Effect of operating parameters on high-temperature selective enrichment and precipitation of titanium component in Ti-bearing blast furnace slag and the precipitation mechanism of perovskite

Abstract

Ti-bearing blast furnace slag is an important reproducible Ti resource. The effective recovery of the Ti component from this slag can not only alleviate the resultant environmental problems but also overcome the shortage of Ti resources. In this study, the mineral and element of Ti-bearing blast furnace slag were analyzed and adjusted according to the gravity center rule of CaO–SiO2–TiO2 ternary phase diagram. The Ti component in the Ti-bearing blast furnace slag was enriched into the perovskite phase by preoxidation treatment and high-temperature selective enrichment & precipitation. The results indicate that, the preoxidized slag was obtained with adding 2.54% of CaO to the original slag at 1025 °C for 30 min. Subsequently, the preoxidized slag with 1.0% of Fe2O3 was melted at 1470 °C for 40 min, and the temperature was thereupon reduced to 1320 °C at 0.5 °C/min and kept constant for 90 min. The modified slag exhibited obvious enrichment and precipitation of perovskite, which had a crystal size of 63.17 μm and a crystallization volume of 30.62%. The perovskite phase was observed to exhibit mainly an orderly cross-shaped, granular, and beaded arrangement. During the selective enrichment and precipitation process, the fine-grain perovskite crystals fused together, and the concentrations of Ca2+ and TiO32− surrounding the perovskite crystals decreased, which restricted the crystal growth and led to necking. Changes in the surface tension caused the melting point to drop, thereby facilitating remelting and resulting in narrower necking.