Diesel Emission with DPF+SCR in VERTdePN - Testing & Potentials 2011-01-1139

The most efficient way and the best available technology (BAT) to radically reduce the critical diesel emission components particles (PM&NP) and nitric oxides (NO_x) are combined exhaust gas aftertreatment systems (DPF+SCR). SCR (selective catalytic reduction) is regarded as the most efficient deNO_x-system, diesel particle filters are most efficient for soot abatement. Today, several suppliers offer combined systems for retrofitting of HD vehicles.

The presented results are part of the work in the international network project VERT *) dePN (de-activation, de-contamination, disposal of particles and NO_x), which has the objectives to establish test procedures and quality standards and to introduce the SCR-, or combined DPF+SCR-systems in the VERT verification procedure.

Examples of results for some of the investigated systems are given and the most important findings are: - the average NO_x conversion rate at transient operation strongly depends on the operation load profile, on the exhaust gas temperature and the resulting urea dosing control, - the particle number filtration efficiency, which is verified at stationary engine operation, is valid also at the transient operation, - secondary nanoparticles are produced due to urea injection, they nevertheless do not impact significantly the overall filtration efficiency of the system (here: DPF upstream & SCR downstream, differences of PCFE in the range of 0.1%), - the OEM NO_x-sensors of the investigated systems are appropriate tools for the in-use control, - the system with catalyzed DPF (upstream) attains higher overall deNO_x-efficiencies due to NO₂-production in the DPF, - for the investigated systems there are no critical emissions of unregulated components, NH₃ & N₂O.