The mineralogy of nickel laterite ores is one of the key factors in determining the choice of process flow sheet. It is commonly accepted that limonitic ores are best suited to high pressure acid leaching (HPAL) while ores from the clay and saprolite zones of the laterite profile can also be treated under atmospheric and heap leaching conditions. There is potential economic advantage from the accurate prediction of the sulphuric acid requirements to achieve optimal dissolution of nickel with a minimal level of residual free acid, at the end of the leach reaction. Such a predictive capability clearly requires knowledge of relevant ore mineralogy and for HPAL, an understanding of the impact of the leaching conditions upon the residue composition. This study has developed a general model from the mineralogical and chemical information that leads to a simple method for predicting HPAL acid requirements and is applicable to a wide range of ore types.
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