Comparative analysis of mixer designs for optimized NOx reduction and accretion control in SCR systems

• Swirl mixer demonstrated the most significant reduction in accretion rate out of the mixer designs explored. • Flap mixer exhibited higher accretion & deposition levels, improved NH₃ distribution. • Combined Swirl and Flap configuration improved mixing, increased deposition rate at higher injection rates. • Hybrid mixer exhibited improved NH₃ mixing and distribution, but high deposition rate. • Optimized mixer configurations particularly Swirl mixer, can significantly enhance SCR performance, provides more effective urea distribution and reduced deposit build-up to achieve efficient NOx conversion. This study explores the optimizing a Selective Catalytic Reduction (SCR) system aimed to reducing nitrogen oxide (NOx) emissions in diesel engines. Using computational fluid dynamics (CFD) simulations, both a base SCR design and an enhanced design were evaluated. The enhanced design, incorporating multiple mixer configurations, demonstrated notable performance improvements over the base design, including higher NOx reduction efficiency and lower accretion rates. The mixers in the optimized design enhanced ammonia (NH₃) distribution, leading to increased NOx conversion efficiency. In addition, the improved mixing dynamics in the proposed design contributed to a more uniform reagent distribution, essential for achieving consistent NOx reduction. This optimized system achieved significant reductions in Urea deposition and accretion, underscoring its superior performance, industrial applicability, and potential to meet stringent emission standards while minimizing operational challenges associated with Urea buildup. The proposed design achieved a 94.87 % reduction in accretion rate and a 10.8 % improvement in NH₃ mass fraction at the outlet. In terms of Urea deposit thickness, the base design exhibited a thickness of 10 µm, which contributed to system blockages and maintenance challenges. The enhanced design reduced this value to 5.1e- 4 µm, with further reduction to 4.7e- 4 µm upon integrating a swirl mixer, demonstrating improved ammonia distribution. The optimized mixer designs not only enhanced system efficiency but also ensured compliance with stringent emission standards, reduced crystallization risks, and improved long-term operational reliability.