Abstract:
An ozone generator including a pair of electrodes separated by a dielectric element including a plurality of passages defining a corona discharge zone. In one embodiment of the invention, the passages may be convoluted in the sense that the lengths of the passages defining the corona discharge zone are greater than the length of the first and second electrodes and the dielectric element. This configuration provides for an extended period of exposure of the gas to the electric field and may result in production of ozone exhibiting improved stability and oxidation rate. In one embodiment, inner and outer concentric electrodes are held in spaced apart relationship by a concentric tubular dielectric. A corona discharge zone is defined between an inner surface of the outer tubular electrode and the outer surface of the concentric tubular dielectric by a plurality of passages formed on the outer surface of the concentric tubular dielectric.

Description:
BACKGROUND  
         [0001]    1. Field of Invention  
           [0002]    This invention relates to ozone production for domestic and industrial applications, and more particularly, to an improved ozone generator and system.  
           [0003]    2. Background of the Invention  
           [0004]    Ozone gas (O 3 ) is a powerful oxidizing agent that has an oxidation potential about 1.5 times greater than that of chlorine. Ozone is used for various oxidation processes, water and air treatment and as a reactant in many chemical syntheses. Ozone is an unstable gas, which may be produced by exposing oxygen to an electric field derived from a high voltage alternating current. Ozone generators create an electric field by corona discharge between opposing electrodes with intervening dielectric. Corona discharge involves passing air between positively and negatively charged electrodes separated by a dielectric material and a discharge gap. In the process, the air in the highly-charged electric field between the electrodes becomes ionized and conductive such that oxygen in the air is converted to ozone.  
           [0005]    Conventional ozone generators require substantial amounts of energy in order to produce a sufficient volume of ozone for commercially feasible use. For example, a conventional corona discharge ozone generator may require 100 kilowatt-hours of energy to produce 18 pounds of ozone in a 24-hour period. As a result, the cost of producing ozone can be a significant factor in considering the use of ozone as an oxidizing agent for any given process.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention is directed to an ozone generator including a pair of electrodes separated by a dielectric and at least one passage defining a corona discharge zone. The present invention is directed to an ozone generator used to generate ozone by flowing air, or other suitable gas including oxygen, through a corona discharge zone between a pair of charged elements or electrodes. In one embodiment of the invention, pressurized flowing air, or other suitable gas including oxygen, passes along a plurality of passages positioned between the one of the pair of charged elements or electrodes and the dielectric. The plurality of passages may be defined by a plurality of grooves formed on a surface of the dielectric element and a contacting surface of an electrode. In the alternative, the plurality of grooves may be formed in a surface of the electrode and the plurality of passages may be defined by the plurality of grooves formed on a surface of the electrode and a contacting surface of the dielectric element. In one embodiment of the invention, the grooves, and therefore the passages, are convoluted in the sense that the length of each passage is greater than the length of the dielectric material. As a result, a gas flowing along the plurality of passages must travel a distance greater than the length of the dielectric element in order to pass through the corona discharge zone. This configuration provides for an extended period of exposure of the gas to the electric field and may result in increased yields in the production of ozone, and the production of ozone exhibiting improved stability and oxidation rate.  
           [0007]    In a preferred embodiment of the invention, inner and outer concentric tubular electrodes are held in spaced apart relationship by a concentric tubular dielectric. A corona discharge zone is defined between an inner surface of the outer tubular electrode and the outer surface of the concentric tubular dielectric by a plurality of passages formed on the outer surface of the concentric tubular dielectric. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a schematic representative view of an ozone generating system;  
         [0009]    [0009]FIG. 2 is a representative perspective view of an ozone generator;  
         [0010]    [0010]FIG. 3 is a representative side cutaway view of an ozone generator;  
         [0011]    [0011]FIG. 4 is a representative partial cut-away side detail view of an ozone generator;  
         [0012]    [0012]FIG. 5 representative partial cut-away side detail view of an ozone generator;  
         [0013]    [0013]FIG. 6 is a representative cross-sectional view of an ozone generator taken substantially along lines  6 - 6  in FIG. 3;  
         [0014]    [0014]FIG. 7A is representative side view of a dielectric element for an ozone generator;  
         [0015]    [0015]FIG. 7B is representative side view of a dielectric element for an ozone generator; and  
         [0016]    [0016]FIG. 8 is a representative perspective view of an alternate embodiment of an ozone generator according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0017]    [0017]FIG. 1 is a representative perspective view of ozone generating system  10  including housing  11  which provides a protective enclosure for ozone generators  100 A,  100 B and  100 C, each electrically coupled to transformer  20  which is electrically coupled to power supply  25 . Ozone generating system  10  also includes controller  40  for controlling various functions and operations of ozone generating system  10 . Ozone generating system  10  includes compressor  30  which is pneumatically connected to each of the ozone generators  100 A,  100 B and  100 C for providing a flow of air through each of the ozone generators  100 A,  100 B and  100 C. Compressor  30  is pneumatically connected to outlet  154  in such a manner that air is drawn through each of the ozone generators  100 A,  100 B and  100 C under a vacuum. Compressor  30  is an oiless compressor and has a preferred rated output in the range of 20-80 psi, and preferably an output substantially equal to 75 psi. Inlet  153  includes check valve  50  which permits pneumatic communication with each of the ozone generators  100 A,  100 B and  100 C in an inflow direction only. Outlet  154  is pneumatically connected to outlet compressor inlet  52 . Compressor outlet  53  may be fluidly connected to a fluid stream flow F contained within pipe  55  for direct treatment of the fluid with ozone. Alternatively, compressor outlet  53  may be fluidly connected to a vessel for storage or treatment, not shown. Control valve  54  prohibits a fluid flow from pipe  55  upstream to compressor  30 . Alternatively, an inline check valve may be used to prevent backflow to compressor  30 .  
         [0018]    [0018]FIGS. 2 and 3 show ozone generator  100  electrically coupled to transformer  20 . Ozone generator  100  includes first terminal  112  conductively connected to first electrode  110  and second terminal  122  conductively connected to second electrode  120 . Inlet  153  pneumatically communicates through wall  121  of second electrode  120  with inlet plenum  138 , shown in FIG. 3, and outlet  154  pneumatically communicates through wall  121  with outlet plenum  139 , shown in FIG. 3. End caps  125 A and  125 B provide protection against impact and are configured to provide a pneumatic seal as shown in FIG. 3.  
         [0019]    Referring to FIG. 3, ozone generator  100  is shown including first electrode  110  and second electrode  120  held in spaced apart relationship by dielectric element  130 . Dielectric element  130  is configured as shown to include a plurality of grooves  133 , which together with the fit between an outer surface of dielectric element  130  and an inner surface of second electrode  120 , form a plurality of passages  132  which collectively form corona discharge zone  135 . The fit between second electrode  120  and dielectric element  130  is preferably such that each of the resulting plurality of passages  132  are substantially pneumatically isolated from adjoining passages. This configuration results in a structure including a plurality of passages  132  through which a gas can flow between first electrode 110  and second electrode  120  without migrating laterally between passages.  
         [0020]    In the embodiment of ozone generator  100  shown in FIG. 3, inner electrode  110 , dielectric element  130 , and second electrode  120  are all at least generally cylindrical in shape. First electrode 110  is shown formed as a solid cylindrical billet, although other configurations including tubular configurations are possible. First electrode 110  fits coaxially within dielectric element  130 , and second electrode  120  fits coaxially around dielectric element  130 . Preferably, the fit between first electrode 110  and dielectric element  130  is a clearance fit in the range of 0.005 inches to 0.010 inches and more preferably substantially equal to 0.007 inches. First electrode 110  In other embodiments, other shapes are possible for first electrode 110 , dielectric element  130 , and second electrode  120  without departing from the basic function of the ozone generator  100 . For example, these elements can all have at least generally rectangular cross-sections, ovoid cross-sections, or other configurations that produce ozone in substantially the same way as ozone generator  100 .  
         [0021]    In one embodiment of the invention, dielectric element  130  comprises a dielectric material having a minimum dielectric loss of 450 amps per million. In another embodiment of the invention, dielectric element  130  comprises a dielectric material having a dielectric loss in the range of 450-1000 amps per million.  
         [0022]    In one embodiment of the invention, dielectric element  130  comprises a dielectric material having a minimum dielectric strength of 375 V/mil. In another embodiment of the invention, dielectric element  130  comprises a dielectric material having a dielectric strength in the range of 375-1000 V/mil. In another embodiment of the invention, dielectric element  130  comprises a dielectric material having a dielectric strength substantially equal to 450 V/mil. Dielectric strength is defined as the maximum voltage a material can withstand without conducting electricity through the thickness of the material expressed in volts per mil thickness of material. In addition, dielectric element  130  preferably comprises a dielectric material having a maximum operating temperature equal to or greater than 275° F. In addition, dielectric element  130  preferably comprises a dielectric material having a specific gravity equal to or greater than 1.20 g/cm 3 .  
         [0023]    In one embodiment of the invention, dielectric element  130  comprises a material identified as Polysulfone manufactured by Saint Gobain Performance Plastics. Preferably, a cylindrical tubular segment formed of Polysulfone material is machined to form dielectric element  130 . Following machining, dielectric element  130  is heat treated by soaking at a temperature in the range of 300-400 degrees Fahrenheit, and more preferably at a temperature substantially equal to 392 degrees Fahrenheit, for a period of one hour.  
         [0024]    In other embodiments of the invention, dielectric element  130  comprises a material selected from a group of materials including polysulfone such as Udel®, a polyyetherimide such as Ultem®, a Polyethersulfone/Polyarylsulfone such as Radel® and a Polyetherether Ketone, PEEK. Another suitable material that can be used for dielectric element  130  is a dielectric ceramic material.  
         [0025]    In one embodiment, first electrode  110  may be formed of a material having a different electrical conductivity than second electrode  120 . In another embodiment of the invention, first electrode 110  may be formed of a material having a relatively lower conductivity than second electrode  120 . For example, first electrode 110  may comprise an aluminum alloy and second electrode  120  may comprise a stainless steel alloy having a relatively lower conductivity than the aluminum alloy. In one embodiment, first electrode 110  is comprised of an aluminum alloy billet. In other embodiments, first electrode 110  is configured as a tubular segment and includes a wall thickness of 0.50 inch. Other materials having other wall thicknesses can be used for first electrode 110 . Second electrode  120  may have a wall thickness substantially equal to 0.25 inch where second electrode  120  is comprised of a stainless steel alloy. In other embodiments, other materials having other wall thicknesses can be used for second electrode  120 .  
         [0026]    As shown in FIG. 3, ozone generator  100  is electrically connected to transformer  20  which applies a high voltage current between first electrode 110  and second electrode  120 . In one embodiment, transformer  20  is a conventional step-up transformer of 120 volts AC at 890 volt-amps primary, and 15,000 volts AC at 60 milliamps secondary. In other embodiments, other transformers may be used. Transformer  20  has a primary positive lead  21 , primary negative lead  22 , secondary negative lead  23 , and secondary positive lead  24 . Primary positive lead  21  and primary negative lead  22  are conductively connected to power supply  25 . Secondary negative lead  23  is connected to first electrode 110  at first terminal  112 , and secondary positive lead  24  is connected to second electrode  120  at second terminal  122 .  
         [0027]    [0027]FIGS. 4 and 5 are representational cutaway details showing first electrode  110 , second electrode  120  and dielectric element  130 . Dielectric element  130  includes a plurality of grooves  133  which, together with the fit between an outer surface of dielectric element  130  and an inner surface of second electrode  120 , form a plurality of passages  132  which collectively form corona discharge zone  135 .  
         [0028]    Referring to FIG. 4, outlet  154  pneumatically communicates with outlet plenum  139  through wall  121  of second electrode  120  for expelling a flow of gas including ozone. FIG. 4 also shows to advantage secondary negative lead  23  conductively connected to first terminal  112  which is conductively connected to first electrode 110 .  
         [0029]    As seen in FIG. 5, inlet  153  pneumatically communicates with inlet plenum  138  through wall  121  of second electrode  120 . Inlet plenum  138  is fluidly connected to outlet plenum  139  and a flow of gas, such as air, passes along plurality of passages  132  from inlet plenum  138  to the outlet plenum  139 , as seen in FIG. 3. Gas passing through plurality of passages  132  is exposed to an electrical field in corona discharge zone  135 . FIG. 5 also shows to advantage secondary positive lead  24  conductively connected to second terminal  122  which is conductively connected to second electrode 120 .  
         [0030]    Inlet plenum  138 , outlet plenum  139  and corona discharge zone  135  are pneumatically isolated between dielectric element  130  and second electrode  120  as follows. As shown in FIG. 4, o-ring  141  is disposed in groove  142  and provides a substantially air-tight seal between dielectric element  130  and end cap  125 A. As shown in FIG. 5, o-ring  143  is disposed in groove  144  and provides a substantially air-tight seal between the dielectric element  130  and end cap  125 B.  
         [0031]    [0031]FIG. 6 is a cross-sectional view of dielectric element  130  taken substantially along lines  6 - 6  in FIG. 3 in accordance with a preferred embodiment of the invention. Dielectric element  130  has an inner surface radius  131 , an outer surface radius  134 , and a resulting nominal wall thickness  136 .  
         [0032]    [0032]FIG. 7A is a side elevation of dielectric element  130  in accordance with a preferred embodiment of the invention. The plurality of grooves  133  are formed on an outer surface of dielectric element  130  and are uniformly spaced apart from each other, extending along spiral paths around dielectric element  130 . The plurality of grooves  133  extend from inlet plenum  138  at one end and outlet plenum  139  at the other end. The spiral paths of the plurality of grooves  133  increases the time period that the gas resides between first electrode 110  and second electrode  120  compared to a plurality of straight passages which lie parallel to a longitudinal axis of the dielectric element. In other embodiments, the plurality of grooves  133  can be non-uniformly spaced apart from each other and/or extend along other paths from inlet plenum  138  to the outlet plenum  139 .  
         [0033]    [0033]FIG. 7B is a side elevation view of a dielectric element  230  in accordance with an alternate embodiment of the invention. In this embodiment, the dielectric element  230  has a plurality of serpentine grooves  233  that are uniformly spaced apart from one another and extend from the inlet plenum  238  to the outlet plenum  239 . Channel paths extending along spiral or serpentine paths over the outer surface of the dielectric element are but two examples of circuitous paths that could be used to achieve an extended exposure period.  
         [0034]    As best seen in FIG. 1, ozone can be generated using the ozone generator  100  by flowing a gas comprising oxygen at a selected pressure from the inlet  153  through the plurality of passages  132  toward the outlet  154 , while selected electric potentials are maintained on first electrode 110  and second electrode  120 . In one embodiment, ozone is generated by introducing air through inlet  153  into inlet plenum  138 . In other embodiments, ozone can be generated by using air and other gases comprising oxygen at other pressures. Once the air enters the inlet plenum  138 , it travels through plurality of passages  132  collectively forming corona discharge zone  135  between the charged inner and second electrodes  110  and  120 .  
         [0035]    In one embodiment of the invention, second electrode  120  comprises a 0.50 inch thick aluminum alloy, first electrode 110  comprises a 0.25 inch thick stainless steel alloy and dielectric element  130  includes a tubular dielectric material formed of polysulfone. Referring to FIG. 6, the polysulfone dielectric element  130  includes an inner surface radius  131  of 1.75 inches, an outer surface radius  134  of 2.25 inches and a nominal wall thickness  136  substantially equal to 0.50 inch. In other embodiments, the nominal wall thickness  136  can be different than 0.50 inch. The plurality of grooves  133  may each include a generally U-shaped cross-section defined by adjacent upright wall segments  146  and adjoining root wall segment  147 . In one embodiment of the invention, root wall segment  137  includes a root wall thickness  137  in the range of 0.030-0.080 inch, and preferably substantially equal to 0.063 inch. In one embodiment of the invention, the thickness of each upright wall segment  146  is approximately 0.030-0.080 inch, and preferably substantially equal to the thickness of the root wall segment  137 , or in this instance 0.063 inch. The thickness of the root wall segment  137  and upright wall segments  146  can be more or less than 0.063 inch based upon the strength of the electric field, the type of dielectric material, and other factors. The negative electric potential may be in the range of approximately −5,000 to −20,000 volts and the positive electrical potential is approximately 5,000 to 20,000 volts. More preferably, the negative electric potential is approximately −15,000 volts and the positive electric potential is approximately 15,000 volts. In other embodiments, the electric potentials applied to the first and second electrodes  110  and  120  can be more or less than these potentials. As the air flows through the plurality of passages  132  in corona discharge zone  135 , at least some of the oxygen in the air is converted to ozone by the time that the flow reaches outlet  154 .  
         [0036]    [0036]FIG. 8 is a partial cutaway isometric view of a planar ozone generator  400  in accordance with an alternate embodiment of the invention. Ozone generator  400  has a generally planar first electrode  410 , a generally planar second electrode  420 , and a generally planar dielectric element  430  sandwiched between the first and second electrodes  410  and  420 , respectively. A plurality of grooves  433  are formed in the dielectric element  430  and span between an inlet plenum  438  and an outlet plenum  439 . Inlet  461  is attached to second electrode  420  and fluidly communicates with inlet plenum  438 . Similarly, outlet  462  is attached to second electrode  420  and fluidly communicates with outlet plenum  439 . Inlet plenum  438  fluidly communicates with outlet plenum  439  via the plurality of passages  432 . Air, or other gas including oxygen, is introduced through inlet  461  into inlet plenum  438 . Rectangular seal  442  is positioned in groove  434  in dielectric element  430  creating a substantially air-tight seal between the dielectric element  430  and second electrode  420  that surrounds the plurality of grooves  433 , inlet plenum  438  and outlet plenum  439 .  
         [0037]    First terminal  412  is conductively connected to first electrode  410  and second terminal  422  is conductively connected to second electrode  420 . Ozone generator  400  may be electrically connected to transformer  20  which applies a high voltage current between first electrode  410  and second electrode  420 . Secondary negative lead  23  is connected to the second terminal  122 , and secondary positive lead  24  is connected to first terminal  412 .  
         [0038]    Ozone can be generated with the ozone generator  400  in a manner substantially similar to the method employed with ozone generator  100 . Air or another gas with oxygen is introduced at a selected pressure through inlet  461  into inlet plenum  438  passing along the plurality of passages  432  toward the outlet plenum  439 . The gas passes through corona discharge zone  435  defined between first electrode  410  and second electrode  420  and more particularly between inlet plenum  438  and outlet plenum  439  and the plurality of grooves  433  formed on the upper surface of dielectric element  430 , and more particularly in a plurality of passages  432  formed as a result of the fit between the plurality of grooves  433  formed on the upper surface of dielectric element  430  and the lower or inner contacting surface of second electrode  420 . Generated ozone is expelled from outlet  462  to a storage or distribution device, (not shown).  
         [0039]    Like the generally cylindrical ozone generator  100  shown in FIGS. 1 through 6, the generally planar ozone generator  400  may be capable of producing ozone more efficiently than conventional corona discharge ozone generators. In addition, because the basic elements of the planar ozone generator  400  are generally planar in shape, they may be easier to manufacture than the functionally similar, but cylindrically configured, elements of the ozone generator  100 . The planar ozone generator  400  may also be easier to assemble than the cylindrical ozone generator  100 , which requires assembly of coaxially disposed cylindrical elements.  
         [0040]    From the foregoing, it will be appreciated by those of skill in the art that even though specific embodiments of the invention have been described herein for purposes of illustration, various modifications can be made without departing from the spirit or scope of the present invention. In general, the terms in the claims should not be construed to limit the invention to the specific embodiments disclosed in the foregoing description, but should be construed to include all ozone generating systems and ozone generators that operate in accordance with the claims.