Experimental Research on Distribution Characteristics of NO Conversion Efficiency of a Diesel Engine SCR Catalyst

An experimental investigation of the distribution characteristics of NO conversion efficiency inside a selective catalytic reduction system is presented in this paper. Wash-coated and extruded vanadium-based selective catalytic reduction catalysts were investigated under an ANR (ammonia nitrogen ratio) of 1.0 and various exhaust gas temperature and flow rate conditions. A moveable sampling probe was located at various measuring points on the exit cross section of the selective catalytic reduction catalyst shell, and the final distribution maps of NO conversion efficiency were obtained by the interpolation of measured data. The experimental result showed that the distribution of NO conversion efficiency of the wash-coated selective catalytic reduction catalyst at the exit cross section was extremely nonuniform and the efficiency of the extruded SCR catalyst was uniform with a higher distribution at the center. A comparison experiment with 180° rotation of the selective catalytic reduction catalysts was implemented, and the efficiency distribution map of the wash-coated selective catalytic reduction catalyst also rotated 180° but that of the extruded selective catalytic reduction catalyst remained unchanged. The uniformity coefficient of the extruded selective catalytic reduction catalyst was higher than that of the wash-coated selective catalytic reduction catalyst used in this study.