METHOD FOR OBTAINING COPPER FROM CUPRIFEROUS ARSENOSULPHIDE AND/OR ANTIMONY SULPHIDE ORES OR ORE CONCENTRATES

Abstract

Process for extracting copper from copper-bearing arsenic sulfide and/or antimony sulfide ores, ore concentrates or minerals, comprising the following steps: converting the ores, ore concentrates or minerals by reaction with sulfur at 300 to 600° C. for at least 5 min; grinding the reaction product; physically separating the arsenic and/or antimony sulfides obtained at least partially from copper-containing sulfides; treating the separated copper-containing sulfides by pyrometallurgical or hydrometallurgical processes to obtain copper.

Description

The present invention relates to a process for extracting copper from copper-bearing arsenic sulfide and/or antimony sulfide ores.

By far the biggest part of the world's copper production (about 90%) is extracted from copper sulfide minerals. Among the copper sulfide minerals, there may be mentioned, above all, chalcopyrite (CuFeS₂), bornite (Cu₅FeS₄), cubanite (CuFeS₄), chalcosine (Cu₂S), digenite (Cu₉S₅), covelline (CuS), enargite (Cu₃AsS₄), tennantite (Cu₁₂As₄S₁₃) and tetrahedrite (Cu₁₂Sb₄S₁₃).

Among the copper sulfide minerals, chalcopyrite is the most widespread mineral; therefore, it is of the greatest scientific and economic importance in the development of new extraction methods.

In addition, chalcopyrite and the above mentioned minerals are characterized by always containing deposited gold, silver, platinum metals and other rare metals as well as rare earths.

The copper/iron-sulfidic minerals are extracted from ores, which are usually milled and concentrated by a flotation process to yield an ore concentrate, whereby a substantial part of the silicates contained in the ground stock, in particular, is separated off.

Today, in addition to the known pyrometallurgical and chemical hydrometallurgical processes, there are various approaches to leaching copper and other metals occurring in the copper sulfide minerals from the ores or ore concentrates using hydrometallurgical bioleaching processes. This involves the problem that only part of the copper contained in chalcopyrite can be leached out using the known processes because passivation of the chalcopyrite occurs.

Many copper-bearing ores additionally contain arsenic and antimony compounds, for example, enargite (Cu₃AsS₄), tennantite (Cu₁₂As₄S₁₃) and tetrahedrite (Cu₁₂Sb₄S₁₃). These ores are difficult to process. In addition to the environmental problems occurring in the processing of such ores, the arsenic and antimony contents in higher levels are also damaging to the plants employed in the pyrometallurgical treatment.

WO 01/44524 describes a process for extracting copper from chalcopyrite-containing ores in which the chalcopyrite-containing ores are converted to covelline, pyrite and accompanying substances by the addition of sulfur and then copper is extracted by leaching steps of the microbiological or chemical type.

It was the object of the present invention to develop a process by which the extraction of copper from copper-bearing arsenic sulfide and/or antimony sulfide ores can be improved.

This object is achieved by a process comprising the following steps:

• • converting the ores, ore concentrates or minerals by reaction with sulfur at 300 to 600° C. for at least 5 min;
  • grinding the reaction product;
  • physically separating the arsenic and/or antimony sulfides obtained at least partially from copper-containing sulfides;
  • treating the separated copper-containing sulfides by pyrometallurgical or hydrometallurgical processes to obtain copper.

According to the invention, the copper-bearing arsenic sulfide and/or antimony sulfide ores, ore concentrates or minerals are converted to arsenic and/or antimony sulfides and copper-containing sulfides using sulfur.

Then, according to the invention, arsenic and/or antimony sulfides are physically separated from copper-containing sulfides at least partially at first.

Preferably, at least 70 or 90%, more preferably at least 95%, by weight of the arsenic and antimony sulfides are separated. Then, copper can be extracted from the thus purified copper sulfide using pyrometallurgical and hydrometallurgical processes known to the skilled person, avoiding the problems normally arising from the presence of admixed arsenic or antimony sulfides.

The separation of the copper sulfides and arsenic or antimony sulfides is effected by grinding at first. In a preferred embodiment, the separation can be effected by electrostatic processes, gravimetric processes, magnetic processes, air classification, grain size selection, a hydrocyclone, flotation processes or combinations thereof.

In one embodiment, at least two separation methods are combined.

Another possibility is the selective heating of minerals with microwaves of different frequencies in order to alter the physical properties of individual minerals to enable their being separated off selectively, for example, by magnetic methods.

The ores employed according to the invention typically contain other metal components, especially rare earths, gold, silver, platinum, cobalt, nickel, zinc. Depending on the process control, these can migrate with either the arsenic or antimony sulfide phase or the copper sulfide phase, or be separated off in separate phases.

According to the invention, the precious metals, for example, gold and silver, in the copper-containing phase are preferably enriched almost completely by a diffusion process and thus can also be recovered almost completely among the other copper-sulfidic minerals particularly easily.

Inasmuch as sulfur is obtained in the further processing, it may be advantageously recycled to the starting step of the process.

In particular, the pyrometallurgical processing includes a step referred to as “smelting”. In this step, oxygen is blown into the molten material so that the following reactions proceed:

CuS+0₂→Cu+SO₂.

The thus obtained Cu is then typically freed from excess oxygen by adding reducing agents. Subsequently, electrorefining may also be used.

The arsenic or antimony sulfides obtained may be used for preparing arsenic or antimony; it is also possible to dispose of them.

Preferably, the reaction is performed in an inert atmosphere. In one embodiment, the conversion is performed in a continuous process, preferably in a three-chamber system.

The reaction may be performed in a nitrogen atmosphere, for example, but also in argon or in a mixture of the inert gases. Flue gas may also be used, preferably SO₂.

In a preferred embodiment, the grinding process is effected in a rotary kiln or in a fluidized bed reactor in situ by adding grinding balls, for example.

Particularly suitable for the realization is conversion in a rotary kiln or fluidized bed reactor.

Typical reaction times are around 5 min to 24 h, preferably 5 min to 12 h, or 15 min to 24 h, or 0ö6.5 h to 24 h, especially from 5 to 90 or from 5 to 60 min.

Temperatures from 300° C. upwards, preferably >380 ° C. or >400° C., are suitable. The temperature is preferably <500° C., more preferably ≦475° C. or ≦<450° C. Temperatures of from 450 to 500° C. are particularly preferred.

The reaction time is dependent on the grain size of the ores, ore concentrates and minerals employed. Preferred values for d50 are below 210 μm, such grain sizes typically being obtained in the processing of ores by flotation. Grain sizes of d50=410 μm, d50=350 μm and d50=125 μm may also be employed.

The starting materials can be selected from copper-containing ores, ore concentrates or minerals, such as enargite (Cu₃AsS₄), tennantite (Cu₁₂As₄S₁₃) and/or tetrahedrite (Cu₁₂Sb₄S₁₃), optionally accompanied by chalcopyrite (CuFeS₂), bornite (Cu₅FeS₄), cubanite (CuFeS₄), chalcosine (Cu₂S), digenite (Cu₉S₅) and/or covelline (CuS).

The amount of sulfur employed can be stoichiometric, half-stoichiometric or catalytic.

Depending on the composition of the starting material, the copper-containing sulfides obtained may be covelline, chalcosine, digenite, bornite. The arsenic and antimony sulfides are typically obtained as As₂S₃ or asS and Sb₂S₃ or SbS, respectively.

The reactions can be described in part by the following equations:

2 Cu₃AsS₄+0 S→6 CuS+AsS (S only catalytically)

2 Cu₃AsS₄+S→6 CuS+As₂S₃

Cu₁₂As₄S₁₃+5S→12 CuS+2As₂S₃

Cu₁₂Sb₄S₁₃+5S→12 CuS+2Sb₂S₃

If the copper ore contains iron, the following reactions take place additionally:

Cu₅FeS₄+3S→5 CuS+FeS₂

Cu₅FeS₄+2S→5 CuS+FeS

CuFeS2+0.5 S→CuS+FeS

EXAMPLE

FIGS. 1a and b show the conversion of an ore by the converting step employed according to the invention.

FIG. 1a shows a chalcopyrite-containing ore, and FIG. 1b shows the converted ore: a pyrite core with a coat of covelline. Arsenic and antimony are enriched in the pyrite.

FIGS. 2a and b show a copper ore before and after the conversion. FIG. 2a shows the copper ore before the conversion; iron, copper and precious metals are homogeneously distributed, and FIG. 2b shows the copper ore after the conversion; copper and iron are separated, and the precious metals are enriched in the copper sulfide.

Claims

1. A process for extracting copper from copper-bearing arsenic sulfide and/or antimony sulfide ores, ore concentrates or minerals, comprising the following steps:

converting the ores, ore concentrates or minerals by reaction with sulfur at 300 to 600° C. for at least 5 min;

grinding the reaction product;

physically separating the arsenic and/or antimony sulfides obtained at least partially from copper-containing sulfides; and

treating the separated copper-containing sulfides by pyrometallurgical or hydrometallurgical processes to obtain copper.

2. The process of claim 1, wherein the conversion is performed in an inert atmosphere.

3. The process claim 1, wherein the conversion is performed in a continuous process.

4. The process of claim 1, wherein the temperature is at 450° C. to 500° C.

5. The process of claim 1, wherein the conversion is performed in a rotary kiln or fluidized bed reactor.

6. The process of claim 1, wherein the conversion is performed during a period of from 5 min to 12 h.

7. The process of claim 1, wherein the time is from 5 min to 90 min.

8. The process of claim 1, wherein an enrichment of the precious metals in the copper-sulfidic phase takes place during the conversion.

9. The process of claim 1, wherein the sulfur is added in stoichiometric, half-stoichiometric or catalytic amount.

10. The process of claim 1, wherein the antimony and/or arsenic sulfides are transferred to a processing step.

11. The process of claim 1, wherein the separation of the antimony and/or arsenic sulfides is effected by electrostatic processes, gravimetric processes, magnetic processes, air classification, grain size selection, hydrocyclone methods, flotation processes or combinations thereof.

12. The process of claim 1, wherein the copper-bearing arsenic sulfide and/or antimony sulfide ores, ore concentrates or minerals are selected from the group consisting of enargite (Cu3AsS4), tennantite (Cu12As4S13), tetrahedrite (Cu12Sb4S13), and combinations thereof, optionally accompanied by chalcopyrite (CuFeS2), bornite (Cu5FeS4), cubanite (CuFeS4), chalcosine (Cu2S), digenite (Cu9S5) and/or covelline (CuS).

13. The process of claim 3, wherein the conversion is performed in a three-chamber system.

14. The process of claim 6, wherein the conversion is performed during a period of from 5 min to 12 h.