Energies (Jul 2022)
The Composition and Origin of PM<sub>1-2</sub> Microspheres in High-Calcium Fly Ash from Pulverized Lignite Combustion
Abstract
This article presents the results of a systematic study on the composition and origin of PM1-2 microspheres in high-calcium fly ash. The composition of individual microspheres was studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy. It is shown that the compositions of the analyzed microspheres satisfy the general dependency with a high correlation coefficient: [SiO2 + Al2O3] = 88.80 − 1.02 [CaO + Fe2O3 + MgO], r = −0.97. The formation pathway is parallel to the general trend: anorthite, gehlenite, esseneite, tricalcium aluminate, ferrigehlenite, and brownmillerite. The microspheres were classified into four groups depending on the content of major components: Group 1 (CaO > 40, SiO2 + Al2O3 ≤ 35, Fe2O3 2 + Al2O3 ≤ 40, Fe2O3 2 + Al2O3 ≤ 75, Fe2O3 2 + Al2O3 2O3 > 30, MgO ≤ 14 wt %). A comparative analysis of the relationship between major component concentrations suggests the routes of PM1-2 formation from feldspars and Ca–, Mg–, and Fe–humate complexes during lignite combustion.
Keywords