JPS6043162B2 - Method and device for filtering liquids containing suspended matter - Google Patents

Description

Detailed Description of the Invention The present invention provides a hollow fiber-like structure in which the upper end is fixed with a seal, the lower end is sealed with an adhesive, and the hollow fibers are fixed to form a free end. Regarding a method and apparatus for filtering a liquid containing suspended substances using a porous polymer membrane, more specifically, when a porous polymer membrane is washed by gas backflow, the liquid containing suspended substances present in the apparatus is The present invention relates to a filtration method and device that prevent cleaning gas from being carried out of the device.

Hollow fiber porous polymer membranes have a large membrane area and are industrially used as membranes for ultrafiltration and reverse osmosis because they have excellent pressure resistance and chemical resistance.

However, as time passes for the filtration process, a large amount of suspended matter adheres to the surface of the hollow fiber membrane, and the filtration ability gradually decreases.

As a means of restoring its filtration ability,
As disclosed in the Shinaba issue, air is continuously introduced in the opposite direction to the filtration at appropriate times to generate a large number of air bubbles from the membrane to peel off the attached suspended matter, and the air vibrates the membrane to remove the attached suspended matter. Methods have been proposed to remove suspended solids. In this method, it is possible to effectively strip and remove suspended matter on the membrane, but since backflow is performed with the module filled with liquid, a large amount of suspended matter present in the filtration device can be removed. The liquid contained in the backwashing air is carried along with the backwashing air by an amount equivalent to the holdup of the ventilation air, and is led out of the device from the backwashing gas outlet.

If the suspended matter contained in this liquid is, for example, radioactive suspended matter from a nuclear facility, or suspended matter containing harmful substances from food, pharmaceutical, or chemical industrial facilities, etc., this will lead to the spread of contamination. It is not preferable to lead gas containing such suspended matter out of the device. The object of the present invention is to provide a method and a filtration device that minimize the amount of liquid containing suspended matter entrained in this backwashing gas and prevent the spread of contamination. be. As the backwashing gas, a treatment liquid or suspended matter and an inert gas, such as air, nitrogen, or an inert gas, can be used. Among them, air and nitrogen are particularly practical. This object of the present invention is achieved by, when cleaning a porous polymer membrane by gas backwashing, by drawing out in advance only the amount of liquid that overflows due to gas backwashing.

That is, the present invention filters a liquid containing a suspended substance using at least one perforation membrane bundle formed by bundling a large number of hollow fiber-like porous polymer membranes, separates the permeate liquid, and A method for cleaning a filtration membrane by gas backwashing, characterized in that when performing gas backwash cleaning of the offshore filtration membrane, only an overflow amount of liquid is extracted in advance, and then gas backwashing is performed. The method consists of a filtration liquid part having an Oki filtrate outlet and a backwashing gas inlet, and a filtrate band part having a P filtrate inlet, a undiluted solution outlet and a backwashing gas outlet, and a hollow fiber-like filter. A liquid containing suspended matter is filtered through at least one permeable membrane bundle made up of a large number of porous polymer membranes bundled together to separate the permeate liquid, and the permeate membrane is passed through a gas inverter. Although it was designed to be cleaned by washing, the offshore passage device was used. ”, a partition plate is provided to support the filtration membrane bundle and separate the offshore permeate zone and the undiluted solution zone, and an overflow liquid outlet is provided below the backwash gas outlet of the undiluted solution zone. This is an off-shore passage device featuring the following.

Hereinafter, a second method for filtrating a liquid containing suspended matter and a filtration apparatus according to the present invention will be explained. The hollow fiber membrane used in the present invention is microfiltration or ultrafiltration. It can be used for evaporation, etc., and when compressed gas is introduced from the inside, a large number of bubbles are generated from the surface.

Generally used hollow fiber ultrafiltration membranes have a dense layer as an active layer, but these membranes do not produce bubbles when compressed gas is introduced. Cannot be used for invention methods. Hollow fiber membranes that can be used are those formed into hollow fibers of polymeric substances such as cellulose acetate, polyacrylonitrile, methacrylic ester, polyamide, polyester, polyvinyl alcohol, and polyolefin, and can be formed using a wet method or It can be manufactured by a dry method or the like. In particular, the average diameter of PVA-based films is approximately 0.02.
The hollow fiber membrane used in the method of the present invention has a structure in which micropores of ~2μ are arranged substantially uniformly in the cross section, and the bubble point is 0.1 to 20, making it easy to generate bubbles. It is excellent. The hollow fiber membrane used in the present invention has an outer diameter of 300 to 3000 μm and a thickness of about 50 to 500 μm, and at least one bundle of several tens to hundreds of thousands of hollow fiber membranes is provided in the apparatus. In order to prevent this membrane bundle from being damaged due to mutual interference with other membrane bundles, it is desirable to protect it by encasing it in a protective outer cylinder such as a cylinder.

In the present invention, liquids containing suspended matter include radioactive waste liquids from nuclear facilities, waste liquids containing harmful substances, etc. from food, pharmaceutical, and chemical industries.

In addition, the pressure of the compressed air during air backwashing must be high enough to generate a large number of bubbles from the membrane surface, and is approximately 0.1 to 2 msec pressure, preferably 2 to 5 atm. is preferred.

The overflow liquid removal during gas backwashing in the method of the present invention is as follows:
It is important that the liquid is withdrawn to the extent that it is not entrained in the backwash gas due to gas hold-up.

To extract the liquid, open the stock solution outlet provided at the bottom of the device in advance during backwashing and draw out a predetermined amount of liquid, or install an overflow liquid outlet at the bottom of the backwash gas outlet and open this port. You can also drain the liquid. Hereinafter, the present invention will be explained based on the drawings.

FIG. 1 is a partially cutaway sectional view showing an embodiment of the device according to the present invention.

An overflow container 1 containing an overflow membrane bundle 4 is partitioned by a partition plate 2 into an overflow liquid zone A in the upper direction and an undiluted liquid zone B in the lower direction.

The partition plate 2 is further provided with one or more protective cylinders 3 arranged vertically and containing the above-mentioned Oki membrane bundles 4 whose lower ends are sealed.
At least one hole 5 is provided in the side of the cylinder 3. The filtrate zone A has an offshore filtrate outlet 6 and a backwash gas inlet 7.
The undiluted solution section B has an Okinawa undiluted solution inlet 8, an undiluted solution outlet 9, and a backwash gas outlet 10. Further, in the stock solution zone B, an overflow liquid extraction port 11, which constitutes the main part of the present invention, is provided at a position below the backwash gas outlet 10. Next, a method for passing offshore using the above device will be explained.

A stock solution containing suspended matter is introduced into the stock solution band B from the stock solution inlet 8. The suspended matter is blocked by the membrane of the p-diaphragm concentrator 4,
The filtrate passes through the hollow fibers, is guided to the permeate zone A, and is taken out of the container 1 from the permeate outlet 6. As the filtration treatment time increases, a large amount of suspended matter adheres to the surface of the membrane, and the filtration ability decreases. Therefore, the backwash air inlet 7 of the p-filter zone A
from? Backwash gas is pressurized into the hollow fibers of the membrane bundle 4.
When introducing a backwashing gas, the membrane of the filter membrane bundle 4 is immersed in a liquid because the backwashing effect is reduced in a dry state. By this backwashing gas, the offshore filter membrane focusing body 4 is
Numerous bubbles are generated from the surface of the membrane, and the attached suspended matter is removed and washed. This backwashing gas is led out of the offshore vessel 1 from the backwashing gas outlet 10. Here, when the suspended matter adhering to the membrane is washed with the backwashing gas, the liquid containing a large amount of suspended matter becomes foamy, and the apparent volume becomes
The amount increases by the amount of gas held up, and is entrained by the backwashing gas and overflows from the backwashing gas outlet 10.
If the liquid entrained in the backwashing gas contains a radioactive suspension as mentioned above, it must be minimized as it may lead to the spread of contamination. Therefore, in the present invention, an overflow liquid extraction port 11 is provided below the backwash gas outlet 10, and the overflow liquid corresponding to the gas hold-up is removed from the overflow vessel 1 in advance before performing gas backwashing. The backwash outlet 10 is removed by extracting the gas and then performing gas backwashing.
The amount of entrained liquid containing suspended matter from the tank is minimized.

Next, a method for purifying radioactive liquid containing radioactive suspension using the apparatus of the present invention will be explained.

Liquids containing radioactive waste and radioactive liquids from water containing radioactivity must be completely disposed of under very strict conditions from the viewpoint of safety.

Therefore, the p-filtration method and apparatus of the present invention are preferably used. FIG. 2 is a process sheet showing a method for purifying radioactive liquid using the apparatus according to the present invention.

Reference numeral 21 denotes a filtering vessel containing a hollow fiber filtration membrane 22.

23 is a tank for receiving backwash liquid from the p-filtration container 21;
4 is a backwash gas purification device with a built-in demister 25.

A radioactive stock solution containing a radioactive suspension is introduced into the filtration container 21 from a stock solution supply line 26 .

The introduced stock solution is filtered through a hollow fiber filtration membrane 22, and radioactive suspensions contained in the stock solution are removed. The purified offshore filtrate is led out of the offshore filtrate container 21 from the offshore filtrate line 27, and is reused as a purified fluid or discharged outside the system. When suspended matter is deposited on the hollow fiber filtration membrane 22 and the drinking capacity is reduced,
Backwashing gas is sent to restore the function of the hollow fiber membrane 22, but in the case of the present invention, the overflow of the overflow container 21 is prevented in advance before sending the backwashing gas as described above. From the effluent outlet line 28 , the effluent concentrate is conducted into the backwash liquid receiving tank 23 until it reaches the level of its overflow outlet line 28 . Next, air is forced into the overnight vessel 21 from the backwash gas supply line 29, and the radioactive suspension adhering to the surface of the hollow fiber membrane 22 is peeled off and removed. The backwash gas is led out of the offshore vessel 21 from the backwash gas outlet line 30. Since the overflow liquid is led out of the overflow container 21 from the overflow liquid outlet line 28, almost no liquid containing suspended substances is contained from the backwash gas outlet line 30, but from the viewpoint of radioactive liquid. Therefore, even a small amount of suspended solids must be removed. Therefore, the backwash gas containing mist with a small amount of suspended matter from the backwash gas outlet line 30 is temporarily led to the backwash liquid receiving tank 23.

This backwashing gas purification device 2 includes a built-in demister 25 that drops a small amount of suspended liquid in the mist in the backwashing liquid receiving tank 23 and is filled with wire mesh from the backwashing gas line 31.
4, and after completely removing the remaining suspended matter in the mist, it is discharged from the purified gas discharge line 32.

In addition, in order to prevent the level of radioactivity from increasing due to the mist adhering to the piping and inside the pipe leading to the outlet of the demister 25 of this backwash gas purification device 24, the filtrate obtained in the filtration container 21 is used. The filtrate bypass line of the washing liquid line 3
3 to the backwash gas purification device 24 for cleaning. This cleaning liquid is backwashed from the cleaning liquid extraction line 34) in the liquid receiving tank 2.
Lead to 3. The backwash liquid containing the concentrated suspension in the filter container 21 is collected into the backwash liquid receiving tank 23 from the backwash liquid extraction line 35.

The backwash liquid in the tank 23 is sent by a transport pump 36 to a storage tank or to a plastic solidification, asphalt solidification, or cement solidification facility for treatment. below,
The present invention will be specifically explained based on Examples.

Example Made from polyvinyl alcohol (hereinafter referred to as PVA) based polymer, outer diameter 900μ, inner diameter 450μ, pure water permeation rate (K) 200′1hr-Atrrl-i (membrane area is calculated on the outer wall surface), bubble point eye. 5atn1. A hollow fiber with a structure of 300 pots of hollow fibers having an effective length of 100C7X is fixed at the upper end with a seal, the opening of each hollow fiber at the lower end is sealed with adhesive, and the hollow fibers are not fixed together and form free ends. Form a membrane bundle.

Its membrane area is 7d. A hollow fiber filtration membrane bundle 1 having the above filtration area was installed in the filtration apparatus shown in FIG. 1, and the amount of suspended solids entrained in the backwash air was measured. 5 ppm of iron oxide with an average particle size of 0.6 μm was added to the sake stock solution as a suspended substance.

The above stock solution was introduced into the apparatus shown in FIG. 1 and subjected to filtration. After attaching 30VId of iron oxide to the membrane, the air pressure was increased to 3.
Air was aerated with 5k91cr1-G for 5 minutes in the opposite flow to that used during drinking, and the amount of suspended matter in the air discharged from the filtration device was collected with glass wool. The results are as follows. Note that air hold-up during ventilation was approximately 20%, and the concentration of suspended matter on the stock solution side was 13,000 ppm.
(1) If the liquid is not drained beforehand: 2.01mgI air (2) If the liquid is drained beforehand: 0.01wLgId
When the water from the air hold-up is removed from the air, it is 11% lower than when the suspended solids entrained in the air are not removed.
It was possible to reduce it to 200.

As explained above, in the present invention, when a porous polymer membrane is cleaned by gas backwashing, the liquid containing suspended matter is not carried out with the backwashing gas and led out of the apparatus. Since this is prevented, it is suitably used for evaporation of liquids containing suspended matter.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway sectional view showing an embodiment of the apparatus according to the present invention, and FIG. 2 is a process sheet showing a method for purifying radioactive liquid using the apparatus according to the present invention. 1: Overflow container, 2: Partition plate, 3: Protective cylinder, 4: Overflow membrane bundle, 5: Hole, 6: Overflow liquid outlet, 7: Backwash gas inlet, 8: Overflow undiluted liquid introduction Port, 9: Stock solution outlet, 10: Backwash gas outlet, 11: Overflow liquid outlet, A: Sake filter zone, B: Stock solution zone, 21: P filter container, 22: Hollow fiber filter Membrane, 23: Backwash liquid receiving tank, 24: Backwash gas purification device, 2
5: Demister, 26: Raw liquid supply line, 27: Permeate liquid line, 28: Overflow liquid outlet line, 29: Backwash gas supply line, 31: Backwash gas line, 32: Purified gas discharge line, 33: Cleaning liquid Line, 34: Cleaning liquid extraction line,
35: Backwash liquid extraction line, 36: Transport pump.

Claims (1)

[Scope of Claims] 1. A method of filtering a liquid containing a suspended substance through at least one filtration membrane bundle formed by bundling a large number of hollow fiber-like porous polymer membranes to separate a filtrate; A filtration method for cleaning a filtration membrane by gas backwashing, characterized in that when backwashing the filtration membrane, an overflow amount of liquid is extracted in advance and then backwashing is performed. 2 Consists of a filtration liquid part having a filtrate outlet and a backwashing gas inlet, and a undiluted solution zone part having a filtrate undiluted solution inlet, a undiluted solution outlet and a backwashing gas outlet, and a hollow fiber-like porous polymer membrane. A filtration device that filters a liquid containing suspended substances by using at least one or more filtration membranes bundled together to separate a filtrate, and then cleans the filtration membranes by gas backwashing. A partition plate is provided to support the filtration membrane bundle and separate the filtrate band and the stock solution band, and an overflow liquid outlet is provided below the backwash gas outlet of the stock solution band. Features a filtration device.