Study On Extracting Ferronickel From Laterite Ores By Electric Furnace Reduction Smelting

Owning to the rapidly development of stainless steel industry, the demand of nickel greatly increases all over the world. However, the increasingly scarcity of nickel sulphide ore resourses make the enlargement of nickel production mainly rely on nickel laterite. Laterite ores can be approximately divided into two categories: the limonite and the humus soil, which the former with low Ni content and suitable to hydrometallurgical process, especially high pressure acid leaching, and the latter with higher Ni content, its main technology is electric furnace reduction smelting.The process of reduction smelting by electric furnace was adopted to extract ferronickel alloy, which can be used to manufacture stainless steel from laterite. The effects of reductant (coke) and flux(limestone)dosage, smelting temperature and time on nickel grade and metal recovery were studied experimentally, the results showed that adding 22g coke, 22g limestone per 200g ore, smelting 50 minutes under 1550℃could obtain ferronickel alloy with 22.8% nickel grade, the metal recovery of nickel, cobalt, ferrous was 97.6%, 85.1% and 46.9%, respectively.As production materials of stainless steel, ferronickel alloys have strict requirements for harmful impurities(S, P) contents. S, P mainly comes from auxiliary materials such as coke, limestone, et al. Although extracting ferronickel from laterite ores by electric reduction smelting has been an mature technology and applied to industry for large-scale, the influence law of ores and auxiliary materials' S, P content and smelting conditions on S, P content in ferronickel alloy is still not studied yet. Therefore, the effects of coke and limestone dosage on S,P content in alloy were investigated and the effect and mechanism of slag component on sulphur and phosphorus distribution ratio (L_S, L_P ) were analyzed, thus provided theoretical basis for the production of ferronickel with low S, P content. The results showed that the contents of S and P decreased with the doseage of coke and limestone increased; L_S decreased and L_P increased with increase of FeO content in slag; both L_S and L_P increased with increase of CaO content in slag. Under the optimal smelting conditions, contents of S and P in alloy were about 0.4% and 0.05% , respectively, L_S and L_P were 0.024 and 0.145, respectively.Adopting the process of reduction smelting by electric furnace to produce ferronickel alloy has such advantages as short flow, easy-controll of the nickel grade, high metal recovery, but acidic slag goes against the desulphurization and dephosphorization, therefore it is necessary to futher refine the ferronickel alloy.