Nickel Ore Reduction by Hydrogen and Carbon Monoxide Containing Gases

Roasted calcine of a sulphidic nickel-iron ore and nickeliferous laterite ore were reduced in a horizontal tube furnace and in a laboratory scale fluidised bed reactor. Hydrogen, carbon monoxide and their mixtures were used as reducing gases. The possibility for selective reduction of nickel oxide to metallic nickel with minor formation of metallic iron was studied by adding a controlled amount of CO2 or H2O in the reducing gas. The results showed prominent enrichment of nickel in the final product as compared with the starting material. However, pure nickel could not be produced by "selective" reduction, i.e. the product was ferronickel, the grade of which depended on the feed material and the experimental conditions. A two step process for pyrometallurgical nickel-ferronickel production is proposed. In the first step a part of nickel is selectively reduced at minimum reduction potential and at a low temperature to avoid iron reduction and dissolution into the nickel. After separation of the nickel metal product the rest of the nickel is co-reduced with iron oxide to form ferronickel and to assure a high total yield of nickel. Comparison with conventional nickel pyrometallurgy shows remarkable energy savings.