Numerical Simulation of Ammonia SCR-Catalytic Converters: Model Development and Application

A two-dimensional numerical model describing the ammonia based SCR-process on vanadia-titania catalysts is presented. The model is able to simulate coated and extruded monoliths. For the determination of the intrinsic kinetics of the various NH₃-NO_x reactions, unsteady microreactor experiments were used. In order to account for the influence of transport effects the kinetics were coupled with a fully transient two-phase 1D+1D monolith channel model. The model has been validated extensively with laboratory data and engine test bench measurements. After validation the model has been applied to calculate catalyst NO_x conversion maps, which were used to define catalyst sizes. Additional simulations were conducted studying the influence of cell density and NH₃-dosage ratio.