Investigation into the coal-based direct reduction behaviors of various vanadium titanomagnetite pellets

Abstract

The reduction behaviors of fired vanadium titanomagnetite (VTM) pellets must be fully ascertained for the effective utilization of VTM concentrates via the coal-based rotary kiln direct reduction-electric furnace smelting process. This paper investigates the effects of the reduction conditions on the reduction behaviors of three types of fired VTM pellets, i. e., Pellets 1, 2 and 3 assaying 13.02%, 11.70% and 5.25% TiO2, respectively, as well as the differences among their reduction behaviors. The results indicate that the highest metallization degree of Pellets 1, 2 and 3 increases sequentially when fully reduced at high temperature for long duration. Pellet 1 shows a good resistance to volume swelling under any reduction conditions, while both Pellets 2 and 3 exhibit the abnormal volume swelling during reduction, with the maximum volume swelling up to 43.78% and 36.45%, respectively. The compressive strength of reduced pellets of Pellet 1 is about 1000N/pellet, whereas below or only close to 500N/pellet for Pellets 2 and 3. Mechanism analysis shows that the minerals compositions and microstructure of fired VTM pellets have great effect on their reduction behaviors. Moreover, the reduction behaviors of fired VTM pellets can be improved by addition of ordinary magnetite in the pellet feeds.

Keywords

• Fired pellets of VTM
• Coal-based direct reduction
• Metallization degree
• Reduction swelling
• Compressive strength