Classifying – separating – and assorting solids – Fluid suspension – Liquid
Patent
1996-06-25
1998-05-19
Lithgow, Thomas M.
Classifying, separating, and assorting solids
Fluid suspension
Liquid
B03D 102
Patent
active
057531048
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to the physical separation of minerals and, in particular, to the separation of minerals of different mineralogical character.
BACKGROUND OF THE INVENTION
There exists a number of non-sulphide minerals, including carbonaceous minerals (e.g graphite, carbon based residues as exist in Mt Isa, Australia ore bodies), talcose minerals (e.g talc, brucite etc which are associated with Western Australian nickel deposits and the Woodlawn, New South Wales, Australia base metal deposit) as well as amphiboles that have naturally hydrophobic surfaces.
As a result, these "gangue" minerals float readily and are very difficult to separate from other valuable minerals, notably the sulphide minerals (e.g chalcopyrite (CuFeS.sub.2), pentlandite (Ni,Fe).sub.9 S.sub.8) and sphalerite (ZnS)). When present in mineral concentrates, these "gangue" minerals often attract penalty charges at the smelter and, indeed, may be the cause of rejection of the concentrate by the smelter.
Two approaches to this problem exist in practice, namely to minimise the flotation of the non-sulphide "gangue" minerals using specific reagents or, alternatively, to encourage flotation of the "gangue" minerals in a pre-flotation step prior to the flotation of the desired minerals.
In the first approach, reagents such as depressants (guar gum, CMC, etc) or dispersants (e.g sodium silicate, etc.) are employed to minimise the flotation rate of the non-sulphidic minerals. While successful to some extent, the use of these reagents is non-specific and adversely affects the flotation behaviour of the sulphide minerals in terms of metallurgy as well as froth structure. In addition, such reagents are costly and, if it were possible, would be avoided.
Furthermore, the use of such reagents not only adversely affects flotation behaviour, it affects downstream operations such as dewatering and settling of the minerals. Additionally, and particularly with depressants, there is a requirement to add more reagent at each stage of the separation process.
In the second approach, a separate flotation system is dedicated to the recovery of the naturally floating mineral. Reagents are added to prevent the flotation of the valuable sulphide minerals, however with varying degrees of success and losses due to flotation and entrainment may occur. Inevitably, there will be at least some loss of the valuable by undesired flotation mineral with the gangue recovered from the pre-flotation system. Such losses represent an economic disincentive and would ideally be avoided.
It is therefore a first object of the present invention to provide a physical separation process for the separation of a non-sulphidic mineral from a sulphidic mineral in which losses of sulphidic mineral by uncontrolled flotation in the prefloat non-sulphidic mineral are minimised.
It is a second object of the present invention to provide a physical separation process for the separation of a non-sulphidic mineral from a sulphidic mineral in which "activation" of the sulphidic mineral and consequential loss in the non-sulphidic prefloat is avoided.
SUMMARY OF THE INVENTION
With these objects in view, the present invention provides a flotation process for the separation of a mineral of non-sulphidic character from a mineral of sulphidic character characterised in that a slurry containing a mixture of the minerals is subjected to a sequence of mineral dressing operations in which a non-oxidising gas or gas mixture and reducing agent are added in combination to the slurry to achieve an electrochemical potential conducive to the separation of the minerals by flotation.
Conveniently, the non-oxidising gas is selected from the group consisting of inert gases such as nitrogen and argon and gases such as carbon dioxide. Gases such as nitrogen and sulphur oxides e.g. sulphur dioxide, nitrogen dioxide are also included. Mixtures of these gases may also be used and the other reducing agent is preferably selected from the group consisting of ammonium sulphide, ammonium hydrosul
REFERENCES:
patent: 1505323 (1924-08-01), Eberenz
patent: 3655044 (1972-04-01), Delaney
patent: 3883421 (1975-05-01), Cutting
patent: 4011072 (1977-03-01), Holman
patent: 4288315 (1981-09-01), Morrisey
patent: 4457850 (1984-07-01), Tesmann et al.
Derwent Abstract Accession No. 87-019670/03, JP, A, 86/059183-B (Dowa Mining Co. Ltd.) Dec. 15, 1986.
Hoecker Walter
Newell Andrew
BOC Gases Australia Limited
Lithgow Thomas M.
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