GB2276521A

GB2276521A - A system for manufacture of ozone from dry oxygen

Info

Publication number: GB2276521A
Application number: GB9404592A
Authority: GB
Inventors: Boris Malkin; Gena Perlov; Shmuel Yannai
Original assignee: Dimotech Ltd
Current assignee: Dimotech Ltd
Priority date: 1993-03-25
Filing date: 1994-03-09
Publication date: 1994-09-28
Anticipated expiration: 2014-03-09
Also published as: ZA942072B; GB9404592D0; CA2119053A1; DE4408196A1; FR2703039A1; GB2276521B; IL105166A0; FR2703039B1

Description

2276521 1 A SYSTEM FOR AN EFFICIENT MANUFACTURE W OZONE The present

invention relates to the manufacture of ozone and uses thereof. More particularly, the invention relates to a new compact system for the manufacture of ozone and new uses thereof.

BACKGROUND OF THE INVENTION

Ozone is a well-known chemical agent used in industrial oxidation, water and air treatment and manych!mical syntheses. As is known, ozone is an unstable gas which is produced by the dissociation-association of oxygen in an electric field derived from a high voltage, on gaseous oxygen or dry air, obtainining a dilute mixture of ozone, and the original gas. Due to its instability, ozore must be produCled at-site near its application for a particular purpose. As a consequence, it is most desirable to provi is de a compact generator for ozone production. The general approach for its manufacture is based on passing a cur- -L-d to rent of air or oxygen between two electrodes subject an alternating current with a high potential difference. The voltage applied to the electrodes depends on tti,-% type and thickness of the dielectric and width of tae gap between electrodes, which is usually in the range ef 4000 to 20,000 volts, depending on the gap. Due to its impertance, the literature is quite abundant with various suggestions and patents claiming some impro- s for producing ozone. P,)st of these patents are vement claiming various types of electrodes for producing the required electric field. Thus, according to the German Patent Number 3,424,889, a special electrode is described being made from a ffetal layer covered by a ceramic layer coated with an additional thin glassy layer with a smooth surface.

According to the Russian Patent Number 1,567,514, the ozonizer described comprises two electrodes, constructed in the form of 2 coaxially arranged metal tubes coated with glass or enamel. The annular space between the intermediate and outer tube and the inner tube are filled with water.

In the Russian Patent Number 1,414,771, an apparatus for producing ozone is claimed. The apparatus comprises a is housing, a generator for ozone with flow sensors and summator, a multiphase current source, an anode and cathode current assemblies and an impulse-phase control unit. The summator outlet is connected to the inlet of the impulsephase control unit.

One of the problems encountered in the production of ozone is related to the losses involved in the electrical discharge, where a large proportion of energy is converted into heat, which gives rise to a high increase in temperature. As a result, an efficient cooling system is 1 v required, due to the fact that the yield of ozone production is reduced when the gas temperature is increased.

The main disadvantages o-AF the known ozone generators are their bulky construction. and the relatively large amount of energy required per quantity unit of ozone produced.

It is an object of the present invention to provide a system for producing ozone, which requires relatively low energy per quantity unit of ozone produced. It is yet another object of the present invention to provide a cimpact system for ozone production, which facilitates its portabilty and uses for various purposes.

2 BRIEF DESCRIPTION OF THE INVENTION.

The invention relates to a system for producing ozone from dry oxygen or air, using a generator which comprises 16 at least two electrodes made of a light material, posses- sing a high electrode-surface area to mass ratio,enclosed in a chamber which is cooled by a gas comprising oxygen at ambient temperature, possessing a particular configuration wherein the cooling medium is conveyed through said at least two electrodes, including compartments which provide mechanical support and electric insulation. Among the significant advantages of the system according to the present invention that should be mentioned are the small size of the generator and the relatively small amount of energy required per unit of ozone produced.

is BRIEF DESCRIPTION OF THE DRAWINGS. Figure 1, is a schematic illustration of the ozone generator according to the present invention. Figure 2, illustrates a whole unit cell. Figure 3, illustrates a cross section of an ozone generator assembly consisting of unit cells. illustrates a partial assembly of more than one unit. illustrates a partial assembly of sev,.ral units as described in Figure 4. is similar to Figure 5, comprising a tunnel which conveys a cooling liquid. illustrates an embodiment of the system comprising porous components.

,.illustrates an embcdiment wherein a voltage DC multiplier is utilized in the ozone generator. represents a schematic illustration of a system using the present invention for water purification.

DETAILED DESCRIPTION OF THE INVENTION. A particular requirement for ozone production using a system according to the present invention, is the use of a very dry air or oxygen. It was found that a moisture content of above 5 ppm will significantly decrease the ozone output. Dehumidification of the air or oxygen is

Figure 4, Figure 5, Figure 6, Figure 7, Figure 8 Figure 9, A 1 achieved by using a desiccating material. In principle, any desiccant may be used, but preferred desiccants found to be most useful for the present invention, are calcium chloride, magnesium perchlorate, phosphorus pentoxide and silica gel.

The electrodes to be used may be selected from a light material, such as glass or aluminium coated by alumina, ceramic or a plastic layer possessing a high dielectric constant. This has an advantage concerning the production of a small and pcrtable system for the ozone manufacture to be used at-site.This arrangement of the system enables to obtain an electrode-surface area to mass ratio much higher than in the conventional ozone generators. Li this manner, this will assist the feature required in the system according to the present invention that ininirrum air spaces will exist between the electrodes, while maintaining a relatively low plasma discharge voltage. By this arrangement, it is possible to obtain a high capacity generator of a relatively small size, which ozone S easily portable.

In contrast to the known generators, which are bulky, heavy and consume large amounts of energy, the ozone system according to the present invention is characteri zed by its small size and the relatively smaller amount of energy required for producing ozone.Thus,instead of 18 1 is to 20 kW per kg ozone required by the known ozone generators, using the system according to the present invention only about 14 kW per kg ozone are consumed.

A significant advantage of the generator according to the present invention is the use of air or oxygen as a cooling medium, instead of water cooling used by the known generators for the same ozone production capacity. This advantageous feature is a consequence of the high elec+ rode-surface area to mass-ratio used in the generator according to the present invention. Consequently, in the plate-type model a simple circulation of air or oxygen at ambient temperature will be enough to cool the elect2 rodes.

In models consisting of concentric cylinders and other n"on-planar models, the system consists of an assembly of cells including tubes, ducts and rods having a circular, triangular, square or polygonal cross section, in which some cf the tubes convey a cooling liquid, such as water or oil. The inner surfaces of the tubes serve as electrodes, and are made from a thin layer of metal. It is also possible that the cooling liquid itself may serve as an electrode by flowing through two electrodes, being separated and electrically insulated.

The ozone generator according to the present invention may be horizontal or vertical tube-type and plate-type.

1 v 7 The whole system is generally enclosed in a chamber and incorporates cooling means provided by circulation of air or oxygen from which ozone is produced. In case of horizontal or vertical tube-type, there are two concentric electrodes and a dielectric tube.

Generally, the ozone generator used in the present invention is fed by an alternating current from a power source which uses a frequency up to 20kHz and preferably between 50 fierz to 10 kliz.

Due to the abovemertioned advantageous features, the ozone obtained according to the present invention may be used for various purposes atsite. In case of a rnodel intended for water treatment, the ozone formed in the generator is dispersed by passing through a sleeve or filter, thus obtaining small bubbles with a maximum surface area, which are collected into a container where it is to be used. It was found that the highest efficiency of ozone use is achieved when said sleeve is made of sintered glass which provides a very small volume of ozone bubbles which are not more than 5x10-7 mI, compared with the usual size of 1x10-2 ml. In this manner,the total bubble surface area is significantly increased, thus facilitating an efficient and fast treatment with the ozone produced, according to the present invention, which cannot be obtained with the known ozone generators.

A is According to another embodiment, the ozone released from the generator is mixed in a separate compartment provided with a tewperature control device, thus facilitating the supply of any desired amount of ozone.

The oxidizing properties of ozone are indeed well-known; however, due to its relatively high costs of manufacture as well as problems involved in its production at-site, the uses of ozone have been quite limited. According to the present invention, where the ozone manufacture costs are significantly reduced and the small, light and inex- pensive systems are provided, many uses are envisaged. Thus, for instance, ozone can be used for sterilization and deodorization of water, for eliminating objectior-able tastes and odours, for eliminating harmful compounds from industrial wastes and controlling bacteria in cold-storage rooms. Figure 9, is a schematic illustration of the system used for water purification. According to another mode of use, the container in which the ozone is dispersed can be fitted with shelves on which solid materials to be treated by ozone, such as agricultural products, food products, packaging materials or equipment that have to be sterilized, c&n be loaded. At the outlet of the container, the residual ozone is spontaneously converted back into oxygen. In cases where even traces of ozone are undesirable, it is possible to f c c 9 - provide at said outlet a trap containing a soluticn of a reducing agent or active carbon, which will readily eliminate said residuee.

DETAILED DESCRIPTION OF THE FIGURES FIGURE 1, is a schematic illustration of the ozone generator according to the present invention. As can be noticed, the generator comprises the following constituuents: 1: the compressor which provides air or oxygen;

2: the filter with a desiccant producing dried air or oxygen; the ozone generator; electrodes in the generator (also enlarged under 11 he inverter (6); the voltage entrance of 11. exit of the air and ozone mixture which enters into the sleeve (8) located in the reservoir (9); 10: the filter for ozone residues at the exit from the reservoir, generally being sintered glass (scaled down in the Figure); 11: the electrode; metal coating; glass, ceramic material or plastic, possessing a high dielectric constant.

3: 4: 5:

is 7:

j - Figure 2, depicts a unit cell consisting of an insulating material such as extruded glass or ceramic. The internal surfaces of the tubes (1) are coated with metal (2) and all the tubes comprising the cell are attached to a cen tral supporting rod (3) which provides mechanical strength.

Figure 3, shows a cross-section of an ozone generator assembly (1), comprising unit cells (as illustrated in Figure 3). The binding of some cells of this design toge ther facilitates the construction of a compact setup packed tightly within a pipe, consisting of phase (2) and zero (3) electrodes, air tubes (4) and reinforcement rods (5). The advantage of this cylindrical ozone generator is that it possesses a relatively large electrode surface is area with an advantageous heat exchange and efficient cooling of all cells, a problem which is well-known in the operation of existing large ozone generators.

Figure 4, illustrates a whole unit cell uf a cylindrical ozone generator, featuring phase (2) and zero (3) elec trodes with a triangular. cross-section, square air ducts (4) and hexagonal supporting rods (5).

Figure 5, shows a partial assembly of several units as described in Figure 4, the whole assembly being packed in a metal pipe. The advantage of this assembly is the small size of the ozone generator obtained.

a n - 1 1 - Figure 6, is similar to Figure 5, except that Itc:n (5) signifies a tunnel conveying a cooling liquid.

Figure 7, illustrates an embcdiment of the system comprising porous components. The advantage of this generator is that due to the porosity of the insulating material, the electrodes may be very thin. Also, the cooling will be more efficient as air passage is effected by being conveyed through multiple pores.

Figure 8, illustrates a preferred embcdiment wherein a voltage DC multiplier is utilized in the ozone generator.

By using a mechanical motion or a polarity switching of said electrodes, an electric AC field will be produced.

The advantage of this generator is that a voltage DC multiplier will replace the ordinary high voltage -trans- is former. Accordingly, the ozone will be manufactured within the gap between the two cylinders which are in motion, causing the AC field. High voltage is attained w.,thin the unit, thus greatly increasing the safety of the ozone generator and simplifying the design of the system.

Figure 9, is a schematic illustration of a system using the present invention for water purification wherein:

1: a container for receiving the ozone, made of plastic, glass or any other suitable material; 2: the cover of the reservoir; 3:

5: 6: 7:

the shelves are located in the reservoir, on which the material to be treated by ozone is loaded; trap at the outlet of the container, for removal of dny traces of ozone; the ozone generator; the electrical generator; the filter with the desiccant through which the air or oxygen enters into the generator; 8: a compressor which delivers the air or oxygen into the generator; 9: the electric contacts-, 10: a sleeve made of sintered glass which supplies the very small bubbles of ozone; 11: inlet for ozone, and 12: outlet for ozone residues.

While the invention has been described in respect to certain preferred embcdiments, it should be understood that the description is provided primarily for F-,rpos_s of illustration, the invention in its broader aspects

Claims

being covered by tne foliowing Claims.

j T C L A I M S: - 1. A system for producing ozone from dry oxygen or air, using a generator which comprises al, least two electrodes made of a light gaterial, possessing a high electrode surface area to mass ratio, enclosed in a chamber which is cooled by a gas comprising oxygen at ambient temperature, possessing a particular configuration wherein the cooling medium is conveyed through said at least two electrodes, including compartments which provide rfiech.ariical support and electric insulation
2. The system according to Claim 1, wherein the cooling effect used in the generator is provided by circulation of air or oxygen at ambient temperature.
3. The system according to Claims 1 or 2, wherein the drying of oxygen or air fed to the generator is achieved by a desiccating material.
4. The system according to Claim 3, wherein said desiccating nia-terial is selected from calcium chl,.-)y-ide., magnesium perchlorate, phesphorus pentoxide and silicuz gel.

14 -
5. The system accordin to Claim 1, wherein said electrodes are made from a light material selected from glass, ceramic or plastic coated with a thin aluminum layer possessing a high dielectric constant.
6. The system according to Claim 5, wherein the electrodes in said generator are concentric with a dielectric tube.
7. The system according to Claims I to 5, wherein the ozone generator has a plate-type shape.
8. The system according to Claims 1 to 7, wherein tho ozone generator is fed by an alternating current from a povier source which uses a frequency of up to 20 kHz.
9. The system according to Claim 8, wherein said frequency is in the range of 50 herz to 10 kHz.
10. The system according to Claims I to 9, wherein at least one pair of electrodes are made of a perforated material, featuring at least one hole in each electrode, being separated by an insulating porous material.
11. The system according to Claims i to 9, wherein at least one pair of electrodes are made of a porous material, being separated by an insulating porous material.

1
12. The system according to Claim 6, wherein at least two electrodes are contained in the internal electricallyinsulated cylinder, and at least one pair of electrodes is packed within the external cylinder.
13. The system according to Claims 1 to 7, wherein the ozone released from said system is mixed in a mixing compartment.
14. The system according to Claim 13, wherein said mixing compartment is provided with a temperature controller to permit condensation of vapour.
15. The use of a system for ozone generator according to Claims 1 to 12, for the sterilization of solid materials located on shelves in the ozone container.
16. A system fcr producing ozone from dry oxygen or air, substantially as described in the specification and in any one of Claims 1 to 14.

A A