JPH02119906A - Electroosmotic dehydrator - Google Patents

Abstract

PURPOSE:To efficiently execute electroosmotic dehydration with lower electric power consumption by expelling the gas generated between sludge and a non- water collecting side electrode by the electrolytic effect in an electroosmotic dehydration process to the outside of the system through venting passages. CONSTITUTION:A voltage is impressed between the electrodes on an anode 1a and cathode 2 side which face each other via a sludge passage to collect the water contained in the sludge 5 supplied in the sludge passage to one electrode side by the electroosmotic effect. The filtrate is discharged to the outside of the system through a filter member 3. Strings 6 to form the venting passages 6a between the surface of the electrode 1a and the sludge 5a are laid to the electrode 1a on the non-water collecting side across the inside and outside of the sludge passage. Further, the gas generated between the non-water collecting side electrode 1a and the sludge 5 in the electroosmotic process is expelled to the outside of the system through the venting passages 6a. As a result, the increase in the contact electric resistance occurring in the gas stagnation is averted and the electroosmotic dehydration is efficiently executed with the lower electric power consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electroosmotic dewatering machine for dewatering sludge generated in a treatment process at a sewage treatment plant or human waste treatment plant.

[Conventional technology]

As an electroosmotic dewatering machine that continuously dehydrates sludge by applying electroosmosis, an electroosmotic dewatering machine having the configuration shown in Fig. 5@, R6 is known in Japanese Patent Application Laid-Open No. 60-25597.

In the figure, 1 is a rotating drum equipped with an anode side electrode 1a on its circumference, 2 is a press belt that is stretched across the rotating drum 1 and also serves as a cathode side electrode, and 3 is a press belt 2
4 is a DC power supply that applies voltage between the anode side electrode 1a and the cathode side electrode 2;
A sludge passage serving as a dewatering area is formed in the opposing surface area between the press belt 2 and the press belt 2.

With this configuration, when the press belt 2 is driven and the pre-dehydrated sludge 5 is supplied to the sludge passage with a voltage applied between the electrodes, the sludge 5 is transferred to the rotating drum 1 and the press belt 2.
During this process, it is subjected to electroosmotic action due to the electric field between the opposing electrodes in addition to the mechanical squeezing force.

That is, the particles of sludge 5 (negative potential) are negative.

The contained water is positively charged, and the sludge water flows toward the press belt 2 on the cathode side, where it is discharged to the electrode member, and
It passes through the filter belt 3 and is separated and dehydrated from the sludge 5. Further, the filtered water that has passed through the filter belt 3 drips downward through a drainage hole 2a (FIG. 6) drilled in the press belt 2, and is drained out of the system from there. On the other hand, the sludge 5 is dehydrated and turned into a cake with a low moisture content, which is then carried out along the press belt 2.

It will be collected.

In addition, since the potential of the particles of the sludge 5 is negative, the li property of the t-pole 1a (non-water collecting side) of the rotating drum 1 is positive,
The polarity of the electrode (water collection side) of press belt 2 was set to negative,
In particular, when the ζ-potential of the sludge particles is positive, the voltage is applied with the polarity of the electrode 1a on the rotating drum side being negative and the polarity on the press belt 2 side being positive.

[Problem to be solved by the invention]

By the way, general sludge generated in sewage treatment plants, human waste treatment plants, etc. contains a large amount of sulfate ions, chloride ions, etc. in the water contained therein. For this purpose, sludge-containing water is electrolyzed in the electroosmosis process described above, and oxygen gas and chlorine gas are released to the anode side.
Further, hydrogen gas is generated on the cathode side. In this case, the gas generated on the surface of the cathode side electrode (press belt 2) passes through the filter belt together with the filtrate separated from the sludge and is eliminated from the system. On the other hand, the gas generated on the surface of the anode side electrode (rotating drum 1) has no place to escape, and as shown in FIG. Become. Furthermore, since this generated gas is non-conductive, it results in an increase in the electrical resistance of the contact surface between the electrode 1a and the sludge 5.

On the other hand, the amount of water transferred by electroosmosis, that is, the dewatering capacity, is proportional to the magnitude of the current flowing through the sludge, so as mentioned above, gas is trapped between the electrode and the sludge. This inhibits conductivity, making it difficult for current to flow through the sludge, and if this continues, the dewatering ability of electroosmosis will decrease.

Therefore, in order to maintain a predetermined dehydration processing capacity in an electroosmotic dehydrator, it is necessary to increase the voltage applied between the electrodes to compensate for the increase in electrical resistance caused by residual gas.

However, when the applied voltage is increased, the amount of power consumed increases, and as a result, the running cost of the electroosmotic dehydrator increases, and the dewatering efficiency, which is expressed as the ratio between the amount of power consumed and the amount of sludge dewatered, decreases.

The present invention has been developed in view of the above points, and is designed to eliminate gas generated between the sludge and the electrode on the non-water collection side that is not equipped with a filter member (filter belt) through electrolysis during the electroosmosis process. To provide an electroosmotic dewatering machine that avoids an increase in contact electrical resistance caused by gas retention by removing gas from the system by a simple means, and enables efficient electroosmotic dehydration with low power consumption. purpose.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, first
As a solution to this problem, a string that forms a degassing passage between the surface of the electrode and the sludge is laid inside and outside of the sludge passage for the electrode on the non-water collection side, and the string is installed inside and outside of the sludge passage. The structure is such that gas generated between the side electrode and the sludge is removed from the system through the gas vent passage.

In addition, as a second solution, a string with gas permeability is laid across the sludge passage between the opposing electrodes, and the gas generated between the non-water collection side electrode and the sludge during the electroosmosis process is The water is introduced through the internal pores of the string to a filtration member provided on the water collection side electrode, and is removed from the system from there.

[Effect]

First, in the first means, the string is, for example, a synthetic rubber belt body with a convex cross section, and its narrow end surface is in contact with the electrode surface of the non-water collection side electrode, and the string is stretched in and out parallel to the sludge passage. It is well laid out.

Note that if the non-water collecting side electrode is in the form of a rotating drum, the strings are laid along the circumferential surface of the rotating drum.

When pre-dehydrated sludge (lower fluidity than raw sludge) is supplied to the sludge passage between the opposing electrodes, the strings bite into the sludge and form gas venting passages behind the wide end faces of the strings. A functional void communicating with the atmosphere will remain. Therefore, gas generated on the surface of the non-water collection side electrode by electrolysis of sludge water during the electroosmosis process is exhausted to the atmosphere via the gas vent passage. This prevents the generated gas from remaining between the sludge and the electrode surface, and it is possible to avoid an increase in the contact electrical resistance between the electrode and the sludge due to the residual gas.

On the other hand, in the second method, the string is a gas-permeable belt made of sponge-like synthetic rubber having open-cell pores, and one end of the string is placed in contact with the electrode surface on the non-water collection side. The other end surface is placed in contact with the filter member placed on the counter electrode. Therefore, the gas generated on the surface of the non-water collection side electrode due to the electrolysis of sludge water during the electroosmosis process does not stay in this part, but diffuses through the internal pores of the gas-permeable string, and further It is discharged to the atmosphere through a filtering member that is in contact with the other end surface of the string.

[Example] Next, an example of the first solving means and the second solving means described above will be described with reference to FIGS. 1, 2, 3, and 4. In addition, FIG. 5 in each figure.

Identical members corresponding to FIG. 6 are given the same reference numerals.

Example 1! First, in FIGS. 1 and 2, 6 is a string serving as an endless belt body, and a plurality of strings 6 are distributed at predetermined pitch intervals along the width direction of the rotating drum so as to surround the surface of the rotating drum 1. It is laid down. Further, the string 6 has a convex cross-sectional shape, and when the narrow end surface is in contact with the surface of the electrode 1a as shown in FIG. 7 and a rack is placed between them.

Here, when the sludge 5 pre-dehydrated in the previous stage is supplied to the sludge passage between the opposing electrodes, the string 6 comes to bite into the sludge 5 as shown in FIG.

In this case, since the sludge 5 has low fluidity due to pre-dewatering, the proportion of the sludge 5 spreading in the lateral direction is small, so when the string 6 bites into the sludge 5 as described above,
The sludge 5 is pushed away in the maximum width range of the string 6, and on the back side of the string 6, as shown by the symbol 6a, ii 8i
A void is formed that functions as a gas venting passage surrounded by the surface of 1a and the sludge 5. This degassing passage 6a is formed along the string member 6 laid both inside and outside the sludge passage, and is open to the atmosphere at the entrance and exit points of the sludge passage.

Therefore, gas generated on the surface of the electrode 1a by electrolysis of sludge-containing water during the electroosmosis process of the sludge 5 moves to the gas vent passage 6a opened in the vicinity, and is exhausted to the atmosphere through the passage. be done.

As a result, generated gas does not remain between the electrode surface of the rotating drum 1 and the sludge 5, and an increase in contact electrical resistance between the electrode 1a and the sludge 5 due to residual gas is avoided, resulting in high conductivity. gender is ensured. As a result, a sufficient amount of current can be continued to flow through the sludge 5 and a high electroosmotic dewatering ability can be maintained without increasing the applied voltage more than necessary.

Next, the results of an actual machine test conducted to confirm the effects of the present invention will be described. In this test, raw sludge generated at a sewage treatment plant was pre-dehydrated using a roll dehydrator to a moisture content of 81%, and the sample was processed at a processing rate of 90 kg/po/h.
Moisture content 65% in r (dehydration filtration area converted to per liter)
The sludge sample was dehydrated using the electroosmotic dehydrator shown in Figs.
The amount of electricity required for this dehydration process was compared.

According to this test result, the conventional electroosmotic dehydrator (5th
In Figure), an applied voltage of 75 V is required to maintain stable electroosmotic dehydration, and the power consumption is -H/
On the other hand, in an electroosmotic dehydrator (Fig. 1) in which strings are attached around a rotating drum at intervals of 70 mm, the applied voltage is 60 g (dehydrated sludge cake).
Stable electroosmotic dehydration can be maintained at V, and power consumption is 0.
．． It was 3KWH/Kg (dehydrated sludge cake).

In other words, the applied voltage can be lowered by 15V compared to the conventional method, and the power consumption required for sludge dewatering treatment is also significantly reduced by 1! It was confirmed that ff could be reduced. Also, visual observation did not show that the string's degassing passage was clogged with sludge during the dewatering process. Furthermore, during the dehydration process, it was confirmed that gas generated by electrolysis along with water vapor generated by heat generation was blown out through the gas vent passage of the string.

Example 2: Next, the example according to the second means of the present invention will be described as a third example.
In this embodiment shown in FIG. 1 and FIG. 4, an endless belt body with a square cross section made of synthetic rubber open-cell sponge with a pore diameter of about 50 to 100 μm is used as the string 8. A plurality of strings 8 arranged at intervals in the width direction of the rotating drum 1 are stretched between the rotating drum 1 and the pulley 7. In addition, the cross section of this string 8, especially its thickness in the height direction, is such that when loaded in the machine, the outer end surface is the press belt 2 with the mating electrode.
The height h of the sludge passage is set to be larger than the height h of the sludge passage so that it comes into contact with the filter belts 3 stacked on top of each other. Note that the string 8 is attached at a pitch of approximately 70 g+m.

Therefore, the gas generated on the surface of the electrode 1a by electrolysis of sludge-containing water during the electroosmosis process of the sludge 5 migrates to the porous string 8 disposed in the vicinity and fills the internal pores of the string 8. It diffuses and is removed from its end face to the atmosphere through the filter belt 3. As a result, no generated gas remains between the electrode surface of the rotating drum 1 and the sludge 5, and an increase in contact electrical resistance between the electrode 18 and the sludge 5 due to residual gas is avoided, resulting in high conductivity. The quality can be ensured.

In addition, regarding this example, the previous examples (Fig. 1, 2
Even though the results of a test similar to the evaluation test described in Fig.
It has been confirmed that effects such as road spacing can be obtained in terms of applied voltage and power consumption.

〔Effect of the invention〕

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

In other words, a string that provides a degassing function is installed in the sludge passage between the opposing electrodes, and the gas generated between the sludge and the non-water collection side electrode remains in place due to the electrolysis action during the electroosmotic dehydration process. By eliminating the residual gas from the system, it is possible to avoid an increase in electrical resistance at the contact surface between the electrode and the sludge due to residual gas, and maintain high conductivity. High dewatering efficiency can be achieved by reducing power consumption required for sludge dewatering.

[Brief explanation of the drawing]

FIGS. 1 and 3 are overall configuration diagrams of different embodiments of the present invention, and FIGS. 2 and 4 are FIG. 1, respectively. Fig. 3 is an enlarged cross-sectional view of the sludge passage section, Fig. 5 is an overall configuration diagram of a conventional electroosmotic dehydrator, and Fig. 6 is an enlarged cross-sectional view of the sludge passage section.
In Figure 0, which is an enlarged cross-sectional view of the sludge passage section in the figure, there are 18 rotating drums, la: electrode (non-water collection side electrode), 2 nibbles belt (water collection side electrode), 3: filter belt (filtration member), 4 is the source, 5: sludge, 6: string, 6a: gas vent passage, 8: gas permeability 1.・,-7 Figure 3

Claims (1)

[Claims] 1) A voltage is applied between the anode and cathode electrodes that face each other across the sludge passage, and the water contained in the sludge supplied to the sludge passage is collected on one electrode side by electroosmosis. In an electroosmotic dehydrator that drains filtrate out of the system through a filtration member, a string is installed on the non-water collection side of the electrode to form a degassing passage between the surface of the electrode and the sludge. An electroosmosis system, characterized in that it is installed both inside and outside the sludge passageway, and gas generated between the non-water collection side electrode and the sludge during the electroosmosis process is removed from the system through the gas venting passageway. Type dehydrator. 2) A voltage is applied between the anode and cathode electrodes that face each other across the sludge passage, and the water contained in the sludge supplied to the sludge passage is collected on one electrode side by electroosmotic action, and then is deposited on the electrode surface. In an electroosmotic dehydrator in which filtrate is drained out of the system through a filtration member provided, a string with gas permeability is laid across the sludge passage and between opposing electrodes, and the string is Electroosmosis characterized in that the gas generated between the non-water collection side electrode and the sludge is guided through the internal pores of the string to a filtering member provided on the water collection side electrode, and is eliminated from the system from there. Type dehydrator.