JP2000300970A - Foam detecting method in hollow fiber membrane module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make surely detectable the generation of foams in a hollow fiber membrane module regardless of the kind of the material of the hollow fiber membrane by transmitting X-rays through the module in the state of passing a liquid through filtrate flow paths and also passing the liquid through paths in hollow fibers and detecting the dose fluctuation of the transmitted X-rays thus provided. SOLUTION: A liquid to be filtered is introduced from both end openings 5a and 5b of a hollow fiber membrane module 1 into the flow pathes in the hollow fibers 6 of the hollow fiber membrane 3. The liquid permeated through the hollow fiber membrane 3 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 path in the hollow fibers, the liquid is not passed through the blocking section and a foam storage section is formed in the inner diameter flow path. In that case, when whether the foam storage section is formed in the flow path in the hollow fibers or not is judged, X-rays are emitted from outside the hollow fiber membrane 1, namely outside a housing 2 and the dose fluctuation of X-rays provided by the transmission in the hollow fiber membrane module 1 is detected.

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 to solve the above-mentioned conventional problems with the hollow fiber membrane module. However, the present inventors utilize X-rays having a high ability to penetrate substances. 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, the present invention relates to a hollow fiber membrane module, in which a liquid passes through a filtrate flow path and a liquid passes through at least one open end into a hollow fiber flow path to transmit X-rays through the module. And detecting a change in the dose of the transmitted X-ray obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for detecting 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. The drawings are used for explaining the present invention,
The present invention is not limited at all 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, X-rays are irradiated from the outside of the hollow fiber membrane module, that is, from the outside of the housing, and the change in the dose of X-rays obtained through the inside of the hollow fiber membrane module is detected.

That is, if bubbles are stored inside the hollow fiber membrane module, the dose of X-rays passing through this portion is:
This is different from the dose of X-rays transmitted through an area filled with liquid (a so-called healthy area). The present invention detects and records the difference (dose change) in the dose of X-rays transmitted through the bubble storage region and the healthy region by using, for example, a change in the degree of blackening of an X-ray film, and records the difference in the amount of bubbles. It detects the presence or absence.

FIG. 4 schematically shows the state of transmission of X-rays when bubbles are present inside the hollow fiber membrane module. Points A and B in FIG. 4 indicate positions at which X-rays that have passed through a portion where bubbles are present and a region in which the inside of the membrane module is completely filled with liquid (healthy region) respectively. The points A and B are the same in that the X-rays pass through the housing, the filling liquid in the membrane module and the hollow fiber membrane, and the difference in the dose of the transmitted X-rays at the points A and B depends on the inside of the membrane module. Only depends on the presence of the bubbles.

In general, when an X-ray passes through a substance having a thickness of xcm, if the intensity (dose rate) of the X-ray before transmission is defined as I ₀ , the intensity I (transmission dose rate) of the X-ray after transmission is assumed. ) Is represented by the following equation (see FIG. 5).

[0022]

(Equation 1) In the above equation, μ is an absorption coefficient, which is a value determined by the type of a substance to be transmitted.

Therefore, in the case of the hollow fiber membrane module,
Since the absorption coefficient of air is significantly smaller than the absorption coefficient of liquid, the transmitted X-rays that reach point A are less attenuated than the transmitted X-rays that reach point B by the amount transmitted through the bubble portion. . In other words, the transmitted X-ray that reaches point B has a large attenuation by the amount that has not passed through the gas portion but has passed through the liquid portion. Therefore, the magnitude relationship between the transmitted X-ray I _B (dose rate) at the point B and the transmitted X-ray I _A (dose rate) at point A is as I _A> I _B. Transmission X-ray dose that reaches the points A and B (dose rate I × exposure time t), so likewise the I _A t> I _B t, when baked this example, X-ray film, the bubble portion The degree of blackening (density) of the point A obtained through transmission becomes stronger (darker) than that of the point B, that is, the other region not including bubbles. Therefore, when an image having a dark black portion is obtained in a transmission photograph such as an X-ray film, it can be determined that the hollow fiber membrane module has bubbles inside.

In carrying out the above method, necessary devices and materials include an X-ray generator, an X-ray film, and a development facility, which serve as a radiation source. A transmissometer and a gradation meter for evaluating the image quality of the light-sensitive paper and the transmission photograph may be provided.

The detection method of the present invention can widely use, as an X-ray source, a low-energy X-ray or a medium-energy X-ray such as a tube voltage of 300 kV and a tube current of 5 mA. Any X-ray generator with a source can be used.

In the method of the present invention, the liquid to be fed or filled into the hollow fiber membrane module is not particularly limited, and examples thereof include water, oil, glycerin aqueous solution, and CFC. From the viewpoint of detectability, a liquid having a large absorption coefficient is preferable.

The change in the transmitted dose of X-rays based on the presence of air bubbles in the hollow fiber membrane module, that is, the difference in density can be identified by the visualization process by printing on the X-ray film as described above. The processing is not particularly limited to this, and other image processing can be arbitrarily used. As an example, as shown in the embodiment, a method of detecting a transmission line obtained by transmitting an X-ray into the hollow fiber membrane module with an image intensifier and integrating the transmission line with a CCD camera to obtain an image. Can be mentioned.

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, which 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.

[0029]

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 loss of 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.

[0032]

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. A micro focus X-ray inspection device (MBR-130)
MF-1; manufactured by Hitachi, Ltd.), a tube voltage of 50 kV, a tube current of 100 μA, and a focal point of 1 from the outside of the membrane module housing.
X-rays were transmitted under the condition of 0 μm, the transmitted light was detected by an image intensifier, and an image was formed by a CCD camera under the conditions of 100 integrated frames and 20 times magnification. FIG. 6 shows the results. As can be seen from these figures, in the images obtained in this manner, a state in which the air in the hollow fiber membrane flow path was filled was observed separately from the liquid in the filtrate flow path. From this, it was confirmed that the X-ray transmission method of the present invention can detect bubbles stored in the hollow fiber membrane module. Example 2 As a model hollow fiber membrane module, both open ends of a hollow fiber membrane module prepared using 10,000 hollow fibers were sealed with a resin, and water was fed from an outlet into a filtrate flow path and filled. As a result, a membrane module in which the inside of the hollow fiber membrane channel was filled with air was manufactured. Then, air having a diameter of 0.5 mm was mixed into the filtrate channel by feeding air from the outlet of the membrane module. Using a microfocus X-ray inspection device (MBR-130MF-1; manufactured by Hitachi, Ltd.), X was applied from outside the membrane module housing under the conditions of a tube voltage of 50 kV, a tube current of 100 μA, and a focus of 10 μm.
The transmitted light is detected by an image intensifier, and the total number of frames is 10 by a CCD camera.
An image was formed under the conditions of 0 and a magnification of 40 times. FIG. 7 shows the results.

As can be seen from the figure, it was observed that the image obtained in this manner was filled with air in the flow path in the hollow fiber membrane and bubbles were stored in the flow path of the filtrate. From this, it was confirmed that the X-ray transmission method of the present invention can detect bubbles stored in the hollow fiber membrane module.

[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 showing the principle of a method for detecting bubbles in a hollow fiber membrane module by the X-ray transmission method of the present invention.

FIG. 5 is a diagram illustrating a basic principle of an X-ray transmission method.

FIG. 6 is a drawing substitute photograph of an image showing a result of measuring a hollow fiber membrane module containing air bubbles therein by an X-ray transmission method in Example 1. In the figure, horizontal stripes shown in white indicate bubbles inside the hollow fiber.

FIG. 7 is a photograph substituted for a drawing showing a result of measuring a hollow fiber membrane module containing air bubbles therein by an X-ray transmission method in Example 1. In the figure, the horizontal stripes shown in white are bubbles inside the hollow fiber, and the round white parts are bubbles stored in the filtrate channel.

[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

Continuation of the front page (72) Inventor Yoichi Matsui 2-1-1 Katata, Otsu-shi, Shiga F-term in Toyobo Co., Ltd. General Research Laboratory 4D006 GA02 HA01 LA06 LA10

Claims (1)

[Claims] In a hollow fiber membrane module, a liquid is passed through a filtrate flow path, and a liquid is passed through at least one open end into a hollow fiber flow path.
A method for detecting air bubbles in a hollow fiber membrane module, comprising transmitting a X-ray and detecting a change in the dose of the transmitted X-ray obtained.