Study on evaporation and decomposition process of urea water solution in selective catalytic reduction system

Abstract

Urea selective catalytic reduction (Urea-SCR) system is a promising technology for reducing nitrogen oxides (NOx) emissions from diesel engines. The evaporation and decomposition process of urea water solution (UWS) has been a concerned issue since it is more and more widely used in SCR systems as reductant to generate ammonia. UWS droplets may not evaporate and decompose completely when reaching the reactor, leading to a lack of ammonia in SCR reactions. Besides, the deposits generated during UWS decomposition may block the flow and degrade the efficiency of SCR system, when combined with the undecomposed solid urea. This research aims to investigate the evaporation and decomposition process of UWS droplets. A numerical model of UWS droplet evaporation and decomposition process was established and implemented by an in-house developed MATLAB simulation code. The model developed is able to predict the evaporation and decomposition process of UWS droplets.