JPH09138298A - Filter using hollow-fiber membrane and method for backwashing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency in backwashing by combining draining methods and liquid levels in backwashing when a hollow-fiber membrane equipped with hollow-fiber membrane modules in a container is backwashed with the air. SOLUTION: The pressurized air is quickly supplied to a filter tower body container, and a waste liquid from backwashing is drained for a short time. Moreover, the efficiency is improved in the drainage of granular impurities during backwashing by changing liquid levels when the lower air from a lower air intake valve 44 is backwashed to remove residual granular impurities in parts inside the filter tower and interstices between modules by liquid level vibration and combining the high-pressure backwash with the upper air, the low-pressure air backwash with the lower air and the regulation of liquid levels.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filtration device using a hollow fiber membrane filter having a plurality of hollow fiber membrane modules in a container for filtering a stock solution, and a method for backwashing the same. The present invention relates to a filtration device having a high backwashing property of a membrane module and a backwashing method thereof.

[0002]

2. Description of the Related Art As a filtering device used for separating and removing particulate impurities existing in condensate and radioactive waste liquid in a nuclear power plant, conventionally, a filter aid such as powder ion exchange resin is precoated on an element. However, a precoat type filter that separates and removes particulate impurities from the filter aid precoat layer has been adopted, but in recent plants, hollow fiber membrane filters that do not use the filter aid have come to be adopted.

FIG. 2 shows a schematic structure of a hollow fiber membrane filter. The stock solution that needs to be filtered is the stock solution supply pipe 1.
1, a raw liquid inlet valve 12, a raw liquid filtration tower inlet pipe 13 is introduced into a filtration tower 1 and filtered by a hollow fiber membrane bundled in a hollow fiber membrane module 2, a treatment liquid filtration tower outlet pipe 14, a treatment liquid It is sent to the downstream system via the outlet valve 15 and the processing liquid outlet pipe 16. When the particulate impurities captured by the hollow fiber membrane reach a specified amount, the hollow fiber membrane is backwashed. In the backwashing of the hollow fiber membrane, the compressed air from the lower air supply pipe 41 is reduced to a required pressure by the lower air pressure reducing valve 42, and the compressed air is supplied from the lower air supply pipe 43, the lower air inlet valve 44, and the lower air inlet pipe 45. Low-pressure air backwashing for removing particulate impurities by vibrating the hollow fiber membrane with low-pressure air and compressed air from the air supply pipe 31 are filtered by the pre-air filter 6 to remove impurities, and the upper air pressure reducing valve 33 adjusts the pressure to the required pressure. After depressurization, the air further filtered by the air filter 7 and stored in the air storage tank 8 is supplied to the upper air supply pipe 37 and the upper air inlet valve 3
8. There is high-pressure air backwashing in which the filtration treatment liquid held in the filtration tower lid container 1b of the filtration tower 1 is pressure-fed by high-pressure air supplied from the upper air inlet pipe 39 to backwash the hollow fiber membrane from the inside to the outside. The particulate impurities trapped in the hollow fiber membrane are removed by one or a combination of both. Of the air used for this backwashing, the air supplied to the filtration tower barrel container 1a is supplied to the filtration tower barrel vent pipe 56, the filtration tower barrel vent valve 57, and the filtration tower vent pipe 59 in the filtration tower lid container 1b. The supplied air is supplied to the filter tower upper vent pipe 61 and the filter tower upper vent valve 6
2, the water held in the backwash receiving tank 9 through the filtration tower vent pipe 59 and containing particulate impurities in the filtration tower body container 1a is stored in the filtration tower drain pipe 51 and the filtration tower drain valve 5;
2. It is discharged to the backwash receiving tank 9 via the drain pipe 53.

FIG. 3 shows the structure of a hollow fiber membrane filter column. The filtration tower includes a filtration tower body container 1a and a filtration tower lid container 1b.
And the tube plate 3 sandwiched between them and the air dispersion plate 4 for backwashing
The hollow fiber membrane module 2 is composed of each nozzle.
Are suspended on the tube sheet 3.

FIG. 4 shows a general structure of a hollow fiber membrane module, particularly a multistage module. Hollow fiber membrane module 2
The upper and lower sides of the hollow fiber membrane 72 are placed in the outer cylinder 70 by the bonding agent 71.
A, 71B, and ones joined with the bonding agents 71C, 71D are stacked, and an opening 75 is provided in the outer cylinder 70 for introducing backwash air, exhausting air, and draining backwash water in the module.
It has A, 75B, 75C, and 75D. In addition, an air groove 76 for introducing the backwash air from the skirt 73 into the module is formed in the lower bonding agent 71D of the lower module,
It has an air communication pipe 77 for introducing air into the upper module. In the backwashing with the lower air of the filtration tower, the filtration tower shell container 1a is filled with water, and the low-pressure air supplied from the lower air inlet pipe 45 to the filtration tower shell container 1a is dispersed by the air dispersion plate 4 to each hollow fiber membrane. Collected in the lower part of the module 2, part of which is guided from the skirt portion 73 of the lower part of the module to the lower module through the air groove 76, to the upper module through the air communication pipe 77, and partly through the outer cylinder openings 75B and 75D into the module. Then, the hollow fiber membrane is vibrated to separate the particulate impurities captured by the hollow fiber membrane from the hollow fiber membrane. The separated particulate impurities together with the water contained in the filtration tower body container 1a have openings 75B,
It is guided to the outside of the module from 75D and discharged from the filtration tower shell container 1a to the backwash receiving tank 9 through the filtration tower drain valve 52.

In this case, especially in a multi-stage hollow fiber membrane module, since it is difficult to uniformly disperse air into the module, there is a concern that the backwashing effect may be different between the upper module and the lower module.

In order to solve this problem, Japanese Patent Laid-Open No. 62-2627
Japanese Unexamined Patent Publication (Kokai) No. 10 discloses a method of detecting the water level of backwash water, setting the liquid surface of the backwash water at the portion where the most particulate impurities remain, and removing the remaining particulate impurities. According to this method, it is possible to solve the problem that the backwash effect differs between the upper module and the lower module.

[0008]

Even if the backwashing is performed as in the above-mentioned prior art, since the drainage (drain) of the water contained in the filtration column body container 1a is discharged by gravity transfer, the hollow fiber membrane is once removed. There was a concern that particulate impurities separated from the module would settle and remain in the filtration tower and module. That is,
Particulate impurities in the drain effluent settle and are deposited on internal parts of the tower, such as the upper part of the air dispersion plate 4, or as a module bonding agent
There is a concern that they may remain in the gaps between B and 71D, the openings 75B and 75D, and the hollow fiber membrane 72. Such residual impurities are reattached to the hollow fiber membrane immediately after starting the normal filtration operation, so that the effect of backwashing is significantly reduced.

An object of the present invention is to extend the life of the hollow fiber membrane module by suppressing the residual of the fine particle impurities after such backwashing.

[0010]

To achieve the above object, the backwash water is drained rapidly at the time of backwashing to drain the particulate impurities. The pressurized air supplied to the filtration tower body container 1a acts to press the held water liquid level by pressurizing the held water in the filtration tower body container 1a,
As a result, rapid draining is possible and the draining time is shortened, so that the particulate impurities can be discharged out of the filtration tower together with the retained water in a floating state before the particulate impurities spontaneously settle. Further, it is effective to wash the portion where particulate impurities are likely to remain simultaneously with the rapid discharge of the backwash water. It is also preferable to change the backwashing method of the upper and lower modules of the multistage hollow fiber membrane module 2.

Specifically, in FIG. 1, the compressed air is supplied from the compressed air / air storage tank 8 to the filtration tower body 1a through the compressed air inlet valve 47, and is rapidly drained by pressurizing air. The tube sheet on which the hollow fiber membrane module is suspended is a filter tower lid container 1
b and the filtration tower body container 1a have a watertight structure so that the filtrate does not move to each other. That is, the filtration tower lid container 1b
The filtrate inside does not reach the filtration column body container 1a unless it passes through the hollow fiber membrane from the inside of the hollow fiber membrane module. In the conventional backwashing, backwashing is performed by sending pressurized air only into the inside of the filtration tower lid container 1b and by forcibly feeding the filtrate in the filtration tower lid container 1b into the hollow fiber membrane module. It was In the present invention, the pressurized air is sent to the inside of the filtration tower lid container 1b, and the pressurized air is also sent to the filtration tower body container 1a, whereby the backwash water drainage liquid inside the filtration tower body container 1a is rapidly discharged. To discharge. It is effective that the pipe for sending the pressurized air to the filtration tower body container 1a is installed as close as possible to the tube plate so that the drainage liquid is pushed out from above the liquid level of the drainage liquid inside the filtration tower barrel container 1a. Is. Most preferably, it is installed directly below the tube sheet. Further, although the filtration tower body container is often cylindrical, in that case, it is preferable that a plurality of pipes for feeding air are evenly provided in the circumferential portion of the filtration tower body container.

Further, bubbling by injecting low-pressure air from the lower part of the filtration column body container (making air bubbles in the filtrate by injecting air to vibrate the hollow fiber membrane module)
By carrying out simultaneously, effective backwashing can be carried out. Further, at this time, by intermittently supplying the pressurized air to the filtration column body container 1a, while particularly backwashing the hollow fiber membrane module, in particular, where particulate impurities are likely to adhere, In addition, floating impurities can be rapidly discharged without settling.

Liquid is obtained by changing the liquid level of the filtration tower body container 1a and performing low pressure air backwashing with lower air using the portion of the hollow fiber membrane module 2 and the filtration tower 1 where particulate impurities are likely to remain as the liquid surface. The surface vibration acts to remove the residual particulate impurities in the gap.

In the multistage hollow fiber membrane module 2, it is difficult to uniformly separate air into the upper module by backwashing with low pressure air. The backwashing efficiency of the filtration tower can be improved by improving the backwashing property of the upper module by performing the washing.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.

One or more hollow fiber membrane modules 2 shown in FIG. 4 are suspended on a tube plate 3 sandwiched between a filtration tower shell container 1a and a filtration tower lid container 1b. The stock solution is passed through the stock solution inlet valve 12 and the stock solution filtration tower inlet pipe 13 to form the filtration tower body container 1
It is guided to the inside of a and filtered by the hollow fiber membrane in the hollow fiber membrane module 2. The treatment liquid is collected in the filtration tower lid container 1b and sent to the downstream system through the treatment liquid filtration tower outlet pipe 14, the treatment liquid outlet valve 15, and the treatment liquid outlet pipe 16. The backwashing of the hollow fiber membrane is performed by low pressure air backwashing in which the hollow fiber membrane 72 is vibrated by the low pressure air supplied from the lower air inlet valve 44 and the lower air inlet pipe 45, and the upper air inlet valve 38 and the upper air inlet pipe 39.
The high pressure air supplied from the hollow fiber membrane is used for backflow from the inside to the outside to perform backwashing, and the air used for backwashing is the filtration tower barrel vent pipe 56 and the filtration tower barrel vent valve 58.
The water stored in the container is discharged to the backwash receiving tank 9 via
It is discharged to the backwash receiving tank 9 through the filter tower drain pipe 51 and the filter tower drain valve 52.

Here, what is different from the conventional one is that a pressurized air supply system from an air storage tank 8 which is a compressed air supply facility is installed in the filtration tower body container 1a.

The pressurized air supply is performed by a pressurized air supply pipe 46 and a pressurized air inlet branching from the upper air supply pipe 37 to the high pressure air stored in the air storage tank 8 for supplying air from the upper side for high pressure air backwashing. It is supplied to the filtration tower shell container 1 a via a valve 47 and a pressurized air inlet pipe 48. At this time, the pressurized air inlet valve 47 and / or the filtration tower drain valve 52, or any one of them, has a valve specification that allows a rapid opening operation in order to rapidly pressurize the water contained in the filtration tower.

In the backwashing of the filtration tower, low-pressure air supplied from the lower air inlet valve 44 and the lower air inlet pipe 45 at the lower part of the filter tower shell 1a is collected in each hollow fiber membrane module 2 by the air dispersion plate 4, and the hollow fiber The bubbles on the outside of the membrane vibrate the membrane to remove trapped particulate impurities on the outer surface of the membrane. Immediately after low-pressure air backwashing with the lower air, the pressurized air inlet valve 47 and the filter tower drain valve 52 are rapidly opened to suspend the water contained in the filter tower from the upper part of the filter tower in a floating state before the particulate impurities settle. Drain with pressurized air.

Here, the pressurized air inlet valve 47 is operated normally to open the pressurized air inlet valve 47, and then the filtration tower drain valve 52 is used.
The same effect can be obtained by the operation of rapidly opening the valve or the operation of normally opening the filter tower drain valve 52 and rapidly opening the pressurized air inlet valve 47.

The present invention has the effect of improving the dischargeability of impurities by rapidly discharging the water contained in the filtration column body container 1a containing the particulate impurities after backwashing the lower portion of the hollow fiber membrane module. .

5 and 6 show an embodiment in which the hollow fiber membrane module 2 is backwashed by low-pressure air backwashing by changing the liquid level and vibrating the liquid surface. First, backwashing is performed by vibrating the membrane from the lower air when the filtration tower body container 1a is full of water, and then water is drained to, for example, the vicinity of the opening 75B of the module shown in FIG. At this liquid level, the lower air inlet valve 44 is opened to supply low-pressure air to the filtration tower body 1a, and the particulate impurities remaining in the gap between the module bonding agent 71B, the hollow fiber membrane 72, and the opening 75B are removed by vibration of the liquid surface. To do. Subsequently, water is drained to the vicinity of the opening 75D of the module shown in FIG. 6, and low pressure air is similarly supplied to remove the particulate impurities remaining in the gap between the module bonding agent 71D, the hollow fiber membrane 72, and the opening 75D. Remove by vibration. If necessary, further air dispersion plate 4
The backwashing effect can be improved by draining the water to the vicinity and removing the particulate impurities accumulated in the upper portion of the air dispersion plate 4 by the liquid level vibration caused by the low pressure air.

FIG. 7 shows an embodiment for improving the backwash efficiency of the hollow fiber membrane module 2. In the module structure shown in FIG. 4, when air is backwashed with low-pressure air, the air collected in the skirt 73 in the lower module passes through the air grooves 76 and is collected in the lower module, but the upper module communicates with the lower module. Since the air is introduced through the pipe 77, the air is not evenly dispersed in terms of the dispersibility of the air, and there is a concern that particulate impurities may remain particularly in the hollow fiber membrane binding portion of the bonding agent 71B. Therefore, in the upper module, water is drained to the middle portion of the hollow fiber membrane module 2 shown in FIG. 7, and the hollow fiber membrane 72 is backwashed from the inside to the outside by high pressure air in the upper air. It is a thing. In other words, during high-pressure air backwashing in which the upper air inlet valve 38 is opened and the water held in the lid container 1b is backflowed from the inside of the membrane to the outside by air pressure, the lower module is hollow because it is in the water held in the filtration column body container 1a. Since the resistance of the outer surface of the thread film 72 is large, the backflow water mainly flows back through the upper module portion open to the atmosphere, which improves the backwash efficiency of the upper module.

[0024]

According to the present invention, a waste liquid containing particulate impurities after backwashing a hollow fiber membrane module is rapidly discharged, and
The backwashing efficiency can be improved by changing the liquid level of the filtration tower and causing the gap to vibrate on the liquid surface by air so as to improve the discharge property of the particulate impurities.

Further, by backwashing the upper stage module of the hollow fiber membrane module with high pressure air by the upper air, the backwashability of the upper stage module can be improved and the backwashing efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a system diagram in which a pressurized air system of a hollow fiber membrane filter is installed.

FIG. 2 is a conventional system diagram of a hollow fiber membrane filter.

FIG. 3 is a structural diagram of a hollow fiber membrane filter.

FIG. 4 is a structural diagram of a hollow fiber membrane module.

FIG. 5 is a structural diagram 1 showing the liquid level of a hollow fiber membrane filter during backwashing.

FIG. 6 is a structural diagram 2 showing the liquid level of the hollow fiber membrane filter during backwashing.

FIG. 7 is a structural diagram 3 showing the liquid level of a hollow fiber membrane filter during backwashing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Filtration tower, 1a ... Filtration tower body container, 1b ... Filtration tower lid container, 2 ... Hollow fiber membrane module, 3 ... Tube plate, 4 ... Air dispersion plate, 6 ... Pre-air filter, 7 ... Air filter , 8 ... Air storage tank, 9 ... Backwash receiving tank, 11 ... Stock solution supply pipe, 12 ... Stock solution inlet valve, 13 ... Stock solution filtration tower inlet tube, 14 ... Processing solution filtration tower outlet tube, 15 ... Processing solution outlet valve, 16 ... Processing liquid outlet pipe, 2
1 ... Make-up water supply pipe, 22 ... Make-up water inlet valve, 23 ... Make-up water inlet pipe, 31 ... Air supply pipe, 32, 34, 36, 37 ...
Upper air supply pipe, 33 ... Upper air pressure reducing valve, 38 ... Upper air inlet valve, 39 ... Upper air inlet pipe, 41, 43 ... Lower air supply pipe, 42 ... Lower air reducing valve, 44 ... Lower air inlet valve, 45 ... Lower air inlet pipe, 46 ... Pressurized air supply pipe, 4
7 ... Pressurized air inlet valve, 48 ... Pressurized air inlet tube, 51 ... Filtration tower drain tube, 52 ... Filtration tower drain valve, 53 ... Drain tube, 56, 58 ... Filtration tower barrel vent tube, 57 ... Filtration tower barrel Vent valve, 59 ... Filtration tower vent pipe, 61 ... Filtration tower upper vent pipe, 62 ... Filtration tower upper vent valve, 70 ... Outer cylinder, 71
A, 71B, 71C, 71D ... Bonding agent, 72 ... Hollow fiber membrane,
73 ... Skirt part, 75A, 75B, 75C, 75D ... Opening, 76 ... Air groove, 77 ... Communication pipe.

Front Page Continuation (72) Inventor Masato Kobayashi 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory

Claims (5)

[Claims] 1. A container body having a stock solution inlet and a processing solution outlet, and one or more hollow fiber membrane modules suspended in the container, and the container is separated into two chambers so that water does not communicate with each other. A filtration device equipped with a tube plate having a function, which allows the undiluted solution to pass through from the outside of the hollow fiber membrane module and captures particulate impurities on the outer surface of the hollow fiber membrane in the hollow fiber membrane module. A filtration device, characterized in that a tube for supplying pressurized air is provided near the tube sheet on the side where the membrane module is suspended. 2. A container body having a stock solution inlet and a processing solution outlet, and one or more hollow fiber membrane modules suspended in the container, and the container is separated into two chambers so that water does not communicate with each other. A reverse filter that is equipped with a tube plate having a function, passes the stock solution from outside the hollow fiber membrane module, and traps particulate impurities on the outer surface of the hollow fiber membrane inside the hollow fiber membrane module to remove the trapped impurities. In the washing method, pressurized air is injected from above the liquid surface of the liquid in the container to accelerate discharge of the liquid in the container, thereby backwashing the filtering device. 3. The method of backwashing a filtration device according to claim 2, wherein the pressurized air is intermittently injected. 4. A container body having a stock solution inlet and a processing solution outlet, and one or more hollow fiber membrane modules suspended in the container, and the container is separated into two chambers so that water does not communicate with each other. A reverse filter that is equipped with a tube plate having a function, passes the stock solution from outside the hollow fiber membrane module, and traps particulate impurities on the outer surface of the hollow fiber membrane inside the hollow fiber membrane module to remove the trapped impurities. In the washing method, pressurized air is injected from above the liquid surface of the liquid in the container to accelerate the discharge of the liquid in the container, and at the same time, air is injected into the liquid to bubble the liquid. The method of backwashing the filtration device. 5. The operation according to claim 4, wherein pressurized air is injected also into the side of the container on which the hollow fiber membrane module is not suspended so that the liquid in the container flows backward from the inside of the hollow fiber membrane to the outside. A method of backwashing a filtration device, characterized in that