PETROLOGY AND CHEMISTRY OF FLY ASHES FROM A WESTERN KENTUCKY POWER PLANT: LEGACY OF SHIFTING FUEL SUPPLIES
The changing coal supply has influenced the nature of the fly ash. In all cases, the ash petrology is dominated by Al-Si glass. Combustion of the high-S coal produced a fly ash with a moderate content of Fe-oxides. The glass content of the fly ash increased with the shift away from high-S coal. Carbon content of the fly ash generally increased following the 1990's installation of low-NOx burners. The nature of the fly ash carbon changed with the introduction of subbituminous coal to the fuel blend. Carbons from bituminous coals take the form of inertinite, the macerals passing through the boiler with little or no physical change, and isotropic and anisotropic cokes derived from the thermoplastic melting and repolymerization of vitrinite and low-reflectance semifusinite. Carbons from subbituminous coals are generally chars which have not passed through a plastic phase. Subbituminous chars have a greater capacity to adsorb Hg. The distribution of volatile trace elements other than Hg generally follows a path of enrichment towards the cooler parts of the ash collection system.