JPH1028824A - Filter cloth - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain filter cloth which can filter fine particles and to which crystals can hardly adhere and accumulate by arranging the high density warp woven into the weft on the front layer side and the low density warp bonding the wefts on the front and the back layer sides to each other. SOLUTION: The warps 20, 21 and wefts 30, 31 are constituted from synthetic fibers such as fibers of polyester, nylon, etc. In filter cloth having wefts 30, 31 on both sides, the first warp 20 woven into the front side weft 30 is made high in density, while the second warp 21 bonding the wefts 30, 31 on the front and back layer sides to each other is made low in density. The density ratio between the first warp 20 and the second warp 21 is made to be 4:1-2:1. In the filter cloth, fine particles are filtered by the high density front layer side, the filtrate is allowed to pass to the back layer side, but since its density is low, a small quantity of water is retained, and an absolute quantity of crystals deposited during stop is small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter cloth which can be suitably used for a filter press or the like, and more particularly to a smooth and dense surface layer to improve cake peelability and a rough back layer to reduce clogging. The present invention relates to a filter cloth having an increased processing amount by preventing the same.

[0002]

2. Description of the Related Art Various filter cloths are used in filter presses according to their uses.
In general, filter cloths woven from monofilament yarns have high rigidity and excellent dimensional stability, durability and detergency, but because of the coarse weave, there is a limit to the fineness of the filterable particles. Not applicable for filtering fine particles. In addition, filter cloth woven from multifilament yarn and spun staple yarn (spun yarn)
On the other hand, it is excellent in collecting fine particles, but has the drawback that clogging easily progresses, the filtration speed is slow due to high filtration resistance, and the peelability of the cake is poor due to insufficient surface smoothness.

On the other hand, dewatering and filtration of solids using a filter press has recently been performed in a groundwater intake.
Since this dehydration filtration is carried out by so-called non-chemical injection without using a flocculant, the apparent solid particle diameter is very small, and the solid content concentration is often as low as 1% or less. For this reason, a filter cloth used for dewatering and filtering of groundwater must be woven with multifilament yarns having low air permeability because monofilament yarns have too high air permeability to filter small solids. However, since groundwater contains a large amount of iron ions and the like, the filter cloth for dewatering and filtering groundwater has a specific problem not found in the conventional filter cloth.

That is, when the dewatering and filtering operation of the groundwater by the filter press is stopped, the flow of water in the filter press is stagnated, and iron ions and the like contained in the groundwater come into contact with air to oxidize and crystallize. It is deposited on the back of the cloth. Although recent filter presses are designed to automatically clean the filter cloth,
Since this automatic cleaning is performed by spraying cleaning water from the surface layer side of the filter cloth, the precipitated crystals are not washed away on the back layer side of the filter cloth and accumulate with time. When the crystals adhere and accumulate in this way, drainage of the filter cloth deteriorates and the amount of precipitated crystals further increases, and eventually the filter cloth is clogged. As described above, the conventional filter cloth for dewatering and filtering of groundwater intake causes clogging of crystals, so that the life of the filter cloth is short and it is difficult to increase the throughput.

It is an object of the present invention to provide a filter cloth which can filter fine particles and in which deposition and accumulation of crystals on the filter cloth do not easily proceed.

[0006]

In order to solve the above-mentioned problems, a filter cloth according to the present invention is a filter cloth having double wefts on the front and back sides, and a high-density first warp woven into the surface side weft of the filter cloth. And a low-density second warp that connects the surface yarns and the back yarns of the filter cloth to each other. Thereby, the attachment of crystals can be effectively suppressed while filtering the fine particles.

That is, the fine particles are filtered on the surface side of the high density, and the filtrate from which the fine particles have been filtered flows through to the back layer side. On the back layer side, since the warp density is coarse, the fine particles are filtered on the back layer side. And the amount of water retained on the back layer side during stoppage of the filter press decreases. Therefore, the absolute amount of crystals precipitated during the stop of the filter press is reduced.

The drainage efficiency of the filtrate or washing water is improved, and the crystals deposited on the back layer side are easily washed away.

[0009] By the action described above, the adhesion of crystals on the filter cloth is effectively suppressed.

The ratio of the warp density of the first warp to the warp density of the second warp is practically in the range of 4: 1 to 2: 1, and 3: 1 is most preferable for dewatering and filtering solids in groundwater.

As the warp yarns on the surface layer side and the back layer side, those obtained by twisting a plurality of filaments having relatively fine fineness are preferable for dehydration filtration of fine particles. For example, two or more yarns of 250 denier in Tetron and two or more yarns of 170 denier in polypropylene are twisted, and the fine particle filtration performance of a filter cloth using a multifilament yarn having a total fineness of 300 to 1000 denier is good. Met. In general, the higher the fineness, the lower the surface smoothness on the surface layer side. Therefore, a warp fineness of 1000 denier or more is not preferable.

The wefts on the surface layer and the back layer are preferably monofilaments in order to maintain the strength of the filter cloth.
Can be used. These warps and wefts are formed of synthetic fibers such as polyester, nylon or polypropylene. However, it is not preferable to reduce the weft diameter to 0.15 mm or less, because the smaller the weft straightness, the smaller the voids on the back layer side, resulting in an increase in the absolute amount of precipitated crystals and a decrease in drainage efficiency. In addition, as the diameter of the weft increases, the rigidity of the filter cloth increases and the handleability of the filter cloth, such as mounting on a dehydrator, deteriorates. Therefore, it is not preferable to increase the diameter of the weft to 0.4 mm or more.

By using the above-described yarn for the warp and the weft, the surface layer side of the filter cloth is mainly covered with multifilaments and the back layer side is mainly covered with monofilaments.

[0014] The air permeability of the filter cloth is determined in consideration of the filtering ability and the processing ability of the fine particles.
The range of 0 cc / min. / Cm ² is good.

In order to improve the ability of the filter cloth to collect fine particles and to remove the cake, the surface layer may be calendered. By this calendering, the weave gap on the surface layer side becomes finer and smoothness is obtained. The above-mentioned synthetic fibers such as polyester, nylon and polypropylene have a suitable degree of heat softening and are therefore particularly suitable for calendering.

The filter cloth according to the present invention can be used in various dehydration filtration apparatuses, such as a filter press for dewatering and filtering of groundwater intake water and a long-time dehydration filtration, and can be used in general factory drainage filtration filter presses and horizontal belts. It is also applicable to belt-type filter cloths such as. In addition, when used for filter press for dewatering and filtration of groundwater intake and filter press for long-time dewatering and filtration,
The effects of the present invention appear more remarkably.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

FIG. 1A is a schematic plan view of a woven structure of a filter cloth 10 according to an embodiment of the present invention,
Vertically arranged Roman numerals 1 (circled numerals) to 12 (circled numerals) correspond to warp numbers 1 to 12 of the longitudinal section of the filter cloth 10 in FIG. 1B, and these 12 warp yarns are woven. Makes up the organization's repeat units. Also, the side-by-side Chinese numerals 1-6, 1-6 are the weft number 1- of FIG. 1 (B).
Six, one to six, and these six wefts constitute a repeat unit of the weave structure.

The warps 20 and 21 and the wefts 30 and 31
It is composed of synthetic fibers such as polyester, nylon or polypropylene.

As apparent from FIG. 1, the filter cloth 10 of the present invention has a double weave, a twill weave structure with a surface layer side of 2/1, and is woven into a surface layer side weft 30 (1, 3, 5). The density of the first warp 20 is three times higher than the density of the second warp 21 that connects the surface layer side and the back layer side wefts to each other. That is, the surface side weft 30 (one,
The first warp 20 woven only in (3, 5) is (1
To 3), (5 to 7), and (9 to 11), and the second warp 21 that connects the surface layer side and the back layer side wefts to each other is (4, 8, 12).

The weave pattern of the filter cloth 10 is as follows:
With 12 warps and 6 wefts as the repeat unit of the weave,
These are woven patterns that are repeated in the longitudinal direction. When observing the warp yarns (1 to 12) in the repeat unit, the first warp yarns 20 (1 to 3), (5 to 7), (9
11), three of them are always lurking below the surface side weft 30, but the other six first warps 20 are the second warp 2
Along with any one of 1 (4, 8, 12), it covers the surface side weft 30. For example, for the first weft, the first
A total of seven warps (3,7,11), (1,5,9) and a second warp (8) are covered on one weft, and three first warps (2,6) , 10) are under the weft.
FIG. 1 (A) schematically shows the above-described weaving pattern. A warp portion covered on the surface side weft is represented by a black pit, and a warp portion buried under the surface side weft is represented by a white pit. ing.

When comparing the surface layer side and the back layer side in FIG. 1B, there is a difference in density between the first warp yarn 20 and the second warp yarn 21 as described above, and the woven structure is completely different. I understand. Due to such difference in density and difference in woven structure,
The front and back of the filter cloth 10 have a so-called asymmetric structure, which prevents the filter cloth 10 from being clogged, traps fine particles, and improves cake peelability.

In order to increase the density gradient on the surface layer side, that is, to increase the density gradient from the surface layer side to the back layer side, the calendering is effective while keeping the number of warp yarns on the surface layer side and the back layer side as they are. This calendering also improves the smoothness of the surface layer side, and thus also serves as a measure for improving the peelability of the cake.
The calendering conditions are as follows: the roll temperature is 140 ° C. to 230 ° C., and the roll load is 50 kgf to 250 kgf per 1 cm in the width direction of the filter cloth, depending on the type of the warp and the weft.
In the range of. Further, the speed of the roll is desirably in the range of 1.4 m / min to 3.0 m / min. Whether or not to perform calendering may be selected according to the use of the filter cloth, and calendering is not necessarily required in applications where the density gradient may be relatively small.

According to the present invention, a filter cloth having a necessary and sufficient strength can be manufactured according to the application, so that the present invention can be applied to a belt type filter cloth requiring a high strength such as a horizontal belt. In addition, the present invention can be suitably applied to applications for leaf filters, centrifuges, and the like by utilizing its characteristics.

[0025]

As shown in FIG. 2, the filter cloth experimentally woven according to the present invention has the same weft double weave as that of FIG. The density of the side warp (first warp) 20 is 72 / 2.54 cm, and the density of the back layer side warp (second warp) 31 is 24 / 2.54 cm.
cm. Therefore, the ratio of the warp densities on the surface layer side and the back layer side is 3:
It is one. Note that the twill structure is 3/1 in addition to the 2/1 twill structure.
One twill texture is also possible.

The surface layer side warp 20 and the back layer side warp 21
Both are 250D (denier) twisted yarns in which two polyester multifilament yarns are twisted.

The surface layer side weft 30 and the back layer side weft 31
Both are polyester monofilament yarns having a diameter of 0.3 mm, and both have a density of 42 yarns / 2.54 cm.

After weaving the above filter cloth 10, the surface layer was calendered. Calendar processing,
A roll heated to 200 ° C. was passed in the width direction (weft direction) on the surface layer side of the filter cloth 10 and a load of 250 kgf / cm per 1 cm width of the filter cloth was applied.

The resulting product has a thickness of 0.62
mm, and the air permeability was 180 cc / min. / cm ² (JIS / Fragile method). The surface side was glossy and extremely smooth, and the weave of the weave was finer than before calendering.

The filter cloth woven and processed as described above was used in a filter press for dewatering and filtration without chemical injection in a groundwater intake, and the dewatering filtration performance was tested.

As a result of the test, the amount of precipitated crystals on the back layer side of the filter cloth is greatly reduced as compared with the filter cloth woven with the conventional multifilament yarn, and the filter cloth is not clogged. Did not. Further, the flow path of the filtrate was sufficiently secured by the amount of the voids on the back layer side increased by the low density warp on the back layer side, and the filtration speed was improved.

On the other hand, the high-density warp on the surface layer improved the recovery rate of the filtered fine particles, shortened the cycle time required for filtration, and obtained a large filtration efficiency. Also, the peelability of the cake was good, and it was found that this good state could be maintained for a long time.

The same effect as that of polyester can be obtained by using nylon or polypropylene as the material of the warp and weft of the filter cloth.

[0034]

According to the present invention, the deposited crystals can be prevented from adhering and accumulating on the back layer side of the filter cloth, so that clogging of the filter cloth can be eliminated.

In addition, a filter cloth which can collect fine particles and has good cake releasability can be obtained.

Furthermore, since the cycle time required for filtration can be shortened, there is an effect that the filtration efficiency can be improved.

Further, the initial leakage was reduced.

[Brief description of the drawings]

FIG. 1A is a schematic plan view of a woven structure of a filter cloth according to an embodiment of the present invention, and FIG. 1B is a longitudinal sectional view of the filter cloth.

FIG. 2 is a diagram showing specifications of a filter cloth.

[Explanation of symbols]

 20,21 warp yarn 30,31 weft yarn

Claims (8)

[Claims] 1. A filter cloth having double wefts on the front and back sides, wherein a high-density first warp woven into the surface side weft of the filter cloth and the wefts on the surface side and the back side of the filter cloth are mutually connected. A filter cloth comprising: a low-density second warp to be tied. 2. The density ratio between the first warp and the second warp is defined as
4. The filter cloth according to claim 1, wherein the ratio is in the range of 4: 1 to 2: 1. 3. The warp yarns on the surface layer side and the back layer side are multifilament yarns of two or more twisted yarns having a total fineness of 300 to 1000 denier, and the weft yarns on the surface layer side and the back layer side are straightened. The filter cloth according to claim 1, wherein the warp is a monofilament yarn having a warp of 0.15 mm to 0.4 mm. 4. The filter cloth according to claim 3, wherein the air permeability is 50 to 400 cc / min. / Cm ² . 5. The filter cloth according to claim 3, wherein the warp and the weft are made of polyester, nylon or polypropylene. 6. The filter cloth according to claim 3, wherein the surface layer is calendered. 7. A filter press for dewatering and filtering underground water using the filter cloth according to any one of claims 1 to 6. 8. A filter press for long-time dehydration filtration using the filter cloth according to claim 1.