JPH0611386B2 - Backwashing method for hollow fiber membrane filters - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention uses a hollow fiber membrane to backwash the hollow fiber membrane when a radioactive waste liquid generated in a nuclear power plant or condensate in a nuclear reactor is passed. It is about the method.

[Conventional technology and its problems]

Conventionally, a precoat type filter has been used to remove suspended substances from radioactive waste liquid or condensate.
When this precoat type filter is used, the filter is clogged and the differential pressure is a certain value or more (for example, 1.
Backwashing is carried out when it reaches 5 to ² kg / cm ² or more), but the precoat material itself is also mixed as secondary waste in the backwashing waste liquid in addition to the suspended substances captured by the filter. Therefore, the amount of waste increases, which is not preferable for waste management.

In order to solve such a problem, a method of using a hollow fiber membrane filter in which the amount of secondary waste generated is extremely small has been adopted. When using a hollow fiber membrane filter, when the suspended substance is passed on the outer surface of the hollow fiber membrane and the amount of suspended substance adhered increases and the differential pressure becomes a constant differential pressure, or a predetermined differential pressure rise When the temperature reaches a certain level, backwashing is performed, but it is necessary to suppress the progress of dirt on the film surface by this backwashing as much as possible.

That is, if the membrane surface is significantly soiled, the hollow fiber membrane itself cannot be regenerated and must be discarded, which is not preferable from the viewpoint of waste reduction and economical efficiency.

[Object of the Invention]

It is an object of the present invention to provide an effective backwashing method for extending the life of hollow fiber membranes.

[Structure of Invention]

The present invention is a method for backwashing a hollow fiber membrane as set forth in claims 1 and 2.

First, the method for backwashing the hollow fiber membrane of the present invention will be described with reference to FIG. In the hollow fiber membrane passing step (step 1), the liquid to be treated inlet valve 7 and the water outlet valve 4 are opened, the liquid to be treated is introduced from the liquid to be treated introducing pipe into the hollow fiber membrane filter, and The plurality of hollow fiber membrane bundles provided are passed from the outside to the inside of the hollow fibers, and the excess water is drawn from the upper end of the hollow fibers into the dome on the tube sheet 11, and then through the excess water outlet valve 4 to the filter. Drawn from.

When the suspension adheres to the outer wall of the hollow fiber membrane and the differential pressure becomes a constant value or the differential pressure increase degree becomes a specific value or more, the liquid to be treated inlet valve 7 and the liquid to be treated (super water) outlet valve 4 Is closed to stop the operation of the excess device (step 2).

Next, the main body vent valve 5 and the air scrubbing valve 9 are opened, air is introduced into the main body from the air scrubbing valve 9, and scrubbing is performed to promote separation of the suspension adhered to the outer wall of the hollow fiber membrane. (Step 3).

At the end of this step, the water level in the body barrel has dropped by the volume of the air introduced and remaining during the air scrubbing. Therefore, the air scrubbing valve 9 is closed and the water inlet valve 8 is opened. Introduce water from 8 and tube plate 11
(Step 4), then the main body vent valve 5 and the water inlet valve 8 are closed, and the pressurized air valve 2 and the dome drain valve 3 are opened to perform the dome drain above the dome drain port (step). 5).

Then, the dome drain valve 3 is closed, and the air in the upper body is pressurized to a predetermined pressure with pressurized air (step 6), and then the backwash discharge valve 10 at the lower part of the main body is opened, and the water in the upper body is used. The bumps of the hollow fiber membrane are bumped to remove the suspension adhering to the hollow fiber membrane (step 7), and then the pressurized air communication valve 6 is opened to introduce pressurized air into the main body cylinder to remove it. The liquid containing the suspended liquid is discharged (step 8).

Then, the pressurized air valve 2 and the pressurized air communication valve 6 are closed, the dome drain valve 3 is opened to release the pressure in the filter 13 (step 9), and then the main body vent valve 5 is opened and the backwash discharge valve 10 is opened.
Is closed and the water inlet valve 8 is opened to introduce water into the main body cylinder to perform liquid filling below the tube plate (step 10), and then the main body cylinder vent valve 5 is closed to perform liquid filling to the dome drain port (step 11). ).

Then, the water inlet valve 8 and the dome drain valve 3 are closed, the body barrel inlet valve 5 and the air scrubbing valve 9 are opened, and the air introduced from the air scrubbing valve again scrubs the hollow fiber membrane for a predetermined time to obtain the hollow fiber. After further promoting the separation of the suspension adhered to the membrane (step 12), the air scrubbing valve 9 is closed and the water inlet valve 8 is opened to perform liquid filling below the tube sheet (step 13). After finishing the water inlet valve 8,
After closing the main body vent valve 5 and opening the pressurized air valve 2 to pressurize the upper body (upper dome) to a predetermined pressure with pressurized air (step 14), open the backwash discharge valve 10 and open the upper part. The hollow fiber membrane is bumped with the water in the body (step 15), and then the pressurized air communication valve 6 is opened to introduce pressurized air into the body barrel to backwash the water containing the suspension in the body barrel. The liquid is discharged all at once through the liquid discharge valve (step 16). Then, the pressurized air valve 2 and the pressurized air communication valve 6 are closed, the dome drain valve 3 is opened to release the pressure in the filter (step 17), and then the dome drain valve 3 and the backwash discharge valve 10 are closed and vented. After the valve 1, the main body vent valve 5 and the water inlet valve 8 are opened and liquid is filled up to below the tube plate (step 18), the main body vent valve 5 is closed and the upper body is filled with liquid (step 19). After full water, the water inlet valve 8 and the vent valve 1 are closed and brought into a stopped state (step 20) to prepare for the next overstep (step 1).

In the present invention, after over-operation is stopped to backwash the hollow fiber membrane filter (step 2), air scrubbing of the hollow fiber membrane is immediately carried out (step 3), liquid filling under the tube sheet, dome drain, and After pressing the dome, bumps of the hollow fiber membrane are applied (step 7) to effectively remove the suspension adhering to the hollow fiber membrane, and then pressurized air is introduced into the main body. And then the liquid containing the suspension is discharged all at once (step 8),
Liquid fill up to the dome drain port on the upper body again (Process 10,
Performing step 11), scrubbing step (step 12), lower tube sheet draining step (step 13), dome pressurizing step (step 14), bump step (step 15), lower tube sheet discharging step (step 16) Then, the scrubbing step is prioritized over the bump step, and the scrubbing step and the bump step are repeated twice to completely remove the suspended matter from the hollow fiber membrane. In addition, steps 10 to 17
By incorporating a series of steps up to and including two or more series of steps, it is possible to efficiently prevent the hollow fiber membrane from being contaminated and to perform stable overoperation.

Further, in the present invention, the bump step (steps 7 and 15) is performed with the clean liquid that has passed through the hollow fiber membrane, which is more effective.

The reason why the liquid is not discharged below the tube sheet in steps 7 and 15 is that the hollow fiber membrane used in the present invention does not pass air. That is, the discharge pressure is below the bubble point.

Further, in the description of the drawings, the pressurized air chamber is provided inside the filter, but this portion can be provided outside.

〔The invention's effect〕

According to the present invention, when backwashing a hollow fiber membrane, the scrubbing step is prioritized over the bump step and is divided into scrubbing and bumps, and at least two steps are required.
Efficient backwashing can be performed by repeating the process.

[Brief description of drawings]

FIG. 1 is a process diagram for explaining the method of the present invention. 1 ... Vent valve, 2 ... Pressurized air valve, 3 ... Dome drain valve, 4 ... Overwater outlet valve, 5 ... Main body vent valve, 6
...... Pressurized air communication valve, 7 ...... Processed liquid inlet valve, 8 ...... Water inlet valve, 9 ...... Air scrubbing valve, 10 ...... Backwash discharge valve

Claims (2)

[Claims] 1. A method for passing a suspension contained in radioactive waste liquid or condensate by passing the whole amount of the radioactive waste liquid or condensate from the outside to the inside of the hollow fiber membrane, which comprises the following (A):
A method of backwashing a hollow fiber membrane, which comprises sequentially performing the steps from (R) to (R). (A) In the step (step 1) of supplying radioactive waste liquid or condensate to the hollow fiber membrane filter 12 and passing it, the pressure is stopped after the differential pressure reaches a predetermined pressure (step 2), and then the main body vent Opening the valve (5) and the air scrubbing valve (9) to introduce air from the air scrubbing valve (9) and performing air scrubbing for a predetermined time (step 3) (B) Close the air scrubbing valve (9) Inlet valve (8)
To open water and introduce water to fill the bottom of the tube plate (step 4) (C) Close the main body vent valve (5) and water inlet valve (8),
Opening the pressurized air valve (2) and dome drain valve (3) to perform dome drain (Step 5) (D) Closing the dome drain valve (3) and applying pressurized air to a predetermined pressure (Step 6) (E) Step of opening the backwash discharge valve (10) and bumping with water in the upper cylinder (Step 7) (F) Then, opening the pressurized air communication valve 6 to remove the liquid in the main cylinder Discharging process (Process 8) (G) Close the pressurized air valve (2) and pressurized air communication valve (6),
Step of opening the dome drain valve (3) to release the pressure in the filter (13) (Step 9) (H) Open the main body vent valve (5), close the backwash discharge valve (10), and close the water inlet valve ( 8) Opening to fill the bottom of the tube sheet with liquid (step 10) (I) Closing the main body vent valve (5) and filling with liquid to the dome drain port (step 11) (J) Water inlet valve 8 Closing the dome drain valve 3 and opening the main body vent valve 5 and the air scrubbing valve 9 to introduce air from the air scrubbing valve 9 to perform air scrubbing for a predetermined time (step 12) (K) close the air scrubbing valve 9 , The step of opening the water inlet valve 8 to fill the bottom of the tube sheet (step 13) (L) The water inlet valve (8) and the main body vent valve 5 are closed, and the pressurized air valve (2) is opened. Step of pressurizing the dome to a predetermined pressure with compressed air (step 14) (M) Backwash discharge valve (10 Open the chamber and perform bumping with water in the upper cylinder (step 15) (N), then open the pressurized air communication valve (6) and discharge the liquid in the body cylinder (step 16) (O) Close the compressed air valve (2) and the pressurized air communication valve (6),
Opening the dome drain valve (3) to release the pressure in the filter (step 17) (P) Dome drain (3), backwash discharge valve (10) are closed, vent valve (1), main body vent valve Step (5) and the water inlet valve (8) are opened to perform liquid filling up to the bottom of the tube plate (Step 1
8) (Q) A step of closing the main body vent valve 5 and filling the upper body with liquid (step 19) (R) A step of closing the water inlet valve (8) and the vent valve (1) after the water is full (stopping the state) Step 20) 2. The method for backwashing hollow fiber membranes according to claim 1, wherein between step 9 and step 18, a set of a series of steps from intermediate step 10 to step 17 is set, 2 steps
A method for backwashing hollow fiber membranes, characterized in that at least one set is provided.