Ammonia Production from Solid Urea Using Non-Thermal Plasma

Among various NOx reduction technologies, selective catalytic reduction (SCR) methods have been studied for cleaning of diesel engine exhaust. Urea SCR system, in which ammonia is used as reducing agent is thought to be one of the most promising methods. However, further improvement of the performance is required at low temperatures for example below 400 K. The purpose of this study is to enhance ammonia generation from urea at low temperatures. In this study, a dielectric barrier discharge (DBD) plasma reactor in which dielectric pellets and urea powder were packed was investigated experimentally. The reactor was fed with humid gas and driven by pulsed high voltage at 400 K or lower. The effect of the pellet material, gas humidity, and gas flow rate on ammonia generation was experimentally examined. Application of discharge plasma enhanced the ammonia generation significantly at low temperatures in which ammonia generation was negligible without plasma. Material of the catalyst pellets packed in the reactor significantly affected the ammonia generation. Air plasma showed nearly the same ammonia generation as that of nitrogen plasma. These results suggest that our method can provide a compact and low temperature on-board ammonia production system.