JPH0557009B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a filter cloth for solid-liquid separation, and more specifically to a filter used when dehydration or filtration is performed while rotating an endless filter cloth carrying a solid-liquid. Regarding cloth.

[Prior art]

Conventionally, an endless filter cloth carrying a solid liquid is run through a pressing section consisting of a transfer drum and a press roll.
A belt press type dehydrator is used in which the liquid components are squeezed out in the above-mentioned squeezing section, and the so-called solid components remaining on the filter cloth are transferred to a transfer drum, where they are scraped off with a scraper and recovered. Filters liquid components using gravity without squeezing solid-liquid,
So-called solid-liquid separators, such as filters that collect remaining solid components using water nozzles or scrapers, are used in various fields. These solid-liquid separation devices, especially filters, are equipped with a pressure reducing section near the solid-liquid supply section and facing the back side of the filter cloth to suck out liquid components and improve separation efficiency. There is also. The filter cloth of the present invention is used in such a solid-liquid separation device.

Conventionally, the filter cloth used in the solid-liquid separator described above has a thickness of 30 to 30 mm on the surface of the textile base material.
Thick short fibers of 100 microns are flocked with adhesive to form raised naps that are slanted in one direction, or those that are raised on the surface of a textile base material to form thick naps of several tens of microns in thickness. something is known. These conventional filter cloths have a textile base material that provides the necessary strength as a filter cloth, and a raised surface that prevents solid components from entering the filter cloth. In other words, the piloerection forms a filter layer. however,
All such conventional filter cloths have the drawbacks of low solid-liquid separation performance and poor transferability.

That is, in the above-mentioned conventional filter cloth, the raised fibers are formed by flocking with an adhesive, and in order to prevent the holes in the base material from being buried by the adhesive, the density of the raised fibers cannot be made very high. The thickness of the piloerection
Since it is very thick, measuring 30 to 100μ, the gaps, or eyes, formed between the pili are quite large, and fine solid components can easily pass through the gaps. Therefore, when using this conventional filter cloth, it is essential to coarsen the solid component by using a flocculant, which not only increases running costs, but also
Depending on the type of flocculant, its toxicity may also be an issue.
The use of flocculants also increases the amount of solid components.

In addition, the conventional filter cloth mentioned above has a nap thickness of 30~
Because it is very thick (100μ), it is rigid and does not easily lie on the surface of the base material. Therefore, the gaps formed between the raised fluffs are very deep, and if solid components get into those gaps, they will have a hard time coming out, and the filter cloth will become clogged. This tendency is very remarkable, partly because the piloere is rigid and easily pierced by solid components. Furthermore, the fact that the nape is difficult to lie down also means that the filter layer formed by the nape is bulky. Therefore, airtightness is poor when vacuum suction is performed. Further, since the gaps between the naps are deep, the surface has large irregularities, and the thickness of the solid component on the filter cloth becomes uneven, so that pressure at the pressing section is not uniformly applied.

For the reasons mentioned above, conventional filter cloths have very low solid-liquid separation performance. If the solid-liquid separation performance is low, not only will the liquid component contain a large amount of solid components, but the recovered solid components will contain a large amount of water, requiring a large amount of energy for post-processing such as incineration. Become.

Furthermore, in conventional filter cloths, as mentioned above, solid components that have gotten into the nape do not easily come out.
Therefore, when the filter cloth is separated from the transfer drum, the solid components are returned to the filter cloth side by the raised fluff, resulting in poor transferability.

On the other hand, in the conventional filter cloth, although not as large as in the conventional filter cloth 1, the gaps between the naps are still quite large and deep. Therefore, this conventional filter cloth 2 also has low solid-liquid separation performance and poor transferability.

On the other hand, the inventors of this invention previously filed a patent application in 1983.
In the -226384 application, a new type of filter cloth was proposed. This filter cloth has a filter layer on the surface of the base material with a thickness of
It is made of raised microfibers with a diameter of 0.1 to 10μ.

Since the above-mentioned filter cloth has a filter layer formed of napped microfibers having a thickness of 0.1 to 10 μm, the gaps formed between the napped fibers are very small, and even fine solid components can be blocked. In addition, the raised fibers of ultra-fine fibers are very flexible and lie easily, so the gaps between the raised fibers are shallow, and the solid component gets stuck in the gap while deforming and becomes difficult to get out.
Less likely to cause clogging. The fact that the nape is easy to lie down also means that the filter layer formed thereby does not become bulky, and the density of the nape is increased, so that airtightness can be maintained highly when vacuum suction is performed. For these reasons, the filter cloth has very high solid-liquid separation efficiency.

In addition, the transfer performance is also high because the gaps between the raised fluffs are small, making it difficult for solid components to enter the gaps, and because the raised fluffs are flexible and are prevented from digging into the solid components.

As described above, the filter cloth proposed in the above-mentioned application is an excellent product that does not have the drawbacks of the conventional filter cloths mentioned above. Another problem is that the solid-liquid separation performance is unstable due to the piloe being pushed into the eye, making it difficult to stand up again, and the piloere becoming entangled.

Therefore, in order to improve this problem, the inventors of the present invention further proposed in Japanese Patent Application No. 58-137639 that the naps forming the filter layer of the filter cloth have directionality, and that A filter cloth with a directional index of 12-10 was proposed.

In the filter cloth proposed in this application, the naps forming the filter layer have directionality, and the directional index is
1.2 to 10, it is possible to prevent the raised fluff from being pushed into the holes of the substrate and making it difficult to stand up again during use, or from getting entangled, and to maintain stable solid-liquid separation efficiency. However, in the case of separation of solid components with small particle sizes, there is a problem that the transferability is insufficient.

[Purpose of the invention]

The present invention was made in view of the above problems, and its purpose is to provide a filter cloth for solid-liquid separation that has a high transfer rate and solid-liquid separation performance, and in which the deterioration thereof is extremely small. The purpose is to improve rejection rate, water permeability, and transfer rate.

[Structure of the invention]

A filter cloth for solid-liquid separation of the present invention that achieves the above object has a substrate made of synthetic fibers, on at least one side of which
The filter cloth has a raised portion having a directionality index of 1.2 to 10 in the length direction and a specific surface area of 3×10 ³ cm ² g/or more,
Moreover, it is characterized in that a water-repellent substance is applied only to the raised part.

[Embodiments of the invention]

To explain one embodiment of the filter cloth of the present invention, in FIG. 1, the filter cloth 1 is sewn together along the dotted line,
Processed endlessly. Perforated belts 2 and 3 are sewn to both ends of the filter cloth 1 to stretch the filter cloth 1 and run it without meandering. It is preferable that the belts 2 and 3 have some elasticity so that the belts 2 and 3 can be stretched without causing wrinkles in the filter cloth 1. Therefore, belts 2 and 3
It is preferable that the core material is a synthetic fiber fabric, and the core material is a composite of the core material and rubber.

The above-mentioned filter cloth is made by laying the raised synthetic fibers obtained by raising the base material on the surface of a base material made of synthetic fiber woven fabric, knitted fabric, non-woven fabric, etc., and aligning them in almost one direction.
A filter layer is formed by the raised fluff, and its direction index is 1.2 to 10, and the specific surface area of the raised fluff is 3×10 ³ cm ² /g.
In addition to the above, a water-repellent substance is further applied to the raised part.

The synthetic fibers constituting the base material are preferably those with wear resistance and chemical resistance, such as polyamide fibers,
polyester fiber, polyvinyl alcohol fiber,
Polyfluoroethylene fibers, polypropylene fibers, polyacrylonitrile fibers, etc. can be used. The fibers are preferably non-crimped;
Those with circular or modified cross sections can be used as stables or filaments.
In addition, as the fiber, a so-called multifilamentary composite fiber having different polymeric substances as sea-island components, or a splittable composite fiber obtained by laminating and spinning different polymeric substances and being splittable at the laminated part are used. It is also possible.
Furthermore, depending on the type of solid-liquid, these fibers subjected to hydrophilic or hydrophobic processing may also be used.

As the base material, woven fabrics, knitted fabrics, nonwoven fabrics, etc. can be used. As a textile base material, it is preferable that the warp is a synthetic fiber filament processed yarn, the weft is a yarn made of non-crimped fibers, and the weft is raised. Moreover, it is also possible to use a spun yarn or a bulky textured yarn having loops or protrusions as the weft. The woven structure is preferably a satin weave so that the warp and weft have a desired density and a desired floating structure.

Further, as the knitted fabric base material, circular knitting such as rib knitting, double-sided knitting, etc., warp knitting such as half knitting, Queen's cord knitting, etc. can be used. Among these, half-knit, tricot fabric is preferred because it is relatively easy to form naps.

Furthermore, in the case of using a nonwoven fabric base material, the stable or filament of the synthetic fiber is mixed with fibers or fine particles having a lower melting point than that, and the paper is made into paper, and the low melting point fiber or fine particles are partially melted. After the synthetic fibers are integrated using a filter, the surface may be buffed to raise the synthetic fibers to form a filter layer, or the stable or filament may be formed using an air stream or a water stream. The filament may be accumulated and punched to form a felt, and the surface of the filament may be raised to form a filter layer.

Methods for forming naps on the substrate include clothing, sand paper, sand cloth, sand net, grindstone, steel brush, polishing brush, sand roll, garnet, sand honing, and the like. Among these, it is most preferable to use clothing.

Now, in this invention, it is necessary that the above-mentioned nap has directionality and the directionality index is 1.2 to 10. The preferred direction index is 1.3~
It is 5. Here, the directional index is measured as follows.

The length in the longitudinal direction of the filter cloth to be measured, that is, the warp direction if the base material is a woven fabric, or the wale direction in the case of a knitted fabric.
Make 4 shredded pieces 25cm wide and 3cm wide. A mark is attached to the leading edge of each shredded piece when it is run as a filter cloth.

Next, in order to remove distortion of the filter layer, each of the shredded pieces was placed on a 50-mesh wire mesh with the filter layer facing up, and submerged in water. After 24 hours, the filter cloth was pulled up with the wire mesh, air-dried, and left in an atmosphere at a temperature of 25±2°C and a relative humidity of 65±5% for 24 hours to maintain constant moisture absorption.

Next, prepare a glass plate with a length of 65 cm and a width of 30 cm, and raise one longitudinal end of the glass plate by 2.5 cm and tilt it. Furthermore, place one of the shredded pieces prepared above on the glass plate so that its longitudinal direction is the longitudinal direction of the glass plate, and the mark end is located above the slope of the glass plate. Then cover the area up to 7cm from the top with a polyester film 7cm long, 3cm wide, and 75μ thick, and then cover it with a 35cm long polyester film.
Place a piece of cellophane tape with a width of 2.4 cm so that both ends protrude 5 cm from the top and bottom ends of the filter cloth and touch the surface of the glass plate, with the adhesive side facing the filter cloth.

Next, the outer diameter is 5cm, the length is 15cm, and the weight is 2.3Kg.
A roll made of SUS steel with a smooth surface is rolled by gravity from the upper end of the cellophane tape to adhere the filter cloth and the cellophane tape. To reduce measurement errors, this rolling operation is performed twice. After adhesion, 5 cm of both ends of the cellophane tape are cut off to obtain an adhesive between the filter cloth and the cellophane tape.

Next, the adhesive body obtained above is subjected to a peel test between a filter cloth and cellophane tape. This test is carried out continuously using a tensile tester, with the upper chuck gripping the polyester film and the lower chuck gripping the filter cloth, at a tensile speed of 30 cm/min. Then, from the peeling start end,
The peeling force is measured as the average value from the starting point to 9 cm from the starting point. Hereinafter, the peeling force obtained by this measurement will be referred to as A.

Next, another cut piece is subjected to exactly the same test, but this time with the other end corresponding to the mark end being above the slope of the glass plate. By this measurement, the peeling force D
get.

Next, regarding the third shredded piece,
Exactly the same test is carried out, but now with a polyester film placed on the bottom side of the filter cloth. By this measurement, the peeling force B is obtained.

Next, the last test piece is subjected to the same test as above. However, in this case as well, the polyester film is placed on the lower end of the filter cloth. By this measurement, the peeling force C is obtained.

Next, from the above peeling forces A, B, C, and D, (B
+D)/(A+C) is performed. The result of this calculation is the directional index referred to in the present invention.

As is clear from the above definition, the directional index is the ratio of the peeling force in the direction in which the cellophane tape is easy to peel and in the direction in which it is difficult to peel, and this indicates the stability of the direction of napping. A directional index of 1.2 to 10 can be obtained by appropriately selecting the number of times and direction of napping, the type of napping machine, etc. In the above test, the cellophane tape used has an adhesive strength specified in JIS Z1522-1982 and has a width of 24 mm.

Further, in the present invention, it is necessary that the specific surface area of the nape is 3×10 ³ cm ² /g or more. Here, the specific surface area is the average circumference of the fiber cross section.
It is the product of the total fiber length per 1 g, and the average circumference is the average value of several samples.

In the present invention, it is important that the water-repellent substance is applied only to the raised portions of the filter cloth. By applying this water-repellent finish only to the napped portion and not to the base material, the water permeability of the filter cloth can be significantly improved.

As the water repellent, commonly used water repellents such as silicone-based, polyethylene wax, and fluorine-based resin can be used. Methods for applying a water repellent to the raised area include the foam treatment method (adding a raising agent and running the raised area over the foam to apply the water repellent), and the roller treatment method (applying a water repellent to a roller and applying the water repellent). It is preferable to apply a water repellent agent by contacting the napped part with the water repellent agent, and the amount of the applied water repellent agent is determined by the weight ratio to the entire filter cloth.
0.5-2.0% is preferred.

Figure 2 shows that the naps of synthetic fibers obtained by raising the base material are laid on the surface of a textile base material, aligned almost to one side, the naps form a filter layer, and only the naps are removed. This is a side view of the warp disassembly of a water-repellent filter cloth, where A is the base texture part and B is the raised part to which the water repellent agent is attached.

When the filter cloth of the present invention is used in a belt press type dehydrator, as shown in FIG.
The endless filter cloth 1 carrying the solid liquid 6 is run through a pressing section consisting of the above, and the liquid component in the solid liquid 6 is squeezed out by the pressing section, and the solid component remaining on the filter cloth 1 is transferred to the transfer drum 4. It is transferred, scraped off with a scraper 7, and collected. In this case, the filter cloth 1 is mounted so that the surface having the napped faces, that is, the front surface, faces the surface of the transfer drum, and the direction of the inclination of the napped faces in the opposite direction to the running direction of the filter cloth 1. In addition,
In FIG. 3, reference numeral 8 is a water spray nozzle for washing the filter cloth from the front and back surfaces after transfer, and 9 is a vacuum suction tank for liquid components.

As mentioned above, the filter does not have a transfer drum, and the solid components remaining on the filter cloth are collected with a scraper or a water spray nozzle.

The filter cloth of this invention can be manufactured by various methods. Next, a preferable example will be shown.

That is, as the weft, the island component is made of a polymeric material, preferably polyester, and the sea component is made of a polymeric material, preferably polystyrene,
So-called multifilament composite fibers containing 35 to 75% of island components, and twin or triple spun yarns of mixed spun fibers containing 80% or more of fibers that generate ultrafine fibers also use multifilament yarns and are used as warp yarns. False twisted yarn or composite latent crimped yarn is used, and the weft and warp yarns are woven with satin so that they have a desired density and a desired floating structure.

Next, the sea component of the weft yarn is removed with a suitable solvent, such as trichlorethylene, and after drying, the weft yarn is raised to form a nap, and only the raised part is treated to be water repellent.

Another method is to make a woven fabric using composite fibers obtained by pasting and spinning different polymeric substances, peeling off the pasting, and raising the nap to form a nap, and treating only the nap part to make it water repellent. . The polymer material to be laminated is preferably polyamide and polyester copolymer. As for the peeling method, it is preferable to rub vigorously in hot water and then air dry.

The filter cloth of this invention removes extremely fine solid components.
Moreover, since it can be separated stably,
It can be used for various purposes. For example, it concentrates and dewaters sludge, scum, flocs, wash water, concentrated sludge, etc. generated during wastewater treatment, such as suspended sludge and fixed sludge discharged from biofilm treatment equipment. It can be used in case. Specifically, for example, sludge generated from water and sewage treatment, excess sludge generated from septic tanks, sludge generated from human waste treatment, scum generated from pressurized flotation operations, and flocs and their agglomerations generated from industrial wastewater treatment. These include sediment flocs, backwash water from various filtration devices such as sand filters, and sludge concentrated in screen devices. Furthermore, it can be used to recover solid components in various manufacturing industries, such as paper pulp manufacturing, food manufacturing, sake brewing, and miso brewing. Furthermore, it can also be used to purify water in ponds and rivers.

Example: 223-core multifilament composite fiber with polyester as the island component and polystyrene as the sea component (fineness 2.5D)
The weft is a 20/2S spun yarn made by spinning, and the warp is a bundle of 48 polyester fibers with a thickness of 20μ, and the weft is 30 / cm and the warp is 40 / cm. Obtained textiles.

Next, the sea component of the weft was removed using trichlorethylene as a solvent to obtain a fabric consisting of a bundle of approximately 3,570 ultrafine fibers with a weft of approximately 0.02D in fineness.

Next, the above-mentioned fabric was put through a napping machine, and 20
Repeat the raising operation once, and then repeat the raising operation 10 times in the opposite direction to mainly raise the weft yarns to form raised naps.The raised part is treated with water repellent using foam treatment under the following conditions, and the number of raised naps is approximately 1000. A filter cloth of the present invention was obtained, which had a diameter of 2.0 mm and a directionality index of about 2.2.

(Water repellent processing conditions) ●Processing process Adding water repellent (applying to the raised areas using futsuo-based resin and foam treatment) - Drying (110℃) - Heat treatment (180℃,
1 minute) ●Processing agent composition Water repellent (futsu-based resin) 350g/l Water repellent durability improver 16g/l Foaming agent 20g/l Softener 50g/l Foam stabilizer 3g/l ●For processed fabrics Foam adhesion amount: 35g/m ^2.Next , the above filter cloth was cut into a width of 30cm and a length of 2.5m with the warp direction as the longitudinal direction, and the cut ends were sewn to form an endless filter cloth as shown in Figure 1. Obtained.

Next, the endless filter cloth was put through a belt press type dehydrator shown in Fig. 3, and the running speed of the filter cloth was adjusted.
A dehydration test was conducted at a rate of 4 m/min, the degree of vacuum in the vacuum suction tank was approximately 900 m water column, and the pressing force against the transfer drum was approximately 60 kg. The solid liquid used was tap water and clay with an average particle size of about 20 μ, adjusted to a clay concentration of about 300 mg/liter, and was mixed at about 40 liters/min without adding a flocculant. supplied. The particle size distribution of the clay in the above solid-liquid as measured by a Coulter counter was about 1 to 50 microns, which was found to be distributed over a fairly wide range.

As a result of the test, the rejection rate by the filter cloth was 72%, and the components recovered by scraping with the scraper were about 60% solids, which was actually about 2000 times more concentrated than the original concentration. Furthermore, the transfer rate to the transfer drum was approximately 90%, which was extremely high. Furthermore, the particle size distribution of clay in the solid component measured with a Coulter counter is approximately 1
~10μ, and most of those exceeding 10μ were removed. Further, even after approximately 500 hours of operation, the above performance did not change at all, and no abnormality was observed in the filter cloth.

〔Effect of the invention〕

As described above, the filter cloth for solid-liquid separation of the present invention has naps made of synthetic fibers on at least one side, and the naps have a directionality index of 1.2 to 1.2 in the length direction of the filter cloth.
It has 10 directions, and the specific surface area of the raised hair is 3×10 ³
cm ² /g or more, and is further characterized in that the raised portions are coated with a water-repellent substance. Moreover, its directional index is 1.2
~10, it is possible to prevent the nape from being pushed into the holes of the substrate and making it difficult to stand up again during use, or from getting entangled, resulting in stable solid-liquid separation efficiency. is obtained. Further, the filter cloth of the present invention has a specific surface area of raised fluff of 3×10 ³ cm ² /g or more,
In addition, since a water-repellent substance is applied to the raised portion, the transfer rate can be improved without reducing the amount of water permeation, and the recovery rate of solid components can be improved.
Furthermore, even a cake with a high moisture content can be transferred, and even a fine solid component with a small particle size can be efficiently transferred.
Furthermore, since even fine solid components can be blocked, it is not necessary to add a flocculant.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing an embodiment of the filter cloth of the present invention, FIG. 2 is a side view of the weft disintegration yarn of the filter cloth whose napped portion has been water-repellent, and FIG. 3 is the same as shown in FIG. 1 above. FIG. 2 is a schematic front view showing a belt press type dehydrator in operation using the filter cloth shown in FIG. 1...Filter cloth, 2, 3...Perforated belt, 4...Transfer drum, 5...Press roll, 6...Solid liquid, 7
...Scraper, 8...Water spray nozzle, 9...
...Decompression suction tank.

Claims (1)

[Claims] 1 On at least one side of the base material made of synthetic fibers,
The filter cloth has a raised portion having a directionality index of 1.2 to 10 in the length direction and a specific surface area of 3×10 ³ cm ² /g or more,
Moreover, the filter cloth for solid-liquid separation is characterized in that a water-repellent substance is coated only on the raised portion.