Experimental study of ammonia storage characteristics of selective catalytic reduction for diesel engine based on Cu-based catalysts

Abstract

In this paper, the ammonia storage characteristics of Cu-based zeolite catalysts at different exhaust temperatures in heavy-duty diesel engines were experimentally investigated. The data such as exhaust temperature, rotational speed, torque, urea consumption, NOx concentration at selective catalytic reduction (SCR) inlet and outlet, ammonia storage, and NH3 leakage of the diesel engine were recorded respectively. The trend of ammonia storage characteristics of the SCR system was analyzed using the urea injection stopping time as the cut-off point. Both the SCR catalyst ammonia storage volume and the time to saturation of ammonia storage volume decreased with the increase in exhaust temperature. The maximum value of ammonia storage was 9.58 g at 193 °C and 1.08 g at 376 °C. The saturation time decreased from 466.4 s to 96.8 s. The increase in catalyst activity at high temperatures increased the rate of denitrification reaction, but it was observed that the ammonia slippage occurred earlier from 450 s to 100 s, which was mainly due to a more active ammonia desorption reaction at high temperatures. The larger ammonia storage at low temperatures made the effect on NOx conversion efficiency more significant, and the effect of exhaust temperature gradually increased when the temperature was further increased.