FI107455B - Process for producing copper - Google Patents

Abstract

The invention relates to a process for producing copper from copper-containing raw material such as sulphide concentrates, scrap and precipitates. The raw material is dissolved by being dissolved in several stages in a chloride-based solution. The copper-containing solution which results from the dissolution process is subjected to reduction and solution refinement, after which copper which is present in the solution is precipitated out as copper protoxide using magnesium oxide. Magnesium chloride solution which is formed when producing the copper protoxide is fed to pyrohydrolysis, in which the magnesium chloride is regenerated back into magnesium oxide, which is used both in the solution refinement and the precipitation of the copper protoxide. Hydrochloric acid which is formed in the pyrohydrolysis is used for dissolving the concentrate or other raw material. The precipitated copper protoxide is reduced to metallic [lacuna] using a suitable reagent.

Description

1 107455

METHOD FOR THE PREPARATION OF COPPER

This invention relates to a process for the production of copper from copper-containing raw materials such as sulphide concentrates, scrap and fines. 5 The raw material is dissolved in a multi-step solution in a chloride-based solution. The copper-containing solution resulting from the leaching is subjected to reduction and solution purification, after which the copper in the solution is precipitated as copper oxide by means of magnesium oxide. The magnesium chloride solution from copper oxide production is fed to pyrohydrolysis where the magnesium chloride is regenerated into magnesium oxide for both solution purification and copper oxide precipitation. Hydrochloric acid produced by pyrohydrolysis is used to dissolve the concentrate or other raw material. The precipitated copper oxide is reduced to metal with a suitable reagent.

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Leaching of sulphidic copper raw material in the chloride environment is known and it is preferred that leaching can be performed at normal pressure and that leaching will cause most of the concentrate copper to dissolve in monovalent cuprous form as Cu1 +, which in principle reduces energy consumption from -20% to normal, electrolyte for the production of its copper metal. Typical examples of such process * * * stands are the so-called "process" stands already developed in the 1890s. The Hoepfner process described in U.S. Patent No. 507,130, as well as the CLEAR and INTEC processes, the first of which is described, e.g. U.S. Patent 3,785,944 and the latter e.g.

25 articles by van Os, J.: "Australian company reveals low cost process for 'Ϊ /.' granular copper ', Metal Bulletin Monthly, January 1991, p. 67.

• · • · ·

However, there are many reasons for reducing the energy consumption of a bubble process • · in practice. In addition, the ♦ · · * · * '30 disadvantage is that the metal is produced in granular, which is not a normal * ···' commercial quality. Due to this, and possibly also to the removal of impurities, 2 107455 grains of copper may still need to be thawed and refined before being marketed, as experience with the CLEAR process shows.

Another disadvantage of electrolytic copper metal production in the chloride environment from the Cu1 + solution is that the structure of the electrolytic cells is easily complicated, e.g. U.S. Patent 4,025,400, which also describes the CLEAR process. The complexity of the structure is mainly caused by the granular product, which grows as 10 needle-like crystals on the surface of the cathode, from which it periodically scrapes off and drops to the bottom of the cell and further removes it. It also has the effect that the cathode and anode spaces of the cell must be separated by either a diaphragm or a membrane. This and the needle-like growth of copper grains on the cathode surface cause that the distance between the electrodes to ensure trouble-free operation 15 (short circuits!) Cannot be very small, which in turn increases energy consumption.

Attention is drawn to the complexities and shortcomings of the electrolysis step: U.S. Patent 4,097,271, which discloses a method for precipitating a solid addition compound of butadiene and copper (I) chloride from a solution of sulfide crude chloride in gaseous butadiene and copper (I) chloride. The aqueous slurry of * ··· * copper crystals (l) chloride obtained in the process is then oxidized in an autoclave to produce a copper (II) oxychloride precipitate and a copper (II) chloride solution which is returned to the sulfide raw material leaching. The oxychloride precipitate is then converted at normal pressure with sodium hydroxide solution *** into copper (II) oxide (CuO) according to the following reaction:

CuCl2. 3Cu (OH) 2 + 2NaOH = 4CuO + 2 NaCl + 4H 2 O (1) 3 107455

The copper (II) oxide, on the other hand, is reduced in the converter at spaces above the melting point of copper by hydrogen leaching, apparently according to reaction (2), to metallic copper:

CuO + H 2 = Cu + H 2 O (2) Then, in the above process, the sodium chloride solution produced by the reaction (1) is subjected to chlor-alkali electrolysis to produce the sodium hydroxide needed for the reaction (1). In addition, chlor-alkali electrolysis produces hydrogen gas which is utilized in the reduction of copper (II) oxide according to reaction (2).

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It is also known in the US patent 6,007,600 to recover copper from a copper raw material in a chloride atmosphere by precipitating the copper (I) chloride solution as copper oxide with sodium or potassium hydroxide and reducing the resulting copper oxide to elemental. The process takes advantage of the advantage of hydrometallurgical chloride processes for copper: the possibility of utilizing a lower degree of oxidation. This is illustrated by the following reaction (3), which shows that at a lower oxidation rate the same amount of copper is now produced with the same amount of copper as in reaction (2): 20 CuzO + Hz = 2 Cu + HzO (3) i Sodium chloride formed by copper oxide precipitation is regenerated in chlor-alkali electrolysis to sodium hydroxide and recycled into oxide precipitation. Electrolysis also produces hydrogen, which is · · '···' utilized in the reduction steps of the process and the chlorine produced ... to dissolve 25 copper raw materials.

The purpose of the presently developed process is to eliminate the drawbacks of the sodium or potassium chloride based methods described above.

»The starting point is the countercurrent leaching of a copper raw material such as copper sulphide concentrate, scrap V: 30 or fine in a magnesium chloride environment to yield a · ···’ essentially iron-free magnesium chloride-copper chloride solution with 4 107455 copper in most monovalent or Cu1. Among the advantages of the magnesium chloride milieu, it can be mentioned that, when operated therein, the solution has a higher chloride content than, for example, a sodium chloride milieu. As a result, the Cu2 + / Cu1 + ratio of solution 5 produced by concentrate leaching is more advantageous when operating on a MgCl2 basis than on a sodium chloride base, which reduces the need for post-leaching reduction and in-process copper circulation. In addition, the regeneration of magnesium oxide from magnesium chloride can be done by thermal energy, whereas the regeneration of sodium hydroxide from sodium) chloride, for example, must be done by means of electricity (electrolysis). The essential features of the invention will be apparent from the appended claims.

In the process, the sulfur of the raw material is removed from the process in an elementary manner. The divalent copper, Cu2 +, of the solution produced by the countercurrent leaching is reduced to monovalent, for example, with metallic copper or hydrogen gas before the solution is subjected to a solution purification to remove the harmful impurities present in the solution. From the purified copper (I) magnesium chloride solution, copper oxide is precipitated with magnesium oxide, which is: reduced to a suitable reagent for the metal. The reduction is effected either from 20 aqueous slurries in an autoclave or in an oven, whereby the precipitate may be in a solid state or in a molten state. The oxide dust precipitate can also be fed into the copper smelter

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at some point suitable for the copper manufacturing process.

The precipitation of copper oxide is carried out, for example, by the magnesium oxide produced by pyrohydrolysis of magnesium chloride according to the following reaction: · V '2CuCl + MgO = Cu20 + MgCl2 (4) • · · * The use of pyrohydrolysis is a feature of the invention in that it regenerates: 30 magnesium chloride formed in the Cu20 precipitation into magnesium hydroxide and 5 107455 produces hydrochloric acid for the same process according to the following reaction:

MgCl 2 + H 2 O = MgO + 2 HCl (5)

The reaction is known per se and used in industry, but not in the preparation of copper 5. In pyrohydrolysis, magnesium chloride is subjected to a thermal decomposition by means of water vapor, which produces magnesium oxide and hydrochloric acid when the temperature is high enough.

The hydrochloric acid produced by the pyrohydrolysis is utilized to dissolve the sulfuric 10 Cu concentrate or other copper raw material, for example, to regenerate the solvent Cu 2+ ion according to the following reaction: 2CuCl + 0.5 02 + 2HCl = 2CuCl 2 + H 2 O 1, which shows a flow diagram of a copper fabrication method according to the invention.

In the copper production process of Figure 1, the leaching of a copper raw material j such as chalcopyrite copper concentrate (CuFeS2) 1 is carried out in I · ti 20 in a multi-step countercurrent leaching 2. In this case, leaching is performed in circulating, either copper 4 is led to one of the intermediate stages of leaching • * * • ♦ * ··· * to precipitate iron in the raw material. The sulfur remains in the precipitate as elemental sulfur and is separated from the iron precipitated leaching residue 5 in known ways, if separation is required.

The copper contained in the raw material is soluble in countercurrent in leaching, and leaching results in a substantially iron-free, copper-rich solution *: * a more concentrated solution 6 in which the leached copper is essentially monovalent -

• »I

'30 as a cupro-ion Cu1 +, but also partially as a divalent cupro-ion Cu2 +.

The solution 6 from the leaching of the raw material is divided into two portions, 6 107455 of the other 6a, is passed to an oxidation step 7 according to reaction (6) to regenerate the divalent copper by counter-current leaching. A second portion of the solution 6b is led to a reduction 8 which is intended to reduce all the divalent copper contained in the solution to monovalent. The reduction 5 is preferably carried out with a pair of elemental batteries 9 obtained from a later process step. Instead of hydrogen, hydrogen or other suitable reducing agent may also be used.

The reduction solution 10, where all the copper is now monovalent, is then passed to a solution purification 11 where the impurities in the CuCl-MgCl 2 solution are removed using conventional methods and reagents 12 and the downstream products: copper 9 and magnesium oxide 14 from pyrohydrolysis 13 precipitating the metallic impurities 15 from the copper (I) chloride solution as fines 15 which are removed from the process.

The pure copper chloride-magnesium chloride solution 16 is led to a copper precipitation step 17 to precipitate copper from the solution as copper oxide Cu20 18. i, i; Precipitation is carried out with magnesium oxide 14 formed by pyrohydrolysis 13.

j'V 20 i A portion of the magnesium chloride solution 3 from precipitation 17 is passed to '···' for pyrohydrolysis 13. The remainder of the magnesium chloride solution is • • · • »returned to countercurrent leaching 2. · Through the pyrolysis, · the amount of solution is sufficient to 25 for the reactions required for oxide precipitation. In Pyrohydrolysis 13 • · J ”. the hydrochloric acid 20 formed by the fuel 19 is fed to the oxidation 7 and its product solution 21, which now contains bivalent copper, is further leached. The fuel 19 may be gas or oil.

30 »« 7 107455

The copper oxide precipitate 18 from the Cu20 precipitation is reduced in the metallurgical reactor 22 by means of a reducing agent 23 to a metallic copper 9, which can be further smelted. The reducing agent used in the metallurgical reactor is gas, oil or coal. Part of the reduced copper 5 is used as the reducing agent 9 in the divalent copper reduction step 8 and the solution purification step 11.

The method according to the invention is further illustrated by the following example.

10 Example

In an experiment, the precipitation of copper oxide with magnesium oxide from a solution of copper chloride-magnesium chloride was investigated. The experiment was carried out by initially loading 250 ml of a solution containing 220 g / l MgCl 2 into a two liter laboratory reactor with a lid. Reactor 15 was heated to 55 ° C where it was maintained throughout the experiment. A small amount of nitrogen gas was blown into the reactor throughout the experiment. The purpose was to prevent both the entry of air into the reactor and the oxidation of Cu1 + to Cu2 +.

During the first two hours, a solution of 70 g / l monovalent copper in the form of copper chloride :: v CuCl and 220 g / l MgCl 2 was fed to the reactor at a constant rate of 20 ml / min. In addition, the reactor was fed at a constant rate of 2.5; ; ml of aqueous slurry containing 100 g / l MgO. Magnesium oxide was of fine commercial grade. During the second two hours, the reactor was no longer fed. ···, nothing but the slurry was stirred. So the test took a total of four hours.

• · t · · ·. 25 »· • · ·

The pH of the slurry was measured from the reactor and samples of the slurry were subjected to •: · ·: analyzes. The results were: «· · • t

• I

• I

. "! 30 • · · · 8 107455

table 1

Time pH Cu Mg (h) (55 "Cj" gJ \ g / i Ö 5ÄÖ 567 Ö25 7 ^ 8 367. - - 457 Ϊ7 7J2 67 477 2 ~~ 7J3 67 497 3 T29 37 5Ö6 4 77 37 5Ϊ

At the end of the experiment, a sample was taken from the precipitate and washed thoroughly. When dried, the precipitate contained 78% Cu, 1.3% Mg. According to X-ray diffraction, the sample contained only copper oxide, Cu 2 O, and a small amount of Cu (II) oxide, apparently formed during sample treatment.

The results of the test indicate to a person skilled in the art that with fine MgO 10 such as a pyrohydrolysis product of MgCl 2 solution, copper can be practically sufficiently and selectively precipitated from the CuCl-MgCl 2 solution as Cu 2 O, suitable for various processes. ·] For the production of copper metal. Precipitation does not have to be complete because • »• · ·. ···. At pyrohydrolysis, CuCl does not decompose at temperatures where MgCl 2 decomposes.

♦ · »; ***; 15 Also, the selectivity does not have to be perfect, since Mg is not a · · · harmful substance in the 7 ″ pyrometallurgical process ending in copper smelting. It should also be noted that the possibly slightly Mg-containing copper oxide produced by the process of the invention may be treated with an aqueous solution of hydrochloric acid produced by the pyrohydrolysis of Figure 1, whereby the reaction: · · · · MgO + 2HCl -> MgCl 2 (7) * I · ♦ ♦ · 9 107455

This reaction dissolves magnesium from the copper oxides if it hinders further processing.

I I I * • • • * «# • • • • • • • • • • • • • • • *

Claims (11)

10 107455 A process for recovering copper from copper raw materials (1) such as sulfide concentrates, scrap and fines in a chloride environment, wherein the 5 raw materials are leached into copper-free or copper-containing chloride solution (3) by multi-step countercurrent leaching (2) 6) is subjected to reduction (8) and solution purification (11), after which the copper is precipitated from the chloride-containing solution (16) as copper oxide (18) and the copper oxide formed (22) is reduced to elemental copper (9), characterized in that leaching (2) of the material is carried out by means of magnesium chloride (3), and part of the magnesium chloride is regenerated after the oxidation precipitation (17) by pyrohydrolysis (13) to magnesium oxide (14) which is used as the precipitation reagent for Cu20 precipitation (16). 15 Process according to Claim 1, characterized in that a portion (6a) of the solution from the copper raw material leaching (2) is led to an oxidation step (7), wherein the monovalent copper in the solution is oxidized: by dichloromethane (13) hydrochloric acid and The product solution (21) obtained 20 is recycled to the raw material leaching (2). «« • · · • · Process according to Claim 1, characterized in that the magnesium oxide (14) produced by the pyrolysis (13) is utilized as a solution in the purification (11). 25 • · • · ·. ···. 4. A method according to claim 1, characterized in that the elemental copper (9) produced in the process is utilized in solution. in cleaning (11). a fence " · · Method according to claim 4, characterized in that the solution (6b) resulting from the leaching of the copper raw material is subjected to reduction of divalent 11 107455 copper to monovalent by the elemental copper (9) produced in the method. Process according to Claim 1, characterized in that the leaching of the copper-5 raw material is carried out with a magnesium chloride solution (3) coming from a Cu20 precipitation (17). A process according to claim 1, characterized in that the reduction of the copper oxide gas is carried out in a solid state. 10 Process according to Claim 1, characterized in that the reduction of the copper oxide gas is carried out as an aqueous slurry in an autoclave. Process according to Claim 1, characterized in that the reduction of copper oxide gas is carried out in the presence of metallic copper at temperatures above the melting point of copper. The method according to claim 9, characterized in that the copper:.:; the oxide gas is reduced by feeding it to a suitable step in the copper smelter. : V 20 The method according to claim 1, characterized in that the elemental copper (9) is melted and cast into compact copper. • * • · ♦ ♦ · «• ♦ ♦ ♦ ♦ ♦ * * * * * * «« * · «» M * «· II | * · A a 107455