JP4849381B2 - Belt type filtration concentrator - Google Patents

Description

  The present invention relates to an improvement in a belt-type filtration concentrator that concentrates sludge such as excess sludge, mixed raw sludge, digested sludge, or OD excess sludge.

Belt-type filter concentrators using filter cloth have been put into practical use for a long time, and have also been adopted in belt press concentration zones. The filter cloth as a filter medium has various options such as material, aperture ratio, air permeability, mesh opening, strength, woven shape, light weight and low cost, so it is used in most belt type filter concentrators. . The filter cloth used in conventional belt-type filter concentrators is generally selected with a small mesh opening, with an emphasis on ensuring a certain sludge solids recovery rate. There are some disadvantages in the discharge performance. The strength of the fiber that weaves the filter cloth is not as strong as that of metal, and the life of the filter medium is not as long as that of a wire mesh due to abrasion caused by sliding. In recent years, it has been proposed to use a metallic filter medium having a good filtrate discharging property, a good peeling property and a good cleaning property for a belt-type filtration concentrator. For example, a belt body with a gap between the upper layer and the lower layer is formed by abutting ring-shaped wires, and suction is performed by the upper layer capillary phenomenon, and the sludge is drained by vibration and bending of the endless belt. The device is known as described in US Pat. Further, as a technique related to a draining device for an endless belt made of a metal wire, a belt type concentrator in which a support plate is arranged at a predetermined interval below the endless belt is also described in Patent Document 2, for example. It is well known.
Japanese Patent No. 3504252 (paragraph numbers 0009 to 000 12, FIGS. 2 and 3) Japanese Patent Laying-Open No. 2005-95845 (paragraph numbers 0024 to 0 025, FIG. 4)

  The filter cloth used in the conventional belt-type filter concentrators has a support roll that is supported to prevent the filter cloth from sagging, and shares the weight of the filter cloth and sludge between the rolls. The support surface pressure is relatively large, and this acts intermittently, and wear of the filter cloth is accelerated. Endless belts such as metals that form wires in close contact with each other have a capillary water absorption function, so the water absorption function from sludge is excellent, while the high capillary water absorption function increases the drainage resistance of the filtrate. . The sludge solid matter that has entered the middle part of the upper and lower layers having voids is extremely difficult to discharge, and the sludge solid matter cannot be excluded unless it is carefully washed. Also, in an endless belt made of a wire such as metal, if the endless belt and the carrier roller that shares the weight of sludge are arranged at a narrow interval, the bending between the rollers will be reduced, and vibration and bending will be eliminated. It is not suitable for the initial stage when a large amount of gas must be discharged. When the arrangement interval of the support plates for supporting the conventional endless belt is narrowed, the vibration and bending action of the endless belt are lost, the filtrate discharge is hindered, and the draining action cannot be promoted. The endless belt is in sliding contact with the end corners of the support plate, and the progress of wear during passage is inevitable. In endless belts such as a ribbon network, rough irregularities are formed on the front and back surfaces between metal wires, and concentrated sludge remains when scraping with a scraper, and a large amount of washing water is required because of clogging. The solid concentration in the separated filtrate is high, and the washing nozzle may be clogged, and the filtrate cannot be used as washing water. The present invention provides a belt-type filtration concentrator that combines a filter medium having an existing capillary water-absorbing action and a drainage action to exert a concentration function.

  The belt-type filtration concentrator according to the present invention is a woven fabric having a capillary water absorption function in a concentrating device that circulates an endless belt between rolls and feeds sludge to a filtration surface of the endless belt for solid-liquid separation. The upper traveling filter medium is stretched, and the filtration surface of the upper traveling filter medium is slidably supported on the lower fixed filter medium, and a deep slot with a drainage function is formed in the lower fixed filter medium in the traveling direction of the upper traveling filter medium. Because of the synergistic effect of the capillary water absorption function of the running filter medium and the drainage function of the fixed filter medium, it exhibits outstanding capillary water absorption and drainage functions, so it can concentrate well even in low-concentration sludge that requires a large amount of filtrate discharge. The action can be secured. And since the filtration surface of the upper traveling filter medium supplied with the sludge is supported by the lower fixed filter medium, the surface pressure of the upper traveling filter medium is reduced, and wear due to dripping of the upper traveling filter medium is eliminated. The elongated holes of the lower fixed filter medium are continuously arranged in the traveling direction of the upper traveling filter medium, and the lower fixed filter medium slidingly supported on the upper traveling filter medium is always lubricated by the filtrate, so that the filter medium is less worn.

  The upper traveling filter medium is composed of a filter cloth or a net conveyor belt wire mesh, and the lower fixed filter medium is composed of a wedge wire or a parallel wire mesh, and the lower fixed filter medium of the wedge wire or parallel wire mesh has an elongated hole penetrating in the thickness direction. Therefore, while maintaining the strength of the upper traveling filter medium of the filter cloth or the net conveyor belt wire mesh, the clogging of the elongated holes due to the stagnation of the solid matter does not proceed and water permeability can be secured. Appropriate sludge concentration and solids recovery rate can be obtained, and the filter function can be used for a long time without lowering the filtration speed and causing poor peeling. When the wedge wire and filter cloth are combined, the elongated holes expand from the filtration surface side toward the filtrate discharge side, strengthening the characteristics of the metal filter medium that is hard to clog, and concentrating to exhibit capillary water absorption and drainage. Function is obtained.

  The filter surface of the upper traveling filter medium and the lower fixed filter medium that slidably supports the upper traveling filter medium are formed with an inclination angle of the upward gradient toward the traveling direction of the filter cloth, and a composite filter medium having a slight upward gradient is adopted. As a result, the filtrate having a high flow velocity flowing through the gap between the elongated holes applies a negative pressure to the filter cloth to enhance the discharge function. The filtrate is discharged along the elongated holes of the lower fixed filter medium without stagnation, the filtrate dischargeability (concentration performance) is greatly improved, and a high solids recovery rate is also obtained.

  The lower fixed filter medium is divided, and the elongated holes of the divided fixed filter medium are sequentially reduced in the traveling direction of the upper traveling filter medium, and the filtration surface of the upper traveling filter medium has an amount of filtrate to be discharged as it moves to the latter stage in the traveling direction. Capillary water absorption capacity is required rather than drainage capacity. If the elongated holes of the split fixed filter medium are sequentially reduced and opened in the traveling direction of the upper traveling filter medium, the water absorption function of the capillary tube will increase, and the concentration will be improved by reducing the moisture content compared to the conventional filter medium with a constant pore diameter. Therefore, the pore diameter and pitch of the fine metal filter medium can be appropriately set according to the demand for the amount of filtrate to be discharged and the capillary water absorption capacity. In addition, if the lower fixed filter medium is divided, the divided fixed filter medium can be easily processed, and a relatively heavy load of the divided fixed filter medium can be assembled in a divided form even in the initial assembly. There is no obstacle to work.

  The narrow hole width and wire interval of the plurality of divided fixed filter media that slidably support the filtration surface of the upper traveling filter medium are sequentially reduced and opened in the range of 0.2 to 20 mm in the traveling direction of the upper traveling filter medium. In the initial stage of sludge injection, which requires a draining function, the opening size of the divided fixed filter medium is made larger. In the middle period, when the capillary water absorption capacity is required rather than the drainage capacity, the opening of the divided fixed filter medium is compared with the initial stage of input. The latter divided fixed filter medium is further reduced to increase the capillary water absorption capability, and the capillary water absorption function and the drainage function can be further amplified.

The filtration surface of the upper traveling filter medium may be divided into an input concentration zone immediately after mud supply and a concentration zone for performing sludge concentration, and a plurality of divided fixed filter media obtained by dividing the lower fixed filter medium may be arranged in the concentration zone. In the input concentration zone from which the lower fixed filter medium is removed, there is no resistance to the discharged filtrate, and a large amount of filtrate can be discharged. In the input concentration zone of the sludge input part, a slight bending action is generated in the upper traveling filter medium, the sludge reservoir is slightly deepened to increase the concentration pressure, and the concentration time can be increased to increase the concentration effect.

If a dam plate-like connection support member is arranged on the back surface of the elongated fixed filter member in the direction crossing the upper traveling filter medium, the filtrate flowing down along the elongated hole of the lower fixed filter medium is connected to the connection support member. It can be dammed and dropped and removed from the filter medium at appropriate intervals. The filtrate is accumulated in the lower fixed filter medium and does not hinder the discharge from the upper traveling filter medium to the lower fixed filter medium, and can be efficiently drained as a draining medium. Then, a predetermined gap may be provided between the divided fixed filter medium before and after the lower fixed filter medium that slidably supports the filtration surface of the upper traveling filter medium, and the filtrate is discharged from the downstream gap of the divided fixed filter medium. By this, the filtrate which flows along a wedge wire is parted and the draining function improves.

  If a cleaning device is provided on the back surface of the lower fixed filter medium, the lower fixed filter medium can be cleaned, the filter medium function is maintained, and the service life is extended. By removing the lower fixed filter medium in the input concentrating zone, the filtrate in the input concentrating zone with a large amount of filtrate discharge does not interfere with the cleaning of the lower fixed filter medium, and at the same time as sludge concentration in the upper traveling filter medium at high speed In this way, it is possible to clean the divided fixed filter medium. If the upper traveling filter medium is a filter cloth, a high solid matter recovery rate is maintained, so that the filtrate can be recycled and the filter medium can be washed, and the supply of cleaning water becomes unnecessary. If the split fixed filter medium is constituted by the wedge wire, the clogging can be easily eliminated because it is cleaned from the wire hole on the widening side that expands from the sliding contact surface side of the upper traveling filter medium to the filtrate discharge side.

  Since the belt type filtration concentrator according to the present invention is a belt type filtration concentrator of a composite filter medium combining an upper traveling filter medium having a capillary water absorption function and a lower fixed filter medium having an excellent drainage function, the capillary water absorption action and the drainage action As a result of this synergistic effect, a large amount of filtrate can be discharged, and the concentration performance and throughput can be improved. If a filter cloth is used for the upper running filter medium, the filtrate can be recycled and used as wash water while maintaining the high solid matter recovery rate and high washability of the filter cloth. With low water pressure and less wash water The filter medium surface can be regenerated. And while the lower fixed filter medium is lubricated with the filtrate, the upper running filter medium is supported by the filtration surface, so wear of the upper running filter medium such as filter cloth is less, and the life can be expected to be longer than the conventional single filter cloth. The frequency of replacing the upper traveling filter medium is greatly reduced. The performance improvement of the belt-type filtration concentrator can be converted to a reduction in the amount of the polymer flocculant added and a reduction in the length of the concentrator.

  The belt-type filtration concentrator according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a side view of the belt-type filtration concentrator, and a tension roll in which an endless upper traveling filter medium 1 is disposed before and after a frame 2. 3 and the drive roll 4, and the upper surface of the upper traveling filter medium 1 is used as a filtration surface 1a. A filter cloth tensioning device 5 is connected to the tension roll 3 and a driving device 6 is linked to the driving roll 4. FIG. 2 is a plan view of the belt-type filtration concentrator. The mud supply trough 7 is provided on the filtration surface 1a on the starting end side of the upper traveling filter medium 1, and the sludge is present on both sides of the filtration surface 1a immediately after the supply mud in the vicinity of the mud supply trough 7. Guide plates 8 and 8 are provided for preventing the overflow of the spillage, and a scraper 9 is provided on the upper traveling filter medium 1 wound around the drive roll 4. As shown in FIG. 1, a filtrate trough 10 is disposed in the vicinity of the back surface of the upper traveling filter medium 1 from which a large amount of filtrate is discharged at the beginning of sludge charging. A filter cloth meandering correction device 11 and a filter material cleaning device 12 are disposed on the inverted lower surface of the endless upper traveling filter medium 1, and a general drainage trough 13 for receiving the filtrate and cleaning waste water is disposed below the filter cloth meandering correction device 11. It is set up. The upper traveling filter medium 1 wound around the tension roll 3 and the drive roll 4 shown in FIG. 1 and FIG. 2 is constituted by a filter cloth such as plain weave, twill weave and double weave having a capillary water absorption function, or a net conveyor belt wire mesh. It is. The filter cloth and the net conveyor belt wire mesh are excellent in the water absorption function of the capillary tube, have good cleaning properties and bend flexibility, and are suitable for driving the belt. If the upper traveling filter medium 1 is constituted by a filter cloth, the sludge solids recovery rate is high, and a large amount of filtrate received in the filtrate trough 10 at the beginning of sludge charging can be used as a filter medium cleaning liquid.

  As shown in FIGS. 1 and 2, a lower fixed filter medium 14 that slidably supports the filtration surface 1 a of the upper traveling filter medium 1 is disposed on the frame 2, and a composite in which the upper traveling filter medium 1 and the lower fixed filter medium 14 are combined. As a filter medium. FIG. 3 is a conceptual diagram showing the structure of the lower fixed filter medium, wherein the lower fixed filter medium 14 is a long elongated hole constituting member 15... It comprises a plurality of connecting support members 16... Which are fixedly attached to the lower surfaces of the constituent members 15. FIG. 4 is an enlarged view of a main part of the lower fixed filter medium, and is a long and narrow slot having a slot width S and a slot depth H between the slot members 15 and 15 arranged in parallel at a predetermined interval. A hole L is formed. In the embodiment of the present invention, the interval between the connecting support members 16... Is set in the range of 10 to 100 mm according to the size of the belt type concentrator.

  FIG. 5 is a conceptual diagram of another embodiment of the lower fixed filter medium constituted by the wedge wire. In the embodiment of the present invention, the lower fixed filter medium 17 is constituted by the wedge wire, and a plurality of parallel sectional views are reversed. It comprises a triangular long wire 18 and a plurality of connecting support members 19 attached to the lower surface of the wire 18 with a predetermined interval. FIG. 6 is an enlarged view of a main part of the lower fixed filter medium 17 composed of wedge wires, and a long wire hole La having a wire interval Sa and a wire height Ha is formed between the left and right wires 18 and 18. is there. If the lower fixed filter medium 17 is composed of a wedge wire, the long wire hole La expands from the sliding contact surface side of the upper traveling filter medium 1 to the filtrate discharge side, and the characteristic that the metal filter medium is difficult to clog is reinforced. . Further, the lower fixed filter medium 17 may be constituted by a parallel wire mesh in which elongated holes penetrating in the thickness direction are formed, and is a filter medium having a drainage function (drainage function).

  The filter holes of the lower fixed filter media 14 and 17 shown in FIGS. 3 and 5 are elongated holes L and La that penetrate in the thickness direction, so that the filter media has a drainage function (drainage function), and clogging due to stagnation of solid matter is Water permeability can be ensured without progressing, and it becomes a filter medium function that can be used for a long time without causing a decrease in concentration performance. Since the filtration surface 1a of the upper traveling filter medium 1 to which the sludge is supplied is slidably supported by the lower fixed filter mediums 14 and 17, the surface pressure of the upper traveling filter medium 1 is reduced, and wear due to the dripping of the upper traveling filter medium 1 is eliminated. The upper traveling filter medium 1 is always lubricated with the filtrate, and the elongated holes L and La of the lower fixed filter mediums 14 and 17 are arranged along the traveling direction of the upper traveling filter medium 1, so that the upper traveling filter medium is less worn by the sliding contact support. 1 strength can be maintained. Due to the synergistic effect of the capillary water absorption function of the upper traveling filter medium 1 constituted by the filter cloth or the net conveyor belt wire mesh and the drainage function of the lower fixed filter media 14 and 17 of the wedge wire or the parallel wire mesh, the capillary water absorption action and the drainage action are exhibited, Even in low-concentration sludge that requires discharge of a large amount of filtrate, good concentration performance can be secured, and an appropriate sludge concentration and solids recovery rate can be obtained. Life expectancy can be expected more than conventional single filter cloth, and exchange of filter media is greatly reduced. The lower fixed filter media 14 and 17 that are relatively heavy are also used in a fixed state and do not need to be replaced.

  FIG. 7 is a conceptual diagram of a belt type filtration concentrator in which an upper traveling filter medium and a lower fixed filter medium are arranged, and lower fixed filter mediums 14 and 17 that are slidably supported on the filtration surface 1a of the upper traveling filter medium 1 stretched endlessly. The above-mentioned composite filter medium is set as an ascending gradient with an inclination angle α toward the traveling direction of the upper traveling filter medium 1. Unlike conventional belt-type concentrators with a slope whose slope effect depends on the belt speed, the slope can be set independently regardless of the belt speed.

The lower fixed filter media 14 and 17 slidably supported by the filtration surface 1a of the upper running filter media 1 are simply combined with the capillary water absorption function of the upper running filter media 1 and the drainage function of the lower fixed filter media 14 and 17 slidably supported. In addition, the filtrate flowing quickly through the gaps between the elongated holes L and La of the inclined lower fixed filter media 14 and 17 applies a negative pressure to the upper traveling filter media 1 to enhance the discharge function, and the upper running filter media 1 has a capillary water absorption function and Further amplifies the drainage function. The filtrate discharged from the upper traveling filter medium 1 toward the lower fixed filter mediums 14 and 17 flows along the inclined surfaces of the lower fixed filter mediums 14 and 17 and is connected to the back surfaces of the lower fixed filter mediums 14 and 17 that support the upper traveling filter medium 1. The support members 16 and 19 are shaped like a weir plate substantially orthogonal to the traveling direction of the upper traveling filter medium 1 and are removed from the lower fixed filter mediums 14 and 17 at appropriate intervals. The filtrate is accumulated in the elongated holes L and La of the lower fixed filter media 14 and 17 so that the drainage from the upper traveling filter media 1 to the lower fixed filter media 14 and 17 is not hindered and becomes an effective drainage material. Can be eliminated. High concentration performance that cannot be achieved with conventional single filter media is expressed, and a high solids recovery rate is obtained.

FIG. 8 is a conceptual diagram of another embodiment in which the lower fixed filter medium is divided, and the filtration surface 1a of the upper traveling filter medium 1 is placed in the input concentration zone A immediately after the mud supply with the lower fixed filter medium 14 removed, and a plurality of It is divided into a concentration zone B slidably supported by the divided fixed filter media 14a, 14b, and 14c. The lower fixed filter medium 14 is not brought into sliding contact with the input concentration zone A immediately after the sludge is input, and the upper running filter medium 1 is separated by gravity. In the input concentration zone A, the resistance of the discharged filtrate is small, and a large amount of filtrate can be discharged. In the charging concentration zone A, due to the slight bending action of the upper traveling filter medium 1, the sludge reservoir in the initial charging stage is deepened, the concentration pressure is increased, the concentration time is increased, and the concentration action can be enhanced. In the embodiment of the present invention, the concentration zone B is divided into the _first concentration period B ₁ , the _second concentration period B ₂ , and the _second concentration period B ₃ , and the divided fixed filter media 14 a, 14 b, 14 c are divided into the filtration surface 1 a of the upper traveling filter media 1. It is slidably supported. The slender pore width S of the split fixed filter media 14a, 14b, and 14c is set larger in the sludge concentration first term B ₁ where drainage and drainage functions are required, and the capillary water absorption capability is required in the middle concentration B ₂ than the drainage capability. Therefore, it is relatively small compared to the enrichment _first period B ₁ , and the later enrichment period B ₃ is further reduced.

As shown in FIG. 8, a predetermined gap D is provided between the divided fixed filter media 14 a, 14 b, 14 c in the concentration zone B that supports the inclined upper traveling filter media 1. By discharging the filtrate from the gap D at the inclined lower end of the divided fixed filter media 14a, 14b, and 14c, the filtrate flowing along the filter media is divided and the draining function is improved. The lower fixed filter medium 14 is relatively heavy. If the lower fixed filter medium 14 is divided, the divided fixed filter mediums 14a, 14b, and 14c can be easily processed, and can be assembled in a divided form even in the initial assembly. There is no hindrance in work due to weight. In the embodiment of the present invention, there are three sets of divided fixed filter media 14a, 14b and 14c. Depending on the progress of the concentration of the belt type concentrator, the _first concentration period B ₁ , the middle concentration period B ₂ and the _second concentration period B It is possible to appropriately increase the divided fixed filter media 14a, 14b, and 14c disposed in ₃ .

FIG. 9 is a conceptual diagram of another embodiment of the lower fixed filter medium, in which the lower fixed filter medium 17 composed of a wedge wire is divided, and a plurality of divided fixed filter mediums 17a, 17b, and 17c are concentrated in the concentration zone B ₁ in the concentration zone, They are arranged in the middle concentration period B ₂ and the latter concentration period B ₃ . The wedge wire uses a wedge wire with a wire width W of 0.8 mm and a wire height Ha of 2 mm, and the wire interval Sa of the lower fixed filter medium 17 can be appropriately set according to the treatment capacity and sludge properties. fixed filter media 17a, 17b, the wire interval Sa of 17c, concentrated year B ₁ in the range of 0.2 to 20 mm, concentrated metaphase B _2, are sequentially reduced opening in the order of concentrating the late B _3. If the appropriate wire interval Sa is set according to the amount of the filtrate to be discharged and the capillary water absorption function, the concentration performance is improved by increasing the capillary water absorption action and decreasing the water content. Between the divided fixed filter media 17a, 17b, and 17c before and after the concentration zone B, a gap Da of 5 to 30 mm is provided. The lower fixing member 17 that slidably supports the upper traveling filter medium 1 has the divided wedge wires 17a, 17b, and 17c arranged continuously in the traveling direction of the upper traveling filter medium 1, and the entire filtration surface 1a is covered with the wedge wire. Since it is supported by 17a, 17b, and 17c, the surface pressure is small and the wire interval Sa is as narrow as 0.2 to 20 mm, so there is no bending due to the dripping of the upper traveling filter medium 1. Since the wedge wires 17a, 17b, and 17c are always lubricated by the filtrate, the upper traveling filter medium 1 is less worn, and the upper traveling filter medium 1 such as a filter cloth can be expected to have a longer life than a conventional single filter cloth.

As shown in FIG. 7, if a reciprocating cleaning device 20 is provided in the vicinity of the back surface of the lower fixed filter media 14 and 17, sludge adheres to the lower fixed filter media 14 and 17 and the lower fixed filter media is fixed when the drainage function is lowered. The clogging of the filter media 14 and 17 can be eliminated. If a filter cloth is used for the upper traveling filter medium 1, it becomes a clear filtrate due to the high solids recovery rate and high washability of the filter cloth. Is no longer necessary. And if the lower fixed filter medium 17 is comprised with a wedge wire, since it wash | cleans from the slit hole by the side of expansion, clogging will become easy to cancel. 7 and 8, when the divided fixed filter media 14a, 14b, 14c, 17a, 17b, and 17c disposed only in the concentration zone B are washed, the supply of sludge is stopped while the upper travel filter media 1 is running. However, if it starts from the discharge side of the upper traveling filter medium 1, in the input concentration zone A where the filtrate discharge amount is large immediately after input near the mud supply trough 7, while the cleaning device 20 approaches the sludge input side, the concentration previous period B ₁ A large amount of the filtrate is discharged, and the filtrate discharged from the upper traveling filter medium 1 does not become an obstacle to the filter medium washing water and can be washed during operation. The entire back surface of the lower fixed filter mediums 14 and 17 can be cleaned at high speed, and the filter medium function is maintained and can be used semipermanently.

FIG. 10 is a flowchart of a belt-type concentrator using a composite filter medium. In the concentration zone B of the upper traveling filter medium 1 made of filter cloth shown in FIG. 8, a split fixed filter medium 17a made of wedge wire shown in FIG. A processing flow of the belt type concentrator for slidingly supporting 17b and 17c will be described. As shown in FIG. 10, agglomerated sludge to which flocs are generated by adding a polymer flocculant is supplied from the mud supply trough 7 to the input concentration zone A of the upper traveling filter medium 1. In the charging concentration zone A, due to the slight curving action of the upper traveling filter medium 1, the sludge reservoir in the initial charging stage is deepened, the concentration pressure is increased, the concentration time is increased, and the concentration action is enhanced. A filtrate trough 10 is arranged below the concentration zone A of the upper traveling filter medium 1 and the concentration period B ₁ of the concentration zone B, and the filtrate separated by the upper traveling filter medium 1 is stored in the washing water tank 21. To do. The filter cloth of the upper traveling filter medium 1 has a high sludge solids recovery rate, and the filtrate separated by the filter cloth has a high clarity and can be used as a cleaning liquid. The concentrated sludge from which the filtrate has been separated in a large amount from the input concentration zone A is transferred to the concentration first period B ₁ of the concentration zone B, and is transferred to the concentration middle period B ₂ and the concentration latter period B ₃ while separating the filtrate.

As shown in FIG. 10, on the upper traveling filter medium 1 that is slidably supported by the divided fixed filter media 17 a, 17 b, and 17 c in the concentration zone B, the filtrate absorbed by the capillary action from the sludge passes through the upper traveling filter medium 1. The filtrate that has been absorbed by the capillary action between the route drained to the divided fixed filter media 17a, 17b, and 17c and the gap between the upper traveling filter media 1 and the divided fixed filter media 17a, 17b, and 17c is divided into the divided fixed filter media 17a, 17b, and 17c. A route that drains to And on the divided fixed filter media 17a, 17b, 17c side, the filtrate flows in the direction of gravity along the side of the wire 18 and the route that flows in the inclined downstream direction along the wire hole La of the divided fixed filter media 17a, 17b, 17c. Generate a route. The route flowing in the inclined downstream direction along the wire hole La is a straight groove-like flow path having a gradient free of obstacles, and excess filtrate is discharged along the route flowing in the gravity direction along the side surface of the wire. . In addition, the route that flows in the direction of gravity along the side surface of the wire 18 has no resistance because the wire hole La of the divided fixed filter media 17a, 17b, and 17c is expanded, and the wire width W has an acute angle at the lowermost end. Since the surface tension of the filtrate is released, it drops. Even if the amount of filtrate decreases, the filtrate is not retained in the wire hole La by surface tension. The filtrate that flows quickly through the gaps between the wire holes La of the inclined lower fixed filter medium 17a further amplifies the capillary water absorption function and the drainage function of the upper traveling filter medium 1. Furthermore, the connection support member 19 that supports the wires 18... Of the divided fixed filter media 17a, 17b, and 17c is substantially perpendicular to the traveling direction of the upper traveling filter media 1 to form a weir plate, thereby eliminating the filtrate. The filtrate is accumulated in the wire holes La ... of the divided fixed filter media 17a, 17b, 17c, and does not hinder the discharge from the upper traveling filter media 1 to the divided fixed filter media 17a, 17b, 17c, and becomes a draining material. Efficient filtration. As it is transferred to the middle concentration stage B ₂ and the latter concentration stage B ₃ of the concentration zone B, a high concentration performance that cannot be achieved by a conventional single filter medium is expressed, and a high solids recovery rate is obtained.

  Next, the concentrated sludge having passed through the concentration zone and having a high concentration is peeled off by the scraper 9 from the upper traveling filter medium 1 that is reversed along the drive roll 4. The traveling filter medium cleaning nozzle 12a is provided opposite to the upper traveling filter medium 1 from which the concentrated sludge has been peeled off, and the filtrate is supplied from the traveling filter medium cleaning pump 22 connected to the cleaning water tank 21 to the traveling filter medium cleaning nozzle 12a. Wash 1 filter cloth. Since the filter cloth is a single fiber fabric, it is easy to clean. The meandering correction roll 11a is in contact with the cleaned upper running filter medium 1, and after the skew of the meandering upper running filter medium 1 is corrected and wound around the tension roll, it is transferred to the filtration surface 1a again. A fixed filter medium cleaning nozzle 20a is disposed near the lower part of the divided fixed filter mediums 17a, 17b, and 17c, and a filtrate is supplied to the fixed filter medium cleaning nozzle 20a from a fixed filter medium cleaning pump 23 connected to the cleaning water tank 21. The fixed filter media 17a, 17b, and 17c are washed. Since the wedge wires of the split fixed filter media 17a, 17b, and 17c are washed from the wire hole La on the widening side where the wire hole La expands from the sliding contact surface side of the upper traveling filter media 1 to the filtrate discharge side, clogging is eliminated. Becomes easy.

  Belt type concentrators using filter cloth have been put into practical use for a long time, and there are models dedicated to concentration, but they are also used in combination with belt press concentration zones. Filter cloth has various options such as material, aperture ratio, air permeability, mesh opening, strength, and weaving, and is used in many belt-type concentrators because it is lightweight and inexpensive. In recent years, a wire mesh is sometimes used for a concentrator, but there are advantages and disadvantages. Therefore, the characteristics and defects of the filter media used in the conventional solid-liquid separator were investigated. As the filter medium, a woven filter cloth, a wire mesh, a nonwoven fabric, a metal filter medium, and a composite filter medium in which the filter cloth and the metal filter medium are combined were used. When used as a belt filter medium in a horizontal posture, basic tests were conducted on the capillary water absorption function, draining function (drainage function), recovery rate, clogging detergency, and bending flexibility, and consideration was given including experience values. The evaluation was conducted based on the analysis of the structure and physical properties and the results of the concentration test. The capillary water absorption function of the filter medium is a draining function (drainage function) of the filter medium and a set action, and both actions are restricted by the smaller ability. Table 1 is an evaluation table of filter media types for which characteristics and defects are compared and examined.

(1) Filter cloth (plain weave, twill, double weave, etc.)
The filter cloth used in the conventional belt-type concentrators places importance on ensuring a certain recovery rate, and generally has a small mesh opening, and the capillary water absorption performance is sufficient. There are some difficulties in draining the filtrate. There is no problem in peelability, and the recovery rate is high. Moreover, since it is a monofilament fabric, it is easy to clean. Flexibility is good and suitable for belt drive. The strength of the fiber is not as strong as that of a metal, and the life of a filter medium is not as long as that of a wire mesh due to wear due to sliding in a conventional plow.
(2) Wire / woven mesh (plain weave, twill, etc.)
Metal meshes and woven meshes such as plain weave and twill weave have the same function as filter cloth except for flexibility, but the flexibility is remarkably inferior to run a belt of metal mesh and woven mesh, which is a fatal defect.
(3) Wire mesh / net conveyor belt (coarse mesh ribbon network)
The wire mesh that has been put to practical use is a heribbon net, which has a wide mesh width and a ribbon diameter of about 1 mm, and has a rough and rough surface, so that the filtrate turbidity increases and the recovery rate deteriorates. When scraping with a scraping device or a discharge scraper, the sludge tends to bite into the recesses and remain so that the turbidity of the washing wastewater becomes high and the recovery rate further deteriorates. In addition, the metal mesh of the ribbon is composed of upper and lower layers, and SS particles of sludge that have entered between the upper and lower layers are difficult to remove by low water pressure cleaning, and careful cleaning from the top and bottom is necessary. May progress. In general, the life of the wire mesh is longer than that of the filter cloth, but the cost is higher than that of the filter cloth. In addition, since the weight is heavy, work using a heavy machine is required when the belt width is widened. Since the woven wire net of the heribbon net is a knitting method developed for a net conveyor, it has good bending flexibility and is suitable for driving a belt.
(4) Non-woven fabric Non-woven fabric has very high capillary water absorption performance, but conversely has no drainage function, and clogging and cleaning problems are fatal defects.
(5) Wedge wire The wedge wire has a shape in which the filter medium slit is expanded to the drainage side and has a fundamentally excellent drainage function, and is generally employed as a screen with good cleaning properties. If the width of the mesh is narrowed, the capillary water absorption performance is also improved, but the aperture ratio is reduced, the discharge function is lowered, and the practical treatment amount is not satisfied. If the width of the mesh is relatively wide, the drainage draining function is excellent, but the capillary water absorption performance is inferior, so it is difficult to concentrate at a high concentration, and a large amount of sludge escapes into the filtrate, so the recovery rate deteriorates and cannot be put to practical use. . There is no flexibility and the belt cannot run.
(6) Punching metal Punching metal can be used in the form of a bent belt if it is made of an extremely thin plate, but round holes with a small hole diameter are considerably inferior to other filter media in capillary water absorption and discharge performance due to surface tension.
(7) Punching metal and filter cloth composite filter medium When the punching metal is combined with the lower fixed filter medium and the filter cloth is combined with the upper traveling filter medium, the disadvantage of the punched metal capillaries that are significantly inferior to other filter media is the obstacle. , Capillary water absorption function of filter cloth is not demonstrated.
(8) Wedge wire and filter cloth composite filter medium Combining a wedge wire with the lower fixed filter medium and a filter cloth with the upper traveling filter medium is a weakness of the filter cloth due to the synergistic effect of the capillary water absorption function of the filter cloth and the drainage function of the wedge wire. The drainage performance is eliminated by the wedge wire, and the recovery rate that was a weak point of the wedge wire is eliminated by the capillary water absorption action of the filter cloth. A strong capillary water-absorbing action and draining action were exhibited, good concentration performance was ensured, and a high recovery rate was obtained. If the wedge wire is fixed, it does not need to be flexible, and if only a filter cloth with good bending flexibility is run, it is a filter medium with excellent peelability and good cleaning properties. From the basic test, it was confirmed that a filter medium without defects can be derived by combining a wedge wire and a filter cloth.

  From the results of the basic test, it was found that the combination of the wedge wire and the filter cloth in a horizontal posture eliminates the disadvantages of capillary water absorption and drainage, but the concentration performance is greatly improved by further increasing the slope. The reason is that each action synergistically increases due to the climbing gradient, and an obvious flow gradient, which may be small, is extremely effective. The minimum gentle gradient from which water naturally flows is called a water gradient. However, it is necessary to suppress the slope as much as possible and to prevent water from being accumulated. From these empirical values and general calculation formulas, the angle, water gradient, and level difference of the filtration surface can be derived. The results are shown in Table 2.

Therefore, at the Kashiwa Purification Center, a verification test was conducted using a belt-type filtration concentrator on the relationship between the presence or absence of the belt inclination angle and the concentration. The belt-type filtration concentrator used a composite filter medium in which a filter cloth having a width of 500 mm × effective length of 3000 mm and a wedge wire was used, and the filter medium traveling speed was set to 10 m / min. The supplied sludge is 0.25% (vs. TS) of polymer flocculant added to surplus sludge with a TS concentration of 0.72% and an SS concentration of 0.46%, and this agglomerated sludge is supplied at 250 L / min. Concentrated sludge concentration was investigated for the cases where the angle of inclination of 0 degrees and 2 degrees. The relationship between the presence / absence of the inclination angle of the belt of the composite filter medium and the concentrated concentration is shown in Table 3.

  In the concentration zone in front of the belt press dehydrator, the belt concentration of the filter cloth alone is adopted, but there is a knowledge that the concentration increases when the inclination angle is increased. This is to prevent the filtrate from being accompanied by the filter medium by making the inclination angle of the climbing gradient in the traveling direction of the filter cloth, so that it is difficult to be conveyed to the concentrated sludge discharge side. In the case of a belt press with a belt speed of about 1 m / min, this action is effective at a relatively small inclination angle of about 5 degrees. However, with belt concentration, the belt speed is generally as high as 10 to 40 m / min. Therefore, the effect is small unless a considerably large inclination angle of 10 to 15 degrees is provided. However, if a large angle of 10 degrees or more is set, the level on the concentrated sludge discharge side becomes high, and the overall height of the apparatus becomes high, which is not preferable. For example, when the distance between the driving roll and the tension roll of the filter cloth belt is 3000 mm, the height becomes about 500 to 800 mm at an inclination angle of 10 to 15 degrees. Furthermore, it is not preferable to provide a large inclination angle of 10 degrees or more because the driving power for running the filter cloth increases.

    In order to reduce the overall height of the device and reduce the driving power for running the filter cloth, the inclination angle should be as small as possible. In the general water gradient angle shown in Table 2, the floor of the bathroom or balcony is usually 1/100 to 1/50 so as to suppress the inclination as much as possible and to prevent the accumulation of water. In case of drainage and when the slope does not matter so much, the slope is increased to about 1/20. Further, considering that there is a slight undulation on the surface of the fixed filter medium such as a wedge wire and the climbing gradient is locally reduced, the inclination angle is set to about 2 degrees and the gradient is set to about 1/30. As an example, when the distance between the driving roll and the tension roll of the filter cloth belt is 3000 mm, the total height is only about 100 mm higher if the inclination angle of the filter cloth belt is 2 degrees.

  A comparative basic test was carried out for each filter medium type with respect to the capillary water absorption function, draining function (drainage function), recovery rate and clogging detergency when the tilt angle was set to 2 degrees. The experimental results are shown in Table 4. By combining the slope of the climbing slope, the composite filter medium with the combination of wedge wire and filter cloth has a stronger capacity to absorb capillary water and drainage drainage synergistically than the other filter media. Express concentration function. In addition, the single filter medium increased the draining function (drainage function) of the wedge wire. Other filter media also showed an improvement in concentration performance due to the gradient effect, but these were small. In the case of wedge wire + filter cloth + inclination, the effect of increasing the rise was greater than the inclination effect of other filter media. In the composite filter medium of the wedge wire and the filter cloth, the lower fixed filter medium does not travel, so that it is possible to prevent the entrainment of the filtrate if there is a slight inclination angle regardless of the speed of the travel filter medium. Unlike a conventional belt-type concentrator with a slope, in which the effect of the slope is influenced by the belt speed, the lower fixed filter medium can set the slope independently regardless of the belt speed.

FIGS. 11 and 12 are conceptual diagrams showing the state of filtrate discharge of a composite filter medium in which a filter cloth and a wedge wire are combined. When the flow of the filtrate is observed, the flow rate of the filtrate flowing through the inclined wire gap is fast. In the input concentration zone where the amount of filtrate discharged is large, the filtrate falls by being blocked by the rod that supports the wire of the wedge wire. It is presumed that the filtrate flowing through the wire gap exerts a negative pressure on the filter cloth and enhances the discharge function. Fig. 13 shows the concentration mechanism of the composite filter medium based on the best combination of wedge wire and filter cloth based on the data of comparative basic tests of various filter media. On the filter cloth side, the filtrate absorbed by the upper sludge by the capillary action is applied to the filter cloth. A route [a] that penetrates and drains to the wedge wire side and a route [b] that drains the filtrate absorbed by the capillary action in the gap between the filter cloth and the wedge wire are generated. In any case, the capillary water absorption action is large, but the drainage action is slightly inferior. In addition, the route of [b] is not expressed by filter cloth alone. On the wedge wire side, the filtrate flows along the longitudinal direction of the wedge wire in the inclined downstream direction [c] and the route in which the filtrate flows in the gravity direction along the side surface of the wire [
d]. The route [c] is a straight groove-like flow path having no obstacle having a gradient, and excess filtrate is discharged along the route [d] flowing in the direction of gravity along the side surface of the wire. Since [d] flows in the direction in which the wire interval widens, there is no resistance, and the wire width is dripped after the surface tension of the filtrate is released because the lower end has an acute angle. Even if the amount of filtrate decreases, the filtrate is not held between the wedge wires by surface tension. In both cases, the drainage action is large, but the capillary water absorption action is slightly inferior. Not only is the capillary water absorption function of the filter cloth combined with the drainage function of the wedge wire, but the high drainage action of the wedge wire that appears in the route [c] [d] causes the filtration of the route [a] [b]. In order to further amplify the capillary water-absorbing function and drainage function of the cloth, high concentration performance that cannot be achieved by a single filter medium appears. Table 5 shows the outflow route, the capillary water absorption function, and the drainage function of the filtrate of the composite filter medium in which the wedge wire and the filter cloth are combined.

  Next, the concentration performance of a single filter medium of conventional wire mesh and filter cloth, and a composite filter medium combining filter cloth and wedge wire was investigated. The belt type filtration concentrator used for the test uses a tester with a width of 500 mm and an effective length of 3000 mm, and a polymer flocculant is added to the sewage surplus sludge collected from the dredged sewage treatment plant with a 0.5% sludge concentration. 0.2% was added, and the concentration performance was investigated at a filter medium traveling speed of 10 m / min for each filter medium type. Table 6 shows the operating conditions of the belt type filtration concentrator.

Based on the operating conditions in Table 6, the concentration (%), solids recovery rate (%), and filtrate turbidity (mg / L) with respect to the throughput (m ³ / m · h) for each composite filter medium and single filter medium The performance was investigated. Table 7 shows the experimental results of the concentration performance for each filter medium type. In addition, the numerical value in a parenthesis shows the case where the inclination angle is 0 degree. When applying the composite filter media belt type filter concentrator to sewage sludge, the initial sedimentation sludge has a good sedimentation concentration, so it is concentrated by the conventional gravity concentration method and applied to the process of forcibly concentrating excess sludge with poor sedimentation. About 20m ³ per hour / belt width is the standard performance of conventional machines using wire mesh or filter cloth, but the concentration of filter cloth + wedge wire can be increased by 50%, even if 30m ³ per hour / belt width is increased. Is improved by about 0.5 to 0.6 points. Table 8 is a comparison table of the concentrated concentration experiment results for each type of inclination angle of 2 degrees and inclination angle of 0 degrees. Regarding the filtrate turbidity and solids recovery rate, the improvement from the wire mesh is large, and the results are slightly better than the filter cloth. Even with an inclination angle of 0 degree (horizontal position), a composite filter medium can handle a throughput of 30 m ³ / m · h, but the final concentration is the same as that of a filter cloth with a throughput of 20 m ³ / m · h and an inclination angle of 2 degrees alone. .4%, which is 0.5 points inferior to 4.9% of the composite filter medium at an inclination angle of 2 degrees. Table 9 is a comparison table of the experimental results of the recovery rate for each type of the inclination angle of 2 degrees and the inclination angle of 0 degrees.

  The belt type filtration concentrator according to the present invention is a composite filter medium combining an upper traveling filter medium having a capillary water absorption function and a lower fixed filter medium having an excellent drainage function, and the filtration surface is slightly inclined upward in the traveling direction of the upper traveling filter medium. As a result, a large amount of filtrate can be discharged due to the synergistic effect of capillary water absorption and drainage, and concentration concentration and throughput can be improved, while maintaining good recoverability and washability of the filtrate. It becomes a belt-type filtration concentrator that demonstrates the concentration function. And it becomes possible to convert the performance improvement of a belt type filtration concentrator into the reduction of the addition amount of a polymer flocculant and the shortening of the length of a concentrator. Therefore, it is optimal for use in a belt-type filtration concentrator that concentrates sludge such as excess sludge, mixed raw sludge, digested sludge, or OD excess sludge.

It is a side view of the belt type filtration concentration machine concerning this invention. Similarly, it is a top view of a belt type filtration concentrator. Similarly, it is a conceptual diagram which shows the structure of a lower fixed filter medium. Similarly, it is a principal part enlarged view of a lower fixed filter medium. Similarly, it is the conceptual diagram of the other Example of the lower fixed filter medium comprised with the wedge wire. Similarly, it is a principal part enlarged view of the lower fixed filter medium comprised with the wedge wire. Similarly, it is a conceptual diagram of a belt-type filtration concentrator in which an upper traveling filter medium and a lower fixed filter medium are arranged. Similarly, it is the conceptual diagram of the other Example which divides | segments a lower fixed filter medium. Similarly, it is a conceptual diagram of the other Example of a lower fixed filter medium. Similarly, it is a flowchart of a belt type concentrator using a composite filter medium. Similarly, it is the conceptual diagram which shows the condition of the filtrate discharge | emission of the composite filter medium which combined the filter cloth and the wedge wire. Similarly, it is the conceptual diagram which shows the filtrate discharge | emission state of the composite filter medium which combined the filter cloth and the wedge wire. Similarly, it is a concentration mechanism of a composite filter medium by a combination of a wedge wire and a filter cloth.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper traveling filter medium 1a Filtration surface 14, 17 Lower fixed filter medium 14a, 14b, 14c, 17a, 17b, 17c Split fixed filter medium 15 Slot member 18 Wire 16, 19 Connection support member 20 Cleaning device A Input concentration zone B Concentration zone L Elongated hole La Wire hole B ₁ Early period B ₂ Middle stage B ₃ Late stage D, Da Gap α Inclination angle

Claims (9)

  In a concentrator that hangs an endless belt between rolls and feeds sludge to the filtration surface of the endless belt for solid-liquid separation, a woven cloth-like upper running filter medium (1) with a capillary water absorption function is stretched. The upper traveling filter medium (1) has a filtration surface (1a) slidably supported on the lower fixed filter medium (14, 17), and the lower fixed filter medium (14, 17) has an elongated slot (L, A belt-type filtration concentrator characterized in that La) is formed in the traveling direction of the upper traveling filter medium (1).   The belt-type filtration according to claim 1, wherein the upper traveling filter medium (1) is constituted by a filter cloth or a net conveyor belt wire mesh, and the lower fixed filter medium (14, 17) is constituted by a wedge wire or a parallel wire mesh. Concentrator.   The upper traveling filter medium (1) has a slope (α) of an ascending slope formed on the filtration surface (1a) of the upper traveling filter medium (1) and the lower fixed filter medium (14, 17) that slidably supports the upper traveling filter medium (1). The belt type filtration concentrator according to claim 1 or 2.   The lower fixed filter medium (14, 17) is divided, and the elongated holes (L, La,...) Of the divided fixed filter medium (14a, 14b, 14c, 17a, 17b, 17c) are moved in the traveling direction of the upper traveling filter medium (1). The belt-type filtration concentrator according to any one of claims 1 to 3, wherein the belt-type filtration concentrator is further reduced in size.   The elongated hole width (S) and wire interval (Sa) of a plurality of divided fixed filter media (14a, 14b, 14c, 17a, 17b, 17c) for slidingly supporting the filtration surface (1a) of the upper traveling filter media (1). The belt-type filtration concentrator according to claim 4, wherein the belt-type filter concentrator is successively reduced and opened in a range of 0.2 to 20 mm in the traveling direction of the upper traveling filter medium (1). The filtration surface (1a) of the upper traveling filter medium (1) is set to the input concentration zone (A) immediately after mud supply and the concentration zone (B) for sludge concentration, and the lower fixed filter medium (14, 17) is divided. The belt-type filtration concentrator according to any one of claims 1 to 5, wherein a plurality of divided fixed filter media (14a, 14b, 14c, 17a, 17b, 17c) are arranged in the concentration zone (B). .
  A dam plate-like connection support member (16, 19) is disposed on the back surface of the elongated hole constituting member (15, 18) of the lower fixed filter medium (14, 17) in a direction crossing the upper traveling filter medium (1). The belt type filtration concentrator according to any one of claims 1 to 6. Between the divided fixed filter media (14a, 14b, 14c, 17a, 17b, 17c) before and after dividing the lower fixed filter media (14, 17 ) that slidably support the filtration surface (1a) of the upper traveling filter media (1). The belt type filtration concentrator according to any one of claims 5 to 7, wherein a predetermined gap (D, Da) is provided.
  The belt-type filtration concentrator according to any one of claims 1 to 8, wherein a cleaning device (20) is disposed on the back surface of the lower fixed filter medium (14, 17).

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