Corona generator method and apparatus

• US 3,954,586 A
• Filed: 07/16/1973
• Issued: 05/04/1976
• Est. Priority Date: 01/04/1967
• Status: Expired due to Term

• Current Assignee: Atlantic Richfield Company Incorporated (BP PLC)
• Original Assignee: Purification Sciences Incorporated
• Inventors: Lowther, Frank E.
• Primary Examiner(s): Edmundson, F. C.
• Application Number:
  US05/379,846
• Time in Patent Office: 1,023 Days
• Field of Search: 204/170, 204/171, 204/176, 250/531-541
• US Class Current: 204/176
• CPC Class Codes: B01J 2219/0849 Corona pulse discharge
• CPC Class Codes: C01B 13/11 by electric discharge
• CPC Class Codes: C01B 2201/12 Plate-type dischargers
• CPC Class Codes: C01B 2201/34 Composition of the dielectrics
• CPC Class Codes: H01T 19/00 Devices providing for corona discharge for charging electrographic elements G03G15/02
• CPC Class Codes: Y10S 422/907 Corona or glow discharge means

Abstract

A corona generator method and apparatus preferably for generating ozone, employing a plurality of corona generating cells each comprising a pair of parallel speced-apart electrodes having a fired-on coating of porcelain enamel. The electrodes are connected to an AC voltage source of sufficient voltage to generate a corona discharge, and an oxygen-containing gas is passed between the electrodes to generate ozone. A high concentration ozone is produced as well as a large quantity of ozone, without water cooling, and at voltages of approximately 6,000 volts. An equation setting forth, for the first time, the interrelationships between the various parameters in a corona generator is derived by Applicant. According to the invention, the corona power is maximized by maximizing the expression ε/Td, where epsilon is the dielectric constant of the porcelain enamel coating and Td is the dielectric thickness.

Claims

1. The method for generating a corona discharge comprising:

providing a pair of parallel, adjacent, spaced-apart electrodes defining a corona discharge chamber between a facing internal surface of each electrode;

providing at least one of said internal surfaces with a fired-on coating of porcelain enamel dielectric material;

providng a total dielectric thickness for said at least one coating of less than 40 mils;

applying an A.C. voltage having a frequency of between about 60 Hz and 40 KHz and a voltage of between the corona start voltage and 15,000 volts, across said pair of electrodes to generate a corona discharge;

spacing said electrodes apart a distance of between about 5 and 100 mils; and

feeding a reactant into said corona discharge chamber to be acted upon by said corona discharge.

2. The method according to claim 1, wherin said coating providing step comprises providing a fired-on porcelain enamel dielectric coating on each of said electrodes.

3. The method according to claim 2, including the steps of providing said coatings by separately firing a plurality of individual porcelain enamel layers onto said electrodes to form each of said coatings.

4. The method according to claim 3 wherein said steps of separately firing-on individual porcelain enamel layers includes firing each of said plurality of layers at a temperature of about 1480°

F.

5. The method according to claim 1, including cooling said electrodes by feeding ambient air past and in contact with external surfaces of each of said electrodes.

6. The method according to claim 1, including the step of eliminating all voids from said porcelain enamel dielectric material.

7. The method according to claim 1 including the step of spacing said electrodes apart the optimum air gap distance Ta in accordance with the formula:

##EQU9## wherein P/A -- corona power in watts per square inch of dielectric area

ε

-- relative dielectric constant of coating

Td -- dielectric thickness in mils

Vo -- applied volts

Vs -- sparking voltage in air measured in volts per mil

Ta -- air gap between electrodes in mils

8. The method according to claim 7 including employing a total dielectric thickness Td in mils and a dielectric constant ε

such that the value ε

/Td is greater than 0.10.

9. A method for generating ozone in an ozone generator including a pair of adjacent, parallel, spaced-apart electrodes defining a corona generating chamber therebetween comprising:

providing a fired-on coating of porcelain enamel dielectric coating on the internal facing surface of at least one of said electrodes,

employing a total dielectric thickness Td in mils and a dielectric constant ε

such that the value ε

/Td is greater than 0.10,

feeding an oxygen-containing gas into said chamber,

applying an A.C. voltage of between the corona start voltage and 15,000 volts and of between 40 Hz and 60 KHz across said electrodes, and,

feeding ozone from said chamber.

10. The method according to claim 9 wherein said providing step comprises coating the facing internal surface of each of said electrodes with a plurality of separate, individually fired-on porcelain enamel layers.

11. The method according to claim 10 wherein said providing step further comprises removing substantially all voids from said porcelain enamel.

12. The method according to claim 11, including cooling said electrodes by feeding ambient air past the external surfaces of each of said electrodes.

13. A method for producing ozone from an oxygen-containing gas passed through a corona generator employing a pair of parallel, spaced-apart electrodes defining an air gap of uniform width therebetween, and a fired-on coating of porcelain enamel dielectric material on at least one of said electrodes, comprising positioning said electrodes a predetermined distance apart to provide an air gap Ta therebetween, such that the following equation is satisfied ##EQU10## where Ta -- air gap length in mils

Vo -- applied peak voltage in volts

Td -- dielectric thickness in mils

ε

-- dielectric constant

14. In the method of generating ozone in an air gap between a pair of spaced-apart electrodes between which electrodes is positioned a fired-on coating of porcelain enamel dielectric on at least one of said electrodes and having a total thickness of less than 40 mils, the improvement comprising determining the optimum air gap length and maintaining the air gap length within 10 mils of the optimum air gap length.