Chapter 6 - Smelting of Laterite Ores to Ferronickel

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This chapter discusses industrial electric furnace laterite-to-ferronickel smelting and how smelting is controlled and optimized. The four main reactions that occur during ferronickel smelting are explained. Overall, these reactions are highly endothermic, that is, they require energy. Several ferronickel smelters are converting their power stations from fuel oil to coal. The recovery of nickel to ferronickel is between 90% and 98%. The loss of nickel is minimized by minimizing slag mass. Laterite smelting is done in electrically heated furnaces with suspended carbon electrodes. Two types of furnaces are used, either a rectangular furnace with six suspended electrodes or a circular furnace with three suspended electrodes. Great care is taken to avoid possible explosions by ensuring that water does not come into contact with molten ferronickel or slag. Great care is taken with all electrode maneuvers to avoid worker electrocution. Long-term shutdown of a furnace for major repairs and restart is accomplished by various procedures adopted. The typical life of a furnace before it needs to be re-bricked or rebuilt is10–15 years. Smelting of laterites to ferronickel in electric furnaces recovers nickel efficiently with little adverse impact on the local environment. The only disadvantage of smelting is the large amount of energy required by the electric furnaces. The last step in ferronickel production is reduction smelting of bone-dry, partially reduced nickel-rich calcine at 900 degree Celsius from the calcination/reduction kilns.

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