Factors Affecting Nickel Upgrade During Selective Grinding Of Low-Grade Limonitic Laterites

In this study wet grinding batch experiments were performed in a laboratory ball mill using laterites from Evia island, Greece, in order to determine the optimal grinding conditions for potential nickel upgrade. Selective grinding which exploits the different grindability between soft and hard minerals was considered. Kinetic models were determined based on population balance considerations for different feed and ball sizes. The efficiency of selective grinding was evaluated by taking into account breakage kinetics as well as the grade and recovery of nickel in the products. The results showed that, in general, nickel tends to concentrate in the finer fraction of -0.075 mm. In this fraction nickel recovery is increased significantly with increasing grinding times, while only a slight decrease in its grade is noticed. The results of breakage rate analysis indicate that nickel bearing phases are ground with a higher rate when shorter grinding times are used.