FI122781B - Process for making a copper product - Google Patents

Description

METHOD FOR MANUFACTURE OF A COPPER PRODUCT. FIELD OF THE INVENTION

The invention relates to a process for hydrometallurgically producing copper, the final purification of which is carried out in connection with a pyrometallurgical smelting process.

BACKGROUND OF THE INVENTION

Various methods of making copper 10 are intended to produce copper 10 that meets the requirements of LME-A (LME-London Metal Exchange, BS 6017: 1981). For example, when the copper raw material is copper sulphide ore, it is generally subjected to enrichment and leaching in either a sulphate or chloride environment. The copper-rich solution containing the impurities is then passed to a solution purification to remove the impurities. Solution purification of the sulphate-based solution is generally effected by liquid-liquid extraction, whereby the copper is first transferred to the organic phase and then to the second aqueous phase, which is led to the electrolytic recovery of the copper.

When the copper concentrate leach solution is chloride-based, the copper rich solution 20 is subjected to first-stage solution purification, usually by doping, and then traces of minor impurities are removed by ion exchange. If copper is recovered electrolytically, accurate solution purification may not be necessary. U.S. Patent No. 5,487,819 describes a process for the hydrometallurgical production of copper from copper-containing raw materials, such as copper sulphide concentrate. According to the method, the raw material is dissolved in countercurrent solution with sodium chloride-copper chloride solution in several steps to form a monovalent copper (I) chloride solution. The resulting solution is subjected to conventional solution purification by hydroxide precipitation as described in Example 6. The concentrations of zinc and lead in the copper (I) chloride solution after solution purification are at a level of 2 to 3 g / L and the solution is subjected to copper electrolysis.

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Chloride-based copper recovery is also described, for example, in U.S. Patent No. 6,007,600, and removal of impurities by ion exchange in EP Patent No. 1,497,474. After removal of impurities, copper (I) oxide is precipitated from a pure copper chloride solution with alkali hydroxide. The copper (I) oxide is reduced to a metallic copper by means of a suitable reducing agent. Solution purification of copper chloride prior to the precipitation of copper (I) oxide is a very important part of the process since all the metallic impurities present in the solution are co-precipitated with copper. Solution cleaning also accounts for quite a significant 10% of the total cost of the process.

From U.S. Patent No. 107,455 there is known a process for making copper from copper-containing raw materials. The raw material is dissolved in a multi-step solution in a chloride-based solution with hydrochloric acid and oxygen. The solution containing copper 15 is subjected to reduction of divalent copper with copper from a later step. The solution is subjected to solution purification with metallic copper and magnesium oxide and the resulting metallic impurities are removed as fines. Copper is precipitated from the chloride solution by means of magnesium oxide as copper oxide, or copper (I) oxide, Cu20. The copper (I) oxide precipitate is reduced, for example, by gas, oil or coal to metallic copper. The magnesium chloride solution formed by the precipitation of copper (I) oxide is fed to pyrohydrolysis, whereby fuel is used to form hydrochloric acid, which is used to dissolve the raw material. Part of the magnesium chloride solution can be directly led to the leaching of the 25 raw materials. Regeneration of magnesium by pyrohydrolysis consumes considerable energy.

In pyrometallurgical copper production, the copper sulphide concentrate is melted, for example, in a suspension melting furnace. The formed sulfur and iron containing copper stone 30 is processed in a converter where the iron and sulfur are removed and the copper is oxidized to a metal form. The final purification of the copper melt takes place in an anode furnace where, for example, the oxygen contained in the copper is reduced from the 3 copper smelters. Pure copper is cast into anodes for final electrolytic purification. Although the copper content of the anode copper is in the order of 99.3%, it still contains small amounts of nickel, arsenic, antimony and precious metals depending on the raw material. The cathode copper content of 5 is 99,998%, so it meets the LME-A requirements.

PURPOSE OF THE INVENTION

In some cases, it is preferable to combine hydrometallurgical and pyrometallurgical copper production. The process 10 according to the invention also enables hydrometallurgical processing of raw materials which are difficult to process pyrometallurgically. For example, the raw materials contain arsenic, chlorine or fluorine or have low copper content. The process developed can utilize sulfuric acid 15 formed or produced in the melting process in hydrometallurgical treatment. Hydrometallurgical manufacturing does not increase the production of sulfuric acid, which is advantageous, since placing sulfuric acid on the market sometimes causes difficulties. The solution purification step of a hydrometallurgically produced copper product becomes economically advantageous when the final treatment of the copper product takes place in a pyrometallurgical melting furnace.

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SUMMARY OF THE INVENTION

The invention relates to a process for producing a copper product hydrometallurgically from a copper sulfide-containing raw material for further pyrometallurgical processing of the product. The process comprises at least 25 the following steps: a) dissolving copper (l) chloride in the calcium containing solution as countercurrent solution with hydrochloric acid and oxygen gas to form a copper (l) chloride solution, (b) removing copper (l) cupric chloride formed therefrom, c) (l) the chloride solution is neutralized, 4 d) copper is precipitated from the copper solution (l) as a copper (l) oxide by means of a calcium compound, (e) the copper (l) oxide formed is subjected to pyrometallurgical treatment, and 5 (f) copper (l) oxide precipitated sulfuric acid to the hydrochloric acid which is led to the leaching of the copper sulphide concentrate.

In a preferred embodiment of the process of the invention, the copper (I) oxide formed is subjected to a pyrometallurgical reduction treatment to form a metallic copper product.

According to one embodiment of the invention, the copper (I) oxide is reduced by a carbon and / or hydrogen containing substance. Copper (I) oxide can be reduced, for example, by heavy fuel oil. The pyrometallurgical reduction of copper (I) oxide occurs at a temperature of at least 400 ° C.

According to the method, the metallic copper product is introduced into an furnace in the copper smelting process. According to one embodiment of the invention, the furnace for the copper 20 smelting process is a converter. According to another embodiment of the invention, the furnace for the copper smelting process is an anode furnace.

According to another embodiment of the process according to the invention, the copper (I) oxide formed is precipitated by precipitation of the formed chloride (I) by heating copper (I) oxide in an oxygen-containing gas stream, whereupon the chlorides evaporate and copper (I) oxide is oxidized to copper (II) oxide in the oven. According to one embodiment of the invention, copper (II) oxide is introduced into the concentrate melting furnace. According to another embodiment of the invention, the copper (II) oxide is introduced into a converter.

According to one embodiment of the invention, the iron and sulfur precipitate formed during leaching is removed as leaching waste.

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According to one embodiment of the invention, the copper (II) chloride solution is removed from the copper (II) chloride solution by reduction of the solution with copper in its metallic form. According to another embodiment 5 of the invention, the copper (II) chloride formed therefrom is removed by means of a lime compound as an attack amide.

According to one embodiment of the invention, the copper (I) chloride solution is neutralized with a lime compound and at the same time the impurity metals in the solution are precipitated therefrom. Typically, the impurity metal is at least one of lead, zinc, antimony or bismuth.

According to one embodiment of the invention, the copper-poor calcium chloride solution formed during the copper (I) oxide precipitation step contains magnesium and the solution is subjected to at least partial magnesium removal with a calcium compound before the solution is subjected to regeneration.

According to a preferred embodiment of the invention, a washing acid formed in a pyrometallurgical smelting process is used to regenerate the copper poor calcium chloride solution formed during the precipitation of copper (I) oxide.

LIST OF FIGURES

Figure 1 shows a flow diagram of an embodiment of the invention.

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DETAILED DESCRIPTION OF THE INVENTION

The process for dissolving and recovering copper-containing sulfide concentrates or raw materials according to the invention is based on dissolving the copper-containing raw material in a calcium-containing solution by means of hydrochloric acid and an oxygen-containing gas. Copper-containing, at least partially sulphidic, raw material may contain such impurities which cause difficulty if the raw material is fed to a copper smelter. These include, for example, arsenic, bismuth, antimony, magnesium, chlorine and fluorine. The feedstock for leaching may also be at least partially dust formed in the melt. For example, in addition to the sulfide component, the dust may also include oxide and / or sulfate components. In hydrometallurgical treatment, impurities of the raw material can be more readily eliminated than in pyrometallurgical treatment. When the text refers to concentrate, it also refers to other, at least partially sulfidic, raw materials.

The copper-containing raw material is leached at atmospheric pressure of 10 and at a temperature of 80 ° C - the boiling point of the solution being about 110 ° C. In the leaching step, the copper sulphide of the concentrate reacts with hydrochloric acid and oxygen to form copper (I) chloride. Due to the high chloride content of the solution, copper (I) chloride also remains soluble.

15 2CuFeS2 + 202 + 2HCl -> 2CuCl + Fe203 + 4S + H2O (1)

The leaching takes place in multi-step countercurrent leaching 1. Seen in the direction of concentrate flow, the first step is non-oxidizing and at least the last step is oxidizing. Oxygen, oxygen-enriched air or air is used as the oxidizing agent. Part of the iron in the concentrate dissolves in the first leaching step, but in the oxidizing leaching stage the iron is precipitated again. Sulfur of the concentrate is precipitated as elemental sulfur and from the final leaching step, a leaching residue containing the iron and sulfur of the concentrate is removed. Iron precipitates as hematite, which is the most preferred form of iron precipitation. A small amount of sulphate is also formed in the leaching residue. If the copper-containing raw material contains arsenic, it remains in the leaching residue. Therefore, arsenic-containing raw materials such as arsenic-based copper concentrate or smelting dust can be used in the process. If the concentrate contains gold or platinum metals (PGM), they will also remain in the leaching residue and may be recovered therefrom.

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As a result of the leaching step, a solution is obtained in which the copper is predominantly in the monovalent chloride form, but also partially in the divalent form. When leaching occurs in the presence of a calcium ion, the amount of divalent copper chloride formed is quite small. It is more preferred for further processing that the copper is monovalent and therefore the divalent copper is removed in step 2, for example by reduction to monovalent. For example, copper in metallic form may be used as the reducing material. This is the case, for example, with scrap copper, anode scrap or later metallic copper from the process. Removal of divalent copper 10 from the solution may also be effected, for example, by means of limestone, whereupon acacamite, or alkaline copper chloride, is precipitated from the solution and returned to the leaching step.

The copper (I) chloride solution is preferably neutralized in the neutralization step 3 before the copper is precipitated from the solution. Neutralization can be carried out, for example, using limestone CaCO 3. During neutralization, most of the impurity metals in the solution precipitate. The impurity metal is at least one of lead, zinc, antimony or bismuth. The pH of the solution to be neutralized is in the range of 2 to 4.5, depending on the concentration of CaCl 2 in the solution and the method of precipitation of divalent copper. By neutralization, the pH of the solution is raised to 6-7.

After the neutralization step, the solution is led to a copper precipitation step 4, where copper is precipitated from the chloride solution as copper (I) oxide by means of calcium hydroxide (Ca (OH) 2), i.e. lime or calcined lime (CaO), whereupon calcium chloride is formed. When copper is precipitated from a solution which has not undergone actual impurity removal, copper is precipitated as an oxide which also contains small amounts of other metal oxides. The amount of other metal oxides is in the order of a few hundred milligrams per liter.

30 2CuCl + Ca (OH) 2 Cu20 + CaCl2 + H2O (2) 8

Thereafter, there are two options for the treatment of copper oxide, either reduction to metallic copper or introduction of the formed copper oxide into the smelter without reduction.

Since the copper produced by reduction is to be fed to the pyrometallurgical treatment of copper, it may contain the small amounts of other metals mentioned above. The formed copper oxide is reduced in a reduction step 5 by means of a suitable preferred reducing agent. This may be, for example, heavy fuel oil or other reducing agent containing carbon and / or hydrogen. The reduction is done by heating the copper oxide-reducing agent mixture in an oven. The reduction occurs rapidly only above 400 ° C. The reduction furnace yields copper, which is preferably fed as hot as possible into an furnace, such as a converter or anode furnace, in the copper smelting process. On the other hand, once the copper has cooled, it can also be used to control the thermal balance of the converter 15, since in some circumstances too much heat is generated in the converter.

If copper oxide is to be fed into an furnace as an oxide in the copper smelting process, it will be necessary to purify all chloride residues, which are usually in the form of the attackamite. The wet doped copper (I) oxide is dried, after which it can be purified from chloride, for example by heating it in a gas stream, whereupon the acacamite is decomposed into water and copper chloride. The water is released from the attackamite at a temperature of about 250 ° C, but the evaporation of copper chloride is only significant at a temperature of about 500 ° C. When the gas stream is an oxygen-containing gas such as air, the copper (I) oxide is oxidized to the copper (II) oxide while releasing heat. The exhaust gas of the heating member is cooled, whereupon the copper chloride condenses and can be recycled to a suitable part of the process. The hot gas from the condensation is again recycled to the drying of the copper (I) oxide. By selecting the appropriate amount of gas to be used and the process temperature, the filter damp copper (I) oxide can be purified from chloride with almost no external energy.

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In the process of the invention, the copper-poor calcium chloride solution formed during the copper (I) oxide precipitation step always contains some magnesium and is preferably removed from the solution. It is also advantageous to carry out the magnesium removal 6 by means of a calcium compound. The amount of magnesium is usually 5 such that it is sufficient to be removed in the side stream. The magnesium precipitate formed is removed from the circuit.

MgCl 2 + Ca (OH) 2 Mg (OH) 2 + CaCl 2 (3) 10 The purified and copper-poor calcium chloride solution is subjected to regeneration 7 in the leaching step 1 to form the hydrochloric acid required. It is preferable to regenerate the calcium chloride solution with sulfuric acid into hydrochloric acid and gypsum. When the hydrometallurgical treatment of the copper sulphide concentrate takes place in the vicinity of the pyrometallurgical treatment process, 15 molten wash acids (approximately 50 wt.%), Often arsenic-containing sulfuric acid, can be used for regeneration. Although the resulting hydrochloric acid contains arsenic and other possible impurities, it does not interfere with the process since the arsenic is precipitated in the leaching residue upon leaching of the concentrate. Of course, it is clear that pure sulfuric acid from sulfur dioxide gas 20 produced by the smelting process can also be used for regeneration. Regeneration takes place at the natural temperature of the process and at atmospheric pressure.

CaCl2 + H2SO4 2 HCl + CaSO4 (4) 25 Combining the hydrometallurgical copper production process with the pyrometallurgical process allows for the passage of non-smeltable concentrates to the hydrometallurgical treatment. The hydrometallurgical copper product can be used to increase anode production without increasing the gas line or increasing sulfuric acid production. Also, the copper product according to the process does not increase the amount of slag in the smelter. If necessary, the copper product can be used to cool the furnace in some melting process.

EXAMPLES Example 1 The example illustrates a calcium chloride solution regenerated by sulfuric acid.

The composition of the calcium chloride solution was as follows: Ca 56.8 g / l, Mg 0.93 g / l and Na 22.2 g / l. The temperature of the solution was 60 ° C and its volume was 1 I. 98.1 g of sulfuric acid having a concentration of 98 wt% were added to the solution. The addition of acid raised the solution 10 to 80 ° C and precipitated the solution as calcium sulfate 152.7 g. The composition of the final solution, i.e. the solution to be leached, was: Ca 22.1 g / l, Mg 0.94 g / l and Na 21.6 g / l and 70 g / l HCl. The gypsum precipitate formed was washed and its composition after water washing was: Ca 22.2 wt%, Mg 0.004 wt%, Na 0.06 wt%, SO 4 56.4 wt% and Cl 0.01 wt%.

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Claims (18)

A process for the preparation of a copper product hydrometallurgically from a copper sulphide-containing raw material for the pyrometallurgical further processing of the product, characterized in that the process comprises at least the following steps: a. The copper sulphide-containing raw material is leached by countercurrent solution in hydrochloric acid and oxygen ) to form a chloride solution, b. the copper (II) chloride formed therefrom is removed from the copper (c) chloride solution, c. neutralizing the copper (I) chloride solution, d. copper is precipitated from a copper (I) chloride solution as copper (I) oxide by means of a calcium compound, e. leaching. Process according to Claim 1, characterized in that the formed copper (I) oxide is subjected to a pyrometallurgical reduction treatment to form a metallic copper product. 25 Process according to claims 1 and 2, characterized in that the copper (I) oxide is reduced by a carbon and / or hydrogen containing substance. Process according to Claim 3, characterized in that the copper (I) oxide is reduced by heavy fuel oil. Process according to claims 1 and 2, characterized in that the reduction of the copper (I) oxide takes place at a temperature of at least 400 ° C. Method according to claims 1 and 2, characterized in that the metal copper product 5 is introduced into an furnace in the copper smelting process. Process according to claim 6, characterized in that the furnace for the copper smelting process is a converter. 10 Process according to claim 6, characterized in that the furnace for the copper smelting process is an anode furnace. Process according to Claim 1, characterized in that by precipitation of the formed copper (I) oxide, the chlorides contained therein are removed by heating it in an oxygen gas stream, whereby the chlorides evaporate and the copper (I) oxide is oxidized to copper (II) oxide which is fed to a furnace . Process according to Claim 9, characterized in that the copper (II) oxide is introduced into the concentrate melting furnace. Process according to Claim 9, characterized in that the copper (II) oxide is introduced into the converter. A process according to claim 1, characterized in that the iron and sulfur precipitate formed during leaching is removed as leaching waste. Process according to Claim 1, characterized in that the copper (II) chloride formed in the copper (II) chloride solution is removed therefrom by reduction of the solution with copper in its metallic form. Process according to Claim 1, characterized in that the copper (II) chloride solution formed therefrom is removed by means of a lime compound as the attack amide. 5 Process according to Claim 1, characterized in that the copper (I) chloride solution is neutralized with a lime compound and at the same time the impurity metals in the solution are precipitated therefrom. Method according to claim 15, characterized in that the impurity metal is at least one of lead, zinc, antimony or bismuth. Process according to Claim 1, characterized in that the copper-poor calcium chloride solution formed during the copper (I) oxide precipitation step contains magnesium and the solution is subjected to at least partial magnesium removal with a calcium compound before the solution is subjected to regeneration. Process according to Claim 1, characterized in that a washing acid formed in a pyrometallurgical smelting process is used for the regeneration of the poor copper chloride solution formed during the precipitation of copper (I) oxide. 25