FI119819B - Method for improving the quality of copper concentrate - Google Patents

Description

119819

METHOD FOR IMPROVING THE QUALITY OF COPPER CONCENTRATION FIELD OF THE INVENTION

The invention relates to a process for preparing a copper concentrate suitable for pyrometallurgical processing from a concentrate containing zinc as an impurity. According to the method, the zinc is dissolved from the concentrate in a solution containing sulfuric acid under oxidizing conditions at atmospheric temperature and pressure. At the end of the leaching, the conditions are adjusted so that any dissolved copper is precipitated.

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BACKGROUND OF THE INVENTION

Complex copper sulphide concentrates contain not only copper but also other non-ferrous metals such as zinc. When sulfide concentrate for pyrometallurgical copper recovery, for example, contains zinc, it complicates 15 processes. In the pyrometallurgical process, the zinc contained in the concentrate evaporates and enters the fly as zinc oxide, from which it must be recovered separately. Today, smelters charge fines for concentrate impurities, for example, the concentration of zinc in the copper concentrate must be less than 3%.

• j * 20 There are several known prior art methods for separating zinc from copper concentrate, s V: The use of selective foaming for separation is described in very many

*: in patent publications such as US 4,279,867, JP 59 160558 and RU

2135298. However, the mineralogy of the ore is sometimes such that, even with selective flotation, * * ·· does not produce good results.

• · «• * 25

Another way is to first treat the concentrate at a temperature such that: •: *** the zinc is evaporated and recovered as zinc oxide, after which ···: ···: the copper concentrate can be further processed as desired. Such has been described e.g.

: T: in CN 1288966. If the concentrate is to be further processed on a pyrometallurgical basis, the process requires the construction of two furnace units. A further disadvantage is the formation of sulfur dioxide, which requires its own * treatment equipment.

U.S. Patent No. 4,260,588 to U.S. Patent No. 2,119,819 discloses a method for treating complex copper sulphide concentrate for upgrading. In it, the concentrate is dissolved in a solution of copper chloride at elevated temperature and. s at a pH of about 3. The leaching results in the recovery of the sulfide concentrate containing copper and iron and other non-ferrous metals such as zinc, nickel and cobalt in the complex concentrate. The method seems rather complicated and expensive. It may also be a disadvantage that the chloride must be carefully removed from the concentrate so that they do not cause problems in the further processing of the concentrate.

PURPOSE OF THE INVENTION

It is an object of the invention to provide a process for improving the quality of a zinc-containing copper sulphide concentrate by removing zinc from the concentrate so that the concentrate is well suited for the pyrometallurgical recovery of copper.

SUMMARY OF THE INVENTION

The invention relates to a process for improving the quality of a zinc-containing copper sulphide concentrate by removing zinc from the concentrate so that the concentrate is well suited for pyrometallurgical recovery of copper. The process is characterized in that the zinc is removed from the concentrate by dissolving the concentrate in a sulfuric acid solution: at atmospheric pressure and temperature, initially under oxidizing conditions and before completion of the dissolution, a reductant is introduced to precipitate dissolved copper.

• 1 2 3 · ϊ Ϊ 25

The process according to the invention is characterized in that at the end of the leaching step, the sulfuric acid content is adjusted to a range of 0 to 100 g / l, preferably 5 to 25 g / l.

It is also typical of the process according to the invention that the oxidant is supplied to the dissolution 1.

• · • · • ·· M • · 2 • · 3 3 119819

According to one embodiment of the invention, the oxidant used is a gas which is at least one of air, oxygen-enriched air and oxygen.

According to another embodiment of the invention, at least one of hydrogen peroxide, manganese dioxide and potassium permanganate is used as the oxidizing agent.

It is also typical of the process of the invention that the redox potential is adjusted such that at the beginning of the leaching there is at least 10 mg / l of copper in the solution and at the end of the leaching there is no copper in the solution.

According to one embodiment of the invention, the reducing agent to be delivered to the end of the leaching step is a reducing gas. The gas is typically hydrogen sulphide.

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According to another embodiment of the invention, the reducing agent to be carried out at the end of the dissolution step is sodium hydrogen sulfide or sodium sulfide.

According to yet another embodiment of the invention, the reductant to be completed at the end of the leaching step is: copper sulphide concentrate I ··· · · · · *

It is typical of the process according to the invention that at the beginning of the leaching the solution contains at least 0.1 g / l of iron and at least 10 mg / l of copper.

The essential features of the invention will be apparent from the appended claims.

• · • · • ··· · · ·

DETAILED DESCRIPTION OF THE INVENTION

: T: In the process of the invention, the zinc-containing copper sulphide concentrate is led to a leaching process, the purpose of which is to dissolve the concentrate in an amount of zinc that is suitable for pyrometallurgical treatment. The leaching is sulfate based and occurs under atmospheric conditions.

4, 119819

Atmospheric conditions refer to leaching that occurs in pressureless reactors and at temperatures up to 105 ° C. The copper sulfide concentrate is mainly copper primary sulfide, such as calcopyrite, and is essentially free of secondary sulfides. Chalcopyrite is not substantially soluble under conditions where zinc is dissolved from the concentrate.

The zinc-containing copper sulphide concentrate is introduced into a solution containing sulfuric acid, wherein the acid content is adjusted at the end of the leaching to be in the range 0-100 g / l, and preferably 5-25 g / l. In the initial stage of dissolution, the oxidant is introduced into the solution, for example an oxidizing gas such as air, oxygenated air or oxygen. The oxidizing agent may also be other than a gas such as hydrogen peroxide, potassium permanganate or manganese oxide.

It is also advantageous for leaching that the acidic solution contains a small amount of dissolved iron as well as copper. A sufficient amount of iron causes the zinc to dissolve at a sufficient rate, i.e. it improves the dissolution kinetics. Preferably the iron is at least 0.1 g / l, typically more than 5 g / l.

The solution contains at least 10 mg / l of copper. Copper in the solution catalyzes the oxidation of iron. Oxidized iron participates in the dissolution of zinc according to the reaction (2) below: · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·

ZnS + Fe2 (S04) 3 ZnS04 + 2FeS04 + S (2) · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · However, dissolution of copper is not a problem since it is precipitated back at the end of leaching.

The redox potential of the leachate is adjusted so that at the beginning of the leaching there is at least 10 mg / l of copper in the solution and at the end of the leaching there is no copper in the solution.

··· • · • · · «· 5 119819

It is essential for the selective leaching process of the invention that the course of leaching is monitored such that the acid content of the leachate at the end of leaching is adjusted to the desired range. At the same time, the amount of oxidizing agent required to dissolve the zinc is determined and fed to the leaching reactor at the initial leaching stage. Preferably, the leaching reactor is a mixing reactor. Once the required amount of oxidant has been fed, the reactions continue even though the oxidant feed has been stopped. When the zinc content of the concentrate has dropped to the desired level, some of the copper may also have dissolved. At the end of the leaching, dissolved copper is precipitated with a reducing agent. The reducing agent may be a solid, liquid or gaseous such as hydrogen sulphide. Other reducing agents include, for example, sodium hydrogen sulfide NaHS, sodium sulfide Na2S or the copper sulfide concentrate itself, which acts as a slow reducing agent. The leaching results in a copper concentrate having a zinc content that is suitably low for the pyrometallurgical treatment of the concentrate. The zinc sulfate solution is treated as desired to prepare a commercial product.

Under process conditions, the total time and cost of leaching is sought to be at the most economically viable level. This takes into account the slow dissolution time required by the 20 reducing agents and the potentially higher cost and reagent consumption of the fast reducing agent (· ·: time vs. reagent consumption).

EXAMPLE 25 Example 1

The copper sulphide concentrate was dissolved in a 10 L reactor. The concentrate: * ·· consisted of the following minerals: CuFeS2, FeS2, ZnS. The grain size of the concentrate was ··· d0.5 = 10 µm and do.9 = 35 µm. The concentrate had the following composition: 30 ·· * • · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·

Table 1 ~ Cu I Zn I Fe Pb S ZnVeemuk.

~%%%%%% 18.4 7.3 28.4 1.5 40.0 2.3

The leaching was carried out at atmospheric pressure and at 95 ° C for 9 hours. The solution contained 9.6 g / l of ferric iron and 1 g / l of copper. Solution 5 had a solids content of 200 g / l and at the start of leaching the solution had a hbSCV concentration of 50.8 g / l. The oxygen containing gas was oxygen, which was fed to the reactor for 3 hours and then stopped. Fresh concentrate was used for reduction, which was fed to the reactor at 1.1 kg 6 to 7 hours after the start of the experiment. As shown in Table 2 below, the concentration of zinc in the concentrate had fallen to 1.4% and the copper content to 21.4%. According to the balance sheet, the amount of copper lost in leaching was less than 10%.

The results show that the concentrate acts as a slow reducing agent, and if the leaching were continued, the copper would gradually be precipitated back. However, concentrate is undoubtedly the most preferred reducing agent if it is possible to carry out the reduction over a long period of time. Redox potential is measured on the Pt electrode of the Ag / AgCl electrode. with.

• · · • · · 1 • · 1 • · · .1 · Table 2 20 • · · f ............ j "........... .I - ........ '....... "" __Solute___Wealth

· 1 · .. Time ~~ Fe ° 1 | Cu 1 Fe21! Zn HaSoJ Redox Cu Fe Pb Zn S

. ···. hg / lg / lg / lg / lg / l mV%%%%% 0 0.53 1.0 9.6 0.0 50.8 412 18.4 28.4 1.5 7.3 40.0 1 0.90 4.9 13.6 9.4 29.3 424 20.0 31.6 2.0 3.3 44.6 f1 ·· 3 2.58 8.4 16.5 12.1 14.2 433 18.3 31.3 2.6 1.5 46.8 5.5 1.19 7.8 17.2 13.4 15.8 401 19.4 32.3 1.7 1.0 46.0! 1! 9 0.82 4.3 18.5 19 32 396 21.4 31.9 1.9 1.4 46.1 • · · • »i • ♦ 1 • • • • • • • • • 1 119819

Example 2

In the experiment, the composition of the dissolved concentrate was the same as in Example 1, as well as the leaching reactor, leaching pressure and temperature. The solubilization time was 11 h. The solution contained 52.5 g / l sulfuric acid, Θ.8 g / l ferric iron and 1.1 g / l copper. After 1h, the solution was deoxidized and hydrogen sulphide was introduced as the reducing gas between 10 and 11 h. The zinc content of the concentrate had fallen to 1.0% and the copper content had increased to 20.6%. The reduction precipitated all dissolved copper so no copper losses occurred. The flow of lysis is shown in Table 3: 10

Table 3 shows that upon completion of oxidation, the redox potential rapidly decreased from 406 mV to 390 mV. Prior to the supply of the reducing agent, the value was 330 mV and rapidly decreased after the supply of the reducing agent to 86 mV. The last value, 207 mV, indicates the 15 oxygen that is likely to come with the replacement water. it can also be deduced from the table that a lower supply of reducing gas would have been sufficient since dissolved copper precipitated immediately after the introduction of the reducing gas.

Table 3__ tit__Solution ___Concentrate

»• f Time Fe3 * Cu Fea + 1 Zn | h2S0J Redox Cu 1 Fe I Pb I Zn 1 S

: Λ: hg / lg / lg / lg / lg / l mV%%%%% 0 0.4 1.1 9.8 0.0 52.5 510 18.4 28.4 1.5 7.3 40.0 1.0 0.6 4.2 14.1 11.0 48.5 406 19.6 30.3 1.6 2.3 46.3 !:; ** 2.0 0.3 3.4 15.0 12.2 42.0 390 20.4 30.2 1.7 2.1 46.2: ** 3.0 0.3 2.9 15.5 12.9 44.0 386 20.4 30.0 1.7 1.7 44.6 »·· ............. Ml ...... ... ...... .............'.............

4.0 0.3 2.4 15.6 13.2 47.0 383_______ 5.0 0.3 1.8 16.1 13.9 44.3 384______ 6.0 0.3 1.5 16.7 14.5 44.8 383 21.3 29.3 1.3 1.2 46.1 • · ι —-- 8.0 0.4 0.4 16.7 14.5 46.0 370 21.8 29.3 1.4 1.0 46.6 '* "* 10.0 0.1 0.03 16.4 14.3 43.7 330 22.1 29.5 1.5 1.0 44.7 10.2 0.03 0.001 16.5 14.4__J36 ______ 10.5 0.03 0.001 16.6 14.3__97 ______ * / ** 11.0 0.03 10.001114.9112.71 40.7 | 207 | 20.6 | 30.11 1.5 | 1.0 | 47Λ 20 • · e · • · e ·· 8 119819

Example 3

The composition of the concentrate dissolved in the experiment was as shown in Table 4.

Table 4

Cu I Zn I Fe I Pb I S Znve8muk.

%%%%%% 18.5 10.0 27.1 1.4 40.0 Ö2 5

The leaching reactor, leaching pressure and temperature were the same as in Examples 1 and 2. The leaching time was 12 h. The solution initially contained 51.4 g / l sulfuric acid, 9.1 g / l ferric iron and 0.9 g / l copper. The solution was stopped after 4h and hydrogen sulphide was supplied as a reducing gas between 11.5 and 12h. The zinc content of the ίο concentrate had fallen to 1.4% and the copper content to 21.7%. The reduction precipitated all dissolved copper so no copper losses occurred. The flow of leaching is shown in Table 5:

Table 5___ ___ Solution__Concentrate

Aika Fe31 Cu Fe21 Zn H2S04 Redox Cu Fe Pb Zn S

h g / l g / l g / l g / l g / l mV% __%%% __% _ 0 0.4 0.9 9.5 0.0 51.4 361 18.5 27.1 1.4 10.0 40.0 ·; ·; 1 0.3 1.3 10.3 6.7 36.7 409 19.6 29.0 1.4 7.3 43.0 2 0.4 2.0 10.6 10.4 27.8 412 19.8 29.9 1.5 5.3 44.5: .i !: 3 0.6 2.9 111 12.9 21.0 414 19.7 29.7 1.7 3.9 43.7: 1 · 1: 6 0.6 2.9 12.4 16.1 17.2 394 20.2 30.0 1.3 2.1 49.6 _8 ______ 18.2 387 _______ 9 0.5 1.0 13.4 18.0 ___ 382 21.2 29.5 1.3 1.3 45.2 10 _____ 19.4 377________ 11.5 0.4 0.2 13.7 18.7 ___ 366 21.7 29.4 1.4 1.1 46.1 11.7 0.1 0.001 13.0 18.3 ___ 177 21.9 30.0 1.3 1.1. 46.7 12 0.1 0.0004 13.8 18.3 21.8 279 21.7 29.0 1.5 1.4 46.2 • 1, 1 - J 1 --1-- * ·· 15 • · • · «• · 1 · 1 • · • · 1 · e · • · · ·· • • · • 1

Claims (12)

119819 The patent claims claims A process for improving the quality of a zinc-containing copper sulphide concentrate by removing the zinc from the concentrate to make the concentrate well suited for pyrometallurgical copper recovery, characterized in that the zinc is removed from the concentrate by dissolving the concentrate in a sulfuric acid solution under atmospheric pressure and temperature; before completion of the leaching, a reducing agent is introduced into the leaching step to precipitate dissolved copper 10. Process according to Claim 1, characterized in that, at the end of the leaching step, the sulfuric acid content is adjusted to a range of 0 to 100 g / l, preferably 5 to 25 g / l. 15 Process according to claim 1 or 2, characterized in that an oxidizing agent is fed to the dissolving step. The method of claim 3, wherein the oxidant is at least one of air, oxygenated oxygen, and oxygen. • · • · 1 • 1 · • • I Process according to claim 3, characterized in that at least one of hydrogen peroxide, manganese dioxide and potassium permanganate is used as the oxidizing agent. The process according to any one of claims 1 to 5, characterized in that: 1) the redox potential is adjusted such that at least 10 mg / l of copper are present at the beginning of the leaching and 30 are not present at the end of the leaching. M1 • · I · • · · · · · · 119819 Process according to one of Claims 1 to 6, characterized in that the reducing agent to be introduced to the end of the leaching step is a reducing gas. Process according to claim 7, characterized in that the gas is hydrogen sulphide. Process according to one of Claims 1 to 6, characterized in that the reducing agent to be terminated in the dissolution step is sodium hydrogen sulfide or sodium sulfide. Process according to one of Claims 1 to 6, characterized in that the reducing agent to be carried out at the end of the leaching step is a copper sulphide concentrate. Process according to one of Claims 1 to 10, characterized in that at the beginning of the leaching the solution contains at least 0.1 g / l of iron and at least 10 mg / l of copper. • »· φφφφ 20 PATENTKRAV • · • · φ • · # Ml