JPH07719A - Filter cloth of filter press - Google Patents

Abstract

PURPOSE:To improve the filtration characteristics of a filter press and durability of a filter cloth. CONSTITUTION:In the filter cloth for the filter press provided with at least one piece of the filter cloth 14a arranged in the filter press and having one face to which a treating solution is supplied and the other face pressed to a filter plate having many discharge grooves and from which the filtrate is discharged, a cloth 14b for back-up is superposedly arranged at the other face side of the filter cloth.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used to dehydrate sludge discharged from a sewage treatment apparatus or an industrial wastewater treatment apparatus including a plating waste liquid, and as a filtration apparatus or a dehydration apparatus in various production processes. It relates to a filter cloth for use in a filter press (pressurizer).

[0002]

2. Description of the Related Art As a conventional filter press, a plurality of filter plates each having a recess for forming a cake forming chamber on its side surface, and a treatment liquid inlet on each side surface thereof are arranged in parallel with the filter plate. A plurality of intermediate plates forming a cake production chamber on both sides of the recess by covering the recess with the both sides, a filter cloth stretched between the filter plate and the intermediate plate in the cake production chamber, and the treatment The present inventor has proposed a device including a means for supplying the processing liquid into the cake forming chamber through a liquid inlet (Japanese Patent Publication No. 62285/1990, Japanese Patent Publication No.
82, JP-A-1-155913, and JP-A-1-317.
507, JP-A-1-317509, JP-A-3-2380.
07 etc.) The filter presses of these prior applications have an excellent filtering property that the cake can be scraped off and thus continuous operation can be performed all day.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a filter cloth which can be used in a filter press to further improve the filtration characteristics such as water content and to have a large degree of dewatering capacity with less clogging of the filter cloth. With the goal. Moreover, it aims at providing a highly durable filter cloth.

[0004]

In order to achieve the above-mentioned object, in the present invention, the filter is arranged in a filter press, and the treatment liquid is supplied from one surface and the other surface is pressed against a filter plate having a large number of discharge grooves. At least 1 to drain the filtrate from the other side
In a filter press filter cloth including a single piece of filter cloth, a backup cloth is laid on the other side of the filter cloth.

In a preferred embodiment of the present invention, as a filter press, a plurality of filter plates having concave portions for forming a cake forming chamber on the side surfaces, and the filter plate having treatment liquid inlets on both side surfaces are provided. A plurality of intermediate plates which are arranged in parallel and cover the recesses with the both side surfaces to form cake generating chambers on both sides thereof, and a filter which is stretched between the filter plate and the intermediate plates in the cake generating chamber. A filter press having a cloth and a means for supplying the processing liquid into the cake forming chamber through the processing liquid inlet is used, and the backup cloth for the filter cloth is a monofilament having higher fluid permeability than the filtering cloth. I use cloth.

As the back-up cloth, a cloth woven from a thicker thread that is less stretchable than the filter cloth, a cloth having a different weave from the filter cloth, the filter cloth and the weave and the size of the mesh. A cloth having substantially the same thickness (fluid permeability) can also be used. However, when the backup cloth is a cloth having a different weave from the filter cloth, the fluid permeability thereof is preferably larger than that of the filter cloth. Further, when the backup cloth is a cloth having substantially the same weave and mesh size as the filter cloth, the backup cloth needs to be overlapped so that the texture crosses the texture of the filter cloth. .

[0007]

According to the present invention, by stacking a plurality of cloths having a specific relationship, these cloths act synergistically to improve the filtration characteristics.

In the filter press, the filter cloth is pushed into the groove 51 as shown in FIG. 3 (b) during the feeding of the treatment liquid, but when the treatment is interrupted or completed, the treatment liquid is fed. When stopped, it is considered that the pressed filter cloth tries to return to a flat state, and the tension thereof squeezes the cake to further reduce the water content of the cake. The present inventor expected that if the tension of the filter cloth is increased by laminating a plurality of cloths for filtration (filter cloth), the squeezing action will be stronger, but if the cloths of the same kind are simply laminated, one cloth is obtained. There was no significant difference in the water content of the cakes produced compared to the filter cloths composed of. A twill weave is usually used as the filter cloth, but if twill weave cloths are simply piled up, the crests of one of the cloths will enter the troughs of the other cloth, It is considered that this is because the cloth is clogged and the filter cloth is less likely to be deformed, which hinders the filter cloth from returning to a flat state when the processing liquid feeding is stopped.

In the present invention, the throttling action can be enhanced by backing up the filter cloth from the outside (filter plate side).

In a first aspect of the invention, a tight filter cloth is backed by a cloth that has less elongation than the filter cloth and is woven with thick threads (ie, has a high fluid permeability), such as a monofilament cloth.

In order to perform more precise filtration, a filter cloth having a fine mesh, that is, a low fluid permeability is used. However, since such a filter cloth is woven using thin threads, its strength is weak and there is a problem that it cannot withstand long-term use.
Such a filter cloth is woven with thick threads, that is, when the cloth with coarse mesh and high fluid permeability is backed up, the backup cloth receives the filter pressure through the filter cloth, so only the compressive pressure is applied to the filter cloth and the tensile force is applied. It doesn't break, so it won't break. Further, when the filtration pressure is released, the tension of the backup cloth exerts a squeezing action on the cake, and the water content of the cake is reduced as compared with the case where the backup cloth is not used.

The above combination is also advantageous in that the filter cloth made of a desired material can be selected relatively freely. For example, Teflon has the advantages that it is chemically stable, is not easily corroded by chemicals, and has a good filter cloth separation for cakes.However, Teflon filter cloth is expensive, thick ones are not commercially available, and they do not grow well. It is large and therefore has a disadvantage that the stretched portions are overlapped with each other and breakage occurs and the breakage portion is easily broken. On the other hand, although Tetoron is chemically more unstable than Teflon, it has a small elongation, and various Tetoron cloths with thin to thick threads are commercially available.

Therefore, a Teflon filter cloth woven with a thread thicker than that of the Teflon filter cloth is laid on the outer side (filter plate side) of the Teflon filter cloth to filter even corrosive liquid substances. Can be performed mainly with fine Teflon filter cloth, and by backing up the Teflon filter cloth with the outer Tetron filter cloth, it is possible to prevent the Teflon filter cloth from stretching and prevent breakage and tear. it can. Further, by using a filter cloth made of thick yarn as the Tetoron filter cloth, it is possible to have sufficient durability against corrosive substances such as chemicals.

In the second aspect of the present invention, the filter cloth is backed up by a cloth having a different weave. Further, in the third aspect of the present invention, a cloth substantially the same as the filter cloth is arranged as the backup cloth so that the weave of the cloth intersects that of the filter cloth.

According to the above construction, the water content of the cake produced is reduced by 3 to 10% as compared with the conventional example using only the filter cloth. This is because the two cloths only contact each other at the peaks of the texture, so the mesh as the filter cloth is not blocked,
Moreover, it is considered that the filter cloths on the filter plate side back up the tension of the filter cloth and the squeezing action for squeezing the water content of the cake becomes stronger without hindering each other from exerting the tension of the cloth.

As a filter press which stretches the filter cloth doubly, it is known that a protective cloth is stretched on the inside of the filter cloth, but the protective cloth has an extremely coarse mesh than the filter cloth. It is for the purpose of protecting the product and improving the packing property, and does not aim to reduce the water content of the produced cake. Also, it seems that the same cloth is stretched doubly, but this is simply a stack of the same cloth as mentioned above in order to increase the strength, and it reduces the moisture content of the produced cake and No significant improvement in filtration efficiency is observed as compared with the present invention.

[0017]

EXAMPLE An example of a filter press for dehydrating sludge as a treatment liquid will be described below. However, the treatment liquid of the present invention is not limited to sludge.

1 to 3 show the structure of a filter press according to an embodiment of the present invention. An intermediate plate 12 is arranged in parallel with each filter plate between a pair of filter plates 11. A projecting edge portion 25 is formed on both sides of the filter plate 11, and a recess 24 is formed by being surrounded by the projecting edge portion 25. The recesses 24 are sealed by bringing the filter plates 11 close to the intermediate plate 12 and pressing the projecting edge portions 25 against the intermediate plate 12, so that the filter plates 11 and the intermediate plate 1 are sealed.
A cake production chamber 13 is formed between the two. Each filter plate 11
Between the intermediate plate 12 and the intermediate plate 12, a fine filter cloth (having low fluid permeability) 14a is disposed on the intermediate plate 12 side.
A backup cloth 14b woven with a monofilament thicker than the weaving thread of the filter cloth 14a (thus having high fluid permeability) is disposed on one side.

A large number of grooves 51 as shown in FIG. 3 (b) are provided in parallel at the bottom of the recess 24 of the filter plate 11, but the filter cloths 14a, 14b are as shown in FIG. 3 (a). , Their texture directions are arranged so as to intersect the groove 51 at an angle of approximately 45 ° and at an angle of approximately 90 °.

Each of the filter plates 11 is vertically arranged and movable in the horizontal direction, and has a cake producing position close to the intermediate plate 12 (state shown in FIG. 1) and a cake discharging position away from the intermediate plate 12. (The state of FIG. 2) can be moved.
The intermediate plate 12 is provided with a mud feed port 15 that opens on both sides. The mud feed port 15 is provided with a mud feed pump 16 via a mud feed pipe 26.
Connected with. A cake scraping device 17 is provided above the intermediate plate 12. This cake scraping device 1
7 includes an arm 18 and a blade 19 provided at the tip of the arm 18, and the arm 18 is connected to a piston 21 of an air cylinder 20. By driving the air cylinder 20, the arm 18 slides vertically along the both surfaces of the intermediate plate 12 together with the blade 19. The upper ends of the cloths 14a and 14b are connected to the arm 1 via support members 27a and 27b, respectively.
Connected to eight. Weights 22a and 22b are attached to the lower ends of the cloths 14a and 14b, respectively. Filter plate 11
Stainless steel wires 23a and 23b for bending the cloths 14a and 14b are respectively stretched below.

The operation of the filter press having the above structure will be described below. First, as shown in FIG. 1, the filter plate 11 is brought close to the intermediate plate 12, and the filter plate 11 is fixed at the closed cake forming position. In this state, the mud feed pump 16 is driven to press the sludge into the cake production chambers 13 on both sides of the intermediate plate 12 through the mud feed port 15. The sludge press-fitted is the cloth 14a,
The water is dehydrated and filtered by 14b, and the filtered water is discharged to the outside through a drainage groove 51 (FIG. 3) provided in the filter plate 11 on the back surface of the backup cloth 14b.

When the sludge after the dehydration treatment fills the cake generation chamber 13 as a cake, the filtration efficiency suddenly decreases. This can be detected as the processing solution feed pressure or the processing solution or filtrate flow rate. In that case, first, the feeding of the processing liquid is stopped. As a result, the filter cloth pushed into the groove as shown in FIG. 3B tends to return to a flat state due to the feed pressure of the treatment liquid, and the tension causes the cake to be squeezed to reduce the water content. Is generated. At this time, as shown in FIG. 3 (a), the filter cloths 14a and 14b are formed so that the weave directions thereof intersect with each other at about 90 °, and the groove 51 provided at the bottom of the recess 24 of the filter plate 11.
By arranging so as to intersect at approximately 45 °, a more suitable diaphragm effect can be exhibited.

When the feeding of the processing liquid is stopped, as shown in FIG. 2, the filter plate 11 is separated from the intermediate plate 12 and the cake discharge position in the open state is entered. In this state, the air cylinder 20
Is driven to push down the arm 18 through the piston 21 as shown by arrow B. Thereby, the blade 19 at the tip of the arm 18 slides along both surfaces of the intermediate plate 12 to scrape off the cake on the surface of the central plate. At this time, the cloths 14a and 14b are also pulled downward by the weights 22a and 22b at the same time and descend while being given an appropriate tension. Cloth 14 when descending
The a and 14b are slidably in contact with the protruding edge portion 25 at the lower end of the filter plate 11 and bent, and the cakes attached to the cloths 14a and 14b are stripped off. Further, the cloths 14a and 14b are made of stainless steel wire 23.
The cake remaining on the cloths 14a and 14b is scraped off by being slidably in contact with a and 23b and bending. Such a cake scraping operation may be repeated a plurality of times by repeating the reciprocating operation of the piston 21.

According to the present embodiment, the durability of the filter cloth is high even if the filter cloth with tight eyes is used. In addition, the filtration efficiency is high and the water content of the cake produced by the filtration is low.
The reason is as follows. That is, among the filter cloths, a narrow cloth must be used as the filter cloth having a large mesh, so that the thickness of the filter cloth becomes thin. Since such a filter cloth has a low tensile strength, it is very weak when used as a filter cloth as it is. However, when backing up with a monofilament cloth having a high fluid permeability, the monofilament cloth receives a filtering pressure through the filter cloth, so that the filter cloth receives only compressive pressure and no tensile force is applied, so that it does not break. Therefore, the durability of the filter cloth is improved. Then, when the pressure release valve opens, the pressure of the monofilament and the filter cloth, which had been compressed by the filtration pressure, disappears,
In order to return to the original thickness, the slurry is first extruded, and the cake is pressed between the cake and the intermediate plate to consolidate (press) the cake. Therefore, the water content of the produced cake can be reduced. If the filtration cloth is backed up with a monofilament cloth and filtration is performed, the filtrate that flows out through the filter easily passes through the monofilament cloth, and the convex portion and the concave portion of the filter plate contribute to the filtration regardless of the filtration area. Available for Therefore, the filtration efficiency can be improved.

[0025]

[Modification of Embodiment] In the above embodiment, one pair (two sheets) is used.
However, not limited to this, three or more filter plates are arranged in parallel and an intermediate plate is provided between the filter plates to increase the number of cake producing chambers and increase the processing capacity. Good.
In this case, it is desirable that the intermediate plate 12 and the air cylinder 20 be fixed to each other so as to be movable in the horizontal direction together with the filter plate 11. This improves the operability of the opening / closing operation of the filter plate.

Further, instead of the weights 22a and 22b for pulling the cloths 14a and 14b downward, a tension may be applied to the filter cloths by using a filter cloth pulling device or the like interlocking with a scraping device.

Further, in the above description, an example using two filter cloths is shown, but the number of filter cloths may be three or more.

Further, in the above description, when the filter press moves from the cake generation position to the cake discharge position, the wire 2 is applied to both the filter cloth 14a and the backup cloth 14b.
The cake is scraped off with 3a and 23b,
When the backup cloth 14b has a higher fluid permeability than the filter cloth 14a and the cake adheres to the backup cloth 14b due to the filtering operation due to the nature of the treatment liquid (sludge, etc.), the wire 23b may be omitted. Furthermore, the weight 22b may be omitted by sewing the filter cloth 14a and the backup cloth 14b at least at their lower ends.

In the above description, an example in which the present invention is applied to a type of filter press having an intermediate plate has been shown, but the present invention can also be applied to a type of filter press having no intermediate plate.

[0030]

Application Example of the Invention The present invention can be applied not only to sludge treatment but also to a filtering device and a dehydrating device in various production processes. For example, the cake or filtrate may be the final product or intermediate product.

[0031]

As described above, according to the present invention, by backing up the filter cloth from the filter plate side, the filter characteristics of the filter press are improved and the water content of the cake produced by filtration is reduced. Further, the strength and life of the filter cloth can be improved.

[Brief description of drawings]

1 and 2 are configuration diagrams of a filter press according to an embodiment of the present invention.

3A is a partially enlarged plan view of the filter cloth of the filter press of FIG. 1, and FIG. 3B is a cross-sectional view showing the relationship between the grooves of the filter plate and the filter cloth.

[Explanation of symbols]

11: filter plate, 12: intermediate plate, 13: cake production chamber, 14
a: filter cloth, 14b: backup cloth, 15: mud port,
31: cake, 51: groove.

Claims (1)

[Claims] 1. A filter cloth, which is disposed in a filter press and comprises at least one filter cloth which is supplied with a treatment liquid from one surface and is pressed against a filter plate having a plurality of discharge grooves on the other surface to discharge the filtrate from the other surface. A filter press filter cloth, wherein a backup cloth having a higher fluid permeability than the filter cloth is laid on the other side of the filter cloth.