Toluene decomposition in humid gas by using surface discharges on dielectric subjected to repetitive voltage pulses with polarity reversal

This paper presents an experimental study on toluene gas decomposition using repetitive surface discharges on a dielectric barrier subjected to very fast polarity-reversed pulse voltage or standard ac (sinusoidal or square) voltages. 300 ppm of toluene with dry air or with humid air is injected into a plasma reactor with a double cylindrical glass tubes. Effect of the very fast polarity reversal on toluene decomposition in humid air is studied. The surface discharge inception voltage for the polarity-reversed pulse is lower than that for both sinusoidal and square ac. Intense surface discharge light spread on the glass barrier when the voltage polarity is rapidly changed from negative to positive. Therefore, the toluene decomposition ratio for the polarity-reversed pulse is higher than those for the standard ac voltages. Under a dry air condition, no remarkable differences of the energy efficiency for toluene decomposition are observed between the applied voltages. However, the energy efficiency for the sinusoidal ac becomes lower than those for the other voltages under a humid air condition. The energy loss due to Joule heating is produced by the conduction current along the wet surface during the voltage polarity is changing. Therefore, the energy efficiency under the humid condition depends on the rise time of the polarity reversal of the applied voltage.