Method for nickel and cobalt recovery from laterite ores by reaction with concentrated acid and water leaching

Abstract

A process for leaching laterite ores containing limonite and saprolite in a two stage process. The first stage consisting of mixing and reacting the ore with concentrated mineral acid, and the second stage consisting of preparing a slurry of the acid/ore mixture in water and leaching the mixture to dissolve nickel and cobalt. Iron is efficiently separated from nickel and cobalt in the solid leach residue primarily as an oxide or hydroxide of ferric iron other than jarosite.

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] This application claims the benefit of U.S. provisional patent application No. 60 / 583243 filed Jun. 28, 2004, the disclosure of which is hereby incorporated herein by reference.FIELD OF THE INVENTION [0002] The present invention relates to the hydrometallurgical processing of nickeliferous laterite ore, and in particular to a method for acid leaching both the limonite fraction and the saprolite fraction of such ores in a single process. BACKGROUND OF THE INVENTION [0003] Laterite ores are formed by the in-situ weathering of nickel-bearing ultramafic rocks near or at the surface of the earth in tropical environments by the action of naturally acidic meteoric waters over geologic time. They consist of a variety of clay, oxide and silicate minerals, some enriched in nickel and / or cobalt, and this distinguishes them from the other major class of nickel ores, the sulfide ores. The latter consist typically of sulfide minerals of iron, nickel a...

AI Technical Summary

Benefits of technology

[0032] The present invention provides a process for the efficient leaching of nickel and cobalt from limonite and saprolite ore, such as could be produced by bulk mining of a typical nickel laterite deposit, in a two stage process, the first stage consisting of mixing and reacting the ore with concentrated

Problems solved by technology

A challenging aspect of nickel recovery from laterite ores is that the nickel values typically can not be concentrated substantially by physical means, that is, so-called ore dressing techniques, prior to chemical processing to separate the metal values.

This renders the processing of laterites expensive, and means to lower the costs of processing laterites have been sought for many decades.

Also, because of the distinct mineralogical and chemical composition of limonite and saprolite ores, these ores usually are not amenable to processing by the same process technique.

A major disadvantage of the HPAL process is that it requires sophisticated high-temperature autoclaves and associated equipment which are expensive, both to install and to maintain.

The latter proton (acid) is therefore not utilized fully for leaching and results in excess sulfuric acid which must be neutralized, for example with limestone.

Another disadvantage of the HPAL process is that it is limited to treating largely limonite-type feeds because the presence of saprolite will cause a large, and often uneconomic, increase in sulfuric acid consumption due to the leaching of magnesium from saprolite.

Disadvantages of the process are that it still requires the use of expensive autoclaves for leaching limonite, and it requires a roasting process for saprolite ore, which is expensive both in capital and operating cost terms.

However, this process still requires the use of expensive autoclaves.

While this process overcomes the disadvantages of pressure leaching, it has other disadvantages.

First, the precipitation of iron would be as a jarosite compound, which is a thermodynamically unstable compound of iron that decomposes over time to release sulfuric acid, thus causing environmental problems.

Jarosite contains two moles of sulfate for every three moles of iron and thus this compound represents substantial excess consumption of sulfuric acid to provide the necessary sulfate ions.

Second, the nickel extractions from the ore were apparently relatively low.

Fourth, there is a need to

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