Distribution of heavy metals and release mechanism for respirable fine particles incineration ashes from lignite

Abstract With the rapid decrease of high-quality coal reserves, utilization of lignite is already a trend in worldwide. Unlike anthracite, lignite often contains special elements Ge, W, As. When these incineration ashes are reused, some resuspended fine particles will inevitably escape into the air, thereby affecting the surrounding environment. The study aims to understand the rule of element distribution of fine particles incineration ash from lignite to avoid the potential risks in future recycling and reuse process of ashes. Hence, we systematically investigated the morphology, element distribution, and chemical species of heavy metals in fine and ultrafine particles. For bottom ash, the large spherical and blocky particles with Dp 10–4.7 were observed in fine particles. The morphology of particles changed to irregular agglomerate particles with Dp 4.7–0.4. The average relative percentage of C, O, Si, and Al in bulk was significantly higher than fine particles, but the heavy metals did not present the rule of enrichment. The residue fraction (F4) of heavy metals were the predominant fraction. For fly ash, some spherical particles of Dp1.1–0.7 and Dp 0.7–0.4 were agglomerated with irregular ultrafine particles. The concentrations of Na, Ge, W, As, Cr, Cd, Pb increased with the decrease of particle sizes. Ca, Al, Mg etc. were acid extractable fraction (F1), and Fe, Pb, As, W, Ni had more proportion of reducible fraction (F2) and oxidizable fraction (F3). A formation of fine particles ashes and release mechanism of heavy metals in incineration process was proposed. Consequently, this study is quite significant for understand rule of element distribution from lignite and future risk prevention from of fine particles.