The production of ozone was investigated using a dielectric barrier discharge in oxygen, and employing short-duration pulsed power. The dependence of the ozone concentration (parts per million, ppm) and ozone production yield (g(O3)lkWh) on the peak pulsed voltage (17.5 to 57.9 kV) and the pulse repetition rate (25 to 400 pulsesls, pps) was investigated. In the present study, the following parameters were kept constant: a pressure of 1.01~10~ Pa, a temperature of 26 k 4T, a gas flow rate of 3.0 llmin and a gaseous gap length of 11 mm. A concentric coaxial cylindrical reactor was used. A spiral copper wire (1 mm in diameter) was wound on a polyvinylchloride (PVC) cylindrical configuration (26 mm in diameter) and placed centrally in a concentric coaxial electrode system with 4 mm thick PVC dielectric layer adjacent to a copper outer electrode of 58 mm in internal diameter. HV and current pulses were provided by a magnetic pulse compressor power source.

Experimental investigation of HV short pulsed strcamcr discharges in dry air-fed ozonizers under various operating conditions arc reported. Ozone concentration, energy input and ozone production yield (efficiency) were measured at various voltagcs (14 to 37 kV), pulse repetition rates (25 to 400 pulses per second, pps), flow rales (1.5 to 3.0 llmin) and different gap spacings (10 to 20 mm) at a pressure of 1.01~10~ Pa in dry air. A spiral copper wire (1 m m in diamcler) madc to a cylindrical configuration (18 to 38 m m in diamcter) in a concentric coaxial clcckade system of various dimensions was employcd. A magnetic pulse comprcssor provided the H V and current pulses. Higher voltage and highcr repetition rates yielded higher concentrations of ozane at a fiwcd air flow rate. The present invcstigation was extended to assess the performance of this pulsed ozone generator using dry air under desired conditions of high concentration and high yield of ozone for industrial applications. ' Ucidcustia Corporation, 'lokyo, ]apau On Icavc from Universily of Windsor, Departnicnt of F.1cctrical and Cnnipiitcv h n ineering, Windsor, Ontario, Cauadn, hhnriscript was rcreived 011 11 Jrly 1999, in revisEd b m i a f

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Energy efficient generation of ozone is very important because ozone is being used increasingly in a wide range of industrial applications. Ozonizers usually use dielectric barrier discharges and employ alternating current (ac) with consequent heat generation, which necessitates cooling. In the present study, very short duration pulsed voltage is employed resulting in reduced heating of the gas and discharge reactor. A comparison of ozone generation in dry air using a coaxial concentric electrode system with and without a solid dielectric layer is reported. Two types of dielectric layers were employed, ceramic and polyvinylchloride (PVC). The effects of peak pulsed voltage (12.5 to 62 kV), reactor length (0.1 to 1 m), pulse repetition rate (25 to 400 pulses per second, pps), gas flow rate (1.5 to 3.0 llmin) and variation of the pitch length of the spiral wire forming the central electrode (5 to 10 mm) on the concentration and production yield of ozone (glkwh) are reported. A comparison is made between the performance of discharge reactors with (ceramic reactor Type IIC and PVC reactor Type IIP) and without (reactor Type I) a dielectric layer, using the same electrode gap separation (15 mm) and reactor lengths (0.157 and 1 m). High production yields of ozone in dry air of -122, 52 and 60 glkwh were obtained when using, respectively ceramic, PVC, and no dielectric layer, for a fixed pulse rate of 100 pps, 1.5 llmin flow rate and for a relatively short length of the reactor of 157 mm.

Very short duration pulsed streamer discharges have been used to produce ozone in a gas mixture of nitrogen and oxygen at atmospheric pressure. The ratio of nitrogen to oxygen in the mixture was varied in the range from 2.510.5 to 0.5/2.5, while maintaining a total flow rate of 3 lr'min. The production of ozone was found to be higher for a specific mixture ratio of N2/02 than that in oxygen or in dry air. The production of ozone in 0 2 was higher than that in dry air, The production yield of ozone (gkWh) increased with decreasing nitrogen in the 02/Nz mixture. It has been found that the peak of the streamer discharge current decreased with time after application of the pulsed power. This decrease in the current corresponded with the increase in the ozone production and is attributed to the loss of electrons in the discharge current due to their attachment to ozone to form negative ions.

Experimental investigations of high voltage short pulsed streamer discharges in dry air-fed ozonizer under various operating conditions are reported. Ozone concentration, energy input and ozone production yield were measured at various voltages (14 to 37 kv), pulse repetition rates (25 to 400 pulses per second, pps), fixed flow rates (1.5 to 3.0 vmin) and different gap spacings (10 to 20 mm) at a pressure of 1.01 x 10' Pa in dry air. A spiral wire made to a cylindrical configuration in concentric coaxial electrodes of varying dimensions was employed. A magnetic pulse compressor provided the voltage and current pulses. Higher voltage and higher repetition rates yielded higher concentrations of ozone at a fixed flow rate. Additionally the present investigations were extended to assess the performance of pulsed ozone generators using dry air under industrial conditions, where both the concentration of ozone (in parts per million, ppm) and its yield (in g/kWh) were maintained at high levels.

Ozone is increasingly being used as an altemative oxidant to chlorination processes in various industrial applications without any objectionable by products to the environment and requiring less energy for its production. Therefore, it is necessary to investigate the effects of various parameters on the production of ozone both experimentally and theoretically. A theoretical study focused on numerical simulation was performed to investigate the validity of the dependence of the ozone concentration on various parameters measured experimentally and to better understand the discharge phenomenon employing very short pulsed streamer discharges in the ozonizer at a room temperature and atmospheric pressure. The generation and decay of different particle species subjected to pulsed discharges were simulated as a function of time using both a single pulse and multiple pulses. The rate coefficients of various plasma chemical reactions including electron impact dissociation of the principal gaseous components, namely oxygen and nitrogen in dry air, occurring in the streamer corona discharge depending upon the electric field to particle density ratio (EN) and the gas temperature were taken into account. The trend showing the dependence of the concentration of ozone in dry air on the parameters studied generally agreed with the experimental results and with the published literature thus confuming the validity of the simulation model.

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