Numerical analysis of NOxreduction for compact design in marine urea-SCR system

Abstract

In order to design a compact urea selective catalytic reduction system, numerical simulation was con-ducted by computational fluid dynamics tool. A swirl type static mixer and a mixing chamber were considered as mixing units in the system. It had great influence on flow characteristics and urea decomposition into ammonia. The mixer caused flow recirculation and high level of turbulence intensity, and the chamber increased residence time of urea-water-solution injected. Because of those effects, reaction rates of urea decomposition were enhanced in the region. When those mixing units were combined, it showed the maximum because the recirculation zone was significantly developed. NH3conversion was maximized in the zone due to widely distributed turbulence intensity and high value of uniformity index. It caused improvement of NOxreduction efficiency of the system. It was possible to reduce 55% length of the chamber and connecting pipe without decrease of NOxreduction efficiency.