Abstract
The pressure oxidation of low-grade nickel sulfide concentrate with high iron sulfides content generates significant amounts of sulfuric acid that must be neutralized. This acid can be utilized to leach metal values from ores such as nickel laterites. The present study demonstrates the use of a low-grade nickel concentrate generated from Poseidon Nickel Mt Windarra ore to enable additional nickel and cobalt extraction from a Bulong Nickel Operation nickel laterite blend. The co-processing of these materials at 250 °C, with oxygen overpressure, using total pulp densities of 30% or 40% w/w, and a range of nickel concentrate to nickel laterite mass ratios between 0.30–0.53, yielded base metal extractions of 95% or greater. The final free acid range was between 21.5–58.5 g/L, which indicates that enough in situ sulfuric acid was generated during co-processing. The acid was shown from mineralogical analysis to be efficiently utilized to dissolve the laterite ore, which indicates that the primary iron hydrolysis product was hematite, while the aluminum-rich sodium alunite/jarosite phase that formed hosts approximately 5% of the hydrolyzed iron.
Highlights
The processing of nickel laterites by high pressure acid leaching (HPAL) typically uses feeds with an average nickel content not less than 1.1%–1.2% [1] though recently several nickel laterite projects have been revalued with lower nickel cut-off grades based upon the cobalt content of the ore
The co-processing of a low-grade nickel concentrate with blended Bulong nickel laterite ore was demonstrated to be effective for the extraction of nickel and cobalt at 250 ◦ C using total pulp densities of 30% w/w and 40% w/w over a range of nickel concentrate to nickel laterite mass ratios between 0.30 and 0.53
Do these enable in situ sulfuric acid generation but the nickel and cobalt contents of the relevant minerals, typically pyrrhotite and/or pyrite. can be accessed; The low-grade nickel concentrate employed in this study had enough acid generating capacity to leach the nickel laterite ore without the need to provide supplementary acid;
Summary
The processing of nickel laterites by high pressure acid leaching (HPAL) typically uses feeds with an average nickel content not less than 1.1%–1.2% (cut-off grade 1.0%) [1] though recently several nickel laterite projects have been revalued with lower nickel cut-off grades based upon the cobalt content of the ore. There have been few scientific studies on this topic [3,7], in addition to a handful of patent applications [8,9,10,11,12,13] This is presumably because sulfur burning to generate sulfuric acid for nickel laterite leaching is well established, while the reliable sourcing of a suitable, readily accessible, consistent grade sulfidic ore/concentrate source may be problematic. The pilot scale study of Quinn et al [3] employed 70:30 nickel laterite/sulfide blends having low nickel (1.24%–1.63%) and sulfide (3.2%) contents milled in previously generated heap leach liquor These blends were leached at 220 ◦ C using 800–1000 kPa oxygen overpressure and supplementary sulfuric acid addition of 150 kg/t blended ore. Extraction performance and changes in the mineralogical composition was obtained
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