Technology Of Deep Reduction-magnetic Separation About Laterite-nickel Ore

Owing to the rapid development of stainless steel industry, the demand of nickel greatly increases around the world. Nickel sulphide is the major source of nickel raw resources. Because of long-term exploition, as it was good in quality and mature in technology, nickel sulphide ore resourses is widely used. And there is no significant breakthrough in nickel sulphide exploition in recent20years. So with the crocking up of nickel sulfide over days, it becomes very necessary to research and develop laterites.Laterite ores can be approximately divided into two categories:the limonite and humus soil. The first with low Ni content and high Fe content is suitable for high pressure of acid leaching which brings serious environmental pollution. The second with lower Fe content, higher Si content, and higher Mg content, is subjected to electric furnace reduction smelting which lead to high energy consumption. A new technology called deep reduction-magnetic separation was put forward in this thesis, through deep reduction, the nickel-ferrous alloys particles was obtained from laterite and then processed by magnetic separation.In this study the raw material was provided from Burma with nickel grade of2.26%and ferrum grade of14.24%. The Mineral properties of laterite were investigated using chemical and mineral analysis, X-ray diffraction(XRD), scanning electron microscop(SEM), energy dispersive spectorscopy(EDS), thermal analysis and differential scanning calorimetry(TG-DSC). The results showed:the nickel do not exhibit independently in laterite, but exist in the crystal lattice of silicate by isomorphism, such as serpentine. The distribution rate of nickel in silicate was85.40%, the rest are existed in nickel sulphide&adsorped on matrix, so it’s difficult to us by traditional methods to enrich nickel. Owing to complex minerals composition, close paragenesis, there are water removed and crystal change. When the reduction temperature is800℃, the lattice of main minerals were damaged, begin to form new phase; hematite begin to precipitate from silicate minerals; the fusion point of nickel laterite was1359.7℃, the melting was started at1325℃.Investigation on deep reduction-magnetic separation technology of laterite-nickel ore was discussed the effect of reducing temperature, reducing time, alkanility of slag, carbon ratio, thickness of material-beds on deep reductionand magnetic separation in this thesi. It was obtained under conditions of the reduction temperature at1275℃, reduction time for50min, the carbon coefficient of2.5, material-beds thickness of20mm, nickel-iron products with nickel and iron grade of6.96%and34.74%, nickel and iron recovery of94.06%and80.44%respectively were achieved by magnetic separation after deep reduction and magnetic separation of laterite-nickel ore.Mineral properties of laterite after deep reduction were investigated using chemical analysis, X-ray diffraction, scanning electron microscop(SEM) and energy dispersive spectorscopy(EDS), it’s mechanism was also investigated thoroughly. Results show that, reduction temperature influenced the possibility of reduction, the reduction time was mainly related to the process of reduction, alkanility of slag can affect the composition of the furance slag and the move speed of the nickel and iron, these are the main effects during deep reduction. The concentrate from high-intensity magnetic separation has good qualities in nucleation, can be used as agent to stimulate nickel-ferrous alloys particles assemble and grown up, promote the process of reduction. Reduce the consumption of energy used during deep reduction. The speed of the whole reduction process was determined by the nucleation and growth of the nickel-iron crystal grain, which can be divided into3steps, namely, reduction and nucleation, reduction、coarsening of nickel-iron grain.The mechanism during deep reduction were investigated with the study on dynamics of nucleation and growth of nickel-ferrous alloys particles.This research may not only provide a new technique method for highly effective utilization of laterite ore, but make a theoretical basis for practical application.