Industrial Experimental Research on Titanium Extraction from Blast Furnace Slag: Mechanism of High-Temperature Carbonization

The “high-temperature carbonization and low-temperature chlorination process” can recover titanium from high-titanium blast furnace slag containing 20–25% TiO2 at 1450–1700 °C and 500–600 °C. The carbonization process was carried out in an industrial three-phase AC electric furnace with a rated power of 9000 kVA. Through Factsage calculations, XRD, SEM-EDS, and industrial data collection, the mechanism of carbonization and the impact of smelting parameters were illustrated. The results indicated that Ti primarily existed as titanaugite or perovskite in the slag, and the reduction reaction of TiO2 began at 1301 °C. But to complete perovskite transformation, a temperature exceeding 1550 °C was necessary. When the reaction began, the reaction rate of TiO2 to Ti2O3 was faster than that of Ti2O3 to TiC, and TiC grains appeared as small island-shaped particles (0–3 μm) and larger aggregates (0–10 μm) surrounding Fe. Furthermore, as the molten pool was agitated, the TiC particles detached from the surface of the carbon and it became very difficult for them to grow. In the final reaction stage, most of the TiC contained a certain amount of oxygen and was dispersed, with a particle size of 0–5 μm and a settling tendency. In terms of industrial production, the results indicate that employing coke with a particle size of 0.074–1 mm, maintaining a bath temperature ≥1550 °C, and implementing stage-specific power supply protocols (particularly for the high-conductivity final stage) are crucial for achieving a ≥88% industrial carbonization rate.