JP2008279339A - Solid/liquid separation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid/liquid separation apparatus which is high in filtering rate, is free from clogging and is high in the recovery ratio of a solid matter. <P>SOLUTION: The solid/liquid separation apparatus uses filter cloth, the filter cloth being a resin with the surface subjected to a hydrophilicizing treatment. The solid/liquid separation apparatus increases the filtering rate by a capillary action of the surface of the filter cloth, by reforming the surface of the resin filter cloth by hydrophilicizing treatment. The formation of a thin water film on the filtering surface prevents attachment of protein in sludge on the filter cloth surface, resulting in the realization of the solid/liquid separation apparatus which is high in the filtering rate, is free from the clogging and is high in the recovery ratio of the solid matter. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a filtration device, a sludge concentration device, and a sludge dewatering device for performing a solid-liquid separation operation in various treatments such as clean water, industrial water, sewage, human waste, and industrial wastewater.

  Conventionally, as solid-liquid separation devices used in various water treatments and sludge treatments, there are various types called filtration devices, sludge concentration devices, sludge dewatering devices, and the like.

  A filtration device removes fine particles in water. For example, the rotary drum type continuous filter described in JP-A-8-155229 has a two-layer structure with a fiber bundle having crimps with the base layer in order to capture smaller particles on the filtration surface. The filter cloth is used.

  A sludge concentrator is a device that separates filtrate from sewage sludge, purified water sludge, or industrial wastewater sludge to enhance the concentration effect. In general, a flocculant is added for the purpose of increasing the aggregating effect. For example, in the belt type concentrator described in JP-A-2006-26455, a flocculant is added to sludge, and then the filtrate is separated by a filter medium. In this apparatus, a metal filter medium with less clogging and good peelability is used as the filter medium.

  The sludge dewatering device is a device in which a flocculant is added to the sludge concentrated by the above sludge concentrator, and the sludge is dehydrated by applying an external pressure such as centrifugal force or press. For example, in the apparatus described in JP-A-8-001390, a screw press having a screen as a filtration surface is used in the outer cylinder, and the clogged screen is regenerated by washing.

  As described above, the solid-liquid separation device is required to reduce the opening of the filtration surface to ensure the capture of the solid content, to be free of clogging, and to have a high filtration rate. It is not easy to do.

In filter devices, sludge concentrators, and sludge dewaterers, resin filter cloth is often used to perform solid-liquid separation operations. However, the resin filter cloth is a hydrophobic material and has water repellency as it is, and has a low water filtration rate. In addition, the resin easily binds to the protein in the sludge and causes clogging. In particular, if the opening of the filtration surface is made small in order to ensure the capture of the solid content, the frequency of clogging increases. In this way, it is not easy to satisfy the requirements of no clogging, high filtration rate and high solid content recovery at the same time.
JP-A-8-155229 JP 2006-26455 A JP-A-8-001390

  The present invention has been made in view of the problems of the solid-liquid separation apparatus using the resin filter cloth as described above, and the object of the present invention is high filtration speed, no clogging, and solid content. An object of the present invention is to provide a solid-liquid separator having a high recovery rate.

The solid-liquid separation device of the present invention comprises:
An apparatus for separating solids from a fluid using a filter cloth,
The filter cloth is a resin whose surface is subjected to a hydrophilic treatment.

  In the solid-liquid separation device of the present invention, the filtration rate is improved by the capillary action of the surface of the filter cloth by modifying the surface of the resin filter cloth with a hydrophilic treatment. Furthermore, since a thin water film is formed on the surface of the filtration surface, it is possible to prevent proteins in the sludge from adhering to the surface of the filter cloth. As a result, a solid-liquid separation device with a high filtration rate, no clogging, and a high solid content recovery rate is realized.

  The solid-liquid separation device of the present invention is particularly suitable when the fluid to be treated is a fluid containing organic sludge.

  Preferably, the filter cloth has hydrophilicity with a contact angle with water of 40 ° or less.

  Preferably, the filter cloth is a mesh cloth in which a resin monofilament is woven in a plain weave, a twill weave, a twill weave, or a soot weave.

Here, the hydrophilization treatment will be further described.
By applying a hydrophilic treatment to the surface of the resin filter cloth, the capillary phenomenon in which the liquid permeates into the solid micropores can be advantageously used. As shown in FIG. 5, this phenomenon is a phenomenon in which, if a hydrophilic solid, the liquid rises in the capillary tube due to surface tension while against gravity. The liquid column height h of the capillary at this time is obtained by the following formula:

a: capillary radius, σ _L : surface tension of liquid, θ: contact angle between liquid and capillary inner wall, ρ: specific gravity of liquid, g: acceleration of gravity.

  The resin is originally hydrophobic, and it is difficult to filter the liquid as shown in the right figure of FIG. 5, but the filter cloth that has been subjected to the hydrophilic treatment has an action of sucking out water by capillary action as shown in the left figure. Filtration rate increases. In addition, according to Formula (1), it turns out that a filtration rate increases, so that the contact angle of a liquid and solid is small and hydrophilicity is high, and the opening of a filter medium is small. The smaller the contact angle with water is, the better, and it is better to be 40 ° or less. Thus, since a filtration rate increases by performing a hydrophilic treatment to a resinous mesh cloth, a to-be-processed substance can be processed using a small filtration area.

  In addition, since the resin is made of a polymer, it is difficult to form a complete crystal, and a structure in which a crystal part and an amorphous part are mixed is easily obtained. For this reason, it has the fault that the surface is easy to be damaged, and sludge will enter there if it is damaged. As shown in FIG. 6, the sludge adhering to the surface soaks into the polymer of the resin, and the sludge is integrated with the resin on the surface of the resin. The opening is crushed and clogging is likely to occur.

  As shown in FIG. 7, the sewage sludge solids contain a large amount of high molecular weight polysaccharides and proteins, and the polymer structure has dissociative hydrophilic properties such as amino groups, carboxyl groups, sulfonic acid groups, and hydroxyl groups. I have a lot of groups. Since these hydrophilic groups form a stable hydrophilic layer, the solid matter of sewage sludge is surrounded by a water film.

  Here, by applying a hydrophilic treatment to the filter cloth, a thin water film is formed on the resin fiber surface of the filter cloth as shown in FIG. Since the sludge itself is also surrounded by a thin water film, it does not come into direct contact with the resin fiber surface, and the sludge hardly adheres to the resin function. Thus, the presence of a water film between the surface of the filter cloth and the sludge prevents the sludge components from binding to the surface of the filter cloth, and the surface is always kept in a smooth state. There is no clogging.

  According to the solid-liquid separation device of the present invention, the filtration rate is improved by the hydrophilization of the surface of the filter cloth and the sludge adhesion preventing effect, so that the filtration rate is high, there is no clogging, and the solids recovery rate is high. A solid-liquid separator is realized.

  Next, some examples of the solid-liquid separation apparatus based on this invention are demonstrated, referring drawings.

  FIG. 1 is a schematic side view showing an example of a rotary drum type continuous filter according to the present invention. In the figure, 10 is a filter cloth, 11 is a drum, 12 is raw water, 13 is filtered water, 14 is concentrated water, 16 is a backwash spray, and 17 is a surface wash spray. In this apparatus, the filter cloth 10 is attached on the circumference of the rotating drum 11, and the raw water 12 guided to the inside of the drum 11 is filtered to the outside. The filter cloth 10 used here is a resin mesh cloth that has been subjected to a hydrophilic treatment.

  There exists a rotary disk type continuous filter as another thing. In this device, filter cloths are attached to both sides of a relatively thin drum (referred to as a disk), and one or more of these disks are installed in parallel on the central axis of the disk. The introduced raw water is filtered outward. The filter cloth used here can also use a resin mesh cloth that has been subjected to a hydrophilic treatment.

  FIG. 2 is a schematic side view showing an example of a belt-type sludge concentrating device based on the present invention. In this apparatus, after adding a flocculant to the sludge, gravity filtration is performed while the sludge 23 is conveyed by a mesh-like endless belt 20 made of resin or metal. The concentrated sludge is discharged to the discharge unit 24, and the filtered filtrate is collected in the water collecting pan 21 and discharged outside the system. The filter cloth used here is a resin mesh cloth that has been subjected to a hydrophilic treatment.

  FIG. 3 is a side view of the screw press sludge dewatering device according to the present invention. In this apparatus, the outer cylinder 30 is provided with a filtration surface. The sludge 31 is conveyed by the screw 33, but is subjected to internal pressure by the outlet-side presser 36. Further, the screw shaft 34 is tapered and the internal volume gradually decreases. Only is filtered and discharged out of the system. The dewatered sludge 38 is discharged from the dewatered cake outlet 35.

  Conventionally, a metal punching metal, a screen, or the like has been used as the filter medium. However, according to the solid-liquid separation apparatus according to the present invention, a resin mesh cloth in which the filter medium is subjected to a hydrophilic treatment is formed. .

  Next, various test results regarding the performance of the resin mesh cloth subjected to the hydrophilic treatment will be described.

  As a method for hydrophilizing the resin surface, (a) a method by melt solidification for improving the resin surface by removing the substrate after the substrate is brought into contact with the resin surface and heated to melt the resin portion in contact with the substrate; (B) Surface modification method by ultraviolet irradiation, laser irradiation, plasma treatment; (c) Method of modifying resin surface by grafting reaction to monomer; (d) Method of forming thin film containing inorganic particles on resin surface; Etc.

  In the method of melting and solidifying in (a), the use of a material having a high surface energy (for example, metal) as the substrate increases the density of functional groups on the resin surface, that is, the degree of crystallinity on the surface, and the hydrophilicity becomes higher. This is desirable because it increases. Examples of the hydrophilization treatment (b) include a hydrophilization example in which a hydroxyl group, which is a hydrophilic group, is formed by irradiating a polypropylene surface with ultraviolet rays using a low-pressure mercury lamp. Examples of hydrophilization by graft polymerization (c) include graft polymerization by acting acrylamide as a monomer on the surface of low density polyethylene or oriented polypropylene, or N-vinylpyrrolidone or acrylic acid as a monomer on the surface of oriented polypropylene. It is known that the hydrophilicity of the resin surface can be remarkably improved by graft polymerization. As a method of forming the hydrophilic thin film of (d), a method of forming a thin film containing titanium oxide and silica particles (Japanese Patent No. 2756474), an acrylic monomer, a polymerizable silane coupling agent, and a colloidal And a method of forming a thin film containing silica on the surface of the resin by emulsion polymerization (JP-A-07-233270).

  In a filtration test using a polyester mesh cloth as a comparative specimen and the hydrophilic mesh cloth specimen of the present invention in which the polyester surface is hydrophilized by laser treatment (excimer laser, oscillation wavelength 248 nm) The effect was confirmed.

  First, a filtration test was conducted using a polyester mesh cloth that had been subjected to a hydrophilic treatment by this method and a polyester mesh cloth that had not been subjected to a hydrophilic treatment for comparison. The filter used is a continuous drum screen of φ500.

  Table 1 shows the results of this test. The mesh cloth subjected to the hydrophilization treatment has a filtration speed of 2.85 times (60 m / H ÷ 21 m / H) compared to the mesh cloth for comparison, and the filtration speed is greatly increased. I understand.

  Further, the filtration speed after one year of continuous operation has been reduced to 71% (15 m / H ÷ 21 m / H) in the comparative mesh cloth. This is because sludge adheres to the polyester fiber and the opening is gradually closed. On the other hand, the mesh cloth subjected to the hydrophilization treatment decreased by 87% (52 m / H ÷ 60 m / H), but more than 5.8 times the comparison mesh cloth (87 m / H ÷ 15 m / h). H) has a filtration rate, and the effect of the hydrophilization treatment is remarkable.

Next, the result of the sludge concentration test using the belt-type sludge concentrator shown in FIG. 2 will be described.
As a filter cloth, the effect of the hydrophilic treatment was confirmed in a sludge concentration test using a polypropylene filter cloth as a comparative specimen and the hydrophilic mesh cloth specimen of the present invention in which the polypropylene surface was hydrophilized with ultraviolet rays. .

Table 2 shows the results of this test. The amount of sludge treatment per 1 m ² of filter cloth when using a mesh cloth subjected to hydrophilic treatment is 1.23 times that when a mesh cloth for comparison is used (24.5 m ³ / m ² · H ÷ 20 m ³ / m ² · H), and the throughput is improved. Also, the solids recovery rate has improved by 2 points.

  Next, the results of the sludge dehydration test will be described. The test methods are the sewage test method, Japan Sewerage Society 1997 edition, Chapter 4 general sludge test, Section 14 dewatering test, 2. According to pressure filtration test.

  FIG. 4 shows a schematic configuration of the dehydration test apparatus used for this test. Effect of hydrophilic treatment in a sludge concentration test using a polyester filter cloth as a comparative specimen and the hydrophilic filter cloth specimen of the present invention in which a thin film containing colloidal silica is formed on the polyester surface by emulsion polymerization. It was confirmed.

  Table 3 shows the results of this test. The water content of the dehydrated cake when using a mesh cloth that has been subjected to a hydrophilic treatment is 78.5%, and the water content is about 2.5 points lower than when a comparative mesh cloth is used. Has improved.

As described above, according to the solid-liquid separator based on the present invention, the following useful effects are brought about by using the resin filter cloth having the hydrophilic layer formed on the surface thereof.
(A) Because of the presence of a hydrophilic layer coated on the surface of the resin filter cloth, the filtration speed increases due to the capillary action that the hydrophilic fiber absorbs water, enabling processing with a small filtration area. Thus, the device becomes compact.
(B) Due to the presence of the hydrophilic layer coated on the surface of the resin filter cloth, a thin water film is formed on the surface of the filter cloth, preventing the protein in the sludge from binding to the filter cloth fibers, and clogging the filter cloth. Does not occur. For this reason, the washing | cleaning property of a filter cloth is good and can ensure the filtration rate. Also, the replacement interval time due to clogging of the filter cloth becomes longer.

The side view which shows an example of the rotating drum type continuous filter based on this invention. The side view which shows an example of the belt type sludge concentration apparatus based on this invention. The side view which shows an example of the screw press type sludge dehydration apparatus based on this invention. The figure which shows schematic structure of a dehydration test apparatus. The figure explaining a capillary phenomenon. The figure explaining the adhesion situation of the sludge on the resin surface. The figure explaining the microbial structure model in sludge. The figure explaining the adhesion situation of the sludge of the resin fiber surface made hydrophilic.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Filter cloth, 11 ... (Rotation) drum, 12 ... Raw water, 13 ... Filtrated water, 14 ... Concentrated water, 16 ... Backwash spray, 17 ... Surface wash Spray, 20 ... Endless belt, 21 ... Catchment pan, 23 ... Sludge, 24 ... Discharge part, 30 ... Outer cylinder, 31 ... Sludge, 33 ... Screw, 34 ... Screw shaft, 35 ... Dehydrated cake outlet, 36 ... Presser, 38 ... (Dehydrated) sludge.

Claims (4)

An apparatus for separating solids from a fluid using a filter cloth,
A solid-liquid separation device, wherein the filter cloth is a resin whose surface is subjected to a hydrophilic treatment.   The solid-liquid separation device according to claim 1, wherein the fluid to be treated is a fluid containing organic sludge.   The solid-liquid separator according to claim 1, wherein the filter cloth has hydrophilicity with a contact angle with water of 40 ° or less.   The solid-liquid separator according to claim 1, wherein the filter cloth is a mesh cloth in which a resin monofilament is woven in a plain weave, a twill weave, a twill weave, or a sussus weave.

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