GB2144610A - Ozone generator - Google Patents

Abstract

The ozone generator 27 has outer and inner tubular electrodes 32, 29 with a tubular insulator 38 between them. A passageway for air to be ozonised is defined between at least one of the electrodes and the insulator, and the electrode surface delimiting the passageway is provided with grooving 43. <IMAGE>

Description

SPECIFICATION Ozone generator Ozone is produced by the action of a glow discharge on molecules of oxygen. Basically, an ozone generator comprises two electrodes with an insulator of dielectric material between to prevent direct arcing between the electrodes. An air passage is defined on one or both sides ofthe insulator, and a sufficient potential difference is applied across the electrodes to obtain electron flow in the (or each) passageway. There are two main forms of electrode assembly, employing either flat components or tubular components.

The present invention provides an ozone generator comprising an innertubularelectrode, an outer tubular electrode, and a tubular insulator of dielectric material disposed between the electrodes and forming with at least one of them an elongate passageway in which a glowdischargeisto be produced bythe application of a high voltage across the electrodes, the passageway communicating at one end with an air inlet and atthe other end with an ozonised air outlet; the electrode surface delimiting the passageway is provided with grooving extending over at least a major part ofthe area facing the other electrode.

The grooving may run substantially circumferentially. In particular, it may comprise annular grooves; however, it is more easy to cut a helical groove in the manner of a screwthread. Alternatively, or additionally, the grooving may comprise longitudinal grooves.

The provision of grooving in the electrode surface produces sharp edges atwhich the electrical field is intensified, thus facilitating the production of a glow discharge which is highly efficient in converting oxygen into ozone. It appears that, by grooving the electrode surface, it is possible to increase the rate of ozone generation by a factorofabout 2 without difficulty.

The main use for ozone is in the treatment of water, since it is a highly efficient agentforthe inactivation of viruses and for the decomposition of certain pollutants such as phenols.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic elevation of apparatus for producing ozone, which is mounted in a cabinet shown in vertical section; Figure 2 is a transverse section through the ozone generatorofthe apparatus; Figure 3 is a part-sectioned elevation ofthe ozone generator; Figure 4 is an enlarged detail of Figure 3; Figure 5 is an elevation ofthe ozone generator, provided with fins, on a reduced scale; Figure 6 is an end view corresponding to Figure 5; Figures 7 and 8 are views corresponding to Figure 4 of two different embodiments of ozone generators; and Figures 9 and 10 are views corresponding to the left-hand side of Figure 2, oftwo further embodiments of ozone generator.

Referring first to Figure 1, a piston compressor 1 draws in airthrough a pipe 2from an airfilter3 mounted in an aperture in the cabinet 4 containing the ozone generating apparatus. Warm compressed air at a pressure of about 4.5 bars leaves the compressor 1 through a pipe 6 and enters a heat exchanger in the form of a honeycomb radiator7 mounted adjacent an aperture 8 in the cabinet 4. If necessary, ambient air can be driven through the radiator 7 by a fan (not shown).

The compressed airfollows a sinuous path through the radiator 7 and is cooled to approximately ambient temperature with the resultthat water condenses out of the compressed air. The water is separated from the compressed air in a trap 9 from which the water is periodically automatically vented. The compressed air then passes through a pipe 11 to an electrically controlled slide valve 12.

In the situation shown in Figure 1, the valve 12 connects the pipe 11 to the lower end of a desiccator 13, which is one of two molecular sieve desiccators 13, 14 which work in alternation. In Figure 1,the desiccatorsareshown side-by-sideforthe sake of clarity, but in practice they will be mounted one in front of the other in orderto save space. The compressed air passes through the desiccator 13, in which the molecular sieve takes up its water content, and then passes to a pressure operated slide valve 16, which, in the situation illustrated in Figure 1, connects the upper end of the desiccator 13 to a pipe 17 leading to the compressed air inlet of a needle valve 18 from which the compressed air expands into a pipe 19.The airin the pipe 19 is approximately at ambient pressure, is at less than ambienttemperature (owing to the expansion), and is very dry; itthus has the optimum properties for ozone generation.

The surplus compressed airfrom the desiccator 13 which is under pressure is returned through a needle valve 21 to the upper end of the other desiccator 14.

The dry air passes through the desiccator 14, sweeping out any moisture which has been stored in that desiccator, and leaves the lower end of the desiccator 14,which, in the situation illustrated in Figure 1, is connected to an air discharge outlet 22. This air may be discharged to the atmosphere, as shown, or it may be discharged into the cabinet4 at one or more points so asto provide a flow of air in the cabinetforthe purpose of cooling. Acontrol unit23, including a timer, periodically changes overthe operation of the desiccators 13 and 14 by operating the slide valve 12 sothatthe incoming compressed airflows up through the desiccator 14, operates the slide valve 16, and enters the pipe 17, while the surplus air expands through the needle valve 21 and flows down through the desiccator 13, clearing it ofthe moisture previously collected.

The flow rate of the air in the pipe 19 is indicated by a gauge 24visiblethrough a window 26 in the front of the cabinet4. The air enters the upper end of an ozone generator 27 (described below) and the ozonised air leaves the ozone generator through a pipe 28. A high The drawing(s) originally filed was (were) informal and the print here reproduced is taken from a later filed formal copy.

voltage at a high frequency (e.g. 5 to 10 for more at 5 to 10 kHz) is produced byan electronic unit 29 connected to the ozone generator 27 by a high tension lead 31, the exterior of the ozone generator being earthed. The unit 29 is powered by the mains and comprises a transformer, a rectifier, and an inverter.

Alternatively, the inverter can be powered by a battery, e.g. a vehicle battery, and the apparatus is thus readily transportable. Furthermore, the appar atus is very compact: the cabinet 4 is less than 1 metre in height and width, and has a depth of about 200 mm.

The ozone generator27 (see Figures 2to 4) has an outertubularelectrode 32 with an air inlet nipple 33 (to which the pipe 19 is attached) and an ozonised air outlet nipple 34 (to which the pipe 28 is attached). The electrode 32 is of stainless steel and has end caps 36, 37 which locate a coaxial tubular insulator 38 of glass or other dielectric material. Between the nipples 33 and 34, the innersurfaceofthe insulator38is provided with an innertubular electrode 39 formed by electroplating copper onto an electrolessly deposited film of silver. The electrode 39 is covered by an insulating layer of resin 41, except where it is connected to the high tension lead 31, which enters through the end cap 36.

When the high voltage at high frequency is applied to the inner electrode 39, the outer electrode 32 being earthed, a glow discharge is produced in the passageway 42 defined between the electrode 32 and the insulator 38. The inner surface of the electrode 32 is provided with grooving in the form of a helical groove 43 resembling a screwthread. It has been found that the presence ofthis grooving has a very advantageous effect on the efficiency of the ozonisation of the air passing along the passageway 42. The provision of the groove 43 results in two sharp edges being formed at the internal surface ofthe electrode 32, and the electric field is intensified at these edges.Furthermore, the machining of the groove 43 in the electrode 32 causes these sharp edges to be irregular and to contain many sharp points which produce intense local electric fields facilitating the production of an effective glow discharge along the whole of the path ofthe air.

The stainless steel electrode 32 acts as a heat sink forthe heat generated in ozonising the air in the passageway 42. Given thefactthatthe air entering the generatorthrough the pipe 19 is coolerthan ambient temperature, the electrode 32 will normally conduct away sufficient heat to prevent the temperature in the passageway 42 from becoming excessive, at ozone production rates of 1 to 5 g/h. If required, however, an additional heatsinkcan be provided intheform of an extruded metal member44with longitudinal fins 46, this member being in contact with the electrode 32 along most of its length. An airflow overthefins can be provided by convection, by a fan (not shown), or by the air discharged from the pipe 22.

Figures7 and 8 showdifferentforms ofthe grooving of the internal surface of the electrode 32. These Figures show longitudinal grooves 47 and annular circumferential grooves 48. In Figure 8the two types of groove are used together, resulting in sharp corners as well as sharp edges. Although the grooves in Figures 4,7, and 8 are shown as V-shaped in section, they could be of any other convenient shape.

Figures 9 and 10 showtwo alternative arrange ments ofthe insulator 38 in relation to the electrodes 32 and 39. In Figure 9, the insulator 38 is directly adjacentthe outer electrode 32 and is spaced from the inner electrode 39, which is supported by the end caps 36,37. Here the external surface of the electrode 39 is provided with grooving 49 having anyofthethree forms described above with reference to Figures 4,7, and 8. The air is passed through the passageway 51 defined between the insulator38 and the conductor 39. In Figure 10 the insulator 38 is spaced from both electrodes 32 and 39 and with them defines two passageways 52 and 53 along which the air is passed.

In this case both the inner surface of the outer electrode 32 and the outer surface of the inner electrode 39 are provided with grooving.

Claims (5)

1. An ozone generator comprising an innertubular electrode, an outertubular electrode, and a tubular insulator of dielectric material disposed between the electrodes and forming with at least one of them an elongate passageway in which a glow discharge is to be produced bythe application of a high voltage across the electrodes, the passageway communicating at one end with an air inlet and atthe other end with an ozonised air outlet, the electrode surface delimiting the passageway being provided with grooving extending over at least a major part of the area facing the other electrode.

2. An ozone generator as claimed in claim 1,in which the grooving comprises a helical groove or circumferential annular grooves.

3. An ozone generator as claimed in claim 1 or2, in which the grooving comprises longitudinal grooves.

4. An ozone generator as claimed in any of claims 1 to 3, in which the electrodes define two said passageways, respectively, with the insulator, the inner surface of the outer electrode and the outer surface of the inner electrode both being provided with grooving.

5. An ozone generator substantially as described with reference to, and as shown in, the accompanying drawings.