Study On Preparing Ferronickel From Laterite By Roasting-Reducing Smelting Method

Nickel is mainly used for stainless steel,high temperature alloys, electroplating and chemical industry, therefore, nickel has an extremely important position in the development of national economy. About 2/3 of the nickel is used in the production of stainless steel and the cost of nickel raw material is around 70% of the austenitic stainless steel production cost.The world's nickel raw materials which is used for smelting is about 60% from nickel sulfide, and nickel sulfide account for only about 28% of the total nickel resources.So with the crocking up of nickel sulfide day and day, it's becoming very necessary to research and develop laterites.Laterite ores can be approximately divided into two categories:the limonite and the humus soil.The former with low Ni content and high Fe content which is suitable to high pressure acid leaching.The latter with lower Fe content, higher Si content and higher Mg content, which is subjected to electric furnace reduction smelting.In this study, the raw material is from abroad which is developed by a domestic company.The process of production ferronickel such as dehydrating, roasting and reduction smelting was systematically studied. Dehydration of raw material and reducing process of nickel-laterite ores were analized by DTA-TG method.Each stage of the process and reaction mechanism was also determined. The results show that when the reduction temperature is 1000℃,the water in the nickel-laterite was amostly removed; in the reduction process, some iron and nickel reduction is in solid phase, while the rest is carried out in the molten state.On this basis, reducing smelting of nickel-laterite ores roasted was investigated. Reducing agent (coke), flux, smelting temperature, smelting time on the smelting result were studied. The coke ratio,flux, smelting temperature, smelting time on the main metal recovery, nickel grade and S,P content in were determined.The results showed that coke ratio has a significant effect on smelting result and CaO is better than CaCO3 as a flux.The optimal parameters were coke proportion 11%,CaO proportion 8.3%,smelting temperature 1550℃and smelting duration 40 min. Under the optimal smelting conditions,nickel grade was 22%,recoveries of nickel and cobalt were 92.5% and 70%, respectively S and P were 0.4% and 0.05% content in the ferronickel.Adopting the process of reduction smelting to produce ferronickel alloy has such advantages as short flowsheet, 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.