Promoting low-temperature consolidation of vanadium titano-magnetite pellets by high-pressure grinding roll: Mechanism of mechanical activation

The utilization of vanadium titano-magnetite concentrate (VTM) for pellet preparation poses challenges in terms of low consolidation strength and high energy consumption during the thermal process. The effect and function mechanism of high-pressure grinding roll (HPGR) pretreatment on the preparation of VTM pellets were investigated. The results indicate that HPGR pretreatment increased the strength of the pellets prepared by VTM and decreased the thermal processing temperature and time. The main reason can be attributed to the reduced particle size of VTM, accompanied by an increase in specific surface area, iron-bearing mineral liberation, and improved interfacial hydrophilicity and particle ballability. Moreover, HPGR pretreatment reduced the crystallite size of VTM and increased lattice microstrain and amorphousness, leading to a 13.21 kJ/mol improvement in the mechanical energy storage of titanomagnetite. The increased specific surface area was a crucial factor in strengthening the preparation of VTM pellets, which increased the contacting points participated in interface physicochemical reactions. The enhanced hydrophilicity and ballability were beneficial to improving the strength of green pellets, while the increased strength of roasted pellets was primarily attributed to the iron-containing mineral liberation and crystal mechanical activation, which promoted the oxidation of iron-bearing minerals and the microcrystalline diffusion and connection. Compared with the untreated VTM, the compressive strength of roasted pellets increased from 2168 N P−1 (Newton per pellet) to 2813 N P−1 when the roller pressure intensity was 12 MPa, and the proper roasting temperature could be reduced by more than 50 °C.