Preparation of high-grade ferronickel from low-grade nickel laterite by self-reduction and selective oxidation with CO2-CO gas

Abstract

The known resources of nickel sulfide ores are quickly diminishing; to satisfy future nickel demands, nickel laterite deposits are now being investigated as an alternative. The use of classic mineral processing techniques to economically extract nickel and prepare high-grade ferronickel from low-grade nickel laterite entails numerous challenges. In this study, we developed a new reduction and selective oxidation process for nickel laterite to separate metallic iron from ferronickel in reduced laterite and produce a higher-grade ferronickel, as compared with current techniques. The thermodynamics of the oxidation of metallic nickel and iron in CO2-CO gas mixtures were investigated, and the self-reduction and selective oxidation of nickel laterite with CO2-CO gas mixtures were examined. We found that ferronickel with a nickel grade of 37.2 wt% could be obtained at a nickel recovery of 95.89% when nickel laterite was reduced at 1200 °C for 25 min, followed by oxidation with CO2 at a concentration of 70 vol% at 1100 °C for 50 min. Therefore, the process proposed here is an effective means of deriving high-grade ferronickel from low-grade nickel laterite whilst using CO2 efficiently.