Experimental and mechanism research on the NOx removal by a novel liquid electrode dielectric barrier discharge reactor

Abstract

Metal electrode corrosion and poor discharge uniformity are the key factors that restrict the discharge lifetime and de-NOx efficiency of a dielectric barrier discharge (DBD) reactor. In order to solve this problem, a novel DBD reactor with homothermic sodium chloride (NaCl) solution as grounded electrode was designed in this paper. The effects of NaCl solution conductivity on the electrical parameters, the de-NOx performance and the optical emission spectrum characteristics of DBD were studied experimentally. The pathways and mechanism of de-NOx in the whole discharge phase were revealed by numerical simulation, electron impact mechanism and chemical reactions sensitivity analysis. The results showed that the best discharge intensity, uniformity, energy consumption and de-NOx performance were achieved at 32mS/cm of NaCl solution conductivity. The removal efficiency of NO, NO2 and NOx reached close to 100%, 97.4% and 83.9% respectively. The numerical simulation showed that the de-NOx process of DBD could be divided into 3 phases, including the rapid removal phase of NO (0–0.05 s), the removal phase of NO and NO2 (0.05–0.7 s), and the stabilization phase of NOx (0.7–1 s). In terms of de-NOx mechanism, the active particles of N atoms, N(2D) atoms and O atoms dissociated from exhaust gas played key roles in the de-NOx process. The N atoms mainly reduced NO to pure N2, and the selectivity of N2 could reach up to 13.6%. The N(2D) atoms were the only radicals that formed extra NO. The O atoms contributed greatly with NO2 re-conversion to NO. This work is of great significance to promote the removal of NOx from ship exhaust gas by the DBD with liquid electrode.