Model Based Study of DeNOx Characteristics for Integrated DPF/SCR System over Cu-Zeolite 2015-01-1060

The SCR Filter simultaneously reduces NO_x and Particle Matter (PM) in the exhaust and is considered an effective way to meet emission regulations. By combining the function of a Diesel Particulate Filtration (DPF) and a Selective Catalytic Reduction (SCR), the SCR Filter reduces the complexity and cost of aftertreatment systems in diesel vehicles. Moreover, it provides an effective reaction surface and potentially reduces backpressure by combining two devices into one. However, unlike traditional flow through type SCR, the deNOx reactions in the SCR Filter can be affected by the particulate filtration and regeneration process. Additionally, soot oxidation can be affected by the deNOx process.

A 1-D kinetic model for integrated DPF and NH₃-SCR system over Cu-zeolite catalysts was developed and validated with experimental data in previous work[1]. In the current work, the reaction kinetics, and interaction between soot and SCR reactions are analyzed to give a clear review on chemical and physical process inside the filter. Extensive studies on the effect of the NO₂/NO_x ratio, ANR (ammonia to NO_x ratio), temperature, and SV (gas hourly space velocity) on clean filter deNOx efficiency at both steady and transient states are presented, followed by the soot influence on deNOx performance. This soot influence is studied for the wall soot and cake layer cases separately, and the wall soot was found to have a larger effect on SCR reactions compared to the soot inside cake layer. It was also observed that the soot promotes the concentration of adsorbed ammonia.