Field of the invention

The invention relates to method for refining sulfidic copper concentrate as defined in the preamble of independent claim 1.

Blister copper means in this context a molten impure copper product consisting mainly of metallic copper (>96%) intended for further refining in anode furnaces.

Matte copper means in this context an impure copper product consisting mainly of copper and iron sulfides.

Figure 1 shows block diagram of an embodiment of a direct to blister process for refining copper concentrate into anode copper.

In the direct to blister process sulfidic copper concentrate 1, oxygen-bearing reaction gas 2, and slag forming material 3, is fed into a reaction shaft 4 of a suspension smelting furnace 5 by means of a burner 6 that is arranged on top of the reaction shaft 4 of the suspension smelting furnace 5 so that sulfidic copper concentrate 1 and 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 8 and slag 7. Slag 7 and blister copper 8 are collected in a settler 9 of the suspension smelting furnace 5 to in the settler 9 of the suspension smelting furnace 5 form a blister layer 10 containing blister copper 8 and a slag layer 11 containing slag 7 on top of the blister layer 10.

Slag 7 and blister copper 8 are separately discharged from the settler 9 of the suspension smelting furnace 5, so that slag 7 is fed into an electric furnace 12 and so that blister copper 8, that can have a copper content of 98 wt-% is fed into anode furnaces 13. Process gases 16 produced in the reactions in the suspension smelting furnace 5 are discharged from the suspension smelting furnace 5 via an uptake 14 of the suspension smelting furnace 5 to a process gas treatment arrangement 15 that normally comprises a waste heat boiler (not shown in the figures) and an electric filter (not shown in the figures).

The slag 7 fed from the settler 9 of the suspension smelting furnace 5 into the electric furnace 12 is in the electric furnace 12 reduced by feeding additionally carbon containing reducing agent 17 such as coke into the electric furnace so that in the electric furnace 12 is formed an electric furnace blister layer 18 containing electric furnace blister copper 19 and an electric furnace slag layer 20 containing electric furnace slag 21 on top of the electric furnace blister layer 18.

Electric furnace slag 21 and electric furnace blister copper 19 are separately discharged from the electric furnace 12 so that electric furnace blister copper 19, that can have a copper content of 97 wt-%, is fed into the anode furnaces 13 where anode copper 22 is produced and so that electric furnace slag 21, that can have a copper content of 4 wt-%, is subjected to final slag cleaning process 23. From the final slag cleaning process 23, that can performed for example by flotation in a flotation arrangement (not shown in the figures) or in an additional electric furnace (not shown in the figures) can slag concentrate or other copper containing product 25 be fed into the reaction shaft 4 of the suspension smelting furnace 5 and reject 24 such as tailings be discarded.

A problem with the direct-to-blister process when treating concentrates with low copper grade is that it produces a lot of thermal energy, which means that the process gas treatment arrangement for treating process gases produced in the process in the suspension smelting furnace has to have a large capacity.

Another problem is that the blister copper that is fed into the anode furnace has normally a different composition such as a different copper content on weight percentage basis than the electric furnace blister copper that is fed from the electric furnace into the anode furnace. Content of many impurities (such as arsenic) in the electric furnace blister copper can be high, causing challenges in maintaining high quality of the anode copper product.

Recovery of copper from the electric furnace slag by using flotation is also challenging because the copper contained in slag is mostly not in sulfidic form.

Objective of the invention

The object of the invention is to provide a method for refining sulfidic copper concentrate that solves the above mentioned problems.

Short description of the invention

The method for refining sulfidic 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 sulfidic copper concentrate as reducing agent in the electric furnace to reduce the slag that is fed from the suspension smelting furnace into the electric furnace by feeding a part of the sulfidic copper concentrate that is to be refined into the electric furnace instead of into the suspension smelting furnace. The sulfidic concentrate reacts with the oxygen contained in the Direct to Blister Furnace slag, resulting in immiscible copper matte and slag products. As oxygen from the slag is consumed in the reaction, copper contained in the slag is reduced. The copper matte formed in the process is solidified, treated and fed to the Direct to Blister Furnace as a feed material. This reduces the amount of process gases produced in the suspension smelting furnace, because a smaller amount of sulfidic copper concentrate is treated in the suspension smelting furnace, and because smelting the solid matte product requires high oxygen enrichment of the process gas.

Because blister copper is fed into the anode furnaces solely from the suspension smelting furnace, the composition of the blister copper that is treated in the anode furnace has a uniform composition and quality. Content of certain impurities, such as arsenic, in blister copper is lower because (i) in electric furnace, where impurities would enter the blister copper due to reducing conditions, they do so to lower extent because their chemical activity coefficient is higher in matte than in blister copper, (ii) all the blister fed to the anode furnaces is discharged from the direct to blister furnace, where the blister copper is in contact with a large amount of highly oxidized slag that dissolves the impurities.

If flotation is utilized in the final slag cleaning process for recovering copper from electric furnace slag, copper recovery is better than in Direct to Blister process because the copper contained in slag is mostly in sulfidic form, which means that copper containing particles are more easily flotated. List of figures

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

Figure 1 shows a block diagram of a direct to blister process,

Figure 2 shows a block diagram of a first embodiment of the method, and

Figure 3 shows a block diagram of a second embodiment of the method.

Detailed description of the invention

Figure 2 shows a block diagram of a first embodiment of the method for refining sulfidic copper concentrate 1 and figure 3 shows a block diagram of a second embodiment of the method for refining sulfidic copper concentrate 1.

The method comprises feeding sulfidic copper concentrate 1 and 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 on top of the reaction shaft 4 of the suspension smelting furnace 5, whereby sulfidic copper concentrate 1 and 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 8 and slag 7.

The method comprises collecting slag 7 and blister copper 8 in a settler 9 of the suspension smelting furnace 5 to in the settler 9 of the suspension smelting furnace 5 form a blister layer 10 containing blister copper 8 and a slag layer 11 containing slag 7 on top of the blister layer 10.

The method comprises discharging slag 7 and blister copper 8 separately from the settler 9 of the suspension smelting furnace 5, so that slag 7 is fed into an electric furnace 12.

The method comprises feeding a part of the sulfidic copper concentrate 1 into the electric furnace 12.

The method comprises reducing the slag 7 in the electric furnace 12 at least partly with the sulfidic copper concentrate 1 that is fed into the electric furnace 12 to in the electric furnace 12 form a matte layer 26 containing copper matte 27 and an electric furnace slag layer 20 containing electric furnace slag 21 on top of the matte layer 26. The method comprises discharging electric furnace slag 21 and matte copper separately from the electric furnace 12.

The method comprises granulating and treating 28 the copper matte 27 that is discharged from the electric furnace 12 to obtain copper matte feed material 29.

The method comprises feeding at least a part of said copper matte feed material 29 into the reaction shaft 4 of the suspension smelting furnace 5 by means of the burner 6.

The method may include, as shown in figures 2 and 3, feeding blister copper 8 from the settler 9 of the suspension smelting furnace 5 into an anode furnace 13 or into anode furnaces 13, and fire refining blister in the anode furnace(s) 13.

The method may include, as shown in figure 2, subjecting the subjecting the electric furnace slag 21 to a final slag cleaning process 23 that can performed for example by flotation in a flotation arrangement (not shown in the figures) or in an additional electric furnace (not shown in the figures). From the final slag cleaning process 23 can slag concentrate or other copper containing product 25 be fed into the reaction shaft 4 of the suspension smelting furnace 5 by means of the burner 6 of the suspension smelting furnace 5 and reject 24 such as tailings be discarded.

The method may include, as shown in figure 3, feeding additionally carbon containing reducing agent 17 such as coke into the electric furnace 12.

The method may include, as shown in figures 2 and 3, feeding process gases 16 from an uptake 14 of the suspension smelting furnace 5 to a process gas treatment arrangement 15.

The method may include feeding process gases from the electric furnace 12 to a process gas treatment arrangement 15.

The method may include feeding between 5 and 50 , preferably between 10 and 40 , more preferably between 25 and 35 , such as about 33 , of the sulfidic copper concentrate 1 into the electric furnace 12.

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.