Reduction disintegration behavior and crystallographic transformation of vanadium-titanium magnetite pellets during hydrogen-based reduction

There are many advantages of the smelting of vanadium-titanium magnetite pellets by hydrogen-based shaft furnace pre-reduction and electric arc furnace process, including high reduction efficiency, low carbon dioxide emission and high recovery of titanium and so on. The preparation of qualified vanadium-titanium magnetite pellets with low reduction disintegration index (RDI) is prerequisite of this process. The reduction disintegration behavior of vanadium-titanium magnetite pellets during hydrogen-based reduction was systematically investigated in this work, and the crystallographic transformations during the reduction were dug into as well. The RDI+6.3 mm of vanadium-titanium magnetite pellets reached 43.28% after 60 min of reduction at 500 degrees C in a Midrex atmosphere (36% CO, 5% CO2, 55% H2, and 4% CH4). During the reduction of trigonal titano-hematite [(Fe,Ti)2O3] to cubic titano-magnetite, both the single unit cell volume and the total number of unit cells increased dramatically. The total titanium-iron oxide cell volume expanded nearly sevenfold, from 8.75 x 1022 & Aring;3 to 5.99 x 1023 & Aring;3, causing considerable pellet swelling. Conversely, the reduction of rhombohedral Fe2TiO5 to trigonal FeTiO3 resulted in a decrease in cell volume. Studying the crystalline transformation is crucial for developing effective methods to inhibit low-temperature reduction disintegration, thereby enhancing the comprehensive utilization of vanadium-titanium magnetite resources.