Influence of Streamer-to-Glow Transition in NOx Removal Using Pulsed Power Generator with SOS Diodes

Abstract

Summary form only given. We carried out NOx removal test using co-axial non-thermal plasma reactor driven by inductive energy storage system pulsed power generator with focusing influence of primary capacitor capacitance on NOx removal. Semiconductor opening switch (SOS) diodes are employed as opening switch. A primary capacitor is charged up negatively to the voltage using a dc high voltage power supply. The charges are released from the capacitor by switching-on a gap switch mechanically, as the results, the current flow to the LC circuit through the SOS diode as forward-pumping current. After the current direction reverses with LC oscillation, the reverse current is injected into the SOS. With the current interrupted by the SOS, tire high voltage pulse is applied to the high voltage electrode as a short nanosecond pulse. This nanosecond pulse produces the streamer discharges homogeneously. A co-axial cylinder plasma reactor, which consists of 1 mm diameter tungsten wire and 19 mm i.d. copper tube with 30 cm in length, is employed as the nonthermal plasma reactor. The gas mixture of 200 ppm NO diluted with N2:O2=9:1 is used as a simulated diesel engine exhaust gas. The gas flow rate is 2 l/min. The energy efficiencies of NO removal are around 16 g/kWh at 50 % removal when the capacitance is in range from 100 to 500 pF. However, the energy efficiency decreases to 3.5 g/kWh with increasing capacitance of the primary capacitor from 500 pF to 4.2 nF. This efficiency decrease is caused by glow discharge generation.