New integrated method to recover the TiO2 component and prepare glass-ceramics from molten titanium-bearing blast furnace slag

Abstract Titanium-bearing blast furnace slag (TBBFS), which contains 15–30 wt% TiO2, is a by-product of the iron-making process and is discharged at approximately 1500 °C. To efficiently utilize molten TBBFS, we propose a new integrated method that the slag was cooled to a certain temperature at which the perovskite precipitated as solid crystals and the supernatant remained in liquid form. The solid component containing perovskite was thereby enriched with TiO2 and separated from the residual liquid by using super-gravity. Simultaneously, the residual liquid was prepared into glass-ceramics by the petrurgic method. Samples were analyzed by XRF, XRD, SEM, and by conducting flexural strength and density tests. The results showed that, during the process of cooling in TBBFS, TiO2 in the form of perovskite precipitated at a temperature approximately 100 °C higher than the precipitation temperature at which pyroxene and melilite precipitated. The optimal temperature for separating perovskite is at 1250 °C and at this temperature, the separated TiO2-rich component had a TiO2 content of 24.44 wt% and a recovery rate of 75.98%. In addition, the glass-ceramics from the residual molten slag had a compact structure and flexural strength of 40.54 MPa and low TiO2 content of 9.46%. The crystals in the glass-ceramics were those of augite and melilite. However, the glass-ceramics contained no perovskite because of the poor TiO2 content, which plays the role of a nucleating agent, and which contributed to the favorable properties of the glass-ceramics.