JPS62163708A - Method for backwashing hollow yarn filter - Google Patents

Abstract

PURPOSE:To prolong the life of a hollow yarn membrane by incorporating a scrubbing stage in succession to backwashing by compressed air, and effectively removing the suspended matter deposited on the hollow yarn membrane and which is difficult to release. CONSTITUTION:When the hollow yarn membrane filter for filtering radio-active waste liq. or condensate is backwashed, a dome drain valve 3 and a compressed air valve 2 are opened to discharge the liq. in the dome. Then only the valve 3 is closed, a backwashing discharge valve 9 is opened, and the liq. is discharged at a stretch to the height of a tube plate 11. The valve 9 is then closed, water is supplied and filled to a height under the tube plate by opening the valve 3, a tube plate vent valve 5, and a water inlet valve 7, the valve 5 is closed to fill the water to a dome drain port, the valves 3 and 7 are closed and an air scrubbing valve 8 and the valves 5 and 2 are opened to carry out air scrubbing, the valve 2 is closed, and air scrubbing is continued. The valve 5 is closed and the valve 9 is opened to discharge the liq. contg. suspended matter, and the valve 8 is closed and the valve 3 is opened to resume the filtration.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to the use of hollow fiber membranes when radioactive waste liquid generated in nuclear power plants or the like or condensate in Fi nuclear reactors is passed through the door using hollow fiber membranes. The present invention relates to a backwashing method.

[Conventional technology and its problems]

Conventionally, pre-coat type filters have been used to remove suspended solids from radioactive waste liquid or condensate.

When using this pre-coated type filter, the filter may become clogged and the differential pressure may exceed a certain value (for example, 1
．． Backwashing is performed when the temperature reaches 5-2 (1774 or higher), but in addition to the suspended solids captured by the filter, the precoat material itself is mixed in as secondary waste in the backwash waste liquid. , the amount of waste increased, and the amount of waste was not desirable from a physical standpoint.

In order to solve these problems, a method of filtration using a hollow fiber membrane filter, which generates an extremely small amount of secondary waste, has been adopted.

When filtration is performed using a hollow fiber membrane filter, when suspended solids are filtered on the outer surface of the hollow fiber membrane and the amount of suspended solids attached increases and the differential pressure becomes a constant differential pressure, or when the differential pressure rises to a specified level. When this happens, backwashing is performed, but it is necessary to suppress the progress of fouling on the membrane surface as much as possible through this backwashing.

That is, if the membrane surface is significantly contaminated, the hollow fiber membrane itself cannot be regenerated and must be disposed of, which is undesirable from the viewpoint of waste reduction and economic efficiency.

[Purpose of the invention]

An object of the present invention is to provide an effective backwashing method in order to extend the life of hollow fiber membranes.

[Structure of the invention]

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

First, a conventional method for backwashing a hollow fiber filtration membrane will be explained based on FIG. Conventionally, in the hollow fiber membrane filtration step (step 1), the treated liquid population valve 6 and the treated liquid outlet valve are opened, the treated water is introduced from the treated liquid introduction pipe into the hollow fiber membrane filter, and the treated water is introduced into the filter. The filtered water is filtered from the outside to the inside of the hollow fibers of the provided plurality of hollow fiber membrane bundles, and the filtered water is drawn out from the upper end of the hollow fibers into the dome on the tube plate 13, and then exits the filter through the treated liquid outlet valve. be drawn out. If suspended matter adheres to the outer wall of the hollow fiber membrane and the differential pressure reaches a certain value or the rate of increase in differential pressure exceeds a certain value, close the treated liquid population valve and the treated liquid (filtrate water) outlet valve. and stop the operation of the filtration device (Step 2). Next, install the dome drain valve (3
) and the pressurized air valve (2) to drain the liquid in the dome to the height of the dome drain pipe (step 3), then after closing only the dome drain valve (step 4), open the backwash discharge valve 9,
The hollow fiber membrane is backwashed by draining the liquid in the dome all at once to the height of the tube sheet (step 5), then the pressurized air valve 2 is closed, the dome drain valve 3 and the tube sheet vent valve 5 are opened, After the inside of the dome is brought to normal pressure, the air scrubbing valve 8 is opened, air is sent into the filter through the valve, and the suspended solids adhering to the outside of the hollow fiber membrane are further removed by scrubbing with air bubbles, and then backwashed and discharged. Open the valve to drain the water in the filter (step 19), then close the backwash discharge valve 9, open the water inlet valve 7 and the tube sheet vent valve 5, and fill the liquid under the tube sheet via the valve 7. (Step 2G), then dome drain valve 6
Then, the tube plate vent valve 5 is closed and the upper body is filled with liquid (step 21), and after the upper body is filled with water (step 22), the to-be-treated liquid population valve and the treated liquid (filtered water) outlet valve are opened to filter the liquid. The method of restarting was adopted.

The present invention is an effective method when the hollow fiber membrane is heavily contaminated, especially when the bubble point of the hollow fiber is high and exceeds the backwash pressure, so that air does not pass through the membrane surface at the end (step 5).

The invention described in claim 1 is different from the conventional method in that it incorporates two forced scrubbing steps following the step of backwashing the hollow fiber membrane with pressurized air (step 5). They are different.

That is, after completing step 4, the backwash discharge valve 9 is opened and the water in the filter is discharged all at once to backwash the hollow fiber membrane (step 5).
), in order to reduce the amount of waste liquid generated at this time, the liquid under the tube plate is blown over the entire surface and drained to an extent of less than 7 cm.Then, the backwash discharge valve 9 is closed, and the dome drain valve 3, tube plate vent valve 5, and Open the water inlet valve 7, supply water (this water may be condensed water, pure water, or the water to be treated) to the filter from the water inlet valve 7, and fill the liquid to the bottom of the tube plate (step 6). Next, the tube sheet vent valve 5 is closed and the liquid is filled to the dome drain opening or the lower part of the dome drain lobe (step 7), and then the dome drain valve 5 and the water inlet valve 7 are closed, and the air scrubbing valve 8, the tube sheet vent valve 5, and the The compressed air valve 2 is opened and air scrubbing is performed with air introduced through the air scrubbing valve while pushing out the liquid on the tube sheet until the liquid level reaches the tube sheet (step 8). In this process, air scrubbing is performed while pushing the water on the tube sheet from the inside of the hollow fiber to the outside, making it possible to more effectively remove suspended matter adhering to the hollow fiber membrane. can. Then, the pressurized air valve 2 is closed and scrubbing is continued for about 10 to 20 minutes with air introduced through the air scrubbing valve 8 (step 8). Next, the tube sheet vent valve 5 is closed, the backwash discharge valve 9 is opened, and while introducing scrubbing air, the liquid containing the suspended solids peeled off by scrubbing under the tube sheet is forcibly discharged ( Step 18), close the air scrubbing valve 8 and open the dome drain valve to release the pressure inside the filter. Step 19), and then fill the tube plate with liquid below (step 20) and upper shell liquid (step 20) as in the conventional method. After performing step 21), filtration of the liquid to be treated is started again.

As described above, in the invention recited in claim 1, the tube sheet underlining process (step 6), the upper body liquid filling (up to the dome drain port), and the scrubbing while pushing out the liquid in the upper body part under pressure. Because the process of performing is added, backwashing and scrubbing can be performed more efficiently than conventional methods.

The invention described in claim 2 provides the second scrubbing step 9 and step 1 in the method described in claim 1.
During Step 9, the air scrubbing valve 8 is closed, the dome drain valve 3 and the water inlet valve 7 are opened, and liquid is filled at the tube plate ridge (Step 10).
), the step of closing the tube plate drain valve 5 and filling the liquid to the lower part of the tetome drain or dome drain port (step 11)
), a step of closing the dome drain valve 6 and water inlet valve 7 and opening the pressurized air valve 2 to pressurize the upper part of the dome (step 12), opening the backwash discharge valve 9 and draining the water in the filter to the bottom of the tube plate. Discharging step (step 13), closing the pressurized air valve 2 and backwash discharge valve 9, opening the tube sheet vent valve 5, dome drain valve 3, and water inlet valve 7 to fill the bottom of the tube sheet with liquid. (Step 14) A step of closing the tube plate vent valve 5 and filling the dome drain port or the lower part of the dome drain port with liquid (Step 15), closing the dome drain valve 3 and the water inlet valve, and air scrubbing valve 8;
a step (step 16) of opening the tube sheet vent valve 5 and the pressurized air valve 2 to push out the liquid on the tube sheet and performing air scrubbing with air introduced through the air scrubbing valve until the liquid level reaches the tube sheet; A series of steps (a combination of steps 10 to 17) of closing the pressurized air valve 2 and scrubbing for about 10 to 20 minutes with air introduced through the air scrubbing valve 8 (step 17) is performed. -As a combination, it is one that has advanced assembly skills or more, and can perform backwashing more completely than the invention recited in claim 1.

〔Effect of the invention〕

The present invention effectively removes suspended solids attached to hollow fiber membranes with poor removability by incorporating a step of scrubbing at the same time as backwashing (step 8.18) into the backwashing step of a hollow fiber membrane filter. can be done.

[Brief explanation of drawings]

FIG. 1 is a flow diagram illustrating the method of the present invention. 1... Vent valve, 2... Pressurized air valve, 6... Dome drain valve, 4... Processing liquid (filtrate water) outlet valve, 5...
・Pipe plate vent box, 6... Liquid population valve to be treated, 7... Water inlet valve, 8... Air scrubbing valve, 9... Backwash discharge valve, 10... Filtration device, 11.・・Tube plate, 12・・
・Hollow fiber membrane bundle patent applicant Hiroki Nakamoto, representative of Ebara Corporation
Akiyoshi Inoue
Mine Katsura procedure amendment (Method) April 4, 1986 Michibe Uga, Commissioner of the Patent Office 1, Indication of the case Patent Application No. 3415 of 1988 Title of the invention Hollow fiber filter backwashing method 5 Relationship with the case of the person making the amendment Patent applicant address 11-1 Haneda Asahi-cho, Ota-ku, Tokyo Name
(023) Ebara Corporation Representative Hatakeyama
Seiji (and 2 others) 5 Date of amendment order i Mizo Do\

Claims (1)

[Claims] 1. A method for filtering suspended matter contained in radioactive waste liquid or condensate by passing the entire amount of radioactive waste liquid or condensate from the outside to the inside of a hollow fiber membrane, which comprises the following (A) )from(
A method for backwashing a hollow fiber membrane, characterized by sequentially performing the steps L). (A) Step of supplying radioactive waste liquid or condensate to the hollow fiber membrane filter (10) for filtration (Step 1), stopping filtration after the differential pressure reaches a predetermined pressure (Step 2), and thereafter Step (Step 3) of opening the dome drain valve (3) and pressurized air valve (2) to drain the dome (B) Step of closing the dome drain valve (3) and pressurizing the dome with pressurized air (Step 4) (C) Open the backwash discharge valve 9 and remove the tube plate 11 or
(Step 5) (D) Close the pressurized air valve 2 and backwash discharge valve 9, open the tube plate vent valve 5, dome drain valve 3, and water inlet valve 7 to drain the waste liquid to the bottom of the pipe. Step of filling the liquid up to the bottom of the plate (Step 6) (E) Step of closing the tube sheet vent valve 5 and filling the liquid up to the dome drain port or the lower part of the dome drain port (Step 7) (F) Dome drain valve 3 and Step 8 of closing the water inlet valve 7 and opening the air scrubbing valve 8, tubesheet vent valve 5, and pressurized air valve 2 to push out the liquid on the tubesheet and perform air scrubbing until the liquid level reaches the tubesheet. ) (G) Step of closing the pressurized air valve 2 and continuing scrubbing while sending air into the liquid under the tube sheet (Step 9) (H) Closing the tube sheet vent valve 5 and opening the backwash discharge valve 9 to drain the pipe. Step of forcibly discharging the waste liquid under the plate (Step 18) (I) Step of closing the air scrubbing valve 8 and opening the dome drain valve to release the pressure inside the filter (Step 19) (J) Backwash discharge valve 9 close the tube plate vent valve 5, water inlet valve 7
(Step 20) (K) Close the tube sheet vent valve 5 and dome drain valve 3, open the vent valve 1, and fill the upper shell with liquid (Step 21) L) After filling with water, close the vent valve 1 and water inlet valve 7 to stop the process (Step 22) 2. Pass the entire amount of radioactive waste liquid or condensate from the outside to the inside of the hollow fiber membrane to remove radioactive waste liquid or condensate. A method for filtering suspended solids contained in (A) to (
In a method of sequentially carrying out the steps L), backwashing of a hollow fiber membrane is characterized in that one or more sets of steps (M) to (T) are incorporated between steps G and H. Method. (A) Step of supplying radioactive waste liquid or condensate to the hollow fiber membrane filter (10) for filtration (Step 1), stopping filtration after the differential pressure reaches a predetermined pressure (Step 2), and thereafter Step (Step 3) of opening the dome drain valve (3) and pressurized air valve (2) to push out the dome drain (B) Step of closing the dome drain valve (3) and pressurizing the dome with pressurized air ( Step 4) (C) Open the backwash discharge valve 9 and remove the tube plate 11 or
(Step 5) (D) Close the pressurized air valve 2 and backwash discharge valve 9, open the tube plate vent valve 5, dome drain valve 3, and water inlet valve 7 to drain the waste liquid to the bottom of the pipe. Step of filling the liquid up to the bottom of the plate (Step 6) (E) Step of closing the tube sheet vent valve 5 and filling the liquid up to the dome drain port or the lower part of the dome drain port (Step 7) (F) Dome drain valve 3 and Step 8 of closing the water inlet valve 7 and opening the air scrubbing valve 8, tubesheet vent valve 5, and pressurized air valve 2 to push out the liquid on the tubesheet and perform air scrubbing until the liquid level reaches the tubesheet. ) (G) Step of closing the pressurized air valve 2 and continuing scrubbing while sending air into the liquid under the tube sheet (Step 9) (H) Closing the tube sheet vent valve 5 and opening the backwash discharge valve 9 to drain the pipe. Step of forcibly discharging the waste liquid under the plate (Step 18) (I) Step of closing the air scrubbing valve 8 and opening the dome drain valve to release the pressure inside the filter (Step 19) (J) Backwash discharge valve 9 close the tube plate vent valve 5, water inlet valve 7
(Step 20) (K) Close the tube sheet vent valve 5 and dome drain valve 3, open the vent valve 1, and fill the upper shell with liquid (Step 21) L) After filling with water, close the vent valve 1 and water inlet valve 7 to stop the operation (Step 22) (M) Close the air scrubbing valve 8 and open the dome drain valve 3 and water inlet valve 7 to drain the liquid to the bottom of the tube plate. Step of filling (Step 10) (N) Step of closing tube plate drain valve 5 and filling with liquid up to the dome drain port or the lower part of the dome drain port (Step 11) (O) Dome drain valve 3 and water inlet valve 7 Close the pressurized air valve 2 and pressurize the dome with pressurized air (Step 12) (P) Open the backwash discharge valve 9 and drain the waste liquid to the tube plate 11 or the lower part of the tube plate 11 using air pressure. Discharge step (Step 13) (Q) Close the pressurized air valve 2 and backwash discharge valve 9, open the tube sheet vent valve 5, dome drain valve 3, and water inlet valve 7 to fill the liquid to the bottom of the tube sheet. Step (Step 14) (R) Step of closing the tube sheet vent valve 5 and filling the dome drain port or the lower part of the dome drain port with liquid (Step 15) (S) Closing the dome drain valve 3 and the water inlet valve 7, Step (T) of opening the air scrubbing valve 8, tube sheet vent valve 5, and pressurized air valve 2 and performing air scrubbing while pushing out the liquid on the tube sheet until the liquid level reaches the tube sheet. (T) Close the pressurized air valve 2. A process in which scrubbing continues while blowing air into the liquid below the tube sheet.