Viscosity of a CaO-MgO-Al2O3-SiO2 melt containing spinel particles at 1646K

This article reports an experimental investigation into the effect of solid suspension on the viscosity of molten slags. Up to about 20 vol pct of spinel (MgAl₂O₄) particles of three size ranges (fine: 0.10 to 0.21 mm; medium: 0.21 to 0.44 mm; and coarse: 0.44 to 0.99 mm) were added to a CaO-MgO-Al₂O₃-SiO₂ melt at 1646 (±10)K. A Brookfield DVII+ viscometer was used. The viscosity determined for the solid-free melts was in good agreement with the results of published work. The viscosity for the solid-containing melt was found to increase with the addition of the particles. With more than 10 vol pct solid particles, particularly the fine and the coarse ones, the melt showed an apparent “Bingham” behavior, i.e., the shear stress increased linearly with the shear rate but had a residual shear stress (up to 3 Pa depending on the amount and size of solid added) at zero shear rate. The viscosity of the solid-containing slag, η, was found to fit an Einstein-Roscoe type equation, η=η ₀ (1−af)⁻ⁿ, where η ₀ is the viscosity of the solid-free melt, f is the volume fraction of solid particles in the melt, and a and n are parameters taking the value of 4.24, 3.29, and 3.56 and 1.28, 2.36, and 2.24 for the fine, medium, and coarse particles, respectively, for best fit.