Cleaning method for a downward flow filtration system and a downward flow filtration system

Abstract

The present invention provides a cleaning method for a downward-flow type filtration system and a downward-flow type filtration system that can promote the detachment of the filter media layer during cleaning of the filtration tank. [Solution] The cleaning method for a downward flow type filtration device involves supplying gas 25 from below the filter media layer 12 to one of the compartments 40 into which the inside of a filtration tank 11, which has a filter media layer 12 formed of amorphous filter media, is divided, and the compartment 40 to which the gas 25 is supplied is changed sequentially, so that the compartment 40 to which the gas 25 is first supplied at the start of cleaning is different from the compartment 40 to which the gas was first supplied at the start of the previous cleaning.

Description

Technical Field

[0001] The present disclosure relates to a method for cleaning a downward flow filtration device and a downward flow filtration device.

Background Art

[0002] Patent Document 1 discloses a filtration device in which a filtrate inlet pipe, a treatment liquid outlet pipe, a cleaning water inlet pipe, and a filter medium support plate are respectively arranged in a filtration tank body. A fibrous filter medium is laminated on the filter medium support plate, thereby forming a filter medium layer. A partition plate is attached to the lower surface of the filter medium support plate. The partition plate divides the lower surface of the filter medium support plate into a plurality of sections. A cleaning air inlet pipe is arranged in each section.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a downward flow filtration device, a filter medium layer is formed by laminating (depositing) amorphous filter media such as resin filter media and fiber filter media on a filter. While the filter medium layer is subjected to a strong pressure from above during the passage of the stock solution, its downward movement is restricted by the filter, so it is consolidated downward. For this reason, a part of the filter medium layer is likely to adhere to peripheral members such as the inner wall of the filtration tank and the filter, and it becomes difficult to peel off and stir the filter medium layer during cleaning in the filtration tank.

[0005] In view of such circumstances, the present disclosure has been made, and an object thereof is to provide a method for cleaning a downward flow filtration device and a downward flow filtration device capable of promoting the peeling of the filter medium layer during cleaning in the filtration tank.

Means for Solving the Problems

[0006] A cleaning method for a downward-flow type filtration apparatus according to a first aspect of this disclosure involves supplying gas from below the filter media layer in one of the circumferentially divided compartments within the filtration tank, in a filtration tank having a filter media layer formed of amorphous filter media, and sequentially changing the compartment to which the gas is supplied. Furthermore, the compartment to which the gas is first supplied at the start of cleaning is different from the compartment to which the gas was first supplied at the start of the previous cleaning.

[0007] A downward flow filtration apparatus according to a second aspect of the present disclosure comprises a filtration tank, a filter media layer provided in the filtration tank and formed of amorphous filter media, a gas supply passage capable of supplying gas from below the filter media layer in each of the circumferentially divided compartments within the filtration tank, and a control unit that controls the supply of the gas to any of the compartments via the gas supply passage, and the sequential change of the compartment to which the gas is supplied. The control unit sets a compartment to which the gas is first supplied at the start of the previous cleaning, which is different from the compartment to which the gas was first supplied at the start of the previous cleaning. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a cleaning method for a downward-flow type filtration apparatus and a downward-flow type filtration apparatus that can promote the peeling of the filter media layer when cleaning the inside of the filtration tank. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram showing the configuration of the filtration device according to this embodiment. [Figure 2] This is a top view of an example of a gas introduction unit according to this embodiment. [Figure 3A] This is a diagram illustrating the filtration process using a filtration device. [Figure 3B] This is a diagram illustrating the filtration process using a filtration device. [Figure 3C] This is a diagram illustrating the filtration process using a filtration device. [Figure 3D] This is a diagram illustrating the filtration process using a filtration device. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described below with reference to the drawings. In each figure, common parts are denoted by the same reference numerals, and redundant explanations are omitted. For the sake of explanation, the vertical direction is defined as the Z direction, and the Z direction is, for example, the central axis when the filtration tank 11 is formed in a cylindrical shape.

[0011] Figure 1 is a diagram showing the configuration of the filtration device 10 according to this embodiment. As shown in Figure 1, the filtration device 10 according to this embodiment comprises a filtration tank 11, a filter media layer 12, a raw liquid supply passage 13, a gas supply passage 14, a washing water supply passage 15, and a control unit 16 composed of a computer or the like. The raw liquid 23 is supplied from the upper part 11a of the filtration tank 11 via the raw liquid supply passage 13 by a water pump (not shown). The raw liquid 23 is then filtered by the filter media layer 12 and discharged from the lower part 11b of the filtration tank 11 via the discharge passage 17. In this way, the raw liquid 23 is filtered as it flows from the top to the bottom of the filtration tank 11. That is, the filtration device 10 according to this embodiment is a downward flow type filtration device.

[0012] The filtration tank 11 is, for example, a cylindrical container extending in the Z direction. The upper part 11a of the filtration tank 11 is provided with a raw liquid supply passage 13 for supplying the raw liquid 23 into the filtration tank 11. On the other hand, the bottom of the filtration tank 11 is provided with a discharge passage 17 for discharging the processed liquid 24, which has been filtered from the raw liquid 23, from the filtration tank 11.

[0013] The wash water supply channel 15 is connected to the stock solution supply channel 13 via the third valve 33. The wash water supply channel 15 is also connected to the discharge channel 17 via the fourth valve 34. The wash water 26 flowing through the wash water supply channel 15 is supplied to the filtration tank 11 via the stock solution supply channel 13 or the discharge channel 17 by opening and closing the third valve 33 and the fourth valve 34. In other words, the stock solution supply channel 13 and the discharge channel 17 also serve as a part of the wash water supply channel 15. The wash water 26 is pumped under pressure by a water pump M connected to the upstream side of the wash water supply channel 15.

[0014] The stock solution supply path 13 and the discharge path 17 are connected by a connection path 18 provided with a fifth valve 35. The connection point between the stock solution supply path 13 and the connection path 18 is located between the first valve 31 and the third valve 33 and the filtration tank 11. On the other hand, the connection point between the discharge path 17 and the connection path 18 is located on the downstream side of the second valve 32 provided in the discharge path 17.

[0015] An exhaust path 19 for discharging the gas supplied for cleaning is connected to the upper part 11a of the filtration tank 11. An eighth valve 38 is provided in the exhaust path 19.

[0016] A filter 20 is provided in the lower part 11b in the filtration tank 11. The filter 20 is a so-called net, which prevents the outflow of the filtering material downward. Therefore, the filtering material layer 12 is formed by the deposition of the filtering material on the filter 20 and consolidation accompanying the passage of the liquid.

[0017] The filtering material is composed of a material capable of capturing the suspended substances contained in the stock solution 23 while maintaining a gap through which the stock solution 23 can pass. The filtering materials are only densely packed and are not fixed by adhesion or the like so that the filtering material layer 12 is separated into independent filtering materials during cleaning.

[0018] Each filtering material is formed of, for example, an amorphous filtering material. In any case, the amorphous filtering material has a specific gravity of 1.0 or more so as to be deposited on the filter 20. The material and shape of the amorphous filtering material are arbitrary as long as the desired filtering performance can be obtained. For example, the amorphous filtering material is formed in a块状 shape so as to have a large number of voids inside, with a large number of wavy fibers adhered or welded to each other.

[0019] Below the filter 20 in the filtration tank 11, a gas introduction part 21 connected to the gas supply path 14 is provided. The gas introduction part 21 is installed for each partition 40 that divides the internal space of the filtration tank 11 into a plurality of parts. The partition 40 divides the internal space into, for example, two left and right spaces as the partition 40A and the partition 40B. In this case, the gas supply path 14 is connected to the gas introduction part 21A of the partition 40A via the sixth valve 36. Similarly, the gas supply path 14 is connected to the gas introduction part 21B of the partition 40B via the seventh valve 37. Note that an air blower (not shown) is connected to the upstream side of the gas supply path 14.

[0020] Hereinafter, this embodiment will be described by taking an example in which two partitions 40A and 40B are set. FIG. 2 is a top view of an example of the gas introduction part according to this embodiment. Each of the gas introduction parts 21A and 21B includes a plurality of gas introduction pipes 22 having a plurality of supply holes 22a. The gas introduction pipes 22 are arranged in parallel at a predetermined interval within, for example, one partition. Also, any of the gas introduction pipes 22 is arranged horizontally. The supply holes 22a are formed at intervals in the extending direction of each gas introduction pipe 22. The attachment direction of the supply holes 22a can be appropriately set, such as downward. The gas (for example, air) supplied from the gas supply path 14 to the gas introduction pipe 22 is introduced into the internal space of the filtration tank 11 through the supply holes 22a.

[0021] FIG. 1 is a diagram for explaining the filtration process by the filtration device 10. The opening and closing of the first valve 31 to the eighth valve 38 are all controlled by the control part 16. First, the first valve 31 of the stock solution supply path 13 connected to the upper part 11a of the filtration tank 11 and the second valve 32 of the discharge path 17 connected to the bottom of the filtration tank 11 are opened, and the other valves are closed. The stock solution 23 to be filtered is supplied from the stock solution supply path 13 to the filtration tank 11, and when it contacts the filter material layer 12, the impurities are captured by the filter material. The treatment liquid 24 that has passed through the filter material layer 12 flows out from the discharge path 17.

[0022] As the filtration process continues, impurities accumulate in the filter media layer 12. Due to the accumulation of impurities, the efficiency of the raw liquid 23 passage gradually deteriorates, and the amount of raw liquid 23 to be filtered decreases. Therefore, the process moves to a washing stage according to predetermined conditions (for example, a predetermined time, a pressure increase, etc.).

[0023] Figures 3A to 3D are diagrams illustrating the cleaning method according to this embodiment. Gas 25 is supplied from below the filter media layer 12 to one of the compartments 40 into which the inside of the filtration tank 11 is divided. Next, the compartment 40 to which the gas 25 is supplied is changed sequentially. For example, if the internal space of the filtration tank 11 is divided into two compartments 40A and 40B on the left and right, the compartment 40 to which the gas 25 is supplied is switched alternately. Also, the compartment 40 to which the gas 25 is first supplied at the start of cleaning is different from the compartment 40 to which the gas was first supplied at the start of the previous cleaning.

[0024] Furthermore, while maintaining the supply of gas 25, washing water 26 may be supplied into the filtration tank 11 from below the filter media layer 12 to promote the swirling flow generated by the gas 25. In addition, the supply of washing water 26 may be switched from below the filter media layer 12 to above the filter media layer 12 to reverse the swirling flow and perform so-called backwashing. In other words, by controlling the direction of the flow of washing water 26, the swirling flow may be increased and the stirring strength may be improved.

[0025] In the initial stage of the cleaning process, the adhering filter media on the gas supply side is roughly detached. At this time, cleaning water 26 is supplied from below in accordance with the flow direction of the gas 25. In the middle stage of the cleaning process, the intensity of the downward swirling flow is increased near the inner wall surface 11c on the gas supply side of the filtration tank 11 and the inner wall surface 11c on the opposite side, detaching the filter media adhering to the inner wall surface 11c on the opposite side. Specifically, while the downward swirling flow is directed against the inner wall surface 11c, turbulence is generated by the collision of the downward swirling flow with the upward flow created by the gas supply, and the generated turbulence is directed horizontally against the inner wall surface 11c. In the later stage of the cleaning process, after the filter media is agitated, the impurities that have passed through the filter 20 and settled at the bottom of the filtration tank 11 are discharged from the discharge passage 17.

[0026] An example of the cleaning method according to this embodiment will be explained with reference to Figures 3A to 3D. Backwashing of the filtration tank 11 with cleaning water 26 is performed as described below.

[0027] First, at the beginning of the washing process, as shown in Figure 3A, the supply of the stock solution 23 is stopped by closing the first valve 31 and the second valve 32. Next, the sixth valve 36 and the eighth valve 38 are opened. This allows the gas 25 to be supplied to the bottom of the filtration tank 11, i.e., below the filter 20, through the gas inlet 21A. The supply of gas 25 from the gas inlet 21A generates a swirling flow CF in the filtration tank 11, which flows upward in section 40A and downward in section 40B. The swirling flow CF mainly causes the filter media layer 12 accumulated in section 40A to break down into individual filter media 12a, and then agitates these dispersed filter media 12a.

[0028] Next, while maintaining the supply of gas 25 to the filtration tank 11, the fourth valve 34 and the fifth valve 35 are opened. This allows the washing water 26 to be supplied to the bottom of the filter media layer 12 in the filtration tank 11 via the discharge passage 17. The washing water 26 promotes the upward flow of the swirling flow CF in section 40A and promotes the collapse of the filter media layer 12 in section 40A. It also improves the agitation intensity in the liquid. The mixture 27 of the washing water 26 and the stock solution 23 is discharged from the filtration tank 11 to the stock solution supply passage 13, passes through the connecting passage 18, and is then discharged.

[0029] Next, as shown in Figure 3B, the sixth valve 36 is closed and the seventh valve 37 is opened. This supplies gas 25 to the bottom of the filtration tank 11 via the gas introduction section 21B. In other words, the section 40 to which gas 25 is supplied is switched. The gas 25 flows mainly from bottom to top within section 40B. As a result, the rotation of the swirling flow CF is reversed. The washing water 26 promotes the upward flow of the swirling flow CF in section 40B, improving the collapse of the filter media layer 12 and the agitation intensity in section 40B.

[0030] The series of steps shown in Figure 3A generate upward swirling flow CF in section 40A and downward swirling flow CF in section 40B, causing the filter media layer 12 in section 40A to collapse. However, in this section, some of the filter media layer 12 that is firmly attached to the inner wall surface 11c of the filtration tank 11 may remain. Also, although some of the filter media layer 12 in section 40B collapses, some of the filter media layer 12 that is firmly attached to the inner wall surface 11c of section 40B and the filter 20 may remain.

[0031] The same can be said for the retention of the filter media layer 12 due to the reverse swirling flow CF. That is, the series of steps shown in Figure 3B generate a downward swirling flow CF in section 40A and an upward swirling flow CF in section 40B, causing the filter media layer 12 to collapse mainly in section 40B. However, in the same section, some of the filter media layer 12 that is firmly attached to the inner wall surface 11c of the filtration tank 11 may remain.

[0032] The filter media 12a that adheres firmly to the inner wall surface 11c and the filter 20 remains there. As a result, new filter media accumulates and increases in volume, and its adhesive force also increases.

[0033] Therefore, in the middle of the washing process, as shown in Figure 3C, the sixth valve 36 is opened again and the seventh valve 37 is closed. Furthermore, the fourth valve 34 is closed and the second valve 32 and the third valve 33 are opened. In other words, the supply of gas 25 is switched from section 40B to section 40A, and the supply destination of the washing water 26 is switched from below the filter media layer 12 to above the filter media layer 12. At this time, the washing water 26 is supplied to the filtration tank 11 from the raw liquid supply passage 13. Due to the switch in the supply destination of gas 25, the swirling flow CF becomes upward in section 40A and downward in section 40B again. That is, the rotation of the swirling flow CF is reversed. In addition, the washing water 26 promotes the downward flow of the swirling flow CF in section 40B and improves the stirring intensity in section 40B. Therefore, the filter media firmly attached to the inner wall surface 11c of section 40B is detached and agitated by the downward swirling flow CF and the turbulence generated by the supply of gas 25 in section 40B.

[0034] Next, as shown in Figure 3D, the sixth valve 36 is closed and the seventh valve 37 is opened. At this time, the supply of washing water 26 from above the filter media layer 12 (i.e., from the raw liquid supply passage 13) is maintained. By switching the supply destination of the gas 25, the swirling flow CF becomes downward in section 40A and upward in section 40B again. In addition, the washing water 26 promotes the downward flow of the swirling flow CF in section 40A and improves the stirring intensity in section 40A. Therefore, the filter media firmly adhering to the vicinity of the inner wall surface 11c of section 40A is detached and stirred by the downward swirling flow CF in section 40A and the turbulence created by the supply of gas 25.

[0035] In the later stages of the washing process, the contaminants removed by the above series of processes are discharged from the discharge passage 17. After the discharge of the contaminants, the process returns to the filtration process. In this embodiment, the section 40 to which gas 25 is initially supplied at the start of washing is different from the section 40 to which gas 25 was initially supplied at the start of the previous washing. For example, if the section 40 to which gas 25 was initially supplied at the start of the previous washing was section 40A, then the section 40 to which gas 25 is initially supplied at the start of the next washing is set to section 40B.

[0036] When backwashing is initiated, supplying gas 25 to section 40A causes the filter media layer 12 in section 40A to primarily collapse. Next, when the supply destination of gas 25 is switched to section 40B, the filter media layer 12 in section 40B primarily collapses. However, when gas 25 is supplied to section 40B, the filter media layer 12 in section 40A, which was the previous supply destination, has already collapsed. Therefore, some of the gas 25 supplied to section 40B flows into section 40A, preventing the filter media layer 12 that has solidified in section 40B from collapsing and making it difficult to detach. If the filtration process is initiated in this state, a vicious cycle occurs where the filter media solidifies even more firmly.

[0037] Therefore, in this embodiment, as described above, the section 40 to which gas 25 is first supplied at the start of cleaning is set to a different section 40 from the section to which gas 25 was first supplied at the start of the previous cleaning. By changing the section 40 to which gas 25 is first supplied each time, the section 40 in which the filter media layer 12 first collapses can be changed each time. Consequently, the residue of the filter media layer 12 due to gas outflow into other sections 40 can be suppressed, and the peeling of the filter media layer 12 during cleaning in the filtration tank 11 can be promoted. In addition, since the section 40 to which gas 25 is first supplied at the start of cleaning is changed each time, uneven distribution of the filter media layer 12 can be suppressed. Furthermore, since the amount of solidified filter media layer 12 decreases or disappears, a decrease in filtration performance can be suppressed.

[0038] In this embodiment, the control unit 16 automatically controlled the opening and closing of the first valve 31 to the eighth valve 38. However, depending on the size of the filtration tank 11 and other factors such as ease of operation, the opening and closing of the first valve 31 to the eighth valve 38 can also be operated manually.

[0039] Alternatively, the inlet for the washing water 26 supplied to the filtration tank 11 may be installed in each of the multiple divided sections 40, and the washing water 26 may be supplied according to the gas supply sections 40A and 40B to promote the vertical swirling flow CF generated in the filtration tank 11.

[0040] This disclosure is not limited to the embodiments described above, but includes all modifications within the meaning and scope of the claims as indicated by the claims, and further includes all modifications within the meaning and scope of equivalence to the claims. [Explanation of Symbols]

[0041] 10 Filtration device 11 Filtration tank 12 filter media layer 13 Stock solution supply path 14. Gas supply path 15 Wash water supply channel 16 Control Unit 21 Gas introduction section 22 Gas inlet tube 23. Undiluted solution 24 Treatment solution 25 Gases 26 washing water 27 Mixed water 40 zone painting CF vortex

Claims

1. A method for cleaning a downward flow type filtration apparatus equipped with a filtration tank having a filter media layer formed of amorphous filter media, Gas is supplied from below the filter media layer into one of the multiple compartments that divide the inside of the filtration tank. The compartments to which the gas is supplied are changed sequentially, The compartment to which the gas is first supplied at the start of cleaning is different from the compartment to which the gas was first supplied at the start of the previous cleaning. A method for cleaning a downward-flow filtration system.

2. While maintaining the supply of the gas, wash water is supplied into the filtration tank from below the filter media layer. A method for cleaning a downward flow type filtration apparatus according to claim 1.

3. The destination of the washing water is switched from below the filter media layer to above the filter media layer. A method for cleaning a downward flow type filtration apparatus according to claim 2.

4. Filtration tank and A filter media layer formed of irregularly shaped filter media is provided within the aforementioned filtration tank, A gas supply passage is provided in one of the compartments into which the inside of the filtration tank is divided, for supplying gas from below the filter media layer. A control unit that controls the supply of the gas to any of the compartments via a gas supply path, and the sequential change of the compartment to which the gas is supplied, Equipped with, The control unit sets the section to which the gas is first supplied at the start of the previous cleaning as a section to which the gas was first supplied at the start of the previous cleaning. Downward flow type filtration device.

5. The filtration tank is equipped with a washing water supply channel for supplying washing water, The control unit, while maintaining the supply of the gas, supplies the cleaning water from below the filter material layer in the filtration tank via the cleaning water supply passage. The downward flow type filtration device according to claim 4.

6. The control unit switches the destination of the washing water supply via the washing water supply passage from below the filter media layer in the filtration tank to above the filter media layer. The downward flow type filtration device according to claim 5.

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