WO1991011395A1

WO1991011395A1 - Oxidizing apparatus

Info

Publication number: WO1991011395A1
Application number: PCT/AU1991/000028
Authority: WO
Inventors: David Bruce Ogle
Original assignee: Sports Marine International Pty. Ltd.
Priority date: 1990-01-24
Filing date: 1991-01-24
Publication date: 1991-08-08

Abstract

Oxidizing apparatus suitable for continuous production of ozone from air or an oxygen containing gas pumped into a body of water for purifying the water. The oxidizing apparatus (10) includes a generating means (17) for generating a high-voltage, a confining means (13) for confining a flow of gas and a discharge electrode (14) associated with the confining means (13) and connected to the generating means (17) to develop an ozone producing electric discharge within the confining means (13). The electric discharge is either a corona discharge, a spark discharge or a combination thereof. The discharge electrode (14) is rod like and the discharge end of the rod-like electrode is formed to provide a discharge apex (15), with the apex being either rounded or pointed to form the apex. A plurality of such rod-like electrodes (31) may be employed as the discharge electrode (30).

Description

"OXIDIZING APPARATUS" This invention relates to oxidizing apparatus. This invention has particular but not exclusive application to the sterilising of water, and for illustrative purposes reference will be made to such application. However, it is to be understood that this invention could be used in other applications, such as bleaching, disinfecting and aqueous oxidation and ozonolysis.

The use of chlorine related chemicals as oxidizing biocides is well known. Chlorine related oxidizing biocides such as chlorine, hypochlorites, chloramine and organochlorines effect a rapid kill on bacteria if free chlorine comes into contact with the organisms for a sufficient time and at a strong enough dosage level. For example, such chlorine related chemicals are routinely added to potable water for sanitizing the supply. While chlorination is usually quite effective for such purposes, it produces an unpleasant odour when used in effective dosages, is highly corrosive and chlorine gas itself is poisonous. Such oxidizing biocides also react with contaminants such as ammonia, hydrogen sulfide, lignin and wood sugars, as well as other organic compounds, thus requiring an increase in dosage to accommodate such contaminants. Although chlorination compounds are not persistent and decay within a relatively short period of time, they do not penetrate slime masses, and lose their effectiveness as alkalinity increases. The chemicals are expensive, and in addition, their storage and transport in a concentrated state constitute a significant danger to life as well as the environment.

The use of ozone as an oxidizing agent for sterilization is known, and apparatus for generating same for such purposes is also known. There are two popular techniques used to generate ozone, a highly reactive allotrope of oxygen; the first being ultraviolet irradiation through a quartz window into an air stream, and the second by use of electrical field or discharge apparatus within or about an air stream. The former operates at very low efficiency, and the surface of the quartz window must be cleaned frequently to maintain effectiveness. The second is very energy intensive, and can only achieve efficiency on a large scale. Examples of such technology are disclosed in the following patents. United States Patent 4,619,763 discloses a water purifier including an ozonator wherein water is exposed to an ozone enriched atmosphere either as a direct in-line delivery to a water supply or with a portion of the water being recirculated and exposed to the ozone enriched atmosphere. The patent teaches the generation of ozone in chilled air which is preferably dry and below 15.6°C using a 3,000 to 10,000 volt AC power source with a frequency of 500 to 10,000 Hz. The electric discharge referred to in the patent, is a corona discharge produced at or near the surface of a tubular shaped electrode coaxially disposed within another tubular shaped electrode. The former electrode has a coolant passing through the axial aperture thereof, and the gas to be ozonated passes through the annulus between the former and the latter tubular electrodes. A venturi is used to introduce the ozone enriched gas into the water. This disclosure has the disadvantage that large and expensive cooling capability must be incorporated into the system to maintain efficiency.

United States Patent 4,834,948 discloses a water purifier with an ozonator wherein one of the electrodes is preferably a helix and the cooling water passing through a quartz tube is used as another electrode. In this disclosure, the high energy output requires extensive cooling.

Soviet Union Patent 969,680 discloses a water purifier with an ozonator wherein a corona discharge is generated using a high voltage impulse generator with a capacitor connected to an electrode system through a commutator. Although claiming low energy consumption, the system does not provide for a continuous corona discharge.

The present invention aims to alleviate the above disadvantages and to provide oxidizing apparatus which will be reliable and efficient in use. Other objects and advantages of this invention will hereinafter become apparent.

With the foregoing and other objects in view, this invention in one aspect resides broadly in oxidizing apparatus suitable for producing ozone from air or an oxygen containing gas pumped into a body of water for purifying the water, said oxidizing apparatus including:- generating means for generating a high-voltage; confining means for confining a flow of gas, and a discharge electrode associated with said confining means and connected to said generating means whereby operation of said generating means develops an ozone producing electric discharge within said confining means.

In a preferred embodiment, the discharge electrode is rod like and the -discharge end of the rod-like electrode is formed to provide a discharge apex. In one form the discharge end of the rod is rounded to form the apex, and in another form the discharge end of said rod is pointed to form the apex. Of course, a plurality of such rod-like electrodes may be employed as the discharge electrode. The e^'lectrode may be disposed internally or externally of the confining means.

In one preferred embodiment, the generating means generates a high voltage sufficient to produce a spark discharge, and preferably, such spark discharges are of very short duration. In another preferred embodiment, the generating means generates a high voltage sufficient to produce a corona discharge. Preferably, the generating means generates a high voltage from a DC low voltage source.

Preferably, the oxidizing apparatus includes a field shaping electrode supported adjacent or within the confining means for aligning the discharge with the gas flow therethrough, with the field shaping electrode preferably being a flat plate with a rounded edge.

Preferably, the confining means is a dielectric tubular member and the field shaping electrode is an elongate electrode extending adjacent the wall of the tubular member. The field

^• shaping electrode may be disposed internally or externally of the confining means. The discharge electrode may be an anode, but preferably the discharge electrode is a cathode.

Suitably, the discharge electrode may . extend into the confining means such as a tube through which air may be pumped, and the field-shaping electrode may be arranged adjacent the wall of the tube remote from the discharge electrode. The electric discharge may be one of, but not limited to a glow, arc, spark or corona discharge. However, a corona or short duration spark discharge are preferred. When using a corona discharge, there is minimal power consumption. The low current flow also results in low electrode erosion rates, permitting the discharge electrode to be constructed from low-cost metals such as stainless steel, aluminium or copper. The high-voltage source may be of alternating current, but a direct current source is preferred such as a mains-powered transformer/rectifier type, and may include a high-frequency oscillator to minimise the size of the transformer or inductor. Alternatively, the power source may be a storage battery such as a six, twelve or twenty-four volt power supply commonly found in small marine or automotive applications. In another aspect, the preferred power source is of limited capacity and wherein electric potentials in which very short duration spark discharge are produced thereby minimizing ozone break-down attributable to the lower gas temperatures surrounding the spark than in prior art spark discharge apparatus.

In another aspect, this invention resides in a method of sterilising water, said method including:- providing an air tube having a discharge electrode extending into the air passage therethrough; providing a field-shaping electrode disposed adjacent the wall of said air tube opposite said discharge electrode; connecting a source of high-voltage electricity between said discharge and said field-shaping electrodes such that an electric discharge forms about said discharge electrode; passing a stream of gas containing oxygen through said air tube whereby the oxygen is converted to ozone, and passing said gas stream through a body of water downstream from said discharge electrode whereby the ozone contained in said stream acts as an oxidizing agent for impurities contained in the water.

In another aspect, this invention resides in an oxidizing apparatus including:- a rod-like discharge electrode formed to provide . a discharge apex, and a generating means for generating a high-voltage from a DC low-voltage source operatively connected to the rod-like discharge electrode.

In order that this invention may be more easily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate preferred embodiments of the invention, wherein:-

FIG. 1 is a schematic diagram of an oxidizing apparatus according to the invention;

FIG. 2 is a schematic diagram of a further embodiment of an oxidizing apparatus;

FIG. 3 is a schematic diagram of a rod-like discharge

-electrode according to an embodiment of the invention, and

FIG. 4 is a schematic diagram of a rod-like discharge electrode according to another embodiment of the invention. The oxidizing apparatus 10 shown in FIG. 1 includes an air pump 11, the discharge of which is connected to a water tank 12 by an oxidizing pipe 13. A discharge electrode or anode 14 in the form of a rod with a rounded tip 15 extends into the top of the pipe 13, and a field-shaping electrode or cathode 16 is arranged outside the pipe 13 directly below the anode 14. The cathode 16 is in the form of a flat plate with a rounded edge.

A high-voltage DC electricity source 17 is connected between the cathode 16 and the anode 14, positive to the latter.

The voltage of the source 17 is set at a level which is insufficient to cause break down of the dielectric property of the air leading to a spark discharge path between the anode 14 and the cathode 16, but sufficient to induce a corona discharge about the tip 15. There are a number of chemical pathways which may theoretically produce ozone according to this invention. While not being bound by theory, the corona discharge produces ultra-violet radiation which may emanate from excited nitrogen molecules, and this radiation acts on the oxygen molecules O2 to produce ozone molecules O3. Ozone O3 may be generated by electrons colliding with oxygen molecules O2 splitting to form oxygen atoms 0 which partly associate with oxygen molecules O2. Ozone may also be generated by a number of other pathways, such as, but not limited to, through the oxides of nitrogen N0_X, hydrogen dioxide HO2, and intermediate, excited or activated forms of oligomeric oxygen as well as oxides of the components in the gas stream wherein the ozone is generated. The ozone-rich air bubbles through the water in the tank 12, and its highly reactive nature ensures that a high proportion of bacteria and the like present in the water are destroyed.

The voltage source 17 may be of any convenient form, but is suitably a mains-powered transformer/rectifier type, and may include a high-frequency oscillator to minimise the size of the transformer or inductor.

The oxidizing apparatus 30 of FIG. 2 is similar to that shown in FIG. 1, except that a plurality of anodes 31 are connected in parallel to the positive terminal of a voltage source 32. A common cathode 33 extends beneath the anodes 31. This arrangement increases the ozone production and thus the concentration, giving a greater oxidizing effect.

In addition, the voltage may be reversed so that the anode 31 is used as the cathode where the negative charge thereon may assist in the production of the peroxyanion 0~.

Referring to FIGS. 3 and 4, the discharge electrode 40 is rod-like in shape and has a discharge apex on the distal end thereof. The discharge electrode is placed in the gas stream 49. The discharge apex may be rounded as shown at numeral 41 in FIG. 3 or pointed as shown at numeral 42 in FIG. 4. In each case, the electric discharge is shaped by the shaping electrode 45 having rounded ends 46.

It will of course be realised that the above has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as is herein defined in the appended claims.

Claims

— CLAIMS —

1. Oxidizing apparatus suitable for producing ozone from air or an oxygen containing gas pumped through confining means into a body of water for purifying the water, said oxidizing apparatus including:- generating means for generating a high-voltage; confining means for confining a flow of gas, and a discharge electrode associated with said confining means and connected to said generating means whereby operation of said generating means develops an ozone producing electric discharge within said confining means.

2. Oxidizing apparatus as claimed in claim 1, wherein said discharge electrode is rod like and wherein the discharge end of said rod-like electrode is formed to provide a discharge apex.

3. Oxidizing apparatus as claimed in claim 2, wherein the discharge end of said rod is rounded to form said apex.

4. Oxidizing apparatus as claimed in claim 2, wherein the discharge end of said rod is pointed to form said apex.

5. Oxidizing apparatus as claimed in any one of the preceding claims, wherein said generating means generates a high voltage sufficient to produce a spark discharge.

6. Oxidizing apparatus as claimed in any one of the preceding claims, wherein said generating means produces very short duration spark discharges.

7. Oxidizing apparatus as claimed in any one of claims 1 to 4, wherein said generating means generates a high voltage sufficient to produce a corona discharge.

8. Oxidizing apparatus as claimed in any one of the preceding claims, wherein said generating means generates a high voltage from a DC low voltage source.

9. Oxidizing apparatus as claimed in claim 8 when appended to claim 6, wherein said DC low voltage source is a storage battery.

10. Oxidizing apparatus as claimed in any one of the preceding claims and including a field shaping electrode supported adjacent or within said confining means for aligning said discharge with the gas flow through said confining means.

11. Oxidising apparatus as claimed in claim 3, wherein said field shaping electrode is a flat plate with a rounded edge.

12. Oxidizing apparatus as claimed in claim 10 or claim 11, wherein said confining means is a dielectric tubular member and said field shaping electrode is an elongate electrode extending adjacent the wall of said tubular member.

13. Oxidizing apparatus as claimed in any one of the preceding claims, wherein said discharge electrode is disposed within said confining means.

14. Oxidizing apparatus as claimed in any one of the preceding claims wherein said discharge electrode is a cathode.

15. A method of sterilising water, said method including:- providing an air tube having a discharge electrode extending into the air passage therethrough; providing a field-shaping electrode disposed adjacent the wall of said air tube opposite said discharge electrode; connecting a source of high-voltage electricity between said discharge and said field-shaping electrodes such that an electric discharge forms about said discharge electrode; passing a stream of gas containing at least some oxygen through said air tube whereby a portion of the oxygen passing therethrough is converted to ozone, and passing said gas stream through a body of water downstream from said discharge electrode whereby the ozone contained in said stream may act as an oxidizing agent for impurities contained in the water.

16. Oxidizing apparatus substantially as herein described with reference to the accompanying drawings.

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