Destruction of hydrocarbons in non-thermal, ambient-pressure, capillary discharge plasmas

Abstract This present work investigates the effectiveness of non-thermal diffuse plasmas for the destruction of environmental contaminants that are present in trace concentrations in respirable atmospheres. Parametric studies were carried out using three atmospheric-pressure capillary plasma reactors of varying geometry. Volatile aliphatic and aromatic hydrocarbons, at concentrations of up to several hundred parts per million (ppm), were used as prototypical compounds for these studies. Parameters studied included the reactor volume, the species residence time, the specific energy input, and the influent contaminant concentration. Moreover, the dependence of the overall destruction efficiency on specific energy, contaminant type, and presence of other contaminants in well-defined contaminant mixtures was evaluated. By-product formation during the plasma chemical destruction was assessed by monitoring the concentration of gaseous nitrogen and carbon oxides, namely, NO x (NO, NO 2 ) and CO x (CO, CO 2 ). Carbon mass balances were used to assess the possibility of complete contaminant destruction leading to mineralization. Systematic trends are highlighted and show that the destruction efficiency increases with specific energy, but tends to level off at values of specific energy that are compound dependent. An inverse relationship between the maximum destruction efficiency of a particular compound and its ionization energy was found for chemically similar compounds.

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