Method for manufacturing copper

Abstract

To provide a method for manufacturing copper capable of efficiently utilizing fine slag including copper and silica such as water-granulated slag without accelerating a wear of a facility.SOLUTION: Fine slag represented by water-granulated slag with an average grain diameter 0.8 to 1.6 mm including copper and silica is treated by preferably a wet-type mill pulverization at an ore polishing step together with converter slag crushed at a crushing step, and is charged into a smelting furnace.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing copper by dry copper smelting, and particularly to a method for producing copper in which fine slag by-produced in dry copper smelting is repeatedly used as a raw material for dry copper smelting.

Background Art

[0002] In dry copper smelting, pure copper is produced by concentrating copper step by step in a pretreatment step, a smelting step, a copper making step, and a refining step for an ore raw material composed of a sulfide ore. Specifically, first, in the pretreatment step, a copper concentrate having a copper grade of about 30% is produced by subjecting a sulfide ore mainly composed of chalcopyrite to pretreatment such as crushing, classification, and flotation. Next, in the smelting step, the copper concentrate produced in the above pretreatment step is charged into a smelting furnace such as a reverberatory furnace together with silica (silica) called a flux and a cooling material, and further, most of the iron sulfide contained in the copper concentrate is oxidized by blowing air or oxygen-enriched air to generate iron oxide, which is combined with silica or gangue components to form slag, and at the same time, a matte having a copper grade of about 60% is generated from a part of the remaining iron sulfide and copper sulfide. These slag and matte are separated into upper and lower layers respectively by a specific gravity difference in the settler part of the reverberatory furnace.

[0003] Next, in the copper making step, the matte withdrawn from the above reverberatory furnace is charged into a converter, and air or oxygen-enriched air is blown from the tuyere thereof to combine iron oxide generated by oxidation of iron sulfide as described above with silica to generate converter slag. After removing this converter slag by tilting the converter, air or oxygen-enriched air is blown again to oxidize white copper matte composed of copper sulfide remaining in the converter to generate blister copper. Finally, in the refining step, this blister copper is transferred to a refining furnace and reduced with a reducing gas such as propane to generate refined blister copper having a copper grade of 99.8%. By charging an anode plate obtained by casting this refined blister copper together with a separately prepared cathode plate into an electrolytic cell and performing electrolytic refining, electrolytic copper (pure copper) having a copper grade of 99.99% or more is produced.

[0004] The slags generated in the above-mentioned reverberatory furnace and converter are both melts mainly composed of iron oxide and silica, etc., which are also called fayalite (2FeO·SiO2). However, since their copper grades are different, they are processed separately. That is, the converter slag generated in the copper-making process contains about 5 to 10% by mass of copper, so it is repeatedly fed into the reverberatory furnace as a raw material together with copper concentrate. However, the converter slag may contain a large amount of Fe3O4. In this case, if it is repeatedly fed into the reverberatory furnace as it is, there is a risk of increasing the viscosity of the slag in the settler part of the reverberatory furnace and preventing the separation of these matte and slag layers. Therefore, the converter slag is subjected to ore dressing treatment in a karami ore dressing process before being repeatedly fed into the reverberatory furnace to separate and remove Fe3O4.

[0005] On the other hand, the reverberatory furnace slag generated in the smelting process contains matte that floats (also called suspended) in the form of particles that could not be completely separated in the above-mentioned settler part. As a result, copper flows out of the system. Therefore, the reverberatory furnace slag withdrawn from the reverberatory furnace is charged into an electric furnace equipped with a plurality of electrodes called a refining furnace. Here, while heating with the Joule heat generated by the electrodes, it is left standing again to separate and recover the matte from the reverberatory furnace slag. Since the recovered matte can be directly processed in the converter, the amount of copper distributed to the reverberatory furnace slag and flowing out of the system can be reduced, and the yield can be increased. After the suspended matte is recovered in this way, the refining furnace slag is withdrawn from the refining furnace and introduced into running water composed of a large amount of water or seawater. As a result, the refining furnace slag is quenched and crushed to form fine-grained fine slag called granulated slag.

[0006] As described in Non-Patent Document 1, the above granulated slag is generally used as a sandblasting material for rust removal of ships and other structures, and as a civil engineering and construction material such as a cement material or fine aggregate for concrete. Standards are defined for each of these applications. For example, when the particle size (particle shape), composition, density, etc. of the granulated slag conform to the standards of "JIS A5011-3 (2016) Slag Aggregate for Concrete", it can be used as a slag aggregate for concrete. Therefore, technologies for adjusting the properties of granulated slag have been proposed to meet these standards. For example, Patent Document 1 discloses a technology for adjusting the blending ratios of copper concentrate, miscellaneous raw materials, and flux used in the raw materials of the copper smelting process in which the granulated slag is produced in order to adjust the particle size of the granulated slag to a size suitable for a sandblasting material.

Prior Art Documents

Non-Patent Documents

[0007]

Non-Patent Document 1

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] The Karami beneficiation process for beneficiating the above-mentioned converter slag generally consists of a crushing process in which the converter slag is slowly cooled and then crushed by a crusher such as a jaw crusher or a cone crusher, a grinding process in which the converter slag crushed in the crushing process is ground by milling or the like, a flotation process that is performed as necessary when the converter slag contains Fe3O4, and a dehydration process in which the slurry-like so-called slag concentrate treated in these grinding processes or flotation processes is concentrated and dehydrated using a thickener and a ceramic filter or the like. By charging the high-copper-grade slag concentrate thus produced together with copper concentrate as raw materials into a reverberatory furnace, the yield of copper smelting per unit ore raw material can be increased.

[0010] On the other hand, granulated slag that does not meet any of the above standards for civil engineering materials and sandblasting materials is a glassy, sharp, and powdery granule with a particle size of about several millimeters and a low copper grade of about 1%. Therefore, it has few other uses and is either disposed of as waste or sometimes charged into a reverberatory furnace or a converter as a cooling material. Also, even for granulated slag that meets the above standards, there is not always a demand to purchase the entire amount, and it has sometimes been left piled up in large quantities in the in-plant stockyard for a long time. These days, due to the increasing awareness of environmental protection, the effective utilization of resources is advocated, and it is required to improve the situation where granulated slag is discarded or left as described above.

[0011] As a countermeasure, it is conceivable to beneficiate granulated slag in the same way as converter slag and repeat the process in a reverberatory furnace. Therefore, when granulated slag was mixed with converter slag and beneficiated in the Karami beneficiation process, a problem occurred in that the part of the crusher in contact with the slag was severely worn. The reason is considered to be that, as described above, granulated slag contains silica in addition to copper, so it is a hard, brittle, and sharp powdery granule, which promoted the wear of the crusher. The present invention has been made in view of the above circumstances, and an object thereof is to propose a method for producing copper that can effectively utilize fine slag containing copper and silica such as granulated slag without promoting the wear of the crusher.

Means for Solving the Problems

[0012] In order to achieve the above object, the method for producing copper according to the present invention is characterized in that fine slag having an average particle size of 0.8 to 1.6 mm containing copper and silica is processed in a grinding step together with converter slag that has been crushed in a crushing step and charged into a smelting furnace.

Effect of the Invention

[0013] According to the present invention, fine slag such as granulated slag can be effectively utilized without promoting the wear of the crusher.

Brief Description of the Drawings

[0014]

Figure 1

Mode for Carrying Out the Invention

[0015] Hereinafter, an embodiment of the method for producing copper according to the present invention will be described. The method for producing copper in this embodiment of the present invention includes a smelting step of charging copper concentrate together with flux and coolants into a self-smelting furnace as a smelting furnace and oxidizing it to generate matte and slag, a copper-making step of charging the matte extracted from the self-smelting furnace into a converter and oxidizing it to generate blister copper and converter slag, a refining step of refining the blister copper extracted from the converter to generate pure copper, a granulating step of introducing the slag extracted from the self-smelting furnace into running water to generate granulated slag, and a karami beneficiation step of treating the above converter slag and granulated slag.

[0016] And the above karami beneficiation step includes a crushing step of crushing the converter slag extracted from the converter, a grinding step of subjecting at least a part of the granulated slag to grinding treatment by directly adding it to the crushed converter slag without passing through the above crushing step, a flotation step of subjecting the ground converter slag and granulated slag to flotation, and a dehydration step of concentrating and dehydrating the slag concentrate recovered on the floating ore side in the flotation.

[0017] Thus, in the copper production method according to the embodiment of the present invention, when treating granulated slag together with converter slag in the karami beneficiation process, the granulated slag does not go through a crushing process, so the granulated slag can be effectively utilized together with the converter slag without causing the problem of significant wear of the crusher. Hereinafter, each of the above steps will be specifically described with reference to FIG. 1.

[0018] 1. Smelting Process In the smelting process, copper concentrates stored separately by type in a plurality of blending bins 1A and 1B are cut out onto a conveyor from their bottoms, and further, a flux mainly composed of silica and slag concentrate described later is cut out onto the conveyor. These cut-out copper concentrates, flux, and slag concentrate (hereinafter referred to as copper concentrates, etc.) are charged into a rotary dryer 2 via the conveyor, where they are dried under predetermined heat treatment conditions. The dried copper concentrates, etc. pass through a dry ore bin 3 and are blown into a reaction shaft part of a reverberatory furnace 4 from the top through a concentrate burner together with air or oxygen-enriched air.

[0019] While the copper concentrates, etc. blown in from the top are falling through the reaction shaft part, the iron and sulfur components contained in the copper concentrates are oxidized, and the reaction heat causes the copper concentrates and silica to melt, while iron oxide and sulfur dioxide are generated. The former iron oxide combines with gangue components contained in silica and copper concentrates to form slag (karami), and layer-separates from matte (kawa) mainly composed of copper sulfide and iron sulfide in the settler part of the reverberatory furnace 4. On the other hand, the latter sulfur dioxide is discharged as exhaust gas from the uptake part of the reverberatory furnace 4 and transferred to a sulfuric acid plant for use as a raw material for sulfuric acid.

[0020] In the settler section described above, in the slag layer that has been separated into upper and lower layers, particulate matte that could not be completely separated floats (hangs) therein. To reduce copper loss due to this hanging matte, the slag layer is withdrawn as converter slag from the settler section through a trough and directly charged into the reverberatory furnace 5. The converter slag charged into the reverberatory furnace 5 is heated by the Joule heat of a plurality of electrodes inserted from the top and is allowed to stand still again. As a result, the separation of the hanging matte contained in the converter slag is promoted, so that it can be withdrawn from the reverberatory furnace 5 as recovered matte. This recovered matte is processed in the converter 6 together with the converter matte described later. On the other hand, the converter slag after the hanging matte has been separated and removed is withdrawn from the reverberatory furnace 5 through a trough as reverberatory furnace slag and processed in the granulation process described later.

[0021] 2. Copper production process In the copper production process, the lower-layer matte withdrawn as converter matte from the settler section of the above-mentioned converter 4 is transferred to the converter 6 through a ladle composed of a cylindrical container that is suspended so as to be rotatable, and is oxidized here. The converter 6 is a horizontally long furnace that supports a cylindrical container in a horizontal orientation and is rotatable. By blowing air or oxygen-enriched air from a plurality of gas introduction parts called tuyeres provided on its side wall part, the iron content and sulfur content contained in the matte charged into the converter 6 are oxidized. Due to this oxidation, sulfur dioxide is generated and slag in which iron oxide and silica are combined is generated on the upper layer side, similar to the case of the above-mentioned converter 4. The slag thus generated is discharged as converter slag by tilting the converter 6 and is processed in the karami beneficiation process described later. On the other hand, the white copper matte composed of copper sulfide remaining in the converter 6 after the above-mentioned converter slag is discharged is oxidized by blowing air or oxygen-enriched air from a plurality of tuyeres again to produce blister copper.

[0022] 3. Refining process In the refining process, the crude copper produced in the above copper smelting process is discharged by tilting the converter 6, and this is transferred to the refining furnace 7 via a ladle for reduction treatment. The refining furnace 7 is composed of a cylindrical horizontally long furnace similar to the converter 6. The crude copper charged into the refining furnace 7 has the oxygen in the crude copper reduced and removed by blowing in a reducing gas such as propane, thereby becoming refined crude copper. The obtained refined crude copper is withdrawn from the refining furnace 7 and transferred as it is to an anode casting machine (not shown) via a trough. A turntable having a plurality of molds provided at equal intervals in the circumferential direction is generally used for the anode casting machine, and a plurality of anode plates are continuously cast by sequentially pouring the refined crude copper into these molds. By immersing the plurality of anode plates cast in this way one by one alternately side by side in the electrolytic solution in the electrolytic cell together with a plurality of separately prepared cathode plates for electrolytic refining, electrolytic copper with a copper grade of about 99.99% is produced.

[0023] 4. Granulation process In the granulation process, the converter slag withdrawn from the above converter furnace 5 is granulated by introducing it into running water. The method of granulation is not particularly limited, but a method of introducing the converter slag from above into the running water in the granulation trough (also called a flowing trough) 8 by jetting a large amount of water or seawater at high pressure from a nozzle provided on the upstream side of the granulation trough is preferable. Thereby, it is possible to efficiently generate finely pulverized fine slag by rapidly cooling the high-temperature molten converter slag without causing troubles such as steam explosion or clogging. The converter slag granulated in this way is discharged as granulated slag from the end of the granulation trough 8 together with water or seawater and flows into the slag pit 9 for sedimentation. The sedimented granulated slag is lifted from the slag pit 9 by a bucket conveyor or a drag conveyor, drained, and then temporarily stored. This granulated slag is mainly sold as a blasting material, but in the copper production method of the embodiment of the present invention, at least a part of this granulated slag is processed in a later-described karami beneficiation process.

[0024] The average particle size of the granulated slag produced in the above granulation process is 0.8 to 1.6 mm. The average particle size of the granulated slag in this case is determined using a Rosin-Rammler diagram after sieving using sieves with openings of 2.35 mm, 1.18 mm, and 0.60 mm. It should be noted that for the measurement of this average particle size, it is preferable to randomly collect 10 samples and evaluate them based on their average value. In the method for producing copper according to the embodiment of the present invention, granulated slag generated by pulverizing the converter slag discharged from the converter furnace 5 by water cooling is used for the fine slag processed in the following Karami beneficiation process. However, it is not limited thereto, and any fine slag having an average particle size of 0.8 to 1.6 mm containing copper and silica can be effectively utilized.

[0025] 5. Karami Beneficiation Process The Karami beneficiation process is composed of four processes: a crushing process, a grinding process, a flotation process, and a dehydration process. At least a part of the converter slag and the granulated slag are used to produce Karami concentrate through these processes. Hereinafter, each of these four processes will be described.

[0026] (1) Crushing Process The crushing process is a process of roughly crushing the converter slag, preferably to a particle size of about 11 mm or less. There is no particular limitation on the crusher used for this crushing process. However, a jaw crusher that sandwiches and compressively crushes the object to be crushed falling from above between both tooth plate parts by opposing a fixed tooth plate part and a swinging tooth plate part at a predetermined biting angle, or a cone crusher that sandwiches and compressively crushes the object to be crushed falling from above between them by eccentrically swinging a conical mantle within an inverted conical cone cave, is preferably used. In particular, it is more preferable to use both of them for stepwise crushing.

[0027] Specifically, the converter slag temporarily stored in the raw ore hopper 11 is cut out from the bottom at a predetermined cut-out amount and first fed into the jaw crusher 12 for primary crushing. After this primary crushing, for example, it is classified by a first vibrating screen 13 with an aperture of 150 mm. The oversize of this primary classification is repeatedly crushed again by the front-stage jaw crusher 12, and the undersize is fed into the cone crusher 14 in the rear stage for secondary crushing to further crush it finer. After this secondary crushing, for example, it is classified by a second vibrating screen 15 with an aperture of 11 mm. The oversize of this secondary classification is repeatedly subjected to secondary crushing again by the front-stage cone crusher 14, and the undersize is temporarily stored in the intermediate hoppers 16A and 16B and then processed in the next-stage grinding process.

[0028] (2) Grinding process The grinding process is a process of subjecting at least a part of the granulated slag generated in the granulation process described above to grinding treatment in addition to the converter slag crushed to a predetermined particle size in the above crushing process. There is no particular limitation on the method of this grinding treatment, and examples include shear agitation that stirs with an intensity such that a shearing force acts on the object to be ground, friction grinding (attrition) that polishes the surface with an intensity such that the object to be ground does not break, ball mill grinding, rod mill grinding, and the like.

[0029] As the grinding device for performing the above grinding treatment, a ball mill that rotates a cylindrical body containing steel balls as a grinding medium and introduces the object to be ground together with water into the inside thereof to perform grinding treatment by the impact of the falling steel balls, a SAG (Semi-Autogenous Grinding) mill that rotates a cylindrical body having an outer diameter larger than that of the ball mill with steel balls stored therein in the same manner as above and introduces the object to be ground together with water to perform grinding treatment by the impact of the falling steel balls, a rod mill that rotates a cylindrical body having a plurality of steel rods accommodated therein parallel to the central axis direction and introduces the object to be ground together with water into the inside thereof to perform grinding treatment by the impact when the steel rods fall, a bead mill that forcibly stirs a large number of spherical grinding media accommodated in a cylindrical container with a stirring device to perform grinding treatment on the object to be ground introduced together with water into the container, and the like can be mentioned. Among these, a ball mill and a SAG mill are preferred.

[0030] Specifically, the crushed converter slag is discharged onto the conveyor 18 from the bottoms of the intermediate hoppers 16A and 16B, and the granulated slag is also discharged onto the conveyor 18 from the bottom of the granulated slag hopper 17. Both slags are introduced into, for example, a SAG mill as the primary mill 21. In this way, the granulated slag discharged from the bottom of the granulated slag hopper 17 is finally charged into the smelting furnace 4 as a raw material together with the copper concentrate and the converter slag. Therefore, the amount of the granulated slag discharged from the granulated slag hopper 17 is adjusted so that the granulated slag preferably occupies 5 to 15% by mass (dry basis), more preferably about 10% by mass (dry basis) of the raw material charged into the smelting furnace 4. A predetermined amount of water is also introduced into the primary mill 21 for wet milling treatment.

[0031] The slag primarily ground as described above is temporarily received in the buffer tank 21a, and then, in the mixing tank 21b on the downstream side, it is mixed with the slag after secondary grinding described later, and then pressurized by a pump and introduced into the hydrocyclone 22, where it is separated into two types of slag according to the particle size by using centrifugal force. Then, the slag with the larger particle size is introduced into, for example, a ball mill as the secondary mill 23 in the subsequent stage and further ground finer by secondary grinding. On the other hand, the slag with the smaller particle size separated by the hydrocyclone 22 is transferred to the flotation process in the next step.

[0032] The method for producing copper according to the embodiment of the present invention is to cut out the converter slag that has been crushed in the crushing process and the granulated slag that has not passed through the crushing process on the conveyor 18 at a predetermined mixing ratio, and then appropriately mix these two slags on the conveyor 18 and introduce them as a mixed slag into the primary mill 21. Thereby, the granulated slag, which is glassy, hard, brittle, and has a relatively small particle shape, can be ground homogeneously together with the converter slag. In addition, since the granulated slag does not pass through crushers such as jaw crushers and cone crushers, it is possible to prevent these crushers from being worn by the granulated slag. Moreover, since the particle size of the granulated slag hardly changes even if it is crushed by these jaw crushers and cone crushers, it is possible to prevent an increase in operating costs due to unnecessarily passing through the crushing process.

[0033] (3) Flotation process The converter slag may contain Fe3O4 as described above. If the converter slag contains Fe3O4 to such an extent that problems occur, for example, as a result of analysis for each lot or periodically, the mixed slag composed of the converter slag and the granulated slag that has been ground in the above grinding process is introduced into the flotation machine 24 as needed for flotation treatment. Thereby, since Fe3O4 can be separated to the sediment side, the mixed slag from which Fe3O4 has been removed can be recovered on the floating ore side. There is no particular limitation on the type of the flotation machine 24, but it is preferably a facility that consists of a cylindrical container and an impeller provided at the central axis portion thereof, and performs flotation by discharging air from the discharge port provided at the blade portion of the impeller. Examples of such facilities include Denver-type or Agitair-type flotation machines.

[0034] (4) Dewatering process The mixed slag obtained after being processed in the crushing process and the grinding process as described above and, if necessary, further subjected to flotation treatment in the flotation process has a slurry form. Therefore, it is preferably introduced into the thickener 25, concentrated by removing moisture through gravity sedimentation separation, and then further introduced into a dehydrator 26 such as a ceramic filter for dehydration. Note that after dehydration by the dehydrator 26, it may be further dried by a dryer 27 if necessary. The mixed slag dehydrated and, if necessary, dried in this way is once stored in the karami concentrate bin 28 as karami concentrate, and then cut out from the bottom so as to have a predetermined blending ratio with respect to the copper concentrate, and can be charged into the smelting furnace 4 together with the copper concentrate through the concentrate burner.

Example

[0035] [Example] Pure copper was produced from the raw copper concentrate along the process flow of the copper production method by dry copper smelting as shown in Fig. 1. At that time, in the karami ore dressing process, the granulated slag was mixed with the crushed converter slag and wet grinding treatment was carried out using a SAG mill and a ball mill so that 10% by mass (dry basis) of the raw material charged into the smelting furnace 4 was occupied by the granulated slag. The mixed slag of the converter slag and the granulated slag after the grinding treatment was subjected to flotation treatment by the flotation machine 24 to separate and remove Fe3O4 to the sediment side, and further repeated to the smelting furnace 4 through gravity sedimentation by the thickener 25, dehydration by the ceramic filter 26, and drying treatment by the dryer 27. As a result, in the jaw crusher 12 and the cone crusher 14 used in the karami ore dressing process and the crushing process, the liner provided at the portion in contact with the object to be crushed could be used for 250 days. In addition, the yield in dry copper smelting could be increased compared with the case where the total amount of the granulated slag was sold externally.

[0036] [Comparative Example] In the chromite beneficiation process, the operation was carried out in the same manner as in the above-described example, except that in the crushing process, the same amount of granulated slag as in the example was mixed with the converter slag before the crushing treatment and then the crushing treatment was performed. As a result, in the crushing equipment used in the chromite beneficiation process, the liner provided at the portion in contact with the object to be crushed was worn out in 100 days, and replacement became inevitable. From the results of the above example and the comparative example, it can be seen that when treating granulated slag together with converter slag in the chromite beneficiation process, wear of the crusher can be suppressed by not passing the granulated slag through the crusher.

Explanation of Signs

[0037] 1A, 1B Blending Bin 2 Rotary Dryer 3 Dry Ore Warehouse 4 Autogenous Furnace 5 Refining Furnace 6 Converter 7 Refining Furnace 8 Granulation Trough 9 Slag Pit 11 Raw Ore Hopper 12 Jaw Crusher 13 First Vibrating Screen 14 Cone Crusher 15 Second Vibrating Screen 16A, 16B Intermediate Hopper 17 Granulated Slag Hopper 18 Conveyor 21 Primary Mill 21a Buffer Tank 21b Mixing Tank 22 Liquid Cyclone 23 Secondary Mill 24 Flotation Machine 25 Thickener 26 Dewatering Machine 27 Dryer 28 Chromite Concentrate Bin

Claims

1. A method for producing copper, characterized in that fine slag having an average particle size of 0.8 to 1.6 mm and containing copper and silica is processed in a grinding step together with converter slag crushed in a crushing step and charged into a smelting furnace.

2. The method for producing copper according to claim 1, characterized in that the fine slag is granulated slag.

3. The method for producing copper according to claim 1, characterized in that the grinding step is wet milling and the wet milling is followed by treatment in a dehydration step.

4. The method for producing copper according to claim 3, characterized by including a flotation step between the grinding step and the dehydration step.

5. The silica is SiO derived from a flux ２ The method for producing copper according to claim 1, characterized in that it is as described above.

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