Thursday, 19 July 2012

Laterite Processing a Major Feature of Nickel Processing ’12

Laterite ores were the major source of early nickel, the rich laterite deposits of New Caledonia being exploited from the end of the nineteenth century. However, the discovery of the sulphide deposits of Sudbury during the early part of last century shifted the focus to sulphides.

About 73% of the world's known nickel resources are laterites found mainly in tropical areas such as Indonesia, Cuba, Columbia and New Caledonia. The remaining 27% are sulphide deposits with notable locations in Canada and Russia. Australia and Brazil have both sulphide and laterite nickel deposits.

Currently, the majority of today’s nickel is produced from sulphide deposits, as it is easier and cheaper to mine and process than lateritic ore. However, known sulphide deposits, which are large in scale and of high nickel grade, are depleting. As a result a higher proportion of future production is expected to come from laterite deposits.

Nickel laterites typically occur in regions where prolonged weathering of ultramafic rocks has occurred, favoured by warm conditions with abundant rainfall. Such deposits commonly exhibit graded layers containing a limonite layer dominated by goethite and a saprolite layer, which is usually magnesium-rich (10-20% Mg), with iron substituting for magnesium in serpentine, as well as being present as goethite.

For typical deposits, the limonitic layer is not very suited to upgrading, while some upgrading in the magnesium-rich saprolitic layer can often be applied to improve the nickel concentration, the major difference between lateritic and sulphidic ores being that the latter can be upgraded to yield high-grade concentrates. Both pyrometallurgical and hydrometallurgical processes are applied commercially to the recovery of nickel and cobalt from lateritic ores, the former mainly with saprolite and hydrometallurgy with limonitic laterites.

The importance of laterites is highlighted by the recently published technical programme for Nickel Processing ’12. The first day will concentrate solely on laterite processing, with a keynote lecture discussing the integration of pyro- and hydro-metallurgical processing techniques.

The call for abstracts is still open, so if you have anything to contribute on the processing of laterite or sulphide deposits, we would like to hear from you.

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