JPS6068017A - Electroosmostic dehydrator - Google Patents

Abstract

PURPOSE:To reduce electric power consumption by performing predehydration simultaneously with electroosmotic dehydration by constructing an external cylinder constituted of a front half part with an insulating material and a hind half part with an electroconductive material and arranging conveying screw blades serving also as electrode to the inside of the external cylinder. CONSTITUTION:Sludge 80 is charged from a hopper 15 through an inlet 14 into an external cylinder 10. The sludge 80 moves toward an outlet 16 while being compressed and stirred by the screw blades 30. Since the front half part of the external cylinder 10 is a screen cylinder 11 constituted of an insulating material. The sludge is first dehydrated by the gravity of its own weight. The sludge is further dehydrated by compression by the transporting effect due to the screw blades 30; thus, predehydration is accomplished. The predehydrated sludge is then dehydrated by electroosmosis by being conveyed to the hind half part by the screw blades 30 between a cylinder 12 constituted of a conductive material as an anode and a rotary shaft 20 of the screw blades 30 as a cathode, both serving as counterelectrodes. Contained water is discharged to the outside of the dehydrator through perforated holes 21 on the rotary shaft 20, a conveying passage of filtrate in the shaft, and a water discharge pipe 60.

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 should not be disposed of directly into rivers, etc., but should be dehydrated and turned into a cake before being landfilled, incinerated, or composted to be reused as fertilizer. I have to. In this case, if the moisture content of the sludge dewatered cake is sufficiently low, natural incineration in an incinerator is possible, and the sludge moisture content can be easily adjusted in the composting process. However, the sludge, which is mainly composed of organic matter, has a strong bond with water and is difficult to dehydrate, and no matter how much coagulant is used for concentration treatment, the water content of the dehydrated cake is only about 60%. This is the limit, and it is said that it is practically difficult to increase the dehydration rate beyond this limit.

For this reason, some dehydrators using electroosmosis have been developed as a way to improve dehydration performance.One example is the use of the press belt and filter belt of an existing belt press type dehydrator as opposed electrodes. It is known that electroosmotic dewatering is performed by applying a voltage between the belts and applying an electric field while applying mechanical squeezing force to the sludge supplied between the belts. Although this dewatering method significantly improves the dewatering performance compared to a pure mechanical dehydrator, the sludge fed into the belt press is limited to pre-dewatered sludge that has been caked to some extent, with a water content of 90%. If the above-mentioned almost raw sludge is directly supplied, the sludge will leak sideways from the sludge passage between the belts during conveyance inside the machine, and the sludge loss will be extremely large, making it impractical. The opposite electrode of the electroosmotic part is a concentrically arranged tubular electrode, and electroosmosis is performed by sending slurry into the slurry passage defined between both electrodes, and the surface of the inner tubular electrode is used as a flood control permeable screen surface. An electroosmotic dehydrator configured to drain reactor water that has passed through the reactor to the outside of the system has already been proposed. Unlike a pre-emptive belt system, such a dewatering machine eliminates the risk of the slurry leaking sideways from the passageway during conveyance, so the highly fluid slurry with a high water content is input into the dewatering process. There are advantages to being able to do so.

On the other hand, however, in the method of dehydrating a slurry with a high moisture content to a dehydrated cake with a low moisture content all at once by electroosmosis, the amount of power required for this process is extremely high. That is, the first
The figure shows the relationship between the initial water content of the slurry and the amount of electricity consumed to dehydrate it to a water content of 55%, based on the inventor's experiment with electroosmotic dehydration. It is clear that the lower the initial moisture content of the slurry before electroosmotic dehydration, the less power consumption is required for the dehydration process. By performing pre-dehydration using a conventional method, power consumption in the electroosmosis section can be reduced. From the point of view of B, an attempt was made to install an independent gravity-type or compression-type pre-dehydrator upstream of an electroosmotic dehydrator and connect the two on a line to construct a slurry dewatering system. However, installing a pre-dehydrator separately from the electroosmotic dehydrator creates new problems such as an increase in equipment costs and equipment space including the means for transferring slurry between the dehydrators.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and it solves the conventional problems described above, and enables highly effective dehydration treatment by directly supplying slurry with a high water content, and the power consumption required for electroosmotic dehydration. It is an object of the present invention to provide an electroosmotic dehydrator which has a small amount of water and a compact structure as a whole.

[Key points of the invention]

In order to achieve the above object, the present invention provides a draining screen cylindrical body made of an electrically insulating material, and a rear part of the horizontal axis-shaped outer cylinder of the dehydrator main body connected to the slurry supply hopper. It is constructed as a conductive cylindrical body that serves as one electrode of the electroosmotic part, and a hollow rotating shaft with a curved surface as a water screen surface and equipped with a screw blade for squeezing and conveying slurry on the outer periphery is inserted into the outer cylinder. Then, while applying frost pressure between the outer peripheral electrode part and the rotating shaft as opposing electrodes,
By conveying the slurry as a material to be dehydrated sent to the slurry conveyance path defined between the hopper outer cylinder and the rotating shaft toward the outlet using a screw blade, the slurry is passed through a screen in the first half of the same machine. After pre-dehydration using gravity and compression, dehydration is performed in the second half by electroosmosis, which passes through the filter surface of the rotating shaft, thereby reducing power consumption and making the overall structure more compact. This system is designed to efficiently and continuously dewater slurry with a high water content, while also reducing the amount of water involved.

[Embodiments of the invention]

FIG. 2 shows an embodiment of the present invention, in which the dehydrator has a horizontal shaft type outer cylinder 101, a rotating shaft 20. The main components include a screw blade 309 for conveying slurry, a rotating shaft drive device 40, a power supply device 50, and the like. Of these, the outer cylinder 10 has a pre-dehydration section on the right side of the drawing, and this section is composed of a draining screen cylinder 11 made of an electrically insulating material, and the rear half on the left side of the drawing is one of the electroosmotic dehydration sections. The conductive cylindrical body 12 constitutes an electrode, and both are integrally assembled and connected with bolts 13. A slurry supply hopper 15 is connected to the slurry inlet 14 of the outer cylinder 10, and a cone-shaped dehydrated cake separating fluid 17 is installed facing each other with a gap in between at the outlet 16 on the opposite side.

On the other hand, the rotating shaft 20 has a large number of through-holes 21'li-perforated on its circumferential surface to form a screen surface, and the inside of the rotating shaft 20 is connected to a drain pipe 60 outside the machine through an opening at the end of the shaft. It is configured as a hollow shaft made of stainless steel, for example, defining a water discharge path 22, and is inserted along the axial center of the outer cylinder 10 via bearings 23 and 24. The above-mentioned through hole 21 is bored in the area of the permeation part of the outer cylinder 10 facing the conductive cylindrical body 12, and the rotating shaft 20 as a whole extends from the inlet side to the outlet side of the outer cylinder 10. It is configured as a tapered shaft whose outer diameter gradually increases.

Further, the screw blade 30 for conveying the slurry is connected to the hopper 15.
The slurry introduced into the outer cylinder 10 is compressed and conveyed toward the outlet 16, and the outer peripheral edge of the screw blade body is provided with an electrically insulating material that slides in contact with the inner wall surface of the outer cylinder 10. For example, a seal gasket made of hard rubber is fitted for electrical insulation. The drive device 4o includes a drive motor 41 and, for example, a gear-type power transmission mechanism 42, and slowly rotates the rotating shaft 20 in a predetermined direction by driving the motor. Further, the power supply device 50 is a DC power supply and is connected to the outer cylinder electrode part 12 via a power supply line 51 so as to apply voltage to both electrodes with the conductive outer cylinder 12 of the outer cylinder 10 as an anode and the rotating shaft 20 as a cathode. It is connected to the current-carrying terminal fitting 18 and the current-carrying terminal portion 25 of the rotating shaft 20 . The trench symbol 61 is a reactor water receiver that covers the pre-dewatering section of the outer cylinder and is connected to the external drainage system installed below it. A suction pump for drainage is connected as necessary.

In the above configuration, if power is supplied from the power supply device 50,
An electric field is formed between the conductive cylindrical part 12 of the outer cylinder 10 and the rotating shaft 20 in the electroosmotic part in the latter half of the dehydrator main body. In this state, the drive device 40 drives the rotary shaft 20 and flows from the hopper 15 through the inlet 14 into the slurry passage 70 defined between the rotary shaft 20 and the inside of the outer cylinder 10 containing a large amount of water. When the slurry 80 to be treated with a high ratio is introduced, the slurry advances toward the outlet 16 in the passage as shown by arrow A while being subjected to squeezing force and stirring force by the screw blades 30. At the same time, the slurry in the vicinity of 10 volumes of the outer cylinder remains in the hopper, and 800 weight of the slurry is loaded upward. Therefore, the slurry fed into the outer cylinder 10 is first subjected to gravity dehydration through the screen section due to the own weight of the slurry 80. Furthermore, the slurry subjected to the squeezing force by the conveyance operation of the screw blades 30 passes through the pre-dewatering section, during which water contained in the slurry passes through the screen section of the outer cylinder 10, and squeezing dewatering is performed. In addition, the screen cylinder 11 is
The water passes through and flows down to the water receiving tray 61 as shown by arrow B, from where it is drained out of the system. On the other hand, the pre-dehydrated slurry is subsequently transferred to the electroosmosis section in the latter half region by the screw blades 30. Here, as mentioned earlier, the cylindrical body 1
2 and the rotating shaft 20 are used as opposing electrodes, and an electric field is formed between them. Therefore, the water contained in the slurry is positively charged, flows toward the rotating shaft 20 that becomes the cathode-side pentode according to the direction of the electric field, is discharged on the electrode surface, and from there passes through the two through holes of the rotating shaft 20. As shown by arrow C, the reactor water collects in the reactor water discharge passage 22 inside the shaft, and is discharged to the outside of the machine via the drain pipe 60. On the other hand, the dehydrated slurry (in the form of a solid cake) is carried out of the machine through the outlet 16 of the cylindrical body 20.

The above-mentioned pre-dewatering and electroosmotic dewatering operations proceed continuously over the entire area from the inlet to the outlet of the slurry squeezing passage 70, thereby making it possible to continuously dewater the slurry. Moreover, since the above dewatering operation is carried out in a closed passageway with the outer cylinder 10 as the outer covering, the slurry does not leak to the outside untreated during the transport process inside the machine, and therefore the slurry remains in an almost raw state. Sludge with high water content and high fluidity can also be directly input for dewatering treatment. In addition, since screw blades are used as the conveying blades and the rotating shaft 20 is a tapered shaft, the slurry is not only subjected to shearing and stirring but also to compressing force, so that pre-dehydration and electroosmotic effects are sufficiently effective, and the solid content is and liquid can be separated smoothly.

An even bigger feature is that the slurry with a high moisture content, for example, 90 to 95%, is fed into the hopper 15. First, 5 to 10q6 of water is dehydrated in the pre-dehydration section, and when the moisture content is low, it is subjected to electroosmosis. As described in FIG. 1, the amount of power consumed in the electroosmosis section can be reduced.

Regarding this point, we conducted a comparative test with a conventional machine without a pre-dehydration section under the same conditions for the water content of the input slurry and the water content of the dehydrated cake after dehydration. A reduction in power consumption was achieved. In addition, the pre-dehydration section and the electroosmotic section are integrated into the front and rear parts of the outer cylinder facing the common rotating shaft with screw blades, so that each part is independent as mentioned above. Compared to an installation in which an electro-osmotic dehydrator and a pre-dehydrator are connected together, it can be constructed more compactly and the equipment cost is lower.

〔Effect of the invention〕

As described above, according to the present invention, the first half screen cylindrical body constituting the pre-dehydration section and the second half conductive cylindrical body constituting one electrode of the electroosmotic section are integrally joined to constitute the outer cylinder, and A hollow rotary shaft equipped with screw blades for transporting slurry on the outer periphery and a screen surface for P-wood on the circumferential surface is inserted into the outer cylinder, and rotates with the conductive cylindrical body of the outer cylinder. While applying a voltage between the shaft and the shaft as opposed electrodes, the slurry introduced into the slurry passage in the outer cylinder through the hopper is conveyed by the screw blade toward its outlet, and thereby the front half area inside the machine. By configuring the system to perform pre-dehydration in the first half and electroosmotic dehydration in the second half, the system has a compact structure, reduces the amount of electricity consumed in the electroosmosis section, and allows slurry with a high moisture content to be directly input. It is possible to provide an electroosmotic dehydrator with excellent dewatering performance suitable for dewatering sludge generated in the above-mentioned sewage treatment equipment.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the relationship between the initial moisture content of slurry and power consumption by electroosmotic dehydration, and FIG. 2 is a cross-sectional configuration diagram of the main part of an embodiment of the present invention. 10... Outer cylinder, 11... Screen cylinder, 12... Conductive cylinder, 14... Slurry inlet, 15... Slurry supply Hopper, 16...
... Slurry outlet, 20 ... Rotating shaft, 21 ...
... Through hole for Sawaki construction, 22 ... Reactor water discharge path, 3
0... Screw blade, 40... Rotating shaft drive device, 50... Power supply device, 60...
... Drain pipe, 61 ... Reactor water tray, 70 ...
...Sludge passage, 80...Sludge, A...
Sludge conveyance direction, B, C...F water discharge direction. Agent Patent Attorney Yama has a good mouth, a muddy tongue, and a sword that has water content (0)

Claims (1)

[Claims] 1) A draining screen cylinder made of an insulating material whose front part constitutes a pre-dehydration part, and a conductive cylinder whose rear part constitutes one electrode of an electroosmotic part. A horizontal axis-shaped outer cylinder is assembled by combining the two into one body, a slurry supply hopper is connected to the inlet side of the outer cylinder, and a number of through holes for F water permeation are bored on the circumferential surface. , and a rotary shaft inserted into the outer cylinder, which is a hollow body made of conductive material with a reactor water discharge path connected to an external drainage system defined inside the outer cylinder, and a rotary shaft mounted on the outer periphery of the rotary shaft. screw blades for conveying compressed slurry;
A drive device for the rotary shaft, a power supply device that applies a voltage between the conductive cylinder of the outer cylinder and the rotary shaft as opposed electrodes, and a space between the outer cylinder and the rotary shaft as a slurry passage. The slurry introduced through the hopper is subjected to pre-dehydration by gravity and compression through the screen part of the outer cylinder in the first half of the slurry passage, and then subjected to electroosmotic dewatering in the second half. Osmotic dehydrator. 2. An electro-osmotic dehydrator according to claim 1, wherein the rotating shaft is a tapered shaft having a small diameter on the inlet side of the slurry passage and a large diameter on the outlet side.