CA1059768A - Copper-nickel separation process - Google Patents
Copper-nickel separation processInfo
- Publication number
- CA1059768A CA1059768A CA246,727A CA246727A CA1059768A CA 1059768 A CA1059768 A CA 1059768A CA 246727 A CA246727 A CA 246727A CA 1059768 A CA1059768 A CA 1059768A
- Authority
- CA
- Canada
- Prior art keywords
- copper
- nickel
- melt
- slag
- flux
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Manufacture And Refinement Of Metals (AREA)
Abstract
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.
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.
Description
PC-ll29 ~L05~7~8 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-cable.
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 ~L~S~'768 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.
~05~76~3 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 lBS9768 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-ery process.
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 ~ 597168 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 ; copper.
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:
3L~5~i'6~3 BXAMPLES
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 nickel-containing scrap;
or b) inthe course of recovering copper from a nickel-containing concentrate by flash smelting and subsequent converting.
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.
~5~761~3 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 parative tests.
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.
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-cable.
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 ~L~S~'768 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.
~05~76~3 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 lBS9768 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-ery process.
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 ~ 597168 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 ; copper.
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:
3L~5~i'6~3 BXAMPLES
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 nickel-containing scrap;
or b) inthe course of recovering copper from a nickel-containing concentrate by flash smelting and subsequent converting.
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.
~5~761~3 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 parative tests.
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.
Claims (4)
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.
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 calcium oxide.
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.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB851375 | 1975-02-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1059768A true CA1059768A (en) | 1979-08-07 |
Family
ID=9853894
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA246,727A Expired CA1059768A (en) | 1975-02-28 | 1976-02-27 | Copper-nickel separation process |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1059768A (en) |
-
1976
- 1976-02-27 CA CA246,727A patent/CA1059768A/en not_active Expired
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