Research On Removing Nitrogen Oxides From Diesel Exhaust By Dielectric Barrier Discharge Plasma

Dealing with nitrogen oxides (NO_x) as main components which cause acid rain and photochemical smog has become a major problem in the field of environment protection. The sources of NO_x are major from vehicle exhausts in China, therefore, controlling and processing diesel emissions have become an extremely urgent task nowadays. Non-thermal plasma technology based on dielectric barrier discharge (DBD) has the advantages of high removal efficiency and energy utilization, removing NO_x and other exhaust gases simultaneously, and no secondary pollutions. DBD has gradually attracted more attentions in exhaust treatment in recent years.This paper employed the NO_x from diesel exhausts as the investigated subject, designed the DBD plasma reactor and established simulated exhausts system based on plasma technology. In order to analyze the involved reactions between components of diesel exhausts and various factors that affect the NO_x conversion, Effects of the amplitude of the applied voltage, oxygen concentration and NO initial concentration on NO_x removal were studied. Obtained results indicate that, the NO removal rate increased with increasing the magnitude of the voltage; Oxygen concentration have a great influence on NO removal, the higher oxygen concentration is, the more NO is oxidized to NO2, and the lower NO removal rate is; the NO removal rate decreased with increasing NO initial concentration.In the DBD, the time that the electrons and radicals were generated didn't coincide with the time that chemical reactions were occurred after discharge; therefore, we divided the whole numerical simulation process into two parts: single micro-discharge calculation and chemical reaction calculation. Temporal of single filaments discharge was simulated by establishing fluid dynamics model in the DBD of coaxial cylinder electrode structure. We obtained two-dimensional profiles of electron concentration in a single micro-discharge by soluting with finite element analysis software; meanwhile, the chemical kinetic model was established by solving with matlab software, and the reaction mechanism that thermal plasma removed NO_x from diesel exhaust was probed. Finally, the experimental and simulation results were compared with.