Physicochemical Properties of Fine and Coarse Fly Ash Aerosol Particles from Waste Incineration.

Understanding the physicochemical properties of fly ash from industrial and municipal solid waste incineration is essential for its safe and efficient utilization. This study investigated the particle size distribution and elemental size partitioning in fly ash aerosols from a waste-to-energy (WtE) facility with grate-fired boilers, along with the composition of boiler deposits and ash collected in the electrostatic precipitator (ESP). The physicochemical properties of fly ash were investigated using online aerosol instruments combined with size-selective collection (low-pressure impactor and cyclone-filter setup) for gravimetric and elemental analyses. The particle size distribution was multimodal, with a distinct mass peak at 0.5 μm well separated from two overlapping modes at 30 and 200 μm. Fine particles (<1 μm) represented 16% of the total mass but were dominant in number. Elemental analysis showed that fine particles mainly consisted of Cl, Na, K, Zn, and S. Fine particles were enriched in potentially toxic yet valuable metals (Zn, Cd, Cu, Sb, Pb, Sn). Coarse particles (>1 μm) were dominated by Ca, Si, and Al, while the above-mentioned metals were depleted. Boiler ash resembled the coarse fraction, and ESP ash was a mix of both fine and coarse particles. Increased knowledge of the elemental composition in different size fractions may enable large-scale size separation for improved resource recovery and safer utilization. The composition of the fine particles support targeted salt or metal recovery, while coarse particles are suitable for construction applications.