The aim of this paper is to analyse the quantitative impact of fuel sulphur content on particulate oxidation catalyst (POC) functionality, focusing on soot emission reduction and the ability to regenerate. Studies were conducted on fuels containing three different levels of sulphur, covering the range of 6 to 340 parts per million, for a light-duty application. The data presented in this paper provide further insights into the specific issues associated with usage of a POC with fuels of higher sulphur content. A 48-hour loading phase was performed for each fuel, during which filter smoke number, temperature and back-pressure were all observed to vary depending on the fuel sulphur level. The Fuel Sulphur Content (FSC) affected also soot particle size distributions (particle number and size) so that with FSC 6 ppm the soot particle concentration was lower than with FSC 65 and 340, both upstream and downstream of the POC. Conversely, FSC did not have major effects on the soot particle number reduction efficiency of the POC. Soot and other exhaust compounds accumulated within the POC during this phase, gradually built a pressure drop across the POC. The final mass of collected matter in the POC differed significantly according to the sulphur content. The efficiency of removal of gaseous pollutants by the POC was found to be markedly worse for the fuels with higher sulphur content, although this deterioration was observed to be non-linear. Following the accumulation phase, a duty cycle was applied that caused the POC to commence passive regeneration. The time taken for the POC to cleanse itself of accumulated matter and thereby eliminate the pressure drop was observed to increase with increasing fuel sulphur content. The proportion of NO_x leaving the POC in the form of NO₂ was also found to vary as a strong function of fuel sulphur content.

Presenter
Toni Kinnunen