Method for operating copper smelting furnace

Abstract

To provide a method for operating a copper smelting furnace by which a recycled raw material can be treated in the copper smelting furnace while suppressing the loss of valuables.SOLUTION: In a method for operating a copper smelting furnace, when a copper smelting raw material containing copper concentrate and a recycled raw material containing metallic Cu is melted and treated in the copper smelting furnace, the treatment amount of the recycled raw material is adjusted according to the amount of an Fe source containing Cr contained in the recycled raw material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for operating a copper smelting furnace. [Background technology]

[0002] In a copper smelting furnace, reactive gas is introduced along with smelting raw materials such as copper concentrate and solvent. The copper concentrate undergoes an oxidation reaction in the reactive gas, producing matte and slag at the bottom of the copper smelting furnace. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2023 / 228912 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the proportion of recycled materials in smelting raw materials has been increasing. In copper smelting furnaces, a problem that arises when increasing the amount of recycled materials processed is when the solubility of the metallic Cu (copper or copper alloy) contained in the recycled materials in the matte exceeds the limit, resulting in the coexistence of metallic Cu phases in the Cu matte. In this situation, metal accumulates at the bottom of the copper smelting furnace, causing operational problems and must be avoided.

[0005] Therefore, it is considered to suppress the coexistence of metallic Cu phase in Cu matte by adjusting the amount of recycled raw material fed into the copper smelting furnace. However, depending on the components contained in the recycled raw material, the metallic Cu phase may coexist even if the amount of recycled raw material is adjusted.

[0006] Through extensive research by the present inventors, it has been found that when a recycled raw material contains an Fe source containing Cr (chromium), a metallic Cu phase or a metallic Fe phase may coexist in matte 5 even if the amount of recycled raw material is adjusted. Therefore, as a result of further extensive research by the present inventors, it has been found that the dissolution rate of the Cr-containing Fe source into matte 5 is slower when the recycled raw material contains an Fe source containing Cr than when the recycled raw material contains pure Fe, resulting in a significant decrease in the dissolution rate of the Fe source. This is thought to be because, when the recycled raw material contains an Fe source containing Cr, a matte phase in which a phase containing a large amount of Cr is dispersed around the Fe source, and a slag phase in which a spinel formed from Cr and Fe is dispersed, are formed around the Fe source, increasing the viscosity of the molten metal and inhibiting the distribution of elements.

[0007] Therefore, it is conceivable to remove stainless steel contained in recycled raw materials in advance (see, for example, Patent Document 1). However, in order to remove stainless steel contained in recycled raw materials, it is necessary for the stainless steel to be uniform in size, and it is also affected by coexisting metals and non-metals. In addition, physical separation is also subject to size restrictions. Therefore, it is difficult to remove nearly 100% of the stainless steel. On the other hand, if an attempt is made to increase the removal rate to nearly 100%, there is a problem in that valuable materials such as Cu and Au will be lost. If valuable materials are lost, there is a risk that profitability in recycling smelting will not be ensured.

[0008] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a copper smelting operation method that can process recycled raw materials in a copper smelting furnace while suppressing loss of valuable materials. [Means for solving the problem]

[0009] In a copper smelting operation method according to the present invention, when a copper smelting raw material containing copper concentrate and a recycled raw material containing metallic Cu is melted and processed in a copper smelting furnace, the processing amount of the recycled raw material is adjusted depending on the amount of an Fe source containing Cr contained in the recycled raw material.

[0010] In the copper smelting operation method, the matte formation limit of the recycled material may be determined, a proportion of Fe present in the recycled material as an Fe source containing Cr may be determined according to the Cr content of the recycled material, and the matte formation limit may be corrected according to the proportion, thereby adjusting the processing amount of the recycled material. A first Fe content in the estimated matte composition may be determined by calculating an estimated matte composition assuming that raw materials excluding the recycled material from the copper smelting raw material are melted together with the copper concentrate to reach an equilibrium state, and a second Fe content may be determined by adding up the first Fe content under the assumption that all Fe contained in the recycled material is pure Fe, and a proportion of the second Fe content that transfers to slag during the residence time of the copper smelting raw material in the copper smelting furnace may be estimated to determine the matte formation limit of the recycled material. When the processing amount of the metallic Cu contained in the recycled material exceeds the Cu solubility of the matte when an equilibrium state is reached in the copper smelting furnace, the processing amount of the recycled material may be adjusted based on the first Fe content and the Cu and S contents in the matte so as not to exceed the corrected matte formation limit amount. A Cr-containing Fe source may be separated from the recycled material, and the amount of the Cr-containing Fe source may be reduced before the material is charged into the copper smelting furnace. In the step of reducing the amount of the Cr-containing Fe source, the Cr-containing Fe source may be separated by physical separation.

[0011] Another copper smelting operation method according to the present invention includes, when melting and processing a copper smelting raw material containing copper concentrate and a recycled raw material containing metallic Cu in a copper smelting furnace, determining a matte-forming limit amount of the recycled raw material, determining a proportion of Fe present in the recycled raw material as an Fe source containing Cr in accordance with the amount of Cr contained in the recycled raw material, correcting the matte-forming limit amount in accordance with the proportion, and adjusting the amount of an S source added to the copper smelting furnace so that the corrected matte-forming limit amount is not exceeded.

[0012] In the copper smelting operation method, a first Fe content in the estimated matte composition may be obtained by calculating an estimated matte composition when it is assumed that raw materials excluding the recycled material from the copper smelting raw materials are melted together with the copper concentrate and an equilibrium state is reached, and a second Fe content is obtained by adding up the first Fe content under the assumption that all Fe contained in the recycled material is pure Fe, and the matte formation limit amount of the recycled material may be obtained by estimating a proportion of the second Fe content that transfers to the slag during a residence time of the copper smelting raw material in the copper smelting furnace. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a copper smelting operation method that can process recycled raw materials in a copper smelting furnace while suppressing loss of valuable materials. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram illustrating a schematic configuration of a flash furnace for copper smelting according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating the details of a concentrate burner 4. [Figure 3] FIG. 1 is a phase diagram showing the solubility of Cu in the matte. DETAILED DESCRIPTION OF THE INVENTION

[0015] (Embodiment) FIG. 1 is a diagram schematically illustrating the configuration of a flash smelting furnace 100, which is a type of copper smelting furnace. As shown in FIG. 1, the flash smelting furnace 100 includes a reaction shaft 1 in which concentrate and reaction gas are mixed, a settler 2, and an uptake 3. A concentrate burner 4 is provided on the ceiling of the reaction shaft 1. The concentrate burner 4 supplies copper concentrate, solvent, recycled raw materials, etc. (hereinafter, these solid raw materials will be referred to as copper smelting raw materials) into the reaction shaft 1, as well as a main reaction blast gas, an auxiliary reaction gas, and a dispersion gas (which also contributes to the reaction). For example, the main reaction blast gas and the auxiliary reaction gas are oxygen-enriched air, and the dispersion gas is air or oxygen-enriched air.

[0016] FIG. 2 is a diagram illustrating the details of the concentrate burner 4, and is an explanatory diagram showing the input section 10 through which the copper smelting raw material, the main reaction gas, the auxiliary reaction gas, and the dispersion gas are input to the reaction shaft 1.

[0017] The input section 10 of the concentrate burner 4 is equipped with a lance 16, which is provided with a first passage 11 through which a dispersion gas passes and a fourth passage 14 through which a reaction auxiliary gas passes. The fourth passage 14 is provided in the center of the lance 16, and the first passage 11 is provided around the fourth passage 14. The input section 10 also has a second passage 12 as a raw material flow path provided outside the lance 16, more specifically, on the outer periphery of the lance 16. The input section 10 further has a third passage 13 provided outside the second passage 12, more specifically, on the outer periphery of the second passage 12, through which a reaction main blast gas passes. The third passage 13 is formed by a tubular portion provided to surround the second passage 12 and communicates with a funnel-shaped air chamber 17 provided above it. The second passage 12 and the third passage 13 are separated by a cylindrical partition wall 21.

[0018] The first passage 11 supplies dispersion gas into the reaction shaft 1. The second passage 12 supplies concentrate into the reaction shaft 1. The third passage 13 supplies main reaction gas from the air chamber 17 into the reaction shaft 1. The fourth passage 14 supplies auxiliary reaction gas into the reaction shaft 1.

[0019] A hollow truncated cone-shaped dispersion cone 15 is formed at the tip (lower end) of the lance 16. A plurality of supply holes 152 are formed in a lower part 151 of the side surface of the dispersion cone 15 to discharge the dispersion gas that has passed through the first passage 11 into the reaction shaft 1. The supply holes 152 are arranged so that the gas is discharged in the normal direction to the bottom circle of the dispersion cone 15.

[0020] When copper smelting raw materials are fed into the reaction shaft 1 from the concentrate burner 4, the copper concentrate containing sulfides undergoes an oxidation reaction according to the following reaction formula (1) and separates into matte 5 and slag 6 (slag solution) at the bottom of the reaction shaft 1, as shown in Figure 1. In the following reaction formula (1), Cu2S·FeS corresponds to the main component of matte 5, and FeO·SiO2 corresponds to the main component of slag 6. Silicate ore is used as the solvent. CuFeS2+SiO2+O2→Cu2S·FeS+FeO·SiO2+SO2+ Reaction heat (1)

[0021] The recycled raw material may contain metallic components. If the amount of metallic components is small, the metallic components are sulfidized to form matte 5 during the process of falling from the concentrate burner 4. Therefore, no metal phase is generated.

[0022] However, as the amount of recycled raw materials processed increases, the proportion of metallic Cu (copper or copper alloy) in copper smelting raw materials tends to increase. In recent years, the proportion of metallic Cu in copper smelting raw materials has sometimes been 6.0 mass% or more and 28.0 mass% or less, or 9.0 mass% or more and 18.0 mass% or less, or 9.0 mass% or more and 12.0 mass% or less.

[0023] As the proportion of metallic Cu in copper smelting raw materials increases, metallic Cu is not completely sulfidized during the process of falling from the concentrate burner 4 and falls as metallic Cu. While metallic Cu dissolves in matte 5 to a certain extent, there is a solubility limit. Figure 3 is a phase diagram showing the solubility of Cu in matte at 1250°C. In Figure 3, "matte(l)" indicates the range in which metallic Cu can dissolve in matte. "matte(l) + Cu(l)" indicates the range in which metallic Cu cannot dissolve in matte and a metal phase is formed. The phase diagram in Figure 3 is based on "Report of the Selection and Research Institute, Takazai and Yazawa, 1983."

[0024] In this embodiment, the processing amount of the recycled raw material in the flash smelting furnace 100 is adjusted according to the amount of the Cr-containing Fe source, such as stainless steel, contained in the recycled raw material. This eliminates the need to pre-remove stainless steel and other materials from the recycled raw material more than necessary, and allows the recycled raw material to be processed in a copper smelting furnace while suppressing losses of Cu, Au, and other elements that result from pre-removal. Furthermore, for example, when the Fe source contains Cr, the processing amount of the recycled raw material can be adjusted taking into account a decrease in the amount of dissolved Fe source.

[0025] For example, when the recycled raw material contains a large amount of the Fe source containing Cr, the amount of recycled raw material mixed with the copper smelting raw material can be reduced to suppress the formation of a metal phase in the matte 5. Conversely, when the recycled raw material contains a small amount of the Fe source containing Cr, the amount of recycled raw material mixed with the copper smelting raw material can be increased to increase the processing amount of the recycled raw material.

[0026] For example, the matte formation limit of the recycled raw material is determined. The matte formation limit here can be defined as the limit of processing amount at which, under predetermined conditions (holding time, slag composition, matte composition, oxygen potential, etc.), if recycled raw material is added in excess of this limit, a metal phase will remain in the matte. Next, the proportion of Fe present as an Fe source containing Cr in the recycled raw material is determined according to the amount of Cr contained in the recycled raw material, and the matte formation limit can be corrected according to this proportion, thereby adjusting the processing amount of the recycled raw material.

[0027] The matte formation limit can be determined, for example, by conducting a preliminary experiment as follows. First, a simulated recycled material sample is used that has a similar composition (Cu, Fe, S) to the matte and slag used in actual operation and the expected recycled material. Next, multiple crucible tests are conducted under conditions that simulate the actual operating conditions, with the amount of recycled material added being varied. Next, the conditions for the maximum amount of recycled material added that does not leave any undissolved recycled material in the matte after the crucible test are identified. This maximum amount of recycled material added that does not leave any undissolved recycled material is defined as the matte formation limit.

[0028] Alternatively, the matte formation limit may be determined by the following procedure. For example, the first Fe content in the estimated matte composition is determined by calculating an estimated matte composition when copper smelting raw materials, excluding recycled materials, are melted together with copper concentrate and an equilibrium state is reached. Next, assuming that all Fe contained in the recycled materials is pure Fe, the second Fe content is determined by adding the first Fe content. Next, the proportion of the second Fe content that transfers to slag 5 during the residence time of the copper smelting raw materials in the flash smelting furnace 100 is estimated, and the matte formation limit of the recycled material is determined under the assumption that S (sulfur) and Cu (copper) contained in the estimated matte and recycled materials do not transfer to slag 5.

[0029] For example, let's say that the matte limit for recycled material is 3g for 10g of matte. Next, let's assume that one-third of the Fe in the recycled material exists as SUS, depending on the amount of Cr contained in the recycled material. Next, let's assume that when the Fe is replaced by SUS after a specified holding time, the amount that dissolves is about 50%. In this case, 3 x (1 / 3) x 50% = 0.5g does not dissolve due to the influence of SUS, so we can estimate that the R material will eventually matte down to 2.5g after the specified holding time.

[0030] For example, it may be assumed that all of the Fe source contained in the recycled raw material is stainless steel.

[0031] Alternatively, it may be assumed that a portion of the Fe source contained in the recycled raw material is stainless steel. For example, suppose that the recycled raw material contains 1 mass% Cr and 10 mass% Fe. In this case, if the Cr-containing Fe source is SUS304, the Fe:Cr (mass% ratio) will be 4.5:1, so it can be assumed that 4.5 mass% of the Fe source is the Cr-containing Fe source, and the remaining 5.5 mass% is the Cr-free Fe source. If the Cr-containing Fe source in the recycled raw material can be analyzed, the proportion of the Cr-containing Fe source among the Fe sources contained in the recycled raw material can be estimated based on the results of the analysis.

[0032] For example, when the processing amount of metallic Cu contained in the recycled raw material exceeds the Cu solubility in matte 5 when the equilibrium state is reached in the flash smelting furnace 100, the matte formation limit amount of the recycled raw material may be corrected by the above-mentioned method based on the first Fe content and the Cu and S contents in matte 5, and the processing amount of the recycled raw material may be adjusted so as not to exceed the corrected matte formation limit amount.

[0033] Furthermore, instead of adjusting the amount of recycled raw material processed so as not to exceed the matte formation limit corrected by the above method, the amount of S source added to the flash smelting furnace 100 can also be adjusted so as not to exceed the corrected matte formation limit. The S source is not particularly limited as long as it contains sulfur, and for example, S-containing waste slag generated in the dressing process of non-ferrous metal raw materials can be used.

[0034] The Cr-containing Fe source may be separated from the recycled raw material, and the amount of the Cr-containing Fe source may be reduced before charging the recycled raw material into the flash smelting furnace 100. For example, when the ratio of the Cr-containing Fe source to all Fe sources in the recycled raw material exceeds a predetermined value, the Cr-containing Fe source may be separated. In this case, the Cr-containing Fe source does not need to be separated more than necessary. For example, it is preferable to separate the Cr-containing Fe source to such an extent that the ratio of the Cr-containing Fe source to all Fe sources in the recycled raw material is reduced to an acceptable value. In this way, the Cr-containing Fe source in the recycled raw material can be reduced and losses of valuable materials such as Cu and Au can be suppressed.

[0035] For example, physical sorting such as magnetic sorting can be applied to sort out Fe sources containing Cr. Alternatively, Fe sources containing Cr can be sorted out by identifying each material by color based on an image of the recycled raw materials.

[0036] In the above embodiment, a flash smelting furnace has been described as an example of a copper smelting furnace, but the copper smelting operation method according to this embodiment can also be applied to copper smelting furnaces other than flash smelting furnaces. In particular, the copper smelting furnace operation method according to this embodiment is preferably applied to a copper smelting furnace. [Example]

[0037] Experiments were carried out in which metallic Cu and metallic Fe were added to the slag-matte two-phase coexistence state.

[0038] The crucible was filled with the first metal sample, matte, and slag in that order. The first metal sample was prepared by mixing weighed amounts of metallic Cu and weighed amounts of metallic Fe (Fe without Cr) in a predetermined ratio (Cu:Fe = 0.76:0.24 by mass%). The crucible was heated and held at 1250°C for 2 hours to melt the sample in the crucible.

[0039] The crucible was cooled, and the presence or absence of metallic components in the matte was confirmed. Specifically, the presence or absence of metallic components in the matte was evaluated by taking out the cooled matte sample and observing the cross section from the edge, and using the presence or absence of metallic components of a certain size or larger and containing impurity components as an indicator.

[0040] As a result of the test, it was confirmed that the first metal sample dissolved into the slag or matte in an amount of 8 mass% to 10 mass% of the matte.

[0041] Next, a test was conducted using a second metal sample instead of the first metal sample, with the same holding time. The ratio of metallic Cu and Fe in the second metal sample was adjusted to be the same as that in the first metal sample, and the amount of Fe was adjusted so that all of it was derived from stainless steel. Analysis confirmed that up to 5% to 6% of the second metal sample dissolved into the slag or matte. This result indicates that the soluble amount of metal was 50% to 75% of that in the first metal sample.

[0042] To determine the cause of the decrease in the soluble amount of metal when the second metal sample was used, the cross section of the matte sample was re-examined after the test. A slag phase was identified near the undissolved stainless steel. EPMA analysis of the slag phase revealed that Cr and Fe were detected in the same location, and that S and Si were almost completely absent in the location where Cr and Fe were strongly detected. This suggests that a spinel with the composition formula FeCr2O4 was formed. This phenomenon was not observed when the first metal sample was used, confirming that the dissolution mechanisms of Fe and stainless steel are different. When stainless steel was used, Cr formed a spinel with Fe, which prevented element partitioning, thereby inhibiting the dissolution of the stainless steel and significantly slowing the dissolution rate compared to metallic Fe.

[0043] Therefore, the ratio of the Fe source containing Cr can be estimated based on the amount of Cr contained in the recycled raw material (for example, it can be assumed that all of the Cr is derived from stainless steel), and the soluble amount of the metal for the Fe source containing Cr can be estimated to be 50% to 75%. Then, the matte-forming limit of the recycled raw material can be determined by the method described in the above embodiment. Then, it becomes possible to adjust the amount of recycled raw material processed or the amount of S source input so as not to exceed the matte-forming limit.

[0044] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims.

[0045] According to one embodiment of the present invention, by contributing to technological innovation in copper smelting, it is possible to contribute to Goal 9 of the United Nations' Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote inclusive and sustainable industrialization, and foster innovation." Furthermore, according to one embodiment of the present invention, by promoting the use of recycled materials, it is possible to contribute to Goal 12 of the United Nations' Sustainable Development Goals (SDGs), "Ensure sustainable consumption and production patterns." [Explanation of symbols]

[0046] 1 Reaction Shaft 2 Setra 3 Uptake 4 Concentrate burner 5. Matt 6. Slug 10 Input section 11 1st aisle 12 2nd aisle 13 3rd aisle 14 4th aisle 16 Lance 100 Flash furnace

Claims

1. A method for operating a copper smelting furnace, comprising: melting and processing a copper smelting raw material containing copper concentrate and a recycled raw material containing metallic Cu in the copper smelting furnace; adjusting a processing amount of the recycled raw material according to an amount of an Fe source containing Cr contained in the recycled raw material.

2. The matting limit of the recycled raw material is determined, 2. The method for operating a copper smelting furnace according to claim 1, further comprising determining a proportion of Fe present as an Fe source containing Cr in the recycled material according to an amount of Cr contained in the recycled material, correcting the matte formation limit amount according to the proportion, and adjusting a processing amount of the recycled material.

3. a first Fe content in the estimated matte composition is calculated by assuming that raw materials excluding the recycled raw material from the copper smelting raw materials are melted together with the copper concentrate and reach an equilibrium state; Assuming that all of the Fe contained in the recycled raw material is pure Fe, a second Fe content is calculated by adding up the first Fe content; 3. The method for operating a copper smelting furnace according to claim 2, further comprising estimating a proportion of the second Fe content that transfers to slag during a residence time of the copper smelting raw material in the copper smelting furnace, thereby determining a matte formation limit amount of the recycled raw material.

4. 4. The method for operating a copper smelting furnace according to claim 3, wherein, when a processing amount of the metallic Cu contained in the recycled raw material exceeds the Cu solubility of the matte when an equilibrium state is reached in the copper smelting furnace, a processing amount of the recycled raw material is adjusted based on the first Fe content and the Cu and S contents in the matte so that the corrected matte formation limit amount is not exceeded.

5. 2. The method for operating a copper smelting furnace according to claim 1, further comprising separating an Fe source containing Cr from the recycled raw material, reducing the amount of the Fe source containing Cr, and then charging the reduced Fe source into the copper smelting furnace.

6. 6. The method for operating a copper smelting furnace according to claim 5, wherein in the step of reducing the amount of the Fe source containing Cr, the Fe source containing Cr is separated by physical separation.

7. In a copper smelting furnace, when melting and processing copper smelting raw materials including copper concentrate and recycled raw materials containing metallic Cu, The matting limit of the recycled raw material is determined, a method for operating a copper smelting furnace, the method comprising: determining a proportion of Fe present in the recycled material as an Fe source containing Cr according to an amount of Cr contained in the recycled material; correcting the matte formation limit amount according to the determined proportion; and adjusting an amount of an S source added to the copper smelting furnace so that the corrected matte formation limit amount is not exceeded.

8. a first Fe content in the estimated matte composition is calculated by assuming that raw materials excluding the recycled raw material from the copper smelting raw materials are melted together with the copper concentrate and reach an equilibrium state; Assuming that all of the Fe contained in the recycled raw material is pure Fe, a second Fe content is calculated by adding up the first Fe content; 8. The method for operating a copper smelting furnace according to claim 7, further comprising estimating a proportion of the second Fe content that transfers to slag during a residence time of the copper smelting raw material in the copper smelting furnace, thereby determining a matte formation limit amount of the recycled raw material.

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