JPS6213046B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a filter cloth for solid-liquid separation, and more particularly to a filter cloth suitable for use in belt press type dehydrators and the like.

A belt press type dehydrator rotates an endless filter cloth on which a solid liquid is placed on a pressing section consisting of a transfer drum and a press roll. In addition, the so-called cake is transferred onto the surface of the transfer drum and collected by scraping it off with a scraper. In this case, it is common to provide a vacuum dehydration section opposite to the solid-liquid supply section, and reduce the pressure on the back side of the filter cloth to promote the passage of liquid components.

Conventionally, the filter cloth used for so-called solid-liquid separation is one in which thick short fibers with a thickness of 30 to 100 μm are flocked to the surface of a fabric using an adhesive to form raised naps (hereinafter referred to as conventionally called filter cloth),
It is like forming thick raised fibers with a thickness of several tens of microns on the surface of the fabric by raising the base material (hereinafter referred to as
Conventionally, filter cloth (referred to as filter cloth) is known. These conventional filter cloths provide the necessary strength as a filter cloth by the woven fabric, and also block solid components and remove water by the raised naps on the surface. In other words, the piloerection forms a filter layer. However, such conventional filter cloths A and B both have the drawbacks of low solid component rejection rate, dewatering rate, processing capacity, etc., and poor transferability.

In other words, 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 nape. The gaps between the particles are quite large, and fine solid components can easily pass through the gaps, resulting in a very low rejection rate. The reason why the gaps between the naps are so large is because the naps of this conventional filter cloth are formed by flocking with adhesive.
This is because in order to prevent the stitches of the fabric from being filled with adhesive, the density of the nap cannot be made very high, and because the thickness of the nap is very thick (30 to 100 μm), the gaps cannot be made very small. Therefore, when using this conventional filter cloth, it is necessary to coarsen the solid components using a polymer flocculant, etc., which not only increases running costs, but also
The toxicity of some flocculants is a problem. Also,
Use of a flocculant not only increases the amount of solid components, but also requires constant checking of the amount added, making it difficult to manage operating conditions.

In addition, the above conventional filter cloth has a nape thickness of 30 to 100.
It is extremely thick, so it is rigid and difficult to lie down on. Therefore, there is a problem that the gaps between the naps are very deep, and if the solid components enter the gaps while being deformed, they will have a hard time coming out, which will clog the filter cloth and reduce the processing capacity. This clogging tendency is further aggravated when the solid components are penetrated by the rigid standing fluff.
Furthermore, the fact that the raised floes are difficult to lie down also means that the filter layer formed by the raised floes is bulky, and therefore the airtightness in the vacuum dehydration section is poor, making it impossible to achieve a high dewatering rate. The lower the dehydration rate, the higher the moisture content of the resulting cake;
Post-processes such as incineration require a large amount of energy. In addition, conventional filter cloths have deep gaps between the naps, resulting in large irregularities on the surface, and the thickness of the solid components on the filter cloth becomes uneven, resulting in uneven pressure at the pressing part. Low dehydration rate.

Furthermore, in conventional filter cloths, the solid components that have gotten into the nape do not come out easily, as described above.
Therefore, during transfer to the transfer drum, the cake is pulled back toward the filter cloth by the raised fluffs, resulting in poor transferability.

On the other hand, as shown in Figure 3 (scanning electron micrograph of the surface, magnification: 30x) and Figure 4 (scanning electron micrograph of longitudinal section, magnification: 30x), the conventional filter cloth Although not as much, the gaps between the piloerections are still quite large and deep. Furthermore, not only is the nap density so low that the surface of the fabric can be seen through, but the naps are curled, making the filter layer quite bulky. Therefore, this conventional filter cloth B also has a low rejection rate, a low dehydration rate, and a low processing capacity, although it is not as good as the above-mentioned conventional filter cloth I, and also has poor transferability.

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

In order to achieve the above object, the present invention is such that a filter layer made of raised fibers is formed on the surface of an endlessly processed belt-shaped base material, and the base material is a woven fabric having at least a weft made of polyester fiber, and the weft is made of a polyester fiber. A filter cloth for solid-liquid separation, which extends in the width direction of the base material, and the raised naps are mainly made of ultrafine fibers with a thickness of 0.1 to 10 μm obtained by raising the weft yarns in one longitudinal direction of the base material. This is a characteristic feature.

To explain one embodiment of the present invention, FIG. 5 is a schematic perspective view showing a filter cloth for a belt press type dehydrator using the filter cloth of the present invention, and the filter cloth 1 is sewn at the dotted line. , belts 2 and 3 with holes are sewn to both ends thereof for stretching the filter cloth 1 and running it without meandering. The filter cloth 1 is
It is necessary to sew the filter cloth so that it can sufficiently withstand expansion under strong force and not impair its flatness.
It is preferable that both longitudinal ends of the fabric are folded back to the back side, butted together, and the abutted portion and the folded portion are sewn together. It is preferable that the belts 2 and 3 have some elasticity so that the belts 2 and 3 can be stretched to prevent wrinkles from forming on the filter cloth 1. Therefore, belts 2 and 3
It is preferable that the core material is a synthetic fiber fabric, and the material is made of a composite material of the core material and rubber.
The filter cloth 1 and the belts 2 and 3 are sewn together as shown in the BB cross-sectional view of FIG. 5 above in FIG. Next, fold both ends of the filter cloth 1 in the width direction to the back side,
It is preferable to perform this at the folded portion.

The filter cloth has a thickness of 0.1 to 10 μm, preferably 0.3 to 7 μm, obtained by directly raising the surface of a base fabric, at least the weft of which is made of polyester fibers.
It is covered with napped microfibers of μ, more preferably 0.3 to 5 μm, and a filter layer is formed by the napped fibers. FIG. 8 (30x magnification) and FIG. 9 (300x magnification) show scanning electron micrographs of the surface of the filter cloth, and FIG. 10 (60x magnification) shows a scanning electron micrograph of a longitudinal section. These photos show that the napped microfibers lie on the surface of the fabric and are present at an extremely high density, and that the surface of the fabric is covered with a large number of napped layers forming a filter layer with very little surface unevenness. .

The above fabric has 200 to 50,000 single weft yarns made of twin or triple spun yarn or multifilament yarn of ultrafine polyester fibers with a thickness of 0.1 to 10μ.
It is preferably made of satin fabric, with preferably 3 to 8 threads floating relative to the warp threads. The weft yarns are arranged at a density of 20 to 100 pieces/cm in the width direction of the filter cloth, the warp yarns are arranged in the longitudinal direction, and the weft yarns are mainly raised in the longitudinal direction (warp direction).
The floating structure is adopted because it reduces the number of intersections between the weft and warp yarns, resulting in a filter cloth with fewer surface irregularities. Further, the reason why the weft yarns are mainly raised is that the warp yarns are subjected to a large spreading tension, and if the warp yarns are raised, the strength of the filter cloth will be reduced. On the other hand, the warp is a bundle of 10 to 150 synthetic fibers such as polyester fibers, polyamide fibers, polyvinyl alcohol fibers, polypropylene fibers, and polyacrylonitrile fibers with a thickness of 10 to 30μ, and is 0.7 to 3 times the density of the weft. It is preferable to arrange them at a density of . In addition, weft and warp 4 to 15 times/
It is preferable to use one with a twist of about cm, as this improves the retention of the raised naps and makes them difficult to fall out.

The reason why polyester fibers are used for the weft yarns extending in the width direction of the filter cloth and the raised yarns are mainly formed by raising the weft yarns is as follows.

In other words, the ultrafine polyester fibers are easy to raise, and the ends of the hair do not curl, resulting in straight raised hair. Moreover, it is extremely durable. Therefore, it is extremely suitable for forming a filter layer. Polyamide fibers are also known as ultrafine fibers, but polyamide fibers have a high elongation, making them difficult to raise, and the length of the naps tends to be long and short, resulting in irregularities. Also, since the ends of the hair are curled, the raised hairs tend to tangle with each other. When the naps curl, they form pilling, which shortens the life of the filter cloth.

The thickness of the raised fluff needs to be 0.1 to 10μ as described above. In other words, if it is thicker than 10μ, it will become rigid and the fluff will stand up, making it impossible to form a layered filtration layer, and the gaps between the fluff will become large, allowing fine solid components to pass through. The blocking rate is extremely low. Also,
The surface irregularities also become larger, and the solid components stuck in the depths become stuck together with the rigid standing hairs and become unable to escape.

Figure 11 shows the thickness d (μ) of the standing floes and the solid Component rejection rate K
(%). Rejection rate K
is expressed as a percentage of the weight of the recovered solid component to the weight of the solid component contained in the solid liquid, and the weight of any solid component is measured after water is heated and evaporated. From FIG. 11, it can be seen that when the thickness of the raised fluff exceeds 10μ, the rejection rate decreases significantly, and it no longer functions effectively 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, the thickness of the piloerection is 0.1
If it is thinner than μ, even if it is possible to increase the density of the naps, the strength will be low and will break easily, making it impossible to obtain a filter cloth that can withstand practical use. Furthermore, since the flow path resistance of the filter layer increases significantly, the dehydration rate also decreases significantly, as shown by the relationship between the nap thickness d (μ) and the solid component concentration C (wt%) in FIG. 12.

Another advantage of forming napped fibers with ultrafine fibers with a thickness of 0.1 to 10μ is that the flexibility of the fiber is inversely proportional to the fourth power of the thickness, so the napped fibers become very flexible, and when transferred to the transfer drum, The standing fluff that had been lying down is smoothly raised one after another and separated from the cake, and the force that pulls the cake back toward the filter cloth is weakened, improving transferability. In this case, if the naps lie facing in the opposite direction to the running direction of the filter cloth, the transferability will be further improved.

If the above-mentioned raised naps are extremely short, the surface of the fabric cannot be sufficiently covered and the rejection rate decreases, and if they are too long, the raised naps intersect with each other and the transfer rate decreases.
The length is preferably such that it can bridge 2 to 6 wefts of the fabric. When the length of the naps is set as above, it is possible to form an extremely good filter layer in which the naps lie on the surface of the substrate without crossing each other and have a number of naps of 100 to 40,000/mm.

When the filter cloth of the present invention is used in a belt press type dehydrator, as shown in FIG. An endless filter cloth 1 loaded with solid liquid is run through a pressing section consisting of a compressor section, and the liquid component in the solid liquid is squeezed out at the pressing section, and the cake 8 formed on the filter cloth 1 is transferred to the surface of the transfer drum 4. Then, scrape it off with a scraper 9 and collect it. In this case, the filter cloth 1 is mounted so that the side having the nap, that is, the front surface, faces the surface of the transfer drum 4. Further, the raised naps are arranged in a direction opposite to the running direction of the filter cloth 1, that is, in a direction toward the rear.
Note that 11 is a solid-liquid supply section, and the filter cloth 1 travels within this supply section 11 and takes in the solid-liquid thereon. A vacuum dehydration section 12 is provided on the back side of the filter cloth 1 facing the supply section 11, and the solid liquid placed on the filter cloth 1 is first dehydrated under reduced pressure here, and then sent to the above-mentioned pressing section. go. 10 is a cleaning nozzle for cleaning the filter cloth 1 after cake transfer and subjecting it to the next dehydration process.

The filter cloth of this invention can be manufactured by various methods, but the most suitable method will be explained next.

That is, a so-called multifilamentary composite fiber is used as the weft, which is made up of polyester as the island component, and a polymeric substance, preferably polystyrene, as the sea component, and contains 35 to 75% of the island component, and as the warp. Using false twisted synthetic yarns or composite latent crimped yarns, 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 is removed with a suitable solvent, such as trichlorethylene, and after drying, the weft is mainly raised in the warp direction to form raised naps,
Constitutes a filter layer. Raising methods include needle cloth, sandpaper, sand cloth, sand net, whetstone, steel brush, Kenmaro brush, and sand roll. There are garnet, sand honing, etc. Among these, it is preferable to use clothing.

Another preferred method is to use spun yarn or multifilament of ultrafine polyester fibers as the weft yarns, while using the above-mentioned synthetic fibers as the warp yarns to produce a woven fabric, in which the weft yarns are mainly raised in the warp direction.

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 so-called twin-cross type dehydrators, in which a solid liquid is sandwiched between two filter cloths and dehydrated by pressing. It can also be used as cloth. In this case, the above-mentioned problem of transferability is that good transferability means that the cake is easily peeled off from the surface of the filter cloth, producing the effect that the cake is difficult to remain on the surface of the filter cloth.

Since the filter cloth of this invention can block even extremely fine solid components, it is extremely suitable for separating blue-green algae, etc.; It can be used to separate, concentrate, and dehydrate sludge, scum, flocs, wash water, concentrated sludge, etc. generated during wastewater treatment, such as so-called fixed sludge discharged from biofilm treatment equipment. can. 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 filters, and concentrated water from screen devices. There are Suratji etc. 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. In addition, for example, with biofilm sludge, the properties of the sludge can be changed by mixing suspended sludge produced by activated sludge treatment equipment with fixed sludge discharged from the biofilm treatment equipment. When more than one type of solid-liquid is mixed and used, processing ability and transferability may be improved.

As explained above, the filter cloth of the present invention has a filter layer made of napped microfibers with a thickness of 0.1 to 10 μm formed on the surface of the fabric, so the gaps formed between the napped fibers are extremely small. Even fine solid components can be blocked. Therefore, fine solid components such as blue-green algae can be easily separated without using a flocculant, and the rejection rate is extremely high.

In addition, since the filter cloth of the present invention has a filter layer formed of napped microfibers having a thickness of 0.1 to 10 μm, the napped fibers are flexible and easily lie on the surface of the fabric. Therefore, deep gaps are not formed between the raised fluffs, and the solid components are prevented from deforming and getting into the gaps and becoming difficult to get out.This prevents clogging and improves the dehydration rate. and processing capacity will be significantly improved. The fact that the fluff is flexible and easy to lie down means that the filter layer that is formed does not become bulky and the filling rate of the fluff is high, which improves airtightness when performing vacuum dehydration. This also increases the dehydration rate.

Furthermore, the filter cloth of the present invention has small gaps between the naps, and solid components are difficult to enter into the gaps.
Since the fluff is flexible, it is prevented from digging into the solid components, so it has high transferability when using a transfer drum and high removability when used in a twin-cross type dehydrator.

Furthermore, the filter cloth of the present invention has, as a base material,
We use a fabric whose at least weft is polyester fiber, which does not have high elongation and is easy to raise like polyamide fibers, and because the weft is mainly raised to form the nap, the length of the nap is relatively uniform. In addition, the tips of the bristles are relatively straight and do not curl as sharply as the naps of polyamide fibers, which prevents the naps from tangling with each other.Therefore, there is less worry about pilling, and the condition of the filter layer is stabilized. ing. Additionally, polyester fibers are highly durable and have a long lifespan.

Example: 18-core multicore composite fiber (thickness: 20μ) with polyester as the island component and polystyrene as the sea component
A 5-ply satin fabric with 20/2S spun yarn as the weft, and 48 bundles of 20μ thick polyester fibers as the warp, with 30 wefts/cm and 40 warps/cm. I got it.

Next, the sea component of the weft yarns was removed using trichlorethylene as a solvent to obtain a fabric whose weft yarns were made up of bundles of about 2000 ultrafine fibers with a thickness of about 2.5 μm.

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 filter layer having a nap count of about 1000/mm, thereby obtaining a filter cloth.

Next, the above-mentioned filter cloth was cut to a width of 30 cm and a length of 1.8 m, and sewn together so that the warp direction became the longitudinal direction to construct an endless filter cloth as shown in FIG. 5.

Next, the filter cloth was applied to a belt press type dehydrator shown in Fig. 13, and the degree of vacuum in the vacuum dehydrator was reduced to -900mm.
A dehydration test was conducted with Aq, filter cloth traveling speed of 4 m/min, and pressing load on the transfer drum of 60 kg. The solid liquid is mainly composed of blue-green algae, but also contains green algae and diatoms, with a solid component concentration of approximately 100mg/
A liter of pond water was used and was supplied at a rate of approximately 40 liters/minute (approximately 16 m ³ /m ² ·hr). In addition,
No flocculant was used.

On the other hand, when the particle size distribution of the solid component in the solid liquid was measured using a Coulter Counter TAII manufactured by Coulter Electronics Co., USA, the particle size was distributed over a wide range of 1 to several tens of microns, and the average particle size was about 30 μm.

As a result of the test, the material recovered by scraping with a scraper was approximately 17% solids, which was approximately 10% of the original concentration.
It was 1700 times hotter. Furthermore, the transfer rate to the transfer drum was extremely high at approximately 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 to be approximately 1 to 10 microns, and most of those exceeding 10 microns were removed. Also, about
Even after 1200 hours of operation, the above 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 longitudinal section of a conventional filter cloth, respectively. Figures 3 and 4 are photographs of a conventional filter cloth different from the above. FIG. 5 is a schematic perspective view showing a filter cloth according to an embodiment of the present invention, and FIGS. AA sectional view and BB sectional view, FIGS. 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 section of the filter cloth shown in FIGS. 8 and 9 above, and FIG. The graph showing the relationship, Figure 12, is
Thickness of piloerection d (μ) and solid component concentration C (wt%)
FIG. 13, which is a graph showing the relationship between . 1: Filter cloth, 2, 3: Belt with holes, 4: Transfer drum, 5: Press roll, 6: Drive roll, 7: Solid liquid, 8: Cake, 9: Scraper, 10: Washing nozzle, 11: Solid liquid Supply section, 12: vacuum dehydration section.

Claims (1)

[Claims] 1. A filter layer made of raised fluff is formed on the surface of an endlessly processed strip-shaped base material, and the base material is a woven fabric in which at least the weft threads are made of polyester fibers, and the weft threads extend in the width direction of the base material, A filter cloth for solid-liquid separation, characterized in that the nap is mainly made of ultrafine fibers with a thickness of 0.1 to 10 μm obtained by raising the weft yarns in one longitudinal direction of the base material.