JPS6363311B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid-liquid separation method, and more specifically, an endless filter cloth carrying a solid liquid is run through a pressing section consisting of a transfer drum and a press roll, and the solid liquid is compressed to separate liquid components. The present invention relates to a so-called filter cloth running type solid-liquid separation method in which the cake is squeezed out, the formed cake is transferred to a transfer drum, and the cake is scraped off and collected.

Conventionally, an endless filter cloth carrying a solid liquid is run through a pressing section consisting of a transfer drum and a press roll.
The so-called filter cloth running type solid-liquid separation, in which the liquid component is squeezed out in the above-mentioned squeezing section, and the cake formed by this squeezing is transferred to a transfer drum and collected by scraping with a scraper, is used in various fields. It is being said.

In such solid-liquid separation, it is of course necessary that the solid component and liquid component be removed well. shows high fluidity and protrudes from the edges of the filter cloth, reducing the recovery rate of solid components. This phenomenon is particularly remarkable when the solid liquid is a so-called difficult-to-filter solid liquid with an average filtration specific resistance of 10 ¹⁰ cm/g or more. Furthermore, if the thickness of the cake on the filter cloth is uneven, the transfer rate to the transfer drum will decrease, resulting in a low recovery rate as well. Furthermore, if the mesh of the filter cloth is not small enough,
Small solid components easily pass through, which also causes a reduction in recovery.

By the way, in the above-mentioned solid-liquid separation, conventionally, 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 a raised nape that is inclined in one direction, such as a filter cloth or a textile. A filter cloth is used, which is formed by raising the base material to form thick raised fluffs of several tens of microns in thickness on the surface of the base material. These filter cloths obtain the necessary strength as a filter cloth due to the woven base material, and also prevent solid components from being absorbed by the raised naps on the surface. In other words, the piloerection forms a filter layer. However, it is difficult to obtain a high recovery rate of solid components using such filter cloths.

In other words, the above-mentioned filter cloth has raised fluffs formed by flocking with adhesive, and in order to prevent the eyes of the base material from being buried by the adhesive, it is necessary to make the fluff density high and to reduce the raised fluff density. Since it is very thick (30 to 100 μm in thickness), the gaps, or eyes, formed between the pili are quite large, and fine solid components can easily pass through the gaps. In other words, the blocking rate is low.

In addition, the filter cloth has very thick naps of 30 to 100 μm in thickness, so it is rigid and difficult to lie on the surface of the base material. Therefore, the gaps formed between the raised fluffs are very deep, and if a solid component gets into the gaps, it is difficult to get out, resulting in poor transferability.

For the reasons mentioned above, if the above filter cloth is used, not only will a large amount of solid components be included in the liquid component, but the amount of solid components that can be recovered is small. In other words, the recovery rate of solid components is very low.

On the other hand, the above filter cloth, although not as good as the filter cloth,
As expected, the gaps between the piloerections are quite large and deep. Therefore, when this filter cloth is used, the recovery rate is similarly low.

On the other hand, the inventors of this invention previously filed a patent application in 1983.
−93591 (Japanese Patent Publication No. 63-14644) and Patent Application No. 57-226384 (Japanese Patent Publication No. 62-13046)
proposed a new type of filter cloth. In these filter cloths, the so-called filter layer on the surface of the base material is formed of napped ultrafine fibers with a thickness of 0.1 to 10 μm.

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, since the napped fibers of ultrafine fibers are very flexible and lie easily, the gaps between the napped fibers are shallow, and it is rare for solid components to get into the gaps while being deformed and become difficult to get out. Furthermore, the transferability is good 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.

In this way, when the filter cloth proposed in the above-mentioned applications is used, a higher recovery rate of solid components can be obtained than when using the above-mentioned filter cloth, but the average filtration specific resistance is ¹⁰ cm/g. For certain solid liquids that are difficult to filter, a sufficient recovery rate cannot be obtained unless the usage conditions are appropriate.

The purpose of this invention is to have an average filtration specific resistance of 10 ¹⁰ cm/
It is an object of the present invention to provide a method that can obtain a high recovery rate of solid components even when separating solid liquids that are highly difficult to filter, such as those having a particle size of more than 100 g.

In order to achieve the above object, in this invention, an average filtration specific resistance of 10 ^{to 10} cm/g is applied to the surface of an endless filter cloth that runs and circulates in one direction through a pressing section consisting of a transfer drum and a press roll. The above solid liquid was supplied, the solid liquid was squeezed to squeeze out the liquid component without protruding from the edge of the filter cloth, and the cake formed by this compression was transferred to the transfer drum. When collecting after scraping, use a filter cloth having a raised filter layer of ultrafine fibers with a thickness of 0.1 to 15 μm formed by raising the base material on the surface of a woven or knitted fabric base material as the filter cloth, Further, a solid-liquid separation method is provided, which is characterized in that the cake thickness during transfer is 10 to 1000 μm.

To explain the method of the present invention in more detail, FIG. 1 is a schematic side view showing the method of the present invention being carried out.

In Fig. 1, a so-called hard-to-filter solid material with an average filtration specific resistance of 10 ^{to 10} cm/g or more is installed in the compression section consisting of a transfer drum 1 rotating at a constant speed in the direction of the arrow and press rolls 2 and 8. The endless filter cloth 4 carrying the liquid 3 is run, and the solid liquid 3 is squeezed out from the edge of the filter cloth 4 to squeeze out the liquid component, and the filter formed by this compression is The cake on the cloth 4 is transferred to the transfer drum 1, scraped off with a scraper 5, and collected. In this case, the filter cloth 4
is driven by one press roll 8.
In other words, the press roll 8 also serves as a drive roll for the filter cloth 4. The driving speed of the filter cloth 4 is 10~
It is relatively fast at 100m/min. Incidentally, reference numeral 6 is a water spray nozzle for washing the filter cloth from the front and back surfaces after the transfer. In addition, 7 maintains the back side of the filter cloth 4 in a reduced pressure state of 500 mm or more in water column through the suction pipe 9, and sucks the solid liquid 3 supplied onto the filter cloth 4 under reduced pressure to prevent the liquid component from passing through. This is a vacuum suction tank for discharging the passed liquid components from the drain pipe 10.

In the above, the filter cloth covers the surface of a base material made of woven or knitted synthetic fibers with napped ultrafine fibers with a thickness of 0.1 to 15 μm, preferably 0.3 to 10 μm, obtained by directly raising the base material, A filter layer is formed by the raised fluff.

The above fabric has 200 to 50,000 single weft yarns made of twin or triple spun yarns or multifilament yarns made of ultrafine fibers with a thickness of 0.1 to 15 μm to the warp yarns.
It preferably consists of 3 to 8 strands, preferably satin fabric. Then, 20 to 100 weft threads/
cm, and are 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 in the warp direction. Therefore, piloerection has directionality. When in use, the filter cloth is stretched so that the direction of the nap is opposite to the running direction of the filter cloth, as shown in FIG. The reason why the weft yarns are mainly raised is that since a large tension is applied to the warp yarns, if the warp yarns are raised, the strength of the filter cloth will be reduced. In addition, the warp threads have a thickness of 10~
10 to 150 bundles of 30μ fibers are arranged at a density of 0.7 to 3 times the density of the weft. The floating structure is used because it reduces the number of intersections between the weft and warp yarns, reduces the unevenness of the fabric, and provides a filter cloth with less surface unevenness. In the above, if the weft and warp yarns have a twist of about 4 to 15 times/cm, the flow path of the base material can be secured even if the weaving density is high, and the weft yarns can maintain the nap. It is preferable because it improves the properties and makes it difficult to fall out.

As the knitting base material, circular knitting typified by rib knitting, double-sided knitting, etc., and warp knitting typified by half knitting, Queen's cord knitting, etc., using the same yarn as the above-mentioned woven fabric, can be used. Among these, half-knit and tricot-knit fabrics are preferred because they are relatively easy to form naps.

The synthetic fibers constituting the woven or knitted fabrics 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 solid-liquid, it may be preferable to use these fibers that have been subjected to hydrophilic or hydrophobic processing.

The filter cloth as mentioned above has a basis weight of 100 to 400 g/m ²
It is preferable that In other words, the basis weight is 100g/
If it is less than m ² , the filter cloth tends to stretch due to tension during running, resulting in poor running stability. Furthermore, a filter cloth with a basis weight exceeding 400 g/m ² is not economical because it requires high water pressure during washing.

Furthermore, the filter cloth used in this invention has a porosity of 50 when a load of 240 g/cm ² is applied to the surface of the filter cloth at a temperature of 20 ± 2°C and a relative humidity of 65 ± 5%.
Preferably it is ~75%. In other words, the porosity is
If it is less than 50%, the flow path resistance increases and the throughput decreases, which is not practical. On the other hand, if it exceeds 75%, the filter cloth tends to contain a large amount of liquid component, which increases the time required for solid-liquid separation, making it necessary to use a long filter cloth, which is not preferable.

The filter cloth used in this invention can be manufactured by various methods. Next, a preferable example of this 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, twin or triple spun yarns or multifilament yarns of mixed spun fibers containing 80% or more of fibers that generate ultrafine fibers are used as warp yarns. Using a false twisted yarn or a composite latent crimped yarn, 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 raised to form a nap, thereby forming a so-called filter layer.

Another method is to make a woven or knitted fabric from a composite fiber obtained by laminating and spinning different polymeric substances, then peeling off the lamination, and raising the fibers to form a nap. 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.

Methods for forming the nap include cloth, sandpaper, sand cloth, sand net, grindstone, steel brush, polishing brush, sand roll, garnet, sand honing, etc. Among them,
Most preferably by means of clothing.

Now, as mentioned above, the thickness of the nap of the filter cloth is
It needs to be 0.1-15μ. That is, if it is thinner than 0.1 μm, even though it is possible to increase the density of the naps, the strength is low and it easily breaks, making it impossible to obtain a filter cloth that can withstand practical use. In addition, the flow path resistance of the filter layer increases significantly, resulting in not only a significant decrease in efficiency but also a decrease in solid-liquid separation efficiency. On the other hand, if it is thicker than 15μ, it will become rigid and have raised fluffs, making it impossible to form a layered filter layer, and the gaps between the fluffs will become large, allowing fine solid components to pass through. , the rejection rate of solid components decreases. In addition, the surface irregularities also become large, and the solid components stuck in the depths become difficult to come out due to the piercing of the stiff raised fluffs, resulting in a significant decrease in transferability.

The graph shown by the dotted line in Figure 2 shows the surplus sludge discharged as solid-liquid from the activated sludge treatment equipment of a chemical factory (average filtration resistivity: 4.5 x ¹⁰ cm/g , solid component concentration: 8000mg/
The relationship between the thickness d (μ) of the raised pils and the rejection rate K (%) of solid components was investigated using the following method. The 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 each solid component is measured after heating and evaporating water. From this second figure,
It can be seen that when the thickness of the raised fluff exceeds 15μ, the rejection rate decreases significantly and it no longer functions as a filter cloth. That is, a filter cloth with a nape thickness of more than 15 μm has little effect on the rejection rate of solids and liquids with an average filtration specific resistance of 10 ¹⁰ cm/g or more. The preferable upper limit of the thickness of the nap is 12μ. In this experiment, the cake thickness at the time of transfer was approximately 100 μm.

Another advantage of having a nap thickness of 0.1 to 15μ is that the flexibility of the fiber is inversely proportional to the fourth power of the thickness, so the nap becomes very flexible, and the nap becomes smooth when transferred to the transfer drum. The reason is that the force that pulls the cake away from the cake and returns it to the filter cloth becomes weaker, and the transferability improves.

If the nap is extremely short, it will not be possible to sufficiently cover the surface of the base material, so it is preferably long enough to bridge 2 to 6 wefts of the base material. If the nap length is set as above, the base material length is 1
It is possible to form an extremely preferable filter layer having a number of raised fibers of 100 to 40,000 per mm.

In the method of the present invention, the thickness of the cake on the filter cloth at the time of transfer must be in the range of 10 to 1000 microns.

The graph shown by the solid line in FIG. 2 shows the cake thickness T (μ) measured under the same conditions as the above-mentioned rejection rate.
This shows the relationship between the transfer rate P (%) to the transfer drum, and it shows that if the cake thickness is less than 10μ, the transfer rate is very low, and if it exceeds 1000μ, the transfer rate decreases significantly, and it is no longer the purpose of this invention. It turns out that it cannot be achieved. Therefore, the solid component thickness of 10 to 1000μ depends on the type of solid liquid.
This can be achieved by appropriately adjusting the amount of solid liquid supplied, the type and running speed of the filter cloth, the gap between the transfer drum and the press roll, etc. In other words,
By appropriately selecting the above-mentioned conditions, the solid liquid will not protrude from the edge of the filter cloth, and the thickness of the cake at the time of transfer will be 10 to 1000 μm.

Now, in the method of this invention, the average filtration specific resistance is
10 Applicable to solid liquids with a density of ¹⁰ cm/g or more. Here, the average filtration specific resistance is measured as follows,
defined.

First, a separate type filter specified in JIS M 0202-1974 "SS measurement method" is prepared. The filter has an effective filtration area of ^9.62cm2 on the bottom funnel
(35mm in diameter) and the upper funnel has a height of 200mm
Use one with the same diameter from the filter surface to the top. Additionally, a graduated cylinder is placed inside the suction bottle in order to measure the amount of liquid component to be filtered. Furthermore, in order to reduce errors at the start of measurement, a glass cap is attached between the bottom funnel and the rubber stopper, and the vacuum bottle is maintained at 1000 mm in water column before opening the cap. Be ready to start.

On the other hand, as a filter paper, glass fiber filter paper AP40 047 manufactured by Millipore Corporation in the United States was used.
Prepare 05.

In addition, the solid liquid to be measured has a concentration of solid components.
Adjust it to 0.5 to 1.0% by weight. If the concentration is outside the above range, adjust by concentrating or diluting it. When diluting, a liquid component obtained by filtering the same solid liquid is used. Maintain the prepared solid-liquid at 20°C.

Next, load filter paper into the filter, close the pot, and maintain a water column of 1000 mm inside the suction bottle.

Next, in the upper funnel, add 100 ml of the solid liquid prepared by
, open the pot, and use a measuring cylinder to read the time t from the time the pot is opened for each fixed amount of filtration (5 ml is appropriate) until the amount of filtration reaches 50 ml.

Next, in order to calculate the quality/dry mass ratio n of the solid components, for the 10 ml of solid liquid prepared in above,
Perform the same operation as . However, in this case, it is not necessary to measure the amount of filtration. When a solid component is formed on the filter paper and there is no free liquid component on the surface layer, 30 seconds after the surface of the solid component appears, the pot is closed.

Next, remove the filter paper from the filter and measure the moisture content γ of the solid components attached to it using JIS K
0102-1981 "Factory wastewater test method" 14.2
Measured by term.

Next, the dry mass ratio n is calculated from the following formula.

n=1/(1-γ) Next, from the filtration amount V and time t, a graph is drawn with V as the horizontal axis and dt/dV as the vertical axis, and its slope k is determined.

Next, the average filtration specific resistance α of solid-liquid is determined from the following equation.

α=k・gc・△p・A ² (1−ns・s)/δ・
ρ・s However, gc: Gravity conversion coefficient [980 (g・cm/sec ²・g−
force)] Δp: Filtration pressure [100 (g-force/cm ² )] A: Filtration area [9.62 (cm ² )] δ: Filtrate viscosity (g/cm・sec) ρ: Filtrate density (g/cm ³ ) s: solid component concentration (g/g) The method of this invention has an average filtration specific resistance of 10 ¹⁰ cm/g.
Since a high recovery rate of solid components can be obtained for difficult-to-filter solid liquids having a particle size of more than 100 g, this method can be used to separate various solid liquids. 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.

As explained above, the filter cloth of the present invention uses a filter cloth having, on the surface of a woven or knitted fabric base material, a napped filter layer of ultrafine fibers with a thickness of 0.1 to 15 μm made by raising the base material, Squeeze the solid liquid so that it does not protrude from the edge of the filter cloth, and keep the cake thickness at the time of transfer from 10 to 10.
1000μ, it is possible to obtain a high recovery rate of solid components for difficult-to-filter solid liquids with an average filtration specific resistance of 10 ¹⁰ cm/g or more.
This will be specifically explained below based on examples.

Example: The weft is a 20/2S spun yarn made by spinning 16-core multicore composite fibers (thickness 20μ) with polyester as the island component and polystyrene as the sea component.
A 5-ply satin fabric with a warp of 48 bundles of 20 μm polyester fibers and a weft of 30/cm and a warp of 40/cm was obtained.

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 2.5 μm.

Next, the above-mentioned fabric was put through a napping machine, and 20
Repeat the napping operation twice, and then repeat the napping operation 10 times in the opposite direction to mainly nap the weft yarns and increase the number of naps.
A filter cloth with a density of 1000 pieces/mm was obtained.

Next, the filter cloth was cut into a width of 30 cm and a length of 2.3 m with the warp direction as the longitudinal direction, and the cut ends were sewn to obtain an endless filter cloth.

Next, the endless filter cloth was placed in the dehydrator shown in Fig. 1, and a dehydration test was conducted with the running speed of the filter cloth being 14.5 m/min, the degree of vacuum in the vacuum suction tank being 600 mm water column, and the pressing force against the transfer drum being 60 kg. did. As a solid liquid,
Excess sludge (average filtration resistivity: approximately 4.5 x ¹⁰ cm/g, solid component concentration: approximately 8000 mg/liter) discharged from an activated sludge treatment equipment at a chemical factory was used and was supplied at a rate of 10 liters/min. . The cake thickness during transfer was 100μ.

As a result of the test, no solid liquid was observed to protrude from the edge of the filter cloth. The rejection rate of solid components is approx.
It was 98%. In addition, the transfer rate to the transfer drum is 97
It was %. Furthermore, the recovery rate of solid components is approximately 95%.
It was extremely expensive. Furthermore, the liquid component in the recovered cake was 82.7%, indicating that the liquid component was well removed.

[Brief explanation of drawings]

Fig. 1 is a schematic side view showing how the method of the present invention is carried out, and Fig. 2 shows the thickness d (μ) of the raised hair.
It is a graph showing the relationship between and the rejection rate K (%) of the solid component, and the relationship between the cake thickness T (μ) and the transfer rate P (%). 1... Transfer drum, 2, 8... Press roll, 3...
Solid liquid, 4...Filter cloth, 5...Scraper, 6...Water spray nozzle, 7...Reduced pressure suction tank, 9...Intake pipe, 10
...Drainage pipe.

Claims (1)

[Claims] 1. A solid liquid having an average filtration specific resistance of ¹⁰ cm/g or more is supplied to the surface of an endless filter cloth that runs and circulates in one direction through a pressing section consisting of a transfer drum and a press roll. is squeezed to squeeze out the liquid component without protruding from the edge of the filter cloth, and when the cake formed by this compression is transferred to a transfer drum and then scraped and collected, as the filter cloth. , use a filter cloth on the surface of a woven or knitted fabric base material that has a napped filter layer of ultrafine fibers with a thickness of 0.1 to 15 μm made by raising the base material, and make the cake thickness at the time of transfer 10 to 1000 μm. A solid-liquid separation method characterized by the following.