JPH0824590A - Method for filtering concentrated organic solution - Google Patents

Abstract

PURPOSE:To provide an in-to-out system filtration method without the working efficiency of the filter being decreased. CONSTITUTION:In the in-to-out system filtration using a hollow-fiber membrane module 5 with both open ends of a hollow-fiber membrane 6 separately bundled and fixed, a liq. to be treated is supplied to the hollow part of the membrane alternately from a first liq. inlet and outlet 4 and a second liq. inlet and outlet 9, a part of the liq. is discharged from the inlet and outlet to which the supply is stopped immediately after the liq. flow direction is changed, and the liq. is filtered. Consequently, the turbid matter accumulated close to the open end of the membrane is easily removed in the continuous filtration, and the concd. org. liq. is filtered without lowering the working efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of filtering a high-concentration organic liquid by using a hollow fiber membrane module containing a hollow fiber membrane in an in-out system.

[0002]

2. Description of the Related Art Hollow fiber membranes have an excellent filtration function, and since the membrane area of the filtration membrane that can be stored in a unit volume is large, it is possible to use drinking water of higher purity than conventional ones, sterile water for medical treatment, etc. Is widely used for various purposes.

The hollow fiber membrane module containing the hollow fiber membrane is used as a method of filtering from the hollow portion of the hollow fiber to the outside (into-out method) and from the outside of the hollow fiber to the hollow portion. There are two methods, filtering method (out-to-in method). With the into-out method, the passage resistance of the water to be treated inside the hollow fiber is large, and contaminants etc. in the water to be treated remain in the hollow part of the hollow fiber, and it is necessary to remove it. The out-to-in method has been used in many cases.

However, when the liquid to be treated contains pollutants at a relatively high concentration, the out-to-in filtration treatment causes the pollutants adhering to the outer surface of the hollow fibers to aggregate with each other. There is a problem in that the hollow fiber bundles are likely to be stuck together and the effective filtration membrane area is likely to decrease rapidly based on this phenomenon.

Various methods are known as a method for recovering the function of a hollow fiber membrane module, but it is a comparison that a sufficient function recovery process is performed after the hollow fiber bundles are thus fixed in one bundle. It was difficult. Therefore, from the viewpoint that the hollow fiber bundle will not be stuck in one,
Again, the filtration by the into-out method is receiving attention.

However, when the high-concentration organic liquid is filtered by the into-out method, in addition to the clogging of the pores of the hollow fiber membrane, the accumulation of suspended matter near the open end of the hollow fiber membrane. Is likely to occur, which contributes to a reduction in the filtration flow rate, and thus it is necessary to repeat the function recovery process frequently, thus lowering the operating efficiency of the filtration device.

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made extensive studies as to a filtration method of a hollow fiber filtration module which solves the above problems, and as a result, a double-ended opening type hollow fiber membrane module is used to remove a liquid to be treated. Supplied by alternately switching from two open ends, and immediately after switching the liquid flow, by discharging a part of the liquid to be treated from the stop side, the suspended matter accumulated near the open end of the hollow fiber membrane is washed away. Therefore, they have found that the frequency of the function recovery process can be reduced, and completed the present invention.

[0008]

That is, according to the present invention, a hollow fiber membrane whose both open ends are separately focused and fixed by a fixing member is provided in a container, and two liquids are provided facing each open end. Supply of the liquid to be treated in a filtration method in which the liquid to be treated is supplied from the hollow part side of the hollow fiber membrane and the permeate is collected from the outside of the hollow fiber membrane using a hollow fiber membrane module having a port Alternately switching from the two liquid inlets and outlets, and immediately after the switching of the liquid flow direction, there is a step of carrying out filtration while discharging a part of the liquid to be treated from the liquid inlet and outlet side where the supply is stopped. It is a method of filtering a high-concentration organic liquid.

In the hollow fiber membrane module used in the filtration method of the present invention, both open ends of the hollow fiber membrane are separately converged and fixed by the fixing members in the container constituting the module main body, and the hollow fiber membrane modules are connected to each of the fixing members to form two hollow ends. A liquid inlet / outlet for the liquid to be treated is provided, and a permeated liquid outlet is provided facing the outside of the hollow fiber membrane,
Various materials can be applied as long as they have a structure that can be used for in-out type filtration. As a typical example, the one used in FIG. 1 is exemplified, but as shown in FIG.
Even if the hollow fiber membranes are arranged in a letter shape and fixed by one fixing member, they can be used as long as both open ends of the hollow fiber membrane are partitioned so as to face different liquid inlets and outlets. In the case of this type of hollow fiber membrane module, the backwashing method described in JP-A-5-184884 can be applied. Further, as shown in FIG. 3, it is also possible to use a type in which a water pipe is provided inside and a liquid to be treated can be supplied from the same direction.

Although various hollow fiber membranes can be used in the hollow fiber membrane module, a porous membrane is preferable in terms of permeation flow rate. Various materials such as cellulose-based, polyolefin-based, polyvinyl alcohol-based, PMMA-based, and polysulfone-based can be used as the material for forming the hollow fiber membrane, but materials with high elongation such as polyethylene and polypropylene are usable. preferable. There are no particular restrictions on the pore diameter, porosity, film thickness, outer diameter, etc. in the case of a porous membrane, but considering the object to be removed and securing the membrane area per volume, the strength of the hollow fiber membrane, etc., a preferred example As a pore diameter of 0.01 to 1 μm, a porosity of 20 to 90%, and a film thickness of 5 to 30.
A range of 0 μm and an outer diameter of 20 to 2000 μm can be mentioned.

As the surface characteristics of the hollow fiber membrane, a so-called permanent hydrophilization membrane having a hydrophilic group on the membrane surface is desirable. When the membrane is hydrophobic, hydrophobic interaction works between the organic matter in the liquid to be treated and the surface of the hollow fiber membrane, causing adsorption of organic matter on the membrane surface, which leads to pore clogging and shortens the filtration life. Prone.

In the filtration method of the present invention, when performing the in-out type filtration using the hollow fiber membrane module as described above, the liquid to be treated is supplied by alternately switching from the two liquid inlets and outlets. Immediately after switching the above, the permeated liquid is taken out from the permeated liquid outlet while filtering a part of the liquid to be treated from the liquid inlet / outlet side where the supply is stopped.

FIG. 1 shows an example of an apparatus used for carrying out the filtration method of the present invention. The filtration method of the present invention will be described more specifically with reference to this figure. The liquid to be treated in the stock solution tank 1 is passed from the first liquid to be treated inlet / outlet 4 through the liquid feed pump 2 and the three-way valve 3 to the hollow fiber membrane module. The liquid to be treated is supplied to the inside of the hollow fiber membrane 5 from the hollow portion side of the hollow fiber membrane 6 toward the outside, and the permeated liquid is collected from the permeated liquid outlet 7. When the liquid to be treated is a high-concentration organic liquid, with time, the open end of the hollow fiber membrane facing the liquid inlet / outlet 4 and fixed by the fixing member 8 and the hollow portion of the hollow fiber membrane in the vicinity thereof become turbid. Quality is easy to accumulate,
In the porous hollow fiber membrane, this contributed to the decrease in the flow rate before the pores were clogged.

Therefore, in the present invention, the supply of the liquid to be treated is switched to the second liquid inlet / outlet 9 of the liquid to be treated which has not been used until then by switching the three-way valve 3 at a predetermined time. Immediately after this switching, the valve 10 is opened, and the operation is carried out by a method similar to the cross flow method in which a part of the liquid to be treated is filtered from the liquid inlet / outlet 4 which has been used until then while returning to the stock liquid tank. Then, the suspended matter accumulated in the vicinity of the open end of the hollow fiber membrane facing the liquid inlet / outlet 4 being used is washed away by the circulating liquid to be treated. The valve 10 may be opened after that, but it is normally closed because the amount of permeated liquid in the hollow fiber membrane decreases. Instead of opening the valve 10, the valve 13 may be opened and a part of the liquid to be treated may be taken out as a highly concentrated turbid liquid. After the filtration is continued in this way, the supply of the liquid to be treated is switched to the liquid inlet / outlet port 4 again by switching the three-way valve 3 at a predetermined time, the valve 11 is opened, and the hollow fiber membrane facing the liquid inlet / outlet port 9 is opened. The suspended matter accumulated near the open end is washed away. By alternately switching the liquid flow direction in this manner, suspended matter does not accumulate at both ends of the opening of the hollow fiber membrane. Therefore, the function recovery process of the hollow fiber membrane module is performed with the pores of the hollow fiber membrane. It only has to be done for clogging.

The supply of the liquid to be treated in the method of the present invention may be switched at regular intervals or when the permeate flow rate is reduced to a predetermined value. It can be appropriately selected depending on the properties of the high-concentration organic liquid to be supplied. Also, the liquid to be treated is discharged from the liquid inlet / outlet on the supply stop side immediately after the liquid flow is switched in order to flush away suspended solids accumulated in the vicinity of the open end of the hollow fiber membrane. Is enough.

When performing backwashing as a function recovery treatment of the hollow fiber membrane, after closing the three-way valve 3, the valves 10 and 11, the valve 12 is opened to supply compressed air from the permeate outlet. The backwash water can be efficiently taken out from the opened valves 13 and 14.

[0017]

EFFECTS OF THE INVENTION According to the filtration method of the present invention, since the suspended matter accumulated in the vicinity of the open end of the hollow fiber membrane can be easily removed during the continuous filtration operation in the in-out type filtration, the hollow fiber membrane module It became possible to filter a high-concentration organic liquid without lowering the operating efficiency of.

[Brief description of drawings]

FIG. 1 is an example of an apparatus used in the filtration method of the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of a hollow fiber membrane module that can be used in the filtration method of the present invention.

FIG. 3 is a schematic cross-sectional view showing an example of a hollow fiber membrane module that can be used in the filtration method of the present invention.

[Explanation of symbols]

 1 undiluted solution tank 2 liquid feed pump 3 three-way valve 4 first treated liquid inlet / outlet 5 hollow fiber membrane module 6 hollow fiber membrane 7 permeated liquid outlet 8 fixing member 9 second treated liquid inlet / outlet 10-14 valve 15 water conduit

Claims (1)

[Claims] 1. A hollow fiber membrane in which a hollow fiber membrane having both open ends thereof separately focused and fixed by a fixing member is provided in a container, and two liquid inlets and outlets are provided so as to face each of the fixing members. In the filtration method in which the liquid to be treated is supplied to the hollow portion of the hollow fiber membrane using the module and the permeated liquid is collected from the outside of the hollow fiber membrane, the supply of the liquid to be treated is alternately switched from the two liquid inlets and outlets. A method for filtering a high-concentration organic liquid, which comprises performing a filtration while discharging a part of the liquid to be treated from the liquid inlet / outlet side where the supply is stopped immediately after switching the liquid flow direction.