JPS6025597A - Electroosmotic-type dehydrator - Google Patents

Abstract

PURPOSE:To perform effective electroosmotic dehydration while providing a favorable current-passing property, by a method wherein a slurry sqeezing passage is defined between an anode-side electrode and a cathode-side electrode, and a slurry supplied is fed toward an outlet while impressing a voltage between the electrodes. CONSTITUTION:The slurry 10 such as a sludge supplied from a hopper 7 into the slurry squeezing passage 3 is fed toward the outlet side while being clamped between a press belt 1 and a filter belt 2. In the feeding prosess, electroosmosis by an electric field is effected in addition to the squeezing force, whereby dehydration proceeds. As the dehydration proceeds, the water content of the slurry 10 is lowered, electric resistance thereof is increased, and the volume thereof is reduced. In this case, since the passage gap between the belts 1, 2 is gradually reduced and the intensity of the electric field is gradually increased in the direction toward the outlet, a strong squeezing force and a strong electric field are applied from the belt side to the slurry 10 making close contact with the belts 1, 2, so that a favorable current-passing property is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to an electroosmotic dewatering machine for dewatering slurry such as sludge produced in a treatment process at a sewage treatment plant or human waste treatment plant.

[Prior art and its problems]

Due to the problem of environmental pollution, the sludge generated at the above treatment plant is not disposed of directly into rivers, etc., but instead is dehydrated and turned into a cake, then landfilled, incinerated, or composted for reuse as fertilizer. There is. In this case, if the water content of the sludge dewatered cake is 50 cm or less, natural incineration in an incinerator is possible, and the sludge water content can be easily adjusted in the composting process, so it is possible to use a dewatering machine. As for performance, the tentative goal is to reduce the moisture content of the cake after dehydration treatment to about 50 fibers.

However, the sludge, which is mainly composed of organic matter, has a strong bond with water and is difficult to dewater, and existing mechanical dehydrators use a blood-rich flocculant such as slaked lime to concentrate the sludge. However, the moisture content of the dehydrated cake is at most 60%, which is the dehydration limit, and it is said that it is practically difficult to increase the dehydration rate beyond that.0For this reason, electroosmosis is used as a measure to improve dehydration performance. Some dehydrators are now being developed. An example of this is to apply a voltage between the press belt and filter belt of an existing belt press dehydrator as opposed electrodes, and apply an electric field to the sludge supplied between the belts while applying mechanical squeezing force. A device that performs air infiltration dehydration is known.

Next, a conventional example of such an electroosmotic dehydrator is shown in FIG.

In the figure, 1.2 is a pair of left and right subrockets)
The frame is a press belt and a filter belt passed between la, lb and 2a, 2b, and both belts are arranged parallel to each other so as to face each other with a gap between them. A compression passage 3 is defined. Further, the filter belt 21 is driven in the direction of arrow A by a drive motor 4, and a reactor water receiving tray 5 is installed below the filter belt 21, which communicates with a drainage channel outside the system. On the other hand, each of the belts 1 and 2 is made of a conductive material so as to serve as a positive electrode, and the anode side of the n-source device 6 is connected to the press belt 1 via a sprocket.
The cathode side is connected and wired to the filter belt 2, respectively. The slurry squeezing passage 3 has an inlet at its left end and an outlet at its right end, with a slurry supply hopper 7 on the inlet side and a container 9 for receiving dewatered cake via a chute 8 on the outlet side.

In the above configuration, pressel) 1 and filter belt 2
If the high moisture content slurry 10 supplied from the hopper 7 is conveyed along the slurry squeezing passage 3 in the direction of arrow P by sandwiching it between the belts while applying a voltage between the belts,
In addition to the mechanical squeezing force, an electric field acts on the slurry 10, and the water in the slurry is positively charged and the filter belt 2 on the cathode side
It flows towards the direction of discharge, passes through the filter belt 2, drips into the reactor water tray 5, and is discharged outside the system.
So-called electroosmotic dehydration is performed. On the other hand, the dehydrated slurry is turned into a cake and becomes a dehydrated cake 10/ in the passage 3.
On the other hand, the filtration effect due to electroosmosis in the dehydration method described above depends on the strength of the electric field and the slurry, assuming the voltage applied between the electrodes is constant. The higher the conductivity of the slurry, the greater the effect.As shown in Fig. 1, the slurry 10 being conveyed through the slurry squeezing passage from the inlet to the outlet gradually becomes dehydrated during the conveyance process, and as a result, The moisture content of the slurry also changes. The water content of the slurry is high in the region close to the pick-up side and the current conductivity is high, but as it advances toward the exit side, the water content decreases and its electrical resistance increases, deteriorating the current conductivity. As a result, a sufficient dewatering effect cannot be obtained in the entire area of the slurry squeezing passage 3. Of course, it is possible to solve the problem to some extent by setting the applied voltage sufficiently high in advance, but this method increases power consumption and does not allow for economical operation.

As a solution to this problem, as shown in FIG. 2, a press belt that also serves as an anode side electrode is placed along the slurry squeezing passage 3 in multiple stages parallel to the belt filter 2 (Prespel IA).
Divided into IB, IC, each divided prespell) IA, I
B, different voltages Vl and V2 for each IC.
A system in which VB (Vl<V2<VB) is applied is conventionally known. According to this method, the applied voltage is set to decrease in stages according to the progress of dehydration, so the electric field is strengthened by compensating for the increase in electrical resistance that occurs as dehydration progresses, thereby reducing excess power consumption. However, in order to use the above method, the press belt must be independently divided into multiple parts, including the power supply circuit. However, the structure is complicated and the manufacturing cost is high. In addition, it was found through experiments that the expected dehydration performance could not be obtained with the above configuration. The main reasons for this are as follows.

That is, as the water content of the slurry decreases as dehydration progresses, its volume decreases. For this reason, the volume of the slurry conveyed sandwiched between the press belt and the filter belt, which are arranged in parallel, decreases as it approaches the outlet side, resulting in poor adhesion between the electrodes and the slurry. As a result, not only does the electrical conductivity of the slurry decrease, but also sufficient mechanical squeezing force is not applied, making it impossible to achieve the expected dewatering performance. [Object of the Invention] This invention has been made in view of the above points. However, without having to take complicated measures such as dividing the applied voltage as mentioned in the case of the conventional machine, the slurry can be effectively applied to the entire area of the slurry squeezing passage from the inlet to the outlet as dewatering progresses. An object of the present invention is to provide an electroosmotic dehydrator with high dewatering performance that is skillfully constructed so that electroosmotic action and mechanical squeezing force can be applied to slurry.

[Key points of the invention]

In order to achieve the above object, the present invention delivers slurry to a slurry squeezing passage defined between an anode side electrode and a cathode side electrode, and dehydrates the slurry by electroosmosis during the conveyance process within this passage. In this dewatering machine, the gap between the slurry pressing passages between opposing 75° poles is gradually reduced from the entrance to the exit of the passage, thereby compensating for the loss of slurry as dehydration progresses and reducing the volume of slurry throughout the passage. The chicken slurry is brought into close contact with the electrode to provide good electrical conductivity and strong squeezing force, thereby improving dewatering performance.

[Embodiments of the invention]

3, 4 and 5 each show a different embodiment of the invention. Of these, the embodiment shown in FIG. 3 is an embodiment of a belt press system in which a press belt 1 and a filter belt 2 similar to those shown in FIG. 1 are combined. It is connected to a conductive press belt 1 through a slurry pressing passage 3 on one cathode side.
The filter belt 2 is connected to an electrode plate 12 disposed in close contact with the back surface of the filter belt 2 along the filter belt 2 . Further, behind the slurry conveying area, opposite to the pressel 1, there is a hydraulic cylinder 13. A press device 15 is provided which presses the press 1 toward the passage 3 via an adjustment bolt 14 etc.
In such a configuration, according to the present invention, the press belt 1 is inclined relative to the filter belt 2 including the cathode side electrode 12, and the inclination is between the opposing surfaces of the press belt 1 and the filter belt 2. The passage gap D1 between the electrodes is set to be large on the entrance side of the defined slurry squeezing passage 3, and the passage gap D2 is set to be small on the exit side.

As a result, the passage 3 has a shape in which the width in the vertical direction gradually decreases from the inlet to the outlet. As a result, the potential gradient at each position in the slurry squeezing passage 3 and the strength of the stain field gradually increase from the inlet to the outlet.

According to the above structure, the slurry 10 such as sludge supplied from the hopper 7 to the slurry pressing passage 3 is sandwiched between the press belt 1 and the filter belt 2 and conveyed by the belt toward the outlet side. During this conveyance process, in addition to mechanical squeezing force, electroosmosis caused by an electric field acts, and dehydration progresses. In this case, as dehydration progresses, the water content of the slurry 10 decreases, increasing the electrical resistance and decreasing the volume, but on the other hand, the passage gap between the press belt 1 and the filter heating belt 2 As the electric field gradually decreases toward the exit, and the electric field strength gradually increases, the slurry compensates for the volume reduction and the increase in electrical resistance, and adheres tightly between belts 1 and 2, while being strong from the belt side. Good electrical conductivity is maintained by applying a strong squeezing force and a strong electric field. In this way, effective electroosmotic dewatering can be carried out over the entire stroke area of the slurry squeezing passage 3, and this makes it possible to dehydrate the slurry to a low water content that could not be achieved with the conventional machine.
Becomes Noh.

The embodiment shown in FIG. 4 uses a four-way rotary drum 16 as an anode side electrode in place of the press belt in the embodiment shown in FIG. A metal press conveyor 17 on the cathode side which is overlapped with 2 is disposed facing each other, and a slurry compression passage 3 is defined between the surfaces facing the rotating drum 16. The press conveyor 17 is stretched between sprockets 17a to 17d, and a press device 15 similar to that described in FIG. 3 is disposed on the back side facing the slurry squeezing passage area. In addition, the anode side of the power supply device 6 is connected to the rotating drum 1 via a brush.
The cathode side is connected to the rotating shaft 16a of the rotating drum 16.6, and the cathode side is connected to the tin rocket shaft of the press conveyor 17, respectively. Press conveyor 17 is anode.

A voltage is applied between both electrodes as the cathode side electrode. In this structure, the multi-rotating drum 16 and the arc region of the press belt 17 facing the multi-rotating drum 16 are relatively eccentrically opposed to each other, and the slurry squeezing passage 3 defined between them is The structure is such that the inter-electrode passage gap pi on the inlet side is large and the passage gap D2 on the outlet side is small. Therefore, as described in FIG. 3, a slurry squeezing passage 3 is defined in which the passage gap gradually decreases from pi to D2 from the inlet to the outlet. As a result, effective electroosmotic dewatering can be achieved in the entire range of the slurry squeezing passage 3 from the inlet to the outlet, similar to the embodiment shown in FIG.

The embodiment shown in FIG. 5 differs from the previous embodiments in that it does not use a belt. That is, in this embodiment, a conductive cylindrical body 18 with both ends open and a Chugi rotating shaft 19 inserted into the cylindrical body correspond to the electrodes on the anode side and the cathode side, respectively, and the slurry squeezing passage 3 is defined between the cylindrical body 18 and the outer periphery of the hollow rotating shaft 19. The cylindrical body 18 has its right end as an inlet, and a slurry supply hopper 7 made of an insulating material is connected thereto. A dehydrated cake separation guide 20 is installed opposite the left end outlet. The hollow rotating shaft 19 has a large number of reactor water permeation holes 19a formed on its circumferential surface to serve as a filter surface, and its inner space is used as a reactor water conveyance path to communicate with a drainage pipe 21 outside the system. ,
It is inserted through a bearing 22 along the axial center of the cylindrical body 18 , and its shaft end is conductively connected to the drive motor 4 through a reduction gear mechanism 23 . Furthermore, slurry conveying blades 24, which serve as screw blades, are attached to the outer periphery of the hollow rotating shaft 19.The cylindrical body 18 and the intermediate rotating shaft 19 are electrically insulated from each other, and are connected to the anode side of the power supply device 6, respectively. The cathode side is connected by wiring.

The slurry 10 is supplied from the hopper 7 to the slurry squeezing passage 3 inside the cylindrical body, and is pushed into the passage and conveyed toward the outlet by the rotational drive of the conveying blades 24. In this conveying process, the slurry is compressed along with the mechanical squeezing force. Electroosmotic dehydration is performed under the action of an electric field, and the water contained in the slurry that is positively charged and flows around the circumferential surface of the hollow rotating shaft 19, which is the cathode side electrode, is discharged to the rotating shaft 19 and then flows through the permeation hole 19a. The reactor water passes through and collects in the reactor water discharge path inside the shaft, from where it is discharged outside the system through the drain pipe 21.A reactor water suction pump is connected to the drain line outside the system as necessary. On the other hand, from the outlet of the passage 3, the dehydrated slurry cake 10' is discharged by the guide 20, with the direction changed from the axial direction to the radial direction. It has a tapered shaft structure with a small diameter and a large diameter at the left end, so that the passage gap between the electrodes and the cylindrical body 19 changes from the gap D1 on the inlet side to the gap D2 on the outlet side.
(DI)]) A slurry squeezing passage 3 is defined which gradually reduces to 2). Therefore, according to this embodiment,
Electroosmotic dehydration is effectively achieved in the same manner as in the previous embodiments.

Furthermore, according to the results of experiments in which samples such as digested sludge from a sewage treatment plant, mixed sludge, and sludge collected from a settling tank of a water treatment plant were dehydrated using the dehydrator shown in each of the above examples, It has been confirmed that the moisture content of the dehydrated cake can be reduced to 50% by weight. [Effects of the Invention] As described above, according to the present invention, the water content of the dehydrated cake can be reduced to 50 cm. By configuring the passage gap of the slurry pressing passage to gradually decrease from the passage entrance to the exit, the electrical resistance of the slurry increases and the volume of the slurry decreases as dehydration progresses during the conveyance process in the slurry pressing passage. The reduced volume can be reduced by the sleeve (It), and a sufficiently strong squeezing force and good electrical conductivity can be applied to the inner metal area of the passage to perform effective fishing force electroosmotic dewatering. like an electrode.

There is no need to take complicated measures such as dividing the applied voltage, and it is possible to provide an electroosmotic dewatering device with excellent dewatering performance suitable for dehydrating sludge generated in the above-mentioned sewage treatment plants, etc. .

[Brief explanation of the drawing]

FIGS. 1 and 2 are schematic diagrams of a conventional electroosmotic dehydrator, and FIGS. 3 to 5 are diagrams of different embodiments of the present invention. 1...Press belt, 2...Filter belt, 3...Sludge compression passage, 4...
Drive motor, 5...p water tray, 6...
Power supply device, 7... Slurry supply hopper, 10...
... Sludge, 10' ... Dehydrated cake, 16...
... Rotating tram, 17 ... Press conveyor, 18 ... Cylindrical body, 19 ... Hollow rotating shaft, 24 ... Slime conveying blade, P ...Transportation direction of the slurry in the passage, Dl... Passage gap on the passage entrance side, D2... Passage gap on the passage exit side

Claims (1)

[Claims] 1) A slurry squeezing passage is defined between an anode side electrode and a cathode side electrode that are arranged to face each other, and a voltage is applied between the electrodes while supplying the slurry to the entrance of the slurry squeezing passage. When the slurry is conveyed toward the outlet, the water contained in the slurry is collected by electroosmotic action to one electrode side, and from there it is separated and discharged out of the system through the offshore passage member. In the osmotic dehydrator,
An electroosmotic dewatering machine characterized in that the gap between the slurry squeezing passages between the opposing electrodes is gradually reduced from the entrance to the exit of the passage. 2. In the dewatering machine as set forth in claim 1, the slurry squeezing passage is defined between a press belt on the anode side and a filter belt on the cathode side that faces relatively inclined with respect to the press belt. 3) In the dehydrator according to claim 1, the slurry squeezing passage covers the rotating drum on the anode side and a part of the circumferential area of the rotating drum. An electroosmotic dewatering machine characterized in that it is defined between a press conveyor tonneau with a fill belt on the cathode side which is eccentrically wound around the cathode side. 4) In the dewatering machine according to claim 1, the slurry compression passage is defined by a cylindrical body on the anode side and an inner 11Cv5 water discharge passage with the peripheral surface as a filter surface, and is provided on the outer periphery thereof. An electroosmotic dehydrator characterized in that the slurry conveying blade is defined between the circumferential surface of a tapered hollow rotary shaft on the cathode side which is inserted into the cylindrical body.