Plasma Assisted De-NOx In Diesel Engine

Plasma assisted De-NOx systems in mobile application are introduced. In general, de-NOx process requires reductant for reducing catalyst. NH3(Urea) fueling, post injection of diesel fuel are representative of method for supplying reductant. Here, using synthesis gas by on board reforming as reductant can remove inconvenience of periodic reductant fueling, requirement for infra structure for reductant station. Also on board reforming can improve relative low de-NOx rate of post injection based de-NOx system for hydrogen in reformate gas works as superior reductant.

In this presentation, plasma assisted HC-SCR and plasma assisted LNT system is introduced. Developed plasma on-board reformer has small volume of about 50cc and use only about 100W of electric power for passenger car application. However, when applied in HC-SCR system, this small reformer can elevate de-NOx rate even up to 50% in some cases that is proven in engine bench test. Moreover, the result is obtained in reduced volume of reducing catalyst or less than half of typical SCR catalyst volume. (Considering typical HC-SCR catalyst requires volume of about 2~3 time of engine volume)

In the case of LNT system, requirement for fuel rich condition of engine during reducing mode, periodic high temperature operation for de-SOx result in rather high fuel penalty and this has been the bottleneck of LNT application. However, in plasma assisted dual leg LNT system, LNT operation is independent of engine condition or rich condition for reducing mode is not required. Also, de-SOx operation is independent with engine operation and high efficiency de-SOx is possible by using plasma reformer as plasma burner.

All of these benefits of plasma assisted de-NOx system are verified in engine bench test. Field tests are also in preparation and application of the system is prospective in near future