Migration Behavior of Sulfur, Manganese, and Zinc During Electric Furnace Smelting of Nickel–Cobalt Enrichments

During the reductive smelting of nickel–cobalt hydroxide enrichments, the migration behavior of typical impurities has a direct impact on the quality of crude nickel and the subsequent electrorefining process. In this study, pre-reduced calcine derived from laterite nickel–cobalt hydroxide enrichments was used as feed material, and semi-industrial smelting tests were carried out in a 40 kVA single-phase electric arc furnace. The migration and distribution behaviors of typical elements, including Ni, S, Mn, and Zn, were systematically investigated. The results show that under the conditions of pre-reduction at 900 °C and electric furnace smelting at 1550 °C, nickel is efficiently reduced, yielding crude nickel with a grade exceeding 80% and a nickel recovery of approximately 95%. During smelting, the sulfur was mainly distributed between the crude nickel and the flue gas, dust, and furnace retention, with only 1.26–1.38% of the sulfur in the charge entering the slag phase. The sulfur content in crude nickel increases with the degree of reduction, reaching a maximum of 14.84%. Manganese is mainly enriched in the slag; under moderate reducing conditions, the manganese content in crude nickel can be kept below 0.2%, while that in the slag is about 9.91%. Zinc exhibits a high volatilization rate of over 90% during reductive smelting, and by controlling an appropriate reduction depth, crude nickel with a zinc content lower than 0.1% can be obtained. Phase analysis indicates that the crude nickel is mainly composed of a nickel-based alloy phase and a hexagonal nickel sulfide (Ni3S2) phase, whereas the slag is predominantly composed of a manganese–magnesium olivine phase and a glass phase. This study elucidates the migration behavior of typical impurities during the electric furnace smelting of nickel–cobalt enrichments, providing a theoretical basis for optimizing the reductive smelting process parameters and controlling the quality of crude nickel.