JPH11319501A - Hollow fiber membrane module and use applications thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hollow fiber membrane module which can maintain the quality of permeated water at a high level even when the membranes are damaged by making the internal flow path cross section area of at least one part of hollow fiber membrane- fixed parts consisting of plural hollow fiber membranes with end parts fixed adhesively smaller than the internal flow path cross section area of the hollow fiber membranes in the non-adhesively fixed part. SOLUTION: In the hollow fiber membrane module comprising a plurality of hollow fiber membranes 1 with at least one of the end parts fixed adhesively while an open state is maintained by an adhesively fixed part 2. The part 8 is provided where the internal flow path cross section area of a hollow fiber membrane 2 of at least one part of hollow fiber membrane 1-adhesively fixed parts is substantially smaller than the internal flow path cross section area of the hollow fiber membrane 1 in the non- adhesively fixed part. Thus it is possible to inhibit the deterioration of the quality of permeated water, even when an untreated water flows into the interior of the hollow fiber membrane 1 due to damage inflicted to the membrane 1. Besides, even when a comparatively large amount of pollutant is contained in the untreated water, the pollutant is accumulated in the contracted dia. part 8 to generate a cake filtration state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow fiber membrane module and a method for using the same.
The present invention relates to an "external pressure" hollow fiber membrane module of a type in which treated raw water flows outside a hollow fiber membrane to obtain permeated water from the inside of the hollow fiber membrane, and a method of using the same.

[0002]

2. Description of the Related Art In recent years, separation operations using a polymer membrane have been actively performed. Above all, the development of water treatment is remarkable, and the technology of reverse osmosis method used for ultrapure water production, seawater, and irrigation desalination has many achievements and is expected to be developed in the future. Is done. Recently, the development of microfiltration and ultrafiltration methods for separation on the order of submicrons has been promoted. These include household water purifiers, domestic wastewater treatment, water purification,
It is being developed in a wide variety of fields, such as industrial water production and the food industry. In particular, Escherichia coli and the like can be completely prevented by using a separation membrane, and stable treated water quality can be maintained. Therefore, active development of drinking water production in water purification plants is being started.

[0003] Examples of the form of the separation membrane include a flat membrane laminated type, a spiral type, a tubular type, and a hollow fiber type. In particular, in the microfiltration method / ultrafiltration method in the production of drinking water, Due to the large amount of processing, a hollow fiber membrane that can provide a large effective membrane area per unit volume is generally used.

[0004]

Generally, in order to increase the processing efficiency, the separation membrane is made as thin as possible to reduce the transmission resistance. As a result, it has become possible to provide a very efficient and compact system as compared with the conventional methods such as the sand filtration method and the coagulation sedimentation method. However, when the membrane is damaged, the permeation resistance is low because of the small permeation resistance, and the leakage of treated raw water, which is difficult to occur in the conventional method, occurs through the damaged portion, and the permeated water quality is greatly reduced. In particular, in the production of drinking water, the above-mentioned Escherichia coli and the like are mixed in the permeated water, which has been a very serious problem.

The present invention has been made to solve the above-mentioned problems of the prior art, and provides a hollow fiber membrane module capable of maintaining high permeated water quality even when the hollow fiber membrane is damaged, and a method of using the same. The purpose is to do so.

[0006]

SUMMARY OF THE INVENTION The above objects of the present invention are as follows.
"In a hollow fiber membrane module in which a plurality of hollow fiber membranes are adhesively fixed while maintaining an open state by an adhesive fixing part at least at one end, the inside of the hollow fiber membrane in at least a part of the adhesive fixing part of the hollow fiber membrane The hollow fiber membrane module is characterized in that the cross-sectional area of the flow path is substantially smaller than the cross-sectional area of the flow path inside the hollow fiber membrane in the portion where the adhesive is not fixed. " Is done.

[0007]

FIG. 6 is a side sectional view showing an example of a normal hollow fiber membrane module, and FIG. 7 is an example of a hollow fiber membrane module when the hollow fiber membrane in FIG. 6 is damaged. It is a side sectional view.

As shown in FIG. 6, when this module is used in an “external pressure type” in which treated raw water flows from the treated raw water inlet 5 to the outside of the hollow fiber membrane 1 under normal conditions, dirt in the treated raw water is The water is blocked by the outer surface of the hollow fiber membrane, and the clean water that has permeated the membrane flows inside the hollow fiber membrane and is taken out from the permeated water outlet 4. Here, if the hollow fiber membrane is damaged, as shown in FIG. 7, the raw water to be treated flows from the damaged hollow fiber membrane 7, and the quality of the permeated water is reduced.

Here, as a result of diligent studies by the present inventors, first, damage to the hollow fiber membrane is caused by the interface between the portion 2 where the hollow fiber membrane is bonded and fixed and the portion where the hollow fiber membrane is not fixed, that is, the hollow fiber membrane. It has been found that the probability of occurrence at the base of is extremely high. Further, in this case, the flow resistance for the treated raw water to flow into the permeated water outlet 4 is only the length of the adhesive fixing portion 2 and is several to several tens times that of the undamaged hollow fiber membrane. It was found that leakage of the treated raw water occurred, and that if the hollow fiber membrane was damaged at the root, the permeation water quality was significantly reduced even if the number was small.

In view of the results, the present inventors have conducted repeated studies and found that as a method of increasing the quality of permeated water without reducing the amount of permeated water as much as possible, a hollow fiber in an adhesive fixing portion where the hollow fiber membrane is not likely to be damaged is used. The flow path of the fiber membrane is reduced to increase the flow resistance, and it is possible to minimize the leakage of raw water in the event that the hollow fiber membrane is damaged.

FIG. 1 is a side sectional view showing an example of the hollow fiber membrane module according to the present invention, and FIG. 2 is a side sectional view showing another example of the hollow fiber membrane module according to the present invention.

As shown in FIG. 1, a hollow fiber membrane module according to the present invention comprises a plurality of hollow fiber membranes 1 bonded and fixed while maintaining an open state by an adhesive fixing portion 2 at least at one end. In the module, the flow path cross-sectional area inside the hollow fiber membrane in at least a part of the adhesive fixing part of the hollow fiber membrane is substantially smaller than the flow path cross-sectional area inside the hollow fiber membrane in the part not bonded and fixed. It has a portion 8 which is gradually reduced.

Accordingly, even if the hollow fiber membrane is damaged and the raw water for treatment flows into the hollow fiber membrane, it is possible to suppress a decrease in the quality of the permeated water. Furthermore, if the treated raw water contains relatively large dirt, the dirt accumulates in the hollow fiber membrane where the cross-sectional area of the flow channel is reduced, so that it takes some time after the damage to the hollow fiber membrane. When the time elapses, even in the portion where the dirt is accumulated, the cake is filtered by the accumulation, so that the dirt in the raw water does not leak into the permeated water.

The effect of reducing the cross-sectional area of the flow path is not limited, and the effect is manifested regardless of the degree. Become. In this regard, the cross-sectional area of the part where the flow path cross-sectional area inside the hollow fiber membrane is small in at least a part of the adhesively fixed part of the hollow fiber membrane is A, and the hollow fiber membrane in the part where the adhesive fiber is not fixed. Is defined as B, the sectional area of the flow path inside is 0.5 ≦ A / B ≦ 0.
By setting it to 8, it is preferable in that the quality of permeated water can be improved while suppressing a decrease in the amount of permeated water.

Here, the length of the portion of the adhesive fixing portion where the flow path cross-sectional area inside the hollow fiber membrane is small is basically not limited. However, as described above, from the viewpoint of increasing the flow resistance inside the hollow fiber membrane, which is the first effect of the two effects according to the present invention, the length of the portion where the cross-sectional area of the flow channel is small is small. If the length is short, the effect of the flow resistance is reduced, and therefore, the length of the hollow fiber membrane portion having a smaller flow path cross-sectional area is preferably equal to or more than half of the length of the fixed portion. . However, as described above, if the portion with a small cross-sectional area of the flow path is long, the flow resistance of clean permeated water will also be to some extent, so it is important to optimize it together with the inner diameter of the hollow fiber membrane. is there.

In order to accumulate dirt, which is the second effect, it is sufficient that there is a portion where the flow path cross-sectional area is small, and the length is not particularly limited. Therefore, considering only the purpose of exhibiting this effect alone, it is substantially preferable that the length of the hollow fiber membrane portion having a reduced channel cross-sectional area is 1 mm or more and 10 mm or less. However, in this range, the first effect is small, so that the quality of the permeated water decreases until the second effect is exhibited, that is, until cake filtration due to accumulation of dirt is performed. Further, in order to exhibit the second effect, it is preferable that cake is easily generated due to accumulation of dirt. In this regard, as shown in FIG. It is preferable that the length d from the non-opening side of the part where the area is substantially the same as the cross-sectional area of the flow path of the part not bonded and fixed is at least 5 mm or more. By taking such a shape, it is easy to hold the cake layer that has accumulated.

The hollow fiber membrane module to which the present invention is applied is generally airtightly sealed (potted) between the hollow fiber membrane and the hollow fiber membrane and between the hollow fiber membrane and the module container. Take the shape that was made. by this,
The outside and inside of the hollow fiber membrane are isolated by the hollow fiber membrane itself,
Separation treatment can be performed through the membrane. The structure of the hollow fiber membrane module is such that, after potting both ends of a hollow fiber membrane, the hollow fiber membrane is opened from both ends.
No. 027, Japanese Utility Model Application Laid-Open No. 2-100636, Japanese Utility Model Application Laid-Open No. 3-15628, Japanese Utility Model Application Laid-Open No. 3-59028, etc.
No. 29, etc., a "single-end open type" in which only one end is opened after potting both ends,
The hollow fiber membrane as shown in US Pat.
A "U-shape" in which the hollow fiber membrane is opened with only one end of the hollow fiber membrane open, and as shown in JP-A-3-12288, the U-shape section is cut, and the hollow fiber membranes are cut one by one. There is a “comb-type” module that is sealed alone, and the filtration direction includes the case where treated raw water flows inside the hollow fiber membrane (internal pressure type) and the case where it flows outside (external pressure type).

The "single-end open type", "U-shaped" and "comb type" have only an outlet inside the hollow fiber, and these generally supply water to be treated outside the hollow fiber membrane. Then, it is used in a method of obtaining permeated water from the inside of the hollow fiber membrane (external pressure type). The external pressure method is a method that can be applied even if the water to be treated is dirty, so that it is very expected to be developed in the future. When these modules are applied to the present invention, in particular, in the case of the "external pressure type", the above two effects can be exhibited, which is very effective. In the case of "internal pressure type", the inner diameter of the hollow fiber membrane is relatively large because the raw water is allowed to flow inside the hollow fiber membrane,
It is necessary to prevent cake accumulation, which is the second effect described above. Therefore, the first effect can be exhibited by reducing the cross-sectional area of the flow path in the hollow fiber within a range in which cake does not accumulate.

The hollow fiber membrane to be used in the present invention is not particularly limited. However, the problem of permeated water quality deterioration due to leakage of raw water according to the present invention is that it is difficult to provide sufficient strength. Since the material is liable to be damaged by the fatigue due to the rocking, application to a hollow fiber membrane using a polymer membrane is effective. Examples of the polymer membrane include a homogeneous hollow fiber membrane, a porous hollow fiber membrane, and a composite hollow fiber membrane, but are not particularly limited. Specific examples of these hollow fiber membranes include a polyacrylonitrile porous hollow fiber membrane, a polyimide porous hollow fiber membrane, a polyethersulfone porous hollow fiber membrane, a polyphenylene sulfide sulfone porous hollow fiber membrane, and a polytetrafluoroethylene porous hollow fiber membrane. Fiber hollow membranes such as fiber membranes, polypropylene porous hollow fiber membranes, polyethylene porous hollow fiber membranes, and the like, and crosslinked silicone, polybutadiene, polyacrylonitrile butadiene, ethylene propylene rubber, Examples thereof include a composite hollow fiber membrane obtained by compounding a rubber-like polymer such as neoprene rubber and a homogeneous hollow fiber membrane such as a crosslinked silicone tube. The inner and outer diameters of the hollow fiber membrane are not particularly limited, and those having an inner diameter of 1 mm or less to those having several mm or more can be applied.

Further, in order to carry out the present invention, as a method of reducing the internal flow passage cross-sectional area of a part of these hollow fiber membranes, there are a method of changing the film forming conditions of the hollow fiber membrane with time, A method of performing treatment after film formation can be given. Regarding the film forming conditions, hollow fiber membranes having different diameters can be obtained by temporarily changing the film forming speed, the film forming temperature, and the like. On the other hand, as a method of performing a treatment after film formation, a method of shrinking the hollow fiber membrane by heat or a solvent or deforming the hollow fiber membrane by pressure can be mentioned. When shrinking by heat, methods such as raising the ambient temperature or bringing a high-temperature gas or liquid into contact with the sealing part can be cited.However, since the temperature is easy to control, the gas or liquid controlled at a certain temperature is used. The method of making contact with the sealing portion is most suitable. However, care must be taken because the shrinkage ratio changes depending on the temperature, and if the temperature is too high, the film is denatured.

When a solvent is used, the object can be achieved by using a solvent to which a component that dissolves or swells the hollow fiber membrane is added. However, when a component that dissolves the hollow fiber membrane is used, the concentration is too high. Since the film completely dissolves, it is important to optimize the concentration so as not to dissolve. The solvent for dissolving or swelling the hollow fiber membrane is not particularly limited, but includes N-methyl-2-pyrrolidone, dimethylsulfoxide, tetrahydrofuran, hexane and the like.
Also, when a solvent having a high permeability or a low viscosity is used for the hollow fiber membrane, the solvent may enter into the unsealed portion of the hollow fiber membrane, and there is a risk of impairing the membrane performance. In such a case, it is preferable to add an appropriate amount of a thickener to the solvent.

Specific methods for applying pressure include, for example, flattening using a roll press machine and crushing with a hammer, but the method is not particularly limited. In order to easily deform the hollow fiber membrane, it is effective to use a method in which the hollow fiber membrane is heated or impregnated with a solvent in advance.

Incidentally, the method of bonding and fixing the hollow fiber membrane is generally performed by a method called potting. Potting includes a method in which the adhesive is allowed to permeate into and between the hollow fiber membranes in a stationary state, a "stationary method", and a method in which the adhesive is permeated using centrifugal force, "centrifugal method", but is particularly limited. is not. The adhesive used for potting is not particularly limited, but a urethane-based adhesive or an epoxy-based adhesive is generally used. Furthermore, it is also possible to adopt a method of fusing hollow fiber membranes to each other. In addition, the temperature control at the time of potting,
Since it affects the curing of the adhesive, it is necessary to consider it. However, it is also possible to adopt a method of causing the hollow fiber membrane to contract simultaneously with the potting in consideration of the heat generation of the adhesive.

[0024]

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited by this.

Example 1 An average pore diameter of 0.01 made of polyacrylonitrile
μm, outer diameter 680 μm, inner diameter 400 μm, length 800 m
A 200-m porous hollow fiber membrane having a U-shape was immersed in boiling water for about 40 mm over the open end of the hollow fiber membrane for about 40 mm. This hollow fiber membrane bundle has an inner diameter of 40 mm and a thickness of 4 m.
m, and was plugged with a urethane adhesive (manufactured by Nippon Polyurethane Co., Ltd.) to prevent the potting material from entering the potting portion at the end of the hollow fiber and causing clogging. Next, after potting was performed using the same adhesive, the potting fixing portion was cut, and the inside of the hollow fiber membrane was opened. Further, a water collecting device is attached to the opened potting portion, and the effective length of the hollow fiber membrane is 350 m.
m modules were produced. The appearance is shown in FIG.

This module has a potting thickness of 25
mm, d = 10 mm at the potting portion. In addition, the value of the ratio (A /
B) averaged 0.58.

The module thus obtained was subjected to a filtration test by external pressure type total filtration using raw water having a turbidity of about 20 ppm. At this time, the pressure difference between the raw water side and the permeation side is 0.
The water temperature was 20 ° C. at 5 kgf / cm ² . As a result, the amount of permeated water was 60 l / h, and the turbidity of permeated water was 0.07 p.
pm. Further, five hollow fibers of the same module were cut at the root of the hollow fiber membrane, and a similar filtration test was performed. At the start of filtration, the permeated water amount was 67 L / h, and the permeated water turbidity was 3. The amount of permeated water 60 minutes after the start of filtration was 60 l / h, and the turbidity of permeated water was 0.8 ppm.
It was 5 ppm.

Example 2 100 hollow fiber membranes having the same specifications and the same length as in Example 1 were arranged in a line, and a position approximately 40 mm from both ends was pressurized and flattened. The two hollow fiber membrane bundles were formed in a U-shape, and a hollow fiber membrane module as shown in FIG. This module has a potting thickness of 25m
m, d = 10 mm in the potting area. In addition, the value of the ratio (A /
B) averaged 0.58.

The module thus obtained was subjected to a filtration test in the same manner as in Example 1. As a result, the amount of permeated water was 64 l / h, and the turbidity of permeated water was 0.07 ppm. Further, five hollow fibers of the same module were cut at the root of the hollow fiber membrane, and a similar filtration test was performed. At the start of filtration, the permeated water volume was 82 l / h, and the permeated water turbidity was 5 .14 ppm, the amount of permeated water 60 minutes after the start of filtration was 74 l / h, and the permeated water turbidity was 0.98.
ppm.

Comparative Example 1 A hollow fiber membrane module as shown in FIG. 5 was produced in the same manner as in Example 1 except that the end of the hollow fiber membrane was not immersed in boiling water.

The module thus obtained was subjected to a filtration test in the same manner as in Example 1. As a result, the amount of permeated water was 64 l / h, and the turbidity of permeated water was 0.07 ppm. Further, five hollow fibers of the same module were cut at the root of the hollow fiber membrane, and a similar filtration test was performed. At the start of filtration, the permeated water amount was 86 L / h and the permeated water turbidity was 5 .38 ppm, the amount of permeated water 60 minutes after the start of filtration was 78 l / h, and the permeated water turbidity was 5.10 p.
pm.

[0032]

According to the present invention, in a hollow fiber membrane module in which a plurality of hollow fiber membranes are bonded and fixed at at least one end and then opened, the hollow fibers in at least a part of the bonded and fixed portions of the hollow fiber membranes are provided. The hollow fiber membrane module according to claim 1, wherein a cross-sectional area of the flow path inside the membrane is substantially smaller than a cross-sectional area of the flow path inside the hollow fiber membrane in a portion where the adhesive is not fixed. Even if the membrane is damaged, it is possible to suppress the leakage of the treated raw water and maintain a high water quality.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an example of a hollow fiber membrane module according to the present invention.

FIG. 2 is a side sectional view showing another example of the hollow fiber membrane module according to the present invention.

FIG. 3 is a side sectional view showing an example of the hollow fiber membrane module according to the present invention in Example 1.

FIG. 4 is a side sectional view showing an example of a hollow fiber membrane module according to the present invention in Example 2.

FIG. 5 is a side sectional view showing an example of a hollow fiber membrane module in Comparative Example 1.

FIG. 6 is a side sectional view showing an example of a normal hollow fiber membrane module.

FIG. 7 is a side sectional view showing an example of a hollow fiber membrane module when the hollow fiber membrane in FIG. 6 is damaged.

[Explanation of symbols]

 1: hollow fiber membrane 2: potting part 3: sealing material 4: permeated water outlet 5: treated raw water inlet 6: treated drainage outlet 7: damaged hollow fiber membrane 8: hollow fiber membrane part with reduced flow channel cross-sectional area

Claims (6)

[Claims] 1. A hollow fiber membrane module in which a plurality of hollow fiber membranes are adhesively fixed at least at one end while maintaining an open state by an adhesive fixing part, wherein at least a part of the adhesive fixing part of the hollow fiber membrane is hollow. A hollow fiber membrane module, wherein the cross-sectional area of the flow path inside the fiber membrane is substantially smaller than the cross-sectional area of the flow path inside the hollow fiber membrane at a portion where the adhesive is not fixed. 2. The cross-sectional area of a portion of the hollow fiber membrane where the flow channel cross-sectional area is small in at least a part of the adhesively fixed portion of the hollow fiber membrane is denoted by A, and the hollow portion in the portion where the adhesive is not fixedly fixed. 2. The hollow fiber membrane module according to claim 1, wherein, when the cross-sectional area of the flow channel inside the fiber membrane is B, the relationship of 0.5 ≦ A / B ≦ 0.8 is satisfied. 3. The method according to claim 1, wherein the length of the hollow fiber membrane portion whose flow path cross-sectional area is smaller than the length of the adhesively fixed portion of the hollow fiber membrane is half or more. The hollow fiber membrane module according to claim 1. 4. The hollow fiber membrane module according to claim 1, wherein the length of the hollow fiber membrane portion in which the cross-sectional area of the flow passage is small is 1 mm or more and 10 mm or less. . 5. The cross-sectional area of the hollow fiber membrane at the adhesive fixing portion of the hollow fiber membrane is at least 5 mm from the side where no opening is provided.
The hollow fiber membrane module according to any one of claims 1 to 4, wherein the flow path cross-sectional area of the portion not adhered and fixed over the above is substantially the same. 6. Using the hollow fiber membrane module according to any one of claims 1 to 5, flowing treated raw water outside the hollow fiber membrane, and obtaining permeated water from inside the hollow fiber membrane. To use hollow fiber membrane module.