Paper PS1-TuM12
High Density Narrow Tube Ozonizer by Increased Barrier Discharge Frequency

Tuesday, October 29, 2013, 11:40 am, Room 102 B

Atmospheric plasmas are being general tool for various surface treatment applications, such as cleaning, sterilization, hydrophilic property control, etc. Among these applications, oxygen related radicals are the key species to influence the surface chemistry of the target. For the transport of the radical, spraying plasma processed gases to the object is commonly applied among these uses. There are certain reasons to develop high density atmospheric plasma source which is compact and able to be introduced or “ retrofit ” to the current chemical processing systems. In the current study, we are developing the high frequency atmospheric ozonizer plasma source in general 1/4 inch O.D. tube which gives high density ozone.

High frequency barrier discharge at 280 kHz consists of the alumina tube, the cupper grounded electrode, and the aluminum drive electrode. ( shown in fig . 1) The aim of MF range of frequency is to shift power deposition target to electrons from ions, and to increase the barrier discharge frequency. High voltage for the barrier discharge (0.5 mm gap) is produced by the LC resonance circuit (fig . 2).

Comparison of ozone density between 50 Hz (0.8 g /Nm³, 40 kVpp ) and 280 kHz (30 g/Nm³, 6.5 kVpp ) shows the production rate is increased 40 times for realistic voltage range (fig . 3).

V-I characteristic of 280 kHz (fig . 4) shows the discharge current and power is increased steeply around 6 kVpp that corresponds to the rapid increase of ozone production rate.

The increase of power with voltage is explained by the change of waveform (fig . 5). Small change of the voltage leads to the forwarding of the current phase and increase of barrier discharge frequency.

The power efficiency of the ozonizer is 19 g /kWh which is comparable to the commercial small scale unit.