JP2004141748A - Filtering device and filtering method using the device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filtering device which can surely strip a cake deposited on the surface of a filter element and a filtering method using the device. <P>SOLUTION: In the device which has a raw liquid cylinder 2 and a filter cylinder 3 arranged inside it at a prescribed distance from it, catches solids in treatment liquid on the surface of the filter cylinder 3, and discharges the filtrate through the filter cylinder 3, a double pipe 6 comprising an outside pipe 4 and an inside pipe 5 installed at a prescribed interval in the filter cylinder 3, a disk 8 having a slit 7 which is installed in the end part of the double pipe 6, and a cake stripping apparatus having a moving means for vertically moving the disk 8 together with the double pipe 6 along the inner surface of the filter cylinder 3, are provided. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a filtration device and a filtration method using the same, and more particularly, to a filtration device capable of easily separating and recovering solids in a liquid, in which cake can be easily separated, and a filtration method using the same.
[0002]
[Prior art]
As a conventional filtration device for separating and recovering a solid in a liquid, for example, the device shown in FIG. 6 is exemplified. In FIG. 6, the apparatus includes a tank 20 partitioned into an upper tank 20A and a lower tank 20B by a partition 21 and a cylindrical filter medium, for example, which is suspended from the opening 22 of the partition 21 into the lower tank 20B. A filter element 23 formed of a filter element or a sintered wire mesh coated with a filter aid layer on the surface, a liquid inlet 24 provided at the bottom of the lower tank 20B, and a processing liquid outlet 25 provided at the upper tank 20A. Having.
[0003]
In such an apparatus, the liquid to be treated introduced into the tank 20 from the liquid inlet 24 rises in the filtration element 23 as a clarified liquid after solids are captured on the surface of the filtration element 23, and the partition 21 is opened. It flows into the upper tank 20A through the hole 22 and is discharged out of the apparatus via the liquid outlet 25. When a predetermined amount of solid matter (hereinafter referred to as cake) accumulates on the surface of the filtration element 23, the introduction of the liquid to be treated is stopped, and the filtration element 23 is discharged through the liquid outlet 25 provided in the upper tank 20A. From the next side, for example, pressurized air is introduced, and the cake deposited on the surface of the filter element 23 is peeled off by the pressurized air. The peeled cake is drawn out of the device from the bottom of the lower tank 20B. After the cake peeling operation is completed, the liquid to be treated is introduced in the same manner as described above, and the same filtering operation is performed.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2000-32974
[Problems to be solved by the invention]
However, the conventional technique has a problem in that the cake adhered to the surface of the filtration element cannot be completely removed. That is, the peelability of the cake depends on its type, shape, size, and the like. As an example, in the process of manufacturing aluminum powder used in many industries, for example, in the operation of separating and recovering flaky aluminum powder dispersed in oil, since the cake adheres to the surface of the filtration element in a sheet form, filtration is performed. When pressurized air is introduced into the secondary side of the element to peel the cake, for example, when a thin part of the cake is peeled off and an air flow path is formed, purge air flows out from the peeled part thereafter So that it becomes impossible to peel off the cake in other portions.
[0005]
By the way, when coating the filter element surface with an auxiliary agent and peeling off the deposited cake together with the filter auxiliary agent, the cake can be efficiently peeled off.However, in the case where the solid matter filtered and collected is a product itself, etc. Often cannot use a filter aid. Also, in view of the current state of waste treatment in recent years, it is necessary to minimize the amount of filter aid used as waste. Therefore, there has been a demand for the development of a high-efficiency filtration device and a filtration method capable of reliably separating a cake deposited on a filtration element without using a filter aid.
[0006]
The object of the present invention is to solve the above-mentioned problems of the prior art, and to surely peel off the cake deposited on the surface of the filtration element without using a filter aid regardless of the type, shape, and physical properties of the cake. It is an object of the present invention to provide a filtering device capable of separating and recovering a solid in a liquid efficiently and efficiently, and a filtering method using the same.
[0007]
[Means for Solving the Problems]
The invention claimed in the present application to solve the above problems is as follows.
(1) An undiluted liquid cylinder having an inlet for a liquid to be treated, and a filter cylinder provided in the undiluted liquid cylinder at a predetermined interval from the undiluted liquid cylinder, and solids in the liquid to be treated flowing from the inflow port Is trapped on the surface of the filter tube, and the filtrate is discharged to the outside through the filter tube. In the filter device, an outer pipe and an inner pipe are provided in the filter tube at predetermined intervals from the filter tube. A heavy pipe, a disc-shaped disc having a slit for fluid ejection, provided at the tip of the double pipe, and a moving means for moving the disc along with the double pipe along the inner surface of the filter tube. Having a cake peeling device having the same, flows between the filtration tube and the outer pipe of the double pipe toward the tip of the double pipe, flows into the inner pipe through the tip of the double pipe, and flows into the inner pipe. The flow path of filtrate flowing in the pipe in the opposite direction And flowing between the outer pipe and the inner pipe toward the disk-shaped disk, and forming a flow path of the injected fluid which is injected from the slit of the disk and impinges on the inner wall surface of the filter cylinder. Filtration device.
[0008]
(2) A liquid reservoir portion having an enlarged diameter is formed at an end of the filter tube, and a disk-shaped disk provided at a tip portion of the double tube is connected to the double tube within a range smaller than the inner diameter of the filter tube. The diameter of the outer pipe is larger than that of the outer pipe, and the gap between the filter tube and the outer pipe of the double pipe flows between the disc-shaped disk and the inner wall of the liquid reservoir, and passes through the end of the double pipe. The filtration device according to the above (1), wherein a part of a filtrate flow path flowing into the inner pipe is formed.
(3) The thickness from the fluid ejection slit of the disk-shaped disc provided at the tip of the double pipe to the tip of the disc is set to be smaller than the gap between the filtration tube and the outer pipe of the double pipe. The filtration device according to the above (1) or (2), wherein the filtration device is thickened. (4) The open ends of the stock tube and the filter tube are fixed to flanges each having an opening corresponding to the tube diameter, and the stock tube and the filter tube are relatively detachably fixed via the flange. The filtering device according to any one of the above (1) to (3), wherein
[0009]
(5) A filtration method using the filtration device according to any one of (1) to (4) above, wherein solids in the liquid to be treated flowing into the stock solution cylinder through the inflow port are removed from the surface of the filtration cylinder. A filtration step of discharging the filtrate to the outside of the system through the filtrate flow path, extracting the liquid to be treated remaining in the stock solution cylinder after the filtration step, and introducing a purge medium from the inlet of the liquid to be treated. A purging step of purging the inside of the stock tube and the filtrate flow path, extracting the filter tube after the purging step from the stock tube together with the cake peeling device, and attaching the stock tube to a cake collection box; After the step, the jet fluid is jetted toward the inner wall surface of the filter cylinder through the flow path of the jet fluid of the cake stripper, and the moving means moves the disc-shaped disk of the cake stripper at a predetermined speed together with the double pipe. Move the filter A cake peeling step of peeling the cake adhered to the outer surface of the tube, and a filtration preparation step of attaching the filter tube after the cake peeling step to the stock solution tube together with the cake peeling device and preparing for the next filtration step. A characteristic filtration method.
(6) A series of filtration operations including the filtration step, the purge step, the unloading step, the cake stripping step, and the filtration preparation step are performed at predetermined time intervals using a plurality of filtration devices, and the filtration is always performed by any one of the devices. The filtration method according to the above (5), wherein the step is performed.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a main part of a filtration device according to one embodiment of the present invention, and FIGS. 2 to 5 are explanatory diagrams showing positional relationships between members in a filtration operation using the device of FIG. , FIG. 2 is a view showing a filtration step, FIG. 3 is a plan view of FIG. 2, FIG. 4 is a view showing a stock liquid tube extracting step, and FIG. 5 is a view showing a cake peeling step.
[0011]
In FIG. 1, this filtration device is a vertical type device, and a stock tube 2 having an inlet 1 for a liquid to be treated and a stock tube 2 provided in the stock tube 2 at predetermined intervals, for example, concentrically. And a filter tube 3 having an outer pipe 4 and an inner pipe 5 provided concentrically with the filter tube 3 at a predetermined interval, for example. A heavy pipe 6, a disk-shaped disc 8 having a slit 7 for fluid ejection provided at a tip end of the double pipe 6, and the disc 8 is attached to the double pipe 6 along the inner surface of the filter tube 3. A cake peeling device having moving means 9 (not shown, see FIG. 2) for moving the filter tube 3 between the filter tube 3 and the outer pipe 4 of the double tube 6 toward the tip of the double tube 6. And flows into the inner pipe 5 through the tip of the double pipe 6, The filtrate flows in the reverse direction through the inner pipe 5 and flows between the outer pipe 4 and the inner pipe 5 toward the disk 8, and is injected from the slit 7 of the disk 8 to The flow path 11 of the jet fluid that collides with the inner wall surface of the filter cylinder 3 is formed. The inner pipe 5 constituting the double pipe 6 extends slightly ahead of the outer pipe 4 and is in contact with the bottom inner wall of the liquid reservoir 19 provided so as to expand at the end of the filter tube. A notch 18, for example, a V-cut or an R-cut, for allowing the filtrate flowing between the filtration tube 3 and the outer pipe 4 of the double pipe to flow into the inner pipe 5 is provided at the tip. 2A is a flange fixed to the stock tube 2 and 3A is a flange fixed to the filtration tube 3.
[0012]
In FIG. 2, the moving means 9 of the cake peeling device includes, for example, a female screw 12 fixed to the upper end of the double pipe 6 via a member, a bar-shaped male screw 13 fitted to the female screw 12, and a male screw 13. And a driving device (motor) 14 for rotating the motor in both forward and reverse directions.
[0013]
In such a configuration, solids contained in the liquid to be treated, which are introduced into the undiluted liquid cylinder 2 under a pressurized state of, for example, 0.4 to 0.7 MPa through the inflow port 1 of the liquid to be treated, The filtrate is trapped and flows toward the distal end of the double pipe 6 with the filtrate flow path 10, that is, the gap between the filter tube 3 and the outer pipe 4 of the double pipe 6 as a downward flow, and flows toward the tip of the double pipe 6. It flows into the inner pipe 5 through the tip, flows in the opposite direction as the upward flow in the inner pipe 5 (see FIG. 1), and is discharged out of the apparatus via a piping not shown (see FIG. 1). Filtration step, FIG. 2). Next, the liquid to be treated remaining in the stock solution cylinder 2 after the filtration step is withdrawn through, for example, a short pipe provided at the lower part of the stock solution cylinder 2, and purged from the solution to be treated inlet 1. The medium, for example, pressurized air purges the inside of the stock tube 2 and the filtrate channel 10 (purge step). After the purging step, the filter tube 3 is removed from the stock tube 2 together with the cake peeling device 16 having the double tube 6, the disk 8, etc. (FIG. 4A), and is mounted on the cake collection box 15 (FIG. 4C, stock tube extraction). Process). After the stock liquid cylinder extracting step is completed, compressed air of, for example, 0.4 to 0.7 MPa is introduced as an ejection fluid into the ejection fluid flow path 11 between the outer pipe 4 and the inner pipe 5 of the cake peeling device. By rotating the motor 14 of the moving means 9 through the male screw 13 and the female screw 12 so as to eject the disc 8 of the cake peeling device 16 (see FIG. 1). ) Is reciprocated up and down several times together with the double pipe 6 at a predetermined speed, for example, 1 to 2 cm / sec, and the cake 17 adhered to the outer surface of the filter tube 3 by the compressed air (air knife) ejected from the slit 7. Peeled (cake peeling step, FIG. 5). After the peeled cake 17 is collected in the cake collection box 15, it is sent to the next step and used, for example, as a raw material, a product, or discarded. After the completion of the cake peeling step, the filter tube 3 is withdrawn from the cake collection box 15 and attached to the stock solution tube 2 together with the cake peeling device 16 to prepare for the next filtration step (filtration preparation step).
[0014]
According to the present embodiment, since the cake peeling device 16 having the fluid jet slit 7 that moves along the inner wall surface of the filter tube 3 is provided in the filter tube 3, the slit 7 of the cake peeling device 16 is provided. Since the air knife ejected from the collides with the entire inner wall surface of the filter tube 3, the cake 17 adhered to the outer surface of the filter tube 3 can be surely peeled off without requiring any manual operation. Therefore, work efficiency is improved, and labor costs can be greatly reduced as compared with the case where the cake is peeled off manually.
[0015]
In this embodiment, the case where the undiluted tube 2 and the filtration tube 3 and the double tube 6 composed of the filtration tube 3 and the outer pipe 4 and the inner pipe 5 are provided concentrically has been described. You can also.
In the present embodiment, the relative fixing between the stock tube 2 and the filter tube 3 is performed by detaching the flange 2A fixed to the stock tube 2 and the flange 3A fixed to the filter tube 3 by, for example, a hydraulic clamp. It is done by fastening. This facilitates the automation of the total filtration operation.
[0016]
In this embodiment, nitrogen gas, water vapor, or the like may be used instead of compressed air as the purge medium in the purge step.
In the present invention, the filtration device is preferably a vertical type, but may be a horizontal type or an inclined type inclined at a predetermined angle.
[0017]
In the present invention, the distance between the stock tube and the filter tube is not particularly limited, but is, for example, 10 to 20 mm when the outer diameter of the filter tube is 80 mmφ. As the filter tube, for example, a sintered wire mesh obtained by sintering a plurality of metal meshes is preferably used. The opening diameter, the opening ratio, and the like of the filtration tube are appropriately selected depending on the liquid to be treated, the solid to be collected, and the like.
In the present invention, the interval between the filter tube and the outer pipe of the double pipe as a part of the cake peeling device is, for example, 10 to 20 mm, the interval between the outer pipe and the inner pipe is, for example, 2 to 10 mm, and the inner pipe is The inner diameter is, for example, 20 to 50 mmφ, but is not particularly limited.
[0018]
In the present invention, the slit width of the fluid ejection slit provided on the disk-shaped disk as a part of the cake peeling device is, for example, 0.5 to 1.0 mm. If the slit width is too large, the effect of removing the cake by the air knife decreases, and if it is too small, the pressure loss increases and the running cost increases. As the ejection fluid ejected from the slit, for example, high-pressure air of 0.4 to 0.7 MPa is suitably used. As the injection fluid, for example, steam at 0.2 to 0.5 MPa, 110 to 130 ° C., or other fluid can be used.
[0019]
In the present invention, it is preferable to provide a liquid reservoir part whose diameter is larger than that of the filtration tube by, for example, 10 to 20 mm at the end of the filtration tube. In addition, it is preferable that the diameter of the disk-shaped disk provided at the end of the double pipe is larger than the outer pipe of the double pipe within a range smaller than the inner diameter of the filter tube. The gap between the filter tube and the outer pipe of the double pipe is, for example, 10 to 20 mm, and the relative gap between the disc-shaped disk and the filter tube is, for example, 1 to 2 mm, the disc-shaped disk and the The gap with the inner wall of the liquid reservoir is, for example, 20 to 30 mm. By providing a liquid reservoir portion larger in diameter than the filter tube and a disk-shaped disk having a diameter larger than the inner diameter of the filter tube, a gap between the filter tube and the outer pipe of the double tube is provided between the two. A part of the filtrate flow path flowing through the gap and flowing into the inner pipe through the notch provided at the end of the inner pipe of the double pipe is formed, and the flow direction of the filtrate flow path is smoothly changed. Can be done. In addition, this can prevent the filtrate from staying in the liquid reservoir.
[0020]
In the present invention, the thickness of the disk-shaped disk provided in the double pipe from the fluid injection slit to the tip of the disk is set to be larger than the gap between the filter tube and the outer pipe of the double pipe. Is preferred. Thereby, most of the fluid, for example, compressed air, injected from the slit of the disc-shaped disk penetrates from the inner surface of the filter tube to the outer surface without short-passing along the surface of the disk, and the cake is peeled off. Get involved. The thickness of the disc from the fluid ejection slit to the tip of the disc is, for example, 10 to 20 times the gap between the filter tube and the outer pipe of the double tube. If the thickness is insufficient, the jetting fluid tends to make a short path along the disk surface. On the other hand, if it is too thick, the width of movement of the slit becomes small, and a sufficient cake peeling effect cannot be obtained.
[0021]
In the present invention, the moving means of the cake peeling device is an elevating means in the case of a vertical device. As the moving means, for example, a means having a female screw, a male screw fitted to the female screw, and a driving device for rotating the male screw in the normal / reverse direction is preferably used, but is not particularly limited. As the type of the thread, for example, a ball screw or a trapezoidal screw is suitably used. The moving direction of the cake peeling device is a vertical direction in a vertical device, but is a horizontal direction in a horizontal device, for example.
[0022]
In the present invention, a series of filtration operations consisting of a filtration step, a purge step, a stock solution withdrawal step, a cake stripping step, and a filtration preparation step are performed using a plurality of filtration devices while being shifted by a predetermined time, for example, 1 to 2 hours. It is preferable that the filtration step is always performed by such an apparatus. Also, at this time, the number of necessary members can be omitted by sharing the filter cylinder, the cake peeling device, and / or the moving means of the cake peeling device with two or more devices.
[0023]
In the present invention, a series of filtration operations can be automatically controlled using a computer. The time required for the filtration step, the purging step, the unloading step, the cake stripping step, and the filtration preparation step in the filtration operation is not particularly limited.
In the present invention, when the solid matter in the liquid to be filtered, which is an object to be filtered, is a metal powder such as aluminum, for example, the filter tube is formed by dissolving only the metal powder without affecting the constituent material of the filter tube. It is preferable to perform regular cleaning with a suitable cleaning liquid.
[0024]
In the present invention, the filtration step is performed in a state where the disk-shaped disk of the cake peeling device is moved to the vicinity of the flange fixed end of the filter tube together with the double tube. It may be made to move between. Thereby, the pressure loss in the apparatus in the filtration step is reduced.
[0025]
【Example】
Next, specific examples of the present invention will be described. Using the apparatus of FIG. 2 using a sintered wire mesh having an opening diameter of several μm to several tens μm as a filtration cylinder, the inflow pressure of the liquid to be treated in the filtration step is 0.4 MPa, the inflow amount is 40 kg / hr, and the filtration time is 60 minutes, the purge air pressure in the purge step is 0.5 MPa, the purge air amount is 600 L / hr, the purge time is 30 minutes, the pressure of the compressed air as the injection fluid in the cake peeling step is 0.5 MPa, and the spraying (cake peeling) is performed. Assuming that the time is 5 minutes and the moving speed of the cake peeling device is 60 cm / min (two reciprocations), 5% by weight of scale-like aluminum peeling wear powder (thickness of several μm or less) having a particle size of several tens μmφ is contained. When the aluminum powder in oil having a temperature of 40 ° C. and a viscosity of 10 Pa · s was separated by filtration and collected, the aluminum powder was recovered at 1.6 kg / hr, and the recovery was 99%.
[0026]
【The invention's effect】
According to the invention described in claim 1 of the present application, the cake deposited on the surface of the filter cylinder can be reliably peeled off without requiring any manual operation, so that the solids in the liquid to be treated and / or the filtrate are efficiently separated. , Can be recovered. Further, since it is not necessary to use a filter aid and a filter medium, it is possible to avoid generation of impurities other than cake or waste.
[0027]
According to the invention described in claim 2 of the present application, in addition to the effects of the above invention, the flow and discharge of the filtrate can be performed smoothly.
According to the invention described in claim 3 of the present application, in addition to the effects of the above invention, the utilization efficiency of the jet fluid is improved, and the cake can be more reliably peeled.
[0028]
According to the invention described in claim 4 of the present application, in addition to the effects of the above-mentioned invention, the relative attachment and detachment of the stock tube and the filter tube becomes free, and complete automation can be promoted.
According to the invention as set forth in claim 5 of the present application, the cake deposited on the surface of the filter cylinder can be reliably peeled off without requiring any manual operation, so that the solids in the liquid to be treated and / or the filtrate are efficiently separated. , Can be recovered. Further, since it is not necessary to use a filter aid and a filter medium, it is possible to avoid generation of impurities other than cake or waste.
[0029]
According to the invention described in claim 6 of the present application, in addition to the effects of the above invention, the separation and recovery efficiency of the solid and / or the filtrate in the liquid to be treated is further improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a main part of a filtration device according to one embodiment of the present invention.
FIG. 2 is a diagram showing a relationship between members of a filtration device in a filtration step.
FIG. 3 is a plan view of FIG. 2;
FIG. 4 is a diagram showing a mutual relationship between members of a filtration device in a stock solution cylinder extracting step.
FIG. 5 is a diagram showing a relationship between members of a filtration device in a cake peeling step.
FIG. 6 is an explanatory view showing a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Inflow port of liquid to be processed 2 ... Undiluted liquid cylinder 2A ... Flange 3 ... Filtration cylinder 3A ... Flange 4 ... Outer pipe 5 ... Inner pipe 6 ... Double pipe 7 ... Slit 8 Disk 9; moving means 10; filtrate flow path 11; injection fluid flow path 12; female screw 13; male screw 14; motor 15: cake collection box 16: cake peeling device 17: cake 18 ... notch, 19 ... liquid reservoir, 20 ... tank, 20A ... upper tank, 20B ... lower tank, 21 ... partition, 22 ... opening, 23 ... filtration element, 24 ... liquid inlet, 25 ... liquid outlet.

Claims (6)

A source cylinder having an inlet for the liquid to be treated, and a filter cylinder provided in the source cylinder at a predetermined interval from the source cylinder, and the solid in the liquid to be treated flowing from the inlet is filtered by the filter. In a filtration device that captures on the surface of the tube and discharges the filtrate to the outside through the filter tube, the filter tube has a double tube including an outer pipe and an inner pipe each provided at a predetermined interval with the filter tube. A cake disc having a disk-shaped disc provided with a slit for fluid ejection provided at the tip of the double pipe, and a moving means for moving the disc along with the double pipe along the inner surface of the filter tube. A device is provided, flows between the filter tube and the outer pipe of the double pipe toward the tip of the double pipe, flows into the inner pipe via the tip of the double pipe, and flows through the inner pipe. Reverse flow path and front of filtrate A flow path of a jet fluid which flows between the outer pipe and the inner pipe toward the disk-shaped disk, is injected from the slit of the disk, and collides with the inner wall surface of the filter cylinder is formed. Filtration device. A liquid reservoir having an enlarged diameter is formed at an end of the filter tube, and a disc-shaped disk provided at the tip of the double tube is connected to an outer pipe of the double tube within a range smaller than the inner diameter of the filter tube. Larger than the diameter, and flows between the disc-shaped disk and the inner wall of the liquid reservoir through the gap between the filter tube and the outer pipe of the double pipe, and to the inner pipe via the end of the double pipe. 2. The filtering device according to claim 1, wherein a part of the inflow filtrate channel is formed. The thickness from the fluid ejection slit of the disk-shaped disc provided at the tip of the double pipe to the tip of the disc is made thicker than the gap between the filter tube and the outer pipe of the double pipe. The filtration device according to claim 1 or 2, wherein: The open ends of the stock tube and the filter tube are fixed to flanges each having an opening corresponding to the tube diameter, and the stock tube and the filter tube are relatively detachably fixed via the flange. The filtration device according to any one of claims 1 to 3, wherein A filtration method using the filtration device according to any one of claims 1 to 4, wherein solids in the liquid to be treated flowing into the undiluted liquid cylinder through the inflow port are captured on the surface of the filtration cylinder, and the filtrate is filtered. A filtration step of discharging the filtrate out of the system through the filtrate flow path, extracting the liquid to be processed remaining in the raw liquid cylinder after the filtration step, introducing a purge medium from the inlet of the liquid to be processed, and introducing a purge medium into the raw liquid cylinder. A purging step for purging the filtrate flow path, a filter cylinder after the purging step is withdrawn from the raw liquid cylinder together with the cake peeling device, and a raw liquid cylinder withdrawing step to be attached to a cake collection box; The ejection fluid is ejected toward the inner wall surface of the filter cylinder through the ejection fluid flow path of the above, and the moving means moves the disc-shaped disk of the cake peeling device together with the double pipe at a predetermined speed to perform the filtration. Outer surface of tube A filtering method, comprising: a cake peeling step of peeling off the attached cake; and a filtration preparation step in which a filter tube after the cake peeling step is attached to the stock tube together with the cake peeling device to prepare for the next filtration step. . A series of filtration operations including the filtration step, the purge step, the unloading step, the cake stripping step, and the filtration preparation step are performed at predetermined time intervals by using a plurality of filtration devices, and the filtration process is always performed by any one of the devices. The filtration method according to claim 5, wherein the filtration is performed.

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