Diesel engine exhaust treatment with a pulsed streamer corona reactor equipped with reticulated vitreous carbon electrodes

Reticulated vitreous carbon (RVC) has been shown to be useful for high-voltage and ground electrodes in gas-phase pulsed streamer corona reactors. RVC disks with large macroscopic porosity are placed perpendicular to the gas flow and the main axis of a cylindrical corona reactor. This electrode geometry produces streamers that propagate in the direction of the gas flow and are uniformly distributed in the cross section of the reactor. This highly electrically conductive material has large macroscopic porosity, thus allowing for gas flow through the electrodes with low pressure drop. Previous work has considered the effects of RVC electrodes on NO/NO_x removal from various test gases containing air, water vapor, and ethylene. The present studies show removal of NO/NO_x from the exhaust of a 5 kW diesel engine. Under cold reactor operating conditions (12°C) 81% NO and 53% NO_x could be removed at an energy yield of 4.8 g/kWh (based on NO). Furthermore, experiments with the combination of TiO₂ or γ-Al₂O₃ catalyst particles placed in the region between the high-voltage and ground electrode disks gave NO removal at energy yields of 29 g/kWh and 9 g/kWh, respectively, at about 100°C, and significant fractions of the nitrogen were recovered as NO₃^- deposited on the catalyst surface. The RVC electrode system without catalysts was found to lead to efficient ozone production (55-70 g/kWh) in dry air at room temperature