The Plasma Flame: Development and Application of a Hybrid Plasma at Atmospheric Pressure

Abstract

The focus of this work was to develop a hybrid plasma at atmospheric pressure, which we have deemed the “plasma flame†. This discharge is capable of facilitating the chemical reactivity associated with non-thermal (low energy) plasmas while operating at temperatures which can drive high energy reactions. Gas mixtures of nitrogen and oxygen were used as a model system for understanding the nature of the plasma flame. Multiple process variables and discharge characteristics were studied gas composition, applied power, driving frequency, electron density, gas temperature, plasma temperature, radical chemistry, and reaction kinetics. It was found that this discharge produces a significant amount of nitrogen dioxide (NO2) over 10^17 cm-3. The production of NO2 was found to depend predominately on the temperature differential between the plasma and ambient gas. The extent to which the NO2-forming reactions proceed also depends on the availability of atomic oxygen (O) and nitric oxide (NO). Given the level of NO2 formation in the plasma flame, a process was created for synthesizing nitric acid (HNO3) we call “Acid on Demand†. This process was then developed for application to the production of bioethanol and printed circuit boards (PCB’s). Furthermore, the formation of syngas (CO + H2) was also produced by introducing a different chemical system into the plasma flame (i.e. CH4 + H2O).

This thesis establishes a framework for understanding the complex chemistries associated with the plasma flame. Such knowledge can be extended to a number of chemical systems and potential applications. Overarching themes of this work have implications for a variety of topics, from non-equilibrium chemistry to synthesis of alternative fuels.