JPH1085566A - Pleated type filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discharge backwash water uniformly and improve the backwash efficiency by feeding water in a body vessel with a pleated element and increase the resistance on the outer surface of a pleated type filter membrane at the time of backwashing. SOLUTION: At the time of backwashing, a valve 6 is opened and the inside of a cover vessel 4 is pressurized by compressed air in an air tank 7. After pressurizing, when a drain valve 11 is opened quickly, the air in the cover vessel 4 is expanded, following which backwash water in the cover vessel 4 is backwashed from the inner surface to the outer surface of a plated type membrane 12 to backwash elements 12. At the time of repeating the operation, the inside of the cover vessel 4 and the body vessel 3 are in the state of being filled sufficiently with reinforcing water supply from a reinforcing water line 8 and a valve 9, and then the operation of pressurizing by the compressed air in the air tank 7 and opening the drain valve 11 is repeated to backwash the pleated type elements 12. The water level in a filter is adjusted by the arrangement and efficient backwashing is carried out to uniformize the backwash intervals and extend the period of use.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pleated filter.

[0002]

2. Description of the Related Art For example, as a filtration device used for separating and removing a suspended material mainly composed of iron rust present in condensate in a thermal or nuclear power plant,
A pre-coat type filtration device for pre-coating a filter aid such as powdered ion exchange resin on a fibrous or stainless steel wire mesh element and separating and removing suspended matter with a filter aid pre-coat layer has been adopted. A pleated filter equipped with a pleated element that can be operated without using a filter aid has come to be used.
Since the pleated filtration device can be operated without using a filter aid, the filter aid contained in the waste liquid generated by the conventional precoat filter is eliminated, and the amount of waste generated is reduced. In addition, because of its excellent removal performance, it is widely used in water treatment apparatuses for removing various suspended matters. In the pleated filtration device, as the filtration processing time elapses, the suspension to be removed in the raw water is captured on the outer surface of the membrane, and the filtration efficiency of the membrane gradually decreases. This phenomenon will be described below.

FIG. 4 shows an example of a schematic configuration around a filter of a pleated filter, in which a pleated element 12 has a tube sheet 13 sandwiched between a body container 3 and a lid container 4.
Shows a case where a plurality of cables are suspended.

[0004] Raw water requiring filtration is filtered through a raw water inlet pipe 1 to the body vessel 3 and flows inward from the outer surface of the pleated filtration membrane bundled in the pleated element 12. , Collected in the lid container 4 and sent to the downstream system via the treated water outlet pipe 2. The suspension separated by this filtration is captured and accumulated on the outer surface of the pleated filtration membrane, whereby the pores opened in the pleated filtration membrane are gradually closed, and the filtration resistance of the pleated filtration membrane is accordingly reduced. And the filtration pressure difference rises. When the filtration pressure difference reaches the specified value, the pleated element is backwashed. In the backwashing of the pleated type element, the backwash water held in the lid container 4 is pressure-fed from the air tank 7 by high-pressure air supplied from the air valve 6 and the air pipe 5 to flow from the inside to the outside of the pleated type filtration membrane. High pressure air backwashing is performed to remove the suspended matter on the outer surface of the pleated filtration membrane. The suspension separated from the filtration membrane is discharged from the body container 3 through the drain pipe 10 together with the backwash water. In order to improve the backwash effect of the pleated element, the high-pressure air backwash is repeatedly performed. That is,
After filling the lid container 4 with the make-up water by opening the make-up water line 8 and the valve 9 and supplying the back container 4 with backwash water, the inside of the pleated filtration membrane is pressurized with high-pressure air from the inside to the outside as in the above-described operation. Backwash, and discharge from the barrel 3. Here, since the specific resistance of the filtration membrane is small, part of the backwash water filled in the lid container 4 flows into the body container 3 through the filtration membrane before applying air pressure. In addition, even if repeated backwashing is performed, a large amount of water cannot be flowed in one backwashing, so that the suspended matter trapped on the outer surface cannot be completely removed, and a part remains.
Therefore, the filtration pressure difference immediately after performing backwash does not recover to the initial filtration pressure difference when the pleated element was subjected to filtration,
The filtration pressure difference becomes higher than the initial filtration pressure difference, and then the filtration pressure difference when subjected to the filtration treatment again increases by that amount. By repeating the filtration process and the backwash, the suspension remaining on the outer surface of the pleated element without being removed by the backwash gradually increases, so that the filtration differential pressure increases quickly, and the backwash interval becomes short,
The recovery of the filtration pressure difference due to the backwashing is substantially eliminated, and the use of the pleated element is no longer possible. When this happens, the pleated element is replaced with a new one.

[0005] Fig. 5 shows an example of a change in the pressure difference in water flow of the filtration device. This figure shows the relationship between the operating time and the filtration pressure difference when water flow and backwashing of the pleated filter were repeated. The horizontal axis represents the operation time, and the vertical axis represents the pressure difference between the fluids contained in the inlet pipe 1 and the outlet pipe 2, that is, the filtration pressure difference. Curve a indicates a change in filtration differential pressure, and the filtration differential pressure gradually increases as the operation time elapses. This is because suspended matter accumulates on the surface of the pleated element 12 and the filtration resistance of the pleated element 12 increases. The filtration process was stopped at point B, backwashing was performed, and the reduced differential pressure was point C. In the subsequent filtration process operation, the filtration process is stopped when the operation time has reached near the point B differential pressure and backwashing is performed. Here, as described above, since the suspended matter remains on the outer surface of the pleated element every time the backwashing is performed, the differential pressure rise with the elapse of the filtration operation time is filtered to the differential pressure at the point B, and the filtration and the backwashing are performed. Repeatedly, the operation interval t becomes short as t ', t ", t""due to the suspended matter remaining on the outer surface of the pleated filtration membrane.
The operation of the pleated filter was complicated, and the life of the pleated element was short. A related device of this type is disclosed, for example, in Japanese Patent Application Laid-Open No. HEI 8-17243.

[0006]

The above prior art has a problem that the filtration time is gradually shortened because the trapped suspension remains on the outer surface of the pleated element every time the pleated element 12 is backwashed. .

[0007] This is because at the time of backwashing, the specific resistance of the pleated type filtration membrane is small, and the backwash water filled in the lid container 4 partially flows into the body container 3 through the filtration membrane before applying air pressure. This is because a large amount of water flows in a portion where the backwash water easily passes, and the backwash becomes uneven.

[0008] It is an object of the present invention to efficiently remove a suspension trapped on the outer surface of a pleated element.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a body container to which a pleated element is mounted in order to increase the specific resistance of the pleated filter when the pleated element is backwashed. By increasing the resistance of the outer surface of the pleated filtration membrane by filling with water, uniform distribution of the backwash water is achieved and the backwash efficiency is improved.

[0010] When backwashing the pleated element, not only the lid container 4 but also the body container 3 is filled with make-up water to increase the resistance of the outer surface of the pleated filter membrane. It will be evenly distributed in the membrane. Since the pleated filter membrane can be backwashed with air, only the inside of the body container 3 is filled with make-up water to increase the resistance of the pleated filter membrane. Evenly distributed. Further, by performing the backwashing while changing the level of the make-up water in the body container 3 to improve the backwashing effect, the filter membrane can be backwashed in several parts, and the extreme backwashing becomes possible. In addition, the backwashing effect is improved, and the amount of the suspension remaining on the outer surface of the pleated element is reduced.

[0011]

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

The function of filtering raw water with a pleated element remains unchanged.

FIG. 1 shows an example of the overall structure of a filtration device of the type in which an element is suspended. An inlet pipe 1 is connected to a lower part of the body container 3 and an outlet pipe 2 is connected to an upper part thereof.

In the structure of the filtration device, backwashing of the pleated element 12 is performed as follows.

First, with the valves 6, 9 and 11 closed, raw water flows from the inlet pipe 1 to the body vessel 3 and treated water is taken out from the outlet pipe 2 to perform a filtration operation. During the filtration operation, the suspension in the raw water becomes pleated.
The backwashing operation is performed when the filtration pressure difference rises as shown in FIG. 5 and reaches the specified pressure difference point B as shown in FIG. First, the valves 20 and 21 are closed to stop the flow of raw water. Next, the valve 6 is opened and the lid container 4 is opened with the compressed air in the air tank 7.
Pressurize inside. After the pressurization, the air in the lid container 4 expands by rapidly opening the drain valve 11, and accordingly, the backwash water in the lid container flows back from the inner surface of the pleated filtration membrane to the outer surface side, The pleated element 12 is backwashed. This system can be repeatedly operated. In the case of repeating the operation, the inside of the lid container 4 and the inside of the body container 3 are filled with the make-up water supplied from the make-up water line 8 and the valve 9, and then the air tank 7 is made again.
The operation of pressurizing with compressed air inside and opening the drain valve 11 is repeated to backwash the pleated element 12.

According to the backwashing method of the pleated filter of the present embodiment, since the outer surface of the pleated filter is filled with water, the backwash water does not pass through the filter before applying air pressure. Since the water pressure is applied to the outer surface, the backwash water is uniformly distributed without being affected by the dispersion of the suspended matter capture, so that efficient backwash can be performed.

FIG. 2 shows an application example of the method for backwashing a pleated filtration membrane. In the case of a type in which backwashing with air is possible with a pleated filtration membrane, after the inside of the lid container 4 is emptied, the valve 6 is opened, the air in the air tank 7 is supplied, and the air in the lid container 4 is removed. Apply pressure. Next, the drain valve 11 is quickly opened to flow compressed air held in the lid container 4 from the inner surface to the outer surface of the pleated filtration membrane, thereby backwashing the pleated element 12. This system can be repeatedly operated. In the case of repeating the operation, only the inside of the body container 3 is filled with the make-up water by opening the make-up water line 8 and the valve 9 and then the inside of the lid container 4 is pressurized and then drained. The valve 11 is opened and the pleated element 12 is backwashed.

FIG. 3 shows a pleated filter in which the lower part of the pleated element is fixed. In the case of the lower fixed pleated element, backwashing is performed with backwash water from the lower part. That is, the valve 6 is opened, and the air in the air tank 7 is supplied to the backwash water held between the lower end plate 15 and the lower partition plate 16 at a stretch, and the air is removed from the inner surface of the pleated filtration membrane from below the pleated element. Backwash water is flown to the front side to backwash the pleated element 12. In the case of the pleated element lower fixed type, the backwash water flows from the element mounting portion where the resistance is small, and the backwash effect of the upper part of the pleated element is reduced. Change the water level and backwash.

That is, the makeup water is supplied from the makeup water line 8 and the valve 9 to adjust the water level at an arbitrary position of the element. The air supply valve 6 is opened to pressurize the backwash water between the filter lower mirror 15 and the lower partition plate 16, and the vent valve 18 is quickly opened to release the backwash water to the element 12 fixed to the lower partition plate 16. Backwash from inner surface to outer surface. At this time,
The lower part of the element with water on the outer surface of the element has a large resistance and the element part where air is in contact with the outer surface is only the resistance of the membrane and the resistance is small, so much backwash water flows to the part where the outer surface is in contact with air Therefore, the backwashing effect is improved.
By repeatedly backwashing while adjusting this water level,
Perform a uniform backwash of the pleated element.

[0020]

According to the present invention, as a backwashing method for removing a suspension adhered to the outer surface of a pleated filtration membrane using a pleated filtration apparatus, the water level in the filter is adjusted by pleating. Efficient backwashing of mold elements
It is possible to make the backwash interval uniform and extend the use period.

[Brief description of the drawings]

FIG. 1 is a system diagram of one embodiment showing a method for cleaning a pleated filtration device according to the present invention.

FIG. 2 is a system diagram of a second embodiment showing a method for cleaning a pleated filtration device according to the present invention.

FIG. 3 is a system diagram of a third embodiment showing a method for cleaning a pleated filter according to the present invention.

FIG. 4 is an explanatory view showing a conventional method for cleaning a pleated filtration device.

FIG. 5 is an explanatory diagram showing the performance of a conventional pleated filter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Inlet piping, 2 ... Outlet piping, 3 ... Body container, 4 ... Lid container, 5 ... Air piping, 6 ... Air supply valve, 7 ... Air tank,
8 make-up water pipe, 9 make-up water supply valve, 10 wash water discharge pipe, 11 wash water discharge valve, 12 pleated element, 13 partition plate.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Seiichi Kazama 3-1-1, Sakaicho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Plant

Claims (3)

[Claims] 1. A pleated type filtration membrane is used to perform a filtration treatment of raw water, and the backwashing of the filtration membrane is performed by flowing backwash water in a direction opposite to a flowing direction of an element. A pleated filtration device for removing a suspended substance adhering to a filter, wherein a natural backflow of the filtration membrane during backwashing is prevented and backwash water is uniformly distributed. 2. The pleated filtration device according to claim 1, wherein the resistance is increased by applying water pressure to the outer surface of the pleated filtration membrane with the filter body being water-filled. 3. The pleated filtration device according to claim 1, wherein the backwashing of the filtration membrane changes the water level of a body vessel on which the pleated filtration membrane is mounted, thereby changing the resistance of the outer surface of the pleated filtration membrane. .