Ozone production of low-frequency plasma using high-impedance high-voltage transformers for volume plasma generation for plasma-based air purification

Plasma-based air purification was demonstrated to inactivate a range of pathogens, including viruses, bacteria and fungi, while also breaking down pollutants and odors. Plasma-based air purifiers can be used to clean industrial exhaust air, kitchens, food manufacturing facilities and in animal housing. One of the active mechanisms is attributable to the ozone produced by the plasma from atmospheric oxygen and subsequent ozone chemistry. Accordingly, a high ozone production rate is essential for an efficient process. In this study, the production rates of ozone were measured in a 3 m3 stainless steel chamber of a plasma-based air purifier. The plasma electrode is composed of two electrode stacks, each with 68 glass tubes (two rows of 34 tubes) and a gas gap of 2 mm. These stacks are alternately contacted with the two poles of a high-voltage (HV) transformer in a checkerboard pattern. When an alternating HV is applied, a volume plasma is generated between the glass tubes. The frequency and duty cycle (D), which is the control ratio of the transformer, was changed separately via the power electronics. The maximum electrical power consumption was achieved at the resonance frequency of 75 Hz with the D by 50%. The electrical power consumption decreased at higher and lower frequencies as well as by reducing the D. The results show that the ozone production rate increases with electrical power consumption and excitation frequency when the electrical power consumption is maintained at a constant level.