Formation and migration of trace elements in condensable particulate matter with the finest particle size distribution

There is a lack of existing studies on the effect of particle size distribution on the condensation behavior of trace elements (TEs) in condensable particulate matter (CPM) surfaces. The effects of TEs on the formation of PM10 and CPM10 with different particle sizes in coal-fired flue gas were studied using an entrained flow reactor. Hg and Se were enriched in ultra-fine CPM. As, Pb, and Cr were enriched in sub-micron and ultra-micron PM. For Hg2+, As3+ and Cr6+, a higher toxicity state was observed in PM10. For Se4+, a higher toxicity state was observed in CPM10. TEs in the form of volatile elements and oxides tend to be enriched in ultra-fine particle sizes, while TEs in the form of metal salts tend to be enriched in sub-micron and ultra-micron particle sizes. The formation mechanism of TEs on PM and CPM surfaces was closely related to the volatility and speciation of TEs and the particle sizes of PM and CPM. The results established the qualitative (speciation of TEs) and quantitative (concentration of TEs) correlation between TEs and the finest particle sizes. This study will help to better control the emission of TEs and CPM during coal combustion.