CA2072828A1 - Ozone generator - Google Patents
Ozone generatorInfo
- Publication number
- CA2072828A1 CA2072828A1 CA 2072828 CA2072828A CA2072828A1 CA 2072828 A1 CA2072828 A1 CA 2072828A1 CA 2072828 CA2072828 CA 2072828 CA 2072828 A CA2072828 A CA 2072828A CA 2072828 A1 CA2072828 A1 CA 2072828A1
- Authority
- CA
- Canada
- Prior art keywords
- plate
- dielectric material
- electrode structure
- electrode plates
- ozone
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
- C01B13/10—Preparation of ozone
- C01B13/11—Preparation of ozone by electric discharge
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2201/00—Preparation of ozone by electrical discharge
- C01B2201/10—Dischargers used for production of ozone
- C01B2201/12—Plate-type dischargers
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2201/00—Preparation of ozone by electrical discharge
- C01B2201/20—Electrodes used for obtaining electrical discharge
- C01B2201/22—Constructional details of the electrodes
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2201/00—Preparation of ozone by electrical discharge
- C01B2201/30—Dielectrics used in the electrical dischargers
- C01B2201/32—Constructional details of the dielectrics
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2201/00—Preparation of ozone by electrical discharge
- C01B2201/30—Dielectrics used in the electrical dischargers
- C01B2201/34—Composition of the dielectrics
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Oxygen, Ozone, And Oxides In General (AREA)
Abstract
ABSTRACT
Disclosed is an improved electrode structure for ozone generation. The structure includes a dielectric, such as aluminum oxide in the form of a thin alumina ceramic plate, mounted between and separated from two parallel and closely spaced planar metal electrodes of a chemically stable metal such as titanium. The structure is designed so that the dielectric plate can be readily inserted into or removed from an insulating frame holding the metal plates. The insulating frame material is suitable for high voltage applications and is designed so that the metal plates are held parallel to one another at a predetermined small spacing, and also contains suitable guides for the dielectric plate so that it can be easily inserted between the metal plates and held in position. The dielectric plate is larger in outer dimensions than the opposing metal plates such that this distance prevents the possibility of electric arcing between the metal plates, and the insulating frame prevents arcing between the metal plates and any grounded support structure. As the dielectric plate can be easily inserted into or removed from the frame with a simple sliding action, the design enables a handle and a cleaning pad to be attached to the dielectric plate such that dust and particulate contamination can be readily removed from the gaps between the metal plates and the dielectric plate. This permits easy cleaning of the ozone generator without dismantling the structure.
Disclosed is an improved electrode structure for ozone generation. The structure includes a dielectric, such as aluminum oxide in the form of a thin alumina ceramic plate, mounted between and separated from two parallel and closely spaced planar metal electrodes of a chemically stable metal such as titanium. The structure is designed so that the dielectric plate can be readily inserted into or removed from an insulating frame holding the metal plates. The insulating frame material is suitable for high voltage applications and is designed so that the metal plates are held parallel to one another at a predetermined small spacing, and also contains suitable guides for the dielectric plate so that it can be easily inserted between the metal plates and held in position. The dielectric plate is larger in outer dimensions than the opposing metal plates such that this distance prevents the possibility of electric arcing between the metal plates, and the insulating frame prevents arcing between the metal plates and any grounded support structure. As the dielectric plate can be easily inserted into or removed from the frame with a simple sliding action, the design enables a handle and a cleaning pad to be attached to the dielectric plate such that dust and particulate contamination can be readily removed from the gaps between the metal plates and the dielectric plate. This permits easy cleaning of the ozone generator without dismantling the structure.
Description
ELECTRODE STRUCTU~ FOR OZO~E GENERATOR
BACgGROUND OF THE I~VENTIO~
1. Field of the In~ention This invention rela~es to an improved parallel plate electrode struckure for use in ozone generating apparatus.
It is known that ozone is very efficient at eliminating odours and killing certain bacteria and fungi, thus inhibiting mould growth in certain circumstances. Ozone is particularly effective in oxidizing odoriferous gases containing sulphur groups, such as hydrogen sulphlde and methyl mercaptan. It is also effective in oxidiziny gases such as ammonia, skatole and indole and as a result is effectlve in combatting toilet odours.
Ozone is also known to oxidize aldehydes and other chemicals contributing to the odour of cigarette smoke. Hence there is a growing use of low levels of ozone to remove odours in a wide range of applications such as odours in garbage roomæ and toile s and the removal of smoke odours in residential and hotel accommodation. Relatively low levels of ozone production are required for these types of applications, and this is ~he principal area of use for the apparatus according to the present - invention.
II. Prior Art One common me~hod of producing ozone is by means of a sllent electric discharge, hereinafter sometimes referred to as a corona discharye, generated between two parallel metal electrodes separated by an alr gap in whlch a solid dlelectric material is inserted to partly flll the gap. An alternating high voltage is applied to the metal electrodes and a corona discharge is - ':: ~: '': ~ . i ,::
.,: ::; ~: : ; : : . , . . :
', '' , ' ,"';''',' ,': '''""'" ~' :,:
BACgGROUND OF THE I~VENTIO~
1. Field of the In~ention This invention rela~es to an improved parallel plate electrode struckure for use in ozone generating apparatus.
It is known that ozone is very efficient at eliminating odours and killing certain bacteria and fungi, thus inhibiting mould growth in certain circumstances. Ozone is particularly effective in oxidizing odoriferous gases containing sulphur groups, such as hydrogen sulphlde and methyl mercaptan. It is also effective in oxidiziny gases such as ammonia, skatole and indole and as a result is effectlve in combatting toilet odours.
Ozone is also known to oxidize aldehydes and other chemicals contributing to the odour of cigarette smoke. Hence there is a growing use of low levels of ozone to remove odours in a wide range of applications such as odours in garbage roomæ and toile s and the removal of smoke odours in residential and hotel accommodation. Relatively low levels of ozone production are required for these types of applications, and this is ~he principal area of use for the apparatus according to the present - invention.
II. Prior Art One common me~hod of producing ozone is by means of a sllent electric discharge, hereinafter sometimes referred to as a corona discharye, generated between two parallel metal electrodes separated by an alr gap in whlch a solid dlelectric material is inserted to partly flll the gap. An alternating high voltage is applied to the metal electrodes and a corona discharge is - ':: ~: '': ~ . i ,::
.,: ::; ~: : ; : : . , . . :
', '' , ' ,"';''',' ,': '''""'" ~' :,:
2~72~2~
established in the intervening air gap. Ozone is produced ln this corona discharge and direct arcing between the plates is prevented by the presence of the solid dielectric material The basic phys.tcs and chemistry of the production of the ozone by this means is well known and documented in the text "Ozone" by Horvarth, Bilitzky and H~ter, Elsevier, (1985).
The production of ozone by silent corona discharge in an apparatus with parallel plate electrode structures has been used for many years. An early U.S. Pat. No. 991,767 issued on May 11, 1911 to Armstrong described a parallel plate generator wlth sheet glass dielectrics and adjacent and parallel metal electrodes made from either copper gauze or metals such as tin foil. Air was blown between the plates while a high tension A.C. transformer produced a silent electric discharge in the air gap between the metal plates and the dielectric materials. Many other similar parallel plates devices have been described, such as in U.S.
Patent 2,345,789, issued on April 4, 1944 to Daily. Here, metal electrodes of wire screen materials or aluminum plates were bonded to ylass or other dielectrics and ozone produced in the air gap between the alternate dielectric and metal plates of the structure.
The dielectric plates of ozone generators are generally made from glass, mica or dielectric materials such as alumina. A
recent patent, U.S. Paten~ No. 4,892,713 issued on Jan. 9, l99O to Newman, describes a parallel plate ozone generator with a solid plate ca~hode separated from a porcelain dielectric with insulating spacers and a mesh anode directly contacting the opposing side of the dielectric. The configuration is basically .
, ,' ' ' :~ :' '' '" ' :
:
: .. :; .
~072~28 3 73~24-5 that of the standard parallel plate ozone generator, and ozone is extracted from the structure by blowing air through the gaps in the structure in which ozone is formed by the action of an alternating high volkage applied to the metal electrode structures.
Previously described parallel plate ozone generators suffe~ from loss of efficiency ln ozone production as a function of time, particularly when they are used to produce ozone from unprocessed room air. With the passage of moist and contaminated air through the ozone generator several forms of contamination develop on the surface o~ the dielectric material and the opposing surfaces of the metal electrodes. Contamination on the dielectric results from the accumulation of organic contaminants from the air and from reaction products of ozone with impurity gases in the air. This film of contamination is generally hydroscopic and the adsorption of water by the ~ilm causes a conductive layer to develop on the surface of the dielectric. In the presence of this slightly electrically conducting film the efficiency for ozone production from the device drops so that in time the dielectric has to be cleaned or replaced. In addition to the above contamlnation sources, the dielectric becomes contaminated with oxidation products from reactlons with the surface of the metal electrodes. In the case of electrode material such as stainless steel, one of these reaction products i5 hydrated iron oxide which deposit~ as a rust-llke ~ on the surface of the dielectric and degrades the performance of the generator.
In addition to contamination on the surface of the dlelectric, particulate materials build up on the surfaces of " : ~; "
, ~
,; : : , : :, ,, , ~ : ;
2~728~8 the metal electrodes facing the dielectric, mainly by the process of electrostatic precipitation. This particulate contamination reduces the flow rate oE air through the air gaps in the ozone generator and thus reduces the efficiency of ozone production.
SU~IMARY OF THE I~VENTION
The present invention mitigates the above problems by incorporating features into the design of the ozone generator that prevent the ~ormation of conducting oxides on the dielectric.
Further, it allows for in situ cleaning of the active surfaces of the metal electrodes and ease of replacement of the dielectric material.
The ozone generator is designed in such a way that the dielectric plate of the parallel plate structure can be easily removed from the generator by sliding it out from between the fixed metal counter electrodes in su:Ltable guides in an insulating frame. With a cleaning pad attached to the dielectric plate, this action of removing the dielectric plate can also serve to clean particulate matter from the adjacent inner surfaces of the metal counter electrodes. The material of the fixed parallel plate metal counter electrodes is selected so that oxidation products formed by the action of the air, water vapour and ozone have a higher dielectric constant than the material of the dielectric plate. ~s a result, as oxidation products deposit on the dielectric plate, there is no loss of efficiency of the ozone generator due to the electrical conductivi.ty of these products, as is the case for commonly used electrode materials such as stainless steel.
In accordance with a broad aspect of this invention , ~ ,. . : . . ;
:
~0728~8 ~here is provided a parallel plate electrode structure for an ozone generator comprisiny an insulating frame having means for supporting first and second metal electrode plates in parallel spaced apart relation and guide means for slidably receiving a plate of dielec~ric material and releasably holding it in a position between and spaced from said metal electrode plates.
BRI~F DE9CRIPTIO~ OF THE DRA~I~GS
Figure 1 is a perspective view of one embodiment of the electrode structure according to the invention.
Flgure 2 is an end view of the electrode structure of the first embodlment of the invention.
Figure 3 is a perspective of another embodiment of the invention, where the dielectric plate can be removed in a direction at right angles to that of Figure 1.
Figures 4a and 4b are views of one form ol the dielectric plate where a felt like pad of cleaning material is bonded parallel to-one edge of the dielectric plate. In addition, a handle 47 is attached to the other end.
Flgure 5 is a view of an ozone generator within an enclosure containing a fan, high voltage transformer and necessary control equipment for the operation of the generator and from which the diele~tric plate can be removed from the generator from outside the ~eneral enclosure.
DESCRIPTION OF THE PREFERR~D EHBODIME~T
Figures 1 and 2 illustrate a first embodiment of the electrode structurer accordiny to the lnvention, for an ozone yenerator. The structure lncludes a dielectric plate of aluminum oxide in the form of an alumina ceramic plate 10 with no '. ' ': ' ::
. . :
,, .,: ,:
2~2~28 6 7322~-5 attachments. The dielectric plate 10 i~ supported by a moulded or machined insulating frame, generally indicated at 11~ made of a material with good high voltage insulating properties such as polytetrafluoroethylene or polyvinylchloride. The frame 11 includes a generally U-shaped first, or base, member 12 having a bottom portion 13 and opposed upright end portions 15 and 16 having at least their inner faces 18 and 20 extending at right angles from ~he bottom portion 13. Parallel slots or grooves 21,22 are formed in the end faces 18,20 to guide, support and accurately locate the dielectric plate 10 in an air gap between two metal plates 14 and 15.
The frame 11 further comprises first and second opposed parallel uprlght side members 24,25 attached to the middle of the bottom portion 13 by fastener means such as nuts and bolts 27,28 (Fig. 2) passing through holes 30,31 (Eig. 1) in the side members 24,25 and the bottom portion 13 of base member 12.
As best seen in Figure 2, two flat parallel metal plates 14 and 15 are disposed in recesses 33 and 34 on the inner faces of side members 24 and 25 and secured by metal support studs 3S and 36. Electrical contact with the metal plates can be made through the studs 35 and 36, the electrical terminals 38 being secuxed by nuts 40.
Ozone is produced by applying an alternating high voltage (typically 3000-7500 VAC) to the metal plates 14 and 15.
The metal plates 14 and 15 are spaced in relation to the dielectric plate 10 so that the production of ozone is maximized at the normal operatlng voltage of the device. A gap of between 0.5 to 1.5 mm produces the best ozone yield for such a generator.
: ' ' '~,' '' ' , ,; , "
2~7282~
7 73224~5 For long term stability of the device, the plates 14 and lS are made from a material that resists corrosion in high humidity conditions in the presence of ozone. Titanium is one such material that can be used effectively for this purpose. A thin plate of high alumina ceramic (aluminum oxide) is used for the dielectric plate 10 because it can be provided in a form which is flat and mechanically strong. As the pure titanium electrode is oxidized by the corona discharge, the only oxidation product to be deposited on the alumina dielectric is titanium dioxide. This material is a better dielectric than pure alumina and hence does not degrade the performance of the dielectric plate due to the deposition of a semi-conducting or conducting film of corrosion products. This is not the case when the me~al electrodes are stainless steel, where iron oxides produced by the c~rrosion of the stainless steel form conducting films on the surface of the insulator and ultimately degrade the performance of the ozone generator.
Figure 2 shows porkions 45 and 46 of walls of a caslng or cabine~ for the electrode structure. It also shows a securlty pad 80 attached, for example by adhesive material, to portion 45 of the casing. The upper end of plate 10 is held in place and insulated against vibration by pad 80, which may comprise a non conductive foam material, such as PVC foam. With the casing removed, the plate 10 can be removed from the electrode structure by pulling upward on plate 10.
Figure 3 illustrates a second embodiment of an electrode structure according to the invention. In this embodiment, ~he frame~ generally indicated at 11, comprises a lower member 50, an . ~, . , ~, .
.: ~: : : : :
'. :;~ :,: : ' upper member 51 and two upright side members 53 and 54. A
fastening means (not shown) passes through a hole 55 to secure the member 50 between the lower ends of members 53 and 54, while another fastening means (not shown) passes through a hole 56 to secure member 51 between the upper ends of members 53 and 54. The member 54 has an inwardly directed thickened portion 60 to which is attached a metal electrode plate 14. Although not visible in Figure 3, is will be appreciated that a similar electrode plate is attached to a thickened portion o~ member 53. A hole 61 in member 54 provides access for a stud or other means to connect to plate 14, which stud can ba connected to an AC high voltage source; and identical arrangement is provided for the other plate.
The members 50 and 51 are provided with opposed parallel grooves 62 and 63, respectively, to receive a dlelectric plate 10.
One end of the plate 10 has a handle 47, by means of which it can be slid into or out of the grooves 62 and 63. The electrode structure illustrated in Figure 3 can be enclosed in a casing, not shown, which can include an opening for the handle 47 to extend outwardly of the casing, such as shown in Figure 5 and described hereinafter, so thak the plate 10 can be removed from the electrode structure without removing the casing.
The metal electrodes are supported within the frame 11 so as to be parallel to each other and the dielectric plate 10, and separated by an air gap such that the dis~ance between each metal electrode and the dielectric plate is about 0.5 to 1.5 mm.
A modification of the dielectric plate of Figure 3 is shown in Figures 4a and 4b, where an additional attachment 70 is fixed to the remote end of the dielectric plate 10. This .... . . . ..
,,,,: ::
,, '' , : , ~2~
attachment 70 is in the form of a flexible, ozone resistant, material which can be drawn between the metal electrodes 14 and 15 as the dielectric plate is withdrawn from the device with the ald of the attached handle 47. A suitable material for the cleaning pads 70 is an abrasive pad made by Minnesota Mining and Manufacturing Company (3M) and comprising nylon and an abrasive substance. The pads 70 may be aktached to the dielectric plate 10 with double-sided plastic tape made by 3M and sold under the trade-mark SCOTCH BRAND. Tape sold under the trade-mark VELCRO
has also been found to be suitable. The ends of the metal electrodes may be shaped in such a way that they form a tapered antry for the cleaning attachment 70. The compression of the attachment ~0 as it is withdrawn through the gap between the metal electrodes, serves ~o clean the adjacent surfaces of ~he metal electrodes of particulate materials which may accumulate on these surfaces during the operation of the device.
Since the titanium metal electrodes do not physically degenerate and since the inner surfaces of the electrodes can be cleaned by the attachment on the dielectrlc plate, the device can be easily serviced and returned to full operating efficiency by either cleaning o~ the surface of the dielectric material and replacement of the same, or replacing the dielectric material with a new equivalenk part. Both operations require no dismantling of the structure of the generator and can be done quickly and easily so that servicing of the device is a simple operation.
All configurations of the generator are designed to produce ozone when an alternating voltage of between 3000 and 7500 volts is applied to the metal electrodes. Both electrodes are ~ " ',, " ~, ' . " ', .. .-: . .: .
, , ~ ;, : : ':
."
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2~2~
designed to be at full potentlal so that no grounding of one of the high voltage electrodes i5 necessary. However, the design also allows for the grounding of one of the electrodes, if this ls desirable in certain applications of the generator. The preferred gap between the ~etal electrodes ls about 1.5 to 2.0 mm so that with a dielectric of thickness of about 0.7 mm, each air yap between the dielectric and the adjacent metal electrode is about 0.5 to 0.6 mm. A wide range of values for this air gap can be used, however, the values selected are provlded ~or the most efficient production of ozone from the device.
~ith a dielectric of alumina ceramic plate of about 10 cm x 15 cm and metallic electrodes of about 5 cm x 10 cm, a generator of this ~ype can produce about 250 mg/hr of ozone from dry air at an alternating voltage of 6 kV, RMS at 60 Hz. Ozone generators of increased capacity can be manufactured from identical parallel plate units, mountled physically in parallel and operated electrically in parallel off khe same transformer.
Furthermore, higher levels of ozone can be produced by increasing the overall size of the electrodes.
In all embodlments of the invention, the distanca from the outer edge of the metal electrodes 14 and 15 to the extreme perimeter of the dielectric plate 10, is sufflcient to prevent a direct electrical arc between the metal plates, even when contamination on the lnsulatlny frame 11 may be sufficient to cause some electrical conductivity to the grounded mounting of the lnsulating frame 11. For a high purity alumina dielectric, and the voltages used on the device, this distance is about 15 to 20 mm.
..
:; ,:
: , , , ,; : . .
2~72828 11 7322~-5 Ozone produced by the apparatus shown in the Figures is dispersed into the local environment with the aid of an electric fan. This serves to blow air through the gaps of the parallel plate device and also disperses the ozone air mixture into the volume to be ozonated. The free air displacement of this fan needs to be sufficient to lîmit the concentration of ozone at the front surface of the ozone generator to a value that is low enough to be acceptable within safety limits. The total ozone output of the generator is controlled by either controlling the voltage applied to the electrodes or by cycling the generator at full voltage for various periods of time. For example, if the generator is on for one second out of every 10 seconds and this cycle is repeated continuously, the average output of the genera~or is 10% of that ~hich it would produce if the full power was applied continuously to the device. Such electronic controls are well within the skill of persons skilled in the art. A
general configuration of ~he device is shown in Figure 5, where 71 is the parallel plate ozone generator, 72 the high voltage transformer, 73 the fan, 74 the ozone output control system and 75 the housing of ~he device. A unique $eature of the system is that in one configuration of the device, the dielectric plate of the parallel plate ozone generator can be removed from the ozone generator from outside the housing of ~he assemhled ozone generating system. This permits easy replacement of the dielectric plate and/or cleaning of the metal electrode assembly when the cleaning attachment ls affixed to the dielectric plate.
. : - :: . - . :
... .:: : . ,;
: ' . ~ ~ : . ;
established in the intervening air gap. Ozone is produced ln this corona discharge and direct arcing between the plates is prevented by the presence of the solid dielectric material The basic phys.tcs and chemistry of the production of the ozone by this means is well known and documented in the text "Ozone" by Horvarth, Bilitzky and H~ter, Elsevier, (1985).
The production of ozone by silent corona discharge in an apparatus with parallel plate electrode structures has been used for many years. An early U.S. Pat. No. 991,767 issued on May 11, 1911 to Armstrong described a parallel plate generator wlth sheet glass dielectrics and adjacent and parallel metal electrodes made from either copper gauze or metals such as tin foil. Air was blown between the plates while a high tension A.C. transformer produced a silent electric discharge in the air gap between the metal plates and the dielectric materials. Many other similar parallel plates devices have been described, such as in U.S.
Patent 2,345,789, issued on April 4, 1944 to Daily. Here, metal electrodes of wire screen materials or aluminum plates were bonded to ylass or other dielectrics and ozone produced in the air gap between the alternate dielectric and metal plates of the structure.
The dielectric plates of ozone generators are generally made from glass, mica or dielectric materials such as alumina. A
recent patent, U.S. Paten~ No. 4,892,713 issued on Jan. 9, l99O to Newman, describes a parallel plate ozone generator with a solid plate ca~hode separated from a porcelain dielectric with insulating spacers and a mesh anode directly contacting the opposing side of the dielectric. The configuration is basically .
, ,' ' ' :~ :' '' '" ' :
:
: .. :; .
~072~28 3 73~24-5 that of the standard parallel plate ozone generator, and ozone is extracted from the structure by blowing air through the gaps in the structure in which ozone is formed by the action of an alternating high volkage applied to the metal electrode structures.
Previously described parallel plate ozone generators suffe~ from loss of efficiency ln ozone production as a function of time, particularly when they are used to produce ozone from unprocessed room air. With the passage of moist and contaminated air through the ozone generator several forms of contamination develop on the surface o~ the dielectric material and the opposing surfaces of the metal electrodes. Contamination on the dielectric results from the accumulation of organic contaminants from the air and from reaction products of ozone with impurity gases in the air. This film of contamination is generally hydroscopic and the adsorption of water by the ~ilm causes a conductive layer to develop on the surface of the dielectric. In the presence of this slightly electrically conducting film the efficiency for ozone production from the device drops so that in time the dielectric has to be cleaned or replaced. In addition to the above contamlnation sources, the dielectric becomes contaminated with oxidation products from reactlons with the surface of the metal electrodes. In the case of electrode material such as stainless steel, one of these reaction products i5 hydrated iron oxide which deposit~ as a rust-llke ~ on the surface of the dielectric and degrades the performance of the generator.
In addition to contamination on the surface of the dlelectric, particulate materials build up on the surfaces of " : ~; "
, ~
,; : : , : :, ,, , ~ : ;
2~728~8 the metal electrodes facing the dielectric, mainly by the process of electrostatic precipitation. This particulate contamination reduces the flow rate oE air through the air gaps in the ozone generator and thus reduces the efficiency of ozone production.
SU~IMARY OF THE I~VENTION
The present invention mitigates the above problems by incorporating features into the design of the ozone generator that prevent the ~ormation of conducting oxides on the dielectric.
Further, it allows for in situ cleaning of the active surfaces of the metal electrodes and ease of replacement of the dielectric material.
The ozone generator is designed in such a way that the dielectric plate of the parallel plate structure can be easily removed from the generator by sliding it out from between the fixed metal counter electrodes in su:Ltable guides in an insulating frame. With a cleaning pad attached to the dielectric plate, this action of removing the dielectric plate can also serve to clean particulate matter from the adjacent inner surfaces of the metal counter electrodes. The material of the fixed parallel plate metal counter electrodes is selected so that oxidation products formed by the action of the air, water vapour and ozone have a higher dielectric constant than the material of the dielectric plate. ~s a result, as oxidation products deposit on the dielectric plate, there is no loss of efficiency of the ozone generator due to the electrical conductivi.ty of these products, as is the case for commonly used electrode materials such as stainless steel.
In accordance with a broad aspect of this invention , ~ ,. . : . . ;
:
~0728~8 ~here is provided a parallel plate electrode structure for an ozone generator comprisiny an insulating frame having means for supporting first and second metal electrode plates in parallel spaced apart relation and guide means for slidably receiving a plate of dielec~ric material and releasably holding it in a position between and spaced from said metal electrode plates.
BRI~F DE9CRIPTIO~ OF THE DRA~I~GS
Figure 1 is a perspective view of one embodiment of the electrode structure according to the invention.
Flgure 2 is an end view of the electrode structure of the first embodlment of the invention.
Figure 3 is a perspective of another embodiment of the invention, where the dielectric plate can be removed in a direction at right angles to that of Figure 1.
Figures 4a and 4b are views of one form ol the dielectric plate where a felt like pad of cleaning material is bonded parallel to-one edge of the dielectric plate. In addition, a handle 47 is attached to the other end.
Flgure 5 is a view of an ozone generator within an enclosure containing a fan, high voltage transformer and necessary control equipment for the operation of the generator and from which the diele~tric plate can be removed from the generator from outside the ~eneral enclosure.
DESCRIPTION OF THE PREFERR~D EHBODIME~T
Figures 1 and 2 illustrate a first embodiment of the electrode structurer accordiny to the lnvention, for an ozone yenerator. The structure lncludes a dielectric plate of aluminum oxide in the form of an alumina ceramic plate 10 with no '. ' ': ' ::
. . :
,, .,: ,:
2~2~28 6 7322~-5 attachments. The dielectric plate 10 i~ supported by a moulded or machined insulating frame, generally indicated at 11~ made of a material with good high voltage insulating properties such as polytetrafluoroethylene or polyvinylchloride. The frame 11 includes a generally U-shaped first, or base, member 12 having a bottom portion 13 and opposed upright end portions 15 and 16 having at least their inner faces 18 and 20 extending at right angles from ~he bottom portion 13. Parallel slots or grooves 21,22 are formed in the end faces 18,20 to guide, support and accurately locate the dielectric plate 10 in an air gap between two metal plates 14 and 15.
The frame 11 further comprises first and second opposed parallel uprlght side members 24,25 attached to the middle of the bottom portion 13 by fastener means such as nuts and bolts 27,28 (Fig. 2) passing through holes 30,31 (Eig. 1) in the side members 24,25 and the bottom portion 13 of base member 12.
As best seen in Figure 2, two flat parallel metal plates 14 and 15 are disposed in recesses 33 and 34 on the inner faces of side members 24 and 25 and secured by metal support studs 3S and 36. Electrical contact with the metal plates can be made through the studs 35 and 36, the electrical terminals 38 being secuxed by nuts 40.
Ozone is produced by applying an alternating high voltage (typically 3000-7500 VAC) to the metal plates 14 and 15.
The metal plates 14 and 15 are spaced in relation to the dielectric plate 10 so that the production of ozone is maximized at the normal operatlng voltage of the device. A gap of between 0.5 to 1.5 mm produces the best ozone yield for such a generator.
: ' ' '~,' '' ' , ,; , "
2~7282~
7 73224~5 For long term stability of the device, the plates 14 and lS are made from a material that resists corrosion in high humidity conditions in the presence of ozone. Titanium is one such material that can be used effectively for this purpose. A thin plate of high alumina ceramic (aluminum oxide) is used for the dielectric plate 10 because it can be provided in a form which is flat and mechanically strong. As the pure titanium electrode is oxidized by the corona discharge, the only oxidation product to be deposited on the alumina dielectric is titanium dioxide. This material is a better dielectric than pure alumina and hence does not degrade the performance of the dielectric plate due to the deposition of a semi-conducting or conducting film of corrosion products. This is not the case when the me~al electrodes are stainless steel, where iron oxides produced by the c~rrosion of the stainless steel form conducting films on the surface of the insulator and ultimately degrade the performance of the ozone generator.
Figure 2 shows porkions 45 and 46 of walls of a caslng or cabine~ for the electrode structure. It also shows a securlty pad 80 attached, for example by adhesive material, to portion 45 of the casing. The upper end of plate 10 is held in place and insulated against vibration by pad 80, which may comprise a non conductive foam material, such as PVC foam. With the casing removed, the plate 10 can be removed from the electrode structure by pulling upward on plate 10.
Figure 3 illustrates a second embodiment of an electrode structure according to the invention. In this embodiment, ~he frame~ generally indicated at 11, comprises a lower member 50, an . ~, . , ~, .
.: ~: : : : :
'. :;~ :,: : ' upper member 51 and two upright side members 53 and 54. A
fastening means (not shown) passes through a hole 55 to secure the member 50 between the lower ends of members 53 and 54, while another fastening means (not shown) passes through a hole 56 to secure member 51 between the upper ends of members 53 and 54. The member 54 has an inwardly directed thickened portion 60 to which is attached a metal electrode plate 14. Although not visible in Figure 3, is will be appreciated that a similar electrode plate is attached to a thickened portion o~ member 53. A hole 61 in member 54 provides access for a stud or other means to connect to plate 14, which stud can ba connected to an AC high voltage source; and identical arrangement is provided for the other plate.
The members 50 and 51 are provided with opposed parallel grooves 62 and 63, respectively, to receive a dlelectric plate 10.
One end of the plate 10 has a handle 47, by means of which it can be slid into or out of the grooves 62 and 63. The electrode structure illustrated in Figure 3 can be enclosed in a casing, not shown, which can include an opening for the handle 47 to extend outwardly of the casing, such as shown in Figure 5 and described hereinafter, so thak the plate 10 can be removed from the electrode structure without removing the casing.
The metal electrodes are supported within the frame 11 so as to be parallel to each other and the dielectric plate 10, and separated by an air gap such that the dis~ance between each metal electrode and the dielectric plate is about 0.5 to 1.5 mm.
A modification of the dielectric plate of Figure 3 is shown in Figures 4a and 4b, where an additional attachment 70 is fixed to the remote end of the dielectric plate 10. This .... . . . ..
,,,,: ::
,, '' , : , ~2~
attachment 70 is in the form of a flexible, ozone resistant, material which can be drawn between the metal electrodes 14 and 15 as the dielectric plate is withdrawn from the device with the ald of the attached handle 47. A suitable material for the cleaning pads 70 is an abrasive pad made by Minnesota Mining and Manufacturing Company (3M) and comprising nylon and an abrasive substance. The pads 70 may be aktached to the dielectric plate 10 with double-sided plastic tape made by 3M and sold under the trade-mark SCOTCH BRAND. Tape sold under the trade-mark VELCRO
has also been found to be suitable. The ends of the metal electrodes may be shaped in such a way that they form a tapered antry for the cleaning attachment 70. The compression of the attachment ~0 as it is withdrawn through the gap between the metal electrodes, serves ~o clean the adjacent surfaces of ~he metal electrodes of particulate materials which may accumulate on these surfaces during the operation of the device.
Since the titanium metal electrodes do not physically degenerate and since the inner surfaces of the electrodes can be cleaned by the attachment on the dielectrlc plate, the device can be easily serviced and returned to full operating efficiency by either cleaning o~ the surface of the dielectric material and replacement of the same, or replacing the dielectric material with a new equivalenk part. Both operations require no dismantling of the structure of the generator and can be done quickly and easily so that servicing of the device is a simple operation.
All configurations of the generator are designed to produce ozone when an alternating voltage of between 3000 and 7500 volts is applied to the metal electrodes. Both electrodes are ~ " ',, " ~, ' . " ', .. .-: . .: .
, , ~ ;, : : ':
."
; , . ..
2~2~
designed to be at full potentlal so that no grounding of one of the high voltage electrodes i5 necessary. However, the design also allows for the grounding of one of the electrodes, if this ls desirable in certain applications of the generator. The preferred gap between the ~etal electrodes ls about 1.5 to 2.0 mm so that with a dielectric of thickness of about 0.7 mm, each air yap between the dielectric and the adjacent metal electrode is about 0.5 to 0.6 mm. A wide range of values for this air gap can be used, however, the values selected are provlded ~or the most efficient production of ozone from the device.
~ith a dielectric of alumina ceramic plate of about 10 cm x 15 cm and metallic electrodes of about 5 cm x 10 cm, a generator of this ~ype can produce about 250 mg/hr of ozone from dry air at an alternating voltage of 6 kV, RMS at 60 Hz. Ozone generators of increased capacity can be manufactured from identical parallel plate units, mountled physically in parallel and operated electrically in parallel off khe same transformer.
Furthermore, higher levels of ozone can be produced by increasing the overall size of the electrodes.
In all embodlments of the invention, the distanca from the outer edge of the metal electrodes 14 and 15 to the extreme perimeter of the dielectric plate 10, is sufflcient to prevent a direct electrical arc between the metal plates, even when contamination on the lnsulatlny frame 11 may be sufficient to cause some electrical conductivity to the grounded mounting of the lnsulating frame 11. For a high purity alumina dielectric, and the voltages used on the device, this distance is about 15 to 20 mm.
..
:; ,:
: , , , ,; : . .
2~72828 11 7322~-5 Ozone produced by the apparatus shown in the Figures is dispersed into the local environment with the aid of an electric fan. This serves to blow air through the gaps of the parallel plate device and also disperses the ozone air mixture into the volume to be ozonated. The free air displacement of this fan needs to be sufficient to lîmit the concentration of ozone at the front surface of the ozone generator to a value that is low enough to be acceptable within safety limits. The total ozone output of the generator is controlled by either controlling the voltage applied to the electrodes or by cycling the generator at full voltage for various periods of time. For example, if the generator is on for one second out of every 10 seconds and this cycle is repeated continuously, the average output of the genera~or is 10% of that ~hich it would produce if the full power was applied continuously to the device. Such electronic controls are well within the skill of persons skilled in the art. A
general configuration of ~he device is shown in Figure 5, where 71 is the parallel plate ozone generator, 72 the high voltage transformer, 73 the fan, 74 the ozone output control system and 75 the housing of ~he device. A unique $eature of the system is that in one configuration of the device, the dielectric plate of the parallel plate ozone generator can be removed from the ozone generator from outside the housing of ~he assemhled ozone generating system. This permits easy replacement of the dielectric plate and/or cleaning of the metal electrode assembly when the cleaning attachment ls affixed to the dielectric plate.
. : - :: . - . :
... .:: : . ,;
: ' . ~ ~ : . ;
Claims (10)
1. A parallel plate electrode structure for an ozone generator comprising an insulating frame having means for supporting first and second metal electrode plates in parallel spaced apart relation and guide means for slidably receiving a plate of dielectric material and releasably holding it in a position between and spaced from said metal electrode plates.
2. An electrode structure as claimed in claim 1 wherein said insulating frame comprises a generally U-shaped base member having a bottom portion and opposed upright end portions, said end portions having inner faces extending at right angles from said bottom portion, said end faces each having a slot or groove comprising said guide means to guide, support and accurately locate said plate of dielectric material between and spaced from said metal electrode plates.
3. An electrode structure as claimed in claim 2 wherein said frame further comprises first and second opposed parallel upright side members attached to said bottom portion intermediate said upright end portions of said base member, said side members having opposed recessed inner face portions to which said electrode plates are attached.
4. An electrode structure as claimed in claim 1 wherein said insulating frame comprises upper and lower members secured between spaced apart opposite ends of two upright members, said upper and lower members having opposed faces each provided with a slot or groove comprising said guide means to guide, support and accurately locate said plate of dielectric material between and spaced from said metal electrode plates.
5. An electrode structure as claimed in claim 4 wherein said electrode plates are attached to opposed surfaces of said upright members.
6. An electrode structure as claimed in any one of claims 1 to 5 wherein said metal electrode plates are formed of titanium.
7. An electrode structure as claimed in any one of claims 1 to 5 wherein said metal electrode plates are formed of titanium and said plate of dielectric material is formed of mica, glass, porcelain or ceramic alumina.
8. An electrode structure as claimed in any one of claims 1 to 5 wherein said plate of dielectric material is larger than said metal electrode plates.
9. An electrode structure as claimed in any one of claims 1 to 5 wherein said plate of dielectric material is larger than said metal electrode plates, said plate of dielectric material having an end to which is attached a handle to facilitate slidably moving said plate of dielectric material in said guide means.
10. An electrode structure as claimed in claim 9 wherein an end of said plate of dielectric material is provided with flexible, ozone resistant material wherein removing said plate of dielectric material results in cleaning opposed surface of said metal electrode plates.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2072828 CA2072828A1 (en) | 1992-06-30 | 1992-06-30 | Ozone generator |
| PCT/CA1993/000265 WO1994000381A1 (en) | 1992-06-30 | 1993-06-25 | Ozone generator |
| AU44146/93A AU4414693A (en) | 1992-06-30 | 1993-06-25 | Ozone generator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2072828 CA2072828A1 (en) | 1992-06-30 | 1992-06-30 | Ozone generator |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2072828A1 true CA2072828A1 (en) | 1993-12-31 |
Family
ID=4150094
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2072828 Abandoned CA2072828A1 (en) | 1992-06-30 | 1992-06-30 | Ozone generator |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU4414693A (en) |
| CA (1) | CA2072828A1 (en) |
| WO (1) | WO1994000381A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| HU4286U (en) * | 2013-03-05 | 2013-07-29 | Peter Koltay | Ozonizer with gas blowing system |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1028985A (en) * | 1964-10-29 | 1966-05-11 | Benjamin Caplan | Ozone generators |
| DE2644978C3 (en) * | 1976-10-06 | 1980-10-30 | Pavel Dr.-Phys. 3257 Springe Imris | Device for the production of ozone |
-
1992
- 1992-06-30 CA CA 2072828 patent/CA2072828A1/en not_active Abandoned
-
1993
- 1993-06-25 WO PCT/CA1993/000265 patent/WO1994000381A1/en active Application Filing
- 1993-06-25 AU AU44146/93A patent/AU4414693A/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| WO1994000381A1 (en) | 1994-01-06 |
| AU4414693A (en) | 1994-01-24 |
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| Date | Code | Title | Description |
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| FZDE | Dead |