This invention is generally related to hydrometallurgical processes which separate the copper - as a sulphide - form the copper-containing concentrate leaving the other value- able metals in solution, usually as chlorides.

This invention is -specifically related to the degree of separation between the copper, reporting to the solids as copper sulphide, and other valuable metals, such as nickel, cobalt and zinc reporting to the solution, as chlorides.

All known methods within this area of the hydro etallurgy try to produce a clean copper sulphide and separate it as much as possible from the other valuable metals. This means in other words, they all try to get the best poss¬ ible separation in the shortest time, and without too many undesirable side reactions occurring simultaneously. We feel, to the best of our knowledge, that all the others only partly have succeeded in this task, and that there is room for improvements here.

US patent no. 3.880.653 deals with a chlorine leaching process done in an open tank with a general aim to sepa¬ rate nickel from copper in a nickel-copper matte. The pro¬ cess is controlled by the red/ox - principle. The patent describes that the ratio between the amount of chlorine gas and the matte slurry entering the open tank in cont¬ rolled by the red/ox - potential of the solution inside the tank. The method produces a coppersulphide residue which contains 13% nickel for further use. The solution is practically free of copper.

However, the degree of separation between the copper and the nickel is not complete, as some 13% nickel reports in the copper residue.

A.S. .A/S.15.000.6.84

As mentioned above, this process is controlled by the red/ox-potential of the solution inside the reaction tank. It is known by those familiar with this type of chloride- -che istry that the red/ox - potential of a solution, given as an example to 400 mV (SCE), is subject to varia¬ tions by variations in the temperature of the solution. This limited the controls of the ratio of chlorine gas to the matte slurry to having constant temperatures at all times, which may be virtually impossible in a production plant.

The red/ox - technigue as described in US patent no. 3.880.653 is further made difficult to use in an autoclave where the reaction temperature is even more difficult to control.

British patent no. 1.520.117 deals with a chlorine leach¬ ing process done in an open tank controlled by the pH- value of the solution. The ratio of the chlorine gas to the matte slurry is controlled by the pH of the solution. This pH-value has a drastic change when the elemental sul¬ phur in the leach residue is oxidized by the chlorine gas producing HCl/H-SO.. No data are given on percentages nickel in the residue, but the solution contained 10 grams copper/litre at the start.

This pH-method of controlling the ratio of chlorine gas to the matte slurry cannot be used in an autoclave .if a comp¬ lete separation between copper and nickel in a sulphide concentrate is wanted, as one essential feature in accord- - ance with our present invention is having an excess of elemental sulphur present in the residue.

US patent no. 4.260.588 deals with an exchange process, also known as a metathesis process. Copper sulphide is produced from a complex coopersulphide concentrate where elements such as zinc, lead, nickel and cobalt goes into solution. This is achieved at tempertaures greater than 180°C, preferably at 200 - 225°C in an autoclave. The

A.S.M.A/S.15.000.6.8*

process is controlled by splitting the slurry from the autoclave into two separate streams. One of these streams is leached by (oxidized) oxygen bringing some copper into solution. This oxidation (leaching) has to be adjusted to match the incoming complex concentrate slurry, and the mols of copper in solution had to match the mols of zinc, lead, nickel and cobalt brought into solution at all time. The solution from the autoclave is reported to contain 0,5 to 1,0 grams copper/litre at a red/ox potential of greater than 400 mV (SHE) which means greater than about 160 mV (SCE) .

The patent further explains that it is not important whether the copper ions in the solution inside the auto¬ clave is in the cupric- or the cupro-state. Further, that by running the autoclave at 140-180 C the residual cop¬ per in the solution from the autoclave can be completely removed by adding a large excess of concentrate. Tempera¬ tures less than 140 C was not considered relevant to use.

Further, the patent states that the solution coming from the autoclave contains only cupro-copper complexes (ions) - (which clearly a red/ox potential of 160 mV (SCE) indica¬ ted) - and if acid formation at high reaction temperatures shall be avoided, only cupro-copper-ions must be present.

This indicates that the residue inside the autoclave does not contain an excess of elemental sulphur.

However, claims no. 4, 5 and 6 in the same patent mention that it is of no relevance to the process if cupro- or cupric-copper ions, or mixtures of these, are present in the autoclave solution.

Controlling a process in accordance with this patent is for those known in this field of process operation so dif¬ ficult to do, that this is not the most advantageous method. Problems, such as acid formation, secondary copper

A.S.M. A/S. 15.000.6.84 / ϊJ ORΛ _i lT_D

sulphide precipitation or poor separation between the cop¬ per and the other metals do occur.

The present invention is a chlorine leaching done directly in the autoclave under such controlled conditions that the elements zinc, lead, nickel and cobalt go into solution and are completely separated from the copper which reports into the coppersulphide. This is no exchange reaction (metathese), but a selective chlorine leach. Using a direct chlorine leach, as in the present invention, all the above mentioned problems are eliminated.

The present invention also shows that it is very essential to have cupric-copper-ions in the autoclave solution.

The present invention also shows that it is very essential to ^' have elemental sulphur present in the copper sulphide residue in the autoclave.

The present invention also shows that by controlling the ^' autoclave chlorine leaching by the use of the concentra¬ tion of cupric-copper-ions (Cu ) in the solution, con¬ trol problems such as mentioned above, are eliminated.

The present invention also shows that by adding some oxy¬ gen to the chlorine gas, the secondary production of acid (HCl/H-SO.) is completely avoided during the autoclave leaching.

The present invention is therefore unigue in its form. It feeds a metal sulphide concentrate, a chloride solution together with a mixture of chlorine gas and oxygen gas at a ratio controlled by the /Cu / in the outco ing solu¬ tion., in such a way that the solution also contains bet¬ ween 2-100 gram/litre total copper, where 1-50 gram/litre of the total copper content is in the form of cupric chlo¬ ride ions (Cu ⁺⁺ ) . Further that the residue inside the autoclave contains at least 0,5% elemental sulphur, and the ratio between chlorine gas and the oxygen gas is

AS.M.A'S.15.000.6.84 O

ad _j usted in such a manner that the autoclave solution con ^¬ tains an essential neutral solution or up to 100 gram/ litre acid (HC1 ⁾ .

T _h e present invention is shown in the examples below.

OMPI WIPO

Example 1

A copper-sulphide concentrate containing nickel as the main impurity was treated in a 10 litre autoclave in acc- 5 ordance with this invention.

The test was devided into three parts. The first part was done without the presence of oxydized species (hereafter called Cu ) or elemental sulphur (hereafter called 0 S ) in the solution and the residue respectively inside the autoclave during the treatment at 137 C. The press¬ ure, was 1,2 bar above atmospheric pressure. The chlorine gas was injected into the autoclave at a rate till the Cu - ions just were detectable at about 0,5 grams/ 5 litre or less by continous analysis of a small part of the solution. Samples were taken every 30 minute for a total of 2,5 hours .

In the second part the temperature inside the autoclave 20 was increased to 153 C keeping all other variables con¬ stant. Samples were taken every hour for a ^' total of 3 hours.

In the third part the temperature was kept a-t 153 C, but 25 the rate of feeding chlorine gas to the autoclave was in- creased so much that the Cu -ions were detectable, and S were present in the residue. Samples were taken every 30 minute for a total of 1,5 hours.

30. The results from this test are shown in figure .1 and in table 1 below.

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Table 1 RESULTS FROM TREATING A COPPER-NICKEL SULPHIDE CONCENTRATE IN THE AUTOCLAVE USING PURE CHLORINE GAS

wt.% in residue Reaction rate

__tar_t residue _^ Cui S si Ni % Ni/hrs Part 1 53 ! 35 0,1 12 0,5 Part 2. 53 : 34 0,1 13 1,5 Part 3 - 54 37 5 9 5,0

End_residue_

Part 1 55 34 0,1 11

Part 2 58 34 0,1 8

Part 3 59 40 11 1

Solution (filtrate) grams/litre from the autoclave QL Cu ⁺⁺ Cl ^" Ni so. HC1 ^X)

Part 1 19 0,1 220 190 27 1,1 Part 2 14 0,1 213 178 30 9,5 Part 3 32 2,5 285 226 32 16,1

x) The gas injected into the autoclave was pure chlorine gas without additions of oxygen, hence the formation of HC1 and some SO, .

We can see from figure 1 and table 1 above that the pre¬ sence of Cu and S made a drastic improvement to the reaction rate (here shown as wt.% Ni removed/hour).

In addition the residue filtered very well, indicating no secondary precipitation of sulphides. _ '

Example 2

This test was done to map the importance of having elemen¬ tal sulphur (S°) present. The test was done at 150 C in the same 10 litre autoclave as mentioned in example 1. Here only the analysis of nickel and S° in the residue -- HR

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from the autoclave are shown and they are compared to the reaction rate, which is defined as:

Rate = wt% Nickel removed from the residue/time

For results, see table 2. The test was a batch test.

Table 2 RESULTS FROM CHLORINE LEACHING IN THE AUTOCLAVE. THE IMPORTANCE OF THE PRESENCE OF S°

time Rate

(hrs) wt.% Ni wt.% S° % Ni/hrs .

0 (start) 12,9 10,0

0,5 9,7 4/6 6,4

1,0 8,0 1,5 3,4

1,5 7,3 0 _. 6 1,4

2,0 6,6 0,1 1,4

We see that the rate of nickel removal decreases drasti¬ cally when the wt% S in the autoclave residue is less than 1 wt.%.

To show this even more, another test was done. Here the end product (copper sulphide residue) and the filtrate was analysed after a 2 hours continous chlorine leaching.

- Table 3 -

% Ni removed wt% S° g/1 Cu in of total in residue filtrate

Residue A 98 14 44 Residue B 73 0,2 78

Example 3

This test was done to enlighten the formation of free acid during the chlorine leaching, and how this can be control-

led by injecting oxygen gas into the chlorine gas before the gas mixture is injected into the autoclave.

The results are shown in fig. 2

The results show that by varying the oxygen content in the oxygen-chlorine gas mixture between 10 vol% and 16 vol%, the free acid formation decreases from 13 grams/litre to an approximately neutral solution.

Example 4

This test was done in a continous test in the same auto¬ clave, where all parameters in the present invention was present and tried all together.

The temperature was 135 C and the retention time was 2 hours. The gas-mixture into the autoclave was 50 vol% Cl- og 50 vol% air (resulting in about 10 vol% 0- in the gas mixture) .

The results are given in table 4 below.

Table 4 RESULTS FROM A CONTINOUS; SELECTIVE CHLORINE LEACHING OF A COPPER SULPHIDE CONCENTRATE

grams/litre

Cu Cu ⁺⁺ Cl" HC1 S__7~ F_e_ Ni Co

Solution into .1 1 57 1 50 1 72 1 autoclave

Solution out of autoclave 38 8 181 17 59 3 144 3

OMPI

wt.%

Cu S_ sl _____ Co Fe

Residue .into 50 28 0,6 10 1 2 autoclave

Residue out of autoclave 55 35 4,6 1,4 0,2 3

Cu s Ni Co ____

% of total leached 11 3 90 60 50

The results show that even at 135°C and with 2 hours retention time, the nickel was selectively leached w.r.t. copper. The residue filtered very well and had a steel- blue colour.