JPS62197115A - Electrode of electroosmotic type dehydrator - Google Patents

Abstract

PURPOSE:To obtain mechanical strength and abrasion resistance capable of sufficiently withstanding slip squeezing load, by reducing the consumption of an anode due to an elution caused by current supply by constituting the electrode surface of the anode of a bonded body of lead dioxide particles. CONSTITUTION:An electrode segment 1a is used in a state mounted to the peripheral surface of the anode side rotary drum 1 of an electroosmotic type dehydrator. The electrode segment 1a is a short strip like plate having both flat front and back surfaces and a large number of the electrode segments 1a are arranged on the peripheral surface of the rotary drum 1, of which the outer peripheral surface forms a polyhedral flat surface, in parallel and clamped thereto by screws. The electrode surface of each electrode segment 1a is formed of a bonded body of lead oxide particles and this anode surface is formed by a method wherein a lead nitrate or lead sulfate solution is used as an electrolyte bath and the bonded body of the lead oxide particles is electrodeposited to the surface of an electrode substrate by anodic oxidation to cover said surface or a method wherein a lead oxide powder is bonded to the electrode substrate by a pressure molding method to cover said substrate. By this method, an electrode reduced in consumption due to an elution caused by current supply and excellent in durability and abrasion resistance is obtained.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

This invention uses surplus sludge generated in sewage treatment plants or slurry-like sludge generated in food and other industrial fields as the material to be dehydrated, and simultaneously applies electroosmosis and pressure filtration to the material to be dehydrated. The present invention relates to an electrode for an electroosmotic dehydrator that performs dehydration treatment.

[Prior art and its problems]

First, in Fig. 3, which explains the outline of the electroosmotic dehydrator to which the present invention is applied, reference numeral 1 denotes a rotating drum having an anode side electrode 1a attached to its outer circumferential surface. A press belt 3, which also serves as a cathode electrode and overlapped with a filter belt 2, is disposed facing the area, and a slurry squeezing passage 4 is defined on the surface facing the rotating drum 1. Further, the press belt 3 is stretched between sprockets 58 to 5d, and a press device 6 is provided behind the slurry squeezing passage 4. Furthermore, 7 is a drive motor, 8 is a slurry supply hopper installed on the entrance side of the road 4, 9 is a filtered water tray, 10 is a scraper for separating dehydrated cakes installed on the exit side of the passage 4, and furthermore, the above-mentioned anode side A DC power supply device 1 is installed between the rotating drum 1 and the press belt 3 on the cathode side.
1 is connected. The anode side electrode 1a is made up of strip-shaped electrode segments arranged and fixed on the circumferential surface of the rotating drum 1. With the above configuration, when the slurry 12 is supplied into the slurry squeezing passage 4 through the hopper 8 with voltage applied from the power supply 11, the slurry 12 is sandwiched between the rotating drum 1 and the filter belt 2, and exits the passage. It is transported toward the side in the direction of arrow P. During this transport process, in addition to mechanical squeezing force, electroosmotic dehydration is applied to the slurry 12 by an electric field formed between opposing electrodes. As a result, the water contained in the slurry becomes positively charged and flows toward the cathode, and as it is discharged on the cathode side, it passes through Gt 2 and is dehydrated and filtered, and then drained out of the system through the filtered water receiver 9. It is processed. On the other hand, the dewatered slurry in the road 4 has a low moisture content and is turned into a cake, and the dehydrated cake 13 is passed through the scraper 10 from the exit side of the passage 4.
After being separated and collected, it is incinerated or composted and reused as fertilizer. Conventionally, an electrode made of metal such as stainless steel, nickel steel, or mild steel is generally used as the anode electrode 1a of an electroosmotic dehydrator. However, according to knowledge obtained from operating results of electroosmotic dehydrators, it has become clear that anode electrodes made of these materials have the following drawbacks. That is, when an anode electrode made of the above material is energized, its constituent components are ionized and eluted into the slurry, and the electrode wears out over time. Moreover, since the amount of elution is large, the life of the electrode is short, and the electrode must be replaced with a new one after a relatively short period of operation, making maintenance and management time-consuming. Furthermore, with electrodes made of stainless steel, nickel steel, etc., there is a risk that heavy metal ions eluted from the electrodes when energized may mix into the dehydrated material and filtrate, causing secondary pollution. Although noble metals such as platinum have excellent insolubility properties for the same electrode materials, they are expensive and cannot be used for practical use. Carbon electrodes have also been tried, but carbon electrodes are not as good as metal electrodes. Although the amount of elution and consumption of the electrode is smaller than that, it has a disadvantage that it has a high specific resistance, low current carrying properties, and weak mechanical strength, so it is often damaged by the compressing load during use. In addition, when the electrodes of an electroosmotic dehydrator wear out as mentioned above, the distance between the opposing electrodes (anode and cathode) changes slightly, and if left as is, it will not be possible to maintain efficiency over a long period of time. Electroosmotic dehydration becomes difficult to maintain. Conventionally, this was dealt with by changing the power supply voltage and other energizing conditions during long-term operation, readjusting the distance between the electrodes, or replacing the electrodes with new ones. However, the operation of the dehydrator must be interrupted each time, resulting in a decrease in operating efficiency. As described above, the characteristics of the electrodes, especially their electrochemical durability, play a large role in maintaining the operational performance of electroosmotic dehydrators, and from this perspective, selection and improvement of electrode materials are extremely important issues. It becomes.

[Purpose of the invention]

This invention has been made in consideration of the above points, and has solved the above-mentioned problems by reducing elution and consumption due to energization, and also has electrical and mechanical characteristics required for electrodes of electroosmotic dehydrators. The purpose is to provide a highly durable anode electrode that can provide sufficient cleanliness.

[Key points of the invention]

In order to achieve the above object, the present invention has an electrode surface of an anode made of a combination of lead dioxide particles, thereby providing high electrochemical and mechanical durability as an electrode for an electroosmotic dehydrator. This is to obtain an anode electrode. This combination of lead dioxide particles can be formed by electrodeposition on the surface of the electrode base of the anode using a lead nitrate solution or lead sulfate solution in an electrolytic bath, or it can be formed by pressure molding lead dioxide powder. can do.

[Embodiments of the invention]

Examples of this invention will be described below. First, Figure 1. FIG. 2 shows an electrode segment of an anode side electrode according to an embodiment of the present invention, and the electrode segment 1a is used by being mounted on the circumferential surface of the anode side rotating drum 1 of the electroosmotic dehydrator shown in FIG. The electrode segments (la) are formed as rectangular plates with flat front and back surfaces, and are arranged and fastened with screws on the circumferential surface of the rotating drum 1 whose outer circumferential surface is a polygonal flat surface. . Here, the electrode segment 1a has an electrode surface configured as a combination of lead dioxide particles. The manufacturing method for such an anode electrode is to bond lead dioxide particles to the surface of an electrode base made in advance into a rectangular shape as shown in Figures 1 and 2 by anodic oxidation using a lead nitrate or lead sulfate solution in an electrolytic bath. The electrode body is formed by electrodeposition, or the electrode base is coated with lead dioxide powder by a pressure molding method. By employing such a manufacturing method, almost no mechanical processing is required for the combined body of lead dioxide particles, which is advantageous. Next, in order to evaluate the characteristics of the above-mentioned anode electrode, the inventors will discuss the results of an experiment on the electrode wear characteristics associated with energization for electroosmotic dehydration in comparison with anode electrodes made of other materials. In this experiment, electrodes made of various materials were installed in a batch-type electroosmotic dehydration device, and after performing electroosmotic dehydration for a predetermined period of time, the electrodes were taken out and weighed, and the amount of current applied was compared to the initial weight. The amount of elution consumption of the electrode was calculated. Here, the material composition of the various electrodes used in the above experiment is indicated on the sample side, and Table 1 shows the wear characteristics of each sample obtained from the electroosmotic dehydration experiment results. Note that the number subscripted to the compositional component of each sample represents the weight percent of that component. Sample 1: Stainless steel 5US304 (Fe 70.
Cr 19.5°Ni 10. CO, 0B) Sample 2 Stainless steel 5US430 (Fe 82.
Cr 1B) Sample 3: Nickel steel (Ni 100) Sample 4: Titanium steel (Ti 100) Sample 5 = Inconel 600 (Nl 76, Cr 1
6. Fe7.2゜11n O,2,310,2,C
o 0.1) Sample 6: Incoloy 800 (N132
．． Fe 46. Cr2O, 6°31 0.35.
Cu O, 27, CO, 04) Sample 7: Combined lead dioxide particles (Pb 100) For sample 7, a titanium plate with a titanium expanded band spot welded was used as the electrode base, and the electrode of this electrode base was The surface was plated with platinum and lead dioxide was electrodeposited on top. Table 1 As is clear from the experimental results in Table 1 above, each sample 1
7, the lead dioxide particle bond shown in sample 7 had a very small amount of weight loss compared to other samples 1 to 6, and was recognized to have high electrochemical corrosion resistance. In addition, lead dioxide will be eluted from the electrode in an amount commensurate with this slight weight loss and will be mixed into the dehydrated material and reduced water, but the amount will be lower than the amount normally contained in nature. The amount is small, and the generation of secondary pollution caused by the operation of the electroosmotic dehydrator can be almost ignored. In addition, the mechanical strength of the lead dioxide particle combination is 5 to 6 on the Mohs scale, and it can withstand the compressive load applied to the electrode when used in the electroosmotic dehydrator shown in Figure 3. It can be seen that the strength and abrasion resistance can be obtained. On the other hand, based on the above experimental results, the present inventor further confirmed the practicality of the anode side electrode made of a combination of lead dioxide particles by replacing the electrode segment (la) in Figs. An actual machine test was carried out by mounting it on the circumferential surface of the rotating drum 1 of the electroosmotic dehydrator shown in the figure. As for this electrode segment 1a, □A titanium plate is used as the anode electrode base as in the case of the basic experiment described above, a titanium expanded band net is fixed to the electrode surface side of this titanium plate by spot welding, and further platinum plated. After that, a composite of lead dioxide particles was applied by electrodeposition. The purpose of fixing the titanium expanded band net here is to increase the bonding strength between the lead dioxide particle combination and the electrode base on the electrode surface, and the platinum plating prevents the oxidation of titanium, which is the material of the electrode base. This is to maintain high electrical conductivity between the lead dioxide particle bond and the electrode base. Additionally, the rotating drum of the electroosmotic dehydrator used in this test had a diameter of 69 cm+. The drum width was 26 clll, and the test operating conditions were that the slurry concentration as the material to be dehydrated was 20%, the current supplied from the power supply was 9OA, and the dehydration treatment time was 100 hours. According to the results of an electroosmotic dehydration test under these conditions,
The slurry could be dehydrated to a water content of 60-65%. Furthermore, after the test, the electrode segment on the anode side was removed from the rotating drum and inspected, and no mechanical damage was observed. The total weight was 6.2g. On the other hand, the total outer surface area of the rotating drum is 56 d-, but the area of the dehydration region facing the cathode side electrode is 25 dnf, which is less than half of the total surface area, so the average current density is 90 A/25 dnf-3. ,6A
/drrf. Furthermore, the effective time during which each electrode segment actually participates in electroosmotic dehydration is the time during which the electrode passes through the area of the slurry passage as the rotating drum rotates, and therefore the effective time of the anode side electrode for 100 hours of operation of the dehydrator The operating time is (area of dehydration area/total surface area of electrode) x operating time = (
25d ryr156d rrr) X 100Hr
#44.6 hours. Therefore, the weight reduction of the anode electrode per unit current and unit operation time is 6.2 from the above-mentioned total weight consumption of 6.2 g, supply current of 90 A, and effective operating time of 44.6 ■r.
g/90A X 44.6Hr-1,511g/A
-Hr-d rrl. Note that the values calculated by this calculation are somewhat larger than the experimental results shown in Table 1, but this is presumably due to the difference between the batch processing method and the continuous processing method. On the other hand, based on the weight consumption of the electrode of 6.2 g under the operating conditions of the dehydrator described above, the specific gravity of the combined body of lead dioxide particles was determined to be 9.
．． According to the calculation of the thickness reduction of each electrode segment assuming that the dehydrator is operated continuously throughout the year at 8g/cd, the thickness reduction is only 2.2m.
m. Moreover, if the thickness of the anode electrode decreases to this extent during continuous operation throughout the year, the increase in the gap between the opposing electrodes and the cathode will be negligible. It is possible to maintain high electroosmotic dewatering performance throughout the year without taking special measures such as readjusting the slurry passage gap or replacing the anode electrode segment. Note that the amount of electrode thickness reduction described above is when the current density is 3.6 A/dnf, and if the operating conditions of the dehydrator are set lower than this current density, the anode electrode thickness will be further reduced. The amount of wear and thickness reduction is reduced, making it possible to further extend the life of the electrode.

【Effect of the invention】

As described above, according to the present invention, by configuring the electrode surface of the anode side electrode incorporated in the electroosmotic dehydrator as a combination of lead dioxide particles, (1) the anode side electrode when energized Since the amount of elution consumption is small, it is possible to maintain high electroosmotic dehydration performance without replacing the electrodes and operate continuously for a long period of time, which increases the reliability and operation rate of the electroosmotic dehydrator. . (2) The amount of the lead dioxide particle bond that is the electrode material elutes during electroosmotic dehydration operation is negligible, so the amount of electrode consumption is likely to be mixed into the dehydrated material and filtered water. There is also little risk of secondary pollution occurring. (3) The combined body of lead dioxide particles has high mechanical strength and wear resistance, and can sufficiently withstand the slurry squeezing load applied to the electrode during dehydration operation. (4) A bond of lead dioxide particles can be deposited on the electrode surface of the electrode base by electrodeposition or pressure molding, and a large-area electrode can be easily produced. It is possible to provide a highly durable electrode that fully satisfies the mechanical and electrical properties required for the anode side electrode of an electroosmotic dehydrator.

[Brief explanation of drawings]

FIG. 1 is a plan view of an electrode segment of an anode side electrode according to an embodiment of the present invention, FIG. 2 is a sectional view taken along arrow nn in FIG.
FIG. 3 is a block diagram of a continuous treatment type electroosmotic dehydrator. In each figure, 1: a rotating drum on the anode side, 1a: an electrode segment, 3: a press belt that also serves as a cathode side electrode,
4: Slurry passageway, 11: Power supply device, 12: Figure 1 as material to be dehydrated

Claims (1)

[Scope of Claims] 1) An electroosmotic dehydrator that supplies a material to be dehydrated between opposing electrodes, an anode and a cathode, and applies a DC voltage between the electrodes to dewater and filtrate the material to be dehydrated. An electrode for an electroosmotic dehydrator, characterized in that the electrode surface of the anode side electrode is made of a combination of lead dioxide particles. 2) The electrode according to claim 1, characterized in that a bond of lead dioxide particles is formed on the electrode surface of the anode side electrode substrate by electrodeposition using a lead nitrate solution or a lead sulfate solution as an electrolytic bath. electrodes for electroosmotic dehydration machines. 3) In the electrode according to claim 2, the electrode base is a titanium plate, and a titanium expanded band net is spot welded and fixed to the electrode surface side, and further platinum plating is applied, and the electrode surface is plated with platinum. An electrode for an electroosmotic dehydrator characterized by having lead dioxide particles electrodeposited on the electrode. 4) The electrode according to claim 1, characterized in that lead dioxide powder is bound to the electrode surface of the anode side electrode base by a pressure molding method to form a combined body of lead dioxide particles. Electroosmotic dehydrator electrode.