Modeling an Ammonia SCR DeNOx Catalyst: Model Development and Validation

A 1-D numerical model describing the ammonia selective catalytic reduction (SCR) de-NO_x process has been developed based on data measured on a laboratory microreactor for a vanadia-titania washcoated catalyst system. Kinetics for various NH₃-NO_x reactions were investigated, as well as those for ammonia, CO and hydrocarbon oxidation. The model has been successfully validated against engine bench measurements, over light-off and ESC tests, under a wide range of conditions, e.g. flow rate, temperature, NO₂/NO ratio, and ammonia injection rate. A very good agreement between the experimental data and the model has been achieved. The model has now been used to predict the effect of NO₂/NO ratio on NO_x conversion, and the effect of different ammonia injection rates on the efficiency of the SCR process.