The Influence And Mechanism Of Laterite Nickel Ore Types On Its Direct Reduction-magnetic Separation

Extracting nickel from laterite nickel ore by direct reduction-magnetic separation process has gotten more attention and achieved greater progress in recent years, providing a new way for the utilization of nickel resources. However, the metallogenic regularity of laterite nickel ore is so complex that different laterite nickel ores may need completely different process conditions. Therefore, systematic studies on the influence and mechanism of ore types on its direct reduction-magnetic separation process are of great significance.Ferruginous, femic and magnesian laterite nickel ore of three industrial types were selected as the research object in this paper. The differences of direct reduction-magnetic separation process between the three samples were compared, and the effect of the ore types on direct reduction process was studied. It was found that nickel in ferruginous laterite ore is easy to recover without additives, but it is difficult to obtain nickalloy with high nickel grade. Compared with ferruginous laterite ore, nickel in femic laterite nickel ore is difficult to recover and nickel in magnesian laterite ore is more difficult to recover. The nickel recovery and grade of these two samples are unsatisfactory.To solve the above problems, different samples need different additives. Sodium sulfate is applicable to ferruginous laterite ore but not suitable for magnesia and femic laterite ore. On the contrary, calcium fluoride is applicable to magnesia and femic laterite ore but not suitable for ferruginous laterite ore. Under conditions of roasting temperature at 1200℃, roasting time for 50 min, coal dosage of 6%, ferruginous sample can obtain nickalloy containing 10.53% nickel with the nickel recovery of 86.17% when 9% sodium sulfate was added. Femic and magnesia sample sample can respectively obtain nickalloy containing 9.66%, 8.67% nickel with the nickel recovery of 84.82%,81.14% when 9% calcium fluoride was added.X-ray diffraction (XRD) and electron scanning electron microscopy and energy spectrum analysis (SEM-EDS) were used to analyse the mechanism of the difference between three samples’direct reduction process. It was found that the laterite nickel ore types have great influence on metal particles size in the roasted ore, but little influence on the nickel reduction. From ferruginous laterite nickel ore to magnesian laterite nickel ore, the metal particles size become smaller making them difficult to rocover in magnetic separation; The iron content in laterite nickel ore is the important factor affecting the effects of sodium sulfate and calcium fluoride. Sodium sulfate can obviously inhibit the reduction of iron ore, and has a good effect on ferruginous laterite nickel ore. But, when sodium sulfate is added into the laterite nickel ore with lower iron content, Fe-Ni-S will be generated and makes the nickel recovery rate lower. Calcium fluoride can obviously promote the nickel iron particles to grow up, so it has a good effect on femic and magnesian laterite nickel ore. But, calcium fluoride cannot be used on ferruginous laterite nickel ore because of the lack of capabilities to inhibit the reduction of iron minerals.