Abstract
The Urea-SCR system has commonly been introduced commercially due to the high performance of NOx reduction, and much research has been conducted to invent low noble metal catalysts effective at low exhaust temperatures. The CFD (computational fluid dynamics) with a reaction model is effective for the SCR catalyst development and many SCR simulation models have been proposed. However, the experimental feedback of engine emission tests is required for simulations and fitting parameters in the models are adjusted by the experiment results. This is a cause of the low versatility of the reaction models. The development of reaction model for Cu-ZSM-5 zeolite catalyst without dependence of engine test data is a target of this research. The reaction rates of Standard-SCR reactions, molecular diffusion in catalyst coated layer, and structural parameters of honeycomb catalysts are introduced in the simulations to develop a versatile ammonia-SCR reaction model and the simulation results are compared with the experiment results. The calculated results of the ammonia-SCR model have correlate well with the surrogate gas tests up to 250 °C, and the correlation is poor above 300 °C because the ammonia oxidation is not considered in the simulation. Further, it was obvious that the inhibition reaction of hydrocarbons should be considered to simulate the ammonia-SCR reaction in the engine exhaust emissions.
