Modeling the selective catalytic reduction of NO_x by ammonia over a Vanadia-based catalyst from heavy duty diesel exhaust gases

A numerical simulation for prediction of NO_X conversion over a commercial V₂O₅ catalyst with NH₃ as a reductant was performed for a heavy duty diesel engine applications. The chemical behaviors of the SCR reactor are described by using the global NO _X kinetics including standard, fast, and NH₃ oxidation reactions with the Langmuir-Hinshelwood (LH) mechanism incorporated into the commercial Boost code. After introducing mathematical models for the SCR reaction with specific reaction parameters, the effects of various parameters such as space velocities, the O₂, H₂O, NO₂, and NH₃ concentrations on the NOx conversion are thoroughly studied and validated by comparing with the experimental data available in the literature. It is found that NO_X conversion increases with decreasing space velocity, H₂O concentration, and NH₃/NO_X ratio, and increasing O₂ concentration and NO₂/NO_X ratio. The study shows that not only is the present approach adopted is flexible in treating performance of the commercial V₂O₅ based SCR catalyst, it is also accurate and efficient for the prediction of NO_X conversion in diesel exhaust environments.