Pulsed Corona Plasma Technology for the Removal of NOx from Diesel Exhaust

Increasing environmental awareness and regulatory pressure have motivated investigations into energy efficient methods to remove oxides of nitrogen (NO_x) from diesel exhaust. Past emission requirements have been achieved by modifying the engine combustion parameters. However, engine modifications alone are not sufficient to meet the proposed 2004 EPA regulations for heavy duty diesel powered trucks. Some form of post combustion control is necessary. Conventional catalyst technologies, such as three-way automotive catalysts are ineffective under high oxygen levels. The use of non-thermal plasmas offers the potential to selectively reduce NOx in such high oxygen exhausts without the need for supplemental scavengers or additives. Plasmas produce energetic electrons which collide with the background gas molecules leading to the formation of a variety of new species including ions, metastable species, atoms and free radicals. These are all chemically reactive, providing a pathway for the removal of the pollutants. The present paper focuses on recent advances and developments of pulsed corona system being developed for heavy-duty diesel engines.