JPS59115720A - Filter cloth - Google Patents

Abstract

PURPOSE:To improve the transferability to a transfer drum of dehydrator, by covering the surface of a flow path backing material consisting of a fabric of synthetic fibers functioning as a filter cloth used for a belt-press type dehydrator, by a fluff of superfine fibers obtained by fluffing the backing material in the same direction to fom a filter layer. CONSTITUTION:An object 7 to be filtered is filtered and dehydrated by a belt- press type dehydrator consisting of an endless belt type filter cloth 1, a transfer drum 4, and a press roll 5. The object 7 is previously dehydrated under reduced pressure by an evacuating dehydration part 12, and is filtered under pressure by a pressing part consisting of the press roll 5 and the transfer drum 4, then the dehydrated solid matter sticks to the drum 4 and is stripped off by a scraper 9. In this case, when a sheet-shaped flow-path backing material is used, which is formed to have a fabric consisting of synthetic fibers as a core material and a filter layer of superfine fibers 0.1-10mu in size which is formed on its one side surface, an excellent transferability to a transfer drum is obtained, and the lowering of filtering capacity caused by the sticking of an object to be filtered to a filter cloth 1 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a filter cloth, and more particularly to a filter cloth suitable for use in a belt press type dehydrator.

A belt press type dehydrator runs an endless filter cloth carrying a material to be dehydrated through a pressing section consisting of a transfer drum and a press roll. The material remaining on the cloth is transferred to the surface of the transfer drum and scraped off with a scraper to be recovered. At this time, a reduced pressure dehydration section is provided near the supply section for the substance to be dehydrated, and the back side of the filter cloth is kept in a reduced pressure state to help the passage of liquid components.

Conventionally, the filter cloth used in the above-mentioned belt press type dehydrator is one in which thick short fibers with a thickness of 30 to 100 μm are flocked on the surface of a textile base material using an adhesive to form raised naps (hereinafter referred to as
There are known filter cloth fabrics (hereinafter referred to as "filter cloth I") and "shino" (hereinafter referred to as "urafuguchi") in which thick raised fluffs of several tens of microns in thickness are formed by raising the base material on the surface of a textile base material. These conventional filter cloths have a textile base material that provides the necessary strength as a filter cloth, and the naps on the surface of the base material that block solid components and remove water. In other words, the piloerection forms a filter layer. However, such conventional filter cloths have the drawbacks of low solid component rejection and dehydration rates, and poor transferability.

That is, as shown in Figure 1 (scanning electron micrograph of the surface, magnification: 30x) and Figure 2 (scanning electron micrograph of longitudinal section, magnification: 30x), the conventional filter cloth A is formed between the napped hairs. The gaps, that is, the openings, are quite large, and fine solid components can easily pass through the floes, resulting in a very low rejection rate.

The reason why the gaps between the naps are so large is that the naps are formed by flocking with adhesive in conventional filter cloths, and in order to prevent the eyes of the base fabric from being filled with adhesive, This is because the density of the piloerection cannot be made very high, and the thickness of the piloe is very thick, 30 to 100 μm, so the gap cannot be made very small. Therefore, when using this conventional filter cloth, it is essential to coarsen the solid component using a polymer flocculant, etc., which not only increases running costs but also has the toxicity of some flocculants. becomes a problem. Furthermore, the use of a flocculant not only increases the amount of solid components, but also requires constant checking of the flocculation conditions.

Further, the conventional filter cloth A has very thick naps of 30 to 100 μm in thickness, so it is rigid and difficult to lie on the surface of the cotton cloth. Therefore, the above-mentioned gaps are very deep, and the solid components get stuck in the gaps while being deformed and are difficult to get out, which causes the filter cloth to become clogged and the dehydration rate to decrease. This tendency is further aggravated when the rigid standing fluff pierces the solid component. Furthermore, the fact that the raised piloes are difficult to lie down also means that the wave layer formed by the piloes is bulky. Therefore, the airtightness in the vacuum dehydration section is poor, and in this respect, a high dehydration rate cannot be achieved. If the dehydration rate is low, the amount of water contained in the recovered material will increase, and a large amount of energy will be required in post-processing steps such as incineration. In addition, conventional filter cloths have large irregularities on the surface due to the deep gaps between the naps, and the thickness of the solid components on the filter cloth is uneven, resulting in poor airtightness in the vacuum dehydration section.
Pressure of solid components in the dehydration drum is not uniformly applied, resulting in low dehydration rate.

Furthermore, in conventional filter cloths, it is difficult to remove the solid components that have gotten into the nape as described above.

Therefore, when the cotton cloth is separated from the transfer drum, the solid components are pulled back toward the filter cloth by the raised fluff, resulting in poor transferability.

On the other hand, as shown in Fig. 3 (scanning electron micrograph of the surface, magnification: 30x) and Fig. 4 (scanning electron micrograph of longitudinal section, magnification: 30x), the conventional cotton cloth spout is not as good as the conventional filter cloth. However, the gaps between the piloerections are quite large,
Also deep. Moreover, not only is the density of the naps so low that the surface of the base material can be seen through, but the filtration layer is quite bulky because the naps are curled. Therefore, this conventional cotton cloth also has a low rejection rate and a low dehydration rate, as well as poor transferability, just like the conventional filter cloth A described above.

An object of the present invention is to provide a filter cloth that solves the above-mentioned drawbacks of conventional cotton cloth, has a high rejection rate and a high dehydration rate, and provides high transferability when used in a belt press type dehydrator.

To achieve the above object, the present invention is characterized by a filter cloth in which one side of a sheet-like channel base material is covered with a linear layer of ultrafine fibers having a thickness of 0.1 to 10 μm.

To explain one embodiment of the cotton fabric of the present invention, Fig. 5 is a perspective view of a filter fabric for a belt press type dehydrator using the cotton fabric of the present invention. Belts 2 and 3 with holes are sewn to both ends of the filter cloth 1 to spread out the filter cloth 1 and run it without meandering.

The cotton fabric 1 must be able to withstand stretching with a strong force and must be stitched so as not to impair its flatness. Preferably, both ends of the cotton fabric 1 in the longitudinal direction are folded back to the back side, butted together, and the abutted portion and the folded portion are sewn together. Belt 2.3
It is preferable that the filter cloth 1 has some elasticity so that it can be expanded without causing wrinkles in the filter cloth 1. Therefore, it is preferable that the belts 2 and 3 have a synthetic fiber fabric as a core material, and are made of a composite of the core material and rubber.

The stitching between the filter cloth 1 and the belts 2 and 3 is shown in FIG. 7 as a sectional view taken along line B-B in FIG. It is preferable to fold both ends of the cotton fabric 1 in the width direction to the back side and carry out the process at the folded parts.

The above-mentioned cotton cloth has a thickness of 0.1 to 10 μm obtained by raising the surface of a channel base material made of synthetic fiber fabric in one direction.
, preferably 0.3 to 7μ, more preferably 0.3 to 7μ
It is covered with naps of 5 μm ultrafine fibers, and the naps form a linear layer. Figures 8 (30x magnification) and 9 (300x magnification) show scanning electron micrographs of the surface of the filter cloth, and Figure 10 (60x magnification) shows a scanning electron micrograph of the longitudinal section. . These photographs show that the napped microfibers are present on the surface of the textile base material in an extremely high density and lie horizontally, and that the surface of the base material is covered with a large number of napped fibers in a layered manner, forming a linear layer with very little surface unevenness. It can be seen that it is formed.

The above-mentioned woven fabric has 200 to 50,000 single weft yarns made of twin or triple spun yarns or multifilament yarns of ultrafine fibers with a thickness of 0.1 to 10 μm, preferably 3 to 8 weft yarns to the warp yarns. It consists of a floating, preferably satin fabric. Then, with a density of 20 to 100 wefts/cm,
The filter cloth is arranged in the width direction of the filter cloth, the warp threads are arranged in the longitudinal direction, and the weft threads are mainly raised. The floating structure is adopted because this reduces the number of intersections between the weft and warp yarns, reduces the unevenness of the fabric surface, and provides a filter cloth with less surface unevenness. In addition, the warp yarns are made by bundling 10 to 150 fibers with a thickness of 10 to 30 μm, and the density of the weft yarns is 0.
It is preferable to arrange them at a density of 7 to 3 times. Furthermore, the reason why the weft yarns are mainly raised is that the warp yarns are subjected to a large spreading tension, and if these yarns are raised, the strength of the filter cloth will be reduced. In addition, if weft and warp yarns with a twist of 4 to 15 times/cm are used, a flow path for the base material can be secured even if the weave density is high, and the weft yarns have good retention of raised naps. This is preferable because it improves the properties and makes it difficult to fall out.

The synthetic fibers constituting the woven fabric are preferably polyamide fibers, polyester fibers, polyvinyl alcohol fibers, polyfluoroethylene fibers, polypropylene fibers, polyacrylonitrile fibers, etc. mainly from the viewpoint of durability. Depending on the type of substance to be dehydrated, it is also possible to use these fibers subjected to hydrophilic or hydrophobic processing.

The thickness of the raised fluff needs to be 0.1 to 10 μm as described above. That is, if it is thinner than 0.1μ, even if it is possible to increase the density of the naps, the strength will be low and it will break easily, making it impossible to obtain a filter cloth that can withstand practical use. Also,
The flow path resistance of the filter layer increases significantly, and the dewatering rate decreases extremely. On the other hand, if it is thicker than 10μ, it will become rigid and have standing fluff, making it impossible to form a layered filter layer, and the gaps formed between the fluffs will become large, making the gaps narrower. Solid components can be handled easily, resulting in an extremely low rejection rate of solid components. In addition, the surface irregularities become larger, and the solid components stuck in the depths
Coupled with the stiff erect hair being pierced, it becomes impossible to pull out.

FIG. 11 shows that the dehydrated substance has a particle size of 1 to several tens of μm.
100mg/microcystis, commonly known as blue-green algae.
Using pond water containing about liters, the height of piloerection d(μ)
The relationship between this and the rejection rate K (%) of solid components was investigated. The rejection rate is expressed as the ratio of the weight of the solid components contained in the recovered material to the weight of the solid components contained in the dehydrated material. Measure. From FIG. 11, it can be seen that when the thickness of the raised fluff exceeds 10 μm, the rejection rate decreases significantly and it no longer functions as a filter cloth for fine solid components such as blue-green algae. The upper limit of the thickness of the nap is preferably 7μ, more preferably 5μ. On the other hand, if the thickness of the raised floes is less than 0.1μ, it is theoretically expected that the rejection rate will be high, but if they are too thin, the filter layer will be severely damaged, and the scale will not be durable or the filter layer will flow. The road resistance increases extremely, and the dehydration rate significantly decreases as shown in FIG. 12 by the relationship between the nap thickness d (μ) and the solid component temperature C (wt%).

Another advantage of forming naps using ultrafine fibers with a thickness of 0.1 to 10 μm is that the flexibility of the fibers is inversely proportional to the fourth power of the thickness, so the naps become very flexible and transferable to the dehydration drum. Sometimes, the standing fluffs that have been lying down are smoothly raised one after another and separated from the solid components, reducing the force that pulls the solid components back toward the filter cloth and improving the transfer rate. In this case, if the naps lie facing in the opposite direction to the running direction of the filter cloth, the transfer rate will be further improved.

If the above-mentioned naps are extremely short, the surface of the base material cannot be sufficiently covered and the rejection rate decreases, and if they are too long, the naps become intertwined with each other and the transfer rate decreases.
It is preferable that the length is such that it can bridge up to six bridges. If the nap length is set as above, the naps will lie on the surface of the substrate without getting entangled, and the number of naps will be 100 to 40,000/.
It is possible to form a highly preferred filter layer of mm.

When the above filter cloth is used in a belt press type dehydrator, as shown in FIG. Endless filter cloth 1 with material to be dehydrated on top
is run, and the squeezing section squeezes out the liquid components in the material to be dehydrated, and at the same time, the material containing solid components 8 remaining on the filter cloth 1 is transferred to the surface of the dehydration drum 4, and scraped off with the scraper 9. Make sure to collect it. In this case, the filter cloth 1 is mounted so that the surface having the nap, that is, the surface thereof, faces the surface of the dehydration drum 40. The nap lies in the opposite direction to the running direction of the filter cloth 1, that is, toward the rear. Note that 11 is a holding section for the substance to be dehydrated, and the filter cloth 1 runs inside this holding section 11 and takes in the water substance adhering thereon. Opposed to this holding part 11, a vacuum dehydration part 12 is provided on the back side of the filter cloth 1, and the material to be dehydrated on the filter cloth 1 is first dehydrated under reduced pressure here, and then sent to the above-mentioned pressing part. I'm getting beaten up. 10
is a cleaning nozzle for the filter cloth 1.

The above-mentioned filter cloth can be manufactured by various methods, and preferred examples thereof will be shown below.

That is, the weft consists of an island component made of a polymeric material, preferably polyester, and a sea component made of a polymeric material, preferably polystyrene, and the island component is made of a polymer material, preferably polystyrene.
Using twin or triple spun yarns or multifisciment yarns of mixed spun fibers containing 5% or more of so-called multicore composite fibers or fibers that generate ultrafine fibers of 80% or more,
False twisted yarns or composite latent crimped yarns are used as warp yarns, and the weft and warp yarns are woven with satin so as to have a desired density and a desired floating structure.

Next, residual components of the weft yarn are removed with a suitable solvent, such as trichlorethylene, and after drying, the weft yarn is raised to form a nap, thereby forming a corrugated layer. Raising methods include needle cloth, sandpaper, sand cloth, sand net, whetstone, steel brush, polishing brush, and sand roll. Garnet, sand honing, etc. Among these, it is preferable to use clothing.

Another preferred method is to make a woven fabric using composite fibers obtained by laminating and spinning different polymeric substances, and then peeling off the laminated fibers and raising the fabric to form a nap. The polymer material to be laminated is preferably polyamide and polyester copolymer. As for the method of peeling, it is preferable to gently rub it in hot water and then cover it with air drying.

In the above embodiments, the channel base material is a woven fabric, and the wave layer is formed by raising the woven fabric (A). Or, after mixing the long fibers with fibers or fine particles having a lower melting point and making paper into paper, and partially melting the low melting point fibers or fine particles to integrate the ultrafine fibers,
The filter layer may be formed by buffing the surface and raising ultrafine fibers. Alternatively, the short fibers or long fibers may be accumulated using air flow or water flow, punched to form felt, and the surface of the felt may be raised to form a linear layer. Furthermore, woven fabrics, knitted fabrics, polymer films with many minute holes, etc. are used as channel base materials, and the above-mentioned paper or felt is integrally laminated on one side of these base materials without raising them. It is also possible to use it as a filter layer.

The filter cloth of the present invention is extremely suitable as a filter cloth for belt press type dehydrators, but it is also suitable for use in so-called twin cross type dehydrators, in which the material to be dehydrated is sandwiched between two filter cloths and dehydrated by pressing. It can also be used as a filter cloth. In this case, the problem with transferability mentioned above is that good transferability means that the solid components are not peeled off from the surface of the filter cloth, which creates the effect that the solid components are difficult to remain on the surface of the filter cloth. .

Since the filter cloth of the present invention can separate extremely fine solid components, it is extremely suitable for separating blue-green algae, etc., but it is also suitable for so-called suspended sludge, such as surplus sludge produced as a by-product from activated sludge treatment equipment. It can be used for concentrating and dewatering sludge, scum, flocs, wash water, concentrated sludge, etc. generated by wastewater treatment, such as so-called fixed sludge discharged from biofilm treatment equipment.

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 pressure flotation operations, coagulated flocs and coagulated sediment flocs generated from industrial wastewater treatment, backwash water from various filtration devices such as sand filtration devices, and screens. This includes sludge that has been concentrated using equipment. Further, the filter cloth of the present invention can be used, for example, in the paper pulp manufacturing industry, the food manufacturing industry, the sake brewing industry,
It can be used to recover solid components in various manufacturing industries, such as the brewing industry of miso and other products. For example, with biofilm sludge, the properties of the sludge can be changed by mixing suspended sludge produced as a by-product from activated sludge treatment equipment with fixed sludge discharged from the biofilm treatment equipment. When two or more types of dehydrated substances are mixed and used, processing ability and transferability may be improved.

As explained above, since the filter cloth of the present invention has a corrugated layer of ultrafine fibers with a thickness of 0.1 to 10 μm formed on one side of a sheet-like channel base material, the wave layer formed between the fibers is The gaps created are extremely small and can prevent fine solid components from entering. Therefore, fine solid components such as blue-green algae can be easily separated without using a flocculant, and the rejection rate is extremely high.

Further, since the filter cloth of the present invention has a wave layer formed of ultrafine fibers having a thickness of 0.1 to 10 μm, the fibers are flexible and easily lie on the surface of the curtain material. Therefore, deep gaps between the fibers are not formed, and solid components are prevented from deforming and getting into the gaps and becoming difficult to get out.This prevents clogging and greatly improves the dehydration rate. do. The fact that the fibers are flexible and easy to lie down also means that the wave layer that is formed is not bulky and the fiber filling rate is high.
The airtightness is improved when performing vacuum dehydration, and the dehydration rate is also increased in this respect.

Furthermore, the filter cloth of the present invention uses a transfer drum because the gaps between the fibers are small, making it difficult for solid components to enter the gaps, and the fibers are flexible, which prevents solid components from penetrating. It has high transferability when used in a dehydrator, and has high removability when used in a twin-cross type dehydrator.

Example A 20/2S spun yarn made by spinning 18 core multicore composite fibers (thickness 20μ) with polyester as the island component and polystyrene as the sea component was used as the weft, and polyester fibers with a thickness of 20μ were used as the weft. The final bundle is used as the warp, and the weft is 3
A 5-ply satin fabric with a warp of 0 yarn/cm and a warp of 40 yarn/cm was obtained.

Next, the sea component of the weft is removed using trichlorethylene as a solvent.
A fabric consisting of 000 bundles was obtained.

Next, the above-mentioned fabric was subjected to a napping machine, and mainly the weft yarns were raised in the warp direction to form a wave layer with a nap count of about 1000/mm to obtain the filter fabric of the present invention.

Next, the above filter cloth was cut into a width of 30 cm and a length of 1.8 m.
The endless filter cloth shown in FIG. 5 was constructed by sewing the cloth so that the warp direction became the longitudinal direction.

Next, the above-mentioned filter cloth was subjected to a belt press type dewatering machine shown in Fig. 13, and a dehydration test was conducted with the vacuum speed of the vacuum dehydration section set to -900 mmAq, the filter cloth running speed to 4 m/min, and the pressing load to the transfer drum to be 60 kg. Did. As the liquid separation substance, we used pond water, which mainly contains blue-green algae but also green algae and diatoms, and has a solid component concentration of about 100 mg/liter.
m2·hr). Note that no flocculant was used.

On the other hand, when the particle size distribution of the peripheral component in the dehydrated material was measured using a Coulter Counter TA11 manufactured by Coulter Electronics, USA, the particle size was distributed over a wide range from 1 to several tens of microns, and the average particle size was about 30 microns. there were.

Test results. The material recovered by scraping with a scraper had a solid content of about 17%, which was about 1700 times the original concentration. Further, the transfer rate to the transfer drum was extremely high at about 80%. Furthermore, when the particle size distribution of the solid components in the material that passed through the filter cloth was measured in the same manner as above, it was found that
It was 10μ, and most of the particles exceeding 10μ were removed.

Furthermore, even after approximately 1,200 hours of operation, the above-mentioned performance did not change at all, and no abnormality was observed in the filter cloth.

[Brief explanation of the drawing]

Figures 1 and 2 are scanning electron micrographs showing the shape of the fibers on the surface and cross-section of the membrane, respectively, of a conventional filter cloth, and Figures 3 and 4 are scanning electron micrographs showing a conventional shape different from the above. An electron micrograph, FIG. 5 is a schematic perspective view showing a filter cloth according to an embodiment of the present invention, and FIGS. 6 and 7 are sectional views taken along line AA and line BB in FIG. 5, respectively. 8 and 9 are scanning electron micrographs showing the shape of fibers on the surface of a filter cloth according to an embodiment of the present invention, and FIG. A scanning electron micrograph showing the shape of the fibers in the longitudinal cross section of the filter cloth, Figure 11 is a graph showing the relationship between the thickness d (μ) of the ultrafine fibers and the element rate K (%), and Figure 12 is the graph showing the relationship between the thickness d (μ) of the ultrafine fibers and the element rate K (%). FIG. 13 is a graph showing the relationship between the thickness d (μ) of the filter cloth and the peripheral component concentration C (wt%), and shows how the filter cloth of the present invention is used in a belt press type dehydrator. It is a schematic front view. 1: Filter cloth 2, 3: Belt with holes 4: Transfer drum 5: Press roll 6: Drive roll 7: Film water substance 8: Circumferential component 9: Scraper 10: Linear nozzle 11: Holding section 12 for the substance to be dehydrated : Decompression dehydration section

Claims (1)

[Claims] A filter cloth characterized in that one side of a sheet-like channel ridge is covered with a cline layer of ultrafine fibers having a thickness of 0.1 to 10 μm.