1, there is a tendency that suspended substances accumulate in a dense portion near the fixed portion of the hollow fiber membrane as the elapsed time of filtration increases.
Further, in Patent Document 2, the hollow fiber membrane bundle in the hollow fiber membrane element is divided into three. However, because the divided space is wide, the suspended matter held inside the hollow fiber membrane can be sufficiently discharged. It is difficult, and it is difficult to equally alleviate the impact of aeration generated from the air diffuser on the hollow fiber membrane. For these reasons, there is a need for a hollow fiber membrane module with less adhesion and accumulation of suspended substances.

  The present invention for solving the above problems is a hollow fiber membrane element in which a plurality of hollow fiber membrane bundles are converged and fixed to a rectangular case with an adhesive in a state where at least one end of the hollow fiber membrane is open. The length d of the membrane bundle in the length direction of the case is 1 to 5 cm, and the relationship between the distance s between the hollow fiber membrane bundles in the length direction of the hollow fiber membrane bundle and the length d is 1/20 ≦ A hollow fiber membrane module comprising hollow fiber membrane elements, wherein s / d ≦ 1/1.

  The present invention has been made in order to solve the above-mentioned problems, effectively preventing the suspended matter from adhering to and accumulating on the hollow fiber membrane, and providing excellent air for cleaning the membrane surface with bubbles or the like. By improving the durability of the hollow fiber membrane module by obtaining a scrubbing effect and reducing the impact on the hollow fiber membrane, particularly in water treatment containing a high concentration of suspended solids, maintaining a high filtration flow rate, An object of the present invention is to provide a hollow fiber membrane module having stable filtration performance for a long period of time.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is an example of a front view of a hollow fiber membrane element of the present invention. The hollow fiber membrane element 1 of the present invention has a structure in which a bundle of hollow fiber membranes in which a large number of hollow fiber membranes are converged and fixed to a rectangular case 3 with an adhesive with one end of the hollow fiber membrane open. In the length direction of the case 3, individual membrane bundles are separated by an interval s. The interval s between the hollow fiber membrane bundles is sufficiently larger than the interval between the hollow fiber membranes in the hollow fiber membrane bundle. The hollow fiber membrane bundle A is arranged in at least 4 bundles in the length direction of the case 3 and 3 bundles or less in the width direction. Case 3 has a function of collecting filtered water and can be taken out of the system through piping. In the hollow fiber membrane element of the present invention, the number of membranes and the number of membrane bundles in the membrane bundle are not particularly limited, but the number of the hollow fiber membrane bundles is 100 or more, and the number of the hollow fiber membrane bundles is 20 or more. More preferably.

  FIG. 2 is an enlarged view of the hollow fiber membrane element of the present invention shown in FIG. In the embodiment of the hollow fiber membrane element of the present invention shown in FIG. 2, the length d of the hollow fiber membrane bundle with respect to the length direction of the case is 1 to 5 cm, and the interval s between the hollow fiber membrane bundles and the hollow fiber membrane The relationship with the length d of the bundle case in the length direction is 1/20 ≦ s / d ≦ 1/1. In a preferred embodiment, the relationship between the interval s between the hollow fiber membrane bundles and the length d of the hollow fiber membrane bundle in the length direction of the case is 1/15 ≦ s / d ≦ 1/2. The space | interval s between hollow fiber membrane bundles here is the distance between the hollow fiber membrane bundles in the focusing fixing | fixed part 2. As shown in FIG.

  FIG. 3 is an example of a view seen from the side of the hollow fiber membrane element of the present invention. In the hollow fiber membrane element 1 of the present invention, a plurality of hollow fiber membrane bundles A are bonded and fixed at the converging fixing portion 2 of the rectangular case 3 with an adhesive in a state where one end of the hollow fiber membrane is opened. In the embodiment of the hollow fiber membrane element of the present invention shown in FIG. 3, the hollow fiber membrane bundles A are separated by a distance t in the width direction of the case 3. The hollow fiber membrane bundle A is arranged in three or less bundles in the width direction of the case 3.

  FIG. 4 is an enlarged view of the hollow fiber membrane element of the present invention shown in FIG. In the embodiment of the hollow fiber membrane element of the present invention shown in FIG. 3, the relationship between the distance t between the hollow fiber membrane bundles and the length e of the hollow fiber membrane bundle in the width direction of the case is 1/20 ≦ t / e. <1/1. In a preferred embodiment, the relationship between the interval t between the hollow fiber membrane bundles and the length e of the hollow fiber membrane bundle in the width direction of the case is 1/15 ≦ t / e ≦ 1/2. The interval t between the hollow fiber membrane bundles here is the distance between the hollow fiber membrane bundles in the focusing and fixing portion 2.

  The filling rate of the hollow fiber membrane element used in the present invention is not particularly limited, but the filling rate of the element is preferably 5 to 70% from the viewpoint of production cost, and more preferably 15 to 50%. The filling rate referred to here is the ratio of the total cross-sectional area of the hollow fiber membrane to the cross-sectional area of the focusing and fixing portion.

As an example of a method for producing the hollow fiber membrane module used in the present invention, a known technique can be used.
For example, while traversing a hollow fiber around a frame-like skein frame body, it is wound in a loop shape, a number of hollow fiber membranes are arranged in one direction perpendicular to the length direction of the hollow fiber membrane, and the hollow fiber membranes are A hollow fiber membrane module of the present invention is manufactured by forming a laminated hollow fiber membrane bundle (see, for example, Patent Document 3), and concentrating and fixing the membrane bundle to a rectangular case with an interval defined by the present invention. be able to.

  As the hollow fiber membrane used in the present invention, various types can be used. For example, polyolefin, polysulfone, polyethersulfone, ethylene-vinyl alcohol copolymer, polyacrylonitrile, cellulose, polyvinylidene fluoride Conventionally known ones such as polyperfluoroethylene, polymethacrylic acid ester, polyester, and polyamide can be applied. Among them, polyvinylidene fluoride that is particularly excellent in chemical resistance and strength is preferred. . In addition, a copolymer of these resins or a part of which a substituent is introduced may be used, or a mixture of a plurality of types of resins may be used.

  When an organic polymer hollow fiber membrane is used, the method for producing the hollow fiber membrane is not particularly limited, and a method appropriately selected from known methods depending on the characteristics of the material and the desired hollow fiber membrane performance Can be adopted. Generally, a melt spinning method, a wet spinning method, a dry / wet spinning method, or the like is employed. From the viewpoint of water permeability, the hollow fiber membrane preferably has an asymmetric structure having a dense layer and a support layer. However, since a hollow fiber membrane generally produced by a melt spinning method has a symmetrical structure, wet spinning is preferable. It is preferable to produce by a phase change method such as a method or a dry-wet spinning method.

The pore diameter of the hollow fiber membrane used in the present invention is not particularly limited. However, the pore diameter within the range of UF membrane to MF membrane is 0.001 to 10 μm, which has high water permeability and lowers filtration efficiency. It is preferable because the fear is small. In particular, the effect of the present invention is more remarkable in a large pore diameter membrane or an ultrafiltration membrane having a fractional particle size of 1 to 10 μm and a pure water permeation rate of 30000 L / m ² / hr / 100 kPa or more.

  The length of the hollow fiber membrane used in the present invention is preferably in the range of 200 mm to 2000 mm from the viewpoint of handleability, and more preferably in the range of 300 mm to 1500 mm.

  As the case material of the hollow fiber membrane element used in the present invention, any material having mechanical strength and durability may be used. For example, polycarbonate, polysulfone, polyolefin, polyvinyl chloride, acrylic resin, ABS resin or the like is used. Can do.

  As an adhesive for the hollow fiber membrane element used in the present invention, an epoxy resin, an unsaturated polyester resin, a polyurethane resin, a silicone resin, various hot melt resins, and the like can be usually used. In addition, the viscosity of the adhesive before curing is not particularly limited, but since the adhesive is easily impregnated between a large number of hollow fiber membranes, it depends on the pore diameter of the hollow fiber membranes. In the UF and MF films, the viscosity of the adhesive before curing is preferably 500 to 3000 mPs.

The fractional particle size of the hollow fiber membrane used in the present invention refers to the particle size (S) of particles having a blocking rate of 90% by the hollow fiber membrane, and at least two types of particles having different particle sizes. In the following approximate expression (1), the value of S at which R is 90 is determined based on the measured value, and this is the fractional particle size.
R = 100 / (1−m × exp (−a × log (S))) (1)
In the above formula, a and m are constants determined by the hollow fiber membrane, and are calculated based on measured values of two or more types of rejection.

  Examples of the present invention will be described below, but the present invention is not limited thereby.

Polyvinylidene fluoride hollow fiber membranes are prepared in advance so as to form 20 hollow fiber membrane bundles from 4000 hollow fiber membranes, and have a water collecting function using a two-component curing type urethane resin. A plurality of hollow fiber membrane bundles were bonded and fixed to the case so as to arrange them, and a 10 m ² hollow fiber membrane element was produced. The hollow fiber membrane was an ultrafiltration membrane (UF membrane) having an inner diameter of 600 μm and an outer diameter of 1000 μm, a fractional particle diameter of the hollow fiber membrane of 0.04 μm, and the effective length of the membrane was 1000 mm. At this time, s / d, which is a ratio of the distance s between the hollow fiber membrane bundles to the length d of the hollow fiber membrane bundle in the length direction of the case, was 1/6.

The hollow fiber membrane module of the present invention is immersed in a 10 m ³ sludge tank having an air aeration diffuser tube at the bottom of the tank, and the hollow fiber membrane module having a membrane area of five hollow fiber membrane elements of the present invention having a membrane area of 50 m ² is dispersed. While aeration of 1 m ³ / hr of air in the standard state from the trachea, suction filtration was performed with a suction pump so that the membrane filtration flux was 0.5 m ³ / m ² (membrane area) / day. At this time, the differential pressure was 10 kPa, which was stable for one month, and adhesion of suspended solids was hardly observed.

  The MLSS concentration in the sludge tank during the evaluation period was 15000 mg / L on average, and the water temperature was 25 ° C.

Comparative Example 1
A single bundle of hollow fiber membrane elements comprising the same membrane material, module size, membrane area, and constituent members as in Example 1 was prepared. The s / d at this time was 0.

The hollow fiber membrane module of Comparative Example 1 is immersed in a 10 m ³ sludge tank having an air aeration diffuser at the bottom of the tank, and 1 m ³ / hr of air is aerated from the diffuser to the hollow fiber membrane module of the present invention in a standard state. However, suction filtration was performed with a suction pump so that the membrane filtration flux was 0.5 m ³ / m ² (membrane area) / day. The differential pressure at this time was 10 kPa and was stable for one month, but the suspended solids were remarkably adhered and deposited near the fixed part of the hollow fiber membrane and inside the membrane bundle.

  The MLSS concentration in the sludge tank during the evaluation period was 15000 mg / L on average, and the water temperature was 25 ° C.

A plurality of hollow fiber membrane bundles of polyvinylidene fluoride hollow fiber membranes are prepared in advance, and the plurality of hollow fiber membrane bundles are placed in a rectangular case made of PVC having a water collecting function using a two-component curing type urethane resin. Adhering and fixing so as to be arranged, a 1 m ² hollow fiber membrane element was produced. The hollow fiber membrane is a hollow fiber membrane having an inner diameter of 750 μm, an outer diameter of 1250 μm, a fractional particle diameter of 2.0 μm and a pure water permeation rate of 80000 L / m ² / hr / 100 k or more, and the effective length of the membrane is It was 500 mm. At this time, s / d was 1/4.

The hollow fiber membrane module of the present invention is immersed in a 500-liter sludge tank, and 0.1 m ³ / hr of air is aerated from an air diffuser installed inside the tank, and a membrane filtration flow rate is 0.8 m ³ / Suction filtration was performed so as to be m ² (membrane area) / day. At this time, the transmembrane pressure did not change for one week. Moreover, the sludge adhesion / deposition state at this time hardly accumulated in the hollow fiber membrane, and the sludge discharge was good. As the sludge treated water, pseudo sludge in which bentonite was dissolved in tap water was used. The MLSS concentration in the sludge tank during the evaluation period was 20000 mg / L on average, and the water temperature was 15 ° C.

Comparative Example 2
A single bundle of hollow fiber membrane elements comprising the same membrane material, module size, membrane area, and constituent members as in Example 2 was prepared.

The hollow fiber membrane module of Comparative Example 2 was immersed in a 500 L sludge tank, and 0.1 m ³ / hr of air was aerated from the air diffuser installed inside the tank, and the membrane filtration flow rate was 0.8 m with a suction pump. Suction filtration was performed so as to be ³ / m ² (membrane area) / day. At this time, the transmembrane pressure difference gradually increased in several hours and reached 60 kPa, and suction filtration could not be performed. Further, the sludge adhesion / deposition state at this time was often observed inside the hollow fiber membrane, and particularly, it was remarkably accumulated in the dense portion of the membrane near the fixing resin. As the sludge treated water, pseudo sludge in which bentonite was dissolved in tap water was used. The MLSS concentration in the sludge tank during the evaluation period was 20000 mg / L on average, and the water temperature was 15 ° C.

Reference Example 40 polysulfone hollow fiber membranes were bonded and fixed in a row using a two-component curing type urethane resin so as to provide a 1 mm gap between the hollow fiber membranes in a rectangular case having a water collecting function. The hollow fiber membrane was a hollow fiber membrane having an inner diameter of 750 μm, an outer diameter of 1250 μm, a fractional particle diameter of 2.0 μm, and an effective length of the membrane was 400 mm. The s / d at this time was 4/5.

The prototype element was immersed in a 100 L water tank, and 0.6 m ³ / hr of air was supplied from an air diffuser installed inside the tank, and an aeration durability test was performed. At this time, there was no film breakage for about 3 weeks.

It is a figure which shows an example seen from the front of the hollow fiber membrane module of this invention. It is an enlarged view of FIG. 1 of the hollow fiber membrane module of this invention. It is a figure which shows an example seen from the side of the hollow fiber membrane module of this invention. It is an enlarged view of FIG. 3 of the hollow fiber membrane module of this invention.

Explanation of symbols

A ... hollow fiber membrane bundle d ... length of hollow fiber membrane bundle in length direction of case e ... length of hollow fiber membrane bundle in length direction of case s ... between hollow fiber membrane bundles in length direction of rectangular case The gap t between the hollow fiber membrane bundles in the width direction of the rectangular case 1 The hollow fiber membrane element 2 The focusing fixing part 3 The case having a filtered water collecting function

Claims (5)

  A plurality of hollow fiber membrane bundles are hollow fiber membrane elements that are focused and fixed to a rectangular case with an adhesive in a state where at least one end of the hollow fiber membrane is open, and the length of the hollow fiber membrane bundle in the longitudinal direction of the case The length d is 1 to 5 cm, and the relationship between the distance s between the hollow fiber membrane bundles in the length direction of the hollow fiber membrane bundle case and the length d is 1/20 ≦ s / d ≦ 1/1. A hollow fiber membrane module comprising a hollow fiber membrane element.   The relationship between the length e of the hollow fiber membrane bundle in the width direction of the case and the interval t between the hollow fiber membrane bundles is 1/20 ≦ t / e ≦ 1/1. Hollow fiber membrane module. The hollow fiber membrane module according to claim 1 or 2, wherein the hollow fiber membrane has a fractional particle diameter of 1 to 10 µm and a pure water permeation rate of 30000 L / m ² / hr / 100 kPa or more.   The hollow fiber membrane module according to claim 1 or 2, wherein the hollow fiber membrane is an ultrafiltration membrane.   The hollow fiber membrane module according to any one of claims 1 to 4, wherein the hollow fiber membrane is made of a polyvinylidene fluoride resin.

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