Single-Stage Aerodynamic Separation of Fly Ash Produced after Pulverized Combustion of Coal from the Ekibastuz Basin

Abstract

The single-stage separation of fly ash from field 1 of the electrostatic precipitator of Reftinskaya GRES (Regional Thermal Power Plant), which burns coal from the Ekibastuz Basin, was performed by aerodynamic classification with the use of a flow of air. It was found that, at a constant airflow rate of 50 m³/h, the morphologically uniform fractions of small spherical particles with a narrow distribution, for which d_max was 2, 3, and 4 μm and d₉₀ was 4, 6, and 8 μm, can be separated by decreasing the speed of the classifier rotor from 22000 to 10000 rpm. At a minimum speed of 2000 rpm, the target product of separation was a narrow fraction containing large particles, which were characterized by d_max of 109 μm and d₉₀ of 205 μm. It was established that SiO₂ and Al₂O₃ were the basic chemical components of the fractions obtained, and the total concentration of these components was as high as 86–91 wt %. With increasing the size of fractions with dmax from 2 to 116 μm, a decrease in the concentration of SiO₂ and an increase in the amounts of Al₂O₃ and Fe₂O₃ were observed. The dependence of phase composition on the particle size was established for the small fractions: as d_max was increased in a range of 2–25 μm, a monotonic decrease in the concentration of a quartz phase and an increase in the concentration of mullite were observed; the concentration of a Fe-containing spinel phase also increased.