JP2024078333A - Supply method of copper smelting raw material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for supplying copper smelting raw materials capable of stably operating by suppressing thermal load fluctuation of a self-fluxing furnace due to charging of miscellaneous raw materials.

SOLUTION: A method of supplying copper concentrate, silicate cooling material, and miscellaneous raw materials as copper smelting raw materials to a self-melting furnace 6, of the two bins 1 and 2 provided above a belt conveyor 3 running toward the self-melting furnace 6, from the first bin 1, the copper concentrate is cut out, and from the second bin 2, the silicate-containing cold charge and the miscellaneous raw materials are cut out, and based on the calorific value at the time of combustion in the self-melting furnace 6 of the copper concentrate cut from the first bin 1, a cut out amount from the second bin 2 is controlled.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a method for supplying copper smelting raw materials, including copper concentrate, cold material, and miscellaneous raw materials.

In dry copper smelting, sulfide ore, mainly made of chalcopyrite, is subjected to pretreatment such as flotation to produce copper concentrate with a copper content of about 30%. This copper concentrate is then charged into a flash smelting furnace together with a flux (solvent) mainly made of silica and a cooling material that lowers the temperature of the molten metal in the flash smelting furnace. The resulting oxidation reaction of the sulfur in the copper concentrate produces slag, which is then separated based on its specific gravity to produce matte with a copper content of about 60-65%. This matte is then further concentrated in a converter and refining furnace in the subsequent stages to produce refined crude copper with a copper content of about 99.8%, which is then cast into the form of an anode and electrolytically refined to produce electrolytic copper with a copper content of 99.99%.

The flash smelting furnace generates high-temperature exhaust gas containing a large amount of sulfur dioxide derived from the sulfur content in the copper concentrate. This exhaust gas is introduced into a waste heat boiler to recover heat, and then processed as a raw material for sulfuric acid in a sulfuric acid plant. In this sulfuric acid plant, muddy sediment containing concentrated impurities is generated in equipment that removes dust contained in the exhaust gas discharged from the flash smelting furnace, and in equipment that treats waste acid produced as a by-product in the refining process. In copper smelting plants, muddy sediment and granular material containing concentrated impurities are also generated, for example, from equipment that purifies the electrolyte used in the electrolytic refining.

As mentioned above, the sediments and granular materials generated in copper smelting plants and sulfuric acid plants generally contain valuable metals such as copper, so these sediments are usually collected and charged into the flash furnace as recycle materials together with the copper concentrate. In addition, recycled materials such as gold and silver slag, which is a sludge containing valuable metals recovered by processing so-called urban mines, such as waste electronic circuit boards recovered from discarded mobile phones and personal computers, and copper slag, which is a sludge containing copper generated by copper foil and casting manufacturers, are also processed in the flash furnace as secondary materials. These recycle materials and secondary materials are collectively called miscellaneous materials or miscellaneous materials, and not only the composition but also the form (mud, wet cake, granular, or flake shape, etc.), particle size (size), moisture content, reaction heat, and other properties vary greatly compared to copper concentrate, so when these miscellaneous materials are charged into the flash furnace, the operation of the smelting furnace can become unstable.

Therefore, a technology has been proposed to mix copper concentrate and miscellaneous raw materials as uniformly as possible before charging into a flash smelting furnace. For example, Patent Document 1 proposes a technology in which miscellaneous raw materials are quantitatively cut and added onto each brand of copper concentrate being transported by a conveyer belt to a blending facility that blends multiple brands of copper concentrate, so that the properties of the mixture of copper concentrate and miscellaneous raw materials are approximately uniform.

Japanese Patent Application Laid-Open No. 09-087760

As mentioned above, copper concentrate contains sulfur, so its combustion causes an exothermic reaction. On the other hand, most of the repeating materials contained in the miscellaneous raw materials are sulfates or hydroxides, such as CaSO ₄ (H ₂ O) ₂ , Fe(OH) ₃ , and Ni(OH) ₂ , and therefore cause endothermic reactions in the flash smelting furnace. In addition, most secondary raw materials, such as copper slag and gold and silver slag, also endotherm in the flash smelting furnace. Therefore, although it is possible to mix copper concentrate and miscellaneous raw materials to a certain degree uniformly by adopting the technology of Patent Document 1, for example, when the lot of the miscellaneous raw materials added to the copper concentrate is changed or the composition changes significantly, the operation in the flash smelting furnace may become unstable. That is, when the content of the substance that causes an endothermic reaction in the miscellaneous raw materials charged into the flash smelting furnace together with the copper concentrate decreases, the amount of heat generated increases, and conversely, when the content of the substance that causes an endothermic reaction in the miscellaneous raw materials increases, the amount of heat generated decreases.

As described above, the heat load fluctuates greatly with the fluctuation in the content of substances that cause endothermic reactions contained in miscellaneous raw materials, which can cause unstable operation in the flash furnace, resulting in a problem that the copper grade in the granulated slag obtained by crushing the slag extracted from the flash furnace into sand-like material using running water is higher than the desired grade. The present invention was made in consideration of the problems associated with the above-mentioned flash furnace, and aims to provide a method for supplying copper smelting raw materials that can suppress fluctuations in the heat load of the flash furnace caused by the charging of miscellaneous raw materials, enabling stable operation.

In order to achieve the above object, the method for supplying copper smelting raw materials according to the present invention is a method for supplying copper concentrate, silicate-containing cooling material, and miscellaneous raw materials as copper smelting raw materials to a flash smelting furnace, and is characterized in that, of at least two bins provided above a conveying means traveling toward the flash smelting furnace, the copper concentrate is cut out from a first bin and the silicate-containing cooling material and the miscellaneous raw materials are cut out from a second bin, and the amount cut out from the second bin is controlled based on the amount of heat generated when the copper concentrate cut out from the first bin is burned in the flash smelting furnace.

The present invention makes it possible to stabilize the operation of the flash melting furnace, thereby reducing the copper content in the granulated slag to a desired level or lower.

FIG. 1 is a flow diagram of a method for supplying copper smelting raw material according to an embodiment of the present invention. FIG. 2 is a flow diagram showing how copper smelting raw material is cut out from each of the two bins shown in the flow diagram of FIG. 1 while controlling the amount of the raw material to be cut out and spread out on the belt surface of a belt conveyor.

The embodiment of the method for supplying copper smelting raw materials according to the present invention will be described in detail below. The method for supplying copper smelting raw materials according to the embodiment of the present invention is a method in which copper concentrate, silicate-containing coolant, and miscellaneous raw materials as copper smelting raw materials are cut out from at least two bins onto a conveying means such as a belt conveyor, and then supplied to a flash smelting furnace together with a flux mainly consisting of silica sand. To be more specific, in a dry copper smelting plant, as shown in FIG. 1, copper smelting raw materials cut out from multiple bins 1 and 2 are conveyed by a belt conveyor 3 and charged into a rotary dryer 4, where they are dried under predetermined processing conditions, and then conveyed by an air flow conveying device 5 to a cyclone 7 located above the reaction shaft of the flash smelting furnace 6. The copper smelting raw materials separated from the air flow by the cyclone 7 are temporarily stored in a dry ore storage 8, and then blown into the flash smelting furnace 6 together with the flux for processing.

In the embodiment of the present invention, the following supply method is adopted when copper smelting raw materials are fed from the multiple bins 1 and 2 to the belt conveyor 3. That is, of the first bin 1 and the second bin 2 that are arranged in series above the belt conveyor 3 along its running direction, in the first bin 1 located upstream in the conveying direction of the belt conveyor 3, only the copper concentrate fed from the top is fed from the lower outlet and spread on the belt surface of the belt conveyor 3, and in the second bin 2 located downstream of the first bin in the conveying direction, the silicate-containing coolant and miscellaneous raw materials fed from the top are fed from the lower outlet and further spread on the copper concentrate spread on the belt surface of the belt conveyor 3. Note that the bins may be arranged in the reverse order to that in FIG. 1 with respect to the conveying direction of the belt conveyor 3 (i.e., the first bin 1 is arranged downstream and the second bin 2 is arranged upstream).

When copper concentrate is cut from the first bin 1, the amount of the copper concentrate cut is adjusted using a first cut-out device 1a such as a rotary feeder provided at the lower outlet. Similarly, when silicate-containing coolant and miscellaneous raw materials are cut from the second bin 2, the amount of the copper concentrate cut is adjusted using a second cut-out device 2a such as a rotary feeder provided at the lower outlet. Furthermore, the amount of the copper concentrate cut from the second bin 2 is controlled based on the amount of heat generated per unit time during combustion in the flash smelting furnace 6 of the copper concentrate cut from the first bin 1. This makes it possible to suppress the thermal load fluctuation in the flash smelting furnace 6, and as a result, the operation of the flash smelting furnace is stabilized, making it possible to suppress the copper content in the granulated slag to a desired level or lower.

More specifically, as described above, an exothermic reaction occurs during the combustion of copper concentrate in the flash furnace 6, and therefore, in order to suppress the thermal load on the furnace body due to excessive heat generation, a silicate-containing coolant is charged into the flash furnace 6 as an auxiliary raw material while adjusting the amount of the coolant charged so that the flash furnace 6 is at an appropriate temperature. The reason for using a substance containing silicate as the coolant in this way is that silicates, typified by _Fe2 ( _SiO4 ), cause endothermic reactions and can therefore be suitably used as a coolant for the flash furnace 6.

Miscellaneous raw materials are also charged into the flash furnace 6 as auxiliary raw materials. As mentioned above, the miscellaneous raw materials include precipitates generated by adding alkali to waste acid discharged from sulfuric acid plants, copper-removed slime generated during the purification process of electrolyte during electrolytic refining and electrolytic winning, copper slag such as copper oxide that scatters and peels off when casting anodes are quenched in a cooling tank, and precipitates generated by adding alkali to acidic wastewater from various parts of the factory. These are generally mostly generated in the form of small particle size in the liquid in a tank such as a neutralization tank, and therefore have a muddy or wet cake-like form, causing an endothermic reaction when charged into the flash furnace 6. For this reason, if copper concentrate, which causes an exothermic reaction, and miscellaneous raw materials consisting of neutralized sediment are cut out from one bottle and charged into the flash furnace 6, the operation of the flash furnace 6 may become unstable.

In contrast, in the copper smelting raw material supply method according to the embodiment of the present invention, only copper concentrate is excavated from the first bin 1 as described above, which makes it possible to eliminate disturbances such as fluctuations in the content of substances that cause endothermic reactions in the copper concentrate, which was one of the causes of thermal load fluctuations in the past. Furthermore, silicate-containing coolant and miscellaneous raw materials, both of which cause endothermic reactions in the flash smelting furnace, are excavated from the second bin 2, and the amount excavated from the second bin 2 is controlled based on the amount of heat generated per unit time during combustion of the copper concentrate in the flash smelting furnace 6. This makes it possible to separate the control of the amount of excavation of the substance that causes the endothermic reaction from the control of the amount of excavation of the substance that causes the exothermic reaction, which results in improved controllability and makes it possible to further stabilize the operation of the flash smelting furnace.

As shown in FIG. 2, the control of the amount of copper concentrate cut from the second bin 2 based on the amount of heat generated per unit time when the copper concentrate is burned in the flash smelting furnace 6 is preferably indirectly controlled by the amount of copper concentrate cut from the first bin 1 per unit time. The reason for this is that the composition of copper concentrate is almost stable, so that simple and stable control can be achieved by adopting the amount of copper concentrate cut from the first bin 1 instead of the amount of heat generated per unit time when the copper concentrate is burned in the flash smelting furnace 6. In this way, by controlling the amount of neutralized precipitate and silicate-containing cooling material, which both cause an endothermic reaction, based on the amount of copper concentrate cut, the amount of heat generated in the flash smelting furnace 6 by the copper concentrate can be indirectly controlled (offset) using a relatively simple equipment configuration and control system, so that unstable operation in which the flash smelting furnace 6 is cooled too much by the endothermic reaction or overheated by the exothermic reaction can be prevented. In addition, uneven consumption of either the stock of miscellaneous raw materials or the stock of silicate-containing cooling material can be prevented.

The neutralized precipitate preferably contains gypsum. The silicate preferably contains oxide. Many of the neutralized precipitates obtained in copper smelting plants contain gypsum, which is produced by neutralizing sulfuric acid with lime. Since gypsum decomposes and absorbs a large amount of heat, the amount of gypsum cut out as a miscellaneous heat absorbing material can be controlled to exert its heat absorbing ability without excess or deficiency. On the other hand, silicate containing oxide contains less silicon dioxide that captures metal elements, so it is easy to grasp the excess or deficiency of the amount of silica stone added. By cutting them out from the same place, the composition of the slag produced from the flash smelting furnace 6 (for example, CaO: _SiO2 ratio) can be stabilized.

The method of discharging the copper smelting raw material from at least the first bin 1 and the second bin 2 onto the belt conveyor is not limited to the equipment shown in FIG. 1, and the copper smelting raw material may be discharged from the first bin 1 and the second bin 2 onto two belt conveyors. In this case, it is necessary to position both belt conveyors so that the powder falling from the downstream ends of the two belt conveyors falls (passes) at the same place. In addition, the destination of the copper smelting raw material discharged from at least the first bin 1 and the second bin 2 by the belt conveyor is not limited to the rotary dryer 4 shown in FIG. 1, and may be other drying equipment or a blending bin for blending multiple brands of copper concentrate.

Copper smelting raw materials were supplied to the flash furnace 6 by the supply method of the embodiment of the present invention using a dry copper smelting facility as shown in Figure 1, and were charged into the flash furnace 6 together with a flux mainly composed of silica to perform copper smelting. Specifically, as shown in Figure 2, only copper concentrate was charged into the first bin 1, and miscellaneous raw materials and silicate-containing cooling material were charged into the second bin 2. At that time, 20t of the miscellaneous raw materials and 20t of the silicate-containing cooling material were mixed by scooping and dropping them with a bucket of heavy equipment, and the resulting mixture 40t and the remaining part of the silicate-containing cooling material were scooped with the bucket of the heavy equipment in a ratio of 1 cup:3 cups and charged into the second bin 2. In this way, the mixture and silicate-containing cooling material were cut out from the second bin 2 and spread on the copper concentrate cut out from the first bin 1 and spread on the belt surface of the belt conveyor 3. The copper smelting raw materials cut out as described above were dried with a rotary dryer 4, and then charged into the flash furnace 6 for processing.

As a comparative example, 20 t of miscellaneous raw materials and 20 t of copper concentrate were mixed by scooping and dropping them into a bucket of heavy machinery, and the resulting mixture of 40 t and the remaining copper concentrate were scooped into the bucket of the heavy machinery in a ratio of 1:3 and poured into the first bin 1. Meanwhile, the second bin 2 contained only silicate-containing cooling material. In this way, the silicate-containing cooling material cut out from the second bin 2 was spread on top of the mixture and copper concentrate cut out from the first bin 1 and spread on the belt surface of the belt conveyor 3. Thereafter, the mixture was treated in the flash furnace 6 in the same manner as in the above example.

When the heat load in the flash furnace 6 fluctuates, the slag temperature in the flash furnace 6 fluctuates, so the slag temperature was measured five times a day during the one-month operation period of each of the example and the comparative example. As a result, the standard deviation of the slag temperature in the example was 6.7°C, and the standard deviation of the slag temperature in the comparative example was 8.6°C. This result corresponds to a significant difference in the F-test with a significance level of 5%, so it was found that the effect of reducing the temperature variation in the flash furnace can be obtained by supplying copper smelting raw materials according to the method that satisfies the requirements of the present invention. In addition, when the Cu content in the granulated slag was analyzed, it was about 95% of that in the comparative example in the example. The decrease of about 5% in the Cu content in the granulated slag in this example indicates that the copper production volume in the example was increased compared to the comparative example.

Reference Signs List 1 First bin 1a First excavation device 2 Second bin 2a Second excavation device 3 Belt conveyor 4 Rotary dryer 5 Air flow conveying device 6 Flash smelting furnace 7 Cyclone 8 Dry ore storage

Claims (3)

A method for supplying copper concentrate, silicate-containing cooling material, and miscellaneous raw materials as copper smelting raw materials to a flash smelting furnace, comprising: cutting the copper concentrate from a first bin and cutting the silicate-containing cooling material and miscellaneous raw materials from a second bin of at least two bins provided above a conveying means traveling toward the flash smelting furnace; and controlling the amount of copper concentrate cut from the second bin based on the amount of heat generated when the copper concentrate cut from the first bin is burned in the flash smelting furnace. The method for supplying copper smelting raw materials according to claim 1, characterized in that the miscellaneous raw materials contain gypsum and the silicate-containing coolant is an oxide. The method for supplying copper smelting raw materials according to claim 1 or 2, characterized in that the control of the amount of copper concentrate discharged from the second bin based on the amount of heat generated is an indirect control based on the amount of copper concentrate discharged from the first bin per unit time.

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