Observation of discharges in NOx treatment reactor using nanosecond pulsed powers and the reactor improvement

The NOx treatment using streamer discharges generated by nanosecond pulsed powers was studied. The streamer discharges were produced in the treatment reactor by adopting nanosecond pulsed powers. In the previous study, temporal decrease in NO removal ratio was observed as pulse repetition rate increased. This was because the inner wire electrode of coaxial treatment reactor curved during pulse application and spark discharges occurred between the electrodes. A tensioned inner wire electrode was introduced in the coaxial reactor by using a spring system. As a result, the temporal decrease in removal ratio was not observed and the removal ratio was righted. To utilize denser streamer discharges near the inner wire electrode, the diameter of external cylindrical electrode was made smaller. The thinning of reactor improved the NO removal ratio with the tensioned inner wire electrode. When the initial NO concentration was 100 ppm, the removal ratio reached up to approximately 100 %. However, the NO removal ratio decreased when the inner diameter of the external cylindrical electrode was decreased from 14 mm to 10 mm. This might be because spark discharges would occur in the reactor by excessively shortened electrode separation. In addition, the energy deposited in reactor might decrease with decrease of reactor volume.