Effect of reductive roasting on smelting characteristics of Greek nickel laterites

Abstract

Research was undertaken to determine the effect of the reductive roasting conditions on the smelting characteristics of nickel laterite ores from three different areas of Greece—Evia, Viotia and Kastoria. The roasting experiments were performed in a rotary kiln at 800°, 860° and 900°C for 10-90 min; the smelting experiments were carried out in an electric-arc furnace that allowed the melting temperature and energy consumption to be monitored. The melting temperature values of the ore and roast samples were also determined with a LECO AF 600 instrument by enploying the Seger cones technique. The Evia samples, in which the SiO₂/Fe_tot ratio was higher than in the ores from Viotia and Kastoria, exhibited the highest melting temperatures. The lowest values were observed for the Kastoria samples owing to the presence of serpentine, which had a positive effect on their fusibility. Reductive roasting of the Evia and Viotia ore samples was beneficial for the subsequent smelting stage, but roasting of the Kastoria samples resulted in an increase in the melting temperature, possibly on account of the production of refractory oxides. Finally, in agreement with the generally accepted view that reductive roasting has a positive effect on the subsequent smelting operation, increases in the temperature and duration of roasting of a composite laterite ore sample resulted in lower energy consumption during the reductive smelting, which was attributed to fayalite formation.

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