JPH0437729B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a filtration device used, for example, in nuclear power generation equipment, and in particular to a hollow fiber membrane filtration device.

[Technical background of the invention and its problems] In boiling water nuclear power plants, insoluble solids (hereinafter referred to as crud) contained in condensate and radioactive liquid waste (hereinafter referred to as waste liquid)
A filtration device is used to remove the

By the way, conventionally used filtration devices include, for example, filtration devices using a precoated filter such as powdered ion exchange resin, or filtration devices using filter paper, filter cloth, etc.; This method was not necessarily satisfactory in terms of generation of secondary waste, filtration efficiency, and concentration rate of substances to be separated by filtration.

In recent years, a hollow fiber membrane filtration device using a hollow fiber membrane filter has been used to remove crud from waste liquid.

In such a hollow fiber membrane filtration device, waste liquid flows into the waste liquid supply pipe of the closed container, is filtered by passing through the hollow fiber membrane filter, and is configured to flow out from the treated liquid discharge pipe. At this time, the crud in the waste liquid adheres to the surface of the hollow fiber membrane filter, so as the waste liquid continues to be processed, the differential pressure before and after the filtration device (filtration differential pressure) increases, and the filtration function of the hollow fiber membrane filtration device decreases. do. Therefore, it is necessary to perform backwashing to remove crud adhering to the surface of the hollow fiber membrane filter.

Conventional backwashing involves introducing pressurized gas into the treated water outlet or the treated water side of a sealed container, and by causing the treated water to flow back with this pressurized gas, the hollow fiber membrane filter is further pressurized. This is done by passing gas. That is, the cladding is separated from the surface of the hollow fiber membrane filter by the backflowing treated water or pressurized gas and diffused into the waste liquid in the closed container, and is then discharged from the concentrated sludge discharge pipe. After discharging this waste liquid, the treated water is flowed into the closed container and filtered again. However, in the conventional backwashing method described above, the waste liquid in the closed container must be discharged every time backwashing is completed, and the amount of waste liquid discharged is large. Moreover, there was a problem that the concentration of clad in the waste liquid was low.

Therefore, as a method to reduce the amount of waste liquid discharged from the filtration device and increase the concentration of crud in the waste liquid, after performing a certain amount of filtration treatment, pressurized gas is supplied from the pressurized gas supply pipe to the closed container. After supplying the liquid to the liquid side and causing the processing liquid to flow back with pressurized gas,
A possible filtration treatment method is to repeat the procedure of performing the filtration treatment again a predetermined number of times, and then discharge the waste liquid from the concentrated sludge discharge pipe.

However, when this filtration treatment method is applied to a conventional hollow fiber membrane filtration device, there is variation in the amount of treatment liquid that flows backwards with pressurized gas and removes crud on the surface of the hollow fiber membrane filter, making it difficult to remove enough crud. The problem is that the effects cannot be expected. To explain this in more detail, when introducing pressurized gas from a pressurized gas supply pipe into a sealed container, all pipes other than the pressurized gas supply pipe connected to the sealed container are closed, and the pressurized gas is Gas is supplied in an amount until the pressure inside the sealed container becomes the same as the pressure of the pressurized gas. This is the amount by which the volume is reduced by being pressurized to . In the normal filtration treatment method, air is mixed into the waste liquid, and the amount of air that flows into the closed container of the filtration device is not large, and it is also unfavorable from the viewpoint of the performance of the pump and the like. Furthermore, depending on the material of the hollow fiber membrane, gases such as air may pass through it, resulting in it flowing out together with the processing liquid. Therefore, even if pressurized gas is supplied to a closed container, the amount of processing liquid that flows back due to the pressurized gas is different each time, and since the amount is small, the crud removal effect due to backflow is not sufficient. The problem was that I couldn't get my hopes up.

[Object of the invention] The present invention has been made in view of the above circumstances, and
The objective is to provide a hollow fiber membrane filtration device that can be operated efficiently by reducing the amount of waste liquid discharged from the filtration device and reducing the number of hollow fiber membrane filter replacements.

[Summary of the Invention] In order to achieve the above object, the present invention provides a hollow fiber membrane filter for filtering waste liquid, a closed container main body housing the hollow fiber membrane filter, and a waste liquid flowing into the closed container main body. a supply pipe, a processing liquid discharge pipe through which the processing liquid filtered in the sealed container body flows out, a gas supply pipe which supplies pressurized gas to the hollow fiber membrane filter, and a waste liquid concentrated in the sealed container main body. A concentrated flask discharge pipe for discharging and a gas storage part for pressure adjustment provided on the waste liquid supply side, and the amount of pressurized gas supplied from the gas supply pipe into the closed container is supplied to the gas storage part. This invention relates to a hollow fiber membrane filtration device that can be set to an arbitrary amount depending on the amount of gas to be stored.

[Embodiments of the invention] An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of a hollow fiber membrane filtration device that is an embodiment of the present invention. Hollow fiber membrane filtration device 1
is a divisible airtight container body 2 having a hollow cylindrical shape.
The closed container main body 2 is connected to a separate tank 4 having a gas storage section 3 for pressure adjustment at its lower side. Further, the hollow fiber membrane filter 5 is supported by a support plate 6 fixed to the upper part of the closed container main body 2.

Further, a waste liquid supply pipe 7 having a valve 12 is provided on the lower side surface of the closed container main body 2, and a processing liquid discharge pipe 8 having a valve 13 is provided in the upper part of the closed container main body 2. The processing liquid discharge pipe 8 is provided with a vent pipe 10 having a valve 15 and a pressurized gas supply pipe 11 having a valve 16. Furthermore, the airtight container body 2
A concentrated sludge discharge pipe 9 with a valve 14 is provided at the bottom of the
is installed.

Next, the filtration method of the hollow fiber membrane filtration device 1 will be explained.

Now, valves 12, 13 are open, valves 14, 15, 1
6 is closed, the waste liquid flows into the closed container main body 2 from the waste liquid supply pipe 7 at a constant pressure, passes through the hollow fiber membrane filter 5, and flows out from the processing liquid discharge pipe 8. At this time, the cladding components in the waste liquid adhere to the surface of the hollow fiber membrane filter 5. As crud accumulates on the surface of the hollow fiber membrane filter 5, the filtration differential pressure increases, and when it reaches a predetermined pressure, the water flow is stopped and the filters installed in the waste liquid supply pipe 7 and the treated liquid discharge pipe 8 are Close valves 12 and 13.

Next, the valve provided in the gas supply pipe 11 is opened, and pressurized gas is supplied from the gas supply pipe 11 for a certain period of time until the pressure inside the closed container main body 2 becomes the same as the pressure of the supplied gas. After supplying gas, valve 16
Close. The pressurized gas supplied from the gas supply pipe 11 causes the processing liquid to flow back from the inside of the hollow fiber membrane filter 5 to the surface thereof, thereby removing crud adhering to the surface of the hollow fiber membrane filter 5.

In this case, the amount of processing liquid to be caused to flow back is determined by the amount of gas (for example, air) stored in the gas storage section 3. That is, the gas stored in the gas storage section 3 is a pressurized gas that is supplied to the gas supply pipe 1.
As the pressure inside the closed container 2 increases, the volume of the processing liquid is reduced, and the processing liquid flows back by the reduced volume. Therefore, by adjusting the amount of gas stored in advance, the amount of processing liquid flowing back can be adjusted. After removing the crud by backflowing the processing liquid, open the valve 15 installed in the vent pipe 10,
By releasing the pressure inside the closed container body 2, the gas in the gas storage section 3 returns to its original volume.

Then, the valve 15 installed on the vent pipe 10 is closed, and the valves 12 and 13 installed on the waste liquid supply pipe 7 and the treated liquid discharge pipe 8 are opened again to allow water to flow. At this time, valves 14, 15, and 16 are closed.

After repeating the above water flow and removal of crud by supplying pressurized gas several times, the concentrated sludge discharge pipe 9
The valve 14 installed in the tank is opened and the concentrated sludge is discharged. It is also possible to carry out scrubbing by supplying pressurized gas before this discharge to further increase the crud removal efficiency.

According to this embodiment, since the waste liquid treatment is performed as described above, it is possible to adjust the amount of treated liquid flowing back depending on the amount of gas stored in the gas storage section 3. Therefore, the amount of processing liquid flowing back can be set in advance according to the processing capacity of the hollow fiber membrane filtration device 1, the filtration area of the hollow fiber membrane filter 5, and the properties of the waste liquid.

In the case of conventional hollow fiber membrane filtration equipment that does not have a gas storage section, the amount of treated liquid that flows back due to pressurized gas is the volume reduced due to pressurization of air bubbles introduced into the filtration equipment as waste liquid. The amount was imprecise and small.

Therefore, according to this embodiment, when compared with the conventional filtration device, the concentration of crud, etc. is reduced by approximately 30% due to the crud removal effect by closing the valves before and after the filtration device and supplying pressurized gas to the body of the closed container. This has improved to about 20% (previously about 10%).

Furthermore, the effect of removing crud slows down the progress of clogging of the hollow fiber membrane filter, and the usage period of the hollow fiber membrane filter is approximately 1.5 times longer than that of conventional filtration equipment.
It has doubled. Concentrated sludge discharged from the filtration device as the concentration rate of the clad increases (backwash water amount)
The load on the waste liquid treatment device installed downstream of the hollow fiber membrane filtration device of this embodiment can be reduced.

Further, in this embodiment, a vent pipe 10 is provided in order to release the pressure increased due to the supply of pressurized gas, but this vent pipe 10 can be omitted. This is because when water flow is restarted, the valve 12 of the processing liquid discharge pipe 7 is opened, which allows gas to escape and the pressure to drop.

FIG. 2 is a schematic cross-sectional view of a second embodiment of the invention. Components that are the same as those in the first embodiment are given the same reference numerals, and detailed explanation thereof will be omitted.

The hollow fiber membrane filtration device 1A shown in FIG. 2 has a structure in which a tank 4A provided with a gas storage section 3A is installed in a closed container main body 2A of the hollow fiber membrane filtration device 1A. Note that, as long as this gas storage section 3A is connected to the closed container main body 2A, the crud removal effect is the same as in the previous embodiment, regardless of where it is provided within the closed container main body 2A. Furthermore, when the gas storage section 3A is installed inside the closed container 2A, the gas storage section 3A itself does not function as a pressure vessel, so the wall surface can be made thin, and the structure becomes simple. It also has the advantage of requiring less installation space.

FIG. 3 is a schematic cross-sectional view of a third embodiment of the invention. Components that are the same as those in the first embodiment are given the same reference numerals, and detailed explanation thereof will be omitted. The hollow fiber membrane filtration device 1B shown in FIG. Since it is installed,
This gas storage section 3B will be installed apart from the closed container main body 2B. Therefore, by attaching only the tank 4B to the existing hollow fiber membrane filtration device, the same crust concentration effect as in the first embodiment can be achieved.

Note that the gas storage section is not only installed in the waste liquid supply pipe as in this embodiment, but also installed in a pipe connected to the closed container main body, such as a concentrated sludge discharge pipe, for example.
Alternatively, it may be installed in a drain pipe, vent pipe, etc. that branches from those pipes.

[Effects of the Invention] As explained above, according to the hollow fiber membrane filtration device of the present invention, gas is stored inside the sealed container body housing the hollow fiber membrane filter or in a separate tank communicating with the sealed container body. In a waste liquid treatment method in which crud is removed by supplying pressurized gas to the closed container main body to the treatment liquid side of the hollow fiber membrane filter and causing the treatment liquid to flow back by providing a storage part, the amount of treatment liquid that flows back. can be set arbitrarily. Therefore, the effect of removing crud caused by backflow of the treated liquid is improved, the amount of waste liquid discharged from the hollow fiber membrane filtration device is reduced, and the hollow fiber membrane filter is less likely to be clogged. Reduces the need to replace filters,
It has an excellent effect.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of one embodiment of the present invention, and FIG.
The figure is a schematic sectional view of a second embodiment of the invention, and FIG. 3 is a schematic sectional view of a third embodiment of the invention. 1, 1A, 1B...Hollow fiber membrane processing device, 2, 2
A, 2B... Airtight container body, 3, 3A, 3B...
Gas storage unit for pressure adjustment, 4, 4A, 4B...Tank, 5...Hollow fiber membrane filter, 6...Support plate,
7... Waste liquid supply pipe, 8... Processing liquid discharge pipe, 9...
Concentrated sludge discharge pipe, 10... Vent pipe, 11...
...Gas supply pipe.

Claims (1)

[Scope of Claims] 1. A hollow fiber membrane filter that filters waste liquid, a closed container body that accommodates the hollow fiber membrane filter, a waste liquid supply pipe that flows the waste liquid into the closed container body, and a A processing liquid discharge pipe for discharging the filtered processing liquid, a gas supply pipe for supplying pressurized gas to the hollow fiber membrane filter, a concentrated sludge discharge pipe for discharging the waste liquid concentrated in the sealed container main body, and the waste liquid supply. and a gas storage part for pressure adjustment provided on the side, and the amount of pressurized gas supplied from the gas supply pipe into the sealed container can be set to an arbitrary amount depending on the amount of gas stored in the gas storage part. A hollow fiber membrane filtration device characterized in that the amount can be set. 2. The hollow fiber membrane filtration device according to claim 1, wherein the gas storage section is formed within the closed container main body. 3. The hollow fiber membrane filtration device according to claim 1, wherein the gas storage section is formed of a tank separate from the closed container main body.