Observations and Assessment of Fly Ashes from High-Sulfur Bituminous Coals and Blends of High-Sulfur Bituminous and Subbituminous Coals: Environmental Processes Recorded at the Macro- and Nanometer Scale

Fly ash was investigated with a variety of chemical, mineralogical, petrographic, and microbeam techniques from three coal-fired units at two Kentucky power plants. Two units burn high-sulfur Illinois Basin high volatile bituminous (hvb) coal, and the third unit burns a ∼70:30 blend of high-sulfur Illinois Basin hvb coal and low-sulfur, relatively high-CaO Powder River Basin subbituminous coal. With high-S, high-Fe coals in all of the blends, spinel (magnetite) is an important constituent in the fly ashes. Overall, the fly ashes are dominated by glass. Portlandite was noted in the high-Ca-coal-derived ash. Concentrations of Ba and Sr are highest in the latter fly ash, a function of the Powder River Basin coal source for a portion of the blend. Rare earth elements do not have a high concentration in any of the fly ashes and do not show any significant partitioning between the electrostatic precipitator (ESP) or baghouse rows in the individual generating units. In contrast to previously studied fly ashes fr...