Oxidation behaviour of violarite-based nickel concentrate in simulated suspension smelting conditions

A single-particle laminar-flow furnace was used to study the oxidation of a violarite- and pyrite-containing nickel concentrate from the Forrestania mine, Australia. The composition of the reaction gas varied from N₂ to N₂ + 75 vol% O₂ and the gas preheating temperatures ranged from 500 to 1100°C. The degree of oxidation of the material was established through chemical analysis. Optical and scanning electron microscopy were used to determine the morphology and mineralogy of the oxidation products. The concentrate studied was found to be very reactive, and it ignited at ≤500°C. Total desulphurization of this nickel concentrate was observed at 900°C with 50 vol% oxygen in the reaction gas. The microscopical examinations showed that oxidation started with the formation of a porous oxide rim, after which oxidation proceeded either via grain growth of a two-phase structure or via preferential oxidation of the outer layer - both resulting in the formation of oxide crust. Moreover, particles were found to fragment by several different mechanisms.