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Crelling's Petrographic Atlas of Coals and Carbons

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Fly ash carbons from utility power plants

James C. Hower
University of Kentucky
Center for Applied Energy Research
Lexington, KY 40511
Studies of fly ash at the University of Kentucky’s Center for Applied Energy Research have focused on ashes produced at utility power plants throughout Kentucky, with some investigations of plants from other states as well as Israel and Canada.

The coal rank (determined from the vitrinite maximum reflectance) and the maceral content are important in determining the nature of the carbon in the resulting fly ash.  The carbon type is, in part, a function of the coal rank, with higher rank coals having a greater tendency to form anisotropic cokes.  The amount of inertinite macerals in the coal certainly have a relationship to the amount of inertinite in the fly ash.  Vitrinite contributes to the isotropic and anisotropic cokes.  The formation of fly ash cokes from vitrinite is likely a function of both the coal and the combustion parameters.  The classification of fly ash carbons, see the following table, was reduced to four categories: isotropic coke, anisotropic coke, inertinite, and partially combusted coal.  The inorganic constituents in fly ash are classified into glass, quartz, mullite, and spinel.  The latter includes magnetite and other minerals of similar chemistry and mineral structure.  The set of images, with reference to the papers listed below, provide some insight into the type of material we have studied. 


 Affolter, R.H., Groves, Steve, Betterton, W.J., Benzel, William, Conrad, K.L., Swanson, S.M., Ruppert L.F., Clough J.G., Belkin, H.E., Kolker, Allan, and Hower, J.C., 2011, Geochemical database of feed coal and coal combustion products (CCPs) from five power plants in the United States: U.S. Geological Survey Data Series 635, pamphlet, 19 p.
Ban, H., Li, T.X., Hower, J.C., Schaefer, J.L., and Stencel, J.M., 1997, Dry triboelectrostatic beneficiation of fly ash: Fuel, v. 76, p. 801-805.
Bellucci, J., Graham, U.M., Hower, J.C., and Robl, T.L., 1994, Synthetic aggregates prepared from flue gas desufurization by-products using various binder materials: International Pittsburgh Coal Conference, 11th, p. 1123-1128.
Breit, G., Eble, C., Finkelman, R., Affolter. R., Belkin, H., Brownfield, M., Cathcart, J., Crowley, S., Hower, J., Leventhal, J., McGee, J., Palmer, C., Reynolds, R., Rice, C., and Zielinski, R., 1996, Systematic investigation of the compositional variations in solid waste products of coal combustion:   International Pittsburgh Coal Conference, 13th, p. 1356-1361. 

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