Preparation of innovative calcium ferrite flux and its application in oxidized pellets of vanadium titano-magnetite

Conventional sintering methods are characterized by elevated energy consumption and significant environmental pollution, particularly when processing complex low-grade iron ores, such as vanadium titano-magnetite. In contrast, pelletizing represents a more environmentally friendly technique for producing agglomerated iron ore products. Consequently, the increased utilization of pellet burden of vanadium titano-magnetite in blast furnace low-carbon ironmaking process has emerged as a critical advancement in the field. To overcome challenges associated with vanadium titano-magnetite pellets such as poor oxidation behavior, the propensity to develop core-shell structures, and low mechanical strength, a calcium ferrite flux was synthesized via sintering and pelletizing techniques and introduced as an innovative additive to improve pellet consolidation characteristics. Experimental findings indicate that the calcium ferrite flux produced by sintering predominantly comprises acicular or tabular silico-ferrite of calcium and aluminum （SFCA）, achieving an effective content of SFCA exceeding 78.54%（area fraction） in particles larger than 5 mm. In contrast, the flux prepared through pelletizing mainly consists of monocalcium ferrite and dicalcium ferrite, with an effective content of SFCA of 97.30% （area fraction）. The addition of 2.0%（mass fraction） pelletized calcium ferrite flux to vanadium titano-magnetite pellets facilitates the formation of liquid phase, such as calcic iron olivine, which acts as effective bridging agents promoting intergranular consolidation. This results in a marked increase in titanium hematite grain size, enhances recrystallization bonding and decreases pellet porosity. 26.2% improvement in pellet compressive strength under consistent preheating and calcination conditions is achieved.