Effects of C3H6, SO2, and Temperatures on the Nonthermal Plasma-Facilitated NH3–SCR Hybrid Reactor System to Reduce NOxfrom Diesel Engine Exhaust

An extensive series of experiments have been conducted to investigate the effects of C3H6, SO2, temperatures, and their combination on the comprehensive performance of the plasma-facilitated NH3–SCR hybrid reactor (PFSHR) system. The addition of C3H6drastically changes the pathway of NO oxidation in the process of dielectric barrier discharge (DBD), which can efficiently promote the oxidation of NO to NO2, making it easier to achieve the fast SCR reaction and thus significantly improve the NOxreduction at lower temperatures. In addition, the oxidation rate of NO to NO2is much higher than that of SO2to SO3due to the strong selective oxidation of DBD, which is one of the most important factors attributing to the robust resistance to SO2poisoning and the durability of the PFSHR system. Besides, SO2has some inhibiting effects on the activity of the PFSHR system at low temperatures below 250 °C, while the NOxremoval efficiency can be facilitated to a certain extent at medium to high temperatures. Moreover, the NOxabatement efficiency of the PFSHR system is remarkably influenced by the SIED below 250 °C, and the change of NOxreduction is relatively flat above 250 °C, which indicates that it is efficient for the DBD-assisted SCR to reduce NOxat low temperatures. Additionally, the efficiency of NO oxidation to NO2and the C3H6decomposition rate drops with the increase of the DBD reactor temperature, which, however, does not affect the NOxreduction at high temperatures. Furthermore, some regulated byproducts, N2O and CO, and unregulated byproducts, HCHO and CH3CHO, generated in the PFSHR system, from which HCHO and CH3CHO can efficiently participate in the SCR reactions and further enhance the NOxremoval efficiency, result in only a small amount of HCHO and CH3CHO residue at the outlet of the PFSHR system.