Composition of Individual Microspheres in a Finely Dispersed Fraction from Fly Ash after the Pulverized Combustion of Ekibastuz Coal.

Abstract

A systematic study of the compositions of individual microspheres with sizes of <2.5 μm in a fine fraction of fly ash after the pulverized combustion of Ekibastuz coal was carried out using scanning electron microscopy in combination with energy dispersive X-ray spectroscopy (SEM–EDS). It was established that individual ash microspheres with diameters of <1 and 1–2.5 μm from aerosol particle classes PM1 and PM1–2.5, respectively, form several groups depending on SiO2, Al2O3, and FeO contents, and various mineral precursors participated in the formation of these groups. Microspheres of group (1), in the compositions of which SiO2 + Al2O3 > 90 wt % and FeO < 3 wt %, were formed with the participation of NH4-illite and montmorillonite. Isomorphic mixtures of mixed-layer minerals of the illite–montmorillonite series with a low degree of cationic substitution with iron took part in the formation of microspheres of group (2) containing SiO2 + Al2O3 > 90 wt % and FeO = 3–6 wt %. Mineral precursors of microspheres of group (3), SiO2 + Al2O3 < 90 wt % and FeO to 11 wt %, were mixed-layer illite–montmorillonites with a high degree of cationic substitution with iron and Fe3+ included into interlayer sites.