JP3533538B2 - Double tube type ozonizer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double tube type ozonizer mainly used in the field of water treatment.

[0002]

2. Description of the Related Art The structure of a conventional double-tube type ozonizer is shown in the schematic sectional view of FIG. FIG. 5A is a cross-sectional view of the double-tube ozonizer viewed from the side, and FIG. 5B is a cross-sectional view of the double-tube ozonizer viewed from a direction perpendicular to the side. In FIGS. 5A and 5B, this double-tube ozonizer has a cylindrical stainless steel casing 1, and a stainless steel cylindrical ground electrode 2 is provided inside the casing 1. Glass 3 as a dielectric layer is closely attached to the inner surface of the ground electrode 2 concentrically, and both ends of the ground electrode 2 and the dielectric layer 3 are also fixed to the housing 1. Further, in the center of this ozone generating tube, a cylindrical high-voltage electrode 4 made of stainless steel is concentrically arranged with the surface of the glass 3 and the discharge space 5 separated from each other. Extends to the outside of the housing 1 and is connected to one end of the housing 1 through a bushing 6 and a high frequency power supply 7. High voltage electrode 4
In order to flow the cooling water 8 indicated by an arrow at both ends of the, a thin tube covered with an insulating tube 9 is provided in the ozone generation tube, and this thin tube projects from the housing 1. The cooling water 8 is also circulated from a part of the housing 1 to cool the ground electrode 2. The high-voltage electrode 4 has a diameter of 60 mm, the total length is 1000 mm, and the discharge space 5 is 1 mm.
Is.

From one end of the discharge space 5 of the device having such a structure, the source gas 10 of air or oxygen indicated by an arrow is drawn.
Is supplied and the gas pressure is 1.5 atm, and a voltage is applied between the ground electrode 2 and the high voltage electrode 4 by the high frequency power source 7,
Silent discharge occurs, and ozone 11 indicated by a dotted arrow can be generated from the other end of the discharge space 5.

[0004]

With the sophistication of the water treatment equipment in which the ozone generator is used, there is an increasing need to increase the ozone concentration. In order to increase the ozone concentration, it is common to increase the injection power, but when the injection power exceeds a certain value, the temperature of the high-voltage electrode 4 rises due to heating, ozone is decomposed, and the ozone concentration is low. There is a problem that ozone is saturated and it is not possible to generate high-concentration ozone. One of the causes is that, when the high voltage electrode 4 made of stainless steel is left as it is, contaminants are attached to the surface and a stable oxide film is not formed, so that the discharge is not sufficiently performed. Is.

The present invention has been made in view of the above points, and an object thereof is to maintain a stable discharge by cleaning the surface of a high voltage electrode to form a metal oxide film as a natural oxide film. , To provide a double-tube type ozonizer capable of generating high-concentration ozone.

[0006]

In order to solve the above problems, the ozonizer of the present invention is one in which a metal oxide film as a natural oxide film is formed on the surface of a high voltage electrode from which contaminants have been removed by polishing. The metal oxide film as a natural oxide film is formed after the surface of the high voltage electrode is electrolytically or mechanically polished to clean the surface.

[0007]

As described above, according to the present invention, the contaminants formed on the surface of the stainless steel high-voltage electrode which has been subjected to the drawing process or the like are removed by electrolytic polishing or mechanical polishing so that the form of the natural oxide film is not changed. By changing from a metal oxide film to a stable metal oxide film, the number of secondary electrons during discharge increases, the diameter of the discharge column increases, and the discharge is maintained stable even when the same electric power as before is injected. It is possible to generate a higher concentration of ozone compared to.

[0008]

EXAMPLES The present invention will be described below based on examples. Starting
Ming is to improve the high voltage electrode 4 of the ozonizer shown in FIG.
Therefore, a part of the high-voltage electrode 4 is illustrated and described here.
It FIG. 1A is a partial cross-sectional view of the high voltage electrode 4,
This shows how the surface of the electrode 4 is electrolytically polished. Electric
The cloth 13 in which the solution 12 is dipped is used as the electrode 15 of the constant voltage power supply 14.
It is fixed on the (cathode) and fixed between the high voltage electrode 4 and the power electrode 15.
If you trace the surface of the high-voltage electrode 4 while applying a voltage,
The piezoelectric electrode 4 can have a clean surface.
For example, in the electrolytic solution 12, phosphoric acid (H ₃PO_Four), Power supply
When -20V is applied to the electrode 15, the
The gray surface of the piezoelectric electrode 4 has a metallic luster.
It

FIG. 1 (b) is a partial cross-sectional view for explaining the action of electrolysis performed as described above. The high-voltage electrode 4 mainly uses a stainless steel drawing tube, and contaminants 16 such as oil and dust adhere to the surface of the high-voltage electrode 4 during its manufacturing process and assembly. At this time, when the surface of the high-voltage electrode 4 is brought into contact with the electrolytic solution 12 and a voltage is applied, the components of the high-voltage electrode 4 are dissolved out as + ions from the interface between the surface of the high-voltage electrode 4 and the contaminant 16 and the power electrode 15
It moves to the side (-) and the contaminant 16 is stripped off, so that the surface of the high voltage electrode 4 is exposed as a clean surface.

Further, in order to clean the surface of the high voltage electrode 4, the same effect can be obtained by mechanical polishing. FIG. 2 shows such a state, and FIG.
2B is a partial cross-sectional view seen from the side, and FIG. 2B is a front view seen from a right angle direction. As shown in FIGS. 2A and 2B, the abrasive 17 is brought into contact with the high-voltage electrode 4, and the high-voltage electrode 4 is rotated in the direction of the arrow [FIG.
By reciprocating in the longitudinal direction [Fig. 2 (a)],
The high voltage electrode 4 can obtain a clean surface. For example,
When the surface of the high-voltage electrode 4 having a diameter of about 70 mm and a length of 1000 mm is uniformly ground to a thickness of 0.1 mm, a metallic luster similar to that obtained by the above electrolytic polishing is obtained.

FIG. 3 is a partial cross-sectional view showing the discharge state in the discharge space 5 between the high-voltage electrode 4 whose surface is cleaned as described above and the ground electrode 2 to which the glass 3 is adhered. 3A shows the case of the present invention, and FIG. 3B shows the conventional case for comparison. The surface of the stainless steel is oxidized, and the natural oxide film 18 is formed during standing in both FIGS. 3 (a) and 3 (b), but their properties are different. As described above, the high-voltage electrode 4 is mainly a stainless steel drawn tube, but in the unprocessed state of FIG. 3 (b), oil or dust adheres to the surface and enters into the grain boundaries, and The component of the natural oxide film 18 formed on the surface afterward is mainly a compound of carbon and oxygen. On the other hand, in the case of the present invention in which the surface of the high-voltage electrode 4 is electrolytically or mechanically polished to expose a clean surface, that is, the natural oxide film 18 in FIG. 3A is a main component of stainless steel. Iron, chrome,
Formed from nickel metal oxide.

Since metal oxides generally have a smaller work function than pure metals, the number of secondary electrons generated from the cathode due to collision of oxygen ions during discharge increases. Therefore, the discharge column 1
The diameter of 9 is larger in FIG. 3 (a) than in FIG. 3 (b), and the discharge is stably maintained even when the same electric power is injected. In the case of the present invention, a higher concentration of ozone is generated than in the conventional case. be able to.

FIG. 4 is a diagram showing an increase in ozone concentration when the ozonizer of the present invention is used. The horizontal axis is the relative value of power density and the vertical axis is the ozone concentration. For comparison, a conventional ozonizer is used. The case where is used is also shown. In FIG. 4, the curve plotted with Δ shows the electrolytic polishing of the high-voltage electrode 4, the curve plotted with □ shows the same mechanical polishing, and the curve plotted with ◯ shows that the conventional untreated.

From FIG. 4, when the high voltage electrode 4 is untreated,
The ozone concentration tends to be saturated even if the electric power is increased. By electropolishing the same high-voltage electrode 4, the ozone concentration can be increased by 12% at the maximum power density, and the same high-voltage electrode 4 is mechanically polished. Also in this case, it can be seen that almost the same ozone concentration as that of electrolytic polishing can be obtained. The increase in ozone generation by up to 12% means that the number of ozonizers used is 1.
This is a 2% reduction. For example, in an apparatus that requires 600 ozonizers, 72 ozonizers can be reduced, and the present invention contributes to downsizing of the entire apparatus.

[0015]

EFFECTS OF THE INVENTION In the advanced treatment of wastewater by utilizing the strong oxidizing power of ozone, it is necessary to use a high concentration of ozone in order to perform it efficiently. However, if the injection power of the ozonizer is increased, a high concentration of ozone will be obtained. On the other hand, according to the present invention, the stainless steel high-voltage electrode surface of the double-tube type ozonizer is electrolytically or mechanically polished to be cleaned, and a metal oxide film as a natural oxide film is obtained. Since the surface of the high-voltage electrode is formed without the inclusion of foreign matter that accompanies conventional processing, high-concentration ozone can be obtained with the same electric power as before, and the amount of ozone generated also increases. Suitable for advanced water treatment,
There is an effect that the manufacturing cost is also reduced.

[Brief description of drawings]

FIG. 1 shows a high-voltage electrode used in the ozonizer of the present invention, (a) is a partial cross-sectional view showing a state of electrolytic polishing, (b).
Is a partial cross-sectional view explaining the function of electrolytic polishing

2A and 2B show a high-voltage electrode used in the ozonizer of the present invention, FIG. 2A is a partial cross-sectional view of a state of mechanical polishing seen from the side, and FIG. 2B is a front view seen from a direction perpendicular to the side view.

FIG. 3 shows the discharge space and discharge column of the ozonizer,
(A) is a partial sectional view showing the case of the present invention and (b) the conventional case.

FIG. 4 is a diagram showing the relationship between electric power and ozone concentration shown in comparison between the ozonizer of the present invention and a conventional ozonizer.

FIG. 5 shows a main part configuration of a conventional ozonizer, (a)
Is a cross-sectional view seen from the side, (b) is a cross-sectional view seen from a direction perpendicular to this

[Explanation of symbols]

1 case 2 Ground electrode 3 glass 4 High voltage electrode 5 discharge space 6 bushings 7 High frequency power supply 8 cooling water 9 Insulation tube 10 Raw material gas 11 ozone 12 Electrolyte 13 cloth 14 constant voltage power supply 15 electrodes 16 pollutants 17 Abrasive 18 Natural oxide film 19 discharge columns

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-2-245236 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C01B 13/11

Claims (3)

(57) [Claims] 1. A cylindrical ground electrode having a dielectric material adhered to the inner surface thereof, and a cylindrical high-voltage electrode concentrically installed on the ground electrode with a discharge space therebetween, and between these electrodes. A double-tube ozonizer for applying an AC voltage to ozone a raw material gas, wherein the high-voltage electrode has a metal oxide film formed as a natural oxide film on a surface from which contaminants are removed by polishing. Double tube type ozonizer. 2. The double-tube ozonizer according to claim 1, wherein the metal oxide film is a natural oxide film formed on the surface of the electrolytically polished high-voltage electrode. 3. The double-tube ozonizer according to claim 1, wherein the metal oxide film is a natural oxide film formed on the surface of the mechanically polished high-voltage electrode.