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New Diesel exhaust gas aftertreatment systems, with combined DPF*) and deNOx (mostly SCR) systems represent a very important step towards zero emission Diesel fleet. These combined systems are already offered today by several suppliers for retrofitting of HD vehicles. Reliable quality standards for those quite complex systems are urgently needed to enable decisions of several authorities. The present report informs about the international network project VERT *) dePN (de-activation, de-contamination, disposal of particles and NOx), which was started in Nov. 2006 with the objective 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. These investigations included parameters, which are important for the VERT quality testing: besides the regulated gaseous emissions several unregulated components such as NH3, NO2 and N2O were measured.

The first two of a series of traps retrofitted on a pilot fleet of 110 buses of the Athens Bus Corporation were removed for examination after 100,000 km of revenue service. These buses were gradually equipped with the ELBO Trap Oxidiser since the beginning of 1989 and are constantly operated on Cerium based fuel additive. The physical properties and the chemical composition of filters and ash residues were analysed by the filter manufacturers and the fuel additive producer. The results have shown that after two years of operation the filter material remained intact and the ash deposits (consisting mainly of CeO2) exhibit a limited interaction with the cordierite. More than 94% of these deposits are filtered by the monoliths and could be removed to a large extent with the application of conventional methods.

This paper describes the performance of a new, catalytically acting cerium-based fuel additive in relation to particulate trap regeneration quality, trap filtration efficiency, particle size distribution and fate of additive under steady-state engine operation conditions. The impact of the cerium fuel additive is compared to ferrocene respectively copper based fuel additives. The cerium-based fuel additive DPX6 lower the ignition temperature down to 200 °C. Frequent, so-called quasi-continuous, and smooth regenerations are induced by the cerium fuel additive in that temperature range. Thus, the regeneration quality is quite different to the stochastic and rapid oxidation known from ferrocene and copper. Out of this, the thermal stress with cerium fuel additive will be lower even when regenerations start at comparable high trap loading.