Fe-Zeolite SCR Model Development, Validation and Application 2011-01-1304
Selective Catalytic Reduction (SCR) technology has been widely studied for removal of NOX from the exhaust of diesel engines. To design and optimize diesel engine aftertreatment systems including an SCR catalyst component, a reliable SCR model is a very useful tool, to aid in system integration and control algorithm testing. In this paper, the development of a one-dimensional numerical model for a Fe-Zeolite-based SCR catalyst (hydrothermally aged for 100 hours at 650°C in 10% H₂O in air) is presented, followed by its validation and application. The resulting model is capable of predicting NOX reduction efficiency under various operating conditions as a function of gas hourly space velocity (SV), temperature, NO₂/NOX ratio and NH₃ to NOX (ANR) ratios; NH₃ slip and N₂O formation are also correctly predicted by the model. Extensive validation of the model has been carried out against engine test data for both steady state light-off and the heavy-duty FTP transient cycle (HD-FTP). Good agreement between model prediction and the engine test results was achieved. Finally, the model is used to optimize the instantaneous ANR ratio before the SCR catalyst over the HD-FTP, by minimizing SCR outlet NOX and NH₃ emissions. Results show very good potential for improving the urea/NH₃ dosing strategy for Fe-based SCR catalyst applications.