JP2009095806A - Filtration method and filtration apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a filtration process at high-efficiency without using a body feed method or pre-coating method in a filtration process for a suspension stock solution by a pressure filtration or suction filtration. <P>SOLUTION: The filtration is performed in a state that fine bubbles are mixed in the suspension stock solution. When the diameter of fine bubbles becomes 50 μm or less, the fine bubbles have characteristics different from normal bubbles, have negative charges to be deposited on suspension particles, and the bubbles are mutually repulsive to be uniformly dispersed in the liquid and are extremely slow in the rising speed in the liquid. Accordingly, deposition layers of suspension particles are formed while uniformly forming fine bubbles and channels for liquid on the surface of filter media, the fine bubbles are expanded due to large pressure drop near the surface of the filter media, and the fine bubbles lost charges mutually bond, thereby weakening the deposition layers to exfoliate from the inside. In addition, when a filtration flow rate decreases, the pressure on the downstream side of the filter media is reduced (reduced more in the suction filtration), thereby promoting the exfoliation and collapse. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a filtration method and a filtration device using pressure filtration or reduced pressure filtration, and more particularly to a technique for improving filtration efficiency by utilizing the properties of fine bubbles.

  In the manufacturing process of a printed wiring board (PCB), a surface-polishing process is interposed before applying a photosensitive resist or screen printing on a copper-clad laminate. The purpose is to improve the adhesion of the photosensitive resist and the wiring pattern printing material by polishing the surface copper in advance so that accurate etching can be performed. Also, in the processing of optical elements, flat panels of liquid crystal display devices and glass substrates for hard disks, polishing is performed so as to obtain required surface roughness, parallelism, flatness, and the like.

  In that case, a large amount of clean water is required for the actual polishing step and cleaning after polishing, and naturally the drained liquid after use is turbid with fine particles of polished copper and glass. When using abrasive grains, the fine particles whose abrasive grains are crushed also become turbid in the drainage. The size of the fine particles contained in the drainage liquid in the polishing step is about 0.1 to 50 (μm), and the concentration of the fine particles is about 50 to 1000 (mg / l), which is relatively low. Discharging the liquid as it is is prohibited by the Water Pollution Control Law, and it is obliged to discharge it after reducing the concentration of suspended particles (fine particles) to a certain standard. In addition, the aqueous solution having a reduced concentration as described above is often recycled.

  Therefore, the drainage is filtered. However, if the suspended particles are fine, clogging with the deposited fine particles occurs and the filtration efficiency deteriorates. Therefore, as a solution, pearlite or diatomaceous earth is generally used as a solution. A body feed method in which a filtration aid is added for filtration is employed. The effect of this body feed method varies depending on the type and amount of filter aid to be added. In general, the amount of filter aid added is about 1.5 to 3 times the amount of solid matter contained in the suspension stock solution. It is said that the amount can be increased and the filtration time can be extended by 2 to 3 times. The following Patent Documents 1 to 3 disclose the filtration method using body feed for various suspension stock solutions. .

  Further, as a method for performing filtration while maintaining high filtration efficiency, a precoat method has been conventionally employed, and it is often used in combination with the body feed method. In this pre-coating method, a pre-coat layer is formed in advance on the filter medium surface with a filter aid such as diatomaceous earth, and when the filtration speed is reduced, the suspended particle accumulation layer supplemented with the pre-coat layer is combined with the skin of the pre-coat layer. Various methods for renewing the skin of the precoat layer are proposed in the following Patent Documents 4 to 6 and the like.

JP 2007-135579 A JP 2004-107629 A Japanese Patent Laid-Open No. 2000-32773 JP 2005-177549 A JP-A-10-258208 JP-A-5-228314

  By the way, the body feed method and the precoat method require a filter aid, and the filter aid must select a material according to the suspension stock solution and manage the amount of addition. In addition, the body feed method requires an addition step to the suspension stock solution, and the precoat method requires a precoat layer formation step using only a filter aid at the beginning, and the suspension stock solution is filtered for a certain period of time. In addition, a series of steps are always involved because air is blown over the accumulated layer of suspended particles formed on the surface of the filter medium by filtration to recover the cake as a cake. Therefore, the ratio of the time required for each step other than the original filtration step is considerably large. In addition, since the filter aid is mixed in the cake in the body feed method or the precoat method, there is also a problem that the volume of the cake becomes larger than the amount of suspended particles captured. In addition, when the suspended particles to be captured are valuable materials, if the filter aid is mixed as a foreign substance, there is a disadvantage in that it is disadvantageous for recycling by recovery.

  Therefore, in the present invention, in the filtration process of the suspension stock solution by pressure filtration or vacuum filtration, the accumulated layer of suspended particles formed on the filter medium is peeled off during the filtration operation without using the body feed method or the precoat method. The purpose is to provide a filtration method capable of constantly renewing the filtration surface by collapsing, and a filtration device that rationally realizes the method, so that the suspension stock solution can be filtered with high efficiency. And

  A first invention relates to a filtration method of a suspension stock solution by pressure filtration or reduced pressure filtration, wherein the filtration is performed in a state where fine bubbles are mixed in the suspension stock solution.

  In this invention, in the pressure filtration, the upstream side of the filter medium is pressurized, and in the vacuum filtration, the downstream side of the filter medium is depressurized, so the suspended particles and fine bubbles in the suspension stock solution move together with the liquid to the surface of the filter medium. I will do it. When the microbubbles become microbubbles having a diameter of 50 μm or less, they have colloidal characteristics and are negatively charged, and some of them adhere to the positively charged suspended particles. The fine bubbles that are not attached repel each other, and the bubble concentration in the suspension suspension is kept uniform. Therefore, a deposition layer of suspended particles is formed on the surface of the filter medium while the fine bubbles and the liquid flow paths are formed almost uniformly like leaf veins in the course of filtration. Therefore, even if the deposited layer becomes thick, the decrease in the amount of liquid flow is small and high filtration efficiency can be obtained. Furthermore, since the pressure drop is large near the surface of the filter medium, the microbubbles tend to expand, and the microbubbles that have lost their charge tend to bond with each other in the flow path. And peel from inside. In addition, the gas which becomes a bubble is not limited to air, and a gas corresponding to the type of nitrogen gas or suspension stock solution is used.

  In the first aspect of the invention, as a method for mixing fine bubbles in the suspension stock solution during filtration, gas is dissolved in the suspension stock solution under high pressure, and the suspension stock solution in which the gas is dissolved is filtered. A method of generating fine bubbles in the suspension stock solution in the filtration chamber and a process of mixing fine bubbles into the suspension stock solution by gas-liquid mixing means, and the suspension stock solution after the treatment is directly applied to the filtration chamber The method of injecting into the can be adopted. In particular, the former method is effective when performing pressure filtration.

  Further, if the filtration surface is configured in the vertical direction, filtration is performed while measuring the flow rate of the filtration target liquid, and the pressure downstream of the filtration surface is lowered when the measured flow rate is reduced. It is possible to promote the separation and dropping of the accumulated layer of suspended particles that are gradually formed thick on the filtration surface, and to forcefully form a new filtration surface to maintain high filtration efficiency.

  A second invention is a filtration device for carrying out the first invention by a pressure filtration method, and has a filtration chamber in which a filter medium is mounted on a vertical inner wall surface with a water-permeable layer interposed. A filter body in which an injection hole for injecting the liquid to be filtered from the outside into the filtration chamber, and a drain hole for discharging the filtered water from the water passage layer to the outside, and a suspension stock solution under high pressure A raw solution processing means for producing a liquid to be filtered by mixing fine gas into the suspension stock solution by gas-liquid mixing treatment, and a filtration target liquid produced by the stock solution processing means And a pressure feeding means for pressure feeding to the filtration chamber through the injection hole.

  Further, in the second invention, when the flow rate detecting means for detecting the flow rate of the suspension stock solution pumped by the pumping means, and when the detected flow rate value by the flow rate detecting means becomes a predetermined value or less, the filter body If pressure reducing means for reducing the pressure on the drain hole side is provided, as described in the first invention, the filtration function is forcibly renewed by promoting separation and dropping of the deposited layer on the filtration surface. be able to.

  A third invention is a filtration device for carrying out the first invention by a vacuum filtration method, and has a filtration chamber in which a filter medium is mounted with a water-permeable layer interposed on an inner wall surface in a vertical direction, A filter body in which an injection hole for injecting a liquid to be filtered from the outside into the filtration chamber, and a drain hole for discharging the filtrate water from the water passage layer to the outside, and a suspension stock solution under high pressure A raw solution processing means for generating a liquid to be filtered by dissolving a gas or mixing fine bubbles into a suspension stock solution by a gas-liquid mixing process, and a liquid to be filtered generated by the stock solution processing means being larger than atmospheric pressure The present invention relates to a filtration apparatus comprising: a liquid feeding means that sends pressure to the filtration chamber through an injection hole of the filter body; and a decompression means that decompresses and sucks filtered water from the discharge hole of the filter body.

  In the third aspect of the invention, the flow rate detecting means for detecting the flow rate of the suspension stock solution sent by the liquid feeding means is provided, the pressure reducing means is a variable pressure reducing means capable of changing the pressure reduction level, and the flow rate detecting means If the detected flow rate value by the means is greater than a predetermined value, the reduced pressure level by the variable pressure reducing means is set to the first reduced pressure level for vacuum filtration, and if the detected flow rate value is less than the predetermined value If a decompression control means for setting the second decompression level lower than the first decompression level is provided, as in the case of the second invention, the separation and fall of the deposited layer on the filtration surface are promoted. Thus, the filtration function can be forcibly updated.

  As described above, in the second and third inventions, it becomes possible to cause the accumulated layer of suspended particles adhering to the filter medium to collapse and fall as a slurry, but in the second invention, the liquid to be filtered enters the filtration chamber. In the invention of the third aspect, the liquid to be filtered is sent into the filtration chamber at a pressure higher than atmospheric pressure. Therefore, if a slurry discharge hole leading to the outside is formed in the lowermost part of the filtration chamber of the filter body or in the vicinity thereof, and the first on-off valve is connected to the slurry discharge hole, the filtration step is sequentially performed. The slurry can be discharged. In addition, if a gas discharge hole leading to the outside is formed in the uppermost part of the filtration chamber of the filter body or in the vicinity thereof, and a second on-off valve is connected to the gas discharge hole, the filter medium does not pass through. The fine bubbles rising to the upper part of the filtration chamber can be combined and discharged.

  In realizing the slurry discharge function and the gas discharge function, the filtration chamber is a hollow portion corresponding to a shape in which a quadrangular pyramid is joined to the upper side surface and the lower side surface of the rectangular parallelepiped, or a disk-shaped hollow portion. It is reasonable to be configured as

  The filtration method and filtration apparatus of the present invention have the following effects based on the above configuration. By filtering with fine air bubbles mixed in the suspension stock solution, it is possible to perform filtration processing with extremely high efficiency without using a filter aid as in the body feed method and precoat method, and suspended particles. Makes it easy to recycle by collecting it. In addition, the suspended particle deposit layer formed on the filter medium is a fragile layer due to the securing of the flow path by bubbles, and when it falls off due to separation or collapse, it always filters on a new filtration surface. As a result, the filtration efficiency can always be kept high. Further, when the suspended particles are deposited thickly on the filter medium and the filtration efficiency is lowered, it is possible to recover the filtration efficiency by detecting the state and promoting the separation / falling of the deposited layer. The suspended particle deposit layer peels off and falls to become a slurry at the bottom of the filtration chamber, and fine bubbles that have not passed through the filter medium rise to form a gas reservoir at the top of the filtration chamber. The filter device realizes a configuration for appropriately discharging them to the outside.

Hereinafter, embodiments of a filtration method and a filtration device of the present invention will be described in detail with reference to the drawings.
[Embodiment 1]
First, FIG. 1 is a schematic configuration diagram of a filtration device. In the figure, 10 is a system control unit, 11 is a raw water tank for storing a suspension stock solution, 12 is an on-off valve, 13 is a liquid feed pump, 14 to 16 are on-off valves, 17 is a flow meter, 18 is a pressure gauge, 19 Is a check valve, 20 is a pressure reducing valve, 21 is a pressure gauge, 22 is an air flow meter, 23 is an on-off valve, 24 is a gas-liquid mixer, 25 is a pressurized tank, 25a is a liquid level gauge, and 26 and 27 are open and close Valve, 28 is an exhaust solenoid valve, 29 is an on-off valve, 30 is a pressure gauge, 31 is a filter, 32 is a slurry discharge solenoid valve, 33 is an exhaust solenoid valve, and 34 and 35 are on-off valves. The entire apparatus is controlled by the system control unit 10. The system control unit 10 receives detection signals such as pressure, flow rate, and liquid level, and controls the liquid feed pump 13, the gas-liquid mixer 24, and the electromagnetic valves 28, 32, and 33. It comes to control. The suspension stock solution in this embodiment is a drainage liquid generated in the surface-polishing step in the PCB manufacturing process. As described above, about 50 to 50 suspended particles of copper and abrasive grains are present. It is mixed in the liquid at a concentration of about ~ 1000 (mg / l).

  The filter 31 is configured as shown in FIG. 2 [(A) is a cross-sectional view, and (B) is a cross-sectional view taken along the line XX of (A) (filter cloth is omitted)]. That is, the two plate bodies 41 and 42 having a central region formed as a concave portion are joined together to form a space constituted by the concave portions as a filtration chamber 43, and each of the filtration chambers 43 corresponding to the bottom surface of the concave portion. Filter cloths 45a and 45b are provided on the inner wall surface with metal or resin nets 44a and 44b interposed therebetween.

  Here, the nets 44a and 44b are made by braiding metal wires or resin wires with a certain thickness, but a punching board having a large number of holes is separated from the inner wall surface of the filtration chamber 43 through a spacer. A method of attaching in a state of being allowed to pass, a method of forming irregularities on the inner wall surface of the filtration chamber 43, etc. may be adopted, and in any case, a method of forming a water flow layer behind the filter cloth 45a, 45b If it is.

  In addition, the board bodies 41 and 42 are sandwiched between the peripheral portions of the filter cloths 45a and 45b through the seal member 46 at the frame portions that serve as joint portions, and the entire inner surface of the filter chamber 43 is formed by the filter cloths 45a and 45b. It is lined up. As shown in FIG. 2, as for the mechanism for joining the board bodies 41, 42, a method by tightening bolts and nuts using holes provided at the four corners of each board body 41, 42, or one board body. For example, a method in which 41 is fixed and the other disk body 42 is pressed by a hydraulic cylinder while being guided by a guide mechanism is employed.

  Then, the injection of the liquid to be filtered into the filtration chamber 43 is performed through the injection hole 47 penetrating the one plate body 41, the net 44a, and the filter cloth 45a, and the injection hole 47 side of the filtration chamber 43 A flange nut is screwed into the opening portion in order to clamp the filter cloth 45a and the net 44a to the inner wall surface of the disc body 41. In addition, drain holes 48a and 48b are formed at positions corresponding to the lower regions of the nets 44a and 44b in the respective board bodies 41 and 42, and flow into the water flow layers formed by the nets 44a and 44b. The drained filtered water can be discharged.

  By the way, as shown in FIG. 2, the filtration chamber 43 is a hollow space corresponding to a shape in which a quadrangular pyramid is joined to the upper side surface and the lower side surface of the rectangular parallelepiped. It becomes the apex position of the pyramid part. In this embodiment, the air discharge holes 49a and 49b communicate with the outside in the vicinity of the apex position on the uppermost side in each board 41 and 42, and communicate with the outside in the vicinity of the apex position on the lowermost side. Slurry discharge holes 50a and 50b are formed, and as shown in FIG. 1, the air discharge holes 49a and 49b have exhaust solenoid valves 33, and the slurry discharge holes 50a and 50b have slurry discharge solenoid valves 32. Each is connected.

  Next, the operation of the filtration device according to this embodiment will be described. First, the on-off valves 12, 14, 15, 23, 26, 29, and 35 are opened and the on-off valves 16, 27, and 34 are closed, and the system control unit 10 is connected to the pressure gauge 21 in the circuit on the compressor air supply side. The operation of the liquid feed pump 13 and the gas-liquid mixer 24 is controlled while referring to the measured value of the air flow meter 22 and the pressure gauge 18 and flow meter 17 of the circuit on the suspension stock solution supply side, and the liquid feed pump 13 The suspension stock solution sent from the raw water tank 11 and the compressor air are mixed by the gas-liquid shearing method to obtain a suspension stock solution mixed with fine bubbles, and it is fed into the pressurized tank 25. Here, the pressurized tank 25 is maintained at a constant high pressure by controlling the exhaust solenoid valve 28, and when the suspension stock solution is fed in a state in which fine bubbles are mixed as described above, The fine bubbles easily dissolve in the suspension stock solution by the self-pressurizing effect, and become a solution in which air is dissolved to a supersaturated state.

  Since the pressurized tank 25 is maintained at a constant high pressure, the suspension stock solution is pumped to the filter body 31. In this case, the suspension stock solution is introduced into the filtration chamber 43 through the injection hole 47, and the filtration chamber 43 passes through the drainage holes 48a and 48b and the open / close valve 35 from the water passage layers of the filter cloths 45a and 45b and the nets 44a and 44b. Since the air is in communication with the outside, the pressure is lower than that in the pressurized tank 25, and the air dissolved in the suspension stock solution again becomes fine bubbles and appears in the liquid.

  Therefore, in the filter body 31, pressure filtration is performed on the suspension stock solution in which fine bubbles are mixed, and the filtration state after a certain amount of time has been shown in an enlarged sectional view near the filter cloth. And as shown in FIG. In the figure, 61 is a suspension stock solution in which generated fine bubbles are mixed, and 62 is a deposition layer of suspended particles adhering to the filter cloth 45a (45b). In this case, the filter cloth 45a (45b) is applied with a flat membrane MF (microfiltration) membrane capable of removing suspended particles of 0.1 (μm) or more, does not employ the body feed method, and performs pre-coating. Instead, the suspension stock solution is filtered from the beginning.

  On the other hand, the fine bubbles in the suspension stock solution have a bubble size distribution peak around 10 (μm), the number is more than several thousand (pieces / ml), and the suspension stock solution is white and cloudy. It has become. In this state, since the fine bubbles are negatively charged, they repel each other and maintain the dispersed state, but some of them adhere to the positively charged suspended particles. Therefore, the suspended particles move so as to be attracted to the filter cloth 45a side with the fine bubbles attached, but in the initial stage, only the fine bubbles are trapped on the surface of the filter cloth 45a (45b) and the net 44a (44b) together with the liquid. ) When passing through the water-passing layer on the side and the sedimentation layer 62 of suspended particles is gradually formed on the surface of the filter cloth 45a (45b), the suspended particles are caught on the surface of the deposition layer 62, and fine bubbles are generated. Only water and water flow to the filter cloth 45a (45b) side through the passage of fine bubbles adhering to the suspended particles previously deposited. Further, since the movement speed of fine bubbles in the low pressure direction [filter cloth 45a (45b) side] is generally faster than that of suspended particles or water, fine bubbles that are not attached to the suspended particles enter the deposition layer 62 from the initial stage. It is taken into the passing passage that is formed and plays the role of maintaining the passage. In other words, even if the deposited layer 62 becomes thick, a large number of flow paths are secured in the layer, so that the filtration operation can proceed without reducing the filtration efficiency.

  By the way, the deposited layer 62 of suspended particles becomes thicker as the filtration progresses. However, due to the action of the fine bubbles as described above, as shown in FIG. The flow paths 63 are configured vertically and horizontally like ant nests, and fine bubbles and water alternately flow through the flow paths 63. The fine bubbles flowing through the flow path 63 of the deposition layer 62 may lose their charge and combine with other fine bubbles, and the pressure becomes lower as the filter cloth 45a is closer, so the fine bubbles in each flow path 63 Tends to grow gradually. Accordingly, the deposited layer 62 is configured to be relatively fragile, and when it becomes thicker, it peels and collapses due to its own weight, and stays as a slurry at the bottom of the filtration chamber 43.

  Based on the filtration mechanism described above, the filtration device controls the slurry discharge solenoid valve 32 and the exhaust solenoid valve 33 in the procedure shown in the flowchart of FIG. However, the system control unit 10 closes the electromagnetic valves 32 and 33 in the normal state. First, when a liquid to be filtered, in which air is dissolved in a suspension stock solution (polishing waste liquid) to a supersaturated state, is injected from the pressure tank 25 into the filtration chamber 43 of the filter body 31, it dissolves in the filtration chamber 43 as described above. The air that has come out becomes fine bubbles and is mixed in the suspension stock solution, but the system control unit 10 has confirmed from the detection signal of the pressure gauge 30 that the injection pressure Pin has become a predetermined value Po or more. The filtration chamber 43 is filled with the liquid to be filtered and the state is changed to a steady filtration state, and the timers Ts and Ta are started (S1 to S3).

  When the measurement time ts of the timer Ts becomes equal to or longer than the predetermined time THs, the solenoid valve 32 is opened for a certain time (S4, S5). When the opening is completed, the solenoid valve 32 is returned to the closed setting, the measurement time ts of the timer Ts is set to 0, and the timer Ts is started again to check whether or not the predetermined time THs is reached (S5). , S6 → S4). That is, as described above, the suspended particle deposition layer 62 peels and collapses to form a slurry and accumulates at the bottom of the filtration chamber 43, so that it is discharged to the outside every predetermined time THs.

  The system control unit 10 confirms whether or not the measurement time ta of the other timer Ta is equal to or longer than the predetermined time THa, and when it exceeds the predetermined time THa, the electromagnetic valve 33 is opened for a predetermined time and the filtration chamber is opened. The air staying in the upper part of 43 is discharged to the outside, and the measurement time ta of the timer Ta is set to 0, and the timer Ta is started again to check whether or not the predetermined time THa is reached again. The operation is repeated [(S4) → S7 to S9 → (S4)]. That is, although the fine bubbles have a very small volume, the rising speed is slow, but the air is collected little by little at the top of the filtration chamber 43 while the filtration operation is performed for a long time, so that the air is stored in a predetermined amount. It discharges to the outside every time THa.

  In this embodiment, the solenoid valves 32 and 33 are controlled to be opened and closed by time management. A sensor for detecting that air has accumulated in the vicinity of the uppermost part in the filtration chamber 43 is provided with a slurry in the vicinity of the lowermost part. It is also possible to provide a sensor for detecting that the gas is staying, and to perform opening / closing control based on the detection signal of each sensor. Further, according to the filtration mechanism described above, although the electromagnetic valves 32 and 33 are open for a short time, the pressure in the filtration chamber 43 is reduced, which also promotes the separation and collapse of the deposited layer 62. Is done.

  As described above, according to the filtration device of this embodiment, the fine bubbles are mixed in the suspension stock solution, so that the particles by the suspended particles accumulated on the filter cloths 45a and 45b can be obtained without using a filter aid. High-efficiency filtration that does not cause clogging can be performed. In addition, the filter 31 can be continuously operated for a long time without washing in a state where the filter 31 is opened. This filtration device can also perform reverse cleaning using compressor air. In FIG. 1, the on-off valves 26 and 35 and the solenoid valves 32 and 33 are closed, and the on-off valves 27 and 34 are opened to open the drain holes. When compressor air is supplied from 48a and 48b to the water flow layer, the filter cloths 45a and 45b are back-washed, and the suspension stock solution expelled from the filtration chamber 43 is drained through the on-off valve 27.

[Embodiment 2]
This embodiment is obtained by further improving the filtration device of the first embodiment, and its main part is shown in FIG. A feature of this filtration device is that a flow meter 71 is provided in the pressure feed path of the liquid to be filtered to the injection hole 47 of the filter body 31, and an ejector 72 is provided on the drain side of the filtrate water, and is discharged through the ejector 72 and filtered. By circulating the filtered water stored in the water tank 73 to the ejector 72 by the liquid feed pump 74, the filtered water sent from the drain holes 48a and 48b of the filter body 31 is forcibly sucked by the ejector 72. It is in the point.

  The system control unit 10 executes the control procedure shown in the flowchart of FIG. 6 while confirming the flow rate detection signal obtained from the flow meter 71. First, when the liquid to be filtered is injected from the pressure tank 25 into the filtration chamber 43 of the filter body 31 and it is confirmed from the pressure detection signal of the pressure gauge 30 that the injection pressure Pin is equal to or higher than the predetermined value Po. It is the same as in the case of Embodiment 1 that 43 is filled with the liquid to be filtered and the state is shifted to a steady filtration state (S21, S22).

  Here, the system control unit 10 constantly checks whether or not the detected value Fv of the flow meter 71 is equal to or less than a predetermined threshold value THv1 from that point of time, and activates the liquid feed pump 74 if the condition (Fv ≦ THv1) is satisfied. Then, suction of filtered water by the executor 72 is started (S23, S24). The threshold value THv1 in this case corresponds to the flow rate threshold value when the sedimentation layer 62 of the suspended particles on the filter cloths 45a and 45b is thick and the filtration efficiency is lowered. The pressure on the drain side of the filtrate is lowered to lower the pressure of the water passage layer in the filtration chamber 43, thereby forcibly causing separation / collapse of the deposited layer 62. That is, when the pressure of the water flow layer formed by the nets 44a and 44b behind the filter cloths 45a and 45b is reduced, the fine bubbles and the water are caused to flow through the flow path 63 formed inside the deposition layer 62. At the same time, the fine bubbles tend to expand due to the reduced pressure, causing the deposited layer 62 to collapse from the inside and easily peel off.

  On the other hand, the large pressure reduction of the water flow layer causes the above-mentioned effect, but if the large pressure reduction state is continued thereafter, the suspended particles and the fine bubbles are always strongly attracted to the filter cloth 45a, 45b side, and the deposited layer 62 is crushed. Therefore, the flow path 63 is hardly formed inside the deposition layer 62, and the filtration efficiency is lowered. Therefore, when the detected value Fv of the flow meter 71 recovers to a predetermined threshold value THv2 or more due to the separation / collapse of the deposited layer 62, the system control unit 10 immediately stops the liquid feed pump 74 and stops the suction of filtered water by the executor 72. , Thereby returning to the normal compression filtration state (S25, S26). Note that the threshold value THv2 is sufficiently larger than the threshold value THv1.

  Then, the system control unit 10 repeatedly executes the start / stop control procedure of the executor 72 according to the procedure (S23 to S26), so that only the natural separation / collapse of the deposited layer 62 in the filtration process as in the first embodiment. Rather than relying on it, it is possible to forcibly peel and collapse the deposited layer 62 to maintain higher filtration efficiency more stably. In addition, although the processing procedure (FIG. 3) of slurry discharge / air discharge by time management shown in Embodiment 1 is executed in parallel, in this case, the filtration efficiency is further improved and the slurry is placed at the bottom of the filtration chamber 43. The threshold value THs related to the measurement time ts of the timer Ts at which the accumulation speed is high is set smaller than that in the first embodiment.

[Embodiment 3]
This embodiment relates to the filtration device of the vacuum filtration method, while the first and second embodiments are the filtration device of the pressure filtration method, and a schematic configuration diagram thereof is shown in FIG. However, the gas-liquid mixing processing circuit and the like in the preceding stage of the pressure tank 25 in the filtration device (FIG. 1) of the first embodiment are applied to the device of this embodiment as it is. However, in this embodiment, when a liquid to be filtered in which fine bubbles are mixed in the suspension stock solution is obtained by the gas-liquid mixer 24, it is immediately sent to the filtration chamber 43 of the filter 31 and injected. Therefore, although the liquid to be filtered is not pumped, the compressor air and the suspension stock solution are each sent to the gas-liquid mixer 24 at a predetermined pressure, so that the liquid to be filtered is at least at a pressure larger than atmospheric pressure in the filtration chamber It is sent to 43.

  On the other hand, on the drain side of the filtered water from the filter body 31, as in the case of the second embodiment, a suction pressure reducing part in the circulating system of filtered water comprising an ejector 72, a filtered water tank 73 and a liquid feed pump 74 is provided. It has been. Then, the system control unit 10 controls the liquid feed pump 74 according to the procedure shown in FIG. First, when the liquid to be filtered, in which fine bubbles are mixed in the suspension stock solution, is injected into the filtration device, the liquid feed pump 74 is activated to cause the ejector 72 to pass the filtered water at a high speed, and the pressure on the filtered water discharge side is reduced. Thus, the pressure of the water passage layer in the filtration chamber 43 is reduced (S31, S32).

  As a result, the filtration target liquid is taken into the filtration chamber 43 of the filter body 31 and the injection pressure Pin indicated by the pressure gauge 30 in a state where the filtration chamber 43 is filled is a substantially constant value (a pressure value larger than the atmospheric pressure). Although it becomes stable, the state is nothing but the beginning of steady vacuum filtration (S33). Even in the reduced-pressure filtration state, high-efficiency filtration with separation and collapse of the deposited layer 62 is performed by the filtration mechanism described with reference to FIG. 4, but the filtration to the filter cloths 45a and 45b is performed by the progress of filtration. The accumulated layer 62 of suspended particles gradually increases in thickness, and eventually the filtration efficiency decreases.

  Therefore, the system control unit 10 always confirms the detection value Fv of the flow meter 17 from the time when the injection pressure Pin is stabilized at a substantially constant value, and if the detection value Fv falls below the predetermined threshold THv1, the filtration efficiency decreases. As a result, the liquid feed pump 74 is driven more strongly than in the normal vacuum filtration state to increase the suction force by the ejector 72 (S34, S35). This increase in suction force corresponds to the state in which the liquid feed pump 74 is activated and the ejector 72 is activated in the case of the second embodiment. In this embodiment, the water-permeable layer is at a depressurization level as an offset in advance. Therefore, the pressure is further reduced. Therefore, as in the case of the second embodiment, not only the natural peeling / collapse of the deposited layer 62 by a normal filtration mechanism but also the deposited layer 62 can be forcibly peeled / collapsed to maintain high filtration efficiency. it can.

  As a result, the filtration efficiency increases, and when the detected value Fv of the flow meter 17 recovers and exceeds the predetermined threshold THv2, the liquid feed pump 74 is returned to the original driving state, and the ejector 72 is adapted to the normal vacuum filtration state. Set to suction pressure (S36, S37). Accordingly, returning to the normal filtration mechanism, the system control unit 10 enters a confirmation state as to whether or not the detected value Fv of the flow meter 17 is equal to or less than the predetermined threshold value THv1, and thereafter, the steps S34 to S37 are repeatedly executed. (S34 to S37 → S34). Note that the slurry discharge / air discharge processing procedure (FIG. 3) based on time management is also executed in the same manner as in the second embodiment. That is, although it is basically based on the vacuum filtration method, the inside of the filtration chamber 43 is maintained at a pressure higher than the atmospheric pressure, so that slurry discharge / air discharge is performed in the same manner as in the first and second embodiments. Can be done.

  According to the filtration device of the third embodiment, since it is a vacuum filtration, the pressurized tank 25 is not required as in the first and second embodiments, and the peeling / collapse of the deposited layer 62 is forcibly caused. Since the change in the pressure reduction level of the water passage layer is only required to drive the liquid feed pump 74, there is an advantage that the system can be downsized. 7A, the liquid to be filtered obtained by the gas-liquid mixer 24 is directly sent to the filtration chamber 43 of the filter 31. As shown in FIG. Circulation in which a storage tank 75 for the target liquid is provided, and fine bubbles are mixed into the storage tank 75 by the gas-liquid mixer 77 with respect to the storage liquid pumped from the lower side of the storage tank 75 by the liquid feed pump 76. The path is configured, the inside of the storage tank 75 is stirred by the stirrer 78, and the mixing concentration of the fine bubbles in the liquid to be filtered is kept uniform, and the liquid to be filtered in the storage tank 75 is filtered by the liquid feed pump 79 on the filter 31 side. You may make it send to.

[Embodiment 4]
This embodiment relates to a modification of the filter body. In the first to third embodiments, as shown in FIG. 2, a filter body 31 is used in which a hollow portion corresponding to a shape in which a quadrangular pyramid is joined to the upper side surface and the lower side surface of a rectangular parallelepiped is used as the filter chamber 43. . As described in the first embodiment, this is because the air pool formed by rising fine bubbles remaining in the filtration chamber 43 and the slurry formed by the separation and collapse of the deposited layer 62 are separated from the uppermost portion and the uppermost portion of the filtration chamber 43, respectively. This is because it is convenient to collect at the bottom. From this point of view, the filter 80 shown in FIG. 9 [(A) is a cross-sectional view, (B) is a cross-sectional view taken along the line XX of (A) (filter cloth is omitted)] has a circular filter chamber. It is comprised as a plate-shaped hollow part and can implement | achieve the said function rationally.

  In FIG. 9, 81 and 82 are disc bodies whose central region is formed as a disk-shaped recess, 83 is a filtration chamber, 84 a and 84 b are nets forming a water-permeable layer, 85 a and 85 b are filter cloths, and 86 is a seal. Member, 87 is an injection hole for the liquid to be filtered, 88a and 88b are drainage holes for filtered water, 89a and 89b are air discharge holes, 90a and 90b are slurry discharge holes, and the plate bodies 81 and 82 are joined together. A disk-shaped space constituted by the recesses is defined as a filtration chamber 83, and filter cloths 85a and 85b are provided on the inner wall surfaces corresponding to the bottom surfaces of the recesses in the filtration chamber 83 with nets 84a and 84b interposed therebetween. It is set up. However, the filter cloths 85a and 85b are lined on the entire inner surface of the filtration chamber 83, and the peripheral edge portions are sandwiched between the joint surfaces of the respective plate bodies 81 and 82. As for the joining mechanism of each panel 81, 82, as in the case of the filter 31 shown in FIG. 2, the bolts and nuts are tightened using the holes provided in the peripheral edge of each panel 81, 82. Or a system in which one panel 81 is fixed and the other panel 82 is pressed by a hydraulic cylinder or the like.

  Since the filter body 31 of FIG. 2 is configured as a joined body of the respective board bodies 41 and 42, the air discharge holes 49a and 49b and the slurry discharge holes 50a and 50b can be formed at the uppermost part and the lowermost part of the filtration chamber 43. Therefore, it must be formed in the vicinity of the uppermost part and the lowermost part. In that case, the filter cloths 45a and 45b are pressed by the flange nuts at the openings of the discharge holes 49a, 49b, 50a, and 50b on the filtration chamber 43 side, so that even if they are in the vicinity, As a result, the air above the air discharge holes 49a and 49b does not escape to the outside, and the slurry below the slurry discharge holes 50a and 50b does not escape to the outside. .

  According to the filter body 80 of this embodiment, the air discharge holes 89a and 89b and the slurry discharge holes 90a and 90b can be formed at the uppermost part and the lowermost part of the filtration chamber 83, respectively. The pool and slurry pool can be completely discharged to the outside based on the solenoid valve control procedure of FIG. Furthermore, since the recesses of the disc bodies 81 and 82 are disk-shaped, processing is easier than the disc bodies 41 and 42 in FIG. 2, and there are corners when the filter cloths 85a and 85b are spread. There is an advantage that it becomes easy to not.

  Further, in the above embodiment, the filter body having a single filtration chamber has been described. However, the filter body is provided with a number of filtration chambers in which the plate bodies are stacked and the injection holes for the suspension stock solution communicate with each other like a filter press mold. A configuration can also be adopted. For example, as shown in FIG. 10, the plate bodies 41 and 42 used in the filter body 31 (FIG. 2) of the first embodiment are used as the plate bodies at both ends, and three connecting plate bodies 95 are interposed between them. Thus, a filter body having four filter chambers can be obtained. Here, the connection board 95 has the same configuration of each facing surface as the board 41 of the first embodiment, and the hole corresponding to the injection hole 47 allows the suspension stock solution to pass therethrough. The hole 97 corresponding to the drainage hole 48a communicates with the water-passing layer of each opposing surface, and has a configuration in which a drainage channel communicating with the lower end surface is formed in the middle of the hole 97 corresponding to the drainage hole 48a. It has become. The connecting plate body 95 is also configured to correspond to the air discharge holes 49a, 49b and the slurry discharge holes 50a, 50b of the plate bodies 41, 42.

  And when actually applied to the filtration device, the suspension stock solution is injected from the injection hole 47, and pressure filtration or vacuum filtration using four filtration chambers at the same time is performed. The control described in the first, second, and third embodiments can be performed collectively by the system control unit 10 for all the filtration chambers. However, the solenoid valves for air exhaust and slurry discharge may be performed in units of individual filtration chambers.

  The present invention can be applied to a filtration apparatus using pressure filtration or vacuum filtration.

It is a schematic block diagram of the filtration apparatus of Embodiment 1. (A) is sectional drawing of a filter body, (B) is XX arrow sectional drawing in (A) (however, a filter cloth is abbreviate | omitted). It is a flowchart which shows the control procedure of the solenoid valve for slurry discharge | emission connected to the filter body, and the solenoid valve for exhaust_gas | exhaustion. It is an expanded sectional view of a filtration part for explaining filtration action. It is a schematic block diagram of the filtration apparatus (only the principal part) of Embodiment 2. It is a flowchart which shows the control procedure of a pressure reduction drive part (ejector pump). (A) is a schematic block diagram of the filtration apparatus of Embodiment 3. FIG. (B) is a figure which shows the other structural example of the part which produces | generates the filtration object liquid, and sends to a filter body. It is a flowchart which shows the control procedure of a pressure reduction drive part (ejector pump). (A) is sectional drawing of the filter body which concerns on Embodiment 4, (B) is XX arrow sectional drawing in (A) (however, a filter cloth is abbreviate | omitted). It is sectional drawing of the filter body at the time of laminating | stacking a board body and comprising a some filtration chamber.

Explanation of symbols

10 ... System control unit, 11 ... Raw water tank, 12 ... Open / close valve, 13 ... Liquid feed pump, 14-16 ... Open / close valve, 17 ... Flow meter, 18 ... Pressure gauge, 19 ... Check valve, 20 ... Pressure reducing valve, 21 ... Pressure gauge, 22 ... Air flow meter, 23 ... Open / close valve, 24 ... Gas-liquid mixer, 25 ... Pressurized tank, 25a ... Liquid level gauge, 26, 27 ... Open / close valve, 28 ... Exhaust solenoid valve, 29 ... Open / close valve, 30 ... Pressure gauge, 31 ... Filter body, 32 ... Solenoid discharge solenoid valve, 33 ... Exhaust solenoid valve, 34, 35 ... Open / close valve, 41, 42 ... Board body, 43 ... Filtration chamber, 44a, 44b ... Net, 45a, 45b ... Filter cloth, 46 ... Sealing member, 47 ... Injection hole, 48a, 48b ... Drainage hole, 49a, 49b ... Air discharge hole, 50a, 50b ... Slurry discharge hole, 61 ... Mixed bubbles Suspended undiluted liquid, 62 ... Sedimentation layer of suspended particles, 63 ... Flow path of fine bubbles and liquid, 71 ... Flow meter, 72 ... Ejector, 73 ... Filtration water tank, 74 ... Liquid feed pump, 75 ... Storage tank 76 ... Liquid feed pump, 77 ... Gas-liquid mixer, 78 ... Stirrer, 79 ... Liquid feed pump, 80 ... Filter body, 81, 82 ... Board body, 83 ... Filtration chamber, 84a, 84b ... Net, 85a, 85b ... Filter cloth, 86 ... Seal member, 87 ... Injection hole, 88a, 88b ... Drain hole, 89a, 89b ... Air Discharge holes, 90a, 90b ... slurry discharge holes, 95 ... connecting body, 96 ... communication holes, 97 ... drainage holes.

Claims (12)

  In the filtration method of the suspension stock solution by pressure filtration or reduced pressure filtration, the filtration method is characterized by performing filtration in a state where fine bubbles are mixed in the suspension stock solution.   The filtration method according to claim 1, wherein gas is dissolved in the suspension stock solution under high pressure, the suspension stock solution in which the gas is dissolved is poured into a filtration chamber, and filtration is performed by generating fine bubbles in the suspension stock solution in the filtration chamber. .   The filtration method according to claim 1, wherein a process of mixing fine bubbles into the suspension stock solution by gas-liquid mixing means is performed, and the suspension stock solution after the treatment is injected into a filtration chamber to perform filtration.   The filtration surface is configured in the vertical direction, and filtration is performed while measuring the flow rate of the liquid to be filtered, and when the measured flow rate is reduced, the pressure downstream from the filtration surface is reduced. The filtration method according to claim 2 or claim 3. A filtration chamber in which a filter medium is mounted on a vertical inner wall surface with a water-permeable layer interposed; an injection hole for injecting a liquid to be filtered from the outside into the filtration chamber; and filtered water from the water-permeable layer A filter body in which a drainage hole for discharging the water to the outside is formed,
Stock solution processing means for producing a liquid to be filtered by dissolving gas in the suspension stock solution under high pressure or by mixing fine bubbles in the suspension stock solution by gas-liquid mixing processing,
A filtration apparatus comprising: a pressure feeding means for pressure feeding the liquid to be filtered generated by the stock solution treatment means to the filtration chamber through an injection hole of the filter body.   The flow rate detecting means for detecting the flow rate of the suspension stock solution pumped by the pressure feeding means, and the pressure on the drain hole side of the filter body is reduced when the detected flow rate value by the flow rate detecting means becomes a predetermined value or less. The filtration apparatus according to claim 5, further comprising a decompression unit. A filtration chamber in which a filter medium is mounted on a vertical inner wall surface with a water-permeable layer interposed; an injection hole for injecting a liquid to be filtered from the outside into the filtration chamber; and filtered water from the water-permeable layer A filter body in which a drainage hole for discharging the water to the outside is formed,
Stock solution processing means for generating a liquid to be filtered by dissolving gas in the suspension stock solution under high pressure or by mixing fine bubbles into the suspension stock solution by gas-liquid mixing processing,
Liquid feeding means for sending the liquid to be filtered generated by the stock solution processing means to the filtration chamber through the injection hole of the filter body at a pressure larger than atmospheric pressure;
And a pressure reducing means for suctioning filtered water from the discharge hole of the filter body.   A flow rate detecting means for detecting the flow rate of the suspension stock solution sent by the liquid feeding means is provided, the pressure reducing means is a variable pressure reducing means capable of changing the pressure reduction level, and a flow rate value detected by the flow rate detecting means is a predetermined value. If larger, the decompression level by the variable decompression means is set to the first decompression level for decompression filtration, and when the detected flow rate value is not more than a predetermined value, the first decompression level is exceeded. The filtration device according to claim 7, further comprising a decompression control means for setting the second decompression level to a lower level.   A slurry discharge hole leading to the outside is formed at or near the lowermost part of the filtration chamber of the filter body, and a first on-off valve is connected to the slurry discharge hole. Or the filtration device according to claim 8.   A gas discharge hole that leads to the outside is formed in the uppermost part of the filtration chamber of the filter body or in the vicinity thereof, and a second on-off valve is connected to the gas discharge hole. The filtration device according to claim 8 or 9.   The filtration chamber of the filter body is configured as a hollow portion corresponding to a shape in which a quadrangular pyramid is joined to an upper side surface and a lower side surface of a rectangular parallelepiped, 5, 6, 7, 8, The filtration device according to claim 9 or 10.   The filter chamber of the filter body is configured as a disk-shaped hollow portion, and the filter chamber according to claim 5, claim 6, claim 7, claim 8, claim 9, claim 10, or claim 11. Filtration equipment.

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