JP2023167731A - Compression membrane for filter press and operation method - Google Patents

Abstract

To provide a compression membrane for a filter press and an operation method where backwashing can be performed while compressing a dehydrated cake.SOLUTION: In a filter press where a stock solution is supplied to a filtration chamber 9 formed between a pair of filter plates 4A, 4B with a filter cloth 21 for filtration stretched thereon: a compressed fluid is supplied to a compression chamber 13 formed in the filtration chamber 9 and a dehydrated cake in the filtration chamber 9 is compressed and dehydrated by expanding a compression membrane 12; backwashing can be performed while compressing the dehydrated cake by providing the compression membrane 12 made of the filter cloth having lower permeability than the filter cloth for filtration on the surface of the filter plate 4A for compression forming the compression chamber 13; and the shortening of an operation time and the reduction of power consumption can be realized.SELECTED DRAWING: Figure 2

Description

The present invention relates to a compressed membrane and an operating method for a filter press that utilizes a filter cloth having a different air permeability from that of a filter cloth as a compressed membrane.

Conventionally, in a filter press having a large number of filter plates, in order to carry out high-pressure dehydration, an undiluted solution is forced into a filtration chamber and filtered and dehydrated, and then a pressurized fluid is forced into a diaphragm filter plate for compression dehydration.
A diaphragm filter plate is generally a resin diaphragm stretched over a core plate, and there are methods to fix the diaphragm to the core plate using a holding plate and bolts, or to fix the diaphragm's engagement pieces to the core plate. It is formed using a method such as fitting into a matching groove.

Patent Document 1 discloses that from a compressed air supply section formed in a pair of processing bodies (filter plates) that housed filter cloths inside, between the back side of the filtration surface of the filter cloths and the filtration bed of the processing bodies (filter plates). A technique has been disclosed in which a compressed gas such as air is supplied to compress layered double hydroxide (dehydrated cake) accommodated between filter cloths.

Patent Document 2 discloses that an intermediate plate having a mud feeding port is provided between a pair of filter plates, and a first filter cloth and a first filter cloth are provided in each cake generation chamber formed between the intermediate plate and each filter plate. A filter press is disclosed in which a second filter cloth with a fine mesh is disposed.

JP2021-28288A Japanese Patent Application Publication No. 05-245309

Conventionally, when removing a diaphragm from a diaphragm filter plate, it was necessary to remove a large number of parallel filter plates from the filter press body, which took time, effort, and cost. When the removed diaphragm filter plate fixes the diaphragm with a holding plate and bolts, it is difficult to attach and remove the diaphragm because there are many parts. When the engagement piece of the diaphragm is fitted into the engagement groove of the core plate, it is difficult to fit the engagement piece of the diaphragm into the engagement groove of the core plate during manufacturing. If the diaphragm is forcefully inserted, the diaphragm will be deformed and the sealing performance will deteriorate, so there is a problem that high compression cannot be achieved. Furthermore, since the diaphragm stretched over the diaphragm filter plate was made of resin, it also had the problem of plastic deformation and premature breakage when high pressure was applied during operation.

Patent Document 1 discloses a technique for compressing and dewatering a dehydrated cake using a pair of filter cloths, and since a diaphragm is not used, problems such as the effort required to attach and remove the diaphragm and the deformation of the diaphragm do not occur. do not have. However, the filtration filter cloth itself is used as the filter cloth for squeezing, and as the supplied compressed gas leaks from the filter cloth for filtration, the squeezing surface becomes uneven, and the dehydrated cake cannot be squeezed uniformly. I couldn't do that. When the air permeability of the filtration filter cloth is lowered in order to prevent leakage of compressed gas, there has also been a problem in that the filter cloth becomes clogged early and the filtration efficiency decreases.

Patent Document 2 discloses a technique in which filter cloths with different air permeability are stacked in a filtration chamber, but the treatment liquid is passed through the first filter cloth and then the second filter cloth whose mesh is finer than the first filter cloth. This is a technology that performs precision filtration using filter cloths, and of the two filter cloths, the filter cloth with lower air permeability is not used as the filter cloth for compression. In other words, there has been no technology in which one of two types of filter cloths with different air permeability placed in a filtration chamber is used to compress a dehydrated cake.

The present invention provides a filter cloth for filtration in a filtration chamber formed between a large number of filter plates arranged in parallel, and that the compression filter plate forming a compression chamber located in the filtration chamber has a higher air permeability than the filter cloth for filtration. To provide a compressed membrane and an operating method for a filter press, characterized in that a compressed membrane composed of a thin filter cloth is stretched.

The present invention supplies a stock solution to a filtration chamber formed between a pair of filter plates on which a filter cloth is stretched, and then supplies a compressed fluid to a compression chamber formed in the filtration chamber to expand the compression membrane. In a filter press that compresses and dehydrates the dehydrated cake in the filtration chamber, the surface of the compression filter plate that forms the compression chamber is equipped with a compression membrane made of filter cloth that has lower air permeability than the filtration filter cloth. Backwashing can be performed while squeezing the dehydrated cake produced during the process.

The compressed membrane is stretched so as to cover both filtration surfaces of the compressed filter plates that are alternately arranged in parallel with the filter plates, and is sealed at a position where the compressed filter plates are in contact with the filter frame. Since the compressed membrane is closely fixed to both filtration surfaces of the compressed filter plate, the compressed fluid in the compressed chamber is prevented from leaking from the peripheral surface of the filter frame.

The compression membrane is stretched so as to cover one side of the filtration surface of the compression filter plates that are arranged in series, and a sealing process is applied to the position of the compression filter plate in contact with the filter frame, so that the compression membrane can be compressed. Since it is closely fixed to one side of the filtration surface of the filter plate, the compressed fluid in the compression chamber is prevented from leaking from the circumferential surface of the filter frame.

The pressing membrane hangs down from above the pressing filter plate so as to cover the filtration surface, so that the pressing membrane can be easily attached and removed.

After supplying the stock solution to the filtration chamber formed between a pair of filter plates covered with filter cloth, compressed fluid is supplied into the compression chamber formed in the filtration chamber, and the air permeability is lower than that of the filter cloth. The dehydrated cake generated in the filtration chamber is compressed by expanding the compressed membrane made of colored cloth, and the dehydrated cake is backwashed with the compressed fluid that passes through the compressed membrane and the filter cloth. Since backwashing can be performed at the same time, it is possible to shorten operating time and reduce power consumption.

The compressed membrane and operating method of the filter press of the present invention is to compress a dehydrated cake using a compressed membrane made of a filter cloth with lower air permeability than a filter cloth for filtration, and the compressed membrane is suspended from above the compressed filter plate. Because it has a simple structure, the number of parts is small, and the pressing membrane can be easily replaced. Furthermore, since the compressed membrane is made of filter cloth with high weather resistance, it will not break early even when subjected to high compression. Furthermore, when compressed fluid was supplied into the compression chamber, the resistance of the compression membrane with low air permeability prevented the compressed fluid from immediately passing through the compression membrane, and the pressure inside the compression chamber gradually increased, causing the compression membrane to swell uniformly in the vertical direction. This makes it possible to apply a squeezing action to the entire dehydrated cake. Since backwashing is performed while the compressed fluid in the squeezed membrane gradually flows from the squeezed membrane toward the dehydrated cake, the dehydrated cake can be cleaned evenly and evenly in the vertical direction. In this way, since squeezing and backwashing are performed while continuing to supply a constant amount of compressed fluid to the expanded squeezing membrane, there is no need to supply an excessive amount of compressed fluid, and the amount of compressed fluid used can be reduced. It becomes possible.

FIG. 2 is a side view of a filter press according to the present invention. Similarly, it is a main part sectional view of a filter plate for compression and a filter plate for filtration. Similarly, it is a front view of the filter plate for compression in FIG. 2. Similarly, it is a schematic diagram showing a state in which each filter plate is equipped with a filter cloth for filtration. Similarly, it is a sectional view showing another embodiment. Similarly, it is a sectional view of the filtration chamber during the press-fitting process. Similarly, it is a sectional view of the filtration chamber during the squeezing process.

FIG. 1 is a side view of a filter press according to the present invention.
In the filter press according to the present invention, a pair of guide rails 3 are bridged between a front frame 1 and a rear frame 2, and a large number of filter plates 4 are supported on the guide rails 3. A tightening cylinder 5 disposed on the rear frame 2 is connected to a movable head 6, and the tightening cylinder 5 opens and closes the parallel filter plates 4.

By moving the movable head 6 toward the front frame 1 and closing the filter plates 4, a stock solution supply path 7 is formed above the parallel filter plates 4. A stock solution supply pipe 8 communicating with the front end of the filter plate array is connected to the front frame 1 so that the stock solution can be supplied to the stock solution supply path 7. A filtration chamber 9 communicating with the stock solution supply path 7 is formed between each adjacent filter plate 4, and the stock solution supplied from the stock solution supply path 7 is separated into solid and liquid.

A filtrate discharge path 10 communicating with each filtration chamber 9 is formed below the parallel filter plates 4, and the separated filtrate is discharged. The filtrate discharge path 10 communicates with a filtrate discharge pipe 11 connected to the front frame 1, and the filtrate discharged into the filtrate discharge path 10 is discharged to the outside via the filtrate discharge pipe 11.

FIG. 2 is a sectional view of essential parts of a filter plate for compression and a filter plate for filtration, and FIG. 3 is a front view of the filter plate for compression in FIG. 2.
A pair of filtration filter cloths 21, 21 are suspended between the compression filter plate 4A and the filtration filter plate 4B. is covered. When the filter plates are closed, the stock solution supply holes 19A and 19B are opened above the compression filter plate 4A and the filter plate 4B, respectively, and the liquid supply plate is sandwiched and joined to the upper part of the filter cloths 21 and 21. The 22 stock solution supply ports 20 communicate with each other to form a stock solution supply path 7. The stock solution supplied through the stock solution supply path 7 flows into each filtration chamber 9 through a liquid supply path 33 that communicates with the stock solution supply port 20 .
In addition, although the large number of filter plates 4 in this embodiment are configured by arranging filter plates 4A for compression and filter plates 4B for filtration alternately in parallel, only the filter plates 4A for compression may be arranged in parallel as necessary. It's okay.

4 A of filter plates for compression have the compression membrane 12 stretched so that the whole filtration surface may be covered. In this embodiment, the compression membrane 12 is stretched on both sides of the filtration surface of the compression filter plate 4A, and compression chambers 13, 13 are formed between the compression filter plate 4A and the compression membranes 12, 12. The compression membrane 12 is formed of an expandable and deflated filter cloth, and is expanded by supplying compressed fluid such as air or liquid into the compression chamber 13 .

The compressed membrane 12 hangs down from above the compressed filter plate 4A so as to cover the filtration surface of the compressed filter plate 4A, and connects both hanging parts 35, 35 to one place with a connecting member 23 such as a screw or a cable tie. The above are connected. At this time, both hanging portions 35, 35 are located below the compression filter plate 4A. After the opposing surfaces of both hanging parts 35, 35 are overlapped, the overlapped parts are connected and fixed by the connecting member 23, but it is desirable to connect a plurality of parts to improve connectivity. In addition, the compressed membrane 12 may connect not only both hanging parts 35, 35 but also both side parts.

In this embodiment, since the compression membrane 12 plays the role of a conventional diaphragm, it is necessary to improve the sealing performance of the filter frame 30 so that the compressed fluid in the compression chamber 13 does not leak from the filter frame 30. be. Therefore, when the compressed membrane 12 is stretched over the compressed filter plate 4A, as shown in FIG. I'll keep it. The sealing process uses a known sealing process such as applying a resin. By applying the sealing process, the peripheral edge of the compressed membrane 12 and the filter frame 30 are in close contact with each other when the filter plates are closed, and the sealing performance of the compressed chamber 13 can be improved, so that compressed fluid does not leak from the filter frame 30. prevent. At this time, the entire surface of the filter bed 14A is covered.

Note that by closing the filter plate 4, the compressed membrane 12 can be brought into close contact with the compressed filter plate 4A. You can also use a board. Since the compressed membrane 12 comes into close contact with the compressed filter plate 4A by closing the filter plate, it is desirable that the lower ends of both hanging parts 35, 35 be located below the bottom of the filter frame 30.

Moreover, a pair of openings 34 are opened in the pressing membrane 12 at positions facing the stock solution supply hole 19A of the pressing filter plate 4A. The opening 34 is formed to have the same diameter as the stock solution supply holes 19A and 19B, and allows stock solution and compressed fluid to flow in when the filter plates are closed. Therefore, when the pressing membrane 12 is suspended from above each pressing filter plate 4A, the openings 34 are aligned so that they can communicate with the stock solution supply holes 19A and 19B.

As shown in FIG. 2, the compression filter plate 4A and the filter plate 4B have filtrate discharge holes 32A and 32B formed at the bottom of the filter beds 14A and 14B of each filter plate 4, respectively, and each discharge hole 32A, Filtrate discharge passages 10A and 10B are formed which communicate with each of the filtrate discharge passages 32B. The filtrate discharged from the filtrate discharge hole 32A is discharged to the outside through the filtrate discharge path 10A, and the filtrate discharged from the filtrate discharge hole 32B is discharged to the outside through the filtrate discharge path 10B. . Further, the filtrate discharge hole 32A and the filtrate discharge path 10A communicate with the compression chamber 13 and with the filtration chamber 9 via the compression membrane 12. During the dehydration process, it becomes a discharge path for filtrate, and during the compression process, it becomes a supply path for compressed fluid. On the other hand, the filtrate discharge hole 32B and the filtrate discharge path 10B communicate with the filtration chamber 9, and serve as a discharge path for the separated filtrate. As shown in FIG. 3, each of the filtrate discharge passages 10A and 10B is an opening formed on the side of the filter plate, and the openings communicate with each other when the filter plate is closed, thereby extending below the filter plate row.

The filtrate discharge hole 32B provided in the conventionally used filter plate 4B communicates with the filtration chamber 9, as shown in FIG. The liquid passes through the cloth 21 and is discharged from the filtrate discharge hole 32B. On the other hand, the filtrate discharge hole 32A provided in the compression filter plate 4A is configured to communicate with the compression chamber 13 and the filtration chamber 9, and is covered with the compression membrane 12 and the filtration filter cloth 21. . Therefore, the filtrate discharged from the dehydrated cake produced in the filtration chamber 9 passes through the filtration filter cloth 21, passes through the compression filter cloth 12, and is discharged from the filtrate discharge hole 32A.

FIG. 4 is a schematic diagram showing a state in which a filter cloth for filtration is attached to each filter plate.
A pair of filtration filter cloths 21 for separating solid and liquid from the stock solution is provided between the filter plates 4A for pressing and the filter plates 4B for filtration that are alternately arranged in parallel. The filter cloth 21 for filtration is constructed so that a drive machine (not shown) and a sprocket 24 are interlocked, and a chain 25 is wound around the sprocket 24 . One end of the chain 25 is connected to the upper filter cloth core 26, and the other end is connected to the lower filter cloth core 27. Since the upper filter cloth core 26 and the lower filter cloth core 27 are inserted into a bag portion in which the filter cloth is made into a bag, the chain 25 and the filter cloth 21 are formed in an endless shape.

When the sprocket 24 is rotated clockwise, the filter cloth 21 starts to descend, and the dehydrated cake adhering to the filter cloth 21 is removed along the return roll 28 by reversing the cloth 21. Forcibly peel it off from the filter cloth. When the filter cloth 21 for filtration is lowered to a predetermined position, the driving machine is reversed and the filter cloth 21 for filtration is raised.

In addition, in this embodiment, the traveling filter cloth 21 is used, but as another embodiment, the filter press may be constructed using a fixed filter cloth 21. The method of attaching the fixed type filter cloth 21 to the compression filter plate 4A is the same as the method of attaching the compression membrane 12 to the compression filter plate 4A in this embodiment. The filter cloth 21 for filtration is suspended from above the filter plate 4A, and both hanging parts 35, 35 are connected by a connecting member below the filter plate, if necessary. In other words, the compression filter plate 4A is covered with two types of filter cloths.

In this embodiment, two types of filter cloths are used: a filter cloth 21 for filtration and a compressed membrane 12. The filter cloth 21 for filtration is a pair of well-known filter cloths, and performs solid-liquid separation of the stock solution supplied between the filter cloths 21, 21. The squeezing membrane 12 is used for squeezing the dehydrated cake produced between the filter cloths 21 and 21, and is configured to be expandable with the compressed fluid supplied to the squeezing chamber 13. The compressed membrane 12 uses a filter cloth having lower air permeability than the filter cloth 21 for filtration.

The compressed membrane 12 is not particularly limited as long as it has a lower air permeability than the filter cloth 21, but it is preferable to use a filter cloth with an air permeability of 1/100 to 1/1000 of that of the filter cloth 21. . By using a filter cloth with low air permeability, it becomes a resistance to the passage of compressed fluid, and the amount of compressed fluid that can permeate through the compressed membrane 12 decreases, and the passage speed decreases. As a result, the pressure inside the compression chamber 13 gradually increases, so that the compression membrane 12 can be expanded with the compressed fluid supplied into the compression chamber 13.

FIG. 5 is a sectional view showing another embodiment.
A compression membrane 12 is stretched on one side of the filtration surface of the compression filter plate 4A, and a compression chamber 13 is formed on one side of the filtration surface. A filter press may be constructed by arranging a large number of filter plates for compression 4A formed in this manner in succession. In this case as well, similarly to the present embodiment, the compressed membrane 12 is hung from above and stretched, but an elevating mechanism such as a sprocket is provided above the compressed filter plate 4A so that the compressed membrane 12 can be raised and lowered. It's okay. In this form as well, a sealing process is applied to the position where the compressed membrane 12 comes into contact with the filter frame 30. As a result, the compressed membrane 12 is closely fixed to the filter frame 30 when the filter plate is closed, so that leakage of compressed fluid from the peripheral surface of the filter frame 30 can be prevented.
Hereinafter, embodiments of the present invention will be described based on FIGS. 6 and 7.

<Closing process>
A large number of filter plates 4 are closed with a tightening cylinder 6, and a filtration chamber 9 is formed between adjacent compression filter plates 4A and filtration filter plates 4B. A pair of filter cloths 21 are stretched in each filtration chamber 9 and cover the inside of the filtration chamber 9. At this time, a stock solution supply path 7 is formed above the closed filter plate row, and filtrate discharge paths 10A and 10B are formed below the filter plate row.

<Press-fitting process>
The stock solution supplied at a constant pressure from the stock solution supply pipe 8 flows into each filtration chamber 9 via the stock solution supply path 7, and then is separated into solid and liquid between the filter cloths 21, 21 in the filtration chamber 9. The filtrate in the filtration chamber 9 is discharged as filtration progresses due to the injection pressure of the continuously supplied stock solution. The discharged filtrate is discharged from the filtrate discharge holes 32A and 32B of the compression filter plate 4A and the filtration filter plate 4B.

Specifically, the filtrate discharged from the squeeze filter plate 4A passes through the filter cloth 21 from inside the filtration chamber 9, passes through the squeeze membrane 12, and is then discharged from the filtrate discharge hole 32A. Ru. On the other hand, the filtrate discharged from the filter plate 4B passes through the filter cloth 21 from inside the filtration chamber 9, and then is discharged from the filtrate discharge hole 32B. The filtrate discharged from the filtrate discharge holes 32A and 32B is discharged to the outside through filtrate discharge passages 10A and 10B that communicate with the respective discharge holes.

The filter cloth 21 for filtration swells toward the filter beds 14A, 14B of the filter plate 4A for compression and the filter plate 4B for filtration by the stock solution supplied between the filter cloths 4, 4 when the stock solution is press-injected. Accordingly, the compressed membrane 12 adjacent to the filter cloth 21 located on the filter bed 14A side swells toward the compressed chamber 13 side.
Note that the stock solution is press-fitted for a predetermined period of time.

<Squeezing process (backwashing process)>
After the press-fitting process is completed, the squeezing process is started. As shown in FIG. 7, compressed fluid is supplied from a filtrate discharge path 10A that communicates with a filtrate discharge hole 32A formed in a filter plate for compression 4A. The supplied compressed fluid flows into the compression chamber 13 formed between the compression filter plate 4A and the compression membrane 12 through the filtrate discharge hole 32A.

After the compressed fluid flows into the squeezing chamber 13, it gradually expands the squeezing membrane 12 toward the dewatered cake. At this time, since the surface of the compression chamber 13 is covered with the compression membrane 12 made of filter cloth with low air permeability, the supplied compressed fluid cannot immediately pass through the compression membrane 12, and the pressure inside the compression chamber 13 gradually decreases. becomes higher. As a result, the compressed membrane 12 expands, and the expanded compressed membrane 12 applies compressing pressure uniformly to the dehydrated cake formed between the filter cloths 21 and 21, so that water is efficiently discharged from the dehydrated cake. . In other words, by forming the compressed membrane 12 using a filter cloth with low air permeability and reducing the passage efficiency of the compressed fluid flowing into the compression chamber 13, the compressed membrane 12 can be expanded, and pressing pressure can be applied to the dehydrated cake. I can do it.

Thereafter, the compressed fluid in the compression chamber 13 passes through the compression membrane 12 and the filter cloth 21 and flows into the dewatered cake. Specifically, it flows from the squeeze filter plate 4A side toward the filtration filter plate 4B side so as to penetrate the dehydrated cake. At this time, the mother liquor in the dehydrated cake is replaced with the inflowing compressed fluid, and impurities such as soluble compounds in the dehydrated cake are removed.

In the conventional backwashing process, there was a problem that the compressed fluid supplied from the filtrate discharge hole 32A below the filter plate 4 did not reach above the dehydrated cake, resulting in uneven cleaning of the cake. Since the backwashing process is started with the compressed membrane 12 expanded, it is possible to uniformly flow the compressed fluid toward the dehydrated cake from the numerous pores opened throughout the compressed membrane 12, and the dehydrated cake is moved in the vertical direction. Can be cleaned evenly over the entire area.

The compressed fluid that has passed through the dehydrated cake is discharged from the filtrate discharge hole 32B, and is discharged to the outside through the filtrate discharge path 10B.

In this embodiment, the compression chamber 13 with which the filtrate discharge hole 32A communicates is covered with the compression membrane 12 with low air permeability, and this acts as a passage resistance for the compressed fluid, so that the compressed fluid cannot immediately pass through the compression membrane 12. Since the pressure in the squeezing chamber 13 gradually increases and the squeezing membrane 12 expands, a squeezing action can be applied to the dehydrated cake. Since the compressed fluid gradually flows from the expanded squeezing membrane 12 toward the dehydrated cake, backwashing can be performed at the same time while giving a squeezing action to the dehydrated cake. That is, unlike the conventional squeezing process and backwashing process, the dehydrated cake can be squeezed and washed in one process.

Since the squeezing process is carried out using the operating method of a conventional backwashing process, equipment such as a squeezing tank, a squeezing pump, and piping, which are required in the conventional squeezing process, can be omitted. Since it is also possible to shorten the compression time, it is also possible to shorten operating time and reduce power consumption.

Note that the compressed fluid may be air or liquid, which may be used alone or in combination, and may be selected as appropriate depending on design considerations. Further, forward cleaning may be performed before the squeezing process (backwashing process).

<Opening process>
After the squeezing process is completed, the tightening cylinder 5 is driven to release the movable head 6, and the many parallel filter plates 4 are moved to the rear frame 2 side to open them, and the dehydrated cake in the filtration chamber 9 is removed. Discharge. The dehydrated cake falls out of the machine due to its own weight, the running of the filter cloth 21, etc.

When cleaning the filter cloth 21, a known cleaning mechanism 31 is used for cleaning. During solid-liquid separation, the SS content in the stock solution adheres to the filter cloth 21 for filtration, so the squeeze membrane 12 basically does not require cleaning, but if cleaning is required, it can be cleaned using a known cleaning mechanism. do.

The present invention is not limited to the embodiments detailed above. Appropriate modifications can be made without departing from the spirit of the invention.

The squeezing membrane and operating method of a filter press according to the present invention includes squeezing a dehydrated cake while expanding the squeezing membrane stretched over the filtration surface of the squeezing filter plates that are alternately arranged in parallel with the filtration filter plates. Since it can be backwashed and backwashed during the pressing process, it can shorten operating time and reduce power consumption, making it an environmentally friendly filter press. In addition, since the dewatered cake is squeezed using a pressing membrane made of a filter cloth with a higher permeability than a filter cloth for filtration, a filter cloth with an optimal permeability can be used as the pressing membrane depending on the properties of the inflowing sludge. It can handle sludge of all types.

4A Squeezing filter plate 4B Filtration filter plate 9 Filtration chamber 12 Squeezing membrane 13 Squeezing chamber 21 Filtration filter cloth 30 Filter frame

Claims (5)

After supplying the stock solution to a filtration chamber (9) formed between a pair of filter plates on which a filter cloth (21) for filtration is stretched, compressed fluid is supplied to a compression chamber (13) formed in the filtration chamber (9). In a filter press that compresses and dehydrates a dehydrated cake in a filtration chamber (9) by supplying and expanding a compressed membrane (12),
A pressing membrane (12) made of a filter cloth with lower air permeability than the filter cloth (21) is placed on the surface of the pressing filter plate (4A) forming the pressing chamber (13).
A compressed membrane for a filter press characterized by being equipped with. The compressed membrane (12) is stretched so as to cover both filtration surfaces of the compressed filter plates (4A) that are alternately arranged in parallel with the filter plates (4B),
The compressed membrane for a filter press according to claim 1, wherein the compressed filter plate (4A) is sealed at a position facing the filter frame (30). The compression membrane (12) is stretched so as to cover one side of the filtration surface of the compression filter plates (4A) arranged in series, and
The compressed membrane for a filter press according to claim 1, wherein the compressed filter plate (4A) is sealed at a position facing the filter frame (30). The filter press according to any one of claims 1 to 3, wherein the pressing membrane (12) hangs down from above the pressing filter plate (4A) so as to cover the filtration surface. Squeezed membrane. After supplying the stock solution to a filtration chamber (9) formed between a pair of filter plates on which a filter cloth (21) for filtration is stretched,
Supplying compressed fluid into the compression chamber (13) formed in the filtration chamber (9),
Expanding the squeezing membrane (12) made of a filter cloth with lower air permeability than the filter cloth (21) and squeezing the dehydrated cake generated in the filtration chamber (9),
A method for operating a filter press, which comprises backwashing a dehydrated cake with a compressed fluid that passes through a pressing membrane (12) and a filter cloth (21).

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