JPH0720528B2 - Electro-osmotic dehydrator - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electroosmotic dehydrator for dehydrating sewage sludge, sludge of industrial waste liquid, and the like.

[Prior Art] As the above-mentioned electroosmotic dehydrator, a batch processing type filter press type electroosmotic dehydrator is known, and its conventional configuration is shown in FIG. In the figure, 1 is a box-shaped processing container having an upper and lower two-part structure that is opened and closed by operating a cylinder 2.
A sludge supply port 11 is provided at the top of the container, and a drainage outlet is provided at the bottom.
12 open. In addition, the dehydration processing chamber 13
A pair of electrodes connected to the DC power supply 3 above and below the electrodes
The upper electrode 4 is arranged on the upper wall surface of the processing container 1, and the lower electrode 5 is arranged by being connected to the squeezing diaphragm 6 provided on the bottom side in the container. Reference numeral 14 is a processing air introduction port communicating with the rear side of the unloading diaphragm 6. Further, a filter cloth belt 7 is laid to cover the electrode surface of the lower electrode 5. The filter cloth belt 7 is an endless belt that is stretched inward and outward through the space between the upper and lower divided surfaces of the processing container 1 and stretched between the pulleys, and is cyclically moved by a drive motor 8.

The operation principle of the electroosmotic dehydrator having the above-described configuration is well known, and the sludge 9 (sewage sludge of the sewage sludge is introduced into the dehydration treatment chamber 13 between the electrodes 4 and 5 through the sludge supply port 11 with the treatment container 1 closed. When the electrokinetic potential (ζ-potential) of the sludge particles is supplied as a negative potential, and the electrodes 4 and 5 are used as anodes and cathodes, respectively, a voltage is applied, the water contained in the sludge 9 is filtered by the electroosmotic action. Lower electrode 5 on the cathode side through belt 7.
On the surface of the electrode, and is discharged from the system through the water distribution groove formed on the surface of the electrode. Further, by introducing pressurized air behind the diaphragm 6 in accordance with the progress of electroosmotic dehydration and applying a compressive force to the sludge 9 via the lower electrode 5 and the filter cloth belt 7, the dehydration is further promoted.

Then, when the one-time dehydration process is completed, the processing container 1 is opened by operating the cylinder 2 to remove the sludge cake remaining in the container in a caked state, and the drive motor 8 is used to filter the filter cloth belt. 7 is moved cyclically to draw out the dirty surface area to the outside of the processing container 1, and instead to draw the cleaning surface area into the processing container 1. Also, filter cloth belt 7
Residual deposits are washed out when they are pulled out of the processing container.

The above is for sewage sludge (the electrokinetic potential of sludge particles is negative), and the upper electrode 4 on the sludge supply side is used as the anode and the lower electrode 5 on the water collecting side is used as the cathode to collect the water contained in the sludge on the lower electrode side. Although it was made to water, especially in the case of sludge containing a lot of particles such as metal oxides and hydroxides such as industrial waste liquid, the electrokinetic potential (ζ-potential) of sludge particles becomes negative. Contrary to the above, a voltage is applied to the lower electrode 5 by using the upper electrode 4 as a cathode and the lower electrode 5 on the water collecting side as an anode so that the contained water is collected in the lower electrode 5.

[Problems to be Solved by the Invention]

By the way, in the conventional configuration of the electroosmotic dehydrator described above,
It is difficult to dehydrate the sludge to a sufficiently low water content, and the dewatering efficiency (ratio between power consumption and sludge dewatering amount) is large because it consumes a large amount of electricity for the sludge dewatering amount. There is a problem that low and economical driving cannot be expected, and the improvement measure is a big issue.

Then, the present inventors have made clear the following points when the property changes of the sludge were investigated with the progress of the electroosmotic dehydration. That is, FIG. 5 is an explanatory diagram of the dehydration operation by the electroosmotic dehydrator of FIG. 4, and particularly in the interior of the dehydration progressing state in which there is almost no new discharge of the filtered water even if the voltage application is further continued. It shows the sludge condition distribution. Regarding the sludge 9 sandwiched between the electrodes 4 and 5 in this dehydration progressing state,
The sludge properties of each layer were investigated separately for the upper layer 9a, the middle layer 9b and the lower layer 9c. First, the upper layer portion 9a of the sludge 9 is in a dry state with almost no fluidity, and in the portion in contact with the upper electrode 4, the sludge-containing water is generated in the void 9d locally generated due to the volume reduction of the sludge. It was confirmed that the produced gas generated by electrolysis was confined. On the other hand, the middle layer 9b and the lower layer 9c have a lower degree of dehydration and a higher water content than the upper layer 9a.
In particular, in the middle layer portion 9b, the lower layer portion 9c receives a squeezing force from the diaphragm 6 to form a consolidation layer, and this consolidation layer inhibits the permeation of water flowing from the middle layer portion 9b toward the lower electrode 5. It was found that the water content was highest and dehydration did not proceed so much.

That is, the water contained in the sludge due to the electroosmotic action is absorbed by the upper electrode 4
The sludge 9 which is in contact with the above flows from the upper layer to the lower layer in the sludge layer and is collected by the lower electrode 5. For this reason, when the upper layer 9a is first dehydrated and dried to increase its electric resistance as the dehydration progresses, thereafter, even if the middle layer 9b and the lower layer 9c have a high water content, they are sandwiched between the electrodes. It becomes difficult for electric current to flow in the sludge that has been removed. When the contained water contains a large amount of sulfate ions, chlorine ions, etc., such as sewage sludge, the contained water is electrolyzed with the application of voltage between the electrodes, and gases such as oxygen and hydrogen are generated on the electrode surface. . In this case, the gas generated on the lower electrode side 5 passes through the filter cloth belt 7 together with the filtered water and is discharged to the outside of the system, but the gas generated on the upper electrode side 4 has no escape, so As shown in the figure, the gas comes to stay between the upper electrode 5 and the sludge 9. Moreover, since the produced gas is non-conductive, the electricity to the sludge is further deteriorated.

Therefore, when the sludge state distribution in Fig. 5 is reached, even if the same voltage is continuously applied between the electrodes from this state, the dehydration of the sludge by the electroosmotic dehydration action does not proceed any further, and in order to further promote the dehydration, Therefore, it is necessary to apply a higher voltage. However, when a high voltage is supplied, the power consumption increases, and as a result, the running cost of the electroosmotic dehydrator increases and the dehydration efficiency decreases.

The present invention has been made in view of the above points, by targeting the electroosmotic dehydrator of the batch processing method described above, by improving the structure of the upper electrode disposed on the sludge supply side, and the sludge supply unit, It is an object of the present invention to provide an electroosmotic dehydrator with high dehydration efficiency, which is capable of effectively drying sludge in a localized manner and preventing electrolysis generated gas from accumulating to effectively perform electroosmotic dehydration.

[Means for Solving the Problems]

In order to solve the above problems, in the electroosmotic dehydrator of the present invention, the upper electrode provided on the sludge supply side is a through-hole electrode plate that allows the passage of sludge and gas, and on the back surface side of the electrode plate. A sludge storage chamber leading to the sludge supply port shall be provided.

[Action]

In the above configuration, the through-hole electrode plate that constitutes the upper electrode is, for example, a punching plate in which a large number of holes dispersed in the entire area of the plate are punched, or a wire mesh, and behind it (upper surface side) is a sludge storage chamber. It is placed in the middle position of the processing container leaving the space.

When sludge is supplied to the treatment container through the upper sludge supply port here, the sludge first enters the sludge storage chamber in the container, and the sludge permeates the plate through the perforated electrode plate to allow the dewatering treatment chamber space between the opposing electrodes to flow. As the sludge fills up, the remaining sludge remains in the sludge storage chamber.

On the other hand, in this state, the polarity of the electrodes is selected so that the water contained in the sludge is collected on the lower electrode side in accordance with the interfacial potential (ζ-potential) of the sludge particles. The water contained in the sludge is collected on the lower electrode side by the electroosmotic action and discharged to the outside of the system. Further, it passes through the gas permeation electrode plate generated on the upper electrode side by electrolysis of the contained water, and escapes upward from the dehydration treatment chamber. Furthermore, when the volume of sludge decreases with the progress of electroosmotic dehydration, undehydrated sludge permeates the perforated electrode plate from the sludge storage chamber to fill the void created by this volume reduction, and enters the dehydration treatment chamber. Will be replenished.

Therefore, the gas generated by electrolysis does not stay between the upper electrode and the sludge during the progress of electroosmotic dehydration, and the upper layer part of the sludge in contact with the upper electrode by replenishing the non-dehydrated sludge from the sludge storage chamber Does not stay wet and become extremely dry. As a result, the conductivity of the sludge sandwiched between the electrodes is maintained, and electroosmotic dehydration effectively proceeds until the water content of the entire sludge is sufficiently reduced by the electroosmotic action continuously working even with the same applied voltage. Come to do.

〔Example〕

FIGS. 1 to 3 show an embodiment of the present invention, and the same members corresponding to FIGS. 4 and 5 are designated by the same reference numerals.

First, in FIGS. 1 and 2, the lower electrode 5 and the filter cloth belt 7 are arranged on the bottom side of the processing container 1, and the upper electrode 4 is arranged in the middle position of the processing container 1. A dehydration treatment chamber 13 is defined inside the treatment container 1 between the upper electrode 4 and the lower electrode 5, and a sludge storage chamber 10 communicating with the sludge supply port 11 is defined behind the upper electrode 4. In addition, the treatment container 1 has a pressurized air introduction port 1 opening at the top with respect to the sludge storage chamber 10.
5, and a sludge discharge port 16 that opens to the side is provided. Further, the upper electrode 4 is made as a through-hole electrode plate having a large number of permeation holes 41 dispersed in the entire area of the electrode plate to allow the permeation of sludge and gas, as clearly shown in FIG. It is a thing.

Next, the operation of the above configuration will be described. When the treatment chamber 1 is closed as shown in the figure and sludge 9 is supplied into the treatment chamber through the sludge supply port 11, the sludge first accumulates in the sludge storage chamber 10 and then passes through the holes 41 of the upper electrode 4 to flow down to the lower portion. While filling the dehydration treatment chamber 13 between the electrode 5 and the electrode 5, the remaining sludge remains in the sludge storage chamber 10 as it is. At this point, the sludge discharge port 16 is closed.

Then, the sludge supply port 11 is closed, and the sludge 9 is pressurized by the pressurized air introduced from the pressurized air introduction port 15 while the electrodes 4 and 5 are being pressed.
And a voltage is applied from the power source 3 between them. This allows the electrode 4
The sludge 9 sandwiched between 5 and 5 has an electroosmotic action, and the water contained in the sludge 9 flows toward the lower electrode 5 in the sludge layer, passes through the filter cloth belt 7, and then passes through the drainage outlet. It is discharged out of the system through 12. On the other hand, when the volume of the sludge 9 is reduced (the volume of the sludge is reduced by discharging the filtered water) with the progress of this electroosmotic dehydration, as shown in FIG. The undewatered sludge accumulated in the sludge storage chamber 10 receives the pressure of pressurized air, permeates through the holes 41 of the upper electrode 4 and flows into the dehydration processing chamber 13 (solid arrow). In FIG. 3, reference numeral 91 is the lower-layer dehydrated sludge that has undergone electroosmotic dehydration to some extent, and 92 is the sludge storage chamber as the volume of the sludge 9 is reduced.
It represents the replenishment sludge that was newly replenished from the 10 side to the upper layer side of the sludge. Further, the gas generated on the surface of the upper electrode 4 due to the electrolysis effect caused by the voltage application between the electrodes directly escapes from the through hole 41 of the through hole electrode plate and is discharged from the dehydration treatment chamber 13 to the sludge storage chamber 10 side ( Dotted arrow). The gas generated on the lower electrode side escapes with the filtered water and is exhausted to the outside of the system.

As is clear from the above description of the operation, during the electroosmotic dehydration process, the upper layer portion of the sludge 9 in contact with the upper electrode 4 receives replenishment of the non-dehydrated sludge from the sludge storage chamber 10 and therefore does not extremely dry. The gas generated by electrolysis is discharged to the contact portion with the upper electrode 4 without stagnation. As a result, the energized state of the electric current flowing through the sludge is maintained, and the dehydration by electroosmosis proceeds continuously and effectively until the sludge 9 supplied into the dehydration treatment chamber 13 has a sufficiently low water content. .

In addition, in the operation after the dehydration treatment, first, the voltage application of the power source 3 is stopped, the sludge discharge port 16 is opened, and the high-fluidity undewatered sludge remaining in the sludge accumulating chamber 10 by the pressurized air is removed. After being discharged to the outside of the room, the processing container 1 is opened by operating the cylinder 2 to remove the caked dehydrated sludge from the dehydration processing chamber 13, and the filter cloth belt 7 is circulated to draw out the contaminated surface area to the outside of the room. This completes one batch dehydration treatment process.

Next, the results of an actual machine test conducted by the present inventors to confirm the evaluation by the electroosmotic dehydration method will be described.
In this test, the excess sludge generated in the sewage treatment plant was used as a sample, and a dehydration test was conducted using the electroosmosis dehydrator shown in FIGS. 1 and 4 under the following conditions.

(Test conditions) 1. Sample concentration: 2.2% (water content 97.8%) 2. Dehydration time: 10 minutes 3. Applied voltage: 60V (dehydrator in Fig. 1) 110V (dehydrator in Fig. 4) 4. Addition pressure air pressure: 0.5 Kg / cm ² (Fig. 1) 5Kg / cm ² (FIG. 4) 5. gap between electrodes: According to the test results at 30mm above conditions, the conventional electro-osmotic type dehydrator (fourth In the figure), the water content of the sludge decreased only to 72%, and the power consumption was calculated to be 11 tons of dry solids of the dehydrated sludge, which was 1250 KWH. On the other hand, in the electroosmotic dehydrator of the present invention (Fig. 1), the water content of sludge was reduced to 64%, and the power consumption was 620 KWH. That is, it was confirmed that the water content of sludge was reduced by 8% and the power consumption could be almost halved as compared with the conventional method.

〔The invention's effect〕

Since the electroosmotic dehydrator according to the present invention is configured as described above, it has the following effects.

That is, the upper electrode provided on the sludge supply side is formed as a through-hole electrode plate that allows permeation of sludge and gas, and a sludge storage chamber communicating with the sludge supply port is provided on the back side of the electrode plate. ) When the volume of sludge decreases with the progress of electroosmosis dehydration, non-dehydrated sludge permeates the upper electrode, which is a through-hole electrode plate, to be replenished from the sludge storage chamber side, so the upper layer of sludge in contact with the upper electrode is extremely dried. The conductivity of sludge can be maintained by preventing

(2) The electrolysis generated gas generated on the upper electrode side permeates the perforated electrode plate and immediately escapes from the dehydration treatment chamber, so that gas retention is eliminated and the electrical conductivity between the electrode and sludge due to gas retention is obstructed. Will disappear.

(3) Therefore, during the dehydration treatment process, the electrical conductivity of the current flowing through the sludge sandwiched between the electrodes is maintained, and the electroosmotic action continues and works effectively, which allows the sludge to have a low water content with a small amount of power consumption. Can be effectively dehydrated up to the point that the dehydration efficiency can be greatly improved.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention, FIG. 2 is a plan view of an upper electrode in FIG. 1, FIG. 3 is an operation explanatory diagram of electroosmotic dehydration according to FIG. 1, and FIG. Fig. 5 is an overall configuration diagram of the osmotic dehydrator, and Fig. 5 is an operation explanatory diagram of electroosmotic dehydration according to Fig. 4. In the figure, 1: treatment container, 11: sludge supply port, 12: filtered water discharge port, 13: dewatering chamber, 3: DC power supply, 4: upper electrode, 41: transmission hole, 5: lower electrode, 7: filter Cloth belt, 9: sludge, 10: sludge storage chamber.

Claims (1)

[Claims] 1. A pair of upper and lower electrodes are disposed opposite to each other inside a processing container having a sludge supply port at the top and a drainage discharge port at the bottom.
In the electroosmotic dehydrator that collects the water contained in the sludge on the lower electrode side by applying a DC voltage between the electrodes while supplying the sludge and discharges it out of the system through the filter material, An electroosmotic dehydrator, characterized in that the deployed upper electrode is a through-hole electrode plate that allows the passage of sludge and gas, and a sludge storage chamber that communicates with a sludge supply port is provided on the back side of the electrode plate.