Ozone generator

[0002] This application is a continuation-in-part of U.S. patent application Ser. No. 09/057,593, Injected Flow Ozone Generator, filed Apr. 9, 1998 now U.S. Pat. No. 6,139,809.

[0003] The present invention relates to an ozone generator and to a process for converting oxygen into ozone.

[0004] Ozone is a chemical agent used in industrial oxidation, water and air treatment and in many chemical syntheses. Ozone is an unstable gas, which is produced by the disassociation-association of oxygen in an electric field derived from a high voltage alternating sinusoidal current operating at frequencies typically between about 60 and 5000 Hz and voltages frequently above 20 kilovolts. Ozone generators create the electric field by corona discharge between an electrode and opposing electrode with intervening dielectric.

[0005] A tubular type generator 10 is shown in FIG. 1 and is described in Chamblee et al., U.S. Pat. No. 5,552,125. The generator 10 includes a tubular inner electrode 11 and an outer tubular electrode 13 concentric with the inner electrode 11 and mounted so as to define an annular flow path 12 for oxygen containing gas between the electrodes 11, 13. The inner electrode 11 is coated with a dielectric 14 on a surface between the inner 11 and outer 13 electrodes. The inner electrode 11 includes a hollow interior 15 for the passage of coolant. The inner electrode 11 is connected to a voltage source 16 by a high voltage line and the outer electrode is grounded. An oxygen containing gas (O₂) flows into the annular path 12 between the dielectric 14 and outer electrode 13 where a corona discharge between the electrodes 11, 13 converts some oxygen to ozone (O₃). The discharge also generates heat. The heat suppresses ozone generation by converting some product ozone back to oxygen. A coolant 17 is passed into the hollow interior 15 of the inner electrode 11 to prevent heat buildup and consequential loss of product ozone. However, ozone is produced on the interior (inside diameter) of the inner electrode 11, particularly at and near the connection of the high voltage line. The coolant gas can sweep ozone from the interior 15 of the inner electrode 11 into the work area 18. Ozone is a gas that is environmentally deleterious in closed work areas. Sweeping the interior 15 of the inner electrode 11 with a cooling fluid can create an environmental hazard to workers in the vicinity of the ozone generator.

[0006] Another type of ozone generator is shown in FIG. 2, which is reproduced from Conrad et al., U.S. Pat. No. 5,630,990. In FIG. 2, tubular generator 20 includes a first electrode 25 and a second, larger diameter, electrode 26. Electrode 25 has a layer of dielectric material 27 disposed on the surface thereof and is positioned within electrode 26 to form a gap 28. A flow of feed oxygen or oxygen enriched air is directed as shown by the top arrows into a longitudinal spacing between tubular electrode 25 and dielectric 27 and thence as illustrated by the arrows, to discharge gap 28 between tubular electrode 26 and concentric electrode 25/dielectric 27, thence to an exit port near the entry port of the flow of feed oxygen or oxygen enriched air. Heat and ozone produced on the surface of the inside diameter of electrode 25/dielectric 27 are swept by the feed oxygen/oxygen enriched air as a part of the charge to the discharge gap 28.

[0007] The production of ozone by application of corona discharge to oxygen-containing gas is a temperature dependant process. Ozone generators tend to overheat, which results in conversion of ozone back to oxygen thereby decreasing product yield. Additionally, intricacy of the generator structure as required to provide electrical energy to the electrodes can increase the cost of manufacturing the generator structure. There is a need for a simplified generator structure that does not overheat.

[0008] The present invention provides a simplified generator structure that eliminates expensive to manufacture electrical connections to the generator electrodes and that effectively cools for increased ozone yield. The present invention relates to a tubular ozone generator comprising an outer tubular electrode, concentric inner tubular electrode, dielectric between said electrodes to define a corona discharge zone and a tubular gas injector within and concentric with said inner tubular electrode and in conductive electrical contact with the inner tubular electrode.

[0009] Additionally, the invention relates to a plurality of the tubular ozone generators, arranged to provide ozone enriched gas product to a treatment zone.

[0010] Additionally, the invention relates to a tubular ozone generator, comprising concentric inner tubular electrode/dielectric with inner electrode in intimate length-to-length contact with dielectric and outer tubular electrode with corona discharge zone between the inner tubular electrode/dielectric and outer tubular electrode. A dielectric of the inner tubular electrode/dielectric has a sealed end and an open end. The outer tubular electrode has an open exhaust end concentric with the sealed end of the dielectric and a closed end that forms a port with the open end of the dielectric. A tubular gas injector is situated within and concentric with the inner tubular electrode/dielectric and in conductive electrical contact with an electrode portion of the inner tubular electrode/dielectric. The sealed end of the dielectric is sealed with a transparent end cap to permit visual inspection of an electrode of the electrode/dielectric during operation of the generator.

[0011] Finally, the invention relates to a method of producing ozone in an ozone generator comprising an outer tubular electrode, concentric inner tubular electrode, dielectric between the electrodes to define a corona discharge zone and a tubular gas injector within and concentric with the inner tubular electrode. The method comprises providing electrical contact between the inner tubular electrode and an electrical current source by conductive electrical contact between the injector and the inner tubular electrode to provide the electrical discharge zone. A flow of oxygen or oxygen enriched air is injected by the injector into the electrical discharge zone to convert oxygen in the air to ozone.

[0012] The invention is more readily understood and appreciated by reference to the following drawings:

[0013] FIG. 1 shows a prior art ozone generator;

[0014] FIG. 2 shows another prior art ozone generator;

[0015] FIG. 3 shows a front end view of the generator of the present invention;

[0016] FIG. 4 shows a sectional view along the line a—a of the generator of FIG. 3;

[0017] FIG. 5 shows an array of generators of FIG. 3 and FIG. 4 arranged to produce ozone for injection into a treatment zone; and

[0018] FIG. 6 is a schematic representation of an ozone generator treatment system and process of an embodiment of the invention.

[0019] The tubular generator of the invention is characterized by a simple to manufacture design that achieves improved dissipation of heat and ozone without undesirable discharge into the atmosphere. In one embodiment, the inventive generator is fitted with a transparent cap to permit direct observation of the corona discharge. Observation of the corona discharge permits immediate identification of electrode defects. The ozone generator of the present invention can have a sealed end dielectric tube to allow flow path control of feed gas and to permit visual observation of an interior electrode to assure that the interior electrode is properly operating. The ozone generator can permit direct injection of product ozone into a reaction vessel for industrial oxidations, treatments or chemical syntheses.

[0020] These and other features will become apparent from the drawings and following detailed discussion, which by way of example without limitation describe preferred embodiments of the present invention.

[0021] Referring to FIGS. 3 and 4, the generator 30 includes an outer tubular electrode casing 32, which can be stainless steel. Tube 34 is within outer tubular electrode 32 and concentric therewith and comprises a dielectric material such as glass. The dielectric tube 34 terminates in a closed end 36. Inner tubular electrode 38 is adjacent the inner surface of tubular electrode 32 to form an electrode/dielectric. Inner tubular electrode 38 can be made of any material or structure suitable to form an electrode. For example, the electrode 38 can be a solid integral structure such as a tube or a conductive surface coated onto dielectric tube 34. Preferably the inner tubular electrode 38 is a stainless steel mesh structure.

[0022] Outer tubular electrode 32, tubular dielectric 34 and tubular inner electrode 38 are concentric to one another as shown and are separated to form corona discharge zone 40. Outer tubular electrode 32 is capped by transparent end caps 42, 44. The concentric electrodes 32 and 38 and dielectric 34 and the end caps 42, 44 are secured to flanges 46 by means of nut and bolt combinations 48 with gaskets 50 intervening between the end caps 42, 44 and respective flanges 46.

[0023] In a conventional ozone generator, a lead connects inner electrode 38 to a high voltage source. The lead passes from a current source through a sealed aperture through the wall of end cap 42 to connect to electrode 38. The lead creates several problems in electrode structure and in manufacturing the generator. First, the lead must be insulated at entry into the generator through end cap 42. Insulation can create a combustible fire hazard. Additionally, the lead requires separate manufacturing steps to drill the aperture, load and attach the lead and insulate the entry of the lead through the aperture. According to the present invention, the lead is eliminated by providing a circuit completing tubular gas injector 52 of unique design. The injector 52 is shaped to provide contact with the inner electrode 38. In FIGS. 4, 5 and 6, the contact is provided by jut shape 70 along the longitudinal axis of the injector 52. An end of the injector 52 can be electrically energized with the jut 70 providing an electrical contact 71 with the injector 52 to complete the electrical circuit. Advantageously, this arrangement eliminates the lead and concomitant hazard and manufacturing difficulties.

[0024] In the FIGS. 4, 5 and 6, the contacting structure is shown as a jut 70, which is a projection. However, the structure can be any shape that provides conductive electrical contact of the injector 52 with the electrode 38. For example, the injector 52 can be sloped downward to contact and then upward to oxygen injection end 58 or the injector can be gently curved generally from the vicinity of feed gas end 56 to contact 71 and then upward to injection end 58.

[0025] Referring again to FIGS. 3 and 4, ozone containing gas output port 54 connects to corona discharge zone 40 through product end cap 42 to provide a discharge of product ozone gas from the generator 30. Feed air is injected into the generator 40 by means of tubular gas injector 52 at injector feed gas end 56 and is discharged from generator 30 as ozone containing gas from the output port 54. As shown in the preferred embodiment, the tubular gas injector 52 extends concentric with the inner tubular electrode 38, dielectric 34 and outer tubular electrode 32 to terminate in an injector discharge end 58 that is within close proximity to the dielectric tube closed end 36. The extending injector 52 enables injection of feed gas into the generator 30 at a point within proximity to the closed end 36 of dielectric 34 to permit feed gas flow to initially sweep substantially the entire length of the inner surface (inside diameter) of the tubular electrode 38 prior to feed of the gas into corona discharge zone 40. Additionally, discharge of feed gas within a proximity of closed end 36 results in a net lateral flow of feed gas from feed gas end 56 of tubular gas injector 52 to ozone output port 54 of the generator 30.

[0026] Referring to FIG. 5, connector conduit 60 is shown connecting a plurality of ozone generators 30 via respective ports 54 to provide ozone to a treatment zone (not shown). Feed gas conduit 62 provides feed gas to respective tubular gas injectors 52 at injector feed gas ends 56. High voltage is applied to each corona discharge zone 40 of each generator 30 to convert oxygen in the feed gas to ozone. Each inner tubular electrode 38 of each generator 30 is connected to transformer 64 via high voltage lead 66 and is grounded via ground lead 68. Transformer 64 generates high voltage from line voltage 70 to provide corona discharge in each corona discharge zone 40.

[0027] The improved ozone generator of the present invention is particularly advantageous when incorporated as part of a plurality or array of generators as shown in FIG. 5. The inner electrode 38 of generator 30 is prone to defects that result in improper operation. Closed end 36 of dielectric 34 can be a transparent material to permit visual observation of the interior of inner electrode 38 and of the corona discharge zone 40 during operation. The corona field in the vicinity of the inner electrode 38 appears as a light violet glow. Defects in the electrode 38 appear dark violet and are visually apparent in contrast to properly operating areas that are lighter violet in color. A defective prior art generator in a plurality of arrays can not be identified without stopping operation, disassembly of every generator of the array, replacement of the defective electrode and reassembly of the entire array. The generators 30 permit immediate identification of a generator with a defective electrode. Only the generator with the defective electrode need be disassembled and replaced. Disassembly of the entire array is not necessary.

[0028] According to the process of the present invention, a flow of oxygen or oxygen enriched air is injected 58 into corona discharge zone 40 formed between concentric inner tubular electrode/dielectric 34, 38 and outer tubular electrode 32 wherein oxygen in the enriched air is converted to ozone. The process comprises injecting a feed stream of oxygen or oxygen enriched air by tubular gas injector 52 having an inlet end 56 to accept the oxygen or oxygen enriched air and outlet end 58 to inject the oxygen or oxygen enriched air within the inner concentric electrode/dielectric 34, 38. The injector 52 is characterized by jut 70, which provides electrical contact with inner electrode 34. The injected air flows within the inner concentric electrode/dielectric, 34, 38 to the corona discharge zone 40 for conversion of oxygen to ozone. The flow of oxygen or oxygen enriched air is injected by tubular gas injector 52 within the inner concentric electrode/dielectric 34, 38 in a proximity of a capped end 36 of dielectric 34 of the inner concentric electrode/dielectric 34, 38. The injected feed stream washes an inner surface (inside diameter) of the inner concentric electrode/dielectric 34, 38 to scavenge ozone from within the inner concentric electrode/dielectric 34, 38. The injected feed stream displaces heat by convection from the inner concentric electrode/dielectric 34, 38.

[0029] Referring to FIG. 6, shown is an overall ozone generator and treatment system and process. The first step in the process is air preparation. Ambient air 72 is drawn into a compressor 76 through an intake filter 74. A filtered air stream is sent to a storage/receiver tank 78, where initial moisture is removed as a condensate, which is discharged 82 from tank 78 at timed intervals. This initial separation of moisture extends sieve bed and other line filtration component life. Air in tank 78 is pressurized to 100 PSI in on and off cycles to extend compressor unit life.

[0030] Pressurized air from tank 78 is passed through a sub-micron filter (not shown) and sent to input regulator 80, where pressure is adjusted. The air is then sent to a control solenoid valve 84, which is electrically controlled by a timer to alternately charge the air stream to sieve bed 86 or sieve bed 88, and to alternately exhaust the bed 86 or 88. As one sieve bed is pressurized and provided with air stream, the complementary sieve bed is recharged. The molecular sieve beds 86, 88 absorb excess nitrogen from the feed air stream in a pressurized mode and release a product air stream, reduced in nitrogen (oxygen-enriched), in a decompression mode. This method of oxygen production is called Pressure Swing Absorption (PSA).

[0031] The oxygen-enriched air stream exits sieve beds 86, 88 via a shuttle valve 90. Pressure is regulated 92. Flow meter 94 precisely measures the air stream prior to passing the stream through the ozone-producing generator 30. In FIG. 6, generator 30 represents a single generator or a plurality of generators as depicted in FIG. 5. Each generator 30 is a corona discharge type shown in detail in FIGS. 3 and 4 and having a tubular outer cell 32 with an internal glass dielectric 34. The dielectric 34 has a conductive material applied to its inner surface to form inner electrode 38) connected to high voltage, high-frequency power supply 64 via the contact provided at 71 via the jut 70 on injector 52. The outer tube 32 acts as a ground. Between outer tube 32 and the dielectric 34 is an air gap (the corona discharge zone) 40. When power is applied to the assembly, a high-intensity corona is formed in the air gap 40. An oxygen-enriched feed gas stream passes through the air gap 40 and the intense corona (violet in color) converts a percentage of the oxygen to ozone. The air gap 40 and frequency of the power supply are adjusted for optimum corona density to produce maximum ozone output per square centimeter of electrode surface area.

[0032] Heat is a by-product of ozone production. Excess heat will convert ozone back to oxygen. The problem can be addressed by utilizing a closed-loop, liquid-cooled electrode chilling system 96. However, a chilling system may result in atmospheric ozone release. The structure of the ozone generator 30 of the present invention can provide a feed stream that sweeps an area of excess heat build up in the direction of diffusion of the stream so that the heat is convected through corona discharge zone 40 to discharge with product gas at output port 54.

[0033] FIG. 6 illustrates another advantage of the present invention. The configuration of generator 30 results in a net linear flow of feed gas from injector feed end 56 to ozone output port 54. The FIG. 2 prior art generator discharges product ozone gas from the generator end where feed gas is injected. The configuration of the FIG. 2 generator requires extensive fittings and extending conduits to transport product ozone gas to a treatment zone. In the configuration of FIG. 3 and FIG. 4, output port 54 is located at an end opposite feed end 56. Referring to FIG. 6, output port 54 can be directly connected via connector fitting 100 to the recycle circuit of a treatment zone 98, such as a bubble type diffuser, without requiring intervening structure A circuit includes bubble diffuser 102 and pumping system 104. In a bubble diffuser, the highly concentrated ozone product is applied to the bottom of a tall column to move counter current to flow of treated fluid. The direct connection to the recycle circuit via fitting 100 shown in FIG. 6, results in a configuration that decreases loss of ozone into the atmosphere that otherwise accompanies configurations such as shown in FIG. 2.

[0034] While preferred embodiments of the invention have been described, the present invention is capable of variation and modification and therefore should not be limited to the precise details of the Examples. The invention includes changes and alterations that fall within the purview of the following claims.