Relationship between the phases, structure, MgO migration and the reduction performance of the pre-oxidized vanadium-titanium magnetite ore in a fluidized bed

Abstract

This paper contrastively investigated the reduction behavior of raw and oxidized vanadium titanium magnetite ore (RVTM and OVTM) in a bubbling fluidized bed at 800°C under 75%N2-25%H2, and systematically revealed the relationship between the structure, phases change, MgO migration behavior and the reduction performance. Microstructure observations suggest that oxidization conditions greatly affect structural evolution, phase transformation of Fe-Ti oxides, and migration of MgO in OVTM. The reduction results indicated that the average metallization degree enhanced by 8-10% as the OVTM ore had high oxidization degree. When the RVTM ore was treated at 800°C, the reduction rate increased with the increase of oxidization degree, no significant difference was observed among these oxidized samples due to their similar internal and surface structure. However, the reduction rate of OVTM at 950°C depended on the oxidization time. The reduction rate of OVTM oxidized at 950°C for 2 h was faster than the one for 1 h, which was attributed to the better exsolution of MgO and the formation of bigger pores, even though both samples were fully oxidized and Fe2TiO5 formed in the oxidization process.