The effect of TiO 2 on the crushing strength for high-Cr V-Ti magnetite pellets was studied in this paper. On one hand, the crushing strength obviously decreased with the increasing TiO 2 contents. On the other hand, the crushing strength had an obvious increase after grinding treatment for the high-Cr V-Ti magnetite and titanium concentrate. It is found that the crushing strength has great relations with the mineral phase and microstructure. The effect of TiO 2 on the smelting mechanism for high-Cr V-Ti magnetite pellets was also studied in this paper. With the increasing TiO 2 contents in the range of 2.47 to 12.14 pct, the softening start temperature and softening temperature gradually increased, and the softening zone gradually narrowed down; the melting start temperature and the dripping temperature increased, and the melting-dripping temperature zone also increased. The permeability index increased with the increasing TiO 2 contents as a whole. In the process of slag-iron's dripping and separating, it is proposed that amounts of Cr and V moving to the melted iron are obviously more than those moving to the slag, while amount of Ti moving to slag is much greater than that moving to the melted iron. It is demonstrated that Ti(C,N) generates increasingly with the increasing TiO 2 contents and accumulates as especial regular rigid granules on the surface of coke. The size of melted iron decreased with the increasing TiO 2 contents, and this is in accordance with the present investigations that the dripping difficulty increased with the increasing TiO 2 contents.
In the present study, the reduction process of pellet containing high chromic vanadium–titanium magnetite in cohesive zone has been investigated. To elucidate the reduction process including the softening and melting properties, structure changes and migration processes of valuable components (Fe, V, Ti, and Cr) in pellet containing high chromic vanadium–titanium magnetite in cohesive zone, the experiment was carried out at different temperatures and the pellet samples were analyzed by the methods of XRD, SEM, and chemical analysis. The results of reduction process show that the temperature range of cohesive zone of pellet is from 1087.9 to 1338.3 °C and the maximum differential pressure of the burden is 15 859 Pa at the temperature of 1291 °C. The reduction process of pellet was gradually conducted from outside to inside, which could form a layer of iron shell on the outer surface of the pellet. A lot of wustite could be generated in the core of pellet when the reduction temperature exceeded 1100 °C. The migration process of iron is Fe2O3 → Fe3O4 → FeO → Fe, while the generated FeO could react with SiO2 forming 2FeO · SiO2. The reduction process of titanium is Fe2O3 · 3TiO2 → Fe5TiO8 → Fe2TiO4 → FeTiO3 → Ti(O0.19C0.53N0.32) → Ti(C,N) → [Ti] and MgO · TiO2 → Ti(C,N) → [Ti]. The migration process of vanadium is V2O3 → VN, VC → [V] and the chromium oxide was reduced as follows: (Fe0.6Cr0.4)2O3 → FeCr2O4 → [Cr].
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