Comparative studies of mercury capture by Bulgarian and Kentucky fly ash carbons

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James C. Hower, hower1a@caer.uky.edu, Center for Applied Energy Research, University of Kentucky, 2540 Research Park Drive, Lexington, KY 40511 and Irena J. Kostova, irenko@gea.uni-sofia.bg, Department of Geology and Paleontology, Sofia University “St. Kliment Ohridski”, 15, Tzar Osvoboditel Blvd., 1000 Sofia, Bulgaria.
Fly ash carbons from high volatile bituminous coals, such as the coals burned at most Kentucky power plants, consist primarily of neoformed carbons repolymerized from a vitrinite-derived thermoplastic fluid and inertinite derived, without substantial alteration, from the inertinite component of the feed coal. In contrast, carbons in fly ashes from low-rank coals, such as burned in Bulgarian power stations, consist of inertinite and a vitrinite-derived char. The latter has obviously not passed through a plastic state. In both cases, Hg capture by the fly ash is a function of the temperature at the collection point and the amount of fly ash carbon. The ashes differ in the low-rank-derived carbons having a greater ability to capture Hg, based on a Hg/C ratio, than high volatile bituminous-derived carbons. The Hg/C ratio decrease with the amount of C in the fly ash, perhaps a function of the blinding of interior C surfaces with thicker carbons.