Investigations of SDPF -Diesel Particle Filter with SCR Coating for HD-Applications

Abstract

Diesel exhaust gas aftertreatment systems, which include the selective catalytic reduction (SCR)*) for reduction of NOx are necessary to fulfil the latest legal requirements and are extensively used in the heavy duty (HD) sector.The present paper informs about some results obtained with SCR and with SDPF (a DPF with SCR-coating) on a medium duty research engine Iveco F1C. Beside the limited gaseous emission components NH3, NO2 and N2O were measured.The analysis of nanoparticle emissions was performed with SMPS and CPC.The integration of functions of filtration and NOx-reduction in one element of exhaust aftertreatment system offers several advantages and is widely investigated and considered as a market solution.Some most important technical statements of the research are: the emissions behavior of SDPF after urea switch-on (SWON) concerning NOx reduction speed and NH3-peak is always fluctuating, due to inhomogeneous distribution of urea, urea products and soot in the filter volume, this even with a carefully conducted conditionings,the active urea injection with fully loaded SDPF causes a lower level of passive regeneration efficiency by mass and a slower backpressure drop in the last, highest step of the regeneration attempt,the loaded SDPF, compared with empty one shows: slower NOx- reduction and higher NH3 after SWON because of use of part of NO2 for soot oxidation and consequently less NO2-availability for the deNOx-reactions; the secondary NP penetration after SWON is clearly lower with the loaded trap,both investigated systems: SDPF and 2 x SCR attain nearly the same deNOx-efficiency,in WHTC with a lower level of exhaust gas temperature SDPF causes lower deNOx-values (40-45% against 75% in ETC), but also lower NH3-emissions.Further developments of those aftertreatment systems, concerning substrates, coatings and reduction agent control, open further potentials of improvements.