Ultrasonic wet classification apparatus and ultrasonic wet classification method

Abstract

To provide an ultra-wet classification device and a wet classification method capable of reducing breakage of a filter due to cavitation at the time of ultrasonic irradiation and greatly prolonging the life of the filter.SOLUTION: The ultrasonic wet classification apparatus includes a raw liquid supply pipe for supplying a raw liquid from a raw liquid tank to a classification tank, the classification tank having a filter laid on a bottom thereof, a collection tank for collecting a process liquid having passed through the filter in the classification tank, a discharge pipe line for discharging the process liquid in the collection tank to a process liquid tank, an ultrasonic vibrator for vibrating the filter, and a decompression pump for decompressing the classification tank and the collection tank. By this constitution, ultrasonic wet classification treatment can be performed while reducing the damage of the filter caused by cavitation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ultrasonic wet classification device and an ultrasonic wet classification method that perform classification by vibrating a filter using ultrasonic waves under reduced pressure. [Background technology]

[0002] Conventionally, a wet classification device is known that classifies a liquid containing particles of different diameters using a filter to classify particles into particles of the same diameter. Also known is an ultrasonic wet classification device that irradiates the wet classification device with ultrasonic waves to vibrate the filter, thereby floating particles accumulated on the filter and eliminating filter clogging, thereby continuously classifying the particles.

[0003] Patent Document 1 discloses a wet classification device that includes a filter unit in a classification tank, and performs classification with a filter member by suction force from a pressure reducing means while vibrating the filter of the filter unit with ultrasonic waves.

[0004] Patent Document 2 describes an ultrasonic processing device that suppresses the occurrence of cavitation caused by ultrasonic waves by degassing the cleaning liquid, thereby preventing damage to the object being cleaned. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6012338 [Patent Document 2] Patent No. 6171240 Summary of the Invention [Problem to be solved by the invention]

[0006] In wet classification devices using ultrasonic waves, cavitation occurs in the raw liquid due to ultrasonic vibrations, and the filter is damaged by erosion caused by the cavitation, resulting in durability problems.

[0007] In Patent Document 1, the classification tank is open, so there is a large amount of dissolved gas in the liquid, which can cause cavitation and damage the filter member.

[0008] Patent Document 2 describes a technology for preventing cavitation by degassing the cleaning solution, but if the dissolved gas is not sufficiently removed, the resulting water becomes partially degassed, which makes it more susceptible to cavitation. Furthermore, a large amount of energy is required to fully remove the dissolved gas, so a long degassing time must be set aside in advance. Even if the dissolved gas is sufficiently removed, a small amount of cavitation still occurs, which can damage the object being cleaned.

[0009] The present invention proposes an ultrasonic wet classification device and an ultrasonic wet classification method that reduce filter destruction caused by cavitation during ultrasonic irradiation and significantly extend the life of the filter. [Means for solving the problem]

[0010] The present invention relates to an ultrasonic wet classification device that separates fine particles by irradiating a filter with ultrasonic waves to vibrate it while supplying raw liquid parallel to the filter. The device is equipped with a raw liquid supply pipe that supplies raw liquid from a raw liquid tank to a classification tank, a classification tank with a filter installed at the bottom, a recovery tank that recovers the treatment liquid that has passed through the filter in the classification tank, a discharge pipeline that discharges the treatment liquid in the recovery tank to the treatment liquid tank, an ultrasonic vibrator that vibrates the filter, and a vacuum pump that reduces the pressure in the classification tank and recovery tank.Since the classification process is carried out under reduced pressure, damage to the filter due to cavitation can be suppressed.

[0011] By connecting the vacuum pump to a sealed vacuum chamber containing the classification tank and the collection tank, the classification tank and the collection tank are depressurized to a constant degree, allowing efficient classification processing.

[0012] The vacuum pump is also connected to the stock solution tank and the processing solution tank, so that the entire apparatus can be decompressed to a constant degree, allowing the stock solution to be returned and the processing solution to be discharged by gravity.

[0013] By arranging the filter at a predetermined angle from the horizontal, air accumulation below the filter can be eliminated, and ultrasonic wave obstruction due to the formation of an air layer can be prevented.

[0014] In an ultrasonic wet classification method in which a filter is irradiated with ultrasonic waves to vibrate it while a raw liquid is supplied parallel to the filter to separate fine particles, a raw liquid tank that stores the raw liquid, a raw liquid supply pipe that supplies the raw liquid from the raw liquid tank to a classification tank, a classification tank that classifies the raw liquid with a filter, a recovery tank that recovers the treated liquid that has passed through the filter, a discharge pipeline that discharges the treated liquid from the recovery tank, and a treatment liquid tank that stores the treated liquid discharged from the discharge pipeline are all connected in a sealed state, and by maintaining a constant pressure reduction in each device during the classification process, the classification process can be performed under reduced pressure without prior degassing, and damage to the filter due to cavitation can be suppressed. [Effects of the Invention]

[0015] According to the present invention, classification under reduced pressure reduces damage to the filter due to cavitation during ultrasonic irradiation, allowing for classification of fine particle sizes using a thin plate filter with a fine pore size, significantly extending the filter's lifespan. Furthermore, because prior degassing is not required, the energy and time required for degassing are reduced. Energy loss during ultrasonic irradiation is reduced by reducing the amount of dissolved air in the liquid. Furthermore, circulation of the raw liquid has a water-cooling effect on the ultrasonic vibrator. Furthermore, maintaining a constant degree of decompression throughout the device allows for the return of the raw liquid and the discharge of the treated liquid by gravity. Additionally, the inclination of the classification tank removes air bubbles trapped below the filter, allowing for efficient transmission of ultrasonic waves to the filter. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a flow diagram of an ultrasonic wet classification device according to the present invention. [Figure 2] FIG. 10 is a schematic cross-sectional view of a classification tank and a recovery tank according to another embodiment of the present invention. [Figure 3] FIG. 10 is a flow diagram of an ultrasonic wet classification device according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] FIG. 1 is a flow diagram of an ultrasonic wet classification device according to the present invention. The ultrasonic wet classification device 1 according to the present invention is composed of a raw liquid tank 2, a raw liquid supply pipe 3, a classification tank 6, a return pipe 8, a recovery tank 9, a discharge pipeline 10, a treatment liquid tank 11, and a vacuum pump 15, and classification is performed with the pressure in the classification tank 6 and the recovery tank 9 reduced.

[0018] The stock solution tank 2 stores stock solution containing particles to be classified. A stock solution supply pipe 3 equipped with a valve V1 is connected to the bottom of the stock solution tank 2, and the stock solution stored in the stock solution tank 2 is supplied to the classification tank 6 by a stock solution supply pump 4 installed in the stock solution supply pipe 3.

[0019] The classification tank 6 is a cylindrical member with an open top, and a metal filter 7 is installed at the bottom. A raw liquid supply pipe 3 is connected to the bottom of the side wall of the classification tank 6, and raw liquid is jetted from the raw liquid supply pipe 3 parallel to the filter 7, blowing away large particles larger than the pore size of the filter 7 that accumulate on the filter 7 and preventing clogging of the filter 7. Fine particles smaller than the pore size of the filter 7 pass through the filter 7 and flow into the collection tank 9. By performing a cross-flow classification process in this way, in which the raw liquid is supplied in a direction perpendicular to the filtration direction, the filter 7 is washed during the classification process, allowing for continuous classification and eliminating the need for a filter 7 cleaning device or cleaning process.

[0020] 1, the raw liquid supply pipe 3 is connected to the lower side wall of the classification tank 6, but the raw liquid supply pipe 3 may be inserted from an open section at the top of the classification tank 6 and bent near the filter 7 so that the opening is parallel to the surface of the filter 7. Also, by providing an air supply pipe midway along the raw liquid supply pipe 3 and supplying air into the raw liquid supply pipe 3 when the raw liquid is being supplied, the raw liquid and air will mix inside the pipe, and when the raw liquid is jetted into the classification tank 6, the air will blow away any deposits on the filter 7, thereby enhancing the crossflow effect.

[0021] A return pipe 8 is connected to the upper wall of the classification tank 6, and when the stock solution in the classification tank 6 reaches a predetermined level or higher, it overflows into the return pipe 8 and is returned to the stock solution tank 2. In the ultrasonic wet classification device 1 of the present invention, the stock solution is supplied to the classification tank 6 at a flow rate greater than the throughput of the filter 7 in order to perform crossflow classification. By leaving the top of the classification tank 6 open and connecting the return pipe 8 to a predetermined height in the classification tank 6, the pressure on the filter 7 remains constant regardless of the amount of stock solution supplied, thereby reducing the load on the filter 7. Furthermore, although the classification processing capacity in the classification tank 6 varies depending on the head pressure on the filter 7, the stock solution storage water level in the classification tank 6 is always maintained at the height of the return pipe 8, allowing for stable classification processing.

[0022] The connection height of the return pipe 8 can be determined appropriately depending on the strength, pore size, etc. of the filter 7. When a highly durable filter 7 is used, or when precise flow control of the raw liquid supply pump 4 is required even with a thin plate filter, the classification tank 6 may have a sealed structure, and classification processing can be performed by cross-flow without using an overflow structure.

[0023] The treatment liquid, which is made up of fine particles that have been classified in the classification tank 6 and passed through the filter 7, flows into the recovery tank 9. The recovery tank 9 is a cylindrical member that surrounds the classification tank 6 and recovers the entire amount of treatment liquid that has passed through the filter 7. After the treatment liquid is temporarily stored in the recovery tank 9, it is discharged to a treatment liquid tank 11 through a discharge pipe 10 connected to the recovery tank 9.

[0024] The discharge pipeline 10 may be configured, for example, as an inverted U-shaped riser pipe connected to the bottom of the collection tank 9. By setting the height of the riser above the height of the filter 7, the treated liquid in the collection tank 9 is maintained at a water level that allows the filter 7 to be immersed in the treated liquid, while the treated liquid is discharged into the treated liquid tank 11. Alternatively, the discharge pipeline 10 may be configured by connecting a pipe to the wall of the collection tank 9 above the height of the filter 7 or by providing an overflow weir, so that treated liquid above a predetermined level overflows and is discharged into the treated liquid tank 11. Note that by arranging the treatment liquid tank 11 below the collection tank 9, the treated liquid will naturally flow down the discharge pipeline 10. Alternatively, a pump may be provided in the discharge pipeline 10 to forcibly discharge the treated liquid. In this case, the discharge pipeline 10 can be arranged freely at any height, but the pump should be controlled so that the filter 7 is always immersed in the treated liquid.

[0025] An ultrasonic vibrator 12 is fixed to the bottom of the outer wall of the collection tank 9. The ultrasonic vibrator 12 is connected to an oscillator 13, and an electrical signal supplied from the oscillator 13 causes the ultrasonic vibrator 12 to vibrate and generate ultrasonic waves. The ultrasonic waves propagate toward the treatment liquid filled in the collection tank 9 and reach the filter 7. When the filter 7 receives the ultrasonic waves and vibrates, large particles that are larger than the pore size of the filter 7 and have accumulated on the filter 7 are peeled off and dispersed from the surface of the filter 7, enhancing the crossflow effect. This allows fine particles smaller than the pore size of the filter 7 to smoothly flow downstream of the filter 7. Furthermore, because the filter 7 is immersed in the treatment liquid, the ultrasonic waves from the ultrasonic vibrator 12 are efficiently transmitted to the filter 7 without passing through an air layer.

[0026] The ultrasonic vibrator 12 of the present invention may be installed at any location other than the bottom of the outer wall of the collection tank 9, as long as it can vibrate the filter 7 using ultrasonic waves. For example, the ultrasonic vibrator 12 may be fixed to the side wall of the collection tank 9, and vibrations may be applied parallel to the filter 7 via the treatment liquid. Alternatively, as shown in FIG. 2A, the ultrasonic vibrator 12 may be fixed to the side wall of the classification tank 6, and the classification tank 6 may be directly vibrated to vibrate the filter 7. Furthermore, as shown in FIG. 2B, the ultrasonic vibrator 12 may be immersed in the stock solution in the classification tank 6 and positioned facing the filter 7, and the filter 7 may be vibrated from above the classification tank 6 via the stock solution.

[0027] 2A and 2B, the ultrasonic waves from the ultrasonic vibrator 12 vibrate the filter 7 without the treatment liquid being involved, and it is not necessary to immerse the filter 7 in the treatment liquid. Therefore, the discharge pipe 10 may be connected to the bottom of the recovery tank 9, and the treatment liquid may be immediately discharged to the treatment liquid tank 11 without temporarily storing it in the recovery tank 9.

[0028] 1 and 2 contains the classification tank 6 and is configured to be sealed, and is connected to a vacuum pump 15 via a vacuum line 14. By starting the vacuum pump 15, the classification tank 6 and the collection tank 9 are depressurized to a constant pressure. With the classification tank 6 and the collection tank 9 in a depressurized state, the filter 7 is vibrated by the ultrasonic vibrator 12, and the raw liquid is classified. In this case, the collection tank 9 functions as a decompression chamber 5.

[0029] When ultrasonic waves are applied from the ultrasonic transducer 12 under reduced pressure, the cavitation generated in the liquid expands more than it would expand under atmospheric pressure, expanding without contraction or collapse, preventing erosion of the filter 7. This significantly reduces damage to the filter 7. Additionally, classification can be performed while the classification tank 6 and recovery tank 9 are depressurized, eliminating the need to degas the raw liquid or the treated liquid beforehand. This reduces the energy and time required for degassing and allows for continuous operation. Furthermore, dissolved air, which inhibits ultrasonic waves, is removed from the depressurized treated liquid, improving the ultrasonic transmission efficiency in the treated liquid and increasing the classification throughput of the filter 7. Furthermore, cavitation suppression is enhanced by setting the classification tank 6 and recovery tank 9 to -0.05 MPaG or less.

[0030] By sealing the ultrasonic vibrator 12 in a case 16 and connecting the case 16 to a vacuum pump 15 via a vacuum line 14, the noise generated when the ultrasonic vibrator 12 oscillates ultrasonic waves is blocked within the vacuum-sealed case 16, preventing the noise from leaking to the outside. Furthermore, while heat generated by the vibration of the ultrasonic vibrator 12 is normally insulated within the case 16 and difficult to dissipate to the outside, heat is transferred to the treatment liquid through the wall of the recovery tank 9 to which the ultrasonic vibrator 12 is fixed, and the raw liquid and treatment liquid circulate within the tank, so that heat exchange is constantly taking place, allowing the ultrasonic vibrator 12 to be cooled.

[0031] The decompression line 14 is also branched and connected to the sealed stock solution tank 2 and treated solution tank 11, and a decompression pump 15 simultaneously decompresses the classification tank 6, recovery tank 9, stock solution tank 2, and treated solution tank 11. This makes the degree of decompression in the stock solution tank 2 and treated solution tank 11 consistent with that in the classification tank 6 and recovery tank 9, allowing the stock solution to overflow into the stock solution tank 2 and the treated solution to overflow into the treated solution tank 11 to occur smoothly by gravity.

[0032] The pressure reduction structure in the present invention is such that the classification tank 6 and the recovery tank 9 can be reduced to a constant pressure, since cavitation damage can be reduced if the filter 7 is subjected to ultrasonic vibrations under reduced pressure. Therefore, the configuration of the classification tank 6 and the recovery tank 9 is not limited to that shown in FIG.

[0033] 3, the classification tank 6, collection tank 9, and ultrasonic vibrator 12, all of which have an open top, are housed together in a decompression chamber 5, and a decompression pump 15 is connected to the decompression chamber 5 via a decompression line 14, making it possible to constantly reduce the pressure in the classification tank 6 and collection tank 9. In addition, according to the configuration of FIG. 3, since the collection tank 9 is housed within the decompression chamber 5, noise generated by the vibration of the collection tank 9 by the ultrasonic vibrator 12 can be blocked within the decompression chamber 5.

[0034] When ultrasonic waves are applied to the processing liquid in the recovery tank 9, which is under reduced pressure, the processing liquid is in a state where dissolved gases are easily released as bubbles. The bubbles released from the processing liquid rise and accumulate below the filter 7, forming an air layer in the space below the filter 7, which can hinder the transmission of ultrasonic waves. Therefore, the filter 7 may be tilted at a predetermined angle from the horizontal position, allowing the bubbles to be discharged from the processing liquid along the tilted filter 7. Eliminating the air layer that hinders the transmission of ultrasonic waves can prevent a decrease in classification performance. Since it is sufficient to tilt the filter 7, the filter 7 alone may be tilted, or the filter 7 may be tilted together with other components. Alternatively, the classification tank 6, filter 7, and collection tank 9 may all be arranged parallel to each other and tilted together. [Example]

[0035] An embodiment of the present invention will be described in detail below with reference to FIG. First, the preparation process prior to the classification process will be described. With the valve V1 disposed in the raw liquid supply pipe 3 closed, the raw liquid tank 2 is filled with raw liquid. In addition, the recovery tank 9 is filled with priming water up to the height where the filter 7 is immersed. At this time, if the air pocket below the filter 7 is removed and the tank is filled with priming water, the air layer that interferes with the ultrasonic waves can be eliminated, and the ultrasonic vibrations can be transmitted sufficiently to the filter 7 from the start of the classification process. Note that the recovery tank 9 may be filled with the treatment liquid recovered during the previous classification process as priming water.

[0036] Once the collection tank 9 has been filled with a predetermined amount of priming water, the vacuum pump 15 is started to reduce the pressure in the sealed classification tank 6, collection tank 9, raw liquid tank 2, and treatment liquid tank 11 to a predetermined level. After the pressure has been reduced to the predetermined level, the vacuum pump 15 may be operated continuously until the end of the classification process, but the power consumption related to the vacuum pump 15 can be reduced by closing the vacuum line 14 with a valve (not shown) to stop the vacuum pump 15.

[0037] Next, the classification process will be described. Valve V1 is opened and the raw liquid supply pump 4 is started, supplying raw liquid from the raw liquid supply pipe 3 into the classification tank 6. The opening of the raw liquid supply pipe 3 is positioned near and parallel to the filter 7, so that the raw liquid is supplied to the filter 7 in a crossflow manner. This ensures that the surface of the filter 7 is constantly washed away by the crossflow jet. Furthermore, because of the crossflow jet, raw liquid is supplied to the classification tank 6 in excess of the amount that the filter 7 can process, and raw liquid that exceeds a predetermined height in the classification tank 6 is returned to the raw liquid tank 2 via the return pipe 8.

[0038] When the raw liquid begins to circulate in the classification tank 6, the oscillator 13 is started to oscillate the ultrasonic vibrator 12. The ultrasonic waves generated from the ultrasonic vibrator 12 travel through the liquid in the recovery tank 9 and vibrate the filter 7. The vibration of the filter 7 washes out large particles that have been clogging the pores of the filter 7, and particles smaller than the pores of the filter 7 flow downstream.

[0039] At this time, the ultrasonic waves from the ultrasonic vibrator 12 are also transmitted into the classification tank 6 via the filter 7, but the ultrasonic waves propagating into the classification tank 6 are disturbed by the turbulence generated in the classification tank 6 by the crossflow jet of the stock solution. This suppresses cavitation that may occur above the filter 7 in the classification tank 6.

[0040] Due to the difference in head between the classification tank 6 and the recovery tank 9, the treated liquid flows out of the filter 7 into the recovery tank 9. When the liquid level in the recovery tank 9 exceeds a predetermined level, the treated liquid is allowed to overflow and is discharged through a discharge pipe 10 into a treated liquid tank 11. [Industrial Applicability]

[0041] The ultrasonic wet classification device and ultrasonic wet classification method according to the present invention perform cross-flow classification while preventing the occurrence of ultrasonic cavitation, enabling efficient classification over a long period of time while minimizing filter clogging and damage. Therefore, they can be applied to the classification of a variety of materials, including flour, pharmaceuticals, ceramics, food, minerals, metals, and resin raw materials. [Explanation of symbols]

[0042] 1 Ultrasonic wet classifier 2. Concentrate tank 3 Stock solution supply pipe 5. Decompression Chamber 6 Classifying tank 7 Filters 8 Return pipe 9. Collection tank 10 Discharge pipe 11 Processing liquid tank 12 Ultrasonic transducer 15. Vacuum pump

Claims

1. In an ultrasonic wet classification device (1), a filter (7) is irradiated with ultrasonic waves to vibrate the filter, while a raw liquid is supplied in parallel to the filter (7) to separate fine particles, a raw liquid supply pipe (3) for supplying raw liquid from the raw liquid tank (2) to the classification tank (6); a classification tank (6) with a filter (7) installed at the bottom; a recovery tank (9) for recovering the treated liquid that has passed through the filter (7) of the classification tank (6); a discharge pipe (10) for discharging the treatment liquid in the recovery tank (9) to a treatment liquid tank (11); an ultrasonic vibrator (12) that vibrates the filter (7); a decompression pump (15) for decompressing the classification tank (6) and the recovery tank (9); Equipped with An ultrasonic wet classification device characterized by:

2. A sealed decompression chamber (5) containing the classification tank (6) and the recovery tank (9) is connected to a decompression pump (15).

2. The ultrasonic wet classification device according to claim 1.

3. The decompression pump (15) is also in communication with the raw liquid tank (2) and the treatment liquid tank (11).

3. The ultrasonic wet classification device according to claim 2.

4. The filter (7) is disposed at a predetermined angle from the horizontal.

4. The ultrasonic wet classification device according to claim 1, wherein the ultrasonic wet classification device is a wet classification device.

5. In an ultrasonic wet classification method, a filter (7) is irradiated with ultrasonic waves to vibrate the filter, and a raw liquid is supplied parallel to the filter (7) to separate fine particles, The apparatus includes a raw liquid tank (2) for storing the raw liquid, a raw liquid supply pipe (3) for supplying the raw liquid from the raw liquid tank (2) to a classification tank (6), a classification tank (6) for classifying the raw liquid with a filter (7), a recovery tank (9) for recovering the treated liquid that has passed through the filter (7), a discharge pipe (10) for discharging the treated liquid from the recovery tank (9), and a treatment liquid tank (11) for storing the treated liquid discharged from the discharge pipe (10), all of which are connected in a sealed state; Maintain constant pressure reduction for each device during classification process An ultrasonic wet classification method characterized by:

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