Optimization of Ammonia Mixing in Selective Catalytic Reduction (SCR) Systems: A Computational Fluid Dynamics (CFD) Study on Swirl Angle and Mass Flow Rate Effects

The research deals with design a Heat Recovery Steam Generator (HRSG) model through Computational Fluid Dynamics (CFD) to evaluate Selective Catalytic Reduction (SCR) deNOₓ procedures that help maintain sustainable environmental emissions. We study six swirl angles ranging from θ = 10° to θ = 60° at the GT diffuser exit to determine how they affect ammonia (NH₃) mixing before the SCR catalyst bed. The evaluation process occurred under mass flow conditions of 350 kg/s and 700 kg/s. Ammonia mixing uniformity must comply with Industrial standards by keeping the RMS value of mole fraction distribution less than 5% according to manufacturer specifications. The results indicate that a swirl angle of 30° produces the best NH₃ mixing performance with RMS 4.27% and theta = 40° provides the best temperature distribution ranging within ±7.41°C. The research delivers vital information regarding SCR system optimization when operational parameters change.