Particle number, size distribution, carbons, polycyclic aromatic hydrocarbons and inorganic ions of exhaust particles from a diesel bus fueled with biodiesel blends

Abstract

The primary purpose of this study is to evaluate effects of waste-cooking-oil biodiesel on the particle number (PN), size distribution and particulate-phase compositions including organic carbon (OC), elemental carbon (EC), polycyclic aromatic hydrocarbons (PAHs), N-alkanes, fatty acids and inorganic ions from a diesel bus. Experiments were conducted based on chassis dynamometer with three biodiesel blends at 5%, 10% and 20% by volume, i.e., B5, B10 and B20; and a petroleum diesel D100 was used as a baseline. Results showed that the biodiesel resulted in a reduction in the PN emission, and this reduction increased linearly with the biodiesel ratio. For B20, the reduction in PN emission reached 42.2% in comparison with D100. The particle size distribution indicated that the utilization of the biodiesel increased the proportion of nucleation mode particles, and correspondingly diminished the proportion of accumulation mode particles. Compared with D100, 14.8%, 21.2% and 27.6% reduction in the OC emission was observed for B5, B10 and B20, whereas the EC emission increased slightly, consequently, the ratio OC/EC presented a declining trend. The PAHs, dominated by 3- and 4- rings ones, as well as their toxic equivalent were also reduced with the biodiesel. Additionally, using biodiesel led to lower N-alkanes and fatty acids emissions in the particles, and the reduction of emissions showed a decreased and increased trend with the biodiesel ratio, respectively. In terms of the inorganic ions in the particles, the Cl−, NO2−, NO3−, SO42−, as well as the Na+, NH4+, K+ and Ca2+ emissions were increased with the biodiesel. To sum up, the refining of biodiesel from waste cooking oil is a cleaner production, and as an alternative fuel to petroleum diesel, the biodiesel is also environment-friendly.