Pollutant emission characteristics of the close-coupled selective catalytic reduction system for diesel engines under low exhaust temperature conditions

Abstract

The selective catalyst reduction system is an effective method for reducing pollutant emissions from diesel engines. To meet the increasingly strict requirements of pollutant emission regulations and further reduce the pollutant emissions of heavy diesel engines at low exhaust gas temperatures, a close-coupled selective catalyst reduction (ccSCR) system based on a corrugated substrate was proposed. Based on the corrugated substrate with V2O5-WO3/TiO2 catalysts, the pollutant emission characteristics of the ccSCR system were compared with those of a conventional selective catalyst reduction (SCR) system under the World Harmonized Transient Cycle at the exhaust gas temperature of 165 °C. Additionally, the effects of the volume ratio of ammonia to nitrogen (α) and the catalyst volume to engine gas capacity ratio (γ) on pollutant emissions of the ccSCR system were investigated. Results showed that pollutant emissions exhausted from the ccSCR system were significantly lower than those from the conventional SCR system. With the increase of α from 0.3 to 0.7 and γ from 0.33 to 0.76 in the ccSCR module, the NOx emission and NH3 slip of the ccSCR system decreased, and α had a larger effect on reducing pollutant emissions from the ccSCR system. The minimum values of NOx emission and NH3 slip were 0.22 g/kW·h and 2.33 ppm, respectively, at α = 0.7 and γ = 0.76 of the ccSCR module. The proposed ccSCR system was conducive to reducing the pollutant emission of diesel engines and its pollutant emission characteristics outperformed the conventional SCR system.