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The development of thermally durable zeolite NH3/Urea-SCR formulations coupled with that of high porosity filters substrates has opened the way to integrate PM and NOx control into a single device, namely an SCR-coated Diesel Particulate Filter (SCRF). A few experimental works are already present in the literature regarding SCRF systems, mainly addressing the DeNOx performances of the system (in both presence and absence of soot) under both steady state and transient conditions. The purpose of the present work is to perform a simulation study focused on phenomena which are expected to play key roles in SCRF systems, such as coupling of reaction and diffusion phenomena, soot effect on DeNOx activity, SCR coating effect on soot regeneration and filtration efficiency and competition between soot oxidation and DeNOx processes involving NO2.

Particulate filters are a widely used emission control device on heavy-duty diesel engines. The accumulation of particulate matter, mostly consisting of soot, inside the filter results in increased filter pressure-drop (backpressure). This increased backpressure has been used by the on-board control systems as trigger for regeneration procedures, which aim to actively oxidize the accumulated soot. However, it is known that passive soot oxidation during normal operation affects the correlation between backpressure and the deposited soot mass in filter. Therefore, the backpressure alone cannot be a reliable trigger for regeneration. In this work we highlight operating conditions with very poor correlation between backpressure and accumulated soot mass in filter and evaluate the possible root causes. Experiments with several heavy-duty diesel engines and particulate filters were conducted on engine test bench.