METHOD FOR PRODUCING CATHODE COPPER

Abstract

Provided is a method for producing cathode copper. The method comprises a smelting step including feeding sulfidic copper bearing material and oxygen-bearing reaction gas into a suspension smelting furnace, to produce blister copper, a fire refining step including feeding blister copper into an anode furnace to produce molten anode copper, an anode casting step to produce cast anodes, a quality checking step for dividing cast anodes into accepted cast anodes and rejected cast anodes, an electrolytic refining step including subjecting accepted cast anodes to electrolytic refining in an electrolytic cell to produce cathode copper and as a by-product, spent cast anodes, and a recycling step for recycling anode copper of rejected cast anodes and anode copper of spent cast anodes.

Description

FIELD OF THE INVENTION

The invention relates to a method for producing cathode copper as defined in the preamble of independent claim 1.

A known production method for production of cathode copper, having a purity of more than 99.9%, from copper concentrate involves firstly smelting sulfidic copper concentrate in first pyrometallurgical phase in a first suspension smelting furnace by partial oxidation of the copper concentrate to obtain a copper matte phase that is further oxidized in a second pyrometallurgical phase in a second suspension smelting furnace to metallic copper i.e. blister copper. A production method using a first and a second suspension smelting furnace is sometimes named a double flash process. Alternatively, sulfidic copper concentrate may be directly smelted to metallic copper i.e. blister copper in a direct-to-blister process in one single pyrometallurgical phase that is performed in one single suspension smelting furnace. In both alternatives, the blister copper obtained is further refined in anode furnaces by fire-refining to obtain molten anode copper, which is poured into anode molds to cast copper anodes. This known production method for production of cathode copper involves additionally further subjecting cast anodes to electrolytic refining in electrolytic cells to produce cathode copper.

Anode scrap is obtained in the production of cathode copper in two stages. Spent cast anodes from electrolytic refining constitute the primary source for anode scrap. In addition, some of the cast anodes produced in the anode casting step do not meet certain quality requirements and are therefore rejected. Spent cast anodes and rejected cast anodes contains in terms of mass percentages approximately 99% copper and this is about 15 to 20% of total mass of the primary copper produced. Therefore this material must be recycled.

Traditionally, in smelters that utilize Peirce-Smith (PS) converting, the spent cast anodes and the rejected cast anodes have been fed to the PS-converters. It is easy to feed the spent cast anodes and the rejected cast anodes there and the excess heat produced by the converting reactions is more than enough for melting the spent cast anodes and the rejected cast anodes.

In modern suspension smelting furnaces such as in double flash and direct-to-blister furnaces, the option to feed anode scrap to converters are not available, as these furnaces are not Peirce-Smith converters. The usual solution has therefore to provide a separate furnace for smelting spent cast anodes and rejected cast anodes by using heat from burning fossil fuels. FIG. 1 shows an example of a method according to the prior art, which method involves direct-to-blister smelting.

The method for producing anode copper shown in FIG. 1 comprises a smelting step including feeding sulfidic copper bearing material 1, oxygen-bearing reaction gas 2 and slag-forming material 3 such as flux into a reaction shaft 4 of a suspension smelting furnace 5 by means of a burner 6 that is arranged at a top of the reaction shaft 4 of the suspension smelting furnace 5, whereby feeding sulfidic copper bearing material 1, oxygen-bearing reaction gas 2 and slag-forming material 3 react in the reaction shaft 4 into blister copper 7 and slag. Blister copper 7 and slag 8 is collected in a settler 11 of the suspension smelting furnace 5 to foul′ a blister layer 9 containing blister copper 7 and a slag layer 10 containing slag 8 on top of the blister layer 9 in the settler 11 of the suspension smelting furnace 5.

The method shown in FIG. 1 comprises a fire refining step including feeding blister copper 7 obtained in the smelting step into an anode furnace 12 and fire-refining blister copper in the anode furnace 12 to produce molten anode copper 13 in the anode furnace.

The method shown in FIG. 1 comprises an anode casting step including feeding anode copper 13 obtained in the fire refining step into anode casting molds 14 to produce cast anodes 15.

The method shown in FIG. 1 comprises a quality checking step 16 for dividing the cast anodes 15 obtained in the anode casting step into accepted cast anodes 17 and rejected cast anodes 18.

The method shown in FIG. 1 comprises an electrolytic refining step for subjecting accepted cast anodes 17 to electrolytic refining in an electrolytic cell 19 to produce cathode copper 20, and as a by-product, spent cast anodes 21.

The method shown in FIG. 1 comprises a recycling step for recycling anode copper of rejected cast anodes 18 and anode copper of spent cast anodes 21. More precisely, the recycling step of the method according to the prior art method shown in FIG. 1 comprises feeding rejected cast anodes 18 and spent cast 21 into a separate scrap melting furnace 22 for smelting rejected cast anodes 18 and spent cast anodes 21 in the scrap melting furnace 22 and feeding copper anode smelt 23 from the scrap melting furnace 22 into anode casting molds 14 to produce cast anodes 15.

In the solution shown in FIG. 1, rejected cast anodes 18 and spent cast anodes 21 are melted in the shaft furnace 22 to make new cast anodes 15 of the material of rejected cast anodes 18 and spent cast anodes 21. This is a simple solution that achieves the goal of recovering the copper from of rejected cast anodes 18 and spent cast anodes 21. The disadvantages of a such prior art solution are the expenses to build and to operate the separate scrap melting furnace 22. Also from energy consumption and greenhouse gas emission point of view, this known solution cannot be considered to be good.

Publication WO 2013/186440 A1 presents a method and an arrangement for refining copper concentrate.

Publication JP 2000 239883 A presents a method for recycling anode returning material for casting, and the like, in copper refining, and charging device of anode returning material for casting, and the like, into refining furnace.

Publication JP H09 781 51 A presents a recycle method of valuable metals from scraps.

Publication WO 2004/005822 A1 presents a method and an arrangement for feeding an anode into a smelter.

OBJECTIVE OF THE INVENTION

The object of the invention is to provide an efficient method for refining copper concentrate.

SHORT DESCRIPTION OF THE INVENTION

The method for refining copper concentrate of the invention is characterized by the definitions of independent claim 1.

Preferred embodiments of the method are defined in the dependent claims.

The invention is based on using the excess thermal energy produced in the reactions in the suspension smelting furnace to smelt rejected cast anodes and spent cast anodes. In suspension smelting processes such as in double flash and direct-to-blister process, there is often a surplus of heat produced in the oxidation reactions in the suspension smelting furnaces, meaning that the reactions produce more heat than is required for smelting the copper concentrate. This is especially true with declining ore grades, since a decline in copper grade is usually accompanied by and incline in Fe and S contents, resulting in more reaction heat. Quite often the excess of thermal energy can even be a problem, causing a bottleneck in the suspension smelting furnace. In such case the objective of the invention is both to recycle the anode scrap efficiently and to absorb excess heat in the reaction shaft.

More precisely, in the method rejected cast anodes and spent cast anodes are mechanically broken to produce anode copper grain of rejected cast anodes and spent cast anodes, and the anode copper grain is fed into the reaction shaft of the suspension smelting furnace. The goal is that the anode copper grains are smelted on their way down from the upper part of the reaction shaft of the suspension smelting furnace to the settler of the suspension smelting furnace and not in the settler of the suspension smelting furnace. For this reason, the anode copper grain is preferably, but not necessarily, fed from the roof structure of the reaction shaft into the reaction shaft to enable sufficient time for the copper grains in the reaction shaft to melt. Even if the goal of melting the anode scrap in the reaction shaft is not completely reached, the anode copper grain will be significantly heated in the reaction shaft, thus lowering the cooling effect that melting it will have on the furnace settler.

If the suspension smelting furnace is run with reduced oxygen enrichment to counter the extra heat in the copper concentrate, the heat for smelting the anode scrap may be provided by increasing the oxygen enrichment in the suspension smelting furnace. This increases the technical oxygen consumption. In locations where oxygen is significantly cheaper than natural gas, this is a significant saving in operation costs. Consuming oxygen is also more sustainable than burning fossil fuels considering both the environmental impact and the availability of Earth's finite resources. Utilizing higher oxygen enrichment also results in smaller volume of gas in the suspension smelting process, reducing certain costs of the process.

If there is extra thermal energy in the copper concentrate, but the burner needs to be run with maximum oxygen enrichment because of bottlenecks in the off-gas line, absorbing the heat of the concentrate can be a limiting factor for the rate of production. In this case, smelting anode scrap will not result in increased energy consumption of any form in the suspension smelting furnace. On contrary, the cooling effect introduced can help in increasing the production rate in the suspension smelting furnace.

LIST OF FIGURES

In the following the invention will described in more detail by referring to the figures, of which

FIG. 1 is a schematic illustration showing the principle of a method according to the prior art

FIG. 2 is a schematic illustration showing the principle of a first embodiment of the method,

FIG. 3 is a schematic illustration showing a second embodiment of the method,

FIG. 4 is a schematic illustration showing the principle of a third embodiment of the method,

FIG. 5 is a schematic illustration showing a fourth embodiment of the method, and

FIG. 6 is a schematic illustration showing a fifth embodiment of the method.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 2 to 6 show some embodiments of the method for producing cathode copper.

The method comprises a smelting step including feeding sulfidic copper bearing material 1; 1a, 1b such as sulfidic copper concentrate 1a or finely-ground copper matte 1b and additionally oxygen-bearing reaction gas 2 and slag-forming material 3 such as flux into a reaction shaft 4 of a suspension smelting furnace 5; 5a, 5b by means of a burner 6 that is arranged at a top of the reaction shaft 4 of the suspension smelting furnace 5; 5a, 5b.

In the smelting step of the method, sulfidic copper bearing material 1, oxygen-bearing reaction gas 2 and slag-forming material 3 react in the reaction shaft 4 of the suspension smelting furnace 5; 5a, 5b into blister copper 7 and slag 8, and blister copper 7 and slag 8 is collected in a settler 11 of the suspension smelting furnace 5 to form a blister layer 9 containing blister copper 7 and a slag layer 10 containing slag 8 on top of the blister layer 9 in the settler 11 of the suspension smelting furnace 5; 5a, 5b.

The method comprises additionally a fire refining step including feeding blister copper 7 obtained in the smelting step into an anode furnace 12 and fire-refining blister copper 7 in the anode furnace 12 producing molten anode copper 13 in the anode furnace 12.

The method comprises additionally an anode casting step including feeding molten anode copper 13 obtained in the fire refining step into anode casting molds 14 to produce cast anodes 15.

The method comprises additionally a quality checking step 16 for dividing cast anodes 15 obtained in the anode casting step into accepted cast anodes 17 and rejected cast anodes 18.

The method comprises additionally an electrolytic refining step including subjecting accepted cast anodes 17 to electrolytic refining in an electrolytic cell 19 to produce cathode copper 20 and as a by-product, spent cast anodes 21.

The method comprises additionally a recycling step for recycling anode copper of rejected cast anodes 18 and anode copper of spent cast anodes 21.

The recycling step includes feeding rejected cast anodes 18 and spent cast anodes 21 into a mechanical breaker 24 such as a shredder for mechanically breaking the rejected cast anodes 18 and spent cast anodes 21 to produce anode copper grain 25, and feeding anode copper grain 25 into the reaction shaft 4 of the suspension smelting furnace 5; 5a, 5b by means of copper grain feeding means 27.

The method may include feeding anode copper grain 25 into the reaction shaft 4 of the suspension smelting furnace 5; 5a, 5b at a distance from the burner 6.

The method may include feeding anode copper grain 25 into the reaction shaft 4 of the suspension smelting furnace 5; 5a, 5b through the burner 6.

The method may include feeding anode copper grain 25 into the reaction shaft 4 of the suspension smelting furnace 5; 5a, 5b from the top of the reaction shaft 4 of the suspension smelting furnace 5; 5a, 5b.

The method may include feeding anode copper grain 25 into the reaction shaft 4 of the suspension smelting furnace 5; 5a, 5b at a feeding that is situated between a connection point between the settler 11 and the reaction shaft 4 and the top of the reaction shaft 4, i.e. at a feeding that is situated at a vertical level between a connection point between the settler 11 and the reaction shaft 4 and the top of the reaction shaft 4.

The method may include feeding additionally inert gas such as nitrogen 26 into the reaction shaft 4 of the suspension smelting furnace 5; 5a, 5b to prevent hot gases from the suspension smelting furnace 5; 5a, 5b from entering the copper grain feeding means 27.

The method may include a drying step for drying anode copper grain 25 in a drying means 28 prior feeding anode copper grain 25 into the reaction shaft 4 of the suspension smelting furnace 5, as shown in the embodiment illustrated in FIG. 6.

The method may include a pre-heating step for pre-heating anode copper grain 25 in a heating means (not shown in the figures) prior feeding anode copper grain 25 into the reaction shaft 4 of the suspension smelting furnace 5.

The method may include using a screw feeder for feeding anode copper grain 25 into the suspension smelting furnace 5

In the fourth and the fifth embodiment illustrated in FIGS. 5 and 6, the method comprises feeding slag 8 obtained in the first smelting step into a slag cleaning electric furnace 29. The fourth and the fifth embodiment of the method comprises a slag treating step for treating slag 8 in the slag cleaning electric furnace 29 with reduction agent 30 fed in the slag cleaning electric furnace 29 to produce an electric furnace slag layer 31 containing electric furnace slag 32 and an electric furnace blister copper layer 33 containing electric furnace blister copper 34. The fourth and the fifth embodiments of the method comprise feeding electric furnace blister copper 34 obtained in the slag treating step into an anode furnace 12. The fourth and the fifth embodiment of the method comprise feeding electric furnace slag 32 obtained in the slag threating step to a final slag cleaning means 35. The fourth and the fifth embodiment of the method comprise a final slag cleaning step for subjecting electric furnace slag 32 to final slag cleaning treatment to produce waste slag 36 and slag concentrate or other copper containing material 37 of electric furnace slag 32. The fourth and the fifth embodiment of the method comprises feeding slag concentrate or other copper containing material 37 obtained in the flotation step into the reaction shaft 4 of the suspension smelting furnace 5.

The second embodiment illustrated in FIG. 3 and the third embodiment illustrated in FIG. 4 are so-called double flash methods, whereas the first embodiment illustrated in FIG. 2, the fourth embodiment illustrated in FIG. 5, and the fifth embodiment illustrated in FIG. 6 are direct-to-blister methods. It is obvious for one skilled in the art that the embodiments illustrated in FIG. 2, 5 or 6 could employ a first suspension smelting furnace 5a and a second suspension smelting furnace 5b as illustrated in FIGS. 3 and 4 and that anode copper grain 25 could be fed into at least one of the first suspension smelting furnace 5a and the second suspension smelting furnace 5b as illustrated in FIGS. 3 and 4.

The first embodiment, the fourth embodiment, and the fifth embodiment illustrated in FIGS. 2, 5 and 6 comprises so-called direct-to-blister smelting in the suspension smelting furnace 5. In the first embodiment, in the fourth embodiment, and in the fifth embodiment illustrated in FIGS. 2, 5 and 6, the smelting step includes feeding sulfidic copper bearing material in the form of copper sulphide concentrate 1a, oxygen-bearing reaction gas 2 and slag-forming material 3 into a reaction shaft 4 of a suspension smelting furnace 5 by means of a burner 6 that is arranged at a top of the reaction shaft 4 of the suspension smelting furnace 5. Copper sulphide concentrate 1a, oxygen-bearing reaction gas 2 and slag-forming material 3 react in the reaction shaft 4 of the suspension smelting furnace 5 into blister copper and slag 8. Matte 1b and slag 8 is collected in a settler 11 of the suspension smelting furnace 5 to form a matte layer 38 containing matte 1b and a slag layer 10 containing slag 8 on top of the matte layer 38 in the settler 11 of the suspension smelting furnace 5a

The second embodiment and the third embodiment illustrated in FIGS. 3 and 3 comprises so-called double flash smelting. In the second and in the third embodiment illustrated in FIGS. 3 and 4, the smelting step includes a first smelting step comprising feeding copper sulphide concentrate 1a, oxygen-bearing reaction gas 2 and slag-forming material 3 into a reaction shaft 4 of a first suspension smelting furnace 5a by means of a burner 6 that is arranged at a top of the reaction shaft 4 of the first suspension smelting furnace 5a. Copper sulphide concentrate 1a, oxygen-bearing reaction gas 2 and slag-forming material 3 react in the reaction shaft 4 of the first suspension smelting furnace 5 into matte 1b and slag 8. Matte 1b and slag 8 is collected in a settler 11 of the first suspension smelting furnace 5 to form a matte layer 38 containing matte 1b and a slag layer 10 containing slag 8 on top of the matte layer 38 in the settler 11 of the first suspension smelting furnace 5a.

In the second and the third embodiment illustrated in FIGS. 3 and 4, the smelting step includes additionally a second smelting step comprising feeding matte 1b obtained in the first smelting step, oxygen-bearing reaction gas 2 and slag-forming material 3 into a reaction shaft 4 of a second suspension smelting furnace 5b by means of a burner 6 that is arranged at a top of the reaction shaft 4 of the second suspension smelting furnace 5b. Matte 1b, oxygen-bearing reaction gas 2 and slag-forming material 3 react in the reaction shaft 3 of the second suspension smelting furnace 5b into blister copper 7 and slag 8. Blister copper 7 and slag 8 is collected in a settler 11 of the second suspension smelting furnace 5 to form a layer containing blister copper 7 and a slag layer 10 containing slag 8 on top of the layer in the settler 11 of the second suspension smelting furnace 5.

In the second embodiment illustrated in FIG. 3, anode copper grain 25 is in the recycling step fed into the reaction shaft 4 of the second suspension smelting furnace 5b.

In the third embodiment illustrated in FIG. 4, anode copper grain 25 is in the recycling step fed into the reaction shaft 4 of the first suspension smelting furnace 5a. In this method the anode copper grain 25 will have an effect on the requirement of oxygen-bearing reaction gas 2 which has to be taken into account in controlling the process.

It is apparent to a person skilled in the art that as technology advances, the basic idea of the invention can be implemented in various ways. The invention and its embodiments are therefore not restricted to the above examples, but they may vary within the scope of the claims.

Claims

1. A method for producing cathode copper, wherein the method comprises

a smelting step including feeding sulfidic copper bearing material such as sulfidic copper concentrate or finely ground copper matte and additionally oxygen-bearing reaction gas and slag-forming material into a reaction shaft of a suspension smelting furnace by means of a burner that is arranged at a top of the reaction shaft of the suspension smelting furnace, whereby sulfidic copper bearing material, oxygen-bearing reaction gas and slag-forming material react in the reaction shaft of the suspension smelting furnace into blister copper and slag, and collecting blister copper and slag in a settler of the suspension smelting furnace to form a blister layer containing blister copper and a slag layer containing slag on top of the blister layer in the settler of a suspension smelting furnace,

a fire refining step including feeding blister copper obtained in the smelting step into an anode furnace and fire-refining blister copper in the anode furnace producing molten anode copper in the anode furnace,

an anode casting step including feeding molten anode copper obtained in the fire refining step into anode casting molds to produce cast anodes,

a quality checking step for dividing cast anodes obtained in the anode casting step into accepted cast anodes and rejected cast anodes,

an electrolytic refining step including subjecting accepted cast anodes to electrolytic refining in an electrolytic cell to produce cathode copper and as a by-product, spent cast anodes, and

a recycling step for recycling anode copper of rejected cast anodes and anode copper of spent cast anodes,

wherein the recycling step including feeding rejected cast anodes and spent anodes into a mechanical breaker for mechanically breaking rejected cast anodes and spent cast anodes to produce anode copper grain and feeding anode copper grain into the reaction shaft of the suspension smelting furnace by means of copper grain feeding means.

2. The method according to claim 1, further comprising feeding anode copper grain into the reaction shaft of the suspension smelting furnace at a distance from the burner.

3. The method according to claim 1, further comprising feeding anode copper grain into the reaction shaft from the top of the reaction shaft of the suspension smelting furnace.

4. The method according to claim 1, further comprising feeding anode copper grain into the reaction shaft of the suspension smelting furnace at a feeding that is situated between a connection point between the settler and the reaction shaft and the top of the reaction shaft

5. The method according to claim 1, further comprising feeding anode copper grain into the reaction shaft of the suspension smelting furnace with the burner.

6. The method according to claim 1, further comprising feeding additionally inert gas such as nitrogen into the reaction shaft of the suspension smelting furnace to prevent hot gases from the suspension smelting furnace from entering the copper grain feeding means.

7. The method according to claim 1, further comprising a drying step for drying anode copper grain in a drying means prior feeding anode copper grain into the reaction shaft of the suspension smelting furnace.

8. The method according to claim 1, further comprising using a screw feeder for feeding anode copper grain into the suspension smelting furnace.

9. The method according to claim 1, further comprising feeding slag obtained in the smelting step into a slag cleaning electric furnace,

by a slag treating step for treating slag in the slag cleaning electric furnace with reduction agent to in the slag cleaning electric furnace produce an electric furnace slag layer containing electric furnace slag and an electric furnace blister copper layer containing electric furnace blister copper,

by feeding electric furnace blister copper obtained in the slag threating step into an anode furnace,

by feeding electric furnace slag obtained in the slag threating step to a floatation means,

by a floatation step for subjecting electric furnace slag to flotation treatment to produce waste slag and slag concentrate of electric furnace slag, and

by feeding slag concentrate obtained in the flotation step into the reaction shaft of the suspension smelting furnace.

10. The method according to claim 1, wherein the smelting step includes a first smelting step comprising feeding copper sulphide concentrate, oxygen-bearing reaction gas and slag-forming material into a reaction shaft of a first suspension smelting furnace by means of a burner that is arranged at a top of the reaction shaft of the first suspension smelting furnace, whereby copper sulphide concentrate, oxygen-bearing reaction gas and slag-forming material react in the reaction shaft of the first suspension smelting furnace into matte and slag, and collecting matte and slag in a settler of the first suspension smelting furnace to form a matte layer containing matte and a slag layer containing slag on top of the layer in the settler of the first suspension smelting furnace, and

by the smelting step includes a second smelting step comprising feeding matte obtained in the first smelting step, oxygen-bearing reaction gas and slag-forming material into a reaction shaft of a second suspension smelting furnace by means of a burner that is arranged at a top of the reaction shaft of the second suspension smelting furnace, whereby matte, oxygen-bearing reaction gas and slag-forming material react in the reaction shaft of the second suspension smelting furnace into blister copper and slag, and collecting blister copper and slag in a settler of the second suspension smelting furnace to form a layer containing blister copper and a slag layer containing slag on top of the layer in the settler of the second suspension smelting furnace.

11. The method according to claim 10, further comprising feeding anode copper grain in the recycling step into the reaction shaft of the first suspension smelting furnace.

12. The method according to claim 10, further comprising feeding anode copper grain in the recycling step into the reaction shaft of the second suspension smelting furnace.