The Use of Computational Fluid Dynamics (CFD) in Selective Catalytic Reduction System Ductwork Design

Abstract

Abstract A selective catalytic reduction (SCR) system serving a mixture of two different exhaust gas streams is considered. The exhaust gases are petroleum combustion residues and contain high levels of toxic nitrogen oxides (NOx). The SCR system is used to minimize the hazardous content of the two exhaust streams to meet U.S. national standards. The SCR system injects ammonia into a mixture of the two NOx-laden exhaust streams, which then pass through a catalyst, where a chemical reaction reduces the NOx to harmless water and nitrogen. The system operates most efficiently within specified gas temperature and velocity ranges. This paper discusses the use of computational fluid dynamics (CFD) to design a ductwork geometry upstream of the SCR system that results in optimum performance. Various geometries are considered based upon physical space restrictions and operating conditions. The improved duct system results in the desired temperature and velocity ranges at the catalyst face while keeping the total application pressure drop below a preset value.