INVESTIGATION OF THE SEDIMENTATION OF FENI FINE GRAINS ENTRAINED IN ERF SLAG

Nickel losses in the slag generated at Larco electric reduction furnac es (ERF) during smelting of Greek laterites account for about 20% of t he total nickel of the feed. The recovery of the nickel contained in t he slag as well as in its magnetic concentrate was studied under diffe rent methods. The experimental results have shown that a nickel recove ry in the range of 75-90% is possible by allowing the slag to settle. Washing by low carbon steel can be performed during the final stages o f the settling process as it improves the finally attained nickel reco very up to 94.4%. The simultaneous carbon reduction and settling proce ss do not favour the Ni- recovery as the produced carbon monoxide and dioxide cause boiling of the bath which promotes the flotation of the metallic grains. In all cases a reoxidation of nickel was observed aft er 20min approximately. Settling of the ferronickel grains was describ ed by a mathematical model. The model's results are in good agreement to the experimental ones for the initial 20min of the process. A modif ied model was elaborated combining the settling of the metallic grains with the nickel reoxidation reaction. This model describes with adequ ate accuracy the whole Ni- recovery process. The developed model can b e proven helpful in the design of a slag cleaning step for metal recov ery utilizing a slag settling furnace operating on line to the ERF.