A New After-treatment Concept of Diesel Exhaust Gas Using Barrier Discharge Reactor Combined with Diesel Particulate Filter

For diesel vehicles, NO_x aftertreatment systems have become increasingly important, since the emission legislations continuously tightened. However, particulate matters (PM) and NO_x aftertreatment systems have an impact on the engine operation and fuel penalties. Therefore, it is necessary either to find some auxiliary systems to decrease this impact or to find some brand new deNO_x aftertreatment systems. In the literature, most research works concerning NO_x and PM emission elimination using non-thermal plasma was conducted by employing either a dielectric barrier discharge (DBD) reactor alone or a plasma-assisted catalysis working under high temperature condition (over 150°C). Although there have been evidences that non-thermal plasma decomposes diesel PM but its mechanism is still not clear.

In this paper, the simplified model for laboratory experiments consists of a wire-to-cylinder DBD reactor combined with a DPF was used to investigate NO_x removal characteristics. The DPF putting in the discharge field has two functions: a PM filter and a dielectric barrier. A simulation gas of N₂, NO and O₂ combined with PM was used as the test gas. The results showed that PM promoted NO_x removal reactions in the barrier discharge field but its effect was dropped following elapsed time. Through this study, two new definitions of "Fresh PM" and "Aged PM" are used to explain the significant effect of PM on NO_x removal process. Besides, the chemical reaction mechanism inside reactor was discussed. From the obtained results, a novel catalyst concept for diesel exhaust aftertreatment is suggested.