Chemical characterization of density separated submicrometer coal fly ash

A new geometrical particle size separation method in the range of submicrometer has been developed for coal fly ash. Coal fly ash particles prefractionated less than 5m in geometrical diameter were fractionated with a coupling of supersonical dispersion in methyl alcohol and filtration through antistatic Nucleopore filter into >1.0, 1.0–0.8, 0.8–0.6m.Submicrometer (1.0–0.6m) and micrometer coal fly ash (25–20m) were separated into six density fractions and their compositions measured by SEM-EDX were compared. For the both size fractions, for the low density fractions (<2.8 g/cm³) consisted mainly of aluminosilicates and the fractions of 2.8–3.2 g/cm³ consisted of oxides of aluminum, silicon and calcium, and in the fraction above 3.2 g/cm³ iron was rich. In submicrometer fly ash, phosphor and sulfur concentrated to the particles rich in calcium. In the heaviest fraction, the particles containing over 30 wt% titanium as oxide observed among the particles rich in iron. These fractions were revealed not as a single component, but as mixtures of several components.