JPH04271802A - Method for removing cake in filter - Google Patents

Abstract

PURPOSE:To make the cake discharged from a drain port free of a treated liq. and to eliminate the need for its dehydration in a filter consisting of a tank filter, a liq. reservoir and a filter cylinder by previously discharging a filtrate and the treated liq., and then discharging the cake which has been deposited on the filter cylinder and made into dryness. CONSTITUTION:A stop valve 12V is opened, and the air having a pressure higher than that of a treated liq. at an inlet 11 is introduced from a primary air port 12. A stop valve 14V is then opened, and the treated liq. in a tank filter 1 and the filtrate remaining in the filter cylinder 4 and liq. reservoir 2 are discharged from an outlet 14. Air is continuously supplied even after the treated liq., etc., are discharged, and the filter medium furnished in and around the tank filter 1 is completely dried or quasi-dried. The supply of air from the air port 12 is then stopped, a stop valve 16V is opened to supply air from a secondary air port 16, a stop valve 13V is opened, and the cake (dust and filter medium) dropped by the supply of air is discharged from a drain port 13.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a filter medium (filtration member) for a vertical cylindrical pressurized tubular filter used for filtering processing liquids such as plating processing liquids, dielectric processing processing liquids, and grinding processing liquids. The present invention relates to a method for removing filter slag to prevent clogging.

0002

[Prior Art] A vertical cylindrical pressurized tubular filter used for filtering processing liquids such as plating processing liquids, dielectric processing processing liquids, and grinding processing liquids has fibers on the outer peripheral surface of a cylindrical filter cloth. It has a filter cylinder surrounded by a filtering material such as diatomaceous earth, and by passing the processing liquid through this cylinder, dust, oil scale, etc. in the processing liquid are removed. As a method for removing dust that has become clogged in the filter medium due to repeated filtration, or filter medium that has become clogged with dust and has firmly adhered to it (i.e. filter slag), for example, remove the filter medium or filter cylinder from the filter machine. The primitive method of removing and cleaning the filter tube, or replacing it with a new filter tube was used. Recently, the following methods for removing filter dregs (or cleaning filter media) have been proposed.

(a) Japanese Unexamined Patent Publication No. 60-222117 discloses that a filter cylinder is immersed in a liquid tank having a drain port and an inflow port at the bottom, and the filter cylinder has an outer cylinder, an inside of the outer cylinder, and a filter. Using a filter structure consisting of a liquid reservoir at the top of an outer cylinder that communicates through a member and has an outlet for clean water, a gap is created between the outer cylinder and the inner surface of the liquid phase, and the inlet and flow are separated. At the same time as closing the outlet, the liquid tank and the filter tube are moved relative to each other in the direction of separation, so that the lower end of the outer cylinder exceeds the liquid level in the gap, causing the liquid in the liquid reservoir to rapidly fall into the liquid tank and filtering. A cleaning method for removing scum is disclosed.

(b) Japanese Unexamined Patent Publication No. 101216/1983 discloses that a liquid tank having a drain port and an inlet at the bottom is divided into a main tank chamber and a sub-tank chamber by vertical shielding plates, and the sub-tank A filtration machine that has an air vent inside the room, the lower end of the shield plate is below the filtration member, the main tank chamber and the sub-tank chamber communicate with each other below the filtration member, and the liquid level in the sub-tank chamber can be detected. Using,
The inlet and the outlet are closed, the air vent and the drain port are opened, and the liquid in the sub-tank is allowed to flow down.At the same time as a predetermined level of the liquid level is detected, the liquid in the liquid tank is pressurized to remove the liquid. descend rapidly,
A cleaning method for removing slag is disclosed.

(c) Japanese Patent Application Laid-Open No. 61-238311 discloses that a liquid tank having a drain port and an inlet at the bottom is divided into a main tank chamber and a sub-tank chamber by vertical shielding plates, and The tank chamber and the sub-tank chamber communicate with each other at the lower end of the partition wall, and the main tank chamber is provided with a filtration member that covers the outlet side, and the main tank chamber is provided with a filter for discharging the liquid in the liquid tank by opening a drain port. A filter is disclosed that includes means for synchronizing and pressurizing the liquid level on the main tank chamber side.

(d) Japanese Unexamined Patent Publication No. 61-242610 discloses that a filter medium such as a filter material or a cloth material is disposed around the outer circumferential surface of a tank provided with an inlet for processing liquid. Using a filter in which multiple filter cylinders are arranged in parallel, and the filter cylinders and the cleaning liquid outlet are communicated, the inlet and the outlet are shut off (closed), and the treated liquid in the tank is drained. , discloses a method for removing filter slag by communicating pressurized air to each liquid reservoir and dropping the cleaning liquid in the liquid reservoir downward from a filter member.

[0007] When performing the filtration operation again after the above-mentioned filter dregs are removed, it is common to attach and form a new filter medium on the filter cylinder as necessary to cover the missing amount, and then perform filtration.

[0008] That is, the above (a) JP-A-60-222
No. 117, (b) JP-A-61-101216, and (d) JP-A-61-242610 disclose that filter slag (filter material clogged with dust and etc.) from a filter medium, thereby removing filter slag. In (a) and (b), the filter slag is removed by dividing the filtration tank into a main tank chamber on the inside and a sub-tank chamber on the outside by partition walls, and passing air through the processing liquid in the sub-tank chamber. A method is used in which a certain amount of processing liquid is dropped in advance and the filtrate, etc. in the main tank chamber is dropped all at once using the gap formed. Although (d) is not divided into a main tank chamber and a sub-tank chamber, the process liquid in the filtration tank is first removed using a principle similar to the above, and the filtrate is dropped all at once by using the gap formed. method is used.

Furthermore, (c) the method disclosed in JP-A No. 61-238311 is to prevent clogging of the drain port by the filter material, and in this method, contrary to the above (a) and (b), By passing air through the filtrate in the tank chamber, a certain amount of the processing liquid is dropped first, and then using that gap to drop the processing liquid in the sub-tank chamber to agitate the liquid near the drain port, which prevents clogging of the drain port. prevent. Here, the filter dregs are removed by passing air through the filtrate and the like in the main tank chamber (ie, backwashing) as described above.

Among these methods (a) to (d), the filter dregs are removed by the method of passing air through the processing liquid in the main tank chamber (that is, backwashing), which is adopted in the above-mentioned publication (c). However, it is generally used because the equipment used is relatively small and the control is simple. however,
In the above method, the filtration tank is backwashed with a large amount of processing liquid, etc., so the filter slag (dust and dust-filled filter media) produced after washing is mixed with the processing liquid and becomes large. , this process will take a long time. Such mixtures are generally dehydrated using a filter. As described above, the problem of large amounts of filter dregs also exists in methods (a), (b), and (d).

[0011] Therefore, no matter which of the above methods for removing filter dregs is adopted, a large amount of waste liquid containing filter dregs is discharged from the drain port, which includes not only filter dregs but also treated liquid. Since it is necessary to treat a large amount of waste liquid and a dehydrator is required to dehydrate it, there is a problem that the entire apparatus becomes large and complicated.

0012

[Problems to be Solved by the Invention] The present invention provides a method for removing slag from a filtration device in which the slag discharged from the drain port during the sludge removal operation does not contain processing liquid and does not require dehydration. The purpose is to Further, the present invention provides a simple method for removing filter slag from a filtration device, in which the content of processing liquid contained in the slag discharged from the drain port during the sludge removal operation is small, and the dewatering of the slag is easy. purpose.

[0013]

[Means for Solving the Problems] The above object is to provide a filter tank, a liquid reservoir provided above the filter tank, and a lower opening of the liquid tank so as to communicate the filter tank and the liquid tank. In addition, the removal of filter slag formed on the filter tube of a filter device consisting of one or more filter tubes with filter media disposed around the outer circumferential surface is performed using (1)
) Stop the inflow of the processing liquid from the processing liquid tank, and introduce air from the side wall of the filter tank with a pressure at least equivalent to the pressure inside the filter cylinder so that the filter slag formed in the filter cylinder during the filtration operation does not come off. (2) discharging the filtrate in the filtration cylinder and the liquid reservoir, and the treated liquid in the filtration tank while supplying air; (3) by continuously supplying air, the filtrate and (4) supplying air from the side wall of the liquid reservoir to carry out filtration; This can be achieved by a method for removing filter dregs from a filtration device, which is characterized by a step of discharging filter dregs adhering to a cylinder.

[0014] Preferred embodiments of the method for removing filter dregs from the filtration device of the present invention are as follows.

1) A method for removing slag from the filtration device described above, characterized in that in the step of introducing air in the above (1), the liquid reservoir side is also placed in a ventilated state.

2) A method for removing slag from the filtration device described above, characterized in that the liquid reservoir is provided with a filtrate outlet and the supplied air is discharged.

3) The above filtration characterized in that the liquid reservoir is provided with an outlet for the filtrate, and after most of the filtrate has flowed out from the outlet, the process proceeds to the step (2) of discharging the treated solution and the filtrate. How to remove slag from the device.

4) A method for removing slag from the above-mentioned filtration device, characterized in that in the step of discharging the treated liquid and filtrate in the above (2), the liquid reservoir side is also kept in an aerated state.

5) A method for removing slag from the filtration device, characterized in that a discharge port is provided at the bottom of the filtration tank, and the treated liquid and filtrate of (2) above are discharged using this discharge port.

6) The above method characterized in that in the step of discharging the filter dregs from the filter cylinder in the above (4), air is supplied from the liquid reservoir side after the air supply from the side wall of the filter tank is stopped. Method for removing slag from a filtration device.

7) In the step of discharging the filter slag from the filter cylinder in (4) above, air is supplied from the side wall of the liquid reservoir after the air supply from the filtration tank side is stopped, and the filter slag is filtered. A method for removing filter slag from a filtration device as described above, characterized in that air is again supplied from the filtration tank side after the slag has fallen to the bottom of the tank.

[0022] Also, the above object is to provide a filtration tank, a liquid reservoir provided above the filtration tank, and a filter medium provided at the bottom opening of the liquid reservoir so as to communicate with the filtration tank and the liquid reservoir. Removal of filter slag formed on the filtration cylinder of a filtration device, which consists of one or more filtration cylinders installed around the surface, is carried out by (1) stopping the inflow of the processing liquid and removing the slag formed on the filtration cylinder by the filtration operation. a step of introducing air having a pressure at least equivalent to the pressure inside the filter cylinder from the filter tank side so that the filter slag does not separate;
(2) A process in which most of the filtrate in the filtration cylinder and the liquid reservoir and the treated liquid in the filtration tank are discharged while supplying air, leaving a small amount at the bottom of the filtration tank; (3) Processing in the filtration tank; (4) a step of bringing the filter medium and filter slag surrounding the filter cylinder into a dry or semi-dry state without a liquid phase by continuously supplying air while the liquid and filtrate remain; This can also be achieved by a method for removing slag from a filtration device, which is characterized by a step of supplying air from the side to cause the slag in the filter cylinder to fall, mixing the sludge with the treatment liquid, and discharging the mixture. can.

Preferred embodiments of the method for removing filter dregs from the filtration apparatus of the present invention are as follows.

1) A method for removing slag from the filtration device described above, characterized in that in the step of introducing air in the above (1), the liquid reservoir side is also placed in a ventilated state.

2) A method for removing slag from a filtration device as described above, characterized in that in the step of discharging the treated liquid and filtrate in the above (2), the liquid reservoir side is also kept in an aerated state.

3) A method for removing slag from the filtration device described above, characterized in that the liquid reservoir is provided with an outlet for the filtrate, and a part of the air supply is discharged from the outlet.

4) A method for removing slag from the above-mentioned filtration device, characterized in that a discharge port is provided at the bottom of the filtration tank, and the treated liquid and filtrate of the above (2) are discharged using the discharge port.

5) In the step of discharging the mixture of filter dregs and treated liquid from the filter cylinder in (4) above, supplying air from the liquid reservoir side is carried out after stopping the supply of air from the filter tank side. A method for removing slag from the above-mentioned filtration device.

6) In the step of discharging the mixture of filter dregs and treated liquid from the filter cylinder in (4) above, supplying air from the liquid reservoir side is carried out after stopping the supply of air from the filter tank side. . A method for removing slag from a filtration device as described above, characterized in that air is supplied from the filtration tank side again after the slag falls to the lower part of the filtration tank.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the attached FIGS. 1 to 5. FIG. 1 shows a cross-sectional view of a filtration device having a basic configuration consisting of a filtration tank 1, a liquid reservoir 2 provided above the filtration tank 1, and a filtration cylinder 4 around which a filter medium is provided so as to communicate these. The liquid reservoir 2 is fixed to the upper part of the filtration tank 1 via a lid plate 6 having an opening 3. The filtration tank 1 is provided with an inlet 11 for a processing liquid introduced from a processing liquid tank (not shown) and a primary air supply port 12 on the side wall, and a drain port 13 and an outlet 14 for the processing liquid at the lower part. ing. The processing liquid inlet 11 is an on-off valve 11V,
The primary side air supply port 12 has an on-off valve 12V, and a drain port 1
3 is the on-off valve 13V, and the processing liquid discharge port 14 is the on-off valve 1
Each is equipped with 4V. The liquid reservoir 2 is provided with a filtrate outlet 15 and a secondary air port 16 on the wall surface. The filtrate outlet 15 has an on-off valve 15V and a secondary air port 1.
6 is equipped with an on-off valve of 16V. A filter cylinder 4 with a filter material surrounding the outer circumferential surface is provided at the lower opening 3 of the liquid reservoir 2 (that is, corresponding to the opening 3 of the lid plate 6) so as to communicate the filter tank 1 and the liquid reservoir 2. It is being A plurality of filter cylinders may be used for efficient filtration. A filter tube is generally a filter cloth coated with a filtering material such as a fiber material, cloth material, diatomaceous earth, or the like. In the present invention, the term "filter medium" refers to filter cloth and filtration materials such as fiber materials, cloth materials, and diatomaceous earth. A filtration tank 1 is filled with a processing liquid, and a liquid reservoir 2 and a filter cylinder 4 are filled with filtered processing liquid.

FIG. 2 shows an enlarged sectional view of the filter tube 4 coated with the above-mentioned filter material. The filter tube has a structure in which the outer peripheral surface of a cylindrical filter cloth 21 is covered with diatomaceous earth 22, and a spring 23 is fixed horizontally to the inner wall of the filter tube. Although the spring may not be provided, it is preferable that the spring be installed, since it facilitates the removal of filter slag (dust, filter material). The spring is generally made of stainless steel, has a length generally in the range of 300 to 2000 mm, and a spring diameter generally in the range of 10 to 100 mm.

Filtration of the treated liquid using the above-mentioned filtration device is carried out as follows. First, before filtering the treatment liquid,
Usually, the filter cylinder 4 is coated with a filter aid as follows.

[0033] Opening/closing valve 13V of drain port 13 of filtration tank 1
, switch the pipe line to a tank (not shown) for filter aid (diatomaceous earth, etc.) dispersion liquid, and transfer the filter aid dispersion liquid to the on-off valve 11.
V is opened and the processing liquid is introduced into the filtration tank 1 from the inlet 11 by the pump. The dispersion liquid passes through the filter tube 4 while adhering diatomaceous earth to the outer periphery of the filter tube 4 (still in the state of a filter cloth in this case), and is discharged from the filtrate outlet 14. Then, this dispersion liquid is passed through the filter cylinder 4 via the circulation path again. In this way, a desired amount of diatomaceous earth is attached to the outer periphery of the filter cylinder 4.

Next, the treatment liquid is filtered as follows. The pipe line is switched to a treatment liquid tank (not shown), and the treatment liquid is introduced into the filtration tank 1 from the treatment liquid inlet 11 by opening the on-off valve 11V and using a pump. The treatment liquid passes through the filter cylinder 4 to which diatomaceous earth is sufficiently adhered to the outer periphery, and flows out from the filtrate outlet 14. As a result, the processing liquid is filtered to remove dust and the like, and the dust and the like are adsorbed by the filter aid on the outer periphery of the filter cylinder 4 . During this process, the on-off valve 12V of the primary air supply port 12, the on-off valve 13V of the drain port 13, and the on-off valve 16V of the secondary air port 16 are generally kept closed.

As the above-mentioned filtration process continues for a long time, dust and the like accumulate on the filter cloth of the filter tube 4 and on the diatomaceous earth and fibers attached to its outer circumference, causing clogging. Therefore, when the pressure for supplying the processing liquid at the processing liquid inlet 11 reaches a predetermined value (for example, 3 kg·f/cm<2>), the filter slag of the filtration apparatus of the present invention is removed.

The cleaning of the filter medium of the filter device shown in FIG. 1 is carried out, for example, as follows. (1) While the on-off valve 15V on the filtrate outlet 15 remains open, the on-off valve 11V on the inlet 11 is closed to stop the inflow of the processing liquid. Next, the on-off valve 12V of the primary air port is opened to apply air at a pressure higher than the liquid pressure of the processing liquid at the inlet 11 from the primary air port 12. Here, part or most of the filtrate is discharged from the outlet while preventing the filter material such as diatomaceous earth from falling off.

(2) While continuing to supply air from the primary side air port 12, open and close the on-off valve 14V of the processing liquid discharge port 14.
The processing liquid in the filtration tank 1 and the filtrate remaining in the filtration cylinder 4 and the liquid reservoir 2 are discharged from the outlet 14. At this time, it is preferable for the on-off valve 15V of the filtrate outlet 15 to remain open because the discharge can be carried out smoothly. FIG. 3 shows a state in which the processing liquid is being discharged from the discharge port. 7 is
Indicates the liquid level, which is the position of the surface of the processing liquid. Air from the primary side air port 12 passes through the filter tube 4 and accumulates in the upper part of the liquid reservoir 2, and not only the processing liquid but also the inside of the filter tube 4 that did not flow out in the step (1) above and the liquid reservoir. The filtrate in 2 is discharged from the processing liquid discharge port 14. This discharged processing liquid hardly contains dust, diatomaceous earth, fibers (filter material), or filter cloth materials. This is the primary air port 1
This is because the air supply from 2 prevents dust and filter media from falling off from the filter cylinder 4. The processing liquid and the like discharged from the processing liquid discharge port 14 are returned to the processing liquid tank and filtered again.

(3) By continuing to supply air continuously from the primary air port 12 even after the processing liquid, etc. is discharged, the inside of the filtration tank and the surrounding filter medium are kept in a dry or semi-dry state with no liquid phase. Make it. The processing liquid must be water or a liquid with a boiling point similar to that of water, and the medium must be non-adhesive so that a non-adhesive solid can be obtained as the filtrate. Easy and preferable. Therefore, if the resulting filter cake is sticky (for example, contains a large amount of oily components), it is preferable to use the filter cake removal method described below.

(4) Stop the supply of air from the primary air port 12, open the on-off valve 16V of the secondary air port 16 to supply air, open the drain port 4, and close the on-off valve 16V. 16V is opened and the filter slag (dust and filter material) that has fallen due to the application of air is discharged from the drain port. FIG. 4 shows a state in which the fallen filter dregs are discharged from the drain port. 8 shows the filter slag that has fallen to the bottom of the filter tank. In this way, the dried filter cake can be better discharged from the drain port.

(5) By continuing or stopping the air supply from the secondary air port and adding air from the primary air port 12, the filter slag that was not discharged in the step (4) is removed from the drain. Discharge from 4. (4)
If the process discharges filter cake, there is no need to perform this step.

On the other hand, if the treatment liquid is mainly composed of oily components, for example, it is difficult to completely dry the filter medium, and the filter slag (filter medium and dust) tends to become sticky (mushy). In that case, it is preferable to leave an appropriate amount of the treatment liquid at the bottom of the filtration tank in step (3) above without completely draining it, and then move on to steps (6) to (8) below.

(6) After the processing liquid etc. are discharged, by continuing to supply air from the primary side air port 12 without interruption,
The surrounding filter medium is brought to a semi-dry state with almost no liquid phase.

(7) Stop the supply of air from the primary air port 12, open the on-off valve 16V of the secondary air port 16 to supply air, and open the drain port 4 and close the on-off valve 16V. 16V is opened, the filter dregs are dropped by applying air, and the filter dregs and the processing liquid left at the bottom of the filtration tank are mixed and discharged from the drain. FIG. 5 is a diagram showing a state in which the filter dregs and the processing liquid left at the bottom of the filtration tank are mixed and discharged from the drain. 8 shows a mixture of filter cake and treatment liquid.

(8) By continuing or stopping the air supply from the secondary air port 16 and adding air from the primary air port 12, the filter medium and processing liquid that were not discharged in the step (4) can be removed. is discharged from the drain 4.

[0045] In this way, the slag removal of the present invention can be carried out.

The method for removing slag from a filtration device according to the present invention is not limited to the filtration device having the structure shown in FIG. If so, the removal method of the present invention can be used.

[0047]

Effect of the invention: A filter medium (
The cleaning method for the filter media in a filtration device (so-called vertical cylindrical pressurized tubular filter), which has a basic configuration consisting of a filtration cylinder surrounded by a filtration material (filtering material such as fibers or diatomaceous earth), is to blow air from the filtrate side. In the present invention, the filtrate and the treated liquid are first discharged, and then the filter material, which is the filter residue, is dried or semi-dry and then discharged.

[0048] As a result, the discharged filter slag (dust and dust-filled filter media) is not or hardly mixed with the processing liquid, so the amount of filter slag obtained is small. . Further, if the filter cake is not mixed with the treatment liquid, there is no need to dehydrate the filter cake, and even if the filter cake is mixed with the treatment liquid, the amount thereof is extremely small and even if it is dehydrated, it can be carried out in a very short time. Therefore, by using the slag removal method of the filter medium of the present invention, filtration can be performed efficiently. Furthermore, if this removal method is used, a dehydrator can be made unnecessary, so the entire device including the filter can be made small and simple.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a filtration device having a basic configuration consisting of a filtration tank, a liquid reservoir provided above the filtration tank, and a filtration cylinder provided around the periphery to communicate these.
FIG. 2 is a diagram for explaining one embodiment of a method for removing filter dregs from a filtration device of the present invention.

FIG. 2 is an enlarged sectional view of the filter tube 4 coated with the filter material of FIG. 1 above.

FIG. 3 is a diagram showing a state in the middle of discharging the processing liquid in one embodiment of the above-mentioned filter dregs removal method.

FIG. 4 is a diagram showing a state in which the fallen filter dregs are discharged from the drain port in the step following FIG. 3 in one embodiment of the above-mentioned filter dregs removal method.

FIG. 5 shows another embodiment of the filter slag removal method shown in FIGS. 1 to 4 above, in which the filter dregs and the treated liquid left at the bottom of the filtration tank are mixed using the filtration device shown in FIG. 1. FIG.

[Explanation of symbols]

1 Filtration tank 2 Liquid reservoir 4 Filter cylinder 6 Lid plate 11 Processing liquid inlet 11 12 Primary side air port 13 Drain port 13 14 Processing liquid outlet 15 Outlet 16 Secondary air port

Claims (2)

[Claims] [Claim 1] A filtration tank, a liquid reservoir provided above the filtration tank,
and a filtration cylinder of a filtration device, which is provided at a lower opening of the liquid reservoir so as to communicate the filtration tank and the liquid reservoir, and includes one or more filter cylinders with a filter medium disposed around the outer peripheral surface. (1) Stop the flow of the processing liquid from the processing liquid tank, and reduce the pressure inside the filter cylinder at least so that the filter slag formed in the filter cylinder by the filtration operation does not come off. a step of introducing air having the same pressure from the side wall of the filtration tank; (2) a step of discharging the filtrate in the filtration cylinder and the liquid reservoir and the treated liquid in the filtration tank while supplying air;
3) A step in which the filtrate and the treated liquid are discharged by continuously supplying air to bring the inside of the filtration tank, the filter media and filter slag surrounding the filtration tube into a dry or semi-dry state without a liquid phase, and (4) A method for removing filter slag from a filtration device, characterized by carrying out the step of supplying air from the side wall of the liquid reservoir and discharging the filter slag adhering to the filter cylinder. 2. A filter medium is provided around the outer peripheral surface of a filtration tank, a liquid reservoir provided above the filtration tank, and a lower opening of the liquid reservoir so as to communicate the filtration tank and the liquid reservoir. (1) Stop the inflow of the processing liquid and remove the slag formed on the filter cylinders by the filtration operation. A step of introducing air having a pressure at least equivalent to the pressure inside the filtration cylinder from the filtration tank side to prevent separation, (2) While supplying air, the filtrate in the filtration cylinder and the liquid reservoir, and the filtrate in the filtration tank. (3) With the processing liquid and filtrate remaining in the filtration tank, by continuing to supply air without interruption, the process of discharging most of the processing liquid, leaving a small amount at the bottom of the filtration tank. (4) supplying air from the liquid reservoir side to drop the filter slag in the filter cylinder, and mixing the filter slag with the treatment liquid; 1. A method for removing slag from a filtration device, the method comprising: removing slag from a filtration device;