Nickel processing (united States patent 5211745)

Description:

Thus, the present invention also provides a method of processing nickel sulphide concentrates, said method comprising extracting rock from a nickel ore body, subjecting the extracted rock to normal beneficiation processes, said beneficiation processes including crushing, grinding, flotation and thickening, to produce a nickel sulphide flotation concentrate, and subjecting the nickel sulphide flotation concentrate to an acid leach using sulphuric acid in order to dissolve substantially all of the acid soluble magnesium bearing minerals contained therein to provide an upgraded nickel concentrate residue and a leach solution.

Of course, the present invention also provides a method of processing nickel iron oxide calcine produced after roasting of an upgraded nickel concentrate residue, said method comprising subjecting the nickel iron oxide calcine to an acid leach with sulphuric acid, the upgraded calcine residue providing a calcine having a higher nickel concentration and a lower MgO/SiO 2 concentration than the feed nickel iron oxide calcine.

Depending upon the characteristics and composition of the intermediate nickel-bearing products, the leach solution may also contain economic levels of valuable base metals, including minor levels of nickel. While such dissolution of base metals may be minimised by use of lower acid strengths and/or minimum excess acid conditions, the present invention may be adapted to include the additional step of subjecting the separated leach solution to known methods to recover the dissolved nickel and valuable base metals.

This may include oxidation of the contained iron, together with selective precipitation of valuable base metals via pH adjustment with lime or other suitable bases to raise the pH to the region of 5 to 6 to precipitate, in particular, dissolved iron. Alternatively, the valuable base metals may be recovered via cementation on iron or other suitable metals, via sulphide precipitation, or via solvent extraction. Furthermore, in relation to the calcine leach, dissolved magnesium remains in solution as long as the pH is kept below that required for its precipitation (approximately pH9). Dissolved silica will also remain in solution at these levels.

As indicated above, the dissolution of the valuable base metals and the minor levels of nickel during the acid leach may be minimised by the use of comparatively lower acid strengths and/or minimum excess acid conditions. In practical terms, these minimum acid conditions are always preferred in order to reduce acid costs. The maximum utilisation of acid is enhanced by the use of extended leach times.

The two aspects of the present invention will now be illustrated by examples. The first example relates to the acid leach of the flotation concentrates while the second example relates to the acid leach of the calcine.

The first aspect of the present invention may be illustrated by reference to the first example where nickel sulphide flotation concentrates from the Yakabindie nickel deposit were subjected to an acid leach with sulphuric acid. The minerals providing the nickel in these deposits include pentlandite, violarite, nickeliforous pyrrhotite, millerite and heazelwoodite. The extracted rock is subjected to a normal beneficiation process, which comprises crushing, grinding, flotation and thickening, to produce the nickel sulphide flotation concentrate. It should be understood that the generality of the invention as described above is not to be limited due to reference to the following specific examples.

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