Methods for Characterization of Composition of Fly Ashes from Coal-Fired Power Stations:  A Critical Overview

Abstract

The present state of the methods commonly used for characterization of the phase, mineral, and chemical composition of fly ashes from coal-fired power stations is described and summarized. The application of various methods is briefly discussed; these methods include macroscopic observations, ashing procedures (high-temperature and low-temperature), physical separations (density, magnetic, particle size, froth flotation, and electrostatic), chemical leaching, sequential physical and chemical treatments, as well as optical microscopy (reflected and transmitted), electron microscopy (scanning and transmission), X-ray diffractometry, differential thermal and thermogravimetric analyses, Mössbauer and infrared spectroscopy, and different chemical analyses. A short critical overview on the advantages and limitations is given, as well as certain recommendations during application of the above-listed methods. Some considerations about the practical use of data for fly ash composition are also present.

A review of the alumina recovery from coal fly ash, with a focus in China

“…Coal fly ash is one of the most complex of the materials that can be characterized [28]. The major crystalline phases characterized are mullite and quartz for most ash and major components are …”

CO2 adsorption on agricultural biomass combustion ashes

“…Ashes are common industrial-sourced alkaline byproduct (Gerdemann et al 2007, Wilcox 2012. They contain about 90% and 99% inorganic compounds and between 1% and 9% organic compounds (Vassilev 2005). The main inorganic substances of coal combustion ashes are silicon dioxide (SiO 2 ), calcium oxide (CaO), iron oxide (Fe 2 O 3 ), magnesium oxide (MgO) and aluminium oxide (Al 2 O 3 ) (Hong et al 2009, Malik and Thapliyal 2009, Wilcox 2012.…”

Variations in fly ash composition with sampling location: Case study from a Portuguese power plant

“…Since fly ash is a heterogeneous and complex anthropogenic material, and, like coal, includes organic and crystalline and amorphous inorganic phases, a large number of techniques may be applied in fly ash characterization (French et al, 2007;Vassilev & Vassileva, 2005), to study FA mineralogy (Raask, 1982;Vassilev & Vassileva, 1996a;Ward & French, 2006), morphotypes (Anshits et al, 1998;Bailey et al, 1990;Fomenko et al, 1998a,b;Hower & Mastalerz, 2001;Hower et al, 2005;Sokol et al, 2002;SuarezRuiz & Valentim, 2007;Vassilev & Vassileva, 2007), Hg capture by carbon (Hower et al, 2000;Senior & Johnson, 2005), magnetic properties (Anshits et al, 2000;Hansen et al, 1981), the environmental and technological behavior of trace elements, the mechanisms for concentration enhancement, the relation between trace elements and fly ashes (Block & Dams, 1979;Clark, 1993;Conzemius et al, 1984;Danihelka et al, 2003;Donahoe et al, 2007;Finkelman et al, 1990;Haynes et al, 1982;Meij, 1994;Meij & Winkel, 2009;Swaine, 1990Swaine, , 2000Valkovic, 1983;Yan et al, 2001), and chemical classification of fly ashes (Roy & Griffin, 1982;Vassilev & Vassileva, 2007), among others. Therefore, a case study of FA from a TPP was conducted using several characterization techniques in order to see if FA variations inside a TPP are exclusive of some properties or if they cover a wide range of situations: granulometry, carbon content, major oxides and chemical classification, mineralogy and phase-mineral classification, and trace elements (Cr, Cu, Mn, Ni, ...…”