Study On Mineralogical Characteristics And Coal - Based Reduction - Magnetic Separation Technology Of Yunnan Magnesium - Depleted Lateritic Iron Ore

The comprehensive utilization of low grade nickel oxide ores is increasingly attracting people’s attention with the declining global reserves of nickel sulfide resource. This project develops a systematic research of mineralogy and phase transformation roasted at different temperatures for low-nickel magnesium-rich oxide ores in Yunnan province. Based on the analysis of thermodynamics, coal-based reduction and magnetic separation process was studied, which provide a theoretical support for the treatments of such Yunnan low-nickel magnesium-rich oxide ores in a short process, low costs and clean production way.Mineralogical analyses show that the low-nickel magnesium-rich oxide ores consist mainly of serpentine (about 87%) and ferruginous rock (about 10%), and the minor phases are chlorite, quartz, kaolinite and smectite. The content of nickel is 0.82% and phase analysis of nickel illustrates that 80.5% of the nickel is associated with serpentine as isomorphous substitution for magnesium while the others are present as nickel oxide, nickel supplied, adsorptive nickel and isomorphous substitution for iron in iron oxide.Phase transformation of the ore roasted at different temperatures (400～1300℃) in nitrogen atmosphere were systematically characterized by TG-DSC, XRD, FT-IR, SEM-EDS and BET techniques. The results show that almost no phase transformation occurred to the sample roasted at 400℃. Lizardite and chrysotile were transformed into an amorphous crystal structure at 610℃, which brought in many cracks in of the sample. However, new magnesium silicate (forsterite and enstatite) were converted by the amorphous crystal structure at 800℃. Simultaneously, the surface area decreased.The effects of reducing temperature, reducing time and anthracite content on the process of coal-based reduction and magnetic separation were investigated by theoretical calculation and experiments. The results show that reducing temperature has the biggest impact on the phase transformation of product. The optimal conditions of the process were:reducing temperature 1250℃, reducing time 60 min and anthracite content 8%.A ferronickel with nickel grade of 2.56%, iron grade of 60.55%, and nickel and iron recovery of 15.18% and 30.45% respectively can be achieved.