Study On Smelting Process Of Pre-reduced Laterite Nickel Ore

Nickel metal is one of the main raw materials for producing stainless steel.In 2018,nickel used to produce stainless steel in China accounted for about 70%of nickel output.With the rise of the electric vehicle industry in recent years,the demand for nickel metal has further increased.The main minerals for the production of nickel metal are nickel sulfide and laterite nickel ore.As nickel sulfide ore resources become increasingly dry,laterite nickel ore with abundant reserves has become the main raw material for nickel metal production,and can be roughly divided into two types:limonite and humus.Limonite-type laterite nickel ore has higher iron content,relatively higher nickel content,and lower magnesium content,and is suitable for high-pressure acid leaching.Laterite nickel ore components are mostly high-silicon and high-magnesium,with low nickel content and high wet process costs,which are suitable for RKEF processing.In this paper,a silicon-magnesium laterite nickel ore from Indonesia is used as a raw material to produce nickel-iron after smelting.X-ray diffraction(XRD),scanning electron microscope(SEM)and other detection methods were used to study the phase and mineral composition of raw ore and pre-reduced roasted ore.The results show that the complex mineral structure of laterite nickel ore gradually changes to simple ore phase at high temperature during the pre-reduction process.Nickel-iron beads were not formed in the ore during the pre-reduction process,and nickel-iron was still present in the ore phase in a relatively dispersed form.According to the content of mineral components,SiO2-CaO-MgO-Al2O3 quaternary smelting slag system is selected.The liquidus temperature diagram of the slag system was simulated and calculated using FactSage software,the range of low liquidus temperature was determined,and the range of CaO addition amount was determined.Theoretical calculation of the melting point and viscosity change of slag system after adding CaO.The theoretical calculation results show that the melting point and viscosity of the slag system are reduced after adding a certain amount of CaO.The experimental results show that the melting point and viscosity changes of the slag are basically consistent with the theoretical calculation results.Based on the composition of the raw materials,the viscosity of the slag system,the melting point,and the energy consumption required for smelting,the amount of CaO added was selected to be 15 wt%.Laboratory melting experiment results show that the optimal melting conditions are:melting time of 60 min,melting temperature of 1500℃,and the amount of flux added is 15%.Under the optimal smelting conditions,a smelting experiment was performed on a roasting ore with a carbon content of 12%.Available nickel grade is 10.93%,nickel recovery is 93.05%.Under the conditions of the best fusion experiment conditions determined in the laboratory,for this type of laterite nickel ore,a pilot scale-up test was carried out according to the optimal conditions of the fusion experiment.The optimal parameters of the smelting process were obtained:the smelting time was 30 minutes,the temperature during the smelting process was controlled at 1550℃～1650℃,the amount of CaO added was 15 wt%,and the carbon content of the pre-reduction roasting ore was 12%.An alloy with a nickel grade of 11.22%can be obtained,and the nickel recovery rate reaches 95.39%,This experimental system has studied the lateritic nickel ore smelting process and provided experimental basis for the development of a new ferronickel smelting process.