Investigation of discharge appearance in reactor and removal ratio on NOx treatment using nanosecond pulsed powers

Abstract

Nitrogen oxides (NOx) is one of atmospheric pollutants. We have studied removal of NOx from simulated flue gases using nanosecond pulsed powers. Non-thermal discharge plasma, as streamer discharges by nanosecond pulsed power, is efficient for NOx removal. Coaxial reactors, which consist of a stainless wire as an inner electrode and a stainless pipe as an outer electrode, have been used to generate streamer discharges in the experiment. In the experiment using the coaxial reactor, after when application of voltage pulses started, removal ratio of NOx increased and reached to the peak value, and then it decreased immediately. In order to investigate cause of the decrease in NOx removal ratio, discharges inside the reactor were observed. Spark discharges occurred near center of the coaxial reactor and the inner wire electrode was gradually attracted to the outer electrode. A reactor having a tensioned inner wire electrode by a weight was introduced to consider this phenomenon. In the reactor, the inner wire electrode did not slant regardless of occurrence of spark discharge when some tension was given to the inner electrode. The streamer discharges were distributed evenly around the wire electrode and the removal ratio was upheld at arriving peak ratio.