JP2003340214A - Filter medium cleaning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filtering method which enables a reduction in the pressure resistance design value of a filter container, and a filter medium cleaning method. <P>SOLUTION: In the filter medium cleaning method for allowing liquid to flow through the filter medium housed in the filter container in the direction opposite to a direction at the time of filtering by the pressure of compressed gas after a filter process, a cylindrical filter material having an asymmetric structure is used as the filter medium. Simultaneously with the opening of the discharge port of the filter container or immediately after the opening of the discharge port, the liquid is pressurized by gas. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a filter medium to reuse the filter medium in filtration.

[0002]

2. Description of the Related Art Filtration is applied to chemical and electronic fields such as clarification of plating solutions and washing of electric equipment materials, industrial water, food,
It is an important process widely used in fields such as pharmaceuticals and industrial wastewater, and it is expected that it will be more important than the current situation in the future.

Here, the filtration is generally carried out by a filtration device having a filtration container incorporating a filter medium, and in order to remove even finer insoluble matter, diatomaceous earth or the like is used in combination as a filter aid, and these are applied to the surface of the filter medium. Filtration is also practiced to form a layer of filter aid.

In these filtration treatments, as a result of long-time filtration, insoluble matter (removed substance to be filtered) is accumulated on the surface of the filter medium (filter aid layer when the filter aid is used together), resulting in high pressure loss.
Since the flow rate of the liquid is reduced, water or the like is intermittently flowed in the direction opposite to the direction of the fluid flow at the time of filtration to wash the filter medium (backwash).

In this backwashing process, it is widely practiced to use compressed air to flow the liquid, but in order to prevent the filter medium from being destroyed due to the deformation of the pressure, the backwashing is performed so that the inside and outside of the filter medium are at equal pressure. At the start of the process, in order to apply pressure in the backwash direction to the filter medium with the drainage port of the container closed, as a result, it becomes necessary to increase the pressure resistance design value of the filter container,
There was a problem that the cost of manufacturing the container was high, and at the same time, the pressure container was subject to legal restrictions.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a filtration method capable of reducing the above-mentioned conventional problems, that is, reducing the pressure resistance design value of a filtration container, and a method for cleaning a filter medium. And

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the method for cleaning a filter medium according to the present invention provides a filter medium housed in a filter container by the pressure of compressed gas after the filtration step as described in claim 1. On the other hand, in a method for cleaning a filter medium that causes a liquid to flow in a direction opposite to that during filtration, the filter medium has a cylindrical outer peripheral layer formed by laminating nonwoven fabrics having a low basis weight, an intermediate layer having a nonwoven fabric having a high basis weight, and Having an inner peripheral layer formed by laminating non-woven fabrics of low basis weight in this order, the basis weight of the high-density non-woven fabric of the intermediate layer is higher than the basis weight of the non-woven fabric forming the outer peripheral layer and the non-woven fabric forming the inner peripheral layer, Moreover, the center of the intermediate layer in the thickness direction is 1/1 with respect to the thickness in the laminating direction of the filter medium from the surface on the upstream side in the flow direction of the liquid to be filtered of the outer peripheral surface or the inner peripheral surface.
The non-woven fabric, which is arranged at a position of 0 or more and 1/3 or less, of at least the outer peripheral layer or the inner peripheral layer on the upstream side in the flow direction of the liquid to be filtered has the heat-fusible fiber and the heat-meltable fiber. Using a cylindrical filter medium having an asymmetric structure in which a layer having the heat-fusible fiber is integrated by an adhesive fiber, and at the same time as the opening of the outlet of the filtration container or immediately after the opening of the outlet, This is a method for cleaning a filter medium in which a liquid is pressurized with gas.

Since the cylindrical filter medium having an asymmetric structure as described above has high rigidity and is unlikely to be deformed even if there is a pressure difference between the inside and the outside, when the liquid is made to flow using compressed air in the backwashing process, it is affected by the pressure. It is not necessary to apply pressure to the inside of the container so that the inside and outside of the filter medium become equal in pressure in order to prevent the filter medium from being broken due to deformation, and therefore the pressurization can be performed with the drainage port for drainage being opened. Therefore, it is not necessary to impart high pressure resistance to the filtration container, and the cost is reduced, and at the same time, there is an effect that the pressure container is not restricted by the regulation as a pressure container.

As described above, in the case of a filtration container conventionally made of a material such as a steel plate, it becomes possible to use FRP, or the filtration container formed of FRP can be made of resin without fiber reinforcement. It is also possible to reduce costs.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for cleaning a filter medium of the present invention, it is necessary to pressurize the liquid with a gas at the same time as the opening of the outlet of the filtration container or immediately after the opening of the outlet. When the liquid is pressurized by the gas immediately after the opening of the discharge port, it is necessary to perform it within 2 seconds after opening the discharge port. A desirable range is within 1 second. When more than 2 seconds have passed from the opening of the discharge port, the liquid inside the filter container escapes from the discharge port, and instead air enters the inside of the filter container, and the cleaning (backwashing) effect at the time of discharging the filter medium part touched by the air May decrease.

In consideration of an accident such as a delay in opening the valve of the discharge port, in an automated or semi-automated filter device to which the present invention is applied, pressurization of the liquid by gas is applied from the opening of the discharge port. It is desirable to set it after 0.5 seconds or more,

In the method for cleaning a filter medium of the present invention, as a filter medium, an outer peripheral layer formed by laminating a non-woven fabric having a cylindrical shape, an intermediate layer having a non-woven fabric having a high fabric weight, and a non-woven fabric having a low fabric weight are laminated. Which has an inner peripheral layer in this order, and the basis weight of the high-density nonwoven fabric of the intermediate layer is higher than the basis weight of the nonwoven fabric constituting the outer peripheral layer and the basis weight of the nonwoven fabric constituting the inner peripheral layer, and the thickness of the intermediate layer. The center in the depth direction is located at a position of 1/10 or more and 1/3 or less of the outer peripheral surface or the inner peripheral surface of the upstream surface in the flow direction of the liquid to be filtered, with respect to the thickness in the laminating direction of the filter medium. The non-woven fabric of at least the outer peripheral layer or the inner peripheral layer of the layer on the upstream side in the flow direction of the liquid to be filtered has the heat-fusible fibers and the heat-fusible fibers are used to form the heat-fusible fibers. Use a cylindrical filter medium with an asymmetric structure in which the layers Is required.

In such a cylindrical filter medium having an asymmetric structure, the outer peripheral layer is formed by laminating low-basis-weight nonwoven fabrics, the intermediate layer is formed by high-basis-weight nonwoven fabrics, and the inner peripheral layer is formed by laminating low-basis-weight nonwoven fabrics. It is necessary that the non-woven fabric having a three-layer structure and having a high basis weight in the intermediate layer has a higher basis weight than that of the non-woven fabric constituting the outer peripheral layer and the non-woven fabric constituting the inner peripheral layer.

That is, it is sufficient that there is no intermediate layer, or that the weight of the high-density nonwoven fabric of the intermediate layer is higher than both the basis weight of the nonwoven fabric forming the outer peripheral layer and the basis weight of the nonwoven fabric forming the inner peripheral layer. It may not be possible to obtain good filtration performance, or it may be necessary to enlarge the filter medium. At this time, the low basis weight nonwoven fabric forming the outer peripheral layer and the low basis weight nonwoven fabric forming the inner peripheral layer may have the same basis weight, and in this case, the type of the non-woven fabric that needs to be prepared when the filter medium is produced. Can be reduced. In addition, the basis weight of the high basis weight nonwoven fabric of the intermediate layer is at least twice as high as the higher of the basis weight of the low basis weight nonwoven fabric constituting the outer peripheral layer and the low basis weight nonwoven fabric constituting the inner peripheral layer. It is desirable because a higher effect can be obtained.

[0015] For example, when the bath liquid for the surface treatment process such as a plating solution is used for filtration, the basis weight of the nonwoven fabric constituting the outer and inner layers is preferably 10 g / m ² or more and 30 g / m ² or less. The basis weight of the non-woven fabric having a high basis weight in the intermediate layer is preferably 2 times or more and 6 times or less, and more preferably 20 g / m ² or more and 60 g / m ² or less.

The thickness of the intermediate layer is preferably not less than 1/15 and not more than 1/3 of the thickness in the laminating direction of the cylindrical filter medium having an asymmetric structure. If the thickness of the intermediate layer is too thick, the pressure loss may be too high, and if it is too thin, sufficient filtration performance may not be obtained.

The total thickness of the filtration layer is appropriately adjusted depending on the type of the liquid to be filtered, the amount of liquid to be passed, etc., but it is 3 mm in consideration of the rigidity required for the cylindrical filter medium having an asymmetric structure.
It is preferably not less than 8 mm, more preferably not less than 8 mm.

Considering the pressure loss, the upper limit of the thickness is preferably 20 mm or less, and more preferably 10 mm or less. The length of the cylindrical filter medium having an asymmetric structure is appropriately determined according to the filter container to be stored.

Of the asymmetric cylindrical filter medium used in the present invention,
The intermediate layer having a high basis weight non-woven fabric does not necessarily have to be composed of only a high basis weight non-woven fabric, and may have at least one high basis weight non-woven fabric, for example, a low basis weight non-woven fabric and a high density non-woven fabric are alternately or It may be laminated in any cycle, and this case is also included in the present invention.

In the cylindrical filter medium of the asymmetric structure used in the present invention, if there is no outer peripheral layer formed by laminating a low-basis weight nonwoven fabric or an inner peripheral layer formed by laminating a low-basis weight nonwoven fabric, filtration is performed in the process of filtration. There may be a case where the pressure loss becomes extremely high in the stage where the flow rate is low and frequent backwashing may be required, or the backwashing time becomes long or a sufficient backwashing effect cannot be obtained.

In the intermediate layer of the cylindrical filter medium having an asymmetric structure used in the present invention, the center of the intermediate layer in the thickness direction is at a position of 1/10 or more and 1/3 or less from the outer peripheral surface with respect to the thickness of the filter medium in the laminating direction. It is necessary to be arranged so that. In this way, since the intermediate layer is arranged on the upstream side of the flow of the liquid to be filtered, the amount of liquid such as water required for backwashing is small, and the time required for backwashing is shortened. It becomes possible.

The above effect can be obtained when the center of the intermediate layer in the thickness direction is arranged at a position more than 1/3 of the thickness of the filter medium in the laminating direction from the outer peripheral surface. May not be. A preferable range is that the center of the thickness direction of the intermediate layer is 1/8 or more from the outer peripheral surface with respect to the thickness of the filter medium in the laminating direction.
The position is / 3 or less.

In the method for cleaning a filter medium of the present invention, the non-woven fabric used is selected from materials having performance suitable for the intended use.
At this time, in consideration of cost, chemical resistance, etc., it is preferable that the fiber is made of polypropylene, polyethylene, or a polyolefin fiber obtained by mixing various copolymers with propylene or ethylene.

In the cylindrical filter medium having an asymmetric structure used in the present invention, at least the nonwoven fabric of the outer peripheral layer has the heat-fusible fiber and the layer having the heat-fusible fiber is integrated by the heat-fusible fiber. Need to be present.

The heat-fusible fiber is a fiber made of two kinds of thermoplastic resins having different cores and surface layers, and the melting point of the resin forming the surface layer is higher than the melting point of the resin forming the core. It is a low fiber, and at the temperature at which the core portion does not melt, and when heated to a temperature at which the surface layer portion melts, the heat-fusible fibers are fused, but at this time, the shape of the fiber and the space formed by the fibers Since the pressure loss is not increased and the filtration performance is not deteriorated, the layers formed by laminating the non-woven fabrics can be integrated, and a filter material that does not easily peel between the layers can be obtained. At the same time, the rigidity can be increased.

When the non-woven fabrics are adhered to each other with an adhesive or the like, there is a concern that the adhesive component of the filtrate may be contaminated, and the inter-woven fabric fibers may be clogged by the adhesive, so that the filtration accuracy is improved. In some cases, the filter performance may deteriorate or the filtration performance itself may deteriorate. As such a heat-fusible fiber,
Fusible fibers are generally available that consist of polypropylene in the center and polyethylene in the outer layer.

In the asymmetric cylindrical filter medium used in the present invention, if the fibers constituting the non-woven fabric are too thick, sufficient filtration performance may not be obtained, and if they are too thin, the pressure loss increases and the required filtration flow rate increases. You may not get it. The desirable range of the fibers used is 0.5d or more and 10d or less. Further, the length of the fiber used is preferably 3 mm or more and 40 mm or less, and if it is less than 3 mm, the strength required as a cylindrical filter medium becomes low, and if it exceeds 40 mm, workability may deteriorate.

The asymmetric cylindrical filter medium used in the present invention will be described with reference to the drawings with reference to the model partial sectional view of FIG.

This filter material is cylindrical and has an outer peripheral layer formed by laminating low-basis-weight nonwoven fabrics, an intermediate layer including high-basis-weight nonwoven fabrics, and an inner peripheral layer formed by laminating low-basis-weight nonwoven fabrics. In order, the basis weight of the high-density nonwoven fabric of the intermediate layer is higher than the basis weight of the nonwoven fabric forming the outer peripheral layer and the basis weight of the nonwoven fabric forming the inner peripheral layer, and the center in the thickness direction of the intermediate layer is The nonwoven fabric of at least the outer peripheral layer, which is arranged at a position 1 from the outer peripheral surface with respect to the thickness D in the laminating direction, has heat-fusible fibers, and the heat-fusible fibers are used to form the heat-fusible fibers. A cylindrical filter medium having an asymmetrical structure in which the layers included therein are integrated, and l is D / 10 or more and D / 3 or less. The thickness d of the intermediate layer is D / 15 or more and D / 3 or less in the range where the outer peripheral layer exists. The outer peripheral layer (its thickness is l-d
It is represented by / 2. It is desirable to secure 1/10 or more, and more desirably 1/8 or more of the thickness D of the entire filter medium in the laminating direction.

The flow of the liquid to be filtered during filtration is from the outer peripheral layer to the inner peripheral layer, and the flow of the fluid during backwash is opposite. It should be noted that the backwashing effect is very high in the asymmetric cylindrical filter medium as described above. It is considered that this is because the intermediate layer functions as a kind of nozzle.

The nozzle effect of this intermediate layer will be described with reference to the model diagram of FIG. Since the "eye" of the high-density nonwoven fabric of the intermediate layer is smaller than the "eye" of the low-density nonwoven fabric in the outer peripheral layer or the inner peripheral layer, a kind of bottleneck is formed to the fluid as shown in FIG. In the filtration step, unnecessary substances are accumulated in the layer above the intermediate layer (dark colored hatching portion) in the figure. When the fluid reaches this bottleneck during backwashing, the fluid concentrates on this bottleneck as shown by the arrow in the figure, so the flow velocity increases at that portion, and the fluid flows to the upper side of the intermediate layer in the figure. It is considered that the cleaning efficiency is increased because the accumulated insoluble matter is vigorously washed away.

The model cross section of the asymmetric cylindrical filter medium is shown in FIGS. 3 (a) and 3 (b).

FIG. 3A shows an example in which the intermediate layer is arranged near the outer circumference, and FIG. 3B shows an example in which the intermediate layer is arranged near the inner circumference. In the present invention, a cylindrical filter medium having an asymmetric structure in which the intermediate layer of FIG. 3 (a) is arranged near the outer circumference is used.

Since at least the non-woven fabric of the outer peripheral layer has the heat-fusible fiber and the layer having the heat-fusible fiber is integrated by the heat-fusible fiber, it is intermediate even when backwashing. Since the layers are prevented from being deformed, the cleaning can be efficiently performed without once making the pressure inside and outside the filter medium the same.

Such a cylindrical filter medium can be produced, for example, as follows. A fiber made of two kinds of thermoplastic resins having different cores and surface layers, wherein the melting point of the resin forming the surface layer is lower than that of the resin forming the core A non-woven fabric (non-woven fabric with a low basis weight) is wound around the core material as shown in FIG.
At this time, due to hot air, infrared rays or far infrared rays,
Alternatively, the non-woven fabric is brought into contact with a heated heat roller or the like so that the non-woven fabric is densely laminated while being rotated around the core material while being heated.

At this time, it is necessary to adjust the temperature so that the temperature becomes too high and the entire heat-fusible fiber does not melt, and the non-woven fabrics sufficiently stick to each other. For example, when a non-woven fabric made of a heat-fusible fiber having a polypropylene core and a polyethylene surface layer is heated with hot air, hot air having a temperature of 120 ° C. or higher and 150 ° C. or lower is usually used. adjust.

After laminating a predetermined amount (up to a predetermined thickness), then similarly laminating a predetermined amount tightly on the inner layer prepared above using a nonwoven fabric made of heat-sealable fiber having a high basis weight. An intermediate layer is formed (see FIG. 4 (b)).

Then, similarly, except that a predetermined amount of a nonwoven fabric made of heat-fusible fiber having a low basis weight is tightly wound on the intermediate layer to form an outer peripheral layer (FIGS. 4 (c) and 4 (d)). Finally, pull out the core material.

As described above, the core portion and the surface layer portion are made of two kinds of thermoplastic resins, and the melting point of the resin constituting the surface layer portion is lower than the melting point of the resin constituting the core portion. By winding and laminating a nonwoven fabric around a core material while heating, the excellent cylindrical filter medium according to the present invention can be easily and efficiently produced, in which case there is no peeling between the nonwoven fabric, and a holder. It is possible to obtain a cylindrical filter medium having sufficient strength and rigidity without bulging or crushing at the time of filtration or backwashing, even without a reinforcing material.

The method for cleaning a filter medium according to the present invention can be applied to a filter device as shown in FIG. 5, for example. In the figure, the filtration container A is made of polypropylene (it can be made of polypropylene because high pressure resistance is not required as described later. However, it may be made of polypropylene reinforced with glass fiber). Its shape is cylindrical. The filtration container A includes an upper pipe connecting portion Aa, a middle tubular portion Ab, and a lower pipe connecting portion Ac, which are connected by flanges. The upper and lower bottomed tubular pipe connection parts Aa and Ac are members of the same shape (common members) and are molded by the same mold, which is advantageous in terms of productivity and mold manufacturing cost.

FIG. 6 shows an example of the bottomed cylindrical pipe connection portion Ac as an exploded model diagram in which the funnel-shaped slurry collector 3a having holes on the lower side is removed.

The bottomed tubular pipe connecting portion Ac has a pipe connecting port to which a pipe can be connected, that is, a drain discharge outlet A2 and a filtered liquid introducing port A3, and the drain discharge outlet A2 is a pipe connecting portion. It is provided inside and is connected to a bottomed cylindrical partitioning part 3 that has both the bottom part and the bottom part of the pipe connecting part, and the treated liquid introducing port A3 is connected inside the pipe connecting part and outside the partitioning part. There is. A funnel-shaped slurry sludge collector 3a is fixed to the top of the bottomed cylindrical partition 3 by gluing (it may be fixed by bolts instead of gluing).

The funnel-shaped slurry collector 3a is arranged so as to be located below the cylindrical filter medium 1 having an asymmetric structure (hereinafter also referred to as "cylindrical filter medium 1"). It has a funnel shape, and the area of the hole 3a1 at the bottom of this funnel-shaped slurry collector 3 is considerably smaller than the cross-sectional area of the cylinder of the bottomed partition part 3 of the lower pipe connection part.
It is 3.

The bottom hole 3a1 is small as described above, and when viewed from the side of the bottomed cylindrical partition 3 side, the lower surface of the funnel-shaped slurry mud collector 3a is a "bareback". Since it has a basket-like structure, even if insoluble matter remains in the bottomed cylindrical partition portion 3, it is difficult to return to the filter medium side space of the filtration container A.

Inside the filter container A, a plurality of cylindrical filter media 1 having an asymmetric structure are arranged so that their length directions are vertical, and the lower end thereof is sealed with polypropylene.

The cylindrical filter medium 1 having an asymmetric structure is shown in FIG. 3 (a) with its cross section modeled, and is manufactured by the method shown in FIG. The low-density non-woven fabric used has a basis weight of 20 g / m ² , a core of polypropylene and a surface layer of polyethylene heat-sealing fibers (2 denier). The high-density non-woven fabric has a basis weight of 40 g / m 2. ² , a non-woven fabric made of polypropylene fiber (2 denier), 160
It is rolled up and laminated using hot air of ℃ together.

The inner diameter of the asymmetric cylindrical filter medium 1 is 10 m.
m, the outer diameter is 20 mm, the thickness of the intermediate layer is 0.5 mm, and the center of the intermediate layer is 1.5 mm from the outer circumference. The number of turns of the high-density nonwoven fabric in the intermediate layer is two (actually, more than two because there are some overlapping portions). The length of the asymmetric cylindrical filter medium is 60 cm.

The upper end of the cylindrical filter medium 1 having such an asymmetric structure is fixed to the intermediate plate 2 with an adhesive and suspended (may be fixed with bolts). The intermediate plate 2 is provided with through holes 2a corresponding to the hollow portions 1a of the cylindrical filter medium 1 having an asymmetric structure.

The upper side of the intermediate plate 2 has a bottomed cylindrical pipe connecting portion A.
It is provided inside a and is connected to the bottom of the pipe connecting portion Aa and a bottomed cylindrical partitioning portion 2b that shares the bottom. The bottomed cylindrical partition portion 2b is a cylindrical filter medium 1 having an asymmetric structure of the wall of the filtration container.
Filtrate outlet and gas inlet A provided at a higher position than
1 (the filter liquid outlet / gas inlet A1 is provided on the downstream side of the cylindrical filter medium 1 in the flow direction of the liquid to be filtered, which will be clarified in the description below). In this example, the filtrate outlet and the gas inlet are provided, but the filtrate outlet and the gas inlet may be provided separately. The pipe connecting portion Aa is the same as the pipe connecting portion Ac in FIG. 6, but is used upside down.

Outside the bottomed cylindrical partitioning portion 3 and at the bottom of the pipe connection portion Ac (position upstream of the cylindrical filter medium 1 in the flow direction of the liquid to be filtered), there is an inlet A3 to be filtered. It is provided.

The position of the liquid to be filtered-introduced A3 is that the liquid supplied into the filtration container A from there does not hit the upper surface of the funnel-shaped slurry collector 3a described later, so that the funnel-shaped slurry collector is It is preferable in that it exerts the effect of the mud 3a,
It is usually placed on the bottom or on the side near the bottom. In this example, it is provided on the side surface near the bottom.

In the above, the funnel-shaped slurry collector 3
The area of the gap between the edge (maximum diameter portion) of a and the inner wall of the container A may be 1 times or more as compared with the cross-sectional area of the pipe connected to the filtered liquid introducing port A3 introduced into this container, It is preferably 1.5 times or more. If this ratio is less than 1 times, the flow velocity of the liquid flowing through the gap becomes faster, and as a result, the residual insoluble matter in the bottomed cylindrical partition 3 of the lower pipe connecting portion rises up and the asymmetric structure is formed. Redeposition on the surface of the cylindrical filter medium may increase the load at the time of filtration, or the flow may cause an unexpected obstacle in the cylindrical filter medium 1 having a plurality of asymmetric structures.

On the other hand, the ratio is too large (more than 5 times)
And, the slurry of the filter aid and the insoluble matter filtered by the filter aid from the plurality of asymmetrical cylindrical filter media 1 in the discharging step infiltrate into the filtered liquid introduction port A3 side through this gap. When unnecessary liquids will be described later,
It is supplied to a plurality of cylindrical filter media 1 having an asymmetric structure in which a filter layer formed of a filter aid is not formed, and leaks to the downstream thereof, or the load of the cylindrical filter media 1 having an asymmetric structure is increased.

In this example, the inner diameter of the container A is 30 cm, the maximum diameter of the funnel-shaped slurry collector 3a is 28.8 cm, and the thickness of the pipe connected to the filtered liquid inlet A3 is 5 cm. is there. The drain discharge outlet A2 is provided at the bottom of the filtration container and on the upstream side of the cylindrical filter medium, and is connected to a drain tank (not shown) via a drain valve V7.

Further, a position higher than the top of the filtering surface of the cylindrical filter medium 1 (and the outside of the bottomed cylindrical partition 2b of the wall of the filter container A) (and the cylindrical filter medium 1 to be filtered). An air vent port A4 is provided at a position upstream of the liquid flow direction).

A predetermined amount of filter aid such as diatomaceous earth dispersed in a small amount of water to form a slurry in the filter aid tank 4 (the amount required for one step of forming the filter aid layer: That is, the end of the filter aid layer forming step can be known when the filter aid tank 4 runs out of filter aid). As will be described later, the filter aid is supplied to the surface of the cylindrical filter medium 1 having an asymmetric structure, where it stays and accumulates to form a so-called "attached state" to improve its filtering ability, and the cylindrical filter medium 1 having an asymmetric structure. It has a function to remove insoluble matter smaller than the original ability of.

The filtered liquid introduction port A3 of the filtration container is connected to the outlet side of a pump for delivering the liquid into the filtration container. A filter aid tank 4 is provided outside the filter container A, and the pump 5p is provided at the bottom of the filter aid tank 4 from the filter aid tank.
A filter aid line L5 for introducing a liquid is provided on the inlet side of the filter aid line L5, and the filter aid line L5 has a filter aid valve V5 for opening and closing the filter aid line L5.

Further, the treated liquid tank 6 containing the treated liquid is connected to the pump inlet side by the treated liquid supply line L1, which is opened and closed in the treated liquid supply line L1. An inlet valve V1 is provided for this purpose.

The air vent port A4 of the filtration container A is a cylindrical filter medium 1
It is provided at a position higher than the top of the filter surface and is connected to the filter aid tank 4 by the air vent line L4. The air vent line L4 has a pressure gauge 5b and an air vent valve V4 for opening and closing the air vent line L4.

The filtrate outlet of the filtration container A (in this example, the filtrate outlet / gas inlet A1) is connected to the filter aid tank 4 by a return line L8, and a return valve V8 connected to the return line L8. By opening and closing, the filtrate filtered by the cylindrical filter medium 1 having an asymmetric structure is supplied to the filter aid tank 4 from above as necessary. At this time, the filter aid (diatomaceous earth or the like, which is in the form of a slurry mixed with water) in the filter aid tank 4 is agitated by the force of the liquid flow, and is uniformly dispersed in the liquid. .

The filtrate outlet of the filtration container A (in this example, the filtrate outlet / gas inlet A1) is a filtrate outlet line L2 provided with a filter outlet valve V2 that can be opened and closed, and a precoat valve that can be opened and closed. It is connected to a precoat line L3 equipped with V3. The precoat line L3 is further connected to the inlet side of the pump 5p.

Further, the gas inlet of the filtration container A (filtrate outlet / gas inlet A1 in this example) is adjusted to an appropriate pressure by an air supply line L6 (regulator (not shown)) having an air supply valve V6 that can be opened and closed. Conditioned compressed air is supplied).

As described above, the filtration device shown in FIG.
A filtration device having an upper collection type filtration container (A) containing a filter medium therein, wherein a cylindrical filter medium (1) made of densely wound non-woven fabric is used as the filter medium, and the filter container (A) is covered with the cylindrical filter medium (1). The treated liquid introducing port A3 is located on the upstream side in the flow direction of the filtered liquid, the drain discharge outlet A2 is located on the bottom of the filtering container and upstream of the cylindrical filter medium, and the same as the cylindrical filter medium 1 Or higher and the above cylindrical filter medium 1
With respect to the upstream side of the flow direction of the liquid to be filtered, the air vent A4, and a position higher than the cylindrical filter medium 1 and downstream of the cylindrical filter medium 1 in the flow direction of the liquid to be filtered. Is equipped with a filtrate outlet and gas inlet A1, and the filtered liquid inlet A3 of the filtration container is connected to the outlet side of a pump 5p for delivering the liquid into the filtration container A, and the filtration aid is provided outside the filtration container 1. A return line L8 which has a tank 4 and which introduces a filtered liquid from the filtered liquid outlet / gas inlet A1 of the filtration container A into the filter aid tank 4, and a return valve V8 for opening and closing the return line L8; From a filter aid line L5 for introducing a liquid from the filter aid tank 4 to the inlet side of the pump 5p, a filter aid valve V5 for opening and closing the filter aid line L5, and a filtrate outlet V2 of the filter container A. Entrance side of the above pump 5p Pre-coat line V3 to introduce a liquid
And a precoat valve V3 for opening and closing the precoat line.

The operation of this filtering device will be described first with reference to the liquid spattering process. The pump 5p stops and the valves V1 to V1
After the inlet valve V1, the air bleeding valve V4 and the return valve V8 are opened from the state where all V8 are closed,
Pump 5p is operated

The treated liquid to be filtered in the treated liquid tank 6 to be filtered passes through the treated liquid supply line L1 to be filtered by the pump 5p,
It is introduced into the filtration container A from the liquid to be filtered introduction port A3,
After reaching the top of the container (completion of the liquid beam), the liquid is the air vent A
4 through the air bleeding line L4 and begins to be discharged to the filter aid tank 4. The filtrate that has passed through the asymmetric cylindrical filter medium 1 is discharged to the filter aid tank 4 through the return line L8 through the filtered liquid outlet / gas inlet A1.

After the completion of the liquid bubbling step, the filter aid layer forming step is started. That is, the precoat valve V3 and the filter aid valve V5 are immediately opened, and the inlet valve V1 and the air bleeding valve V4 are closed. At this time, the liquid in which the filter aid is dispersed passes from the bottom of the filter aid tank 4 through the filter aid line L5 and the pump 5p, and the filtered liquid introduction port A
3 is introduced into the filtration container A and is filtered by the cylindrical filter medium 1 having an asymmetric structure, and diatomaceous earth remains on the surface thereof, and the filtered filtrate is filtered again from the filtrate outlet port / gas inlet port A1 through the return line L8. A circulation is formed back to the auxiliary agent tank 4. At this time, since the dispersion concentration of the filter aid supplied from the filter aid tank 4 is high, it is more suitable for the filtrate from the filtered liquid outlet / gas inlet A1 supplied to the pump 5p entry side via the precoat line L3. The dispersion concentration is adjusted.

By such circulation, the filter aid tank 4 is
The filter aid inside is sequentially supplied into the filter container A, is accumulated on the outer peripheral surface of the cylindrical filter medium 1 having an asymmetric structure, and the filter aid is gradually deposited on the surface, and is filtered by the cylindrical filter medium 1 having the asymmetric structure alone. A filtration layer is formed which can remove even a minute amount of insoluble matter.

After the filter aid layer of the filter aid is thus formed on the outer periphery of the cylindrical filter medium 1 having an asymmetric structure, the filtration step is started.

The filter aid valve V5 and the return valve V8 are closed, the inlet valve V1 and the filtrate outlet valve V2.
Is opened and the precoat valve V3 is closed, a clarified filtrate can be obtained from the filtrate outlet line L2. At this time, the pressure loss due to the asymmetrical cylindrical filter medium 1 (and the filter layer of the filter aid disposed around the filter medium 1) can be read from the pressure gauge 5b. After a predetermined amount of filtration is completed, or after the pressure loss reaches a predetermined value, the pump 5p is stopped and discharge is performed.

In the discharging process, the inlet valve V1 and the filtrate outlet valve V2 are closed, the air supply valve V6 and the drain valve V7 are simultaneously opened, and the air supply line L
The compressed air, which is supplied from 6 and is adjusted to an appropriate pressure, is introduced into the filtration container A from the filtrate / gas inlet port A1, and the cylindrical bottomed partition portion 2b through the through hole 2a of the intermediate plate 2 is asymmetrical. After passing through the cylindrical filter medium 1 having the structure, the liquid in the container A is pushed down to the drain valve V7 and discharged. Since the drain discharge outlet A2, which is a discharge port, is opened at the same time when the compressed air is supplied into the container in this manner, it is not necessary to use the filtration container A as a pressure resistant container, and it is inexpensive and easy to work as in this example. It can be made of easy polypropylene.

The clear filtrate existing in a part of the line and in the bottomed cylindrical partition 2b flows backward, and the flow also rinses away the filter aid layer adhered to the surface of the cylindrical filter medium 1 having an asymmetric structure. (Backwashing), as a drain with extremely large amounts of contaminants, it is guided to the partition section 3 while being collected by the funnel-shaped slurry collector 3a, and flows from the drain discharge outlet A2 through the drain line L7 to an external drain tank (not shown). Is discharged to.

As described above, the liquid beam step, the filter aid layer forming step, the filtering step and the discharging step are repeated.

In the above, since the cylindrical filter medium 1 having an asymmetric structure is used, even if the pressure difference between the internal space and the outside of the filter medium is large at the start of discharging, the filter medium is swelled due to its high rigidity.
It will not be destroyed and will not be adversely affected. Therefore, when the liquid is discharged from the filtration container A, it is possible to pressurize the liquid with the gas at the same time as the opening of the discharge port of the filtration container or immediately after the opening of the discharge port. At this time, since it is not necessary to use a pressure container which assumes that pressure is applied to the filtration container A itself, the manufacturing cost of the container is low, and it is used for depressurizing the air supply line 5d (generally high pressure). Even if the regulator fails, it is possible to prevent the filter container from bursting or being damaged.

Further, the pressure inside the container just before the end of the filtration step is examined by the pressure gauge 5b, and the above-mentioned discharging step is performed by using the pushing gas having a pressure lower than the pressure, so that the gas having an unnecessarily high pressure is used. Since it does not occur, it is possible to reduce energy consumption, and it is possible to minimize the impact on the filter container and the filter material in the discharging step.

After the filtration step, the pressure of the compressed gas causes the liquid to flow in the direction opposite to that during the filtration through the filter medium contained in the filter container, simultaneously with the opening of the outlet of the filter container or at the outlet of the outlet. Immediately after the opening, the liquid is pressurized by the gas, so that air does not enter from the discharge port, so that the cleaning (backwashing) effect at the time of discharge is high and a stable effect is obtained.

[0076]

The method for cleaning a filter medium according to the present invention is a method for cleaning a filter medium in which a liquid is caused to flow in a direction opposite to that at the time of filtration with respect to the filter medium stored in a filter container by the pressure of gas after the filtration step. As the cylindrical, an outer peripheral layer formed by laminating non-woven fabric having a low basis weight, an intermediate layer having a non-woven fabric having a high basis weight,
And having an inner circumferential layer formed by laminating non-woven fabrics having a low basis weight in this order, and the basis weight of the non-woven fabric having a high basis weight of the intermediate layer is higher than that of the non-woven fabric constituting the outer peripheral layer and the non-woven fabric constituting the inner peripheral layer. The center of the intermediate layer in the thickness direction is high and is 1/10 or more from the upstream surface in the flow direction of the liquid to be filtered of the outer peripheral surface or the inner peripheral surface with respect to the thickness in the laminating direction of the filter medium. / 3 or less, and at least the nonwoven fabric of the outer peripheral layer or the inner peripheral layer on the upstream side in the flow direction of the liquid to be filtered has heat-fusible fibers and Using a cylindrical filter medium having an asymmetric structure in which the layer having the heat-fusible fiber is integrated, and at the time of pressurizing the liquid with gas, the outlet of the filtration container is opened at the same time as pressurization. Since the pressure resistance design value of the container can be lowered, a low cost container can be used. It can to have high safety, an excellent filter medium cleaning method may further omit and inspection required in the case of the pressure vessel.

[Brief description of drawings]

FIG. 1 is a model partial cross-sectional view of an asymmetric cylindrical filter medium used in the present invention.

FIG. 2 is a model diagram illustrating a nozzle effect of an intermediate layer of a cylindrical filter medium having an asymmetric structure.

FIG. 3 is a model cross-sectional view showing two types of asymmetrical cylindrical filter media. (A) It is a figure which shows the example in which the intermediate | middle layer is distribute | arranged near the outer periphery. (B) It is a figure which shows the example in which the intermediate | middle layer is distribute | arranged near the inner periphery.

FIG. 4 is a model diagram showing a manufacturing method of an example of a cylindrical filter medium having an asymmetric structure.

FIG. 5 is a diagram showing a filtering device to which the method for cleaning a filtering material according to the present invention can be applied.

FIG. 6 is a funnel-shaped slurry collector 3a having holes on the lower side.
FIG. 4 is an exploded model diagram showing an example of a bottomed tubular pipe connection part with the bottom removed.

[Explanation of symbols]

A filtration container Bottomed cylindrical pipe connection on Aa Ab middle tube Bottom bottomed tubular pipe connection under Ac A1 filtrate outlet and gas inlet A2 drain discharge outlet A3 Filtered liquid inlet A4 air vent 1 Cylindrical filter media with asymmetric structure 1a Hollow part of cylindrical filter medium 1 2 Intermediate plate 2a through hole 2b partition 3 partitions 3a slurry mud collector 4 Filter aid tank 5b pressure gauge 5p pump 6 Filtered liquid tank L1 Filtered liquid supply line L2 filtrate outlet line L3 precoat line L4 air bleeding line L5 filter aid line L6 air supply line L7 drain line L8 return line V1 inlet valve V2 filtrate outlet valve V3 pre-coated valve V4 air bleeding valve V5 filter aid valve V6 air supply valve V7 drain valve V8 return valve

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) B01D 29/38 520A 29/10 501Z 510E 510G 520B 530A

Claims (2)

[Claims] 1. A method for cleaning a filter medium, in which a liquid is caused to flow in a direction opposite to that at the time of filtration to a filter medium housed in a filter container by a gas pressure after a filtration step, wherein the filter medium has a cylindrical shape and is low. A peripheral layer formed by laminating non-woven fabrics having a unit weight, an intermediate layer having a non-woven fabric having a high unit weight, and
Having an inner peripheral layer formed by laminating low-density fabrics in this order,
The basis weight of the high-density nonwoven fabric of the intermediate layer is higher than the basis weight of the nonwoven fabric forming the outer peripheral layer and the weight of the nonwoven fabric forming the inner peripheral layer, and the center in the thickness direction of the intermediate layer is the thickness in the laminating direction of the filter medium. On the other hand, the outer peripheral surface or the inner peripheral surface is arranged at a position of 1/10 or more and 1/3 or less from the surface on the upstream side in the flow direction of the liquid to be filtered, and at least the outer peripheral layer or the inner peripheral layer The nonwoven fabric of the layer on the upstream side in the flow direction of the liquid to be filtered is
Using a cylindrical filter medium having an asymmetric structure in which a layer having the heat-fusible fiber is integrated with the heat-fusible fiber, and at the same time when the outlet of the filtration container is opened. Alternatively, a method for cleaning a filter medium is characterized in that the liquid is pressurized by the gas immediately after opening the discharge port. 2. The method for cleaning a filter medium according to claim 1, wherein the pressure of the gas is lower than the pressure applied to the filter medium during the filtration process.