Hydrothermal aging modeling for SCR catalysts

Simon  Dosda, IFP Energies nouvelles

Urea-SCR is one of the most common technology used by car and truck manufacturers to meet the latest NOx emission standards. During engine lifetime, performance degradation of the SCR catalyst is observed due to harsh exhaust conditions. To limit deNOx degradation and ammonia released in the atmosphere with the aging of SCR catalysts, urea injection strategy needs to be adapted. In that context, system simulation approaches are very flexible tools that allow to create virtual exhaust lines and perform, in a quite short time and with reduced cost, a large number of tests over a wide range of operating conditions.
In this work, the effects of hydrothermal aging on a SCR catalyst have been studied in order to model their impact on both ammoniac storage and NOx reduction efficiency. A model of a fresh SCR has been calibrated on data from both synthetic gas bench and engine bench tests. The hydrothermal aging impact on the SCR catalyst has then been studied on synthetic gas bench using several aging conditions. Using these experimental data combined with results from previous work on catalyst aging modeling, a hydrothermal aging model has been developed to represent the evolution of the SCR catalyst performance. This model has then been validated on data from a complete exhaust line having an aged SCR.
This methodology has been proved to be very efficient in modeling the behavior of SCR catalysts aging, allowing to easily take into account the deNOx efficiency and NH3 storage degradation in exhaust line simulation.

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