Technology of Slag Formation Control in Electric Furnace Smelting of Laterite Ore

Two-thirds of the global nickel output is produced by the rotary kiln-electric furnace (RKEF) process. Due to the high contents of MgO and SiO2 and low content of iron in laterite ore, high temperature (~1600 ℃) and huge energy consumption (approximately 4000 kW⋅h/t-ferronickel) are required during the smelting step. This chapter proposes an energy-efficient technique for reducing the smelting temperature and energy consumption by controlling slag formation. The effects of various components on the melting properties of the slag were evaluated by analyzing phase diagrams, generation behaviors of the liquid phase, and viscosity of the slag. Subsequently, a comprehensive regulation of the quaternary basicity [R4 = m(CaO + MgO)/m(SiO2 + Al2O3)] and FeO content of the slag was proposed, instead of solely controlling the MgO/SiO2 mass ratio, to facilitate smelting. The high efficiency of the new method was further verified through the lab-scale, pilot-scale and industrial tests, respectively.