Viscosities and structures of SiO2-CaO-3wt%MgO-10wt%Fe2O3-10wt%Al2O3-Cr2O3 coal slags

The effects of Cr₂O₃ on viscosities and structure evolutions of SiO₂-CaO-3wt%MgO-10wt%Fe₂O₃–10wt%Al₂O₃-(1–5wt%)Cr₂O₃ coal slags were investigated in this work. The viscosity of the coal slag decreased with increasing the Cr₂O₃ content in coal slags. The role of Cr₂O₃ in present systems was clarified. Cr₂O₃ was a basic oxide in the coal slags, and Cr³⁺mainly entered into the slag structures as the form of CrO₆ units to occupy the octahedral positions, which could depolymerize the complex structures. With the addition of Cr₂O₃ into coal slags, the mole ratio of O^2- and O^- raised while the mole fraction of O⁰ declined, suggesting Cr₂O₃ simplified the whole structure of the coal slags and adding Cr₂O₃ to the present slags could lead to a lower viscosity. The variations of slag viscosities were consistent with the change tendencies of structures analyzed by Raman spectra, ²⁷Al NMR and O_1s XPS.