Behavior and mechanism of pre-oxidation improvement on fluidization in the fluidized reduction of titanomagnetite

The direct reduction process is an important development direction of low-carbon iron-making and efficient comprehensive utilization of poly-metallic iron ore, such as titanomagnetite. However, the defluidization of reduced iron particles with a high metallization degree at a high temperature will seriously affect the operation of fluidized bed reduction. Coupling the pre-oxidation enhancing reduction and the particle surface modification of titanomagnetite, the behavior and mechanism of pre-oxidation improvement on fluidization in the fluidized bed reduction of titanomagnetite are systematically studied in this paper. Pre-oxidation treatment of titanomagnetite can significantly lower the critical stable reduction fluidization gas velocity to 0.17 m/s while achieving a metallization degree > 90%, which is reduced by 56% compared to the critical gas velocity of titanomagnetite without pre-oxidation. Corresponding to the different reduction fluidization behaviors, three pre-oxidation operation regions have been divided, taking oxidation degrees 26% and 86% as the boundaries. Focusing on the particle surface morphology evolution in the pre-oxidation – reduction process, the relationship between the surface morphology of pre-oxidized ore and reduced iron with fluidization properties is built. The improving method of pre-oxidation on the reduction fluidization provides a novel approach to prevent defluidization by particle surface modification, especially for the fluidized bed reduction of poly-metallic iron ore.