Reducing Roasting of Hematite Laterite Nickel Ores with the Formation of Granulated Nickel-Containing Cast Iron

Abstract

Abstract—The reducing roasting of hematite-type laterite nickel ores with flux CaCO₃ (limestone) and CaF₂ (fluorite) additions on a coal substrate in the temperature range 1350–1450°C, which causes the formation of granulated nickel-containing cast iron, is studied. The roasting time is 8–10 min without additional holding. The intense coalescence of metallic particles and the separation of metallic and slag phases is detected at 11–13% solid reducer (coke) in the presence of 7.5–12.5% CaCO₃ and 1.5–2% CaF₂ upon reducing roasting at a temperature of ≥1350°C. The yield of cast iron granules is 40–42.5% and the slag yield is 32–35% of the ore mass. 94–99% of iron and almost entire nickel are recovered into cast iron containing up 2.3% Ni and 2.1–2.5% C. The contents of the main components in the slag can change in the following ranges: 32–36% Al₂O₃, 17–24% CaO, 27–28% SiO₂, and 2.5–3.5 Fe_tot. The slag can be used as a combined flux addition for the reducing roasting of magnesia–silicate nickel ores in rotary hearth furnaces with the formation of ferronickel ball (Krupp–Renn process), which makes the technology of processing of hematite ores wasteless and economically efficient.