Influence of Calcium Chloride Addition on Coal-Based Reduction Roasting of Low-Nickel Garnierite Ore

Abstract

This work investigates the influence of calcium chloride addition on coal-based reduction roasting low-nickel garnierite ore, and which is most evident in nickel enrichment and ferronickel particles aggregation. The results demonstrate that a concentrate with 11.83% nickel, corresponding to a nickel recovery of 97.38%, was obtained when the ore was reduced at 1150℃ for 40 min in the presence of 12 mass% CaCl2·2H2O, followed by magnetic separation at 250 mT. Compared with the ore reduced without calcium chloride, the nickel enrichment ratio of the concentrate was increased from 3 to 14 by the addition of 12 mass% CaCl2·2H2O. Duing to the vaporization of the nickel chloride formed and the emergence of a new reactive surface, the addition of calcium chloride makes NiO in the garnierite easier to be reduced. The X-ray diffraction and scanning electron microscopy and energy dispersive spectrometry (SEM-EDS) studies show that metallic nickel was mainly enriched into a kamacite phase, and the presence of CaCl2·2H2O significantly accelerated the aggregation and growth of ferronickel particles, attributing to the vaporization and precipitation of nickel chloride on carbon surface together with ferrou chloride.