The Crystallization Behavior of TiO2-CaO-SiO2-Al2O3-MgO Pentabasic Slag with a Basicity of 1.1–1.4

Abstract

The utilization of titanium-containing blast furnace slag has been an unsolved problem for a long time. Failure to make effective use of the slag, which is caused by a high TiO2 content within it, not only results in a waste of resources, especially titanium, but also increases environmental risk. The key to address the problem is the enrichment and extraction of TiO2 from the slag first. Therefore, in order to study the enrichment of titanium, the crystallization behavior of TiO2-CaO-SiO2-Al2O3-MgO pentabasic slag, the main compositions of titanium-containing blast furnace slag, within the basicity range of 1.1–1.4 was investigated theoretically and experimentally. Thermodynamic calculation shows that perovskite is the main titanium-containing phase and titanium can be enriched in perovskite. By decreasing the temperature, perovskite precipitates at first. Additionally, with the increase of basicity, perovskite precipitation temperature increases continuously, and its amount of precipitation almost does not change, while the amounts of other phases change obviously. The experimental results demonstrate similar results except for the amount of perovskite (with the increase of basicity, perovskite precipitation amount increases slightly), caused by kinetic reason. In addition, the morphology of the slag at different scales was observed. The surface of the cooled slag is granular, vein-like, and irregular, multilaterally shaped from outside to inside. The crystal is dendritic with a spine-like trunk, and the edge is blade-like. In terms of the structure of the crystal, the inner part of it is perovskite, and the outer part is covered with a layer of other phases with spinel inlaying it. Finally, the precipitated mechanism is proposed as well.