Narrow Dispersed Fractions of High-Calcium Fly Ash Produced from the Pulverized Combustion of Irsha-Borodinsky Coal

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.By means of airflow aerodynamic classification, high-calcium fly ash (with a bulk density of 1.14 g/cm3 and size distribution parameters of dav = 5 µm and d90 = 14 µm) produced from the combustion of Irsha-Borodinsky coal and sampled from the fourth field of the electrostatic precipitator at the Krasnoyarsk TPP-2 has been separated. The obtained morphologically homogeneous fractions of spherical particles with a narrow distribution are characterized by dav = 1, 2, 3, 4, and 10 μm and d90 = 3, 4, 5, 9, and 16 μm. It has been established that the main chemical component of the obtained narrow fractions is represented by CaO with a content of 34–43 wt %; the content of the other components is as follows: 15–34 wt % of SiO2, 13–16 wt % of Fe2O3, 9–10 wt % of MgO, 8–10 wt % of Al2O3, 2–10 wt % of SO3. The phase composition has 35–49 wt % of crystalline calcium-containing compounds, including 11–15 wt % of aluminum substituted calcium ferrite and 8–11 wt % of tricalcium aluminate, which are the main phases of Portland cement. The content of crystalline quartz amounts to 2–7 wt %, and that of the amorphous glass phase is 41–51 wt %. It has been established that, as the average fraction size dav obtained after the aerodynamic separation of ash increases from 1 to 10 μm, the bulk ash density exhibits an increase from 0.89 to 1.50 g/cm3 and the content of the magnetic component also increases, amounting up to 4 wt %. At the same time, the chemical composition of the fractions exhibits an increase in the content of SiO2 as well as a decrease in the content of Al2O3 and SO3. The content of СаО and Fe2O3 in the fractions having dav = 1–3 μm increases, then it exhibits an abrupt decrease with increasing particle size. As far as the phase composition is concerned, an increase in the content of crystalline quartz is observed, and the total fraction of calcium-containing phases gradually decreases. At the same time, the percentage of calcium sulfate decreases and the percentage of free calcium oxide exhibits a considerable increase. The content of calcium hydroxide increases in the fractions having dav = 1–2 μm and then decreases with increasing particle size

Одностадийное аэродинамическое разделение золы-уноса от пылевидного сжигания угля Экибастузского бассейна

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.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 dmax 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 dmax 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 dmax 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

Separation of Nonmagnetic Fine Narrow Fractions of PM10 from Coal Fly Ash and Their Characteristics and Mineral Precursors

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.Nonmagnetic fine narrow fractions of particles with mean diameters of 2, 3, 6, and 10 μm were for the first time separated from fly ash produced by pulverized combustion of Ekibastuz coal using aerodynamic classification with subsequent magnetic separation. These fractions were characterized by the size distribution, bulk density, and chemical and phase compositions. The particle size distributions correspond to d50 values of 1.9, 2.3, 5.1, and 9.2 μm. As the fraction particle size increases, the bulk density was found to rise gradually from 0.90 to 1.07 g/cm3. The main components of the chemical composition were SiO2 (65–70 wt %) and Al2O3 (23–28 wt %). The phase composition was represented by the glass phase (64–69 wt %), mullite (17–21 wt %), and quartz (10–18 wt %). The main morphological particle types were microspheres with a nonporous smooth surface and microspheres with a porous shell. With an increase in the fraction particle size, the percentage of microspheres with a porous shell increases. The largest fraction contains particles with a network structure. Single-particle scanning electron microscopy–energy dispersive X-ray spectroscopy analysis of nonporous microspheres with a diameter of 1–2 μm, approximate in composition to the internal coal minerals, indicated that, depending on the content of SiO2, Al2O3, and FeO, they form several groups differing in mineral precursors. Thus, for microspheres of group 1 (SiO2 + Al2O3 > 95 wt %), the mineral precursors are NH4-illite and montmorillonite; group 2 (SiO2 + Al2O3 = 90–95, FeO ≤ 4 wt %)—minerals of the isomorphic montmorillonite-illite series, including phases with a low level of iron cation substitution; group 3 (SiO2 + Al2O3 = 90–95, 4 < FeO ≤ 6 wt %) and group 4 (SiO2 + Al2O3 < 90, 3 < FeO ≤ 9 wt %)—minerals of the illite-montmorillonite series, with a high level of iron cation substitution and with Fe3+ in interlayer sites

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

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.A systematic study of the compositions of individual microspheres with sizes of 90 wt % and FeO 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