JPS6287206A - Method for washing pipe material for precision filtration - Google Patents

Abstract

PURPOSE:To enhance the washing effect by charging a pressurized washing liq. contg. fine air bubbles having a diameter in the specified range into the inner pipeline or the outer pipeline of the precision filtration pipe material and permeating the fine air bubbles through the micropores of a semipermeable membrane. CONSTITUTION:In the precision filter 1 using the bundle body 4 of the precision filtration pipe material (a) consisting of the semipermeable membrane, the pressurized washing liq. contg. fine air bubbles such as micro air or colloidal air is inversely charged from an outlet 4, when the micropores of the semipermeable membrane are clogged after successive filtrations of a liq. to be treated. The fine air bubbles penetrate into the micropores, the diameter of the fine bubbles is increased by the pressure difference as the fine bubbles move to the outside of the pipe, and the substance clogging the micropores is pushed out to the outside of the pipe. The air bubble flowing out to the outside of the pipe material (a) is recovered from an air vent 7. Then air is supplied from the outlet 4 to clean the inside of the inner pipeline, a washing liq. obtained by mixing fine air bubbles into a chemical soln. such as NaOH capable of dissolving the substance in the liq. to be treated is further charged and finally the inside is washed with water.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention is used to filter the treated liquid by ultrafiltration by being immersed in a liquid to be treated. The present invention relates to a method for cleaning a precision filtration tube from which a permeate is extracted.

<Prior art> As shown in Fig. 1, precision filtration tube material a is formed by forming a semipermeable membrane such as cellulose or polymer membrane such as polyamide into a hollow tube shape, and is capable of semipermeable Hb. Internal pipe C
is formed. The diameter of the tube material a is extremely thin, for example, an outer diameter of 85 mm and an inner diameter of 42 mm.

The tube material a is immersed in a pressurized liquid to be treated at a pressure of 0.5 to 5 Kg/crn', or a pressurized liquid to be treated is injected into the inner pipe line C to make the semi-permeable! This method is applied to ultrafiltration that separates low-molecular substances by the action of lb. That is, when immersing in the liquid to be treated (referred to as internal extraction), low molecular substances such as salts and sugars in the liquid to be treated permeate through the semi-permeable membrane to the inside of the tube material a due to the pressure. , is taken out as a permeated liquid from the inner pipe C, and the polymer substance remains in the liquid to be treated. Furthermore, when the liquid to be treated is allowed to flow through the inner pipe C (referred to as external extraction), the low molecular weight substance permeates the semipermeable membrane to the outside, and the permeated liquid is extracted from outside the tube.

In this case, for example, in the case of cellulose, the maximum molecular weight that can be separated (molecular weight cut off) is 15,000, and in the case of polyamide, etc., it is 8,000. In this manner, by appropriately selecting the material, only substances with a desired molecular weight can be separated, and precision filtration becomes possible.

<Problems to be solved by the invention> Such semi-transparent! In precision filtration tube material a using Ib, the semi-transparent! If the micropores d of Ib become clogged with polymers or the like, the filtration function will be degraded, and the supply pressure of the liquid will need to be increased, making it necessary to clean it. By the way, conventionally, when the clogging occurs, air or water is supplied to the inner pipe line. However, with each method, a high cleaning effect could not be obtained and a long cleaning process was required. This is because even if the micropores d are clogged with air or water, they tend to flow out of the tube through the gaps, making it impossible to push out the clogged substances. This seems to be caused by this.

An object of the present invention is to provide a method for cleaning a precision filtration tube material a, which has a high cleaning effect.

Means for Solving the Problems> The present invention provides a pressure washing method containing fine bubbles y with an outer diameter of 10 l to 0.001 g in the inner pipe line or outside of the microfiltration pipe material a. A liquid X is introduced into the semipermeable membrane, and the microbubbles y permeate through the micropores d of the semipermeable membrane.

It is preferable that the size of the microbubbles y be similar to the micropores d of the pipe material a to which precision mesh is applied, but the size of the microbubbles y is influenced by the water pressure inside and outside the pipe. It is difficult to set a precise setting because of the

Effect> The case of inside extraction shown in FIG. 1 will be explained. The microbubbles y in the pressure washing liquid X form micropores d due to their internal pressure.
The substance 2 that is clogging the micropores d is removed. In this case, the diameter of the bubble y is determined by the balance between its internal pressure and external pressure, and since the outside of the precision filtration tube material a has a lower pressure than the inside of the tube, inside the micropore d, the outside of the tube is The diameter becomes larger as you move towards the end. Due to this, the substance 2 in the micropores d is effectively pushed out, thereby cleaning the micropores d.

In the case of outside extraction, the flow of microbubbles y is reversed, but
Its operation is the same as above, and the explanation will be omitted.

<Example> FIG. 3 shows an example of a precision filtration device 1 using a tube material a for precision filtration, which is used for internal extraction.

Here, reference numeral 2 denotes a long water flow pipe, on the top of which a bundle 4 in which a large number of the pipe materials a are bundled is joined at its upper end, and the inner tube of each pipe material a opens at the upper end edge. The passage C is communicated only with the outflow O4 formed at the upper part of the water pipe 2. The end of the bundle 3 is glued to close the lower end of the inner channel C.

Further, an inlet 5 through which the liquid to be treated flows is formed at the upper side of the water pipe 2, and an outlet 6 through which the liquid to be treated flows down at the lower end of the water pipe 2. Further, an air vent lower is provided on the upper side of the water pipe 2.

In the precision filtration device Ml having the above structure, the liquid to be treated flows in from the inlet 5, flows down along the circumferential surface of each tube material a of the bundle 3, and is discharged from the outlet 6. At this time, a reverse osmosis phenomenon occurs on the circumferential surface of each tube material a of the bundle 3 due to the pressure of the liquid to be treated that is supplied into the water pipe 2. Therefore, in the semi-permeable Hb micropores d of the tube material a,
The solvent and low-molecular substances permeate through the semipermeable membrane and enter the inner pipe C, and the high-molecular substances remain in the liquid to be treated.

The permeated liquid that has flowed into the inner pipe C is taken out from the microfiltration device l through the outlet 4.

However, if this process is continued, the micropores d of the semipermeable membrane will become clogged. Therefore, the cleaning method of the present invention is applied.

That is, as a first step, a pressurized cleaning liquid X containing fine bubbles y such as micro air or colloidal air in water is introduced from the outlet 4. Since the cleaning liquid contains fine bubbles y whose shape cannot be determined visually, it is visually recognized as a cloudy state.

As schematically shown in FIG. 2, due to this inflow, the fine bubbles y in the cleaning liquid X enter the fine holes d due to the pressure difference between the pressure of the cleaning liquid X and the pressure around the bundle 3. By the way, since the diameter of the bubble y is determined by the balance between its internal pressure and external pressure, the diameter becomes larger as it moves toward the outside of the tube within the micropore d. At this time, the substance 2 clogged within the micropores d is pushed out of the tube. The air bubbles y that have flowed out of the tube material a are collected from the air vent lower.

Next, in a second step, air is supplied from the outlet 4 to clean the inside of the inner pipe C.

Furthermore, in a third step, the cleaning liquid in which the fine bubbles y are mixed is introduced from the outlet 4 into a chemical solution such as caustic soda or hydrochloric acid that can dissolve substances in the liquid to be treated. As a result, the substance 2 remaining in the micropores d even after the first step is removed.
While melting with the chemical solution, the above-mentioned fine bubbles y
It is pushed out of the tube by the action of

This is followed by washing with water to complete the washing process and eliminate the substance Z.

In this cleaning step, the above-mentioned steps can be arbitrarily combined, and each step may be repeated multiple times.

In addition, in order to mix the fine bubbles y into the cleaning liquid X, under high pressure,
This can be done by known means of ejecting air into the liquid using an ejector.

<Effects of the Invention> As described above, the present invention provides the following steps to clean the pipe material a:
The fine bubbles y in the cleaning liquid It has a positive effect.

[Brief explanation of drawings]

FIG. 1 is an enlarged longitudinal sectional view of tube material a, and FIG. 2 is a longitudinal side view of the semipermeable membrane of tube material a further enlarged to show the dynamics of bubbles.
3rd FI4 is a longitudinal cross-sectional side view of the precision filtration device 1. a; Pipe material b; Semipermeable membrane C; Inner pipe X; Cleaning liquid y:
Microbubbles l; precision filtration device 2; water pipe 3; bundle 4; outflow port 5; inflow port 6; outflow port

Claims (1)

[Claims] A tube with an outer diameter of 10 μm to 0.001 μm is placed inside or outside the tube of a microfiltration tube material made of a semipermeable membrane, from which the permeate is extracted from the inner tube or outside the tube after being subjected to ultrafiltration. A method for cleaning tube material for precision filtration, characterized by flowing a pressurized cleaning liquid containing fine bubbles within a range of 100 to 100 mm, and allowing the fine bubbles to permeate through the fine pores of a semipermeable membrane.