2017 Volume 57 Issue 7 Pages 1156-1165
Based on the gas-based direct reduction followed by melting separation process, the melting separation process of high chromium vanadium-bearing titanomagnetite metallized pellet and its optimization by multi-index synthetic weighted scoring method are studied in the present work. The optimal melting separation parameters include a melting temperature of 1650°C, a melting time of 45 min, and a basicity of 1.10. Under these conditions, the recoveries of Fe, V, Cr, and TiO2 reach 99.87%, 98.26%, 95.32%, and 95.04% respectively; the mass fraction of Fe, V, Cr, and TiO2 are 94.16%, 0.94%, 0.76%, and 38.21% respectively. The basicity has the strongest effect and its effect on the melting separation kinetic is more significant than thermodynamic. As increased basicity from 0.6 to 1.1, the slag viscosity decreases and surface tension increases, which are both attributed to smooth melting separation and improved indexes. But further increasing basicity to 1.2, the amount of CaTiO3 and slag melting point increase, and the slag amount is relatively excessive, then all the melting separation indexes decrease instead. The melting separation contains four key behaviors: Fe–C melt formation and Fe(l) generation; slag melting initiation and slag(l) generation; small iron droplets formation and start of iron-slag separation; continuous aggregation and growth of iron and accomplishment of iron-slag separation. The iron aggregation and growth should go through iron crystal nucleus formation, reaction interface formation and enlargement, and subsequent reaction interface decrease.
