JP2000300971A - Foam detecting method for interior of hollow fiber membrane module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make surely detectable the generation of foams in a hollow s fiber membrane module regardless of the kind of the material of hollow fiber membrane by transmitting ultrasonic wave from the outside of the module and detecting its reflection echoes in the state of passing the liquid through a filtrate flow path and also passing the liquid through flow paths in hollow fibers. SOLUTION: A liquid to be filtrated is introduced from both end openings 5a and 5b of a hollow fiber membrane module 1 into flow pathes in the hollow fibers 6 of the hollow fiber membrane 3. The permeated liquid passed through the hollow fiber membrane and eluted into a filtrate flow path 7 is discharged out of both flow outlets 8a and 8b. In the case a blocking section is formed in the flow paths in the hollow fibers 6, the liquid is not passed through the blocking section and a foam storage section is formed in the flow paths 6. In that case, when whether the foam storage section is formed in the flow paths 6 or not is judged, supersonic is emitted from outside the hollow fiber membrane module 1, namely outside a housing 2, and its reflection echoes are received and detected. The formation of foams can be simply and securely detected by the arrangement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting air bubbles stored in a hollow fiber membrane module. More specifically, the present invention relates to a method for detecting visible or invisible air bubbles accumulated in a hollow fiber membrane module from outside the housing of the module.

[0002] If a part of the hollow fiber loaded in the hollow fiber membrane module is closed for some reason, water cannot pass through after the closed part, and as a result, gas is stored in the hollow fiber. Therefore, according to the air bubble detection method of the present invention, the presence or absence of a blockage defect of the hollow fiber membrane can be easily detected from the outside of the hollow fiber membrane module together with the identification of the site.

[0003]

2. Description of the Related Art Generally, a hollow fiber membrane module has a structure in which a large number of hollow fiber membranes are loaded and fixed in an annular or cylindrical housing with both ends opened. Conventionally, it has been widely used in the separation of various liquids.

In using a hollow fiber membrane module,
It is preferable to use a module having a membrane area suitable for the intended separation characteristics. In general, the membrane area is proportional to the length and number of hollow fibers provided in the membrane module. Therefore, in the manufacturing process of the hollow fiber membrane module, the hollow area loaded in the housing so that the membrane area has a predetermined value according to the purpose of use. The number of yarns is determined.

[0005] However, in the manufacturing process of the hollow fiber, the inside of the hollow fiber is sometimes closed due to the occasional collapse of the hollow fiber or the entry of foreign matter into the hollow fiber.
If there is a blockage inside the hollow fiber, the effective membrane area of the hollow fiber membrane module does not reach a predetermined value, and the expected membrane separation ability cannot be obtained. Further, the membrane collapsed portion is susceptible to fatigue due to fluctuations in internal pressure during use, and has a risk of eventually breaking.

For this reason, when shipping a hollow fiber membrane module product, it is necessary to select and remove a hollow fiber membrane module in which a part of the hollow fiber is blocked due to crushing or mixing of foreign matter in advance.

[0007] In response to such demands, the presence or absence of blockage defects inside the hollow fiber has been conventionally confirmed by performing a non-passing confirmation test in the final step of the hollow fiber membrane module production. In this method, a liquid is filled in the hollow fiber membrane module (the flow path in the hollow fiber and the filtrate flow path), and in this state, light is applied from the outside of the module and transmitted through the module to form a transmission image appearing from the opposite surface. To confirm. That is, according to this method, when bubbles are stored inside the hollow fiber membrane module, the image of the light obtained through the portion is different in color from the image of the light transmitted through the portion filled with the liquid.
(Chromaticity), the closed portion can be detected by pattern formation due to the difference in chromaticity.

[0008]

However, since the non-passage confirmation test method utilizes a difference in light transmittance between a gas portion and a liquid portion as described above, a so-called opaque material having a large light absorption is used. In the case of a hollow fiber membrane module composed of a simple hollow fiber, no difference is obtained between the transmission image of the bubble portion and the transmission image of the liquid portion, and it is not possible to detect a blockage defect of the hollow fiber membrane.

An object of the present invention is to detect air bubbles in a hollow fiber membrane module which can be applied to hollow fiber membrane modules using any hollow fiber membrane, regardless of whether the material is hollow fiber or transparent or opaque. Is to provide a way.

It is another object of the present invention to provide a method for detecting a blockage defect in a hollow fiber membrane module and specifying a blockage site.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies day and night in order to solve the conventional problems concerning the hollow fiber membrane module. As a result, it has been found that air bubbles stored in the hollow fiber membrane module can be easily and accurately detected from outside the module housing regardless of the material of the module. The present invention is based on such findings.

That is, in the present invention, in a hollow fiber membrane module, ultrasonic waves are applied from the outside of the hollow fiber membrane module in a state where the liquid is passed through the filtrate flow path and the liquid is passed through the hollow fiber flow path from at least one open end. This is a method for detecting air bubbles in a hollow fiber membrane module, wherein the air bubbles are propagated and the reflected echo is detected.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for detecting air bubbles in a hollow fiber membrane module according to the present invention and an apparatus used for the method will be described with reference to the drawings. In addition,
The drawings are used to explain the present invention, and the present invention is not limited by these drawings.

FIG. 1 is a schematic view of a hollow fiber membrane module 1 to be inspected. A hollow fiber membrane 3 is provided inside a housing case 2. The ends of the hollow fiber membrane 3 are fixed at both ends of the housing case 2 with the ends opened.
a, 4b.

The hollow fiber membrane module 1 shown in FIG. 1 is an internal pressure filtration type module for filtering a target liquid from the inside to the outside of the hollow fiber membrane. The liquid to be filtered flows into the inner diameter channel 6 of the hollow fiber membrane 3 from one of the openings 5a, 5b at both ends of the module or alternately. The permeated liquid that has passed through and eluted into the filtrate flow path 7 flows out of the filtrate flow path 7 to the outlets 8a, 8a.
It flows out of the hollow fiber membrane module via b.

According to the present invention, when there is a blockage inside the hollow fiber of the hollow fiber membrane module 1 having such a configuration due to various factors such as crushing of the hollow fiber or mixing of foreign matter, according to the present invention, it is detected by the following method. can do.

First, a liquid is supplied from the outlet 8a or 8b of the hollow fiber membrane module to fill the filtrate flow path 7 with the liquid. In this state, the same liquid as above is supplied from at least one of the openings 5a or 5b of the module. Through the hollow fiber membrane channel 6. The liquid may be supplied to the filtrate flow path 7 and the hollow fiber membrane flow path 6 in any order. After the liquid is supplied to the hollow fiber membrane flow path 6, the liquid is supplied to the filtrate flow path 7. May be filled with a liquid. In the case of a module having no defects such as blockage in the hollow fiber membrane due to the feeding or filling of the liquid, FIG.
As shown in (1), both the filtrate flow path 7 and the hollow fiber membrane flow path 6 are filled with the liquid without storing bubbles. On the other hand, in the case of a module having a closed portion 9 in the hollow fiber membrane flow path 6, since the liquid does not pass through the closed portion, as shown in FIG. Is formed. Although FIG. 3 illustrates a case where there are two closing portions, the same applies to a case where there is only one closing portion. That is, in this case, when the liquid is supplied from one of the openings of the module, the liquid does not pass after the closed part, and thereafter, the liquid becomes the bubble storage part.

The presence or absence of bubbles in the hollow fiber membrane passage 6 is determined by
Next, ultrasonic waves are propagated from outside the hollow fiber membrane module, that is, outside the housing, and the reflected echo is detected and detected by receiving and detecting the reflected echo. Specifically, an ultrasonic pulse is propagated from the outer surface of the hollow fiber membrane module to be tested using a probe, and the ultrasonic pulse propagating as an elastic wave inside the module generates bubbles or bubbles on the housing wall of the module. Is reflected by the probe as a reflection signal (reflection echo). The reflected echo received by the probe is converted into an electric signal by an ultrasonic probe, and displayed on an oscilloscope as shown in FIG. Generally, the horizontal axis (corresponding to the time axis in FIG. 4) of the oscilloscope of the ultrasonic probe displays the propagation time of the ultrasonic wave, and the vertical axis (corresponds to the amplitude axis in FIG. 4) displays the amplitude of the ultrasonic wave. .

If the inside of the hollow fiber membrane module is made of a uniform material, the speed of sound propagating through the inside is constant. Therefore, the time until the pulse transmitted from the probe is received (propagation time of ultrasonic wave) , The distance to the reflection source can be measured. The approximate size of the reflection source can be estimated from the amplitude of the received ultrasonic wave. In FIG. 4, the probe is located almost directly above the air bubbles inside the hollow fiber membrane module,
Some of the ultrasonic waves hit the air bubbles and are reflected. The resulting bubble echo is located almost in the middle of the surface and bottom echoes where the ultrasonic pulse hits the module housing wall, looking at the time axis of the oscilloscope. It can be estimated that it is.

The air bubbles stored in the hollow fiber membrane module are as follows:
By making the reflected echo three-dimensional and visualized, it is possible to detect it more clearly and visually.

More specifically, as described above, a gate is applied between the surface echo and the bottom echo so that a signal peak value generated within this range can be taken out. An image in one section is obtained by vertically moving the hollow fiber membrane module relative to each other and modulating the luminance of the obtained signal level. This is a C scope (flat display) representing the information on the surface of the hollow fiber membrane module. Further, when the signal level is brightness-modulated by sensing the beam path on the horizontal axis, an image in the vertical section can be obtained.
This is a B scope (cross section display) that indicates information in a cross section in the depth direction of the hollow fiber membrane module. When the images of the B scope and the C scope are combined, a 3D scope (three-dimensional display) representing three-dimensional information of the hollow fiber membrane module is obtained. As an example, FIG. 5 obtained in the first embodiment is shown. Such an image can be easily obtained by performing data processing by a computer on bubble echo information obtained by the above-described ultrasonic probe.

In the above method, the liquid to be sent or filled into the hollow fiber membrane module is not particularly limited as long as it can transmit ultrasonic waves efficiently. Specific examples include water, oil, an aqueous glycerin solution, and chlorofluorocarbon, but water is preferred.

The method of the present invention can be applied to any hollow fiber membrane module without any restrictions on the materials such as the hollow fiber membrane and the housing that constitute the module. For example, as a material of the hollow fiber membrane and the housing, a polymer material is generally used, but a metal material, a ceramic material, and a ceramic material may be used depending on the application, and the present invention distinguishes these materials. The present invention can be applied to any module without question and regardless of whether each member is transparent or opaque.

[0024]

According to the present invention, the air bubbles stored in the hollow fiber membrane module can be easily detected from outside the module, that is, from outside the housing. In particular, the air bubble detection method of the present invention is also applied to a hollow fiber membrane module made of an opaque hollow fiber, which has a large light absorption and cannot be detected in a conventional non-passing confirmation test using light transmittance. This is an extremely useful method in that any method can be applied to the hollow fiber membrane module regardless of the material constituting the hollow fiber membrane module.

In general, bubbles in the hollow fiber membrane module are generated by closing the flow path in the hollow fiber membrane due to various factors such as crushing of the hollow fiber membrane and mixing of foreign matter. Therefore, according to the method of the present invention, a hollow fiber membrane module having a defective portion such as a blocked flow path in a hollow fiber membrane can be easily detected and selected, and as a result, a desired membrane separation ability is exhibited. It is possible to obtain a highly reliable hollow fiber membrane module.

In the case of a membrane module in which the hollow fiber membrane is formed of a hydrophobic material, in order to avoid losing water permeability of the membrane due to drying, the hollow fiber membrane is provided in the filtrate flow path and the hollow fiber membrane flow path. It is common to supply to a user in the form filled with liquids such as water. In the case of such a hollow fiber membrane module, if air bubbles exist in the module, the membrane dries at the contact portion between the air bubbles and the membrane material, and the liquid does not pass. As a result, a decrease in the effective membrane area, that is, a decrease in the membrane separation ability is caused.In the production of the hydrophobic hollow fiber membrane module, bubbles stored in the filtrate flow path are also detected. Liquid needs to be refilled. According to the present invention, it is possible to detect not only the bubbles stored in the flow path in the hollow fiber membrane, but also the bubbles stored in the flow path in the filtrate, and as a result, it is highly reliable to exhibit a desired membrane separation ability. A hollow fiber membrane module can be obtained.

[0027]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. Example 1 As a model hollow fiber membrane module having bubbles in a flow path in a hollow fiber membrane, both open ends of a hollow fiber membrane module prepared using 10,000 hollow fibers were sealed with resin, and added to the filtrate flow path. The membrane module was filled with water by feeding water from the outlet to fill the inside of the hollow fiber membrane flow path with air. In addition to this, the ultrasonic imaging system Myscope (manufactured by Hitachi Construction Machinery)
The ultrasonic wave was propagated from the housing surface of the membrane module through water and transmitted therethrough for imaging. FIG. 5 shows the results.

As can be seen from FIG. 5, the state of air (bubbles) stored in the flow path in the hollow fiber membrane is distinguished from the liquid in the filtrate flow path in the planar image thus obtained. Indicated. From this, by the ultrasonic treatment method of the present invention,
It was confirmed that bubbles stored in the hollow fiber membrane module could be detected. Example 2 A hollow fiber membrane module was prepared by mixing one fiber of a hollow fiber membrane having a blockage defect due to intentional collapse of the membrane. To this, water is fed into the filtrate channel from the outlet and filled, and then
Water was fed into the hollow fiber membrane flow channel from one open end. In this state, an image was formed by transmitting and transmitting ultrasonic waves from the housing surface of the membrane module through water using Myscope (manufactured by Hitachi Construction Machinery Co., Ltd.). as a result,
From the obtained plane image, it was confirmed that bubbles were stored in the flow path in the hollow fiber membrane after the closed portion (the side opposite to the water supply).

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a hollow fiber membrane module targeted by the present invention.

FIG. 2 is a diagram showing a hollow fiber membrane module in a state of being filled with a liquid.

FIG. 3 shows a state in which water is supplied or filled into a hollow fiber membrane module including a closed hollow fiber.

FIG. 4 is a diagram illustrating the principle of a method for detecting bubbles in a hollow fiber membrane module by ultrasonic detection according to the present invention.

FIG. 5 is a photograph instead of a drawing showing a result of measuring a hollow fiber membrane module containing bubbles therein by the ultrasonic probe method in Example 1.

[Explanation of symbols]

 1. 1. Hollow fiber membrane module Housing 3. Hollow fiber membrane 4a, 4b. Fixing member 5a, 5b. Opening 6. 6. Channel in hollow fiber membrane Filtrate channel 8a, 8b. Outlet 9. Closed part 10. Bubbles

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoichi Matsui 2-1-1 Katata, Otsu-shi, Shiga F-term in Toyobo Co., Ltd. Research Laboratory 2G047 AA08 AB01 BA03 BB06 BC09 DA02 DA03 EA10 4D006 GA02 HA02 JA02Z KA12 LA06 MA01 MB02 MC02 MC03 MC09

Claims (1)

[Claims] In a hollow fiber membrane module, an ultrasonic wave is propagated from outside the module in a state where a liquid is passed through a filtrate flow path and a liquid is passed from at least one open end to a hollow fiber flow path. A method for detecting bubbles in a hollow fiber membrane module, wherein the reflected echo is detected.