JPH0356107A - Electroosmotic dehydrator - Google Patents

Abstract

PURPOSE:To carry out electroosmotic dehydration efficiently by using an upper electrode installed in the sludge supply side as a permeable porous electrode plate and installing a sludge storing chamber which is led to a sludge supply inlet in the rear side of the electrode plate. CONSTITUTION:A pair of up side and down side electrodes 4,5 facing each other are installed in a treatment container 1 having a sludge supply inlet 11 in upper side and a filtered water discharge outlet 12 in the bottom, and water in sludge is collected to the down side electrode 5 by applying d.c. voltage between the electrodes 4,5 while the sludge is supplied and discharged outside of the system through a filter 7. The upper side electrode 4 installed in the sludge supply side is used as a permeable porous electrode plate to allow the sludge and a gas to permeate and a sludge storing chamber 10 which is connected to a sludge supply inlet 11 is installed in the rear side of the electrode plate. As a result, the sludge is prevented from being partially dried and electrolytically decomposed gases are prevented from staying and thus electroosmotic dehydration can be carried out efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electroosmotic dehydrator for dewatering sewage sludge, industrial waste sludge, and the like.

[Prior Art] As the above-mentioned electroosmotic dehydrator, a filter press type electroosmotic dehydrator using a batch processing method is known, and the conventional configuration thereof is shown in FIG. 4. In the figure, 1 is a box-shaped processing container with an upper and lower structure that can be opened and closed by operating a cylinder 2.
A sludge supply port 11 is opened at the top 81≦ of the container, and a filtrate discharge port 12 is opened at the bottom. Further, inside the processing container, two electrodes 4.5 connected to a DC voltage a3 are arranged facing each other above and below the dehydration processing chamber l3, and the upper electrode 4 is arranged on the upper wall surface of the processing container l. The lower electrode 5 is arranged in conjunction with a squeezing diaphragm 6 provided on the bottom side of the container. Note that 14 is a pressurized air inlet that communicates with the rear side of the delivery diaphragm 6. Furthermore, a filter cloth helt 7 is installed to cover the electrode surface of the lower electrode 5. This filter cloth belt 7 is an endless belt that is stretched between the pulleys by passing between the upper and lower [delta] sides of the processing container 1 so as to span the inside and outside, and is operated to move around by a driving moke 8.

The operating principle of the electroosmotic dehydrator according to the above i-precept is well known, and the sludge 9 (
The interfacial potential (ζ-potential) of sludge particles in sewage sludge is a negative potential), and when a voltage is applied using electrodes 4 and 5 as anode and cathode, respectively, the water contained in sludge 9 undergoes electroosmotic action. The water passes through the filter cloth belt 7 and collects on the surface of the lower electrode 5 on the cathode side, from where it is discharged to the outside of the thread from the water distribution port 12 via the water guide groove formed on the electrode surface. In addition, pressurized air is introduced behind the diaphragm 6 as the electroosmotic dehydration progresses, and the lower electrode 5. By applying squeezing force to the sludge 9 through the filter cloth belt 7, dewatering is further promoted. When one dehydration process is completed, the processing container 1 is opened by operating the cylinder 2, and the sludge cake remaining in the container in a caked state is removed.
The filter cloth belt 7 is rotated by the drive motor B so that the contaminated surface area is drawn out of the processing container 1, and the clean surface area is drawn into the processing container 1 instead. Further, any remaining deposits on the filter cloth belt 7 are removed by cleaning after being pulled out of the processing container. Note that the above is for sewage sludge (the interfacial potential of sludge particles is negative), and the upper electrode 4 on the sludge supply side is used as the anode. The lower electrode 5 on the water collection side is used as a cathode to collect water containing sludge to the lower electrode. In sludge containing many particles such as hydroxide, the interfacial potential (ζ-potential) of the sludge particles becomes negative, so in this case, contrary to the above, the upper electrode 4 is used as the cathode, and the lower electrode 5 on the water collection side By using the electrode as an anode and applying a voltage, the contained water is collected to the lower electrode 5.

[Problem to be solved by the invention]

By the way, in the conventional structure of the electroosmotic dehydrator mentioned above,
In addition to being difficult to dewater sludge to a sufficiently low water content, it also consumes a large amount of electricity relative to the amount of sludge dewatered, so the dewatering efficiency (ratio of power consumption to sludge dewatering amount) is low. There is a problem in that the low temperature and economical operation cannot be expected, and measures to improve this problem have become a major issue.Therefore, the inventors investigated changes in the properties of sludge as electroosmotic dewatering progresses, and found the following points. In other words, Fig. 5 is an explanatory diagram of the dewatering operation by the electroosmotic dehydrator shown in Fig. 4, and is especially suitable for dehydration in which almost no new filtrate is discharged even if the voltage is continued to be applied beyond this point. It shows the sludge state distribution inside the machine in the progressing state.For the sludge 9 sandwiched between the electrodes 4 and 5 in this dehydration progressing state,
The sludge properties in each layer were examined by dividing into upper layer 9a+, middle layer 9b, and lower layer 9c. First, the upper layer 9a of the sludge 9 is in a dry state with almost no fluidity, and in the area in contact with the upper electrode 4, there is water containing sludge in the voids 9d that are locally formed as the sludge is sterilized. It was observed that biogas generated by electrolysis was trapped. On the other hand, the middle layer part 9b and the lower layer part 9c have a lower degree of dehydration and a higher water content than the upper layer part 9a. In particular, in the middle layer part 9b, the lower layer part 9c forms a compacted layer under the compression force of the diaphragm 6, and this compacted layer obstructs the permeation of water flowing from the middle layer part 9b toward the lower part 5. It was observed that the water content was the highest and that dehydration had not progressed much. That is, the water contained in the sludge due to electroosmosis flows through the sludge layer from the upper layer of the sludge 9 in contact with the upper electrode 4 to the lower layer, and is collected at the lower electrode 5.

For this reason, as the dehydration progresses, the upper layer 9a first dehydrates and dries and its electrical resistance increases, and then the middle layer 9a
b. Even if the water content of the lower layer 9c is high, it becomes difficult for current to flow into the sludge sandwiched between the electrodes. In addition, if the water contains a lot of sulfate ions, chloride ions, etc., such as sewage sludge, the water will be electrolyzed when voltage is applied between the electrodes, and gases such as oxygen and hydrogen will be generated on the electrode surface. . In this case, the gas generated on the lower electrode side 5 passes through the filter cloth belt 7 along with the filtrate and is discharged out of the system, but the gas generated on the upper electrode side 4 has no place to escape. As shown in Figure 5, gas becomes trapped between the upper electrode 5 and the sludge 9. Moreover, since this generated gas is non-conductive, it further worsens the conduction of electricity to the sludge.

Therefore, when the sludge state distribution shown in Fig. 5 is reached, even if the same voltage is continued to be applied between the electrodes from this state, sludge dewatering due to electroosmotic dehydration will not proceed any further; It is necessary to apply a higher voltage. However, when a high voltage is supplied, the power consumption increases accordingly, and as a result, the running cost of the electroosmotic dehydrator increases, and the dewatering efficiency decreases.

The present invention has been made in consideration of the above points, and is aimed at the above-described batch processing type electroosmotic dewatering machine, by improving the structure of the upper electrode disposed on the sludge supply side and the sludge supply section. The purpose of the present invention is to provide an electroosmotic dehydrator with high dewatering efficiency, which prevents local drying of sludge and retention of gas generated by electrolysis, and allows electroosmotic dehydration to proceed effectively.

[Means to solve the problem]

In order to solve the above problems, in the electroosmotic dehydrator of the present invention, the upper electrode disposed on the sludge supply side is a through-hole electrode plate that allows the permeation of sludge and gas, and the upper electrode is formed on the back side of the electrode plate. It shall be constructed with a sludge sump chamber communicating with the sludge supply port.

[Effect]

In the above configuration, the perforated electrode plate that serves as the upper electrode is, for example, a punched plate with a large number of holes perforated over the entire temporary area, or a wire mesh, and behind it (on the top side) there is a sludge reservoir. It is placed in the middle of the processing container, leaving a space for the chamber.

When sludge is supplied to the processing container through the sludge supply port at the top, the sludge first enters the sludge chamber inside the container, flows down from there through the through-hole of the perforated electrode plate, and enters the dehydration processing chamber space between the opposing electrodes. The remaining sludge remains in the sludge chamber.

On the other hand, in this state, select one polarity and apply a voltage between the electrodes so that the water contained in the sludge is collected on the lower electrode side in accordance with the interfacial dynamic potential (ζ-potential) of the sludge particles. For example, water contained in sludge is collected on the lower electrode side by electroosmosis and is discharged outside the system.

Further, gas generated on the upper electrode side by electrolysis of the contained water passes through the perforated electrode plate and escapes upward from the dehydration treatment chamber. Furthermore, when the sludge is sterilized as electroosmotic dewatering progresses, undehydrated sludge passes through the perforated electrode plate from the sludge chamber to fill the void created by this volume reduction and enters the dehydration treatment chamber. will be replenished.

Therefore, gas generated by electrolysis does not accumulate between the upper electrode and the sludge during electroosmotic dewatering, and the upper layer of the sludge in contact with the upper electrode prevents undehydrated sludge from being captured from the sludge storage chamber. The area remains moist and does not become extremely dry. As a result, the conductivity of the sludge sandwiched between the electrodes is maintained, and even with the same applied voltage, the electroosmotic action continues to work, making electroosmotic dewatering effective until the water content of the entire sludge is sufficiently reduced. It will progress to.

[Embodiment] FIGS. 1 to 3 show embodiments of the present invention, and the same members corresponding to FIGS. 4 and 5 are given the same reference numerals. First, Figure l. In FIG. 2, a lower electrode 5 and a filter cloth belt 7 are placed on the bottom side of the processing container l, and
The upper electrode 4 is installed in the middle position, and with this arrangement, a dehydration treatment chamber 13 is provided inside the processing vessel l between the upper electrode 4 and the lower electrode Fi5, and a sludge supply port is provided behind the upper electrode 4. The sludge sump room 10 leading to 1l is shown in detail. In addition, the processing vessel l with respect to the sludge storage chamber 10 has a pressurized air inlet 15 that opens at the top, and a sludge discharge port l6 that opens to the side.
is provided. Furthermore, the upper electrode 4 is sludge-covered over the entire area of the electrode plate, as clearly shown in FIG. It is made as a perforated electrode plate having a large number of permeation holes 4l that allow gas to pass through.

Next, we will explain the movements based on the above-mentioned Kaikai. When the processing chamber l is closed and the sludge 9 is supplied into the processing chamber through the sludge supply port l1 as shown in I2I, the sludge first accumulates in the sludge storage chamber IO,
From here, it passes through the hole 4l of the upper electrode 4 and flows down, filling the dehydration chamber l3 between it and the lower electrode 5, and the remaining shield mud remains in the sludge reservoir chamber lO. In addition,
At this point, the sludge discharge port 16 is closed. Next, the sludge supply port 11 is closed, and the pressurized air introduction port 15 is closed.
With the sludge 9 pressurized by the pressurized air introduced, the electrode 4
Electricity between and 5? Apply voltage from a3. As a result, an electroosmotic effect acts on the sludge 9 sandwiched between the electrodes 4 and 5, and the water contained in the sludge 9 flows within the layer of sludge toward the lower electrode 5, passing through the filter cloth belt 7. Rear filtrate outlet l2
is discharged from the system through On the other hand, as the electroosmotic dewatering progresses, the volume of the sludge 9 decreases (the volume of the sludge decreases due to the discharge of filtrate), as shown in FIG.
The undehydrated sludge remaining in the sludge storage chamber 10 is subjected to the pressure of the pressurized air to compensate for the volume decrease in the sludge chamber 10, passes through the hole 4l of the upper electrode 4, and flows into the dehydration treatment chamber l3 (as indicated by the solid line arrow). )
do. In addition, in FIG. 3, 9l is the dehydrated sludge on the lower layer side where electroosmotic dehydration has progressed to a certain extent, and 92 is the replenishment newly replenished from the sludge reservoir chamber 10 side to the upper layer side of the sludge as the volume of sludge 9 has been reduced. It represents sludge. Furthermore, gas generated on the surface of the upper electrode 4 due to the electrolytic action accompanying the voltage application between the electrodes escapes as it is through the through holes 4l of the perforated electrode plate and is discharged from the dehydration chamber 13 to the sludge reservoir chamber 10 side. Dotted line arrow〉.The gas generated on the lower electrode side escapes together with the filtrate and is exhausted outside the system.As is clear from the above operation explanation, during the electroosmotic dehydration process, the upper electrode 4 The upper part of the sludge 9 in contact with the sludge 9 is replenished with undehydrated sludge from the sludge storage chamber 1O, so it continues to maintain conductivity without becoming extremely dry, and the gas generated by electrolysis does not interact with the upper electrode 4. The sludge is discharged without stagnation in the contact area.As a result, the current flowing through the sludge is maintained, and the sludge 9 supplied to the dehydration treatment chamber 13 is dehydrated by electroosmosis until its moisture content becomes sufficiently low. The dewatering process proceeds continuously and effectively.The operation after the dewatering process is to first stop the voltage application to the power source 3, open the sludge discharge port 16, and use pressurized air to drain the sludge remaining in the sludge chamber lO. After discharging the non-dehydrated sludge with high fluidity outside the room, the treatment container 1 is opened by operating the cylinder 2, and the caked dehydrated sludge is removed from the dewatering treatment chamber 13, and then the filter cloth belt 7 is circulated. The soiled surface area is moved outside and one batch dehydration process is completed.Next, the results of an actual machine test conducted by the inventors to confirm the evaluation using the electroosmotic dehydration method described above. Let's talk about.

In this test, excess sludge generated at a sewage treatment plant was used as a sample, and a dehydration test was conducted under the following conditions using the electroosmotic dehydrator shown in FIGS. 1 and 4.

(Test conditions) 1. Sample concentration: 2.2% (water content 97.8%)2. Dehydration time: 10 minutes 3. Applied voltage: 60V (dehydrator shown in Figure 1) 110V (dehydrator shown in Figure 4) 4. Pressurized air pressure: 0. 5 Kg/c4 (Fig. 1) 5 Kg/c (Fig. 4) 5. Inter-electrode spacing: 30 - According to the test results under the above conditions, in the conventional electroosmotic dehydrator (Figure 4), the water content of sludge decreased only to 72%, and the power consumption was lower than that of dehydrated sludge. It was 1250KWH in terms of 1 ton of dry solid content. On the other hand, in the electroosmotic dehydrator of the present invention (Figure 1), the water content of sludge is reduced to 64%, and the power consumption is 620 KW.
It was I. In other words, it has been confirmed that the water content of sludge is 8% lower than with the conventional method, and power consumption can be reduced by almost half. [Effects of the Invention] Since the electroosmotic dehydrator according to the present invention is configured as explained above, it has the following effects. That is, by using the upper 1TFI provided on the sludge supply side as a perforated electrode plate that allows permeation of sludge and gas, and by providing a sludge reservoir chamber communicating with the sludge supply port on the back side of the electrode plate, the following results can be achieved. ) As the sludge expands as electroosmotic dewatering progresses, non-dehydrated sludge flows from the sludge reservoir side to the upper 1t electrode, which is a temporary through-hole electrode.
3if! Since the upper layer of the sludge in contact with the upper electrode is prevented from drying out excessively, the conductivity of the sludge can be maintained. (2) The electrolysis product or gas generated on the upper electrode side passes through the perforated electrode plate and immediately escapes from the dehydration treatment chamber, eliminating the accumulation of gas and inhibiting the conductivity between the electrode and the sludge due to gas accumulation. There's nothing to do. (3) Therefore, during the dewatering process, the conductivity of the current flowing to the sludge sandwiched between the electrodes is maintained, and the electroosmotic action continues and works effectively, thereby reducing the sludge with less power consumption. It is possible to effectively dehydrate down to the water content, and the dehydration efficiency can be significantly improved.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of an embodiment of the present invention, Fig. 2 is a plan view of the upper electrode in Fig. 1, Fig. 3 is an explanatory diagram of the electroosmotic dehydration operation according to Fig. 1, and Fig. 4 is a conventional FIG. 5 is an overall configuration diagram of the electroosmotic dehydrator, and FIG. 5 is an explanatory diagram of the operation of electroosmotic dehydration according to FIG. In the figure, l: processing container, 1l: sludge supply port, 12: filtrate discharge port,
13: Dehydration treatment chamber, 3: DC power supply, 4: Upper electrode, 4l
: Transmission hole, 5: Lower electrode, 7: 1l cloth belt, 9: Sludge, lO: Sludge sump chamber. Figure 1 Figure 2 A7? - Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1) A pair of upper and lower electrodes are placed facing each other inside a treatment container with a sludge supply port at the top and a filtrate discharge port at the bottom, and a DC voltage is applied between the electrodes while sludge is being supplied.
In an electroosmotic dewatering machine in which the water contained in sludge is collected on the lower electrode side and discharged to the outside of the system through a filtration material, the upper electrode placed on the sludge supply side is a perforated electrode plate that allows sludge and gas to permeate. An electroosmotic dewatering machine characterized in that a sludge reservoir chamber communicating with a sludge supply port is provided on the back side of the electrode plate.