JP2000070682A - Hollow fiber membrane module and its use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hollow fiber membrane module capable of stably obtaining high transmitted water quantity and high water quality. SOLUTION: In a hollow fiber membrane module wherein hollow fiber membrane bundles obtained by forming a large number of hollow fiber membranes 1 into a U-shape are housed in a container 6 and bonded and fixed at the end parts thereof to be opened, the cross-sectional area S of the inside part of the container 6 at the parts of non-bonded and unfixed hollow fiber membranes is set so that a part of an area S1 substantially smaller than the cross-sectional area S2 of the inside part of the container 6 in the vicinity of the bonded and fixed part is present.

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, a method for using the same, and a method for treating water. More specifically, the present invention relates to a method for treating raw water flowing outside a hollow fiber membrane and permeating from inside the hollow fiber membrane. The present invention relates to a hollow fiber membrane module suitable for an “external pressure type” of obtaining water 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 reverse osmosis technology used for ultrapure water production, seawater, and irrigation water 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 advanced, and these include household water purifiers, domestic wastewater treatment, water purification,
It is being developed in various 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. In addition, as a form of the separation membrane, a flat membrane laminated type, a spiral type, a tubular type,
A hollow fiber membrane type can be mentioned, but in particular, in the microfiltration method / ultrafiltration method in the production of drinking water, a hollow fiber membrane capable of obtaining a large effective membrane area per unit volume is used because of a large amount of treatment. Is becoming more common.

[0003]

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. Under such circumstances, it is an object of the present invention to provide a hollow fiber membrane module that has a small pressure rise during use and has little damage.

[0004]

The present invention has the following arrangement. 1. "A hollow fiber membrane module in which a plurality of hollow fiber membranes are formed in a U-shape and fixed with an adhesive fixing part with the ends opened, and the hollow fiber membrane bundle and the adhesive fixing part are in a container. Then, when the inside of the container is separated from the adhesive fixing portion, the cross-sectional area (S
2) A hollow fiber membrane module having at least a portion having a cross-sectional area (S1) smaller than that of (2). 2. "When the total cross-sectional area of the hollow fiber membrane bundle in the container is S3, the hollow fiber membrane module is characterized by satisfying 1.2 ≦ (S2-S3) / (S1-S3) ≦ 10”. 3. 3. Any one of the above-mentioned hollow fiber membrane modules, wherein 0.4 ≦ S3 / S1 ≦ 0.6. 4. The hollow fiber membrane module according to any one of the above, wherein 0.2 ≦ S3 / S2 ≦ 0.4. "The length L2 of the portion having a cross-sectional area of S2 from the adhesive fixing portion is 0.1% of the effective length L of the hollow fiber membrane.
≦ L2 / L ≦ 0.3, wherein
The hollow fiber membrane module according to any one of the above. 6. 6. The hollow fiber membrane module according to any one of the above, wherein a cross-sectional area of an inner portion of the container surrounding a curved portion of the U-shaped hollow fiber membrane is larger than S1. "A hollow fiber membrane module according to any one of the preceding claims, characterized in that at least one pipe is provided outside the container having a cross-sectional area of S2 in a form for communicating with the outside of the hollow fiber membrane. 8. 8. The hollow fiber membrane module according to any one of the above, wherein the effective length per one hollow fiber membrane is 500 mm or more. "Any of the hollow fiber membrane modules described above are of an external pressure type.""A method for treating water, comprising using any of the above modules to supply treated water to the outside of the hollow fiber membrane and extracting permeated water from the inside of the hollow fiber membrane."

[0005]

FIG. 1 shows an example of a hollow fiber membrane module according to the present invention. 2 and 3 show an example of a conventional hollow fiber membrane module. This module shape is used in a system in which treated raw water flows outside the hollow fiber membrane and permeated water is obtained from the inside of the hollow fiber membrane, that is, an “external pressure type” in which the outside has a higher internal pressure. In this module, raw water is supplied from pipe 5 or pipe 7,
In a normal state, dirt in the treated raw water is blocked on the outer surface of the hollow fiber membrane, and permeated water (clean water) permeating the membrane flows inside the hollow fiber membrane, and is taken out from the permeated water outlet 4. Will be. Here, if the hollow fiber membrane is damaged,
As illustrated in FIG. 2, the treated raw water flows from the damaged hollow fiber membrane, and the quality of the permeated water is reduced.

The present inventors have conducted intensive studies on this point and obtained the following results. Since the external pressure type hollow fiber membrane module obtains clean permeated water from the inside of the hollow fiber membrane while accumulating dirt on the outer surface of the hollow fiber membrane, regular or regular cleaning of the outer surface of the hollow fiber membrane is required. It is said. As a general method for cleaning the outer surface of the hollow fiber membrane, there are a raw water cleaning method using a raw water flow and an air scrubbing cleaning method in which air is blown into the raw water and the flow or the hollow fiber membrane oscillates. Both of these methods remove and remove dirt accumulated on the outer surface of the hollow fiber by a shear force generated by the flow of raw water or air. However, the shear force may damage the hollow fiber membrane. further,
It was found that the probability of this damage to the hollow fiber membrane was extremely high at the interface between the part where the hollow fiber membrane was bonded and fixed and the part where the hollow fiber membrane was not fixed, that is, at the root of the hollow fiber membrane. In this case, the flow resistance for the treated raw water to flow into the permeated water outlet is only the length of the adhesive fixing portion, and leakage of the treated raw water is several to several tens times that of the undamaged hollow fiber membrane. When the hollow fiber membranes were damaged at the root, it was found that the permeation water quality was significantly reduced even if the number was small. On the other hand, in order to remove dirt accumulated on the surface of the hollow fiber membrane, raw water or air is caused to flow on the membrane surface, and a shear force due to the flow is required. Here, since the shear force on the hollow fiber membrane surface is proportional to the hollow fiber membrane surface flow velocity, it is better to increase the membrane surface flow velocity as much as possible except for the vicinity of the adhesive fixing portion where the hollow fiber membrane is easily damaged. In the case of the conventional hollow fiber membrane module illustrated in FIGS. 2 and 3, the hollow fiber membrane surface is excellent in cleaning property in FIG. The fiber membrane is easily damaged. Conversely, in FIG. 3, although the hollow fiber membrane can be prevented from being damaged, the flow of raw water or air during washing short-passes the wide space between the hollow fiber membrane bundle and the container, so that the cleaning property is improved. And had a problem in the recovery from washing in the case of long-term operation.
Thus, the conflicting demands that the hollow fiber membrane has a high cleaning recovery property and is not damaged (in other words, a large shear force is applied to the hollow fiber membrane while applying as little force as possible to the root of the hollow fiber membrane). The inventors have devised the present invention to satisfy them.

That is, the cross-sectional area S of the inner portion of the container at the portion where the hollow fiber membrane is not bonded is smaller than the cross-sectional area S2 of the inner portion of the container near the root (adhesion fixing portion) of the hollow fiber membrane. Is provided at a position distant from the adhesive fixing portion so as to surround the hollow fiber membrane, the membrane surface flow rate of the non-adhesive portion of the hollow fiber membrane during washing can be kept high, and high washing power can be maintained. In addition, it is possible to suppress the flow rate of the membrane surface at the root of the hollow fiber membrane and prevent the membrane from being damaged.

In general, a pipe for raw water supply / drainage, and a pipe 5 for exhaust / intake of air inside the module due to supply / drainage and overflow of raw water in the module are provided near the end of the hollow fiber membrane of the module. By applying the present invention, it is possible to remarkably improve the damage of the hollow fiber membrane particularly near the pipe.

Here, with respect to S1 and S2, it is necessary to control the flow velocity of the membrane surface at each position. For this reason, the present inventors have studied and found that the total diameter based on the outer diameter of the hollow fiber membrane is determined. When the cross-sectional area is S3, 1.2 ≦ (S2-S
3) It has been found that the object of the present invention can be more effectively achieved by setting the ratio to (S1−S3) ≦ 10. That is, (S2-S3) / (S1-S3)
Is small, the effect of the present invention cannot be sufficiently exhibited. On the other hand, if it is larger than 10, the raw water flow path becomes too small in the portion of S1, and the flow path tends to be easily blocked by dust contained in the raw water. As a result of further study on this range, as a more desirable range, 1.5 ≦ (S2-S3) / (S1-
By setting S3) ≦ 5.0, the effects of the present invention can be exhibited highly.

Further, when attention is paid to the cleaning property of the dirt accumulated on the film surface, it is necessary to use S3 / S1 to obtain sufficient cleaning power.
It is desirable that ≧ 0.4, but if S3 is too small relative to S1, the flow rate of raw water on the membrane surface becomes too high, and the membrane surface is damaged by some of the contaminants in the raw water. Therefore, considering these, 0.4 ≦ S3
By setting /S1≦0.6, a hollow fiber membrane module more suitable for the present invention can be obtained. On the other hand, when attention is paid to the damage of the adhesive fixing portion of the hollow fiber membrane, it is preferable that S3 / S2 ≦ 0.4 in order to prevent the damage,
If the number of hollow fiber membranes to be filled in the module is too small, the volume efficiency is reduced.
≦ S3 / S2 ≦ 0.4 is desirable.

The portion having the cross-sectional area S2 is
It is in the vicinity of the adhesive fixing portion of the hollow fiber membrane, but is not particularly limited as long as the length L2 from the adhesive fixing portion is a certain value. In addition to the example shown in FIG. 1 and the S1 portion as shown in FIG. 5 and the boundary between S2 portion is tapered,
Even if the S1 part is divided into a plurality as shown in FIG. However, in the portion where the cross-sectional area is S2, it is not advisable to make the length too long because the flow rate of the film surface at the time of cleaning is likely to decrease and the cleaning property cannot be maintained. Therefore, in this regard, as shown in FIG. 6, it is desirable that the effective length L of the hollow fiber membrane be 0.1 ≦ L2 / L ≦ 0.3. The length of each of L2 and L is not particularly limited, but if L2 is long, the cleaning effect cannot be sufficiently exhibited. Therefore, in order to sufficiently exhibit the effects of the present invention, L2 is defined as L2. , 200 mm or less, and L is desirably 500 mm or more.

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. In addition, as described above, the effect of the present invention is exhibited by using an “external pressure type” in which raw water is flown outside the hollow fiber membrane and permeated water is obtained from the inside as described above. Can be done. In this case, it is necessary to connect at least one pipe for introducing or discharging raw water or air flowing outside the hollow fiber membrane. Here, for example, as illustrated in FIG. 7, when the pipe 5 is connected to a portion having a cross-sectional area of S1, the hollow fiber membrane is hollow due to the influence of the flow of raw water or air because the cross-sectional area of the flow channel is small. There is a risk of breaking the thread membrane. Therefore, in order to reduce the influence of the flow caused by the pipe by connecting the pipe to a portion having a cross-sectional area of S2 as illustrated in FIGS. It can be difficult. Further, as shown in FIG. 8, for example, it is possible to further prevent the hollow fiber membrane from being damaged by providing a baffle plate 9 at the pipe opening. Further, the pipe 7 provided at the lower part of the module can be used as a pipe for water supply / drainage or air supply. On the other hand, the pipe 5 provided on the upper part of the module can be used as a pipe for water supply / drainage or air discharge. In this case, as shown in FIG. 9, not only the adhesive fixing portion of the hollow fiber membrane, but also the cross-sectional area of the hollow fiber membrane in the U-shape is made larger than S1 so that the hollow fiber membrane in the vicinity of the pipe can be formed. Damage can be prevented. Also,
As a result, the free space of the U-shaped portion of the hollow fiber membrane becomes easy to spread, so that it is possible to obtain an effect that it is easy to discharge dirt easily accumulating in the vicinity of the U-shaped portion and to easily disperse the air supplied from the lower portion. . From this point, it is possible to obtain a greater effect by inclining the container bottom as shown in FIG. Of course, even when the pipe is at the center of the module, the cross-sectional area near the pipe is made larger than S1 in the same manner, so that the damage to the hollow fiber membrane can be prevented.

[0013] The hollow fiber membrane to be used in the present invention is not particularly limited, but 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.

There is no particular limitation on the inner diameter of the hollow fiber membrane applied to the present invention. A hollow fiber membrane having a larger inner diameter is generally less likely to be damaged, and a membrane having a smaller inner diameter is more likely to be damaged at the time of damage. Considering that the degree of leakage of raw water is relatively small. The inner diameter of the hollow fiber membrane is 3
It is preferable that the thickness be 50 μm or more and 1000 μm or less,
When the thickness is 50 μm or less, the effects of the present invention are easily exhibited and are very suitable.

By the way, 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 penetrated by using a centrifugal force, "centrifugal method". 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.

Such a hollow fiber membrane module has a low probability of breakage and can be suitably used for separating water or gas.

[0017]

The present invention will be described more specifically with reference to the following examples.

EXAMPLES AND COMPARATIVE EXAMPLES Average pore diameter of 0.01 made of polyacrylonitrile
μm, outer diameter 680 μm, inner diameter 400 μm, length 1600
A 3700 mm porous hollow fiber membrane formed into a U-shaped hollow fiber membrane bundle is inserted into a 7 mm thick acrylic container, and the potting material does not enter the potting portion at the end of the hollow fiber to cause clogging. As described above, the sealing was performed with a urethane adhesive (manufactured by Nippon Polyurethane). Next, after potting was performed using the same adhesive, the hollow fiber membrane was cut so that the length of the adhesive fixing portion of the hollow fiber membrane by potting was 60 mm, and the inside of the hollow fiber membrane was opened. Further, a water collecting device was attached to the opened potting portion, and the effective length of the hollow fiber membrane was 800 mm and the total length of the hollow fiber membrane was 860 m as shown in FIG.
A U-shaped hollow fiber membrane module of m was produced. Here, the modules A to E shown in FIG. 11 in which the diameter D1 of the portion having the cross-sectional area S1 is changed and the modules S1 shown in FIGS.
= Modules F and G satisfying S2 were produced.

The module thus obtained was subjected to a quantitative filtration operation test by an external pressure type total filtration method using raw water having a turbidity of about 20 ppm and a water temperature of about 25 ° C. at a filtration flow rate of 1.0 m / day. . At this time, the raw water is supplied from the pipe 5,
The pipe 7 was closed. After performing the filtration operation for 1 hour, the filtration operation is interrupted, the pipe 7 is opened, air is supplied from the pipe 5, air scrubbing is performed at a flow rate of 40 liter / min for 1 minute, and then the pipe 7 is opened. After the raw water was discharged through the pipe 5, the raw water was supplied to the module container, and the filtration operation was performed again to perform a repetitive filtration operation test.

Table 1 shows the results of the operation.

[0021]

[Table 1]

After 1000 hours of operation, the increase in the filtration pressure difference (pressure on the raw water side-pressure on the permeation side) was minimized at C. G also showed a relatively small increase in differential pressure, but found a problematic damage to the cutting of the hollow fiber membrane.

[0023]

According to the hollow fiber membrane module of the present invention, a high-performance hollow fiber membrane module is provided, in which the pressure rise during use is small, the hollow fiber membrane is hardly damaged, and the membrane has a high recoverability in washing. .

[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 an example of a conventional hollow fiber membrane module.

FIG. 3 is a side sectional view of an example of a conventional hollow fiber membrane module.

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

FIG. 5 is a side sectional view showing another example of the hollow fiber membrane module according to the present invention.

FIG. 6 is a side sectional view showing the length of the hollow fiber membrane module according to the present invention.

FIG. 7 is a side sectional view showing an example of a hollow fiber membrane module according to the present invention in which the positions of the pipes are different.

FIG. 8 is a side sectional view showing an example of a hollow fiber membrane module having a baffle plate in a pipe according to the present invention.

FIG. 9 is a side sectional view showing an example of a hollow fiber membrane module according to the present invention, in which the cross-sectional area of the container at the U-shaped portion of the hollow fiber membrane is large.

FIG. 10 is a side sectional view showing another example of the hollow fiber membrane module according to the present invention, in which the cross-sectional area of the container at the U-shaped portion of the hollow fiber membrane is large.

FIG. 11 is a side cross-sectional view of the container of the hollow fiber membrane module used in the example according to the present invention.

FIG. 12 is a side sectional dimensional view of a container of the hollow fiber membrane module used in Comparative Example 1.

FIG. 13 is a side sectional dimensional view of a container of the hollow fiber membrane module used in Comparative Example 2.

[Explanation of symbols]

 1: hollow fiber membrane 2: adhesive fixing part 3: sealing material 4: permeated water outlet 5: piping 6: container 7: piping 8: raw water flow 9: baffle plate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D006 GA02 HA03 HA06 HA19 JA15A JA15Z JA25A JA25B JA25C JA29A JB04 JB05 JB07 JB08 KC02 KC14 MA01 MA06 MA22 MA33 MC22 MC23 MC26 MC30 MC39 MC58 MC61 MC62 MC65 NA41 PA01 PB02 PB15

Claims (10)

[Claims] 1. A hollow fiber membrane bundle in which a plurality of hollow fiber membranes are formed in a U-shape and fixed with an adhesive fixing portion in a state where the ends are open, and the hollow fiber membrane bundle and the adhesive fixing portion are hollow inside a container. A thread membrane module, wherein the container has at least a portion having a cross-sectional area (S1) smaller than a cross-sectional area (S2) in the vicinity of the adhesive fixing portion when the inside of the container is away from the adhesive fixing portion. And a hollow fiber membrane module. 2. The method according to claim 1, wherein when the total sectional area of the hollow fiber membrane bundle in the container is S3, 1.2 ≦ (S2−S3) / (S1−S3) ≦ 10. Hollow fiber membrane module. 3. The hollow fiber membrane according to claim 1, wherein when the total cross-sectional area of the hollow fiber membrane bundle in the container is S3, 0.4 ≦ S3 / S1 ≦ 0.6. module. 4. The method according to claim 1, wherein when the total cross-sectional area of the hollow fiber membrane bundle in the container is S3, 0.2 ≦ S3 / S2 ≦ 0.4. Hollow fiber membrane module. 5. The length L2 of the portion having a cross-sectional area of S2 from the adhesive fixing portion is larger than the effective length L of the hollow fiber membrane.
The hollow fiber membrane module according to claim 1, wherein 0.1 ≦ L2 / L ≦ 0.3. 6. The cross-sectional area of an inner portion of a container surrounding a curved portion of a U-shaped hollow fiber membrane is larger than S1. Hollow fiber membrane module. 7. The container according to claim 1, wherein at least one pipe is provided outside the container having a cross-sectional area of S2 so as to communicate with the outside of the hollow fiber membrane.
6. The hollow fiber membrane module according to any one of 6. 8. An effective length of one of said hollow fiber membranes is 500.
The hollow fiber membrane module according to any one of claims 1 to 7, wherein the length is not less than mm. 9. The hollow fiber membrane module according to claim 1, which is of an external pressure type. 10. A method for treating water, comprising using the module according to any one of claims 1 to 9, supplying raw water to the outside of the hollow fiber membrane, and extracting permeated water from the inside of the hollow fiber membrane.