Transient simulation of NO _x reduction over a Fe-Zeolite catalyst in an NH ₃ -SCR system and study of the performance under different operating conditions

The NO

reduction in an ammonia SCR converter has been simulated by a 1D+1D model for a single representative channel to parametrically study the characteristics of the system under typical operating conditions. An appropriate model has been selected interpreting the chemical behavior of the system and the parameters are calibrated based on a comprehensive set of experiments with an Fe-Zeolite washcoated monolith for different feed concentrations, temperatures and flow rates. Physical and chemical properties are determined as well as kinetics and rate parameters and the model has been verified by experimental data at different operating conditions. Three different mechanisms for the surface kinetics to model NO

reduction have been assessed and the results have been compared in the cases of steady DeNO

performance and transient response of the system. Ammonia inhibition is considered in the model since it has a major effect specifically under transient operating conditions. Effects of the operating temperature, the gaseous flow rate and the species concentrations such as ammonia dosage and the ratio of NO and NO₂ have been investigated. It has been shown that recently proposed dual site chemical kinetics for Fe-Zeolite catalysts are especially suited to predict the transient operation of the system during ammonia feeding and the inhibition effect after shutting off ammonia. Accurate numerical results for various cases are a strong indication for the validity of the model under the typical operating conditions of an SCR system. This study helps to find the optimum performance of the system under different conditions including a wide range of working temperatures with different flow rates and concentrations.