JP4309616B2 - Cleaning method for filter media - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for washing a filter medium for reusing the filter medium in filtration.
[0002]
[Prior art]
Filtration is an important process widely used in chemical and electronic fields such as clarification of plating solutions and cleaning of electrical equipment materials, industrial water, food, pharmaceuticals, industrial wastewater, etc. Important importance is expected.
[0003]
Here, the filtration is generally performed by a filtration apparatus having a filtration container in which a filter medium is incorporated. In order to remove even finer insoluble matter, diatomaceous earth or the like is also used as a filter aid, and these filter aids are applied to the surface of the filter medium. Filtration to form a layer consisting of is also performed.
[0004]
In these filtration treatments, as a result of filtration for a long time, insoluble matter (subject to be filtered) accumulates on the surface of the filter medium (filter aid layer when the filter aid is used together), pressure loss increases, and the liquid flow rate decreases. Therefore, intermittently, water or the like is flowed in the direction opposite to the flow direction of the fluid during filtration to wash the filter medium (backwash).
[0005]
In this backwashing process, it is widely performed to flow the liquid by the pressure using compressed air, but at the start of the backwashing process so that the inside and outside of the filter medium become equal pressure in order to prevent destruction due to deformation of the filter medium due to pressure. In order to apply pressure in the backwash direction to the filter medium in a state in which the drainage port of the container is closed, it is necessary to increase the pressure resistance design value of the filtration container as a result, resulting in high manufacturing cost of the container, There were problems such as being subject to legal restrictions.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a cleaning method for a filter medium that improves the above-described conventional problems, that is, a filtration method that can lower the pressure resistance design value of a filtration container.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problem, the method for cleaning a filter medium according to the present invention, as described in claim 1, causes the filter medium stored in the filter container in a direction opposite to that during filtration due to the pressure of the compressed gas after the filtration step. In the washing method of the filter medium for flowing the liquid, the filter medium is a cylindrical outer layer formed by laminating a low-weight nonwoven fabric, an intermediate layer having a high-weight nonwoven fabric, and a low-weight nonwoven fabric. The inner layer has an inner circumferential layer in this order, and the basis weight of the nonwoven fabric having a high basis weight 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 in the thickness direction of the intermediate layer The center is arranged so as to be at a position of 1/10 or more and 1/3 or less 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 stacking direction of the filter media. The flow of the liquid to be filtered out of at least the outer peripheral layer or the inner peripheral layer The upstream layer non-woven fabric has a heat-fusible fiber, and the layer having the heat-fusible fiber is integrated with the heat-fusible fiber. This is a method for cleaning a filter medium in which the liquid is pressurized with the gas simultaneously with the opening of the container outlet or within 2 seconds of opening the outlet.
[0008]
Since the cylindrical filter medium with the above asymmetric structure has high rigidity and is difficult to be deformed even if there is a pressure difference between the inside and the outside, the deformation of the filter medium due to the pressure is caused when flowing liquid using compressed air in the backwash process. It is not necessary to apply pressure in the container so that the inside and outside of the filter medium are at the same pressure to prevent breakage due to pressure, and therefore pressure can be applied with the drainage port open for drainage. It is unnecessary to give the container high pressure resistance, and the cost is reduced. At the same time, there is an effect that there is no restriction on the law as a pressure container.
[0009]
Thus, conventionally, in the case of a filtration container formed of a material such as a steel plate, FRP can be used, or the filtration container formed of FRP can be made of resin without fiber reinforcement. Cost reduction is also possible.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the method for cleaning a filter medium of the present invention, it is necessary to pressurize the liquid with a gas simultaneously with opening of the outlet of the filtration container or immediately after opening of the outlet. When pressurizing the liquid with gas immediately after opening the discharge port, it is necessary to do so within 2 seconds after opening the discharge port. A desirable range is within 1 second. When more than 2 seconds have passed since the discharge port was opened, the liquid inside the filtration container escapes from the discharge port. Instead, air enters the filtration container, and the cleaning (backwashing) effect at the time of discharging the filter medium part touched by the air May decrease.
[0011]
In consideration of an accident such as a delay in opening the valve of the discharge port, in an automated or semi-automated filtration device to which the present invention is applied, pressurization of the liquid with gas is performed by 0.5% from the opening of the discharge port. It should be set to be more than a second later,
[0012]
In the filter medium cleaning method of the present invention, the filter medium is a cylindrical outer layer formed by laminating a low-weight nonwoven fabric, an intermediate layer having a high-weight nonwoven fabric, and a low-weight nonwoven fabric. The inner layer has an inner circumferential layer in this order, and the basis weight of the nonwoven fabric having a high basis weight 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 in the thickness direction of the intermediate layer The center is arranged so as to be at a position of 1/10 or more and 1/3 or less 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 stacking direction of the filter media. The non-woven fabric 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 a heat-fusible fiber and a layer having the heat-fusible fiber by the heat-fusible fiber. It is necessary to use a cylindrical filter medium with an integrated asymmetric structure. .
[0013]
In such an asymmetrical cylindrical filter medium, three layers comprising an outer circumferential layer formed by laminating a low-weight nonwoven fabric, an intermediate layer having a high-weight nonwoven fabric, and an inner circumferential layer formed by laminating a low-weight nonwoven fabric It is necessary for the structure and the basis weight of the nonwoven fabric having a high basis weight of the intermediate layer to be 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.
[0014]
That is, sufficient filtration performance without an intermediate layer or when the basis weight of the nonwoven fabric with a high basis weight of the intermediate layer is not higher than both 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 May not be obtained, or the filter medium needs to be enlarged. At this time, the low-weight nonwoven fabric constituting the outer circumferential layer and the low-weight nonwoven fabric constituting the inner circumferential layer may have the same basis weight, and in this case, the type of nonwoven fabric that needs to be prepared when producing the filter medium Can be reduced. In addition, the basis weight of the nonwoven fabric with a high basis weight of the intermediate layer may be at least twice the higher one of the basis weight of the nonwoven fabric with a low basis weight constituting the outer peripheral layer and the basis weight of the nonwoven fabric with a low basis weight constituting the inner peripheral layer. It is desirable because a higher effect can be obtained.
[0015]
For example, when filtering the surface treatment process bath solution such as plating solution, the basis weight of the nonwoven fabric constituting the outer peripheral layer and the inner peripheral layer is desirably 10 g / m ² or more and 30 g / m ² or less. The basis weight of the medium-weight nonwoven fabric is preferably 2 to 6 times, more preferably 20 g / m ^{2 to} 60 g / m ² .
[0016]
The thickness of the intermediate layer is preferably 1/15 or more and 1/3 or less of the thickness in the stacking direction of the cylindrical filter medium having an asymmetric structure. When the thickness of the intermediate layer is too thick, the pressure loss may be too high, and when it is too thin, sufficient filtration performance may not be obtained.
[0017]
The thickness of the entire filtration layer is appropriately adjusted depending on the type of liquid to be filtered, the amount of liquid to be filtered, etc., but considering the rigidity required for a cylindrical filter medium with an asymmetric structure, it is preferably 3 mm or more, and preferably 8 mm or more. And more preferred.
[0018]
In consideration of 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 filtration container to be stored.
[0019]
The intermediate layer having a high-weight non-woven fabric of the cylindrical filter medium having an asymmetric structure used in the present invention does not necessarily need to be composed only of a high-weight non-woven fabric, and may have at least one high-weight non-woven fabric, for example, a low-weight non-woven fabric. And a high-density nonwoven fabric may be laminated alternately or in any cycle, and this case is also included in the present invention.
[0020]
In the asymmetrical cylindrical filter medium used in the present invention, if there is no outer peripheral layer formed by laminating a low-weight nonwoven fabric or an inner circumferential layer formed by laminating a low-weight nonwoven fabric, the filtration flow rate is low during the filtration process. In some stages, the pressure loss becomes extremely high, and frequent backwashing may be required, or the backwashing time becomes long or sufficient backwashing effect cannot be obtained.
[0021]
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 in the stacking direction of the filter medium. It is necessary to be arranged. Thus, 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.
[0022]
The above effect may not be obtained when the center of the intermediate layer in the thickness direction is arranged to be more than 1/3 of the thickness of the filter medium in the stacking direction from the outer peripheral surface. is there.
As a preferable range, the center in the thickness direction of the intermediate layer is a position of 1/8 or more and 1/3 or less from the outer peripheral surface with respect to the thickness of the filter medium in the stacking direction.
[0023]
In the method for cleaning a filter medium of the present invention, a material having performance according to the use is selected as the nonwoven fabric used. At this time, considering cost, chemical resistance, etc., it is desirable that the fiber is made of polyolefin fibers made by blending various copolymers with polypropylene, polyethylene, propylene or ethylene.
[0024]
In the asymmetrical cylindrical filter medium used in the present invention, at least the non-woven fabric of the outer peripheral layer has heat-fusible fibers and the layers having the heat-fusible fibers are integrated by the heat-fusible fibers. is necessary.
[0025]
The heat-fusible fiber is a fiber made of two kinds of thermoplastic resins having a core part and a surface layer part, and the melting point of the resin constituting the surface part is lower than the melting point of the resin constituting the core part. Yes, when heated to a temperature at which the core part does not melt and a temperature at which the surface layer part melts, the heat-fusible fibers are fused, but at this time, the shape of the fibers and the space formed by the fibers are maintained. Therefore, the pressure loss does not increase or the filtration performance does not deteriorate, the layers formed by laminating the nonwoven fabric can be integrated, and the filter medium can be easily separated from each other, and can be rigid. Can be high.
[0026]
In addition, when the nonwoven fabrics are bonded with an adhesive or the like, there is a concern about the contamination of the adhesive component of the filtrate, and the gap between the nonwoven fabric fibers is blocked by the adhesive, so that the filtration accuracy may deteriorate. The filtration performance itself may be deteriorated.
As such a heat-fusible fiber, a fusible fiber having a central portion made of polypropylene and an outer layer portion made of polyethylene is generally available.
[0027]
In the cylindrical filter medium having an asymmetric structure used in the present invention, if the fibers constituting the nonwoven fabric are too thick, sufficient filtration performance may not be obtained. If the fibers are too thin, pressure loss increases, and the necessary filtration flow rate cannot be obtained. There is a case. A desirable range of fibers to be used is 0.5d to 10d. Moreover, it is desirable that the length of the fiber to be used is 3 mm or more and 40 mm or less, and if it is less than 3 mm, the strength required for the cylindrical filter medium is lowered, and if it exceeds 40 mm, the workability may be deteriorated.
[0028]
Here, a cylindrical filter medium having an asymmetric structure used in the present invention will be described with reference to the model partial sectional view of FIG.
[0029]
This filter medium is cylindrical and has an outer circumferential layer formed by laminating a low-weight nonwoven fabric, an intermediate layer having a high-weight nonwoven fabric, and an inner circumferential layer formed by laminating a low-weight nonwoven fabric in this order. The basis weight of the nonwoven fabric with a high basis weight 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 center in the thickness direction of the intermediate layer is the thickness in the stacking direction of the filter media With respect to the thickness D, the nonwoven fabric of at least the outer peripheral layer is disposed at a position 1 from the outer peripheral surface, and the layer having the heat-fusible fiber is formed by the heat-fusible fiber. 1 is a D / 10 or more and D / 3 or less. The thickness d of the intermediate layer is in a range where an outer peripheral layer of D / 15 or more and D / 3 or less exists. In addition, it is desirable that the thickness of the outer peripheral layer (the thickness is represented by 1−d / 2) is secured to 1/10 or more of the thickness D in the stacking direction of the entire filter medium, and more desirably 1 / 8 or more.
[0030]
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 fluid during backwashing is reversed. As described above, the backwashing effect is very high in the cylindrical filter medium having an asymmetric structure. This is considered to be because the intermediate layer functions as a kind of nozzle.
[0031]
The nozzle effect of this intermediate layer will be described using the model diagram of FIG.
Since the “eye” of the nonwoven fabric having a high basis weight in the intermediate layer is smaller than the “eyes” of the nonwoven fabric having a low basis weight in the outer peripheral layer or the inner peripheral layer, a kind of bottleneck is formed with respect to the fluid as shown in FIG. In the filtration step, unnecessary substances are accumulated in a layer above the intermediate layer (dark hatched portion) in the figure. During backwashing, when fluid reaches this bottleneck, the fluid concentrates on this bottleneck as shown by the arrow in the figure, so the flow velocity increases at that part, and on the upper side of the intermediate layer in the figure. Since the accumulated insoluble matter is washed away vigorously, it is considered that the cleaning efficiency is increased.
[0032]
Here, FIGS. 3A and 3B show model cross sections of the cylindrical filter medium having an asymmetric structure.
[0033]
FIG. 3A shows an example in which the intermediate layer is arranged near the outer periphery, and FIG. 3B shows an example in which the intermediate layer is arranged near the inner periphery. In the present invention, a cylindrical filter medium having an asymmetric structure in which the intermediate layer of FIG.
[0034]
Since the nonwoven fabric of at least the outer peripheral layer has heat-fusible fibers and the layer having the heat-fusible fibers is integrated by the heat-fusible fibers, the intermediate layer is deformed even during backwashing. Therefore, the cleaning can be performed efficiently without making the pressure inside and outside the filter medium the same.
[0035]
Such a cylindrical filter medium can be produced, for example, as follows.
The core part and the surface layer part are fibers made of two types of thermoplastic resins, and the melting point of the resin constituting the surface layer part is made of a heat-fusible fiber that is lower than the melting point of the resin constituting the core part. A nonwoven fabric (low-weight nonwoven fabric) is wound around the core as shown in FIG. At this time, the layers are densely stacked while rotating around the core while heating by hot air, by infrared rays or far infrared rays, or by contacting a heated roller or the like heated to the nonwoven fabric.
[0036]
At this time, it is necessary to adjust the temperature so that the temperature becomes too high so that the entire heat-fusible fiber does not melt and the nonwoven fabrics are sufficiently adhered to each other. For example, when heating with hot air using a non-woven fabric made of a heat-fusible fiber with a core part made of polypropylene and a surface layer part made of polyethylene, hot air at a temperature of usually 120 ° C. or higher and 150 ° C. or lower is used, depending on the speed during winding. adjust.
[0037]
Once a predetermined amount (up to a predetermined thickness) is laminated, the intermediate layer is then laminated in the same manner, except that a non-woven fabric made of high-bonding heat-sealable fibers is used and the intermediate layer is densely laminated on the inner layer produced above. It forms (refer FIG.4 (b)).
[0038]
Next, similarly, however, a predetermined amount of a non-woven fabric made of heat-fusible fibers with a low basis weight is wound tightly on the intermediate layer to form an outer peripheral layer (see FIGS. 4 (c) and 4 (d)), Finally, remove the core material.
[0039]
Thus, a nonwoven fabric composed of fibers made of two types of thermoplastic resins having a core part and a surface layer part, wherein the melting point of the resin constituting the surface layer part is lower than the melting point of the resin constituting the core part, By winding and laminating the core material while heating, it is possible to easily and efficiently produce the excellent cylindrical filter material according to the present invention. In this case, there is no separation between the nonwoven fabrics, and the holder or the reinforcing material. Even if there is not, it can have sufficient intensity | strength and rigidity as a cylindrical filter medium, and can be set so that it may not swell or crush at the time of filtration or backwashing.
[0040]
The filtering medium cleaning method according to the present invention can be applied to a filtering 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 will be described later. However, it may be made of polypropylene reinforced with glass fiber). Its shape is cylindrical. The filtration container A is composed of an upper pipe connection portion Aa, an intermediate tube portion Ab, and a lower pipe connection portion Ac, which are connected by flanges. The upper and lower bottom cylindrical pipe connection portions Aa and Ac are the same shape members (common members), and are formed from the same mold, which is advantageous in terms of productivity and mold production costs.
[0041]
FIG. 6 shows an example of the bottomed cylindrical pipe connection portion Ac as an exploded model diagram in which the funnel-shaped slurry mud collector 3a having a hole on the lower side is removed.
[0042]
The bottomed tubular pipe connection portion Ac has a pipe connection port to which pipes can be connected, that is, a drain discharge outlet A2 and a filtered liquid introduction port A3. The drain discharge outlet A2 is provided inside the pipe connection portion. The bottom end of the pipe connection part is connected to the bottomed cylindrical partition part 3, and the filtered liquid introduction port A3 is connected inside the pipe connection part and outside the partition part. A funnel-shaped slurry mud collector 3a is fixed on the bottomed tubular partition 3 by bonding (it may be fixed by bolts instead of bonding).
[0043]
The funnel-shaped slurry mud collector 3a is disposed so as to be positioned below the cylindrical filter medium 1 having an asymmetric structure (hereinafter also referred to as "cylindrical filter medium 1"), but is formed in a funnel shape having an opening on the upper side and a hole on the lower side. The area of the hole 3a1 at the bottom of the funnel-shaped slurry mud collector 3 is considerably smaller than the cross-sectional area of the cylinder of the bottomed partitioning portion 3 of the lower pipe connection portion, which is 1/3 in this example. .
[0044]
The bottom hole 3a1 is small as described above. Furthermore, when viewed from the bottomed cylindrical partition 3 side, the bottom surface of the funnel-shaped slurry mud collector 3a is “barbed”. ) -Like structure, it is difficult to return to the filter medium side space of the filtration container A even if insoluble matter remains in the bottomed cylindrical partition 3.
[0045]
A plurality of cylindrical filter media 1 having an asymmetric structure are arranged in the filtration container A so that the length direction is vertical, and the lower ends thereof are sealed with polypropylene.
[0046]
A cylindrical filter medium 1 having an asymmetric structure is shown in FIG. 3A as a model of its cross section, and is manufactured by the method shown in FIG. The low density nonwoven fabric used has a basis weight of 20 g / m ² , is a nonwoven fabric made of heat-bonded fibers (2 denier) with a core part of polypropylene and a surface layer part of polyethylene, and a high density nonwoven fabric has a basis weight of 40 g / m 2. ² is a non-woven fabric made of polypropylene fibers (2 denier), and is rolled up using hot air at 160 ° C. and laminated.
[0047]
The cylindrical filter medium 1 having an asymmetric structure has an inner diameter of 10 mm, an outer diameter of 20 mm, an intermediate layer thickness of 0.5 mm, and the center of the intermediate layer at a position 1.5 mm from the outer periphery. Note that the number of windings of the high-density nonwoven fabric in the intermediate layer is two rounds (actually over two rounds because there are some overlapping parts). The length of the asymmetrical cylindrical filter medium is 60 cm.
[0048]
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 a through hole 2a corresponding to the hollow portion 1a of the cylindrical filter medium 1 having an asymmetric structure.
[0049]
The upper side of the intermediate plate 2 is provided inside the bottomed tubular pipe connection portion Aa, and is connected to a bottomed tubular partition portion 2b that shares the bottom and bottom of the pipe connection portion Aa. The bottomed cylindrical partition 2b is connected to a filtrate outlet / gas inlet A1 provided at a position higher than the cylindrical filter medium 1 having an asymmetric structure of the filtration container wall (which will be clarified in the description below). The filtrate outlet / gas inlet A1 is provided downstream of the cylindrical filter medium 1 in the flow direction of the liquid to be filtered. In this example, the filtrate outlet / gas inlet is provided, but the filtrate outlet and the gas inlet may be provided separately.
The pipe connection portion Aa is the same as the pipe connection portion Ac shown in FIG. 6, but is used upside down.
[0050]
A filtered liquid inlet A3 is provided outside the bottomed cylindrical partition 3 and at the bottom of the pipe connection part Ac (position upstream of the cylindrical filter medium 1 in the flow direction of the filtered liquid). Yes.
[0051]
The position of the to-be-filtered treatment liquid inlet A3 is such that the liquid supplied from there into the filtration container A does not hit the upper surface of the funnel-shaped slurry mud collector 3a described later. It is preferable at the point which exhibits the effect of this, and it normally provides in the side part near a bottom part or a bottom part. In this example, it is provided on the side surface close to the bottom.
[0052]
In the above, the area of the gap between the edge (maximum diameter portion) of the funnel-shaped slurry mud collector 3a and the inner wall of the container A is the cross-sectional area of the pipe connected to the filtered liquid inlet A3 introduced into this container. In comparison, it may be 1 or more times, preferably 1.5 or more times. If this ratio is less than 1 time, the flow velocity of the liquid flowing through the gap is increased, and as a result, the residual insoluble matter inside the bottomed cylindrical partition 3 of the lower pipe connection portion is swollen so as to have an asymmetric structure. It may reattach to the surface of the cylindrical filter medium and increase the load during filtration, or the flow may cause an unexpected failure in the cylindrical filter medium 1 having a plurality of asymmetric structures.
[0053]
On the other hand, if the ratio is too large (more than 5 times), the filter aid from the plurality of asymmetrical cylindrical filter media 1 and the slurry of insoluble matter filtered thereby are introduced into the filtered liquid from this gap. At the time of the liquid beam process described later, unnecessary substances at that time are supplied to a plurality of asymmetrical cylindrical filter media 1 in which a filter layer is not formed, and downstream thereof. Leakage or a load on the cylindrical filter medium 1 having an asymmetric structure is increased.
[0054]
In this example, the inner diameter of the container A is 30 cm, the maximum diameter of the funnel-shaped slurry mud collector 3a is 28.8 cm, and the thickness of the pipe connected to the filtered liquid introduction port A3 is 5 cm.
The drain discharge outlet A2 is provided at a position at the bottom of the filtration container and upstream of the cylindrical filter medium, and is connected to a drain tank (not shown) via a drain valve V7.
[0055]
Further, outside the top of the filtration container A and the bottomed cylindrical partition 2b of the wall of the filtration container A, a position higher than the top of the filtration surface of the cylindrical filter medium 1 (and the flow of the liquid to be filtered with respect to the cylindrical filter medium 1) An air vent A4 is provided at a position upstream of the direction).
[0056]
The filter aid tank 4 is provided with a predetermined amount of filter aid such as diatomaceous earth dispersed in a small amount of water as necessary (amount necessary for one filter aid layer forming step: filtration). The end of the filter aid layer forming step can be known when the filter aid in the auxiliary agent tank 4 runs out). As will be described later, the filter aid is supplied to the surface of the cylindrical filter medium 1 having an asymmetric structure and stays and accumulates there to become a so-called “attached state”, thereby improving the filtration ability and the cylindrical filter medium 1 having an asymmetric structure. It has the function of making it possible to remove an insoluble matter that is smaller than the original ability of.
[0057]
The to-be-filtered treatment liquid inlet A3 of the filtration container is connected to the outlet side of a pump that sends the liquid into the filtration container.
There is a filter aid tank 4 outside the filter container A, and a filter aid line L5 for introducing liquid from the filter aid tank to the inlet side of the pump 5p is provided at the bottom of the filter aid tank 4, and the filter aid tank The line L5 has a filter aid valve V5 for opening and closing the filter aid line L5.
[0058]
Moreover, the to-be-filtered liquid tank 6 containing the to-be-filtered liquid is connected to the pump inlet side by the to-be-filtered liquid supply line L1. A valve V1 is provided.
[0059]
The air vent A4 of the filtration container A is provided at a position higher than the top of the filtration surface of the cylindrical filter medium 1, and is connected to the filter aid tank 4 by an air vent line L4. This air vent line L4 has a pressure gauge 5b and an air vent valve V4 for opening and closing the air vent line L4.
[0060]
The filtrate outlet of the filtration container A (filtrate outlet / gas inlet A1 in this example) is connected to the filter aid tank 4 by a return line L8, and opening and closing of the return valve V8 connected to the return line L8 If necessary, the filtrate filtered by the cylindrical filter medium 1 having an asymmetric structure is supplied to the filter aid tank 4 from above. At this time, the filter aid (diatomaceous earth, etc., mixed with water to form a slurry) in the filter aid tank 4 is stirred by the momentum of the liquid flow, and is uniformly dispersed in the liquid. .
[0061]
Further, the filtrate outlet of the filtration container A (in this example, the filtrate outlet / gas inlet A1) includes a filtrate outlet line L2 provided with a filtrate outlet valve V2 that can be opened and closed, and a precoat valve V3 that can be opened and closed. Connected to the precoat line L3. The precoat line L3 is further connected to the inlet side of the pump 5p.
[0062]
Further, the gas inlet of the filtration container A (the filtrate outlet / gas inlet A1 in this example) was adjusted to an appropriate pressure by an air supply line L6 (regulator (not shown)) having an openable / closable air supply valve V6. Compressed air is supplied).
[0063]
As described above, the filtration device shown in FIG. 5 is a filtration device having an upper liquid collection type filtration container A in which a filtration material is housed, and a cylindrical filtration material 1 in which a nonwoven fabric is densely wound is used as the filtration material. The filtration container A has a filtration treatment liquid inlet A3 at a position upstream of the cylindrical filter medium 1 in the flow direction of the filtration treatment liquid, and is located at the bottom of the filtration container and upstream of the cylindrical filter medium. Drain discharge outlet A2, the same as or higher than the cylindrical filter medium 1, and the air vent A4 and the cylindrical filter medium 1 at a position upstream of the cylindrical filter medium 1 in the flow direction of the liquid to be filtered. And a filtrate outlet / gas inlet A1 at a position that is higher than the cylindrical filter medium 1 and downstream in the flow direction of the filtrate to be filtered. In contact with the outlet of pump 5p A return line L8 for introducing the filtrate from the filtrate outlet / gas inlet A1 of the filtration container A to the filter aid tank 4 and the return line L8. A return valve V8 for opening and closing, a filter aid line L5 for introducing liquid from the filter aid tank 4 to the inlet side of the pump 5p, and a filter aid valve V5 for opening and closing the filter aid line L5, The filtration apparatus has a precoat line V3 for introducing a liquid from the filtrate outlet V2 of the filtration container A to the inlet side of the pump 5p and a precoat valve V3 for opening and closing the precoat line.
[0064]
The operation of this filtration device will be described first from the liquid pouring step.
From the state where the pump 5p is stopped and all the valves V1 to V8 are closed, the inlet valve V1, the air vent valve V4 and the return valve V8 are opened, and then the pump 5p is operated.
The liquid to be filtered in the liquid tank 6 to be filtered is introduced into the filtration container A from the liquid inlet A3 through the liquid to be filtered supply line L1 by the pump 5p and reaches the upper end of the container (liquid The beam begins to be discharged from the air vent A4 through the air vent line L4 to the filter aid tank 4. Further, the filtrate that has passed through the cylindrical filter medium 1 having an asymmetric structure is discharged to the filter aid tank 4 through the return line L8 via the filtrate outlet / gas inlet A1.
[0066]
After completion of the liquid application step, a filter aid layer forming step is performed. That is, the precoat valve V3 and the filter aid valve V5 are immediately opened, and the inlet valve V1 and the air vent valve V4 are closed. At this time, the liquid in which the filter aid is dispersed is introduced from the bottom of the filter aid tank 4 through the filter aid line L5 and the pump 5p into the filtration container A through the filtered treatment liquid inlet A3, and the cylindrical filter medium having an asymmetric structure. The diatomaceous earth is filtered on the surface of the diatomaceous earth, and the filtered filtrate returns to the filter aid tank 4 from the filtrate outlet / gas inlet A1 via the return line L8. At this time, since the dispersion concentration of the filter aid supplied from the filter aid tank 4 is high, it is more appropriate for the filtrate from the filtrate outlet / gas inlet A1 supplied to the pump 5p inlet side via the precoat line L3. Adjusted to a suitable dispersion concentration.
[0067]
By such circulation, the filter aid in the filter aid tank 4 is sequentially supplied into the filtration container A, 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. Thus, a filtration layer is formed that can remove even minute insolubles that cannot be separated by a single cylindrical filter medium 1 having an asymmetric structure.
[0068]
Thus, after the filter aid layer by the filter aid is formed on the outer periphery of the cylindrical filter medium 1 having the asymmetric structure, the filtration step is started.
[0069]
When the filter aid valve V5 and the return valve V8 are closed, the inlet valve V1 and the filtrate outlet valve V2 are 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 cylindrical filter medium 1 having an asymmetric structure (and the filter layer formed by 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 discharged.
[0070]
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 compressed air adjusted to an appropriate pressure supplied from the air supply line L6 is filtered. A is introduced from the filtrate outlet / gas inlet A1 into A and passes through the through hole 2a of the intermediate plate 2 and the cylindrical filter medium 1 having an asymmetric structure from the bottomed cylindrical partition 2b, and the liquid in the container A is drained. Press down to V7 and drain. Thus, since the drain outlet A2 which is the outlet is opened simultaneously with the supply of the compressed air in the container, the filtration container A does not need to be a pressure resistant container, and is inexpensive and workable as in this example, for example. It can be made of easy polypropylene.
[0071]
The clear filtrate present in a part of the line and the bottomed cylindrical partition 2b flows backward, and this flow also flushes the filter aid layer attached to the surface of the cylindrical filter medium 1 having an asymmetric structure (backwashing). ) As a drain with a lot of impurities, it is guided to the partition 3 while being collected by the funnel-shaped slurry mud collector 3a, and is discharged from the drain discharge outlet A2 to the external drain tank (not shown) via the drain line L7. The
[0072]
As described above, the liquid application process, the filter aid layer forming process, the filtration process, and the discharge process are repeated.
[0073]
In the above, since the cylindrical filter medium 1 having an asymmetric structure is used, even when the pressure difference between the internal space and the outside is large at the start of discharge, the filter medium is high in rigidity, so that it does not swell or be destroyed, There is no adverse effect. Therefore, when discharging the liquid in the filtration container A, it is possible to pressurize the liquid with the gas at the same time as opening the outlet of the filtering container or immediately after opening the outlet. At this time, since it is not necessary to use a pressure vessel assuming that pressure is applied to the filtration vessel A itself, the production cost of the vessel can be reduced, and it is used for depressurization of the air supply line 5d (generally high pressure). Even if the regulator breaks down, it is possible to prevent an accident in which the filtration container is ruptured or damaged.
[0074]
Further, the pressure inside the container just before the end of the filtration process is checked with the pressure gauge 5b, and the above discharge process is performed using an extruded gas having a pressure lower than that pressure, so that an unnecessarily high pressure gas is not used. Therefore, energy consumption can be reduced, and the impact applied to the filtration container and the filtering material in the discharging process can be minimized.
[0075]
When the liquid is allowed to flow in the direction opposite to that during filtration due to the pressure of the compressed gas after the filtration step, simultaneously with the opening of the outlet of the filtration container or immediately after the opening of the outlet. In addition, since the liquid is pressurized with the gas, air does not enter from the outlet, so that the cleaning (back washing) effect at the time of discharging is high and a stable effect can be obtained.
[0076]
【The invention's effect】
The filter medium cleaning method of the present invention is a cylindrical filter as a filter medium in the filter medium cleaning method in which a liquid is flowed in a direction opposite to the time of filtration with respect to the filter medium accommodated in the filter container due to gas pressure after the filtration step. And having an outer circumferential layer formed by laminating a low-weight nonwoven fabric, an intermediate layer having a high-weight nonwoven fabric, and an inner circumferential layer formed by laminating a low-weight nonwoven fabric in this order, The basis weight of the nonwoven fabric 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 center in the thickness direction of the intermediate layer is the outer peripheral surface with respect to the thickness of the filter medium in the stacking direction. Or it arrange | positions so that it may be in the position of 1/10 or more and 1/3 or less from the upstream surface of the flow direction of a to-be-filtered process liquid among internal peripheral surfaces, and the flow of the to-be-filtered process liquid at least an outer peripheral layer or an internal peripheral layer The nonwoven fabric of the upstream layer in the direction has heat-fusible fibers Using a cylindrical filter medium having an asymmetric structure in which the layer having the heat-fusible fiber is integrated with the heat-fusible fiber, and when the liquid is pressurized with gas, the filtration container is discharged simultaneously with the pressurization. Because the outlet is opened, the pressure-resistant design value of the filtration container can be lowered, so that a low-cost container can be used, safety is high, and inspections required for pressure containers can be omitted. It is an excellent method for cleaning filter media.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view of a model of a cylindrical filter medium having an asymmetric structure 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 for illustrating two types of cylindrical filter media having an asymmetric structure.
(A) It is a figure which shows the example by which the intermediate | middle layer is distribute | arranged near outer periphery.
(B) It is a figure which shows the example by which the intermediate | middle layer is distribute | arranged near inner periphery.
FIG. 4 is a model diagram illustrating a method for producing an example of a cylindrical filter medium having an asymmetric structure.
FIG. 5 is a view showing a filtration apparatus to which the filter medium cleaning method according to the present invention can be applied.
FIG. 6 is an exploded model diagram showing an example of a bottomed tubular pipe connection portion from which a funnel-shaped slurry mud collector 3a having a hole on the lower side is removed.
[Explanation of symbols]
A Bottomed cylindrical pipe connection part Ab on the filtration container Aa Middle cylindrical part Ac Bottomed cylindrical pipe connection part A1 Filtrate outlet / gas inlet A2 Drain outlet A3 Filtered liquid inlet A4 Air Opening port 1 Cylindrical filter medium 1a with asymmetric structure Hollow part 2 of cylindrical filter medium 1 Intermediate plate 2a Through hole 2b Partition part 3 Partition part 3a Slurry collector 4 Filter aid tank 5b Pressure gauge 5p Pump 6 Filtration liquid tank L1 Cover Filtration liquid supply line L2 Filtrate outlet line L3 Precoat line L4 Air vent line L5 Filter aid line L6 Air supply line L7 Drain line L8 Return line V1 Inlet valve V2 Filtrate outlet valve V3 Precoat valve V4 Air vent valve V5 Filtration aid Agent valve V6 Air supply valve V7 Drain valve V8 Return valve

Claims (1)

Regarding the cleaning method of the filter medium that causes the liquid to flow in the opposite direction to the time of filtration with respect to the filter medium stored in the filter container due to the pressure of the gas after the filtration step,
As a filter medium, it has a cylindrical outer layer formed by laminating a nonwoven fabric with a low basis weight, an intermediate layer having a nonwoven fabric with a high basis weight, and an inner circumferential layer formed by laminating a nonwoven fabric with a low basis weight in this order, The basis weight of the nonwoven fabric with a high basis weight 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 center in the thickness direction of the intermediate layer is the thickness in the stacking direction of the filter media On the other hand, the outer peripheral surface or the inner peripheral surface is arranged so as to be at a position of 1/10 or more and 1/3 or less from the upstream surface in the flow direction of the liquid to be filtered, and at least of the outer peripheral layer or the inner peripheral layer Cylindrical filter medium having an asymmetric structure in which the non-woven fabric of the upstream layer in the flow direction of the liquid to be filtered has heat-fusible fibers and the layers having the heat-fusible fibers are integrated by the heat-fusible fibers. And
A method of cleaning a filter medium, comprising pressurizing the liquid with the gas simultaneously with opening of the outlet of the filtration container or within 2 seconds of opening of the outlet.

Images