Reaction Mechanism And Application Of Different Utilization Processes Of Low-grade Laterite Nickel Ore

A large numbers of laterite ores with the grade of 0.8wt%?1.8wt%are imported from abroad annually.According to the previous studies,selective reduction followed by magnetic separation of low-grade laterite ores is an effective method to achieve high-nickel powder ferronickel.During selective reduction,sodium or calcium salts are required as additives in order to inhibit the metallization of iron.However,adding addtives increase the amount of secondary tailings and a large quantity of iron is lost in the secondary tailings,especially in high iron-containing laterite ore treating.Meanwhile,the mechanisms for inhibiting iron reduction of additives are ambiguous.Red mud is a strong alkaline solid waste with lower comprehensive utilization rate.The large-scale utilization of the red mud is a main idea of future utilization.For above problems,three types of low-grade laterite ores were selected as the research objects,a transitional type,a limonitic type and a saprolitic type,respectively.With the transitional laterite ore as an example,the mechanisms of adding sodilum sulfate during selective reduction to obtain powder ferronickel with nickel grade exceeding 8wt%and nickel recovery exceeding 90wt%from low-grade laterite ores were deeply and systemalliy investigated.Meanwhile,co-reduction followed by magnetic separation of low-grade laterite ores and the solid waste red mud was proposed.With the limonitic laterite ore and the saprolitic laterite ore as examples,respectively,the technology and mechanism of co-reduction followed by magnetic separation with red mud were investigated.Results showed that,the mechanism of adding sodium sulfate for enhancing selective reduction of the transitional laterite ore was as follows.Two reductive reactions of the sodium sulfate happened,which resulted in weakening of the reduction atmosphere both.Most of the sulfur in the sodium sulfate was reduced to-2 valence to form troilite with iron,and a small amount of sulfur was reduced to form SO2.Sodium in the sodium sulfate reacted with serpentine to form nepheline.Besides,troilite and nepheline accelerated the nickel reduction but delayed the iron reduction.Eventually,iron metallization was controlled effectively,mainly being found in wustite and high iron-containing olivine.When the limonitic ore and the saprolitic ore were co-reduced with red mud followed by magnetic separation,respectively,the synchronous reduction and comprehensive recovery of nickel and iron in the low-grade laterite ores and iron in the red mud were realized.Finally,powder ferronickel with nickel grade exceeding 1.6wt%and iron grade exceeding 85wt%was obtained.The corresponding nickel recovery and total iron recovery were both exceeding 90wt%.The red mud had a great effect on enhancing the nickel recovery of the saprolitic laterite ore,attributing to the formation of low-melting anorthite,omphacite,and diopside during co-reduction.Meanwhile,NiO in the saprolitic ore was released.The melting phenomenon of the roasting system was obviously aggravated,enhancing the growth of the ferronickel particles.Based on the laboratory research,the process flow of producing powder ferronickel was designed and the production line of powder ferronickel was built.The selective reduction and the co-reduction with red mud followed by magnetic separation of low-grade laterite ore based on rotary kiln both were found to be feasible in industry through the industrial tests.Eventrally,the industrial application of co-reduction of low-grade laterite ore and red mud had been successfully realized.