Investigation of spark dischare control in coaxial reactors to produce dense ozone using nanosecond pulsed powers

Summary form only given. Ozone has a strong oxidizability, but its environmental load is low because it is composed of three oxygen atoms. Therefore, field of use and consumption of ozone have been expanded recently. Nonthermal plasma as streamer discharges is efficient for producing ozone. Dielectric barrier discharges has been used to produce ozone in industrial ozonizers because the nonthermal plasma is obtained with facility, but the efficiency of ozone production is not sufficient. On the other hands, ozone productions using pulsed power are highly-efficient but produced ozone concentrations are not high. Improvement of the ozone concentration will put production using pulsed power to practical use. Then, we have applied nanosecond pulsed power to a production of dense ozone. Ozone concentration and efficiency of production increased with decreasing diameter of a coaxial reactor in our previous studies using nanosecond pulsed power. However, in using a coaxial reactor having a smaller diameter, spark discharges occurred in the reactor; therefore, the ozone concentration reduced. The conditions triggering the spark discharges depended on not only the diameter of reactor but also pulse repetition rate. In this study, we considered the phenomena of the spark disc harges in the reactor and control of the spark discharges to achieve high ozone concentration. The effects of temperatures of gas and the electrodes on the occurrence of spark discharges and dissociation of ozone in the reactor were discussed. Although nanosecond voltage pulses were used, the pulse applied on the reactor was extended because of reflections of pulses and redundant energy was not deposited in streamer discharges. The extension of pulse width was one of causes of the spark discharges, so we reconsidered application and optimizing configurations of parallel coaxial reactors. Parallel connecting reactors might suppress the spark discharges and raised the ozone concentration.