Effects of Basicity and Al2O3 Content on Viscosity and Crystallization Behavior of Super-High-Alumina Slag

The CaO-SiO2-MgO-Al2O3 slags with high alumina content are widely applied in various pyrometallurgical processes. However, for super-high-alumina slags, especially for those with alumina content of more than 25 wt%, there is a lack of relevant studies about the properties of slag. The melting behavior, viscosity, structural property, and crystallization behavior of high-alumina slag with the fixed MgO content of 11.13 wt% and Al2O3 content from 27.61 wt% to 40 wt% were investigated. The results revealed that the liquidus temperatures and complete solidification temperatures of slag increased with the increasing binary basicity and Al2O3 content. The melting temperature and viscosity of the CaO-SiO2-11.13wt%MgO-Al2O3 slag system increased with the increasing basicity from 0.8 to 1 and Al2O3 content from 27.61 wt% to 40 wt%. The increase in Al2O3 caused the formation of high-crystallinity and high melting point materials in the slag, such as spinel and angstrom kermanite. A large number of non-uniform phases could quickly crystallize out of the solids present in the slag melt, thereby increasing the slag viscosity and deteriorating the fluidity of the slag.