Study of mixing saprolite with limonite in selective reduction process

Selective reduction of nickel laterite is a pyrometallurgical process using slightly lower temperatures (1100-1200°C) than conventional smelting technology, such as blast furnaces and rotary kiln electric arc furnaces. It is followed by the physical upgrading using a magnetic separation process to deliberate ferronickel from the impurities. In addition, the additive of sodium sulfate is added to increase the nickel recovery. Limiting the addition of reductant can also be carried out to reduce the metallization of iron, thus increasing the nickel grade in ferronickel. Nevertheless, its low nickel recovery due to ferronickel's small particle size is still a significant problem in this selective reduction process for saprolitic nickel ore at low-temperature. In this work, the effect of the mixture of saprolite and limonite in the reduction process on the particle growth of ferronickel will be investigated clearly. The nickel laterite was reduced in a muffle furnace at 1150°C for 60 minutes, followed by a wet magnetic separation process using 500 Gauss of a magnetic field. The XRF was used to identify the iron and nickel in the concentrate and tailings, while the XRD and SEM-EDS were used to analyze the phase transformation along the reduction process and microstructure of the reduced ore. The results showed that the optimal process for limonite and saprolite was generated by adding 0.2 stoichiometry reductant. In the saprolite reduction process, ferronickel's nickel grade is higher, but the recovery is lower than limonite. Mixing saprolite with limonite increased the ferronickel particle size, increasing nickel recovery. Nevertheless, the nickel grade in ferronickel decreased.