JP2010115719A - Method and device for oscillating filtration - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable automatic recovery of filtrating performance and filtration stable for a long time in a method for oscillating filtration. <P>SOLUTION: In this method for oscillating filtration, a liquid 3 to be filtrated is supplied to an oscillated filter, and a layer of suspended particles is formed on the filter 7 by crossflow, thereby achieving separation between a filtrate 14 and an overflow liquid 16 with particles condensed. The outflow of the overflow liquid 16 is reduced, and a pressure difference in the filter 7 is adjusted, thereby stably forming the layer of the suspended particles to perform filtration. When the filtrating performance of the filter 7 is deteriorated, the outflow of the overflow liquid 16 is released to flush away the layer of the suspended particles. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vibration filtration method and apparatus that automatically recovers filtration performance and enables stable filtration for a long period of time.

  For example, to manufacture a silicon semiconductor wafer, a slicing process for slicing a single crystal ingot to obtain a thin disk-shaped wafer, a chamfering process for preventing wafer chipping and cracking, and finish polishing of the chamfered part and the wafer surface There are a number of processing steps such as a polishing step, and waste slurry is generated in such a wafer processing step. In particular, in the slicing process of slicing a single crystal ingot, cutting is performed while applying a cutting fluid in which abrasive grains are mixed with coolant to the wire of a wire saw. Therefore, the waste slurry is composed of abrasive grains, pieces of abrasive grains, silicon The cutting waste is mixed with the coolant.

  Here, the waste slurry is regenerated and reused from the viewpoints of economic reasons and waste volume reduction. That is, waste slurry is separated into abrasive grains, coolant, and impurities such as silicon cuttings, and after adjusting conditions such as pH, the abrasive grains and coolant are mixed with new coolant and new abrasive grains as necessary. It is used again for processing steps such as cutting and polishing.

  Since the waste slurry generated in the wafer processing step has a relatively high viscosity in which fine particles are mixed at a high concentration, it is difficult to separate and recover the abrasive grains and the coolant with high efficiency. .

  In the separation and recovery of the waste slurry, there are two centrifugal separators in which the abrasive particles are recovered in the first-stage centrifuge and the coolant is recovered in the second-stage centrifuge. (See Patent Document 1).

  However, about 10% by weight of impurities (mainly silicon cuttings) are present in the coolant recovered by the second-stage centrifuge, so that the coolant from the second-stage centrifuge When trying to recover the entire amount, the amount of impurities in the regenerated cutting fluid becomes excessive and the cutting performance deteriorates. Therefore, only 30 to 50% of the coolant is recovered and reused, and the remaining coolant Is currently disposed of.

  Accordingly, it is desired to increase the coolant recovery rate and reduce the amount of waste, but there is a membrane filtration method as a method for reliably separating the coolant (see Patent Document 2). The membrane filtration method has the advantage that even fine particles can be reliably separated by selecting a filtration membrane, but the filtration membrane is easily clogged. Does not recover, and there is a problem that the life is short. Therefore, the membrane filtration method is used when filtering a few impurities on the order of ppm, and it is used for the treatment of impurities containing around 10% by weight of impurities such as the coolant recovered by the second-stage centrifuge. Is not applicable.

  Moreover, there exists a cake filtration system conventionally (refer patent document 3). In the cake filtration method, the solid particles in the liquid to be filtered are trapped by the filter so that the cake can serve as a filter. The cake filtration method separates even if the concentration of mixed solid particles is relatively high. Can do. However, in the case of the coolant from the second-stage centrifuge, there is a problem that effective filtration is difficult because the cake is difficult to be formed stably.

  In the waste slurry from the silicon processing step, as shown in the particle size distribution diagram of the solid particles in FIG. 7, the abrasive grains (large particle size) and the silicon cutting waste (small particle size) have two peak points P1, A two-point peak distribution A having P2 is obtained. Then, the abrasive particles are removed by aiming at the first peak point P1 with the first-stage centrifuge, and then silicon scraps are aimed at the second peak point P2 with the second-stage centrifuge. Try to remove. The coolant after being processed in the centrifuge in this way is different from the two peak points P1 and P2, but the two-point peak distribution B having the two peak points P1 ′ and P2 ′ still remains. It has become.

  In the case of the cake filtration method, in the case of one having a single peak point in which the particle diameters of the solid particles are relatively uniform, it is large by performing an appropriate flow path between the particles as shown in FIG. A thick cake is formed and good filtration is performed. As shown in FIG. 7, in the case of a two-point peak distribution coolant having two peak points P1 ′ and P2 ′, fine particles are filtered at an early stage. There is a problem that the separation of the large-diameter particles thereafter does not proceed in order to deposit on the channel and cover the flow path, so that a cake having a large thickness cannot be formed and good filtration is not performed.

  On the other hand, as a method for completely separating the solid particles contained in the coolant, there is a distillation method in which the particles are separated by evaporation and condensation. However, this distillation method has a problem that the coolant has a low boiling point and is flammable and low in toxicity, such as propylene glycol as a main component. Since the distillation method is a recovery process by evaporation and condensation, for example, when a coolant having a high boiling point, flammability, and toxicity is used, treatment at a high temperature and safety measures are required, and the equipment cost and heating fuel cost are reduced. There is a problem of increasing. In recent years, the coolant is shifting from oily to aqueous, and among the aqueous coolants, it has been studied to use diethylene glycol, which is cheaper than propylene glycol, or polyethylene glycol (PEG 200 or the like) whose viscosity is stable. However, since these all have high boiling points or thermal decomposability, their application in the distillation system is limited.

  Further, in recent years, as a separation method that can solve the above-mentioned conventional problems, a filtrate to be filtered is supplied to a vibrating filter, and a filtrate and an overflow liquid in which particles are concentrated in a state where a floating particle layer is formed on the filter. A vibration separation system using a cross flow that separates into two is proposed (see Patent Document 4).

In this vibration separation system, a suspended particle layer that floats away from the filter is formed, and the particles in the suspended particle layer vibrate, so that the filter is less likely to be clogged and stable filtration can be performed. .
JP 2001-277115 A JP 2001-015465 A Japanese Patent Laid-Open No. 08-294606 Special table 2002-509014 gazette

  However, even in the vibration separation system shown in Patent Document 4, when filtering a liquid to be filtered having a high viscosity like the coolant, the layer thickness of the suspended particle layer formed on the filter gradually increases when the filtration is continued. Thus, there is a problem that the filter performance is lowered due to approach to the filter. Furthermore, when the vibration separation system is stopped, the suspended particle layer sticks to and adheres to the filter, and when the operation is resumed, there is a problem that good filtration cannot be performed.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vibration filtration method and apparatus that automatically recovers the filtration performance and enables stable filtration over a long period of time.

  The present invention is a vibration filtration method for supplying a liquid to be filtered to a vibrated filter and separating the filtrate into a filtrate and an overflow liquid in which particles are concentrated, and acts on the filter by restricting the overflow of the overflow liquid. When the filtration of the suspended particle layer formed on the filter increases due to vibration and the filtration performance deteriorates due to vibration, the outflow of the overflow liquid is released to remove the suspended particle layer. The present invention relates to a vibration filtering method characterized by washing away.

  In the vibration filtration method, it is preferable to block the filtrate outflow when the overflow outflow is released.

  In the vibration filtration method, the filtration performance of the filter can be detected from the flow rate of the filtrate.

  In the vibration filtration method, the filtration performance of the filter can be detected from the supply pressure of the liquid to be filtered when the liquid to be filtered is quantitatively supplied by a metering pump.

  In the vibration filtration method, it is preferable that the liquid to be filtered is heated to a temperature equal to or higher than the inflection point at which the viscosity of the liquid to be filtered changes from a high viscosity to a low viscosity.

  In the vibration filtering method, the liquid to be filtered may be a waste slurry having a two-point peak distribution in which silicon cutting waste and abrasive grains generated in the silicon processing step are mixed in the coolant.

  In the vibration filtration method, it is preferable to release the overflow of the overflow liquid to wash away the suspended particle layer before stopping the vibration filtration, and then stop the vibration filtration.

The present invention includes a supply pump for supplying a liquid to be filtered,
A vibrating filter that separates the filtrate from the filtrate and the overflow liquid in which the particles are concentrated by the suspended particle layer that is supplied to the vibrating filter from the supply pump and formed on the filter;
A switching valve provided in the outflow channel of the overflow liquid;
An adjustment flow path connected to the switching valve via a throttle valve;
An open channel connected to the switching valve;
Filtration performance detecting means for detecting filtration performance by a filter;
A switching controller that switches a switching valve so as to open the overflow liquid to an open flow path when the filtration performance detected by the filtration performance detection means falls below a set value;
The present invention relates to a vibration filtering device characterized by comprising:

  In the vibration filtering device, it is preferable to have a shut-off valve that shuts out the filtrate when the overflow liquid is opened to the open channel.

  In the vibration filtering device, the filtration performance detecting means may be a flow meter for detecting the outflow flow rate of the filtrate.

  In the vibration filtering device, the filtration performance detecting means may be a pressure gauge that detects the supply pressure of the liquid to be filtered when the liquid to be filtered is supplied to the filter by a metering pump.

  In the vibration filtering device, it is preferable that the tank has a heater for heating the liquid to be filtered.

  In the vibration filtering device, it is preferable that the switching controller controls the switching valve so as to open the overflow liquid to the open flow path before stopping the vibration filtering.

  According to the vibration filtration method and apparatus of the present invention, by filtering out the overflow of the overflow liquid and adjusting the pressure acting on the filter, a stable suspended particle layer is formed on the filter, and filtration is performed. When the suspended particle layer thickness increases and the filtration performance decreases, the overflow of the overflow liquid is released and the suspended particle layer is washed away, so the filtration performance of the filter is automatically restored when the filtration performance declines Therefore, it is possible to achieve an excellent effect of performing stable filtration for a long time.

  When the liquid to be filtered is heated to a temperature above the inflection point at which the viscosity of the liquid to be filtered changes from a high viscosity to a low viscosity, the viscosity of the liquid to be filtered can be lowered to increase the filtration efficiency and the viscosity is stabilized. This has the effect of stabilizing the formation of the suspended particle layer.

  Even if the liquid to be filtered is a waste slurry having a two-point peak distribution in which silicon chips and abrasive grains generated in the silicon processing process are mixed in the coolant, an effect of performing stable filtration by automatically washing away the suspended particle layer There is.

  Before stopping the vibration filtration, the flow of the overflow liquid is released to wash away the suspended particle layer, and then the vibration filtration is stopped to prevent the problem that the suspended particle layer adheres to the filter and stops the operation. It has the effect of performing good filtration when

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a flowchart showing an example of an outline of a vibration filtering device according to the present invention. In FIG. 1, 1 is a vibration filter, 2 is a tank in which a liquid to be filtered 3 is accommodated, and 4 is a supply pump for supplying the liquid to be filtered 3 in the tank 2 to the vibration filter 1 through a supply flow path 5. is there.

  In the vibration filter 1, a plurality of disk-shaped filters 7 are accommodated in a cylindrical container 6, and the filter 7 vibrates when the container 6 is reciprocally rotated by a drive motor 8. It has become. A filtrate outflow channel 9 is formed at the center of the filter 7 in the diameter direction, while a filtrate to be filtered 3 from the supply pump 4 is introduced to one side in the diameter direction passing through the filtrate outflow channel 9. An introduction flow path 10 is provided, and an overflow liquid flow path 11 is provided on the other side in the diameter direction passing through the filtrate outflow flow path 9.

  FIG. 2 shows the filtration structure of the filter 7 in the vibration filter 1. The two filters 7 with a distance 7a are formed in one unit 12, and this unit 12 has a required distance 13. Thus, a plurality of layers are stacked. Then, the filtrate 3 introduced from the filtrate introduction flow path 10 is guided to the upper and lower outer surfaces of the unit 12 through the interval 13, and the filtrate 14 passes through each filter 7 as shown by broken lines by cross flow. The filtrate 14 flows out into the filtrate outflow passage 9 from the interval 7a. At this time, since the filter 7 vibrates, a suspended particle layer 15 is formed on the outer surface of the filter 7 so as to float with a space from the outer surface of the filter 7 as shown in FIG. Accordingly, the liquid to be filtered 3 is filtered by the suspended particle layer 15. The liquid to be filtered 3 from which the filtrate 14 has been separated becomes an overflow liquid 16 in which particles are concentrated and flows out from the overflow liquid flow path 11.

  If the filtration is continued in the vibration filter 1, the thickness of the suspended floating particle layer 15 gradually increases, which causes a problem that the filtration performance is lowered. Furthermore, when the operation of the vibration filter 1 is stopped, the suspended particle layer 15 is stuck on the filter 7, and there is a problem that good filtration cannot be performed when the operation is resumed.

  For this reason, as shown in FIG. 1, a switching valve 18 (three-way switching valve) is provided in the outflow passage 17 through which the overflow liquid 16 flows, and the overflow liquid 16 is connected to the switching valve 18 via a throttle valve 19. Is connected to an adjustment flow path 20 that returns the liquid to the tank 2 and an open flow path 21 that opens the overflow liquid 16 to the tank 2 as it is.

  Further, in order to detect the filtration performance of the filter 7 in the vibration filter 1, a filtration performance detection means 24 using a flow meter 23 is provided in the outflow passage 22 of the filtrate 14. As the filtration performance detection means 24, when the supply pump 4 is a metering pump, a pressure gauge 25 is provided in the supply flow path 5 to detect the supply pressure of the liquid 3 to be filtered supplied to the filter 7. May be.

  Then, switching control for controlling switching of the switching valve 18 so that the overflow liquid 16 is opened to the tank 2 by the open flow passage 21 when the filtration performance detected by the filtration performance detecting means 24 falls below a set value. A container 26 is provided.

  Further, in FIG. 1, a shutoff valve 27 is provided in the outflow passage 22 of the filtrate 14 so as to shut off the outflow of the filtrate 14 when the overflow liquid 16 is opened to the tank 2 through the open passage 21 as described above. Provided.

  The tank 2 is provided with a heater 28 for heating the liquid 3 to be filtered. The heater 28 is provided in the tank 2 and controls the heating by the controller 30 based on the temperature detected by the thermometer 29 that detects the temperature of the liquid 3 to be filtered. As shown in FIG. 4 and FIG. 5, the relationship between the temperature and viscosity of different types of filtered liquid 3 has different inflection points X at which the viscosity changes from high viscosity to low viscosity depending on the type. Therefore, the heated liquid 28 is heated by the heater 28 so that the temperature above the inflection point X is maintained according to the type of the liquid 3 to be filtered. Various systems such as an electric heater and hot water can be used for the heater 28 that heats the liquid 3 to be filtered, and the position for heating the liquid 3 to be filtered can be arbitrarily selected.

  Further, the switching controller 26 switches the switching valve 18 before the filtration by the vibration filter 1 is stopped to open the overflow liquid 16 to the open flow path 21. That is, when a stop command 31 is input to the switching controller 26, the switching controller 26 switches the switching valve 18 to open the overflow liquid 16 to the open flow path 21 and then stops the operation of the vibration filter 1. A command is issued.

  The operation of the above embodiment will be described below.

  In a state where the vibration filter 1 is reciprocally rotated by the drive motor 8 to vibrate the filter 7, the supply pump 4 is driven to supply the filtrate 3 to be filtered in the tank 2 via the supply channel 5. 10 and the throttle valve 19 provided in the outflow passage 17 for the overflow liquid 16 is throttled to a predetermined opening, so that the liquid 3 to be filtered is guided to the outer surfaces of the upper and lower filters 7 in the unit 12 at a required pressure. In addition, in a state where the suspended particle layer 15 is formed on the filter 7, the filtrate 14 of the liquid to be filtered 3 passes through the suspended particle layer 15 and the filter 7 and is filtered to flow out from the filtrate outflow passage 9. The liquid to be filtered 3 that has cross-flowed on the outer surface of the filter 7 is concentrated into the overflow liquid 16 from the overflow liquid flow path 11 to the outflow flow path 17.

  At this time, in order to filter the liquid 3 to be filtered with a high impurity concentration, the filter 7 is driven by the drive motor 8 at a frequency of about 40 to 70 Hz and about 1/2 inch to 1 inch (about 13 to 25 mm). It was found that good filtration can be performed by vibrating at an amplitude of. When filtering the liquid 3 to be filtered, which is a coolant mixed with about 10% by weight of impurities by the vibration filter 1, the filter 7 is vibrated at a frequency of 50 Hz and an amplitude of 3/4 inch (about 19 mm). In this case, a good suspended particle layer 15 was formed on the outer surface of the filter 7, and good filtration could be performed.

  However, even if the filtration is performed in a good state as described above, if the filtration is continued, the thickness of the suspended particle layer 15 gradually increases and approaches the filter 7. Filtration performance is reduced.

  When the filtration performance of the filter 7 decreases, the flow rate of the filtrate 14 flowing out from the outflow passage 22 gradually decreases, but the outflow flow rate of the filtrate 14 is detected by the filtration performance detection means 24 comprising the flow meter 23, Since the detected value is input to the switching controller 26, when the detected value of the performance by the filtration performance detecting means 24 falls below the set value, the switching controller 26 tanks the overflow liquid 16 through the open channel 21. The switching valve 18 is switched so as to open to 2.

  Then, the suspended particle layer 15 that has grown thick on the filter 7 is immediately washed away. At this time, by closing the shutoff valve 27 provided in the outflow passage 22 for the filtrate 14, all the liquid to be filtered 3 becomes the overflow liquid 16, so that the action of washing away the suspended particle layer 15 can be enhanced.

  Since the surface of the filter 7 from which the suspended particle layer 15 has been washed away is restored to a clean state, the switching controller 26 switches the switching valve 18 so that the overflow liquid 16 flows again to the adjustment flow path 20 having the throttle valve 19. Switch. As a result, the suspended particle layer 15 in a good state is again formed on the filter 7 and good filtration is performed.

  In the above, for example, the heater 28 provided in the tank 2 is heated to a temperature equal to or higher than the inflection point X at which the viscosity of the liquid to be filtered 3 changes from the high viscosity to the low viscosity shown in FIGS. If it does in this way, while the viscosity of the to-be-filtered liquid 3 can be reduced and filtration efficiency can be improved, formation of the floating particle layer 15 can be stabilized by stabilizing a viscosity.

  When a stop command 31 is input to the switching controller 26, the switching controller 26 switches the switching valve 18 so as to open the overflow liquid 16 to the open flow path 21, and then issues a command to stop the operation of the vibration filter 1. Therefore, when the operation of the vibration filter 1 is stopped, the suspended particle layer 15 on the filter 7 is washed away. Therefore, when the vibration filter 1 is stopped, the suspended particle layer 15 adheres closely to the filter 7 and is restarted. It is possible to solve the problem that good filtration cannot be performed.

  FIG. 6 shows an example in which the present invention is applied to the filtration of waste slurry from a silicon processing step. In FIG. 6, 32 is a silicon processing device such as a wire saw, and 33 is waste from the silicon processing device 32. This is a first-stage centrifuge for separating the abrasive grains 35 by introducing the slurry 34, the separated abrasive grains 35 are guided to the preparation tank 36, and the filtrate 37 is guided to the filtrate tank 38. Reference numeral 39 denotes a second-stage centrifuge that introduces the filtrate 37 in the filtrate tank 38 and separates the filtrate 40. The separated filtrate 40 is guided to a receiving tank 41. The impurities 42 separated by the second-stage centrifuge 39 are discarded. The filtrate 40 of the receiving tank 41 is supplied to the tank 2 of FIG. 1 as the filtrate 3 and supplied to the vibration filter 1 by the supply pump 4 to effectively remove the particles 43 (filtrate 14). Is obtained. The obtained coolant 43 is guided to the preparation tank 36, and the abrasive grains 35, new abrasive grains, and new coolant are added to prepare the cutting fluid 44. The cutting fluid 44 is again applied to the silicon processing apparatus. 32. Since the impurities in the filtrate 40 in the tank 2 are gradually concentrated by the filtration, a part of the filtrate 40 in the tank 2 is taken out and separated into waste solids and coolant by distillation separation or the like. Accordingly, in the embodiment of FIG. 6, substantially the entire amount of coolant contained in the waste slurry 34 can be recovered and reused.

  The filtrate 40 separated in the second-stage centrifuge 39 of FIG. 6 has a two-point peak distribution B having two peak points P1 ′ and P2 ′ as shown in FIG. As shown in FIG. 3, it is filtered by the filter 1 by the suspended particle layer 15 formed on the filter 7, and when the thickness of the suspended particle layer 15 is increased and the filtration performance is lowered, the suspended particle layer is automatically Since 15 is washed away, the filtrate 40 (waste slurry) having the two-point peak distribution B that is difficult to separate can also be stably filtered.

  As described above, in the present invention, by filtering out the overflow liquid 16 and adjusting the pressure acting on the filter 7 to form a stable suspended particle layer 15 on the filter 7, the filtration is performed. When the layer thickness of the suspended particle layer 15 increases and the filtration performance deteriorates, the overflow of the overflow liquid 16 is released and the suspended particle layer 15 is washed away, so that the filtration performance of the filter 7 is automatically adjusted when the filtration performance is lowered. Recovery, and thus stable filtration is possible for a long time.

  In addition, this invention is not limited only to the said form, Of course, a various change can be added in the range which does not deviate from the summary of this invention.

It is a flowchart which shows an example of the outline of the vibration filtration apparatus in this invention. It is sectional drawing which shows the filtration structure of the filter in a vibration filter. It is explanatory drawing which shows the state in which the suspended particle layer is formed on the filter. It is a diagram which shows the relationship between the temperature of a to-be-filtered liquid, a viscosity, and an inflection point. It is a diagram which shows the relationship between the temperature of the to-be-filtered liquid different from FIG. 4, a viscosity, and an inflection point. It is a flowchart which shows an example at the time of applying this invention to filtration of the waste slurry from a silicon processing process. It is a particle size distribution figure of the solid particle in the waste slurry from the processing process of silicon. In cake filtration, it is a schematic diagram which shows the thickness of the cake in case it has one peak point with which the particle size of the solid particle was comparatively uniform. In cake filtration, it is a schematic diagram which shows the thickness of the cake in case the particle size of a solid particle has a two-point peak distribution which has two peak points.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vibration filter 3 Filtered liquid 4 Supply pump 7 Filter 14 Filtrate 15 Floating particle layer 16 Overflow liquid 17 Outflow flow path 18 Switching valve 19 Throttle valve 20 Adjustment flow path 21 Open flow path 23 Flowmeter 24 Filtration performance detection means 25 Pressure Total 26 Switching controller 27 Shut-off valve 28 Heater 32 Silicon processing device 34 Waste slurry 35 Abrasive grain 43 Coolant B 2-point peak distribution X Inflection point

Claims (13)

  A vibration filtration method in which a filtrate to be filtered is supplied to a vibrating filter and separated into a filtrate and an overflow liquid in which particles are concentrated by cross flow, and the pressure acting on the filter is adjusted by restricting the outflow of the overflow liquid. When the filtration performance deteriorates due to the increase in the thickness of the suspended particle layer formed on the filter due to vibration, the overflow of the overflow liquid is released to wash away the suspended particle layer. Vibration filtering method.   The vibration filtration method according to claim 1, wherein when the overflow of the overflow liquid is released, the filtrate is blocked from flowing out.   The vibration filtration method according to claim 1, wherein the filtration performance of the filter is detected from the outflow rate of the filtrate.   The vibration filtration method according to claim 1 or 2, wherein the filtration performance of the filter is detected from the supply pressure of the filtrate to be filtrated when the filtrate to be filtrated is quantitatively supplied by a metering pump.   The vibration filtration method according to claim 1, wherein the liquid to be filtered is heated to a temperature equal to or higher than an inflection point at which the viscosity of the liquid to be filtered changes from a high viscosity to a low viscosity.   The vibration filtration method according to claim 1, wherein the liquid to be filtered is a waste slurry having a two-point peak distribution in which silicon cutting waste and abrasive grains generated in a silicon processing step are mixed in a coolant.   The vibration filtration method according to claim 1, wherein before the vibration filtration is stopped, the overflow of the overflow liquid is released to wash away the suspended particle layer, and then the vibration filtration is stopped. A supply pump for supplying the liquid to be filtered;
A vibrating filter that separates the filtrate from the filtrate and the overflow liquid in which the particles are concentrated by the suspended particle layer that is supplied to the vibrating filter from the supply pump and formed on the filter;
A switching valve provided in the outflow channel of the overflow liquid;
An adjustment flow path connected to the switching valve via a throttle valve;
An open channel connected to the switching valve;
Filtration performance detecting means for detecting filtration performance by a filter;
A switching controller that switches a switching valve so as to open the overflow liquid to an open flow path when the filtration performance detected by the filtration performance detection means falls below a set value;
A vibration filtering device comprising:   The vibration filtration device according to claim 8, further comprising a shut-off valve that shuts off the outflow of the filtrate when the overflow liquid is opened to the open flow path.   The vibration filtration device according to claim 8 or 9, wherein the filtration performance detection means is a flow meter for detecting the outflow flow rate of the filtrate.   The vibration filtration device according to claim 8 or 9, wherein the filtration performance detecting means is a pressure gauge for detecting a supply pressure of the liquid to be filtered when the liquid to be filtered is supplied to the filter by a metering pump.   The vibration filtration device according to any one of claims 8 to 11, wherein the tank has a heater for heating the liquid to be filtered.   9. The vibration filtering device according to claim 8, wherein the switching controller controls the switching valve so as to open the overflow liquid to an open channel before stopping the vibration filtering.

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