Process mineralogy for the physical beneficiation of a low-grade nickel laterite bearing ore

Abstract

Nickel is one of the world's most important base metals with a widespread use in numerous industrial processes accounting to a consumption of about 2 million tons yearly. Ni sources include sulphide ore with average grade of 2 wt % and laterite ores with average grade of 0.4 wt%, 60% of the worlds nickel production is from the sulphide ores which constitute 30 % of the world’s reserves and Ni laterite ores contain about 70 % of the worlds nickel reserves and contributes approximately 40 % towards nickel production. The depletion of high-grade Ni sulphide ores has led to the exploration of low-grade Ni laterite ores as an alternative source for nickel production. Liberation and beneficiation of from laterite ores requires an understanding of the ore mineralogy so as to establish the liberation particle size and suitable beneficiation method. In sulphide ores, nickel is concentrated in sulphide minerals that can be beneficiated using conventional metallurgical methods, however in laterite ores nickel is finely disseminated in silicate and oxide minerals thus making liberation and processing by conventional methods it difficult.

In this study, a nickel bearing silicate ore was studied for nickel beneficiation. XRD and bulk modal analysis showed that the ore contained silicate minerals, amphibole (40.34 %), chlorite (30.43 %), talc (11.52 %), quartz (8.76 %) and plagioclase (5.6 %). Ni deportment analysis by EPMA and QEMSCAN showed that the nickel is present in two particular silicate minerals, amphibole and chlorite. Grain size analysis on the ore showed that amphibole had a coarser average grain size than chlorite. Liberation analysis shows that amphibole is less liberated than chlorite, with the percentages of fully liberated particles being 36.21 % and 48.29 %, respectively.

The head sample was crushed and ground to produce three size fractions of -212 μm +125 μm, -125 μm +75 μm, and -75 μm. The three size fractions were classified using the Falcon Concentrator. The effect of G-force was studied at 30 G, 45 G and 60 G, the effect of percentage solids at 10 %S, 20 %S and 30 %S, and the effect of both G-force and percentage solids at 10%S - 30 G, 20 %S- 45 G and 30 %S - 60 G. Samples collected from the falcon concentration test were dried and prepared for mineralogical and chemical analysis.

The optimum conditions for the physical beneficiation of the ore were observed at a size fraction of -75 μm at 10 %S and speed rotation G-force of 30 G, the mass distribution to the underflow and overflow points were obtained at 63.25 % UF and 36.75 % OF, respectively. The reprocessing of the -75 μm underflow material was conducted to recover more mass to the overflow.

The optimum conditions for the physical beneficiation of the ore were observed at a size fraction of -75 μm at 10 %S and speed rotation G-force of 30 G, the mass distribution to the underflow and overflow points were obtained at 63.25 % UF and 36.75 % OF, respectively. The reprocessing of the -75 μm underflow material was conducted to recover more mass to the overflow.