Development and analysis of High-Energy Corona process for air purification

This paper gives an overview of the High-Energy Corona (HEC) technology being developed for treating air and other gas streams, summarizes results of an initial field test of the HEC process and follow-up laboratory experiments, and outlines the progress and approach toward better understanding of the underlying physical and chemical mechanisms to guide further development. The High-Energy Corona process uses high-voltage ac fields developed in a packed bed of dielectric pellets to form a nonequilibrium plasma in the void spaces between the pellets. The pellets refract the electric fields, creating extremely high field strengths capable of initiating electron-impact ionization of the air (and contaminants). The present-generation HEC device is a coaxial cylinder with an inner metal electrode, an outer tube made of glass, and dielectric pellets filling the annular gap. A metal foil or screen in contact with the outside surface of the tube serves as the ground electrode. The inner electrode is connected to a high-volume (25 to 30 kV) ac power supply operated at a fixed frequency of 60 Hz. The glass tube serves as the reaction vessel and as a dielectric barrier to inhibit direct charge transfer between electrodes. The gas to be treated is simply pulledmore » through the packed bed where reactant species are produced and subsequent chemical reactions occur. Thus, far, the HEC process has been effective in destroying trichloroethylene, perchloroethylene, carbon tetrachloride, benzene, and heptane in the gas phase and naphthalene in the liquid phase. Further tests are planned with other compounds.« less