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High Time- and Size-Resolved Measurements of PM and Chemical Composition from Coal Combustion: Implications for the EC Formation Process

Han, Yong, Chen, Yingjun, Ahmad, Saud, Feng, Yanli, Zhang, Fan, Song, Wenhuai, Cao, Fang, Zhang, Yanlin, Yang, Xin, Li, Jun, Zhang, Gan
Environmental science & technology 2018 v.52 no.11 pp. 6676-6685
air pollution, burning, carbon, chemical composition, coal, combustion, furnaces, gases, polycyclic aromatic hydrocarbons, quartz, China
Inefficient coal combustion is a significant source of elemental carbon (EC) air pollution in China, but there is a limited understanding of EC’s formation processes. In this study, high time-resolved particle number size distributions (PNSDs) and size-resolved chemical compositions were obtained from the combustion of four bituminous coals burned in a quartz tube furnace at 500 and 800 °C. Based on the distinct characteristics of PNSD, the flaming stage was divided into the first-flaming stage (with a PNSD peak at 0.3–0.4 μm) and the second-flaming stage (with a PNSD peak at 0.1–0.15 μm). For the size-segregated EC and OC measurements, more soot-EC was observed in particles larger than 0.3 μm, whereas the smaller ones possessed more char-EC. The results indicated that gas-phase and direct-conversion EC generation mechanisms dominate different burning stages. The analysis of 16 parent PAHs showed more high-molecular-weight PAHs in the second-flaming stage particles, which supports the idea of different formation processes for char-EC and soot-EC. For all four coals, the PNSD and chemical compositions shared a similar trend, confirming that the different formation processes of EC in different flaming stages were common. This study provides novel information concerning EC formation.