Influence of Coating MgO on Sticking and Functional Mechanism during Fluidized Bed Reduction of Vanadium Titano-magnetite

The vanadium titano-magnetite (VTM) iron ore fines of 110–150 μm in diameter were reduced in a transparent quartz fluidized bed by 70%CO-30%H2 (volume fraction) mixtures. MgO powders served as coating agent to solve sticking problem. Two coating methods were introduced in this experiment: high temperature injection method and briquetting→oxidizing roast→crushing method. According to the experimental results, the minimum effective coating amount of MgO was 0.1 mass%. The metallization ratio (MR) of the product rose from around 58% to above 90% with the above treatments. To investigate the sticking mechanism of fine ore, the morphology evolution was investigated. Instead of iron whiskers, an interlaced fibrous porous surface formed. The ulvospinel (2FeO · TiO2) in VTM is more difficult to be reduced than FeO according to thermodynamic calculation. XRD results showed that MgO diffused into Fe2O3 lattice before forming pleonaste (MgO · Fe2O3) during oxidizing roast at 1273 K. The melting point of the pleonaste is 1986 K and that made contribution to prevent the sticking problem.