Extraction of valuable metals from Ti-bearing blast furnace slag using ammonium sulfate pressurized pyrolysis-acid leaching processes
(1. School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China;
2. State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China)
2. State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China)
Abstract: A novel method of extracting valuable metals from Ti-bearing blast furnace slag (TBBF slag) via pressure pyrolysis of recyclable ammonium sulfate (AS)-acid leaching process was proposed. The results show that when pressurized roasting at an AS-to-slag mass ratio 3:1 and 370 °C for 90 min, the extraction rates of titanium, aluminum and magnesium reached 94.5%, 91.9% and 97.4%, respectively. The acid leaching solution was subjected to re-crystallization in a boiling state to obtain a titanium product having a TiO2 content of 94.1%. The above crystallization mother liquor was adjusted to pH=6 and pH≥12.2, respectively, and then qualified Al2O3 and MgO products were obtained. The analysis through XRD and SEM-EDS proves that the main phases in roasted samples were NH4AlSO4, CaSO4 and TiOSO4. The thermodynamic analysis presents that the main minerals of perovskite, spinel and diopside in raw ore could spontaneously react with the intermediate produced by AS under optimal conditions.
Key words: Ti-bearing blast furnace slag; ammonium sulfate; pressurized pyrolysis; high value products