Influence of the On-time on the Ozone Production in Pulsed Dielectric Barrier Discharges

Abstract

Understanding the production mechanisms of ozone and other reactive species in atmospheric pressure dielectric barrier discharges (DBDs) has become increasingly important for the optimization and commercial success of these plasma devices in emerging applications, such as plasma medicine, plasma agriculture, and plasma catalysis. In many of these applications, input power modulation is exploited as a means to maintain a low gas temperature. Although the chemical pathways leading to ozone production/destruction and their strong temperature dependence are relatively well understood, the effect of the on-time duration on the performance of these modulated DBDs remains largely unexplored. In this study, we use electrical and optical diagnostics, as well as computational methods, to assess the performance of a modulated DBD device. The well-established Lissajous method for measuring the power delivered to the discharge is not suitable for modulated DBDs because the transients generated at the beginning of each pulse become increasingly important in short on-time modulated plasmas. It is shown that for the same input power and modulation duty-cycle, shorter on-time pulses result in significantly enhanced ozone production, despite their operation at slightly higher temperatures. The key underpinning mechanism that causes this counter-intuitive observation is the more efficient net generation rate of ozone during the plasma on-time due to the lower accumulation of NO2 in the discharge volume.

Removal of Mixed Volatile Organic Compounds of Benzene, Toluene, and Xylene in a Multistage Corona Discharge System under Excess Air

“…Hence, the formation of NO x in the studied plasma system can be ruled out. The formation of ozone (O 3 ), generated from the combination of three atoms of oxygen, was found in trace amounts since most of the generated ROS immediately reacted with VOCs and lower-molecular-weight (MW) HCs derived from the VOCs. , There was a higher probability of a direct collision between the highly energetic electrons and VOCs, by cracking at various molecular positions of VOCs, leading to their dehydrogenation reactions to yield lower-MW HCs, as shown in eqs – …”

“…Hence, the formation of NO x in the studied plasma system can be ruled out. The formation of ozone (O 3 ), generated from the combination of three atoms of oxygen, was found in trace amounts since most of the generated ROS immediately reacted with VOCs and lower-molecular-weight (MW) HCs derived from the VOCs. , There was a higher probability of a direct collision between the highly energetic electrons and VOCs, by cracking at various molecular positions of VOCs, leading to their dehydrogenation reactions to yield lower-MW HCs, as shown in eqs – C 6 H 6 + e − → C 6 H 5 • + H • + e − C 6 H 5 ( CH 3 ) + e − → C 6 H 5 ( CH 2 • ) + H • + e − C 6 H 5 false( CH 3 false) 2 + e − → ( CH 3 ) C 6 H 5 ( CH 2 • ) + H • + e −...…”

Development of a rapid plasma decontamination system for decontamination and reuse of filtering facepiece respirators

“…The optimal emission intensity of the second positive nitrogen is used as a proxy for the overall discharge intensity of the source DBD plasma generator. 17 The emission peaks of the hydroxyl radicals (OH) at wavelengths 306–312 nm and of nitric oxide (NO) at wavelengths below 300 nm are characterized by lower intensity. The first negative system of nitrogen from 390 to 440 nm is also detected.…”

The 2022 Plasma Roadmap: low temperature plasma science and technology

“…Increasing the efficiency of ozone generation in both smalland large-scale plasma reactors has been an ongoing research effort. Both models and experiments have been used to optimize the operation of dielectric barrier discharge (DBD) reactors for ozone production including the electrode geometry, dielectric properties, operating pressure, gas temperature, and power modulation [157,158]. Ozone production efficiency is also strongly dependent on the purity of the starting O 2 .…”