Canadian Patents Database / Patent 1059768 Summary
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|(12) Patent:||(11) CA 1059768|
|(21) Application Number:||246727|
|(54) English Title:||COPPER-NICKEL SEPARATION PROCESS|
|(54) French Title:||PROCEDE DE SEPARATION DU NICKEL EN PRESENCE DANS LE CUPRO-NICKEL|
- Bibliographic Data
- Representative Drawing
- Admin Status
- Owners on Record
|(52) Canadian Patent Classification (CPC):||
|(51) International Patent Classification (IPC):||
|(72) Inventors :||
|(73) Owners :||
|(71) Applicants :|
|(74) Associate agent:|
|(22) Filed Date:|
|(30) Availability of licence:||N/A|
|(30) Language of filing:||English|
ABSTRACT OF THE DISCLOSURE:
In order to remove nickel from a nickel-
containing copper melt while minimizing slag losses
of copper, the copper melt is blown with an oxygen-
containing gas in the presence of a slag comprising
mainly lime and iron oxide.
The embodiments of the invention in which an
inclusive property or privilege is claimed are defined
1. A process for separating copper from nickel-
containing copper alloys or mattes comprises establishing
a melt of the alloy or matte and a flux, maintaining the
melt at a temperature between 1150° and 1350°C., and
blowing the melt with an oxygen-containing gas, the flux
being selected such that a slag is obtained which is sub-
stantially silica-free and which comprises, in addition to
oxides of copper and nickel, 10-30% calcium oxide, 45-60%
iron present as oxide and up to 10% alumina, and separating
the slag from the refined melt.
2. A process as claimed in claim 1 wherein the alloy
or matte contains iron and the flux used comprises essentially
3. A process as claimed in claim 1 wherein the blowing
of the melt is carried out for a duration sufficient to ensure
that the refined melt obtained contains less than 1% nickel.
4. A process as claimed in claim 1 wherein the flux is
selected so that the silica-free slag obtained comprises,
apart from oxides of copper and nickel, 15-20% calcium oxide,
35-45% iron present as oxide and 3-6% alumina.
The present invention relates to copper-nickel
separation and in particular to the removal of nickel
from copper alloys and mattes.
One established procedure for recovering copper
from sulphide ores con~aining copper and nickel involves
the separation of the copper-containing sulphides by
mineral beneficiation techniques. Though such separations
are effective in providing a copper concentrate which
contains the bulk of the copper present in the ore, the
concentrate nevertheless contains certain amounts of nickel
which has to be separated from the copper in the subsequent
processing. It is to the further processing of such con-
centrates that the present invention is particularly appli-
The copper concentrate to be processed is usually
smelted to produce a molten matte which contains most of
the copper and nickel present in the concentrate, as well as
iron and sulphur. To conserve energy the smelting can be
carried out in a flash smelting furnace, such as described
for example in Canadian Patent 503,446. In present day practi~?,
the mol~en matte obtained from the smelter i5 oxidized in a
converter by injection of air or oxygen and addition of a
siliceous flux. It is desirable to conduct the converting
operation in such a way as to remove from the matte most
of the sulphur as gaseous oxides, and to oxidi~e into the
slag not only most of the iron, but also as much as possible
of the nickel. This is because any nickel remaining in the
blister copper which results from the converting operation
has ~o be removed during the electrorefining operations by
bleeding the electrolyte and performing the energy inten- ;
sive steps of evaporation and crystallisation of nickel
sulphate. To minimise the need for such bleeding it is
desirable to produce in the converter a blister copper
containing less than about 1% by weight of nickel. This
goal is presently achieved by extensive oxidation of the
copper matte and blister in the converter, which results
in turn in a substantial amount of copper being transferred
to the slag as oxide. For example if a blister copper
containing 0.8~ by weight of nickel is produced by present
day methods from a concentrate wherein the copper/nickel
ratio is 20, about 30% by weight of the copper in the
concentrate is oxidised into the slag during the converting
operation. In order to maximise copper recovery it becomes --
necessary to resort to expensive slag cleaning operations.
It is an object of the present invention to
provide an improved method of copper-nickel separation, -
whereby the transfer of copper to the slag per unit of
nickel eliminated during the last stages of conver~ing a
nickel-containing copper matte is minimised.
The relationship between the copper losses to
the slag and the nickel content of the blister copper
produced by the converting operation can be represented
by the equilibrium between nickel and copper present in the
metallic melt (i.e. the blister copper) and their oxides
present in the slag as follows:
Ni~bliSter) + Cu2o(slas) = 2 CU(blister) ~ NiO(slag)
The equilibrium constant which will determine the -
refining, or nickel removal, is a function of the ratio of
the activity coefficients of the oxides of nickel and copper
in the slag.
It has now been found that when lime-iron oxide
slags of a predetermined composition are used instead of
slliceous slags in the converting process, the resulting
effects on the activity coefficients of the nickel and
copper oxides are drastically different from one another.
This effect is surprising in view of the known similarity
between the chemistry of copper and that of nickel. ~s
a consequence of this effect, it is possible to carry out
the copper refining process so as to obtain a purer copper
product with much lower losses of copper to the slag.
According to the invention a process for separating
copper from nickel-containing copper alloys or mattes com-
prises establishing a melt of the alloy or matte and a flux,
maintaining the melt at a temperature between 1150 and
1350C, blowing the melt with an oxygen-containing gas, the
flux being selected such that a sla~ is obtained which is
substantially silica-free and compri~es, in addition to oxides
of copper and nickel, 10-30~ calcium oxide, ~5-60% iron
present as oxide and up to 10~ alumina, ancl ~eparatinq the
` 20 slag from the refined melt.
All percentages referred to in this specification
are percentages by weight.
It is essential to adhere to both the slag com-
position and the temperature criteria specified above in
order to achieve the benefits of the invention. Within
the temperature range speclfied, slags of the specified
composition exhibit the desirable property of extracting
a high proportion of the nickel present in the melt with
a corresponding low take-up of copper from the melt. Tem-
peratures lower than 1150C cannot be used due to the
impairment of slag fluidity, while temperatures hi~her
than 1350C result in an unacceptable reduction in the
life of the refractory in the vessel used for the refin-
The invention is particularly useful in treating
materials which are to be refined to give products con-
taining very iittle nickel, e.g., less than 1~ nickel.
Such a degree of refining when carried out on a feed
material with a copper/nickel ratio of 20 by presently used
processes which involve the use of siliceous slags, would
result in about 75% or less of the available copper report- ;
ing in the final product. In contrast the same degree of
refining can be achieved in accordance with the present
invention with a recovery of about ~7% or more of the totaI
copper present in the starting material.
Commercial lime generally contains some silica as
an impurity, and although silica is not a desirable con-
stituent of slags used in the process of the invention,
small amounts of silica can be tolerated. For this reason,
the term "suhstantially silica-free" when used herein is
intended to designate that the slag in question does not
contain more than about 5% silica.
The term "iron oxide" is used herein to designate
the general class of oxides FeOx which will be stable at
the operating conditions of the process. In practising
the process of the invention, account must be taken of the
composition o~ the material to be refined in order to
calculate the initial flux composition needed to arrive
at the desired final slag composition. Thus where, as is
common, the material to be refined contains substantial
amounts of iron, the flux composition introduced into the
refining vessel can contain little or no iron oxide since
the latter will be formed, in situ, on blowing the melt
with the oxygen-containing gas.
In the case of a material to be refined which is
low in, or free from, iron the desired slag composition
may be obtained by direct introduction of the appropriate
amounts of the constituents; alternatively iron oxide can
; be generated in situ by mixing iron or an iron-contalning
material, e.g., pyrrhotite, with the material to be refined.
~lumina is not an essential ingredient of the
slag and its presence therein will depend on the refractories
with which the molten slag comes into contact. In a similar
way magnesia though not a necessary constituent of the slag
may be present in small amounts therein, and when present
it can be said to substitute in part for the lime since lower
lime contents can be used than in its ahsence.
The treatment of the copper-nickel melt with the
specified slags may be effected in a batch mode, but it may
also be practised by causing the slag to 10w in either a
counter-current or a co-current manner over the melt as j~
would be the case in a continuous process for refining
The oxygen-containing gas used for blowing the
melt may be pure oxygen, although air or oxygen enriched
air can also be used. It may be introduced from the top
or from the side of the refining vessel in known manners.
The invention will now be further described with
reference to specific examples thereof:
A series of copper-nickel separation tests were
performed on a copper nickel alloy containing approximately
4~ by weight of nickel and about 1~ sulfur. ~his alloy
was used because it simulates a typical material obtained:
a) in the course of reclaiming copper from
or b) inthe course of recovering copper from a nickel-
containing concentrate by flash smelting and
For each of these tests a 250 g. sample of the
alloys was melted in an alumina crucible together with a
mixture of lime, iron and alumina in amounts such as to
produce 250-300 g. of a final slag containing 15-20~
calcium oxide, 35-45% iron as iron oxide and 3-6% alumina.
A gaseous mixture consisting of equal parts by
volume of nitrogen and oxygen was blown into the melt
through an alumina tube one end of which was submerged in
the melt. During the blowing the melt temperature was
maintained at 1300 - 20C. Samples of the melt and
supernatant slag were analyZed for copper and nickel after
different intervals of blowing.
By way of comparison a second series of tests
was performed using a siliceous slag as in present day
conventional practice. These tests were performed in a
similar manner to that described above on the same copper
nickel alloy. In this case the flux added to the alloy
sample consisted of iron and silica in amounts such as to
produce 250-300 g. of a final slag containing 25-35%
silica and 40-50% iron present as iron oxide.
The results obtained are shown in graphical
form in Figures 1 and 2 of the accompanying drawings.
Figure 1 depicts the copper contents of slags
corresponding to melts of various nickel contents, the
circles and curve A corresponding to the tests in accord-
; ance with the process of the invention while the inverted
triangles and curve B represent the results of the com
The lower portion of Figure 2 depicts the relation
between the percentage of the available copper lost to the
slag, which is designated : copper extraction, and the
nickel content of the copper melt. The curves C and D
correspond respectively to the results of the tests performed
; in accordance with the process of the invention and the com-parative tests. The upper portion of Figure 2 depicts the
variation of the copper e~traction tas defined above) with
the corresponding nickel extraction for the tests in accord-
ance with the process of the invention ~curve E) and the
comparative tests (curve F).
It will be seen from a comparison between the
data for processes according to the invention (curves A,
~ and E) with those for currently used processes (B, D and
F~ that the benefits of the invention are particularly
marked where a final product very low in nickel, e.g.,
containing less than 1% nickel, is sought.
While the invention has been described with
reference to preferred embodiments, it will be understood
that various modifications may be made to the embodiments
without departing from the scope of the invention, which
is defined in tlle apE~erldcd clain~s.
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