WO2016171613A1

WO2016171613A1 - Method and furnace equipment for production of black copper

Info

Publication number: WO2016171613A1
Application number: PCT/SE2016/050355
Authority: WO
Inventors: Matej IMRIS; Bror Magnus HEEGAARD; Sven Santén
Original assignee: Val'eas Recycling Solutions Ab
Priority date: 2015-04-24
Filing date: 2016-04-22
Publication date: 2016-10-27

Abstract

A method for production of black copper comprises an oxidation step (210) and a reduction step (260). The oxidation (210) comprises melting and agitation of an initial material comprising at least Cu, Fe and S and flux into an initial molten slag. An oxidation agent is added. An oxygen potential in the range of 10°- 10^-3 Pa is achieved. A submerged oxidation plasma generator and/or a submerged burner is used for these purposes. S is removed from the initial molten slag. The metallic phase is settled and an intermediate molten slag is formed. The reduction (260) comprises heating and agitation of the intermediate molten slag. An oxygen potential in the range of 10^-5- 10^-7 Pa is achieved. A submerged reduction plasma generator is used for these purposes. CU₂O is reduced, metallic Cu is settled in a liquid black copper phase and a final molten slag is formed.

Description

METHOD AND FURNACE EQUIPMENT FOR PRODUCTION OF

BLACK COPPER

TECHNICAL FIELD

The proposed technology generally relates to Cu production and in particular to methods and furnace equipment for production of black copper. BACKGROUND

Production of copper from copper ores typically requires some initial beneficiation into a copper concentrate. Such copper concentrates typically comprises copper in different forms, e.g. copper matte, copper oxides or metallic copper, and are also typically mixed with relatively high amounts of different iron oxides. Impurities such as As, Bi and Pb are also commonly present in copper concentrates.

Smelting and Converting technologies treat copper concentrates in a wide range of chemical and mineralogical compositions to produce slag with high copper contents. The slag cleaning technologies to treat slags or black copper coming out from these furnaces are used today in the copper industry worldwide. There are several operational parameters that determine the economic performance of pyrometalurgical copper production. Copper losses in final slags is one such parameter.

For example, El Teniente Process, see e.g. Reference 1 below, for Copper production is a process widely applied worldwide. Slags from a El Teniente convertor contain between 6- 10% of Cu. 60-80% of this Copper is mainly in a form of Copper matte, accompanied by Copper oxide (10-30%) and metallic Copper inclusions (5- 10%). The amount of Copper oxide depends on the amount of Magnetite in the slag. More Magnetite means more Copper oxide in the slag. Today mainly electric arc furnaces are used for slag cleaning process. Final slag from the electric arc furnace after decopperization shows that there are substantial amounts of remaining copper, in the form of copper matte and metallic copper. The copper matte and copper is present in the final slag in a form of inclusions in sizes 5-50 microns and 5-25 microns, respectively.

SUMMARY

It is an object to provide methods and furnace equipment for efficient separation of copper from copper concentrates.

This and other objects are met by embodiments of the proposed technology.

In general words, according to a first aspect, there is provided a method for production of black copper. The method comprises an oxidation step, forming a metallic phase and an intermediate molten slag from an initial material comprising at least Cu, Fe and S, and a reduction step, forming a liquid black copper phase and a final molten slag from the intermediate molten slag. The oxidation step in turn comprises melting of the initial material and flux, comprising at least S1O2, into an initial molten slag. An oxidation agent, comprising air or oxygen enriched air, is added above the initial molten slag. The initial molten slag is agitated. Oxidation conditions are controlled to give an oxygen potential in the range of 10°- 10-³ Pa. The agitating of the initial molten slag and the controlling of oxidation conditions are jointly performed by operating a submerged oxidation plasma generator and/ or a submerged burner. Thereby at least S is removed from the initial molten slag. The metallic phase, comprising Cu, is settled and the intermediate molten slag, comprising at least CU2O, FeO and S1O2, is formed from the initial molten slag. The reduction step in turn comprises heating of the intermediate molten slag. The intermediate molten slag is agitated. Reduction conditions are controlled to give an oxygen potential in the range of 10-⁵- lO⁷ Pa. The heating of the intermediate molten slag, the agitating of the intermediate molten slag and the controlling of reduction conditions are jointly performed by operating a submerged reduction plasma generator. The operation comprises controlling of power input, plasma gas composition and plasma gas throughput of the submerged reduction plasma generator. Thereby, the CU2O in the intermediate molten slag is reduced to metallic Cu, metallic Cu is settled in the liquid black copper phase and the final molten slag, comprising FeO, is formed from the intermediate molten slag.

According to a second aspect, there is provided a furnace equipment for production of black copper. The furnace equipment has an oxidation reactor and a reduction reactor. The oxidation reactor comprises means for introducing an initial material, comprising at least Cu, Fe and S, and flux, comprising at least S1O2, into the oxidation reactor. A first heater arrangement is configured to melt the initial material and flux into an initial molten slag. The oxidation reactor further comprises means for introducing an oxidation agent, comprising air or oxygen enriched air, above the initial molten slag. The oxidation reactor further comprises a first agitator for agitating the initial molten slag. The oxidation reactor further comprises an oxidation controller, configured to control oxidation conditions giving an oxygen potential in the oxidation reactor in the range of 10⁰-10"³ Pa. The first heater arrangement, the first agitator and the oxidation controller are jointly constituted by a submerged oxidation plasma generator and /or a submerged burner. The oxidation reactor further comprises a fuming outlet. Thereby, at least S is removed from the initial molten slag. Furthermore, a metallic phase, comprising Cu, is settled at a bottom of the oxidation reactor and an intermediate molten slag, comprising at least CU2O, FeO and S1O2, is formed in the oxidation reactor from the initial molten slag. The reduction reactor comprises a second heater arrangement configured for heating the intermediate molten slag and a second agitator for agitating the intermediate molten slag. The reduction reactor further comprises a reduction controller, configured to control reduction conditions giving an oxygen potential in the reduction reactor in the range of 10⁵- 10⁷ Pa. The second heater arrangement, the second agitator and the reduction controller are jointly constituted by a submerged reduction plasma generator. The reduction controller is thereby configured to control power input, plasma gas composition and plasma gas throughput of the submerged reduction plasma generator. CU2O in the intermediate molten slag is reduced into metallic Cu, metallic Cu is settled in the liquid black copper phase at a bottom of the reduction reactor, and a final molten slag, comprising FeO, is formed from the intermediate molten slag. The reduction reactor further comprises a metal outlet for tapping off the liquid black copper phase and a slag outlet for tapping off the final molten slag.

One advantage of the proposed technology is that a black copper with a high Cu concentration is produced, which is suitable for further Cu refinement processes. At the same time, a remaining slag comprises very low Cu content and may be utilized as raw material in iron production.

Other advantages will be appreciated when reading the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments, together with further objects and advantages thereof, may best be understood by making reference to the following description taken together with the accompanying drawings, in which: FIG. 1 is a flow diagram of steps of an embodiment of a method for production of black copper;

FIG. 2 is a flow diagram of part steps of an embodiment of an oxidation step;

FIG. 3 is a flow diagram of part steps of an embodiment of a reduction step;

FIG. 4 is a flow diagram of steps of another embodiment of a method for production of black copper;

FIG. 5 is phase diagram for the Cu-Fe-S-O-SiO₂ system at 1250^°C;

FIG. 6 is a slag phase diagram of the CaO-FeO-SiO2 system;

FIG. 7 is a schematic illustration of an embodiment of a furnace equipment for production of black copper;

FIG. 8 is a schematic illustration of another embodiment of a furnace equipment for production of black copper; and

FIG. 9 is a schematic illustration of yet another embodiment of a furnace equipment for production of black copper. DETAILED DESCRIPTION

Throughout the drawings, the same reference designations are used for similar or corresponding elements.

Copper concentrate denotes in the present disclosure material comprising mainly Cu, Fe and S and minor amounts of elements like As, Bi, Ag, Au etc. The copper concentrates typically comprises different copper sulphide compounds. The copper content could, in dependence on the ores and the concentration processes, amount to 15-60%.

Black copper denotes in the present disclosure a metallic phase comprising mainly copper. The black copper does however typically comprise different impurities making further refining necessary before the copper can be used in most applications. The copper content in black copper could be in the range of 80-98 %.

All percentage figures in the present disclosures are given as % of weight if not stated differently.

By low-viscous slag is in the present disclosure intended a slag that enables easy settling of reduced metal particles. Typically, a low- viscous slag has a viscosity in the range of 1 to 15 Poise. Preferably, low-viscous slags useful for allowing settling of particles have a viscosity in the range of 2 to 10 Poise.

The main approach for reaching an efficient separation of Cu is a two-step process for production of black copper out of Cu-concentrates. The process comprises a melting oxidizing step followed by a reduction step. Both steps are characterized by strongly agitating, preferably by blowing gas into the slag, preferably from plasma torches trough tuyeres, and by controlling the oxidizing - reduction characteristics of the two steps separately. This control is preferably performed by controlling the oxygen potential and temperature of the respective gas streams of the plasma torches. Fig. 1 is a flow diagram of an embodiment of a method for production of black copper. The process starts in step 200. In step 210, in an oxidation step, oxidation is performed, forming a metallic phase and an intermediate molten slag from an initial material comprising at least Cu, Fe and S. The initial material comprises typically Cu concentrates. In step 260, reduction is performed, forming a liquid black copper phase and a final molten slag from said intermediate molten slag. The process ends in step 299. Fig. 2 is a flow diagram of an embodiment of an oxidation step 210 according to Fig. 1.

The oxidation step comprises step 220, where the initial material and flux, comprising at least S1O2, is melted into an initial molten slag. In step 222, an oxidation agent, comprising air or oxygen enriched air, is added above the initial molten slag. In step 224, the initial molten slag is agitated. In step 226, it is performed a controlling of oxidation conditions giving an oxygen potential in the range of 10°-10 ³ Pa. These part steps are typically performed at least partly overlapping in time and are typically performed as essentially simultaneous part processes.

As caused by the oxygen potential, is removed from the initial molten slag. As will be discussed further below, also other impurities may be fumed off. The removal of the S thus counteracts formation of any matte phases. The removed S is then oxidized, typically into SO2, by the oxidation agent in the atmosphere above the surface of the initial molten slag, and can be removed together with remaining exhaust gases. The SO2 may then be separated from the exhaust gas by conventional methods. In order to have an efficient combustion of sulphur, air or oxygen enriched air is preferably introduces just above the surface of the molten slag.

The oxygen potential also causes a part of the copper in the initial material to oxidize into CU₂O and a major part of the iron in the initial material appears as FeO. This leads to that the initial molten slag is turned into an intermediate molten slag, comprising at least C112O, FeO and S1O₂. This intermediate molten slag is thus preferably of a Fayalite type.

A part of the copper in the initial material is also reduced into metallic Cu. The metallic Cu typically appears in small droplets and depending on the size of the droplets and the viscosity of the slag, some of the metallic Cu is settled as a metallic phase in the bottom of the vessel in which the oxidation takes place. Such a metallic phase may comprise 99% Cu. A part of the metallic Cu, in particular in small droplets, may however remain in the intermediate molten slag phase. The intermediate molten slag thus comprise, in a typical case, minor amounts of metallic Cu together with the Cu₂0 and FeO. The above described processes are dependent on the oxidation conditions and on a thorough mixing of the slag. A vigorous agitation of the slag and well controlled oxidations conditions are therefore of importance. One way to ensure that a vigorous agitation and well controlled oxidation conditions are maintained is to introduce gas in a submerged manner into the slag. The agitating of the initial molten slag and the controlling of oxidation conditions are, as indicated by step 230, jointly performed by operating a submerged oxidation plasma generator and /or a submerged burner. The gas bubbling through the slag ensures a mixing of the components, possibilities for e.g. S to fume off and facilitates for equalization of oxidation conditions throughout the reaction vessel.

As indicated by the dotted extension 231, the operation of the submerged oxidation plasma generator and/ or a submerged burner may also contribute to at least a part of the melting of the initial material. The combustion of S into SO₂ is a highly exothermic reaction, and the oxidation of sulfur into sulfur dioxide therefore produces large amounts of heat. Heat generated by such a reaction also contributes to the melting of subsequently introduced initial material. For particular compositions of Cu concentrates and fluxes, such combustion heat may even be sufficient to melt further introduced Cu concentrates completely.

The oxidation step thus removes the sulphur from the Cu concentrates, counteracting any formation of Cu matte phases, and at the same time the Fe is kept in a basically Fayalite form which gives an easily handled slag. The oxidation step produces certain amounts of settled high purity Cu collected at the bottom of the reactor, but part of the Cu remains in slag as oxide or as small metallic droplets.

In an example embodiment, a Cu concentrate, comprising different sulphates of copper was used. One example of a Cu concentrate comprised 28-30% Cu, 30-32% S, 5- 10% FeO₂ and 37-38% FeO and minor amounts of As and Bi, was used as an initial material. Flux comprising S1O2 was introduced together with the initial material. The initial material comprising Cu, Fe, S and As was melted into an initial molten slag. The initial molten slag was agitating by a submerged jet of hot gas. In this particular embodiment a plasma generator was used for producing the gas. However, in alternative embodiments, other types of submerged burners can be utilized, e.g. an oxyfuel burner. The strong bath agitation promotes a high gas/ melt surface ratio which promotes excellent fuming set by the mass transfer from the interior of the melt to the gas phase. The exhaust gas from the oxidation process comprised in this embodiment mainly SO2, H2O, ¾, CO₂, CO, As and Bi.

In a particular embodiment, the method further comprises fuming off and/ or oxidizing of As, evaporable metals and/ or evaporable metal compounds. In a further particular embodiment, the evaporable metals comprise Bi and/ or Pb. The introduced hot gas was controlled to have required enthalpy for assisting in the melting and keeping the molten slag at an appropriate temperature. An oxygen potential of PO2 = 10^"1 - IO-³ Pa was in this embodiment maintained in the reactor volume, by controlling the oxygen potential in the introduced submerged jet of hot gas. The oxygen potential of the introduced submerged jet of hot gas and the oxygen potential contribution of the added air or oxygen enriched air together determines the overall oxidation conditions. The oxygen potential ensured that S, As and Bi and at least a part of other evaporable metals and/ or evaporable metal compounds were fumed off from the molten slag and/ or oxidized. The oxygen potential also caused a partial reduction of CuO from the slag to a metallic phase while keeping most of the Fe in the slag as FeO bounded to S1O2 as Fayalite. Fayalite type slags have melting temperatures in the range of 1250°C. If the heat introduced for melting the initial material and the heat produced by the oxidation of sulphur is not sufficient to maintain the slag in a low-viscous condition, additional heating may be necessary. In one embodiment, the oxidation step 210 further comprises heating 228 of the initial molten slag and the controlling 226 of oxidation conditions further comprises controlling of the heating of the initial molten slag to give a low-viscous intermediate molten slag.

As mentioned in the particular embodiment above, the enthalpy and oxygen potential may be controlled by further introducing hot gases. These hot gases may in certain embodiments possibly comprising oxidizing or reducing agents. In other words, the step of controlling 226 of oxidation conditions comprises in particular embodiments introduction of oxidizing agents and/ or reducing agents into the initial molten slag.

In a preferred embodiment, plasma generators are used for heating in excess of the sulfur combustion heat, the agitation and the control of the oxidation conditions. In other words, the agitating of the initial molten slag, the heating of the initial molten slag and the controlling of oxidation conditions, and optionally also the melting of the initial material, are jointly performed by operation of a submerged oxidation plasma generator. The operation comprises controlling of power input, plasma gas composition and plasma gas throughput of said submerged oxidation plasma generator. Fig. 3 is a flow diagram of an embodiment of a reduction step 260 according to Fig. 1.

In this embodiment, the reduction step 260 in turn comprises, in step 270, heating of the intermediate molten slag. In step 272, the intermediate molten slag is agitated. In step 274, it is performed a control of reduction conditions giving an oxygen potential in the range of 10"⁵-10"⁷ Pa. These part steps are typically performed at least partly overlapping in time and are typically performed as essentially simultaneous part processes.

A vigorous agitation of the slag, a controlled temperature and well controlled reduction conditions are, in analogy with the oxidation step, of importance. One way to ensure that a vigorous agitation and well controlled reduction conditions are maintained is to introduce gas of a well-controlled composition and with a well-controlled enthalpy in a submerged manner into the slag. The heating of the intermediate molten slag, the agitating of the intermediate molten slag and the controlling of reduction conditions are jointly performed by operation of a submerged reduction plasma generator. In a plasma generator, the supplied electric energy is easily controlled and corresponds to the enthalpy that is introduced into the plasma gas. The amount of gas passing the plasma generator into the slag is also a parameter that is easy to regulate. These properties of the plasma generator makes it a very suitable tool for methods requiring controlled heat supply and chemical composition conditions. The operation of the submerged reduction plasma generator thus comprises controlling of power input, plasma gas composition and plasma gas throughput of the submerged reduction plasma generator. The gas bubbling through the slag ensures a mixing of the components, possibilities for droplets of metallic Cu to settle, as will be discussed further below, and facilitates for equalization of reduction conditions throughout the reaction vessel.

The reduction conditions cause the remaining CU2O in the intermediate molten slag to be reduced to metallic Cu. This metallic Cu, together with the metallic Cu that was already present in the intermediate molten slag from the oxidation stage, is settled in a liquid black copper phase at the bottom of the 016 050355

1 1

reaction vessel. At the same time a final molten slag, comprising FeO, is formed from the intermediate molten slag.

By using the above presented reduction conditions, the transformation of Cu into a metallic form can be driven almost completely. Furthermore, the vigorous agitation furthermore allows an almost complete separation of the created Cu as metal droplets settling through the slag. At the same time, the iron is maintained in an easily handed Fayalite form. The Cu content in the black copper phase may be as high as over 90 %, and impurities of S and As are present only on extremely low levels. In test runs, the black copper phase contained less than 0. 1% of S and less than 0.5 % of As. This black copper phase thus constitutes an ideal raw material for further Cu refining operations. The remaining final molten slag, comprising iron, becomes at the same time almost depleted from Cu. The remaining copper concentration in this final molten slag may be as low as 0.5 % and in certain tests levels of 0.2-0.3 % has even been reached. Impurities, such as S and As are also kept at a low level. In test runs, the final molten slag contained less than 0. 1% of both As S.

In a particular embodiment, the intermediate molten slag from the example embodiment of the oxidation step described above was used. The heat balance of the reactor, the oxygen potential and the strong bath agitation was controlled the by submerged plasma generators. The enthalpy of the gas introduced from the Plasma Generators (PG) is set to balance the heat system. The reduction of Cu is an endothermic process and requires supply of heat to maintain the temperature. Furthermore, the required oxygen potential is set to be favourable to keep the Fe in the slag phase as FeO and thereby hindering formation of Fe3O4. Oxygen potential of the gas coming from the PG is set to give a system oxygen potential of PO2 = 10^~5 - 10 ⁷ Pa. At the same time, the oxygen potential is set to favour reducing and of the Copper into a metallic form. The metallic Cu being present in the intermediate molten slag is settled into the black copper phase, assisted by the agitation. The strong bath agitation promotes coalescence of very small copper droplets in the slag. These larger particles will then overcome the critical radius and will be prone to sink into the reactor bottom. The control of the oxygen potential may be fully controlled by the operation of the composition of the plasma generator gas. Introduction of hydrocarbons or other types of reducing agents in the plasma gas can be used. Alternatively, at least some reducing agents may be introduced into the intermediate molten slag by other means, e.g. by adding coal onto the surface of the intermediate molten slag.

In one particular embodiment, the controlling of reduction conditions comprises introduction of reducing agents into the intermediate molten slag. As a result of the reduction processes, exhaust gases are produced. The exhaust gas from the reduction process comprised in the example embodiment is mainly H20, ¾, CO2 and CO.

By having Fe3O₄, or rather the mitigation of Fe3O₄, under full control during the reduction phase means that one has full control over the slag viscosity. The viscosity decreases with decreasing Fe3O4 content in the slag and therefore the use of Fayalite-type slags enhances the possibilities for metallic droplets to settle. Such reduction condition control together with the temperature control ensures that a low-viscous final molten slag is produced.

In one particular embodiment, the controlling of reduction conditions further comprises controlling of the heating of the intermediate molten slag to give a low-viscous final molten slag.

Transferring the liquid slag into the reduction zone of the reactor or to a separate reactor; The total process can be performed as a batch process in a single reactor, or in two reactors, as well as a continuous process in one or two reactor designs. Fig. 4 is a flow diagram of another embodiment of a method for production of black copper. The steps 210 and 260 are similar to the embodiment of Fig. 1. Between these two steps, a step 250 is introduced, in which the intermediate molten slag is transferring from an oxidation reactor or an oxidation reactor zone to a reduction reactor or a reduction reactor zone. The oxidation step is then performed in the oxidation reactor or the oxidation reactor zone and the reduction step is then performed in the reduction reactor or the reduction reactor zone.

Fig. 5 illustrates schematically the Cu-Fe-S-0-SiO2 system at 1250^°C. The two part processes takes place in different parts of this chemical system. In the smelting and oxidation stage, the system is kept at an oxygen potential of 10°- 10"³ Pa as indicated by the marked area 300. In this area, the formation of CU₂S is disfavoured in comparison with formation of CU2O or metallic Cu. At the same time, at least a part of the iron is in a Fayalite form. The sulphur content will be continuously decreased due to the fuming off and oxidation of sulphur to sulphur dioxide, driving the conditions to the left in the figure.

In a preferred embodiment, the oxygen potential in the oxidizing step is kept in the range of lO-ⁱ- lO ³ Pa.

In an even more preferred embodiment, the oxygen potential in the oxidizing step is kept in the range of 10"²-10"³ Pa.

During the reduction step, the oxygen potential is drastically reduced to 10^~5- IO-⁷ Pa as indicated by the marked area 302, which favours reduction of CU2O to metallic Cu and hinders formation of metallic Fe. A more or less complete reduction of the CU₂O can be achieved. The sulphur content is now low and the iron is still in a Fayalite form. An example of the CaO-FeO-Si02 system used in connection with the example embodiment above is schematically illustrated in Fig. 6. Depending on the composition of the Cu concentrate and the amount and composition of the flux, the slag compositions that at the present are believed to be the most favourable are marked by the marked area 304. Here, a fayalite-type of slag is present, which has a relatively low melting temperature and which is generally low-viscous. The low viscosity enables easy settling of reduced metal particles. Fig. 7 is a schematic illustration of an embodiment of a furnace equipment 1 for production of black copper. An oxidation reactor 10, comprises means 12 for introducing an initial material 14, comprising at least Cu, Fe and S, and flux 16, comprising at least S1O2, into the oxidation reactor 10. Such means 12 for introducing may be designed according to standard prior art feeding equipment for furnace applications, well-known by any person skilled in the art. The details of such means are not essential for the process described in the present disclosure and are therefore not further described. A first heater arrangement 18 is configured to melt the initial material 14 and flux 16 into an initial molten slag 45.

The oxidation reactor 10 further comprises means 24 for introducing an oxidation agent 26, comprising air or oxygen enriched air, above the initial molten slag 45. Such means 24 for introducing may be designed according to standard prior art feeding equipment for furnace applications, well-known by any person skilled in the art. The details of such means are not essential for the process described in the present disclosure and are therefore not further described. In the present embodiment, the means 24 for introducing an oxidation agent 26 is combined with the means 12 for introducing an initial material 14, however, in alternative embodiments, the introduction means may be separate. A first agitator 20 is arranged for agitating the initial molten slag 45. The oxidation reactor 10 further comprises an oxidation controller 22. The oxidation controller 22 is configured to control oxidation conditions in the oxidation reactor 10 to give an oxygen potential in the oxidation reactor 10 in the range of 10⁰- 10^~3 Pa. Preferably, the oxidation controller is further configured to control introduction of oxidizing agents into the initial molten slag.

The first heater arrangement 18, the first agitator 20 and the oxidation controller 22 are jointly constituted by a submerged oxidation plasma generator 40. In an alternative embodiment, they may be constituted by a submerged burner or a combination. The submerged oxidation plasma generator 40 provides a stream of hot gases 46 into the initial molten slag 45, thereby causing a heating of the initial molten slag 45 and a vigorous agitation of the initial molten slag 45, when the gas 46 bubbles upwards through the initial molten slag 45. Hydrocarbons 42 may be used as one part of the plasma generator gas.

In a preferred embodiment, the oxidation controller is configured to control power input, plasma gas composition and plasma gas throughput of the submerged oxidation plasma generator.

Due to the temperature and oxygen potential conditions in the oxidation reactor 10, at least S, and possibly also other impurities such as As, or evaporable metals or evaporable metal compounds, is removed from the initial molten slag 45 and oxidized by the oxidation agent 26. The exhaust gases 28 are leaving the oxidation reactor 10 by a fuming outlet 30. The exhausts can be cleaned according to well-known prior art principles. The processes in the slag are facilitates by a low-viscous slag. Therefore, preferably, the oxidation controller is further configured to control heating of the initial molten slag to give a low-viscous intermediate molten slag.

Due to the oxidation conditions, a metallic phase 32, comprising Cu, is settled at a bottom 34 of the oxidation reactor 10. An intermediate molten slag 50, comprising at least CU2O, FeO and S1O2, is formed in the oxidation reactor 10 from the initial molten slag 45. This intermediate molten slag 50 is allowed to be transferred, continuously or intermittently, through a transfer connection 52 between the oxidation reactor 10 and a reduction reactor 60 for allowing at 50355

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least one of continuous and intermittent transfer of the intermediate slag from the oxidation reactor to the reduction reactor.

The reduction reactor 60 comprises a second heater arrangement 62 configured for heating the intermediate molten slag 50. A second agitator 64 is provided for agitating the intermediate molten slag 50. Furthermore, a reduction controller 66 is configured to control reduction conditions. This control gives an oxygen potential in the reduction reactor 60 in the range of lO-⁵- 10-7 Pa.

In analogy with the arrangements in the oxidation reactor, the second heater arrangement 62, the second agitator 64 and the reduction controller 66 are jointly constituted by a submerged reduction plasma generator 90. Thereby, the reduction controller 66 is configured to control power input, plasma gas composition and plasma gas throughput of the submerged reduction plasma generator 90. The submerged reduction plasma generator 90 produces a jet of hot gas 84, which will bubble up through the intermediate molten slag 50 causing the agitation thereof. Hydrocarbons 84 may be introduced through the submerged reduction plasma generator 90, as one component for controlling the oxygen potential. In other words, the reduction reactor further comprises means for introduction of reducing agents into the intermediate molten slag.

Alternatively, or as a complement, introduction of reducing agents 82, such as e.g. coal or hydrocarbons, can be added directly into the reduction reactor 60 through an inlet 80.

The reduction processes produces different exhaust gases 78, such as CO, CO2, H2 and H2O. Such exhaust gases 78 are allowed to exit the reduction reactor through an exhaust outlet 80.

Due to the oxygen potential conditions in the reduction reactor 60, C 2O in the intermediate molten slag is reduced into metallic Cu. Metallic Cu in the intermediate molten slag, either formed by the process in the reduction reactor 60 or as being brought with the intermediate molten slag from the oxidation reactor 10, is settled in a liquid black copper phase 68 at a bottom 70 of the reduction reactor 60. A low-viscous slag will, as discussed further above, facilitate the settling procedure, and therefore preferably the reduction controller is further configured to control the second heater arrangement to give a low-viscous final molten slag.

The reduction reactor 60 is further equipped with a metal outlet 72 for tapping off the liquid black copper phase 68.

A final molten slag 95 is also from the intermediate molten slag 50 by these processes. The final molten slag 95 comprises FeO. The reduction reactor 60 is further equipped with a slag outlet 76 for tapping off the final molten slag 95.

Fig. 8 illustrates schematically another embodiment of a furnace equipment 1 for production of black copper. In this embodiment, the oxidation reactor 10 is an oxidation zone 11 of a furnace 5 and the reduction reactor 60 is a reduction zone 61 of the furnace 5. The furnace 5 is arranged for continuously transferring, as illustrated by the arrow 51, the intermediate slag 50 from the oxidation zone 11 to the reduction zone 61.

The copper concentrate 14 and flux 16 are introduced into the oxidation zone 11 together with an oxidation agent 26, comprising air or oxygen enriched air. A number of submerged oxidation plasma generators 40 melts the incoming material into the initial molten slag 45 and S is allowed to leave the initial molten slag 45 and being oxidized by the oxidation agent 26. The then formed intermediate molten slag 50 is transferred over to the reduction zone 61, where coke 82 may be added to change the reduction conditions. A number of submerged reduction plasma generators 90 are used for controlling the oxygen potential and the temperature of the intermediate molten slag 50 during its conversion into the final molten slag. The reduced Cu metal settles into the bottom of the furnace 5 as a metallic black copper phase 68 and may be tapped out. The process may also be operated in a batch-wise manner, which allows for using a single furnace as both an oxidation and reduction reactor. Fig. 9 illustrates schematically an embodiment of a furnace equipment 1 for production of black copper according to such ideas. In this embodiment, the oxidation reactor 10 and the reduction reactor 60 are constituted by a same furnace 6, the first heater arrangement 18 and the second heater arrangement 62 are a same heater arrangement 17, and the first agitator 20 and the second agitator 64 are a same agitator 19. The oxidation controller 22 and reduction controller 66 are configured to operate consecutive in time, thereby giving an oxidation process followed by a reduction process in a batch manner.

In other words, the furnace 6 is first operated as an oxidation reactor 10, in which a metallic phase and an intermediate molten slag are formed from an initial material comprising at least Cu, Fe and S. When this process is finished, the intermediate molten slag is kept in the furnace 6, while the operation conditions are changed into a reduction reactor 60 instead. During the reduction process, a liquid black copper phase and a final molten slag are formed from the intermediate molten slag. The final products are tapped out from the furnace 6.

The embodiments described above are merely given as examples, and it should be understood that the proposed technology is not limited thereto. It will be understood by those skilled in the art that various modifications, combinations and changes may be made to the embodiments without departing from the present scope as defined by the appended claims. In particular, different part solutions in the different embodiments can be combined in other configurations, where technically possible. REFERENCES

1. I. Imris, M. Sanchez and G. Achurra: Copper losses to slags obtained from El Teniente process. VII International Conference on Molten Slags Fluxes and Salts, The South African Institute of Mining and Metallurgy,

Claims

1. A method for production of black copper, comprising:

an oxidation step (210), forming a metallic phase (32) and an intermediate molten slag (50) from an initial material (14) comprising at least Cu, Fe and S;

said oxidation step (210) in turn comprises:

- melting (220) said initial material (14) and flux (16), comprising at least S1O2, into an initial molten slag (45);

- adding (222) an oxidation agent (26), comprising air or oxygen enriched air, above said initial molten slag (45);

- agitating (224) said initial molten slag (45); and

- controlling (226) of oxidation conditions giving an oxygen potential in the range of 10°- 10^"3 Pa;

said agitating (224) of said initial molten slag (45) and said controlling

(226) of oxidation conditions are jointly performed by operation (230) of at least one of a submerged oxidation plasma generator (40) and a submerged burner;

whereby at least S is removed from said initial molten slag (45); and whereby said metallic phase (32), comprising Cu, is settled and said intermediate molten slag (50), comprising at least CU2O, FeO and S1O2 is formed from said initial molten slag (45); and

a reduction step (260), forming a liquid black copper phase (70) and a final molten slag (95) from said intermediate molten slag (50);

said reduction step (260) in turn comprises:

- heating (270) said intermediate molten slag (50);

- agitating (272) said intermediate molten slag (50);

- controlling (274) of reduction conditions giving an oxygen potential in the range of 10^~5-10^~7 Pa;

said heating (270) of said intermediate molten slag (50), said agitating

(272) of said intermediate molten slag (50) and said controlling (274) of reduction conditions, are jointly performed by operation (280) of a submerged reduction plasma generator (90); wherein said operation (280) comprises controlling of power input, plasma gas composition and plasma gas throughput of said submerged reduction plasma generator (90).

whereby said CU2O in said intermediate molten slag (50) is reduced to metallic Cu and metallic Cu is settled in said liquid black copper phase (70) and said final molten slag (95), comprising FeO, is formed from said intermediate molten slag (50).

2. The method according to claim 1, characterized in that said controlling (274) of reduction conditions further comprises controlling of said heating of said intermediate molten slag (50) to give a low-viscous final molten slag.

3. The method according to claim 1 or 2, characterized in that said controlling (274) of reduction conditions comprises introduction of reducing agents (84) into said intermediate molten slag.

4. The method according to any of the claims 1 to 3, characterized in that said oxidation step (210) further comprises heating (228) of said initial molten slag (45) and said controlling (226) of oxidation conditions further comprises controlling of said heating (228) of said initial molten slag (45) to give a low- viscous intermediate molten slag (50).

5. The method according to any of the claims 1 to 4, characterized in that said controlling (226) of oxidation conditions comprises introduction (42) of oxidizing agents and/ or reducing agents into said initial molten slag (45).

6. The method according to claim 5, characterized in that said agitating (224) of said initial molten slag (45), said heating (228) of said initial molten slag (45) and said controlling (226) of oxidation conditions are jointly performed by operation (230) of a submerged oxidation plasma generator (40), wherein said operation (230) comprises controlling of power input, plasma gas composition and plasma gas throughput of said submerged oxidation plasma generator (40).

7. The method according to any of the claims 1 to 6, characterized in that said oxidation step (210) is performed in an oxidation reactor (10) or an oxidation reactor zone (1 1) and said reduction step (260) is performed in a 5 reduction reactor (60) or a reduction reactor zone (61) and by further comprising:

- transferring (250) said intermediate molten slag (50) from said oxidation reactor (10) or said oxidation reactor zone (1 1) to said reduction reactor (60) or said reduction reactor zone (61).

10

8. The method according to any of the claims 1 to 7, characterized by further comprising at least one of oxidizing and fuming off of at least one of:

As;

evaporable metals; and

15 evaporable metal compounds.

9. The method according to claim 8, characterized in that said evaporable metals comprises at least one of Bi and Pb.

20 10. A furnace equipment (1) for production of black copper, having:

an oxidation reactor (10), comprising:

means (12) for introducing an initial material (14), comprising at least Cu, Fe and S, and flux (16), comprising at least S1O2, into said oxidation reactor (10);

25 a first heater arrangement (18) configured to melt said initial material (14) and flux (16) into an initial molten slag (45);

means (24) for introducing an oxidation agent (26), comprising air or oxygen enriched air, above said initial molten slag (45);

a first agitator (20) for agitating said initial molten slag (45);

30 an oxidation controller (22), configured to control oxidation conditions giving an oxygen potential in said oxidation reactor (10) in the range of 10⁰- 10^"3 Pa; said first heater arrangement (18), said first agitator (20) and said oxidation controller (22) are jointly constituted by at least one of a submerged oxidation plasma generator (40) and a submerged burner;

and

a fuming outlet (30);

whereby at least S is removed from said initial molten slag (45); and whereby a metallic phase (32), comprising Cu, is settled at a bottom (34) of said oxidation reactor (10) and an intermediate molten slag (50), comprising at least CU2O, FeO and S1O2, is formed in said oxidation reactor (10) from said initial molten slag (45); and

a reduction reactor (60), comprising:

a second heater arrangement (62) configured for heating said intermediate molten slag (50);

a second agitator (64) for agitating said intermediate molten slag (50);

a reduction controller (66), configured to control reduction conditions giving an oxygen potential in said reduction reactor (60) in the range of 10-⁵-10-⁷ Pa;

said second heater arrangement (62), said second agitator (64) and said reduction controller (66) are jointly constituted by a submerged reduction plasma generator (90);

wherein said reduction controller (66) is configured to control power input, plasma gas composition and plasma gas throughput of said submerged reduction plasma generator (90);

whereby CU2O in said intermediate molten slag (50) is reduced into metallic Cu, metallic Cu is settled in said liquid black copper phase (68) at a bottom (70) of said reduction reactor (60), and wherein a final molten slag (95), comprising FeO, is formed from said intermediate molten slag (50);

said reduction reactor (60) further comprises:

a metal outlet (72) for tapping off said liquid black copper phase

(68); and

a slag outlet (76) for tapping off said final molten slag (95).

11. The furnace equipment according to claim 10, characterized in that said reduction controller (66) is further configured to control said second heater arrangement (62) to give a low- viscous final molten slag (95).

5 12. The furnace equipment according to claim 10 or 11, characterized in that said reduction reactor (60) further comprises means for introduction of reducing agents (84) into said intermediate molten slag (50).

13. The furnace equipment according to any of the claims 10 to 12, 10 characterized in that said oxidation controller (22) is further configured to control heating of said initial molten slag (45) to give a low-viscous intermediate molten slag.

14. The furnace equipment according to any of the claims 10 to 13, 15 characterized in that said oxidation controller (22) is further configured to control introduction of oxidizing agents (42) into said initial molten slag (45).

15. The furnace equipment according to claim 14, characterized in that said first heater arrangement (18), said first agitator (20) and said oxidation 20 controller (22) are jointly constituted by a submerged oxidation plasma generator (40), wherein said oxidation controller (22) is configured to control power input, plasma gas composition and plasma gas throughput of said submerged oxidation plasma generator (40).

25 16. The furnace equipment according to any of the claims 10 to 15, characterized in that said oxidation reactor (10) is an oxidation zone (11) of a furnace (5) and said reduction reactor (60) is a reduction zone (61) of said furnace (5), said furnace (5) being arranged for continuously transferring said intermediate molten slag (50) from said oxidation zone (11) to said reduction

30 zone (61).

17. The furnace equipment according to any of the claims 10 to 15, characterized by further comprising a transfer connection (52) between said oxidation reactor (10) and said reduction reactor (60) for allowing at least one of continuous and intermittent transfer of said intermediate molten slag (50) from said oxidation reactor (10) to said reduction reactor (60).

18. The furnace equipment according to any of the claims 10 to 15, characterized in that said oxidation reactor (10) and said reduction reactor (60) are constituted by a same furnace (6), said first heater arrangement (18) and said second heater arrangement (62) are a same heater arrangement (17), said first agitator (20) and said second agitator (64) are a same agitator (19), whereby said oxidation controller (22) and reduction controller (66) are configured to operate consecutive in time, thereby giving an oxidation process followed by a reduction process in a batch manner.