Effect of Temperature on FeNi Particle Growth During Thermal Treatment of Ultramafic Ni Concentrates

The depletion of the high-grade Ni sulfide ores has resulted in efforts aimed at processing the alternative low-grade ultramafic ores. However, these ultramafic ores contain considerable MgO, silica, and gangue rocks, challenging their processing. Smelting has been predominantly used for Ni extraction from sulfide ores as hydrometallurgical methods are associated with vast chemical usage and wastewater. However, high smelting temperatures (>1300 °C), refractory corrosion, and significant emissions remain the main smelting drawbacks. Thus, we explored the thermal treatment (<1000 °C) of the ultramafic Ni concentrates blended with Fe additive as a promising approach with mild processing conditions for upgrading these concentrates. The heat-treated product primarily comprises a magnetic FeNi alloy and a non-magnetic gangue suitable for subsequent physical separation. However, the formed FeNi particles are fine and dispersed in the gangue, lowering magnetic separation efficiency. Thus, adequate growth of the FeNi particles is imperative to guarantee their effective separation from the gangue. This work systematically investigated the effect of various heating temperatures to decipher its impact on FeNi particle growth.