Structure–Composition Relationship of Platelike Ferrospheres in Calcium-Rich Power Plant Ash
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The structure–composition relationship for polished sections of individual platelike ferrospheres in the–0.04 + 0.032 mm size fraction isolated from fly ash from the combustion of brown coal has been studied systematically by scanning electron microscopy and energy dispersive X-ray spectroscopy. We have identified groups of globules whose overall composition, as well as the composition of local areas on their polished sections, can be represented by general equations for component concentrations: CaO = f(FeO) and SiO2 = f(FeO). Analysis of the structure–composition relationship for the globules leads us to conclude that their structure is determined by transformations that occur in the CaO–Fe x O y system in response to an increase in its oxidation potential. It has been shown that the platelike globules containing 68–73 wt % FeO are made up of Ca2Fe2O5 and CaFe2O4 crystallites resulting from the oxidative transformation of Fe, Ca, and Mg complex humates in the parent brown coal. The ferrospheres containing 79–90 wt % FeO have a fragmentary core–shell structure, where the platelike shell consists of Ca2Fe2O5 and CaFe2O4 crystallites, and the core consists of Fe2O3 and a Ca-, Mg-, and Al-promoted magnetite. Precursors for the formation of this type of globule are pyrite associates with complex humates. It has also been demonstrated that the low concentration of aluminum and silicon oxides in the composition of the globules and the viscosity of their melt have no effect on the structure of the platelike ferrospheres.
Keywordsferrospheres with a platelike structure formation paths
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- 1.Kizil’shtein, L.Ya., Dubov, I.V., Shpitsgluz, A.L., and Parada, S.G., Komponenty zol i shlakov TES (Components of Power Plant Ash and Slag), Moscow: Energoatomizdat, 1995.Google Scholar
- 2.Vassilev, S.V., Menendez, R., Borrego, A.G., Diaz-Somoano, M., and Martinez-Tarazona, M.R., Phasemineral and chemical composition of coal fly ashes as a basis for their multicomponent utilization. 3. Characterization of magnetic and char concentrates, Fuel, 2004, vol. 83, pp. 1563–1583.CrossRefGoogle Scholar
- 3.Ramsden, A.R. and Shibaoka, M., Characterization and analysis of individual fly-ash particles from coalfired power stations by a combination of optical microscopy, electron microscopy and quantitative electron microprobe analysis, Atmos. Environ., 1982, vol. 16, no. 9, pp. 2191–2206.CrossRefGoogle Scholar
- 12.Shpirt, M.Ya., Kler, V.R., and Pertsikov, I.Z., Neorganicheskie komponenty tverdykh topliv (Inorganic Components of Solid Fuels), Moscow: Khimiya, 1990.Google Scholar
- 15.Toropov, N.A., Barzakovskii, V.P., Lapin, V.V., Kurtseva, N.N., and Boikova, A.I., Diagrammy sostoyaniya silikatnykh sistem (Phase Diagrams of Silicate Systems), Leningrad: Nauka, 1972.Google Scholar
- 17.Berezhnoi, A.S., Mnogokomponentnye sistemy okislov (Multicomponent Oxide Systems), Kiev: Naukova Dumka, 1970.Google Scholar