Primary Carbonaceous Particle Emission from Four Power Plants with Ultralow Emission in China.

Abstract

Particulate matters (PMs) were collected in stacks from two types of ultralow emission coal-fired power plants by a heated electrical low-pressure impactor (HT-ELPI+), including ultralow emission pulverized combustion technology boilers (ULPCBs) and ultralow emission circulating fluidized bed boilers (ULCFBs). The characteristics of organic carbon (OC) and elemental carbon (EC) in size-resolved particles were analyzed. The ultralow emission technologies significantly decreased the mass concentrations of the carbonaceous content, and the emission concentrations of OC and EC ranged from 5.64 to 17.9 μg/m3 for ULPCBs and from 0.57 to 1.85 μg/m3 for ULCFBs. However, the number concentration of particles was not significantly decreased in the four ultralow emission power plants. The OC in the particle emission of ULPCBs presents a bimodal size distribution with the particle size, while three successive unimodal distributions were observed in the ULCFB emission. Compared to ULPCBs, much more char-EC and soot-EC condensed in the particles, which were collected from ULCFBs. Furthermore, the char-EC/soot-EC in the particle fractions of ULPCBs characterized by the “V” type with the sequence of PM1.0 > PM2.5–10 > PM1.0–2.5, differing from the PM1.0 > PM1.0–2.5 > PM2.5–10 of ULCFBs. The ratios of OC/EC in the stacks from two types of boilers did not show obvious variations in particle size distributions, and the mean OC/EC was far higher than those for non-ultralow emission power plants. Considering the impact of OC1, OC4, and EC1, the ratio of high-temperature organic carbon (HTOC, defined as OC2 + OC3) and soot-EC was studied. The HTOC/soot-EC increased with the increase of RH in the stack, and the highest HTOC/soot-EC values were obtained from ULPCBs (33.0% (PM1.0), 11.4% (PM1.0–2.5), and 23.9% (PM2.5–10)). Meanwhile, strong correlations (0.69–0.85, p < 0.001) between HTOC and soot-EC were obtained, implying that HTOC and soot-EC probably simultaneously condensed in the purification equipment.