Size distributions, PAHs and inorganic ions of exhaust particles from a heavy duty diesel engine using B20 biodiesel with different exhaust aftertreatments

Exhaust particle emissions from a heavy duty diesel engine using B20 biodiesel (20% biodiesel blend with 80% diesel by volume) were investigated, and the engine was equipped with three kinds of exhaust aftertreatment devices: DOC (diesel oxidation catalyst), DOC + DPF (diesel particle filter), and DOC + CDPF (catalyzed diesel particle filter). Particle mass, particle number and size distribution, and PAHs (polycyclic aromatic hydrocarbons) and inorganic ions in the particle emissions from the engine were studied. Compared with the engine without exhaust aftertreatments, DOC decreased nucleation mode particle number by 19.83%, while accumulation mode particles exhibited slight changes. The DOC + DPF reduced the total particle number by 82.54%, while the DOC + CDPF reduced it by 91.71%. Compared with the engine without exhaust aftertreatments, the three aftertreatments were shown to reduce total PAH emissions. DOC + DPF and DOC + CDPF can decrease total TEQ (toxicity equivalent quantity) effectively with a sharp decrease in PAH mass. The DOC increased the TEQ of particles by 46.9%. The catalyst in the DOC increased some high molecular weight PAHs such as BaA, BbF + BkF, and BaP, which led to the increase in TEQ. The DOC increased the total inorganic ions by 2%, while the DOC + DPF and DOC + CDPF decreased inorganic ions by 89.5% and 82.9%, respectively. Catalysts in DOC and CDPF promotes the formation of SO42− and NO3−, which leads to higher inorganic ion emissions with DOC than no aftertreatments and higher inorganic ion emissions with a DOC + CDPF than with a DOC + DPF.