Insights into the Ni-Selective Carbothermal Reduction of Nickel Laterites

Abstract

In this study, a Ni-selective reduction process utilizing Ni laterites was developed to enhance the production efficiency of Fe-Ni metal. The reduction behavior of two distinct types of Ni laterites (limonite and saprolite) was investigated using high-temperature reduction experiments at 1380 °C for no more than 30 min, using coal as the reductant. The results revealed that Ni was preferentially reduced relative to Fe, achieving a maximal reduction fraction of 91% and a Ni-grade of 11–13% in the metal. A comprehensive mineralogical analysis indicated that goethite, serpentine, and silicate (Ni-, Fe-, and Mg-free) were the predominant minerals in the Ni laterites, collectively constituting over 85 mass%. The contents of these three minerals significantly influence the reduction reaction from both thermodynamic and dynamic perspectives, i.e., reduction activity of Ni and Fe in silicates and the meltability of the sample, respectively. These findings strongly suggest mixing of limonite and saprolite for Ni-selective reduction.