JPS6344406B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sludge dewatering device that can continuously perform dewatering by electroosmosis.

Sludge is interposed between the anode and cathode of DC current,
The principle of dewatering sludge by collecting sludge on the anode side and water on the cathode side has been known for a long time, and batch-type or batch-type dewatering devices that apply this principle are also known. Furthermore, in order to increase the dehydration rate, there is also known a batch-type device that utilizes this principle and dehydrates while applying pressure.

However, all conventional devices are batch-type and cannot perform dewatering operations continuously, so they are not suitable for use in places where large amounts of sludge are generated continuously, such as sewage treatment plants and human waste treatment plants. There are problems such as insufficient processing capacity and the need to install multiple units.

Therefore, it is an object of the present invention to provide an apparatus that can perform dewatering continuously using the above-mentioned principle and also includes pressurizing operation, thereby obtaining dehydrated sludge with high capacity and low water content. The present invention will now be described with reference to the illustrated embodiments.

The basic configuration of the present invention will be described with reference to the drawings. It has an endless circulating main fabric belt (main belt) 1a and a subordinate fabric belt (subordinate belt) 1b, and the main belt 1a is independent and substantially horizontal. A sludge supply frame 2 is provided above the traveling section and supplies sludge onto the main belt, and beyond that the subordinate belt 1b overlaps the upper surface of the main belt 1a, and both belts 1a and 1b are in a polymerized state. The press rolls 3... are sewn in a staggered manner in groups, and are equipped with a pressurized dewatering section that further dewaters the sludge sandwiched between both belts by surface pressure, and both belts 1a, 1b.
After passing through the group of squeezing rolls 3..., the scrapers 4a, 4 separate by moving in different directions, and scrape off the dehydrated sludge adhering to the belt surface, respectively.
(b) The main belt returns to the lower surface of the slurry supply frame 2, and the subordinate belt returns to a position superimposed on the main belt beyond that, via washing devices 5a and 5b that eject washing water. A liquid receiver may be provided below the sludge supply frame 2 to receive water in the sludge supplied onto the main belt as it passes through the main belt due to gravity and falls. The above configuration is almost the same as the belt press type dewatering device proposed by the applicant of this patent in Utility Application No. 53-24631 (Utility Model Application No. 53-24631), and for details, please refer to the explanation of the above-mentioned earlier application. Omitted.

Now, the pressurized dewatering section of the above-mentioned dewatering device only dewaters the sludge interposed between the two belts using surface pressure based on the tension of both belts 1a and 1b, but in the present invention, the pressurized dewatering section In this embodiment, a conductive material is provided on the outer peripheral surface of the three press rolls 3' to serve as either negative or positive electrodes, and the belt that directly contacts the press rolls 3' that also serve as electrodes is as in this embodiment. If it is the secondary belt 1b, the other main belt 1
a. Conversely, when the main belt 1a is in direct contact with the pressing roll 3', the outer surface of each of the subordinate belts 1b is made of a conductive material that allows water to pass through, and the other electrode is applied to an endless electrode belt 6. Along, master and slave belt 1
In the section where a and 1b move around the electrode/squeezing roll 3' with the sludge in between while pressurizing and dehydrating, an electroosmotic action is performed between the roll 3' and the electrode belt 6,
In this section, pressure dehydration and electroosmotic dehydration are performed simultaneously in three stages in the front and back direction, electroosmotic dehydration section 7-
, 7-, 7-. The three belts 1a, 1b, 6 can be run by driving the compression roll 3' of the front stage 7-.

The endless electrode belt 6 can be a metal wire, for example, a net belt made of stainless steel wire, and in this embodiment, the electrode belt 6 is superimposed on the back side of the main belt 1a to form a pressing roll 3' which also serves as an electrode.
The front and rear rolls 3a and 3b, which are located at the front and rear of the roll and are circumscribed on the left and right upper portions of the squeeze roll 3', have an inverted Ω shape, and are extremely long and extend around almost the entire circumference of the squeeze roll 3'. Pressurized electroosmotic dehydration section 7-,
7-, 7-, and the subsequent roll 3
It separates from the main belt 1a on top b and moves downward, turns upwards until it reaches the tension adjustment roll 8 below the pressing roll 3', and overlaps the back side of the main belt 1a on the previous roll 3a. The tension adjustment roll 8 applies a high tension to the electrode belt 6 and presses it against the squeezing rolls 3' of the master and slave belts 1a and 1b, and the pressurized dewatering is preferably carried out under a surface pressure of 1 to 10 kg/cm ² .

In this embodiment, a liquid receiver 9 is provided inside the electrode belt 6 to receive water that is dehydrated while the pressing roll 3' advances.
A cathode for collecting water is applied to the electrode belt 6,
An anode is applied to the press roll 3'. The current density of the applied direct current may be 0.5 to 2.5 A/dm ² . or,
The current application time may be in the range of about 1 to 10 minutes, and therefore depends on the diameter and number of pressing rolls that also serve as electrodes.
The running speed of the cloth may be appropriately determined within the range of 0.5 to 3 m/min.

To apply current to the electrode belt 6, a power supply brush 8' connected to one pole of a power supply may be brought into sliding contact, or the surface of the roll, for example, the tension adjustment roll 8, on which the electrode belt 6 is applied may be brought into sliding contact. It may be made of a conductive material, and a power supply brush connected to one pole of a power source may be brought into sliding contact with its shaft. Further, the surface of the pressing roll 3' is made of at least a conductive material, for example, a current collecting ring 10 is provided on its shaft, and a power feeding brush 10' connected to the other pole of the power source is brought into sliding contact with the current collecting ring. good.

The sludge supplied to the sludge supply frame is grown into large flocs by adding a flocculant, and has a water content of about 90% (for this purpose, it may be pre-dehydrated by gravity dewatering etc.). It is preferable that the surface pressure applied by the electrode belt 6 to the sludge between the main and sub-belts in the pressurized electroosmotic dewatering sections 7-, 7-, 7- prevents the sludge from overflowing from between the main and sub-belts to both sides or stagnates at the entrance of the section. 1 to 10 depending on the water content of the sludge so that it does not enter the section or cause a backflow phenomenon.
It is appropriately selected within the range of Kg/cm ² , for example, when the water content is about 90% as mentioned above, it is about 2 Kg/cm ² . In addition, a plate-shaped or brush-shaped draining means is provided on the inner surface of the electrode belt 6 in order to drain the water that has passed through the main belt 1a and the electrode belt 6 and seeped onto the inner surface of the electrode belt and actively drain it into the liquid receiver 9. It is also possible to make sliding contact.

Since the water content of the sludge decreases sequentially from the pressurization in the first stage and the electroosmotic dehydration section 7- to the pressurization in the second stage and the electroosmotic dehydration section 7-, it is preferable that the surface pressure be made larger in the later stages; As for the applied current density, the voltage level tends to increase as the water content decreases, so it is necessary to set the current density lower in the later stages, taking into account wear and tear on the electrodes.
Select appropriately within the range of 0.5 to 2.5 A/ ^dm2 .

Using an experimental machine with the same structure as shown in this figure, the following is a comparison experiment between dehydration by applying an electric current and dehydration by applying pressure only without applying an electric current.

The supplied sludge has a water content of 89.7%, which is obtained by adding a polymer flocculant to mixed sewage sludge, followed by gravity dewatering.

The diameter of the press roll 3' which also serves as a positive electrode in the pressurization and electroosmotic dehydration section of each stage is 600 mm, the running speed of the main and subordinate belts is 1 m/min (current application time 3.6 minutes), the surface pressure in the pressurization and electroosmotic dehydration section. is 2Kg/cm ² at the first stage 7-, 4Kg/cm ² at the second stage 7-, and 6Kg/cm ² at the third stage 7-.
When dewatering was performed without applying an electric current, the moisture content of the dehydrated sludge was 75%.

While applying the above conditions, the current density in the electroosmotic dehydration section was set to 1.6A/ ^dm2 in the first stage and 1.3A/dm2 in the second stage.
dm ² , and in the third stage, when dewatering was performed by applying 1.0 A/dm ² , the water content of the dehydrated sludge decreased to 61%.

In this way, the pressurized electroosmotic dehydration sections are provided in multiple stages in the front-rear direction, and the pressing force by the endless electrode belt in each section is stronger in the later stages, and the applied current density between the roll and the endless electrode belt is smaller in the later stages. As a result, dehydrated sludge with extremely low water content can be obtained continuously.

[Brief explanation of drawings]

The drawing is a side view of one embodiment of the present invention, and in the drawing, 1
1b is a main fabric belt, 1b is a secondary fabric belt, 3' is a pressing roll whose surface is made of a conductive material, 6 is an electrode belt, 7-, 7-, 7
- indicates the pressurization and electroosmotic dehydration sections, respectively.

Claims (1)

[Scope of Claims] 1 A pair of main fabric belts are partially overlapped and stretched endlessly, and are circulated in one direction at a constant speed, and the main fabric belts are fed onto the main fabric belt before the overlapping area. The sludge is sandwiched between the polymerization areas and dehydrated.
In a sludge dewatering device that separates dehydrated sludge from each belt after passing through a polymerization region and separating both belts, the polymerization region of the main and sub-fabric belt has a surface made of a conductive material, and the polymerized main and sub-fabric belt has a surface made of a conductive material. a water-permeable endless electrode belt made of a conductive material that circulates while pressing the portion surrounding the roll from the outside against the roll surface; and a surface of the roll. A plurality of pressure and electroosmotic dehydration sections are provided in the front and back direction, and the pressure and electroosmotic dehydration sections are provided in a plurality of stages in the front and back direction, and the pressure and electroosmotic dehydration sections are made up of a means for applying a DC current to one pole of the DC current and a means for applying an endless electrode belt to the other pole of the DC current. A sludge dewatering device characterized in that the pressing force by the electrode belt in the electroosmotic dewatering section is stronger in the later stages, and the current density applied between the roll and the electrode belt is smaller in the later stages. 2. The sludge dewatering device according to claim 1, wherein each main and subordinate belt returns to the sludge supply section via a washing device.