Experimental Research on Distribution Characteristics of NOx Conversion Efficiency of a Diesel Engine SCR Catalyst

An experimental investigation of the distribution characteristics of NO x 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 x conversion efficiency were obtained by the interpolation of measured data. The experimental result showed that the distribution of NO x 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.