JP3321612B2 - Combination structure of electrodes of electroosmotic dehydrator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combination structure of electrodes used in an apparatus for dewatering and / or washing sludge by electroosmosis.

[0002]

2. Description of the Related Art Conventionally, an electroosmosis method has been used for dehydrating and / or washing inorganic and organic sludge having a high degree of difficulty in dewatering.
In the dehydration treatment using the electroosmosis method, a DC voltage is applied between electrodes provided in the sludge to be treated, utilizing the fact that particles in the sludge are charged to a negative potential with respect to water (zeta potential). As a result, the moisture charged to the positive potential is moved to the negative electrode side, and the sludge is dehydrated and / or washed.

[0003]

In this case, the electrode used in this case is a flat plate made of a metal or carbon having good electrical conductivity,
Cylindrical and rod-like bodies are used, with the opposing surfaces of the positive and negative electrodes parallel to each other. However, in this method, the electrodes necessary for increasing the amount of electricity when a constant voltage is applied,
In particular, there is a limit in securing the area of the positive electrode, and a long time is required for sludge treatment.

That is, among these positive and negative electrodes, the negative electrode disposed on the bottom surface of the sludge treatment area makes strict and uniform contact with the sludge due to the pressure of the sludge and the moisture separated downward, but is disposed on the upper surface. The positive electrode does not always contact uniformly depending on the properties of the sludge, and the effective area of the electrode is not sufficiently ensured. This tendency is particularly remarkable when dehydration proceeds and the upper part of the sludge treatment area is dried by heating at the time of energization, and in some cases, the upper surface of the sludge separates from the positive electrode and substantially no energization is performed. .

An object of the present invention has been made in view of the above-mentioned problems of the prior art, and it has been proposed to increase the area of the positive electrode and to improve the combination position with respect to the negative electrode to improve the current efficiency and dehydration efficiency in the dehydration treatment by electroosmosis. Another object of the present invention is to provide a combined structure of positive and negative electrodes of an electroosmotic dewatering apparatus for improving the transfer efficiency of cleaning water in cleaning contaminated sludge.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to apply a DC voltage between a positive electrode and a negative electrode which are opposed to each other on the top and bottom surfaces of a sludge treatment area, and apply a DC voltage to reduce the water content of the sludge. In the electrode used for the dehydration device to be lowered by permeation, a part of the positive electrode is disposed so as to be opposed to the negative electrode located at the bottom of the processing area in a direction perpendicular to the negative electrode. This is achieved by the electrode combination structure of the electroosmotic dehydrator described above.
In addition, in the sludge treatment by the electroosmosis method, in addition to the usual dewatering of sludge, a treatment of removing harmful substances in sludge by washing water or dewatering simultaneously with washing is also known. Includes both of these processes.

[0007]

According to the present invention, sludge dewatering by electroosmosis and / or
Alternatively, in a cleaning apparatus for contaminated sludge, a DC voltage is applied between a negative electrode installed on the bottom surface of the treatment area and a positive electrode arranged so that a part of the negative electrode protrudes vertically and faces the negative electrode. Is applied, and the water in the sludge positively charged with respect to the soil particles and / or the water supplied to the sludge is transferred to the negative electrode side, so that the sludge is dehydrated or washed.

Here, as shown in FIGS. 1A, 1B and 1C, a negative electrode I disposed horizontally and a positive electrode II are disposed.
In contrast to the case where A is combined in parallel as in the conventional case (FIG. 1A), the case where a part of the positive electrode protrudes in the vertical direction and opposes, for example, as shown in FIG. 1B is a comb-shaped positive electrode IIB and FIG. A corrugated positive electrode IIC is conceivable.

In the case of the electrode structure shown in FIG. 1A, when the positive electrode IA parallel to the negative electrode II contacts the upper surface of the sludge, the contact is not always safe and uniform as shown in the figure. It becomes more noticeable as the upper part of the sludge dries. Therefore, in the conventional electrode structure, the effective contact area of the positive electrode decreases, and a sufficient amount of current cannot be secured.

On the other hand, for example, the vertical portion of the present invention IB shown in FIG. 1B penetrates into the sludge S, and both surfaces thereof sufficiently contact the sludge, so that a large contact area is obtained.

Also in the case of the corrugated electrode structure shown in FIG. 1C, when the positive electrode IIC is placed on the upper surface of the sludge, the downward slope is pressed against the sludge surface to obtain sufficient contact. A large effective contact area is obtained, and in the case of FIGS. 1B and 1C, dehydration is performed in a short time by a large amount of electricity.

In this case, the increase in the amount of electricity in each of the electrode structures shown in FIGS. 1B and 1C is larger than the increase rate of the electrode area, as will be described in an embodiment described later. Although the reason is not always clear, in the usual electroosmotic dewatering equipment, the sludge to be treated is dewatered by gravity, and in the initial stage of the treatment, the sludge is already in a state perpendicular to the moisture in the sludge treatment area. Distribution has occurred. In such a case, in the case of the conventional parallel arrangement of the positive and negative electrodes, the electrical resistance increases in the upper part of the sludge with a small amount of moisture in the processing target area, and the amount of current as a whole is restricted in this part. On the other hand, in the present invention, in addition to the increase in the electrode area of the positive electrode, the positive electrode has a portion (comb-shaped portion and a lower portion of the waveform) which protrudes vertically and opposes the negative electrode. In the lower part of the processing area having a large amount of water, a dehydration action occurs due to a large current density between these opposed parts and the negative electrode, thereby increasing the amount of electricity as a whole, and achieving efficient and uniform dehydration. It is thought to occur.

Further, in FIGS. 1B and 1C, the area of the positive electrode is larger than that of the negative electrode. Therefore, when a constant current is applied between the positive and negative electrodes, the current density is below the area to be treated with high sludge moisture. It is thought that the dehydration by energization is performed evenly through the upper and lower portions of the processing target area, and therefore the substantial dehydration time as a whole is further reduced. .

In the dehydration by electroosmosis, dehydration occurs due to the negative charging of the water and the soil particles due to the application of a voltage between the positive and negative electrodes. This phenomenon occurs at a much lower voltage than in ordinary electrolysis. By increasing the voltage, the dehydration effect also increases, but if the voltage exceeds the electrolysis voltage of the sludge as an electrolyte, electrolysis raises the pH potential of the sludge, especially near the negative electrode, preventing the dewatering effect by electroosmosis. Can be For this reason, the applied voltage needs to be low enough that it is sufficient for electroosmosis but does not substantially cause electrolysis, and the applied voltage during sludge dewatering and / or washing is about 0 with respect to the distance between the electrodes. It is preferably set to 0.1 to 1.0 V / cm (1 to 10 cm / V).

[0015] In the case of a conventional parallel-arranged structural electrode,
The sludge on the side of the treated area that is in contact with the positive electrode is in a dry state due to heat generated by the current-carrying resistance, causing partial exfoliation between the sludge and the positive electrode surface. May not be performed substantially.

However, in the electrode combination structure of the present invention, since the dehydration proceeds uniformly as described above, only the sludge above the area to be treated does not become dry, and the structure of the electrode is comb-like. In order to take a three-dimensional form having a vertical component partially like a mold or a wavy shape, a sludge portion is tightly held between adjacent inclined surfaces or vertical surfaces of the positive electrode, and sludge is discharged from the positive electrode surface. The risk of peeling is reduced.

The positive electrode in the present invention is shown in FIG.
Various types other than the comb type and the corrugated type shown in B and C are possible, and these positive electrodes can be of various sizes and shapes pre-assembled in advance and can be attached to and detached from the sludge dewatering tank according to the intended use. It is preferable to keep it.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments shown in the drawings. FIG. 2 is an explanatory view showing an outline of a sludge dewatering and / or washing apparatus to which the present invention is applied.

In FIG. 2, a 450 mm × 450 mm × 10 mm negative electrode iron plate 2 is horizontally installed at the bottom of a sludge dewatering tank 1 of 500 mm × 500 mm × 500 mm. On the other hand, a positive electrode (illustrated in an enlarged manner in the height direction) having the following dimensions and shapes with an average inter-electrode distance of 300 mm is provided above the dewatering tank 1 so as to be replaceable and removable.

(1) 450 arranged in parallel with the negative electrode 2
mm (width) x 450 mm (length) x 10 mm (thick) positive iron plate 2
A (conventional example: indicated by the dashed line in the figure), (2) 450 mm (width)
A positive electrode plate 3B in which five vertical plates having a height of 50 mm are arranged at equal intervals in the length direction and perpendicular to the negative electrode 2 on an iron plate of x450 mm (length) x 10 mm (thickness) (Example of the present invention: 450 mm (width) x 450 mm (projection length) x with a uniform pitch continuous waveform in the longitudinal direction with an apex angle of 80 °
Positive electrode 3C in which a 10 mm (thick) iron plate is arranged with respect to the negative electrode iron plate 2 with the waveform downward, (Example of the present invention: shown by a dotted line in the figure).

The (-) and (+) terminals of a DC power supply 4 are connected to the negative electrode 2 and the positive electrode 3, respectively. A valve 6 is provided. In other figures, 7
Is a cleaning liquid tank for supplying a cleaning liquid to the dewatering tank 1 when the electroosmosis apparatus is used as a sludge cleaning processing apparatus;
Denotes a regulator of the supply pressure, and 9 denotes a liquid feed pipe.

Example 1 The dewatering tank 1 was filled with 75 kg of sewage sludge having a water content of 84%, and the positive electrodes 3A (conventional example), 3B and 3C were used for each experiment.
The present invention was exchanged and mounted, and a current was supplied from the DC power supply 4 at a constant voltage of 15 V, and a sludge dewatering process by electroosmosis was performed with a target point at which the current value decreased to 0.3 A. Table 1 shows the results.

[0023]

(A) (B) (C) Distance between electrodes 300 mm 300 mm 300 mm Power supply voltage (V) 15 V 15 V 15 V Initial current value (A) 3.0 A 6.0 A 8.2 A Final current value (A) ) 0.3A 0.3A 0.3A Dehydration (energization) time 24 hr 15 hr 12 hr Initial sludge water content 84% 84% 84% Final sludge water content 77% 65% 62% Dewatering amount 22.88 kg 40.72 kg 43 .42 kg Final sludge weight 52.12 kg 34.28 kg 31.58 kg

As is clear from the experimental results shown in Table 1, as compared with the conventional electrode structure corresponding to FIG. 1A in which the positive and negative electrodes are arranged in parallel, for example, the electrode combination structure of the present invention corresponding to FIG. When the positive electrode 3B is used, the initial current value increases about twice, the time required until the final setting processing time is reduced to about 38%, and the dehydration amount at that time increases by about 80% or more. ing.

Such an effect becomes more remarkable when the shape of the positive electrode is corrugated 3C corresponding to FIG. 1C. This is presumably because the slanted portion of the positive electrode 3C in the vertical direction with respect to the sludge to be treated in the tank 1 more uniformly responds to each portion by the corrugated structure, so that the energizing action is more uniformly applied.

Example 2 The treatment tank 1 was filled with 100 kg of contaminated sludge having a water content of 25%, washing water was supplied from a washing liquid tank 7 through a pipe 9, and the positive electrodes 3A, 3B and 3C used in Example 1 were connected to each other. It was installed while replacing, and a direct current was supplied to perform dehydration washing.

The results are shown in Table 2. Note that, in Table 2, the blank column shows the results of washing with only water passing for the same time as the electroosmotic washing time.

[0028]

[Table 2] Blank (A) (B) (C) Distance between electrodes 300 mm 300 mm 300 mm 300 mm Voltage -15 V 15 V 15 V Current-0.4 A 0.8 A 1.1 A (initial to final constant) Unit time Water flow 175 ml / hr 760 ml / hr 1020 ml / hr 1250 ml / hr Water flow (energization) time 24 hr 24 hr 24 hr 24 hr Total water flow 4,200 ml 18,240 ml 24,480 ml 30,000 ml

As shown in Table 2, the current value of the electrode structure 3B according to the present invention is twice that of the conventional electrode and 3A when the positive and negative electrodes are opposed to each other in the washing of contaminated sludge by electroosmosis. The amount of water per unit time increased by about 1/3. Further, as in the case of the first embodiment, the above-mentioned effect becomes more remarkable when the positive electrode is a corrugated 3C.

Example 3 A sludge dewatering experiment was conducted in the same manner as in Example 1 except that the dimensions and shape of the sludge dewatering tank were set to 500 × 500 × 800 mm and the distance between the electrodes was set to 600 mm. Table 3 shows the results.

[0031]

(A) (B) (C) Distance between electrodes 600 mm 600 mm 600 mm Power supply voltage (V) 15 V 15 V 15 V Initial current value (A) 1.8 A 4.2 A 6.8 A Final current value (A) 0.3A 0.3A 0.3A Dewatering (energization) time 46 hr 24 hr 22 hr Initial sludge water content 84% 84% 84% Final sludge water content 80% 67% 65% Dewatering amount 30kg 77kg 69kg Final sludge weight 120kg 73kg 69kg

Example 4 Using the same sludge dewatering tank and electrode structure as in Example 3, the same cleaning experiment as in Example 2 was performed. Table 3 shows the results.

[0033]

[Table 4] Blank (A) (B) (C) Distance between electrodes-600 mm 600 mm 600 mm Voltage-15 V 15 V 15 V Current-0.2 A 0.6 A 0.9 A (initial to final constant) Unit time pass Water volume 180 ml / hr 670 ml / hr 985 ml / hr 1210 ml / hr Water flow (energization) time 24 hr 24 hr 24 hr 24 hr Total water flow 4,300 ml 16,080 ml 23,640 ml 29,040 ml

[0034]

As described above, according to the present invention, when dewatering sludge by electro-osmosis or washing contaminated sludge, a part of the positive electrode combined with the negative electrode horizontally arranged at the bottom of the dewatering tank is moved vertically. Since it has a shape that protrudes into, for example, a comb shape or a corrugated shape, the effective contact area of the electrode at the time of energization is increased, and dehydration or water flow by energization in each part of the processing area is uniformized, As a result, the time for the dehydration or washing process is significantly reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the operation of an electrode combination structure according to the present invention.

FIG. 2 is an explanatory view showing an outline of a sludge dewatering and / or washing device by electroosmosis using the electrode combination structure of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sludge dewatering / washing tank 2 ... Negative electrode 3A, 3B, 3C ... Positive electrode 4 ... DC power supply 5 ... Drain pipe 6 ... Drain valve 7 ... Cleaning liquid tank 8 ... Pressure regulator 9 ... Liquid feed pipe

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 35/06 B01D 61/56 C02F 11/12

Claims (5)

(57) [Claims] 1. An electrode used in a dehydrator for applying a DC voltage between a positive electrode and a negative electrode which are opposed to each other on an upper surface and a bottom surface of a sludge treatment area and are parallel to each other to reduce the water content of the sludge by electroosmosis. The electrode combination of the electroosmotic dehydration apparatus, wherein a part of the positive electrode is disposed so as to project perpendicularly to the negative electrode and face the negative electrode located at the bottom of the processing target area. Construction. 2. The electrode combination structure for an electroosmotic dehydrator according to claim 1, wherein the positive electrode is formed in a comb shape so that a part of the positive electrode protrudes from the negative electrode. 3. The electrode combination structure for an electroosmotic dehydrator according to claim 1, wherein the positive electrode is formed in a corrugated shape so that a part of the positive electrode projects from the negative electrode. 4. The electrode combination structure for an electroosmotic dehydrator according to claim 1, wherein the average distance between the positive and negative electrodes is maintained at 1 to 10 cm / V with respect to the applied voltage. 5. The electrode combination structure for an electroosmotic dehydrator according to claim 1, wherein the positive electrode is integrally combined and detachable from the electroosmotic device.