Method for recovering copper from zinc sulfate solution

Abstract

According to one embodiment of the present invention, a method for recovering copper from a zinc sulfate solution is provided, which is produced in a leaching process of dissolving zinc ore in sulfuric acid. The method includes a neutral leaching process for dissolving the zinc ore; a weak acid leaching process for dissolving the neutral leaching solution containing the dissolved zinc ore with sulfuric acid to produce a zinc sulfate solution; a copper removal process for removing copper dissolved in the zinc sulfate solution in the form of copper cement; a conditioning process for reducing the copper removal solution discharged from the copper removal process; a repulping process for repulping a conditioning cake, which is a solid material discharged from the conditioning process, with a zinc solution; and a purified leaching process for dissolving the repulping solution discharged from the repulping process with sulfuric acid to dissolve the copper contained in the repulping solution. The purified leaching solution discharged from the purified leaching process is then fed back to the weak acid leaching process after being charged with zinc cinder.

Description

[Technical Field]

[0001] The present invention relates to a method for recovering copper contained in a zinc sulfate solution. [Background technology]

[0002] The zinc smelting process generally consists of a roasting process, which oxidizes sulfide concentrate (ZnS), a leaching process, which dissolves the cinder (ZnO) produced in the roasting process in a sulfuric acid solution, and a multi-stage refining process to remove impurities. The resulting pure zinc sulfate solution is then electrolytically extracted to deposit zinc at the cathode. During the leaching process, various metal components contained in the zinc concentrate, such as iron (Fe), copper (Cu), nickel (Ni), cobalt (Co), and cadmium (Cd), are leached together. Among the leached metal components, copper, in particular, is discharged in the form of copper cement after a decoppering process, and this discharged copper cement can be recovered as pure copper through the copper smelting process.

[0003] Conventionally, copper has been recovered by dry smelting of by-products generated in the solution purification process of zinc smelting. However, the copper recovery rate in dry smelting is limited to around 50% to 70%, and the copper content in the slag generated by dry smelting is only 0.3% to 0.5%, meaning that the recovery rate of this valuable metal is low.

[0004] Furthermore, conventional pyrometallurgical processes have the drawback of requiring a large amount of energy and fossil fuels. Summary of the Invention [Problem to be solved by the invention]

[0005] This method allows for the recovery of 90% or more of the copper dissolved in the raw material of zinc hydrometallurgy by linking the by-products generated in the solution purification process when recovering copper contained in zinc sulfate solution to the copper removal process in the existing zinc hydrometallurgy process.

[0006] In addition, when recovering copper contained in a zinc sulfate solution, a method is provided that can minimize smelting costs by linking it to the copper removal process in the existing zinc hydrometallurgy process without requiring a separate smelting process for recovering copper.

[0007] In addition, the present invention provides a method for increasing the recovery rate of zinc in a zinc hydrometallurgy process by linking a by-product generated in a solution purification process, which is performed when recovering copper contained in a zinc sulfate solution, to an existing zinc hydrometallurgy process to further recover zinc contained in the by-product. [Means for solving the problem]

[0008] According to one embodiment of the present invention, a method for recovering copper from a zinc sulfate solution produced in a leaching process of dissolving zinc ore in sulfuric acid includes a neutral leaching process of dissolving the zinc ore; a weak acid leaching process of dissolving the neutral leaching solution containing the dissolved zinc ore with sulfuric acid to produce a zinc sulfate solution; a copper removal process of removing copper dissolved in the zinc sulfate solution in the form of copper cement; a conditioning process of reducing the copper removal solution discharged from the copper removal process; a repulping process of repulping a conditioning cake, which is a solid matter discharged from the conditioning process, with a zinc solution; and a purified leaching process of dissolving the repulping solution discharged from the repulping process with sulfuric acid to dissolve the copper contained in the repulping solution. The purified leaching solution discharged from the purified leaching process is neutralized by adding zinc cinder, and then re-introduced into the weak acid leaching process.

[0009] The zinc sulfate solution re-introduced into the weak acid leaching step may be re-introduced into the copper removal step.

[0010] The conditioning process may include reducing the decopperizing process solution to generate a conditioning process solution, treating the conditioning process solution with a thickener and a filter, and using the discharged solution as an iron precipitation process input solution to be input into the iron precipitation process, and discharging solids as the conditioning cake.

[0011] The iron precipitation step input solution may be input to an iron precipitation step in which iron oxide is recovered by a pressure oxidation step.

[0012] The iron precipitation step may generate an iron precipitation solution through the pressure oxidation step, treat the iron precipitation solution through a thickener and a filter, and transfer the discharged solution to the neutral leaching step, with the solid matter being discharged as iron oxide.

[0013] The repulping process may be carried out at a process temperature of 60°C to 80°C and a pH of 2.5 to 3.0.

[0014] In the repulping step, the concentration of the conditioning cake in the zinc solution may be 100 g / L to 200 g / L.

[0015] The concentration of sulfuric acid in the solution after the purified leaching step may be 25 g / L to 50 g / L.

[0016] In the cleaning leaching step, 85% or more of the copper contained in the conditioning cake may be dissolved.

[0017] In the leaching step, 92% or more of the iron and 98% or more of the zinc contained in the conditioning cake may be dissolved.

[0018] The purified leaching step may be carried out for 2 to 3 hours, the dissolution temperature may be 60 to 80°C, and the process pressure may be 1 to 2 atmospheres.

[0019] The pH of the weak acid leaching step may be 2.5 to 3.0.

[0020] The process time for the weak acid leaching step may be 3 to 4 hours. [Effects of the Invention]

[0021] According to the present invention, by-products generated in the solution purification process are reintroduced into the existing zinc hydrometallurgy process multiple times, thereby maximizing the recovery rate of copper dissolved in the raw materials of zinc hydrometallurgy.

[0022] In addition, by linking with the existing zinc smelting process without a separate smelting process for recovering copper, the cost required for smelting copper can be minimized.

[0023] Furthermore, by reintroducing the zinc contained in the by-products generated in the solution purification process into the zinc smelting process, the zinc recovery rate can be increased. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a process flow diagram for recovering copper according to one embodiment of the present invention. [Figure 2] FIG. 2 is a process flow diagram illustrating the repulping step, the clarification leaching step, and the neutralization step in a method for recovering copper from a zinc sulfate solution according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] In the general zinc smelting process, iron (Fe) and copper (Cu) are also leached into the sulfuric acid during the process of leaching zinc raw material into sulfuric acid, and the copper contained in the leachate is separated into solid and liquid, and then a strong reducing agent such as zinc powder is added to reduce and precipitate the dissolved copper (Cu) in the form of copper sulfate (CuSO4) into copper cement, which is a precipitate, and then removed.In addition, a considerable amount of iron is dissolved in the zinc sulfate solution, and the solution is sent to the Fe Precipitation process to remove the iron.

[0026] This invention aims to maximize the recovery rate of copper dissolved in the raw materials of zinc hydrometallurgy, and to recover more than 90% of copper ions contained in the leachate generated in the zinc smelting process.

[0027] FIG. 1 is a process flow diagram for recovering copper according to one embodiment of the present invention.

[0028] Referring to Figure 1, in the zinc smelting process, zinc-containing raw materials such as zinc concentrate, or the roasted zinc concentrate (cinder), or zinc ferrite are leached in sulfuric acid under atmospheric pressure to produce a zinc sulfate solution. The sulfuric acid remaining in the leaching process is neutralized with cinder to primarily remove impurities (neutral leaching process (S1)). The copper components leached with the raw material during the leaching process are not precipitated in the neutralization process and remain in the process solution after neutralization.

[0029] The solution obtained by dissolving the zinc-containing raw material and neutralizing it is called the neutral leaching solution, which is then dissolved again with sulfuric acid to produce a zinc sulfate solution (weak acid leaching step (S2)). The pH of the weak acid leaching step (S2) may be about 2.5 to 3.0, and the weak acid leaching step may be carried out in a thickener. The residence time of the zinc sulfate solution in the weak acid leaching step (S2) may be about 3 to 4 hours, and the weak acid leaching step may be carried out at a temperature of about 65°C.

[0030] The zinc sulfate solution discharged from the weak acid leaching process (S2) contains a large amount of dissolved copper. By adding a strong reducing agent such as zinc powder to the zinc sulfate solution, the copper (Cu) dissolved in the form of copper sulfate (CuSO4) can be reduced and precipitated as copper cement, a metallic copper powder, and removed (copper removal process (S3)). Copper cement can be recovered in the form of pure copper through a copper smelting process.

[0031] The post-copperization solution discharged from the decopperization process (S3) is input into the conditioning process (S4). In the conditioning process (S4), the post-copperization solution is input into a conditioning tank, passes through a thickener, and is filtered, with the solids being discharged as a conditioning cake. The post-conditioning process (S4) solution is then input into the iron precipitation process (S5), where iron oxide is recovered through a pressurized oxidation process. In the iron precipitation process (S5), the iron precipitation solution is input into an iron precipitation tank, passes through a thickener and a filter, and is discharged in the form of iron oxide. The solution is then transferred to the neutral leaching process (S1) as the post-iron precipitation solution. As the post-iron precipitation solution passes through the decopperization process (S3) and the iron precipitation process (S5), copper is discharged in the form of copper cement and iron is discharged in the form of iron oxide, resulting in a pure zinc sulfate solution with a high zinc content. The zinc sulfate solution is then transferred to a process for electrowinning and depositing zinc at the cathode.

[0032] The conditioning cake discharged in the conditioning step (S4) still contains valuable metals such as copper, iron, and zinc. To recover the metals contained in the conditioning cake, the copper, iron, zinc, etc. contained in the conditioning cake must be dissolved and then transported to a decopperizing step, an iron precipitation step, an electrolysis step, etc.

[0033] For this purpose, the conditioning cake discharged in the conditioning step (S4) is repulped in a zinc solution at a temperature of about 60°C to 80°C for about 1.5 hours (repulping step (S6)). The repulping step (S6) may be performed at a pH range of about 2.5 to 3.0, and the concentration of the conditioning cake in the zinc solution in the repulping step (S6) may be about 100 g / L to 200 g / L.

[0034] The post-repulping solution discharged in the repulping step (S6) is dissolved in sulfuric acid, thereby dissolving most of the copper contained in the post-repulping solution (cleaning / leaching step (S7)). The concentration of the added sulfuric acid can be approximately 25 g / L to 50 g / L. The cleansing / leaching step (S7) is carried out for approximately 2 to 3 hours, at a dissolution temperature of approximately 60 to 80°C and a process pressure of approximately 1 to 2 atmospheres. As a result of the above-mentioned cleansing / leaching step (S7), approximately 85% or more of the copper contained in the conditioning cake can be dissolved. Furthermore, in the cleansing / leaching step (S7), not only the copper but also iron, zinc, etc. contained in the conditioning cake are leached. Specifically, in the cleansing / leaching step (S7), approximately 92% or more of the iron and approximately 98% or more of the zinc contained in the conditioning cake are dissolved.

[0035] The post-cleaning leaching solution discharged in the leaching step (S7) is neutralized by adding zinc cinder (neutralization step (S8)) and then introduced back into the weak acid leaching step (S2). The post-cleaning leaching solution introduced into the weak acid leaching step (S2) is dissolved in sulfuric acid together with the post-neutral leaching solution discharged in the neutral leaching step (S1), and the resulting zinc sulfate solution is introduced into the copper removal step (S3).

[0036] The above-mentioned clean leaching process (S7) dissolves the large amounts of copper, iron, zinc, etc. contained in the conditioning cake, a by-product generated in the conditioning process (S4), and then feeds it back into the weak acid leaching process (S2) of the zinc smelting process, thereby re-recovering valuable metals, especially copper, that would otherwise be discarded as conditioning cake. This maximizes the recovery rate of copper dissolved in the raw materials used in zinc hydrometallurgy, and also increases the zinc recovery rate by re-feeding the zinc contained in the by-product back into the zinc smelting process. Furthermore, by linking the process to the existing zinc smelting process rather than using a separate copper smelting process to recover copper, the cost of copper smelting can be minimized.

[0037] FIG. 2 is a process flow diagram specifically illustrating the repulping step (S6), the purified leaching step (S7), and the neutralization step (S8) in a method for recovering copper from a zinc sulfate solution according to one embodiment of the present invention.

[0038] Referring to Figure 2, the conditioning cake discharged in the conditioning step (S4) was introduced into a repulping tank 10 together with a zinc solution. The amount of conditioning cake introduced into the repulping tank 10 was 120 T / D (tons per day), and the metal composition contained in the conditioning cake was measured.

[0039] The ratio of copper (Cu), iron (Fe), zinc (Zn), arsenic (As), and lead (Pb) contained in the conditioning cake [Table 1]

[0040] The repulping process in the repulping tank 10 was carried out at 60°C for 1.5 hours, and the concentration of conditioning cake in the solution introduced into the repulping process was measured to be 143 g / L. Next, the post-repulping process solution discharged from the repulping process was introduced into the purified leaching process reactor 20, and the concentration of the repulping slurry contained in the post-repulping process solution was measured.

[0041] Concentrations of copper (Cu), iron (Fe), zinc (Zn), arsenic (As), and lead (Pb) in the liquid after the repulping process [Table 2]

[0042] The repulping process liquor was introduced into the purified leaching process reactor 20 together with a zinc sulfate solution, and the sulfuric acid concentration in the zinc sulfate solution was measured to be 85 g / L. The concentrations of copper, iron, zinc, and arsenic in the zinc sulfate solution introduced into the purified leaching process reactor 20 were measured.

[0043] Concentrations of copper (Cu), iron (Fe), zinc (Zn), and arsenic (As) in the zinc sulfate solution added to the purified leaching process [Table 3]

[0044] The post-repulping liquor and the zinc sulfate solution introduced into the purified leaching reactor 20 reacted at 65°C for 2 hours, during which time most of the copper was dissolved. The concentrations and dissolution rates of copper (Cu), iron (Fe), zinc (Zn), arsenic (As), and lead (Pb) in the post-repulping liquor discharged from the purified leaching process were measured. The final acidity of the sulfuric acid (H2SO4) in the post-repulping liquor was measured to be 35g / L.

[0045] Concentrations of copper (Cu), iron (Fe), zinc (Zn), arsenic (As), and lead (Pb) in the solution after the purified leaching process [Table 4]

[0046] Referring to Table 4, after the completion of the clarified leaching process, the discharged clarified leaching solution was found to have dissolved more than 75% of copper, more than 87% of iron, and more than 97% of zinc. In other words, the valuable metals (copper, zinc, and iron) contained in the conditioning cake were mostly dissolved through the repulping and clarified leaching processes, and existed in the form of ions in the zinc sulfate solution. The clarified leaching solution was then fed into the Huma NT (Fumer NT 30) after adding zinc cinder. The clarified leaching solution was neutralized by zinc cinder in the Huma NT 30. The composition of the zinc cinder added to the clarified leaching solution is shown in Table 5 below.

[0047] Composition of zinc cinder added to the solution after the leaching process [Table 5]

[0048] In the Huma NT 30, the post-cleaning leaching solution and zinc cinder were reacted at 65°C for 1 hour, and the final acidity of the post-cleaning leaching solution after this process was pH 2.5. The post-cleaning leaching solution discharged from the Huma NT 30 after the neutralization process passes through a thickener 40, where the solids are removed to the outside, and the liquid post-neutralization solution is transferred to a settling tank 50 for the weak acid leaching process and then reintroduced into the weak acid leaching process. The reintroduced solution then undergoes a copper removal process, conditioning process, iron precipitation process, electrolysis process, etc., and the copper (Cu), iron (Fe), and zinc (Zn) contained in the reintroduced solution can be recovered as metals through the copper removal process, iron precipitation process, and electrolysis process. In addition, the post-clean leaching solution reintroduced into the weak acid leaching process may be subjected to the conditioning process, repulping process, clean leaching process, etc. again together with newly added zinc sulfate solution, and during this process, copper (Cu), iron (Fe), zinc (Zn), etc. that were not recovered may be recovered again. In other words, the by-product discharged in the form of conditioning cake may be subjected to the above-mentioned processes multiple times, and as the above processes are repeated, the recovery rates of copper (Cu), iron (Fe), and zinc (Zn) will continue to increase.

[0049] Although the present invention has been described herein with reference to certain embodiments, it will be apparent that various modifications and variations that would be apparent to one of ordinary skill in the art to which the present invention pertains can be made without departing from the spirit and scope of the present invention, and such modifications and variations are to be considered to fall within the scope of the appended claims.

Claims

1. 1. A method for recovering copper from a zinc sulfate solution produced in a leaching process in which zinc ore is dissolved in sulfuric acid, comprising: a neutral leaching step in which the zinc ore is dissolved; a weak acid leaching step in which the solution containing the zinc ore is dissolved in sulfuric acid to produce a zinc sulfate solution; a copper removal step of removing copper dissolved in the zinc sulfate solution in the form of copper cement; a conditioning step of reducing the post-copper removal solution discharged in the copper removal step; a repulping step in which the conditioning cake, which is a solid material discharged in the conditioning step, is repulped with a zinc solution; and a purified leaching process in which the post-repulping solution discharged in the repulping process is dissolved with sulfuric acid to dissolve copper contained in the post-repulping solution, The post-cleaning leaching solution discharged in the clean leaching step is neutralized by adding zinc cinder, and then re-added to the weak acid leaching step.

2. 2. The method for recovering copper from a zinc sulfate solution according to claim 1, wherein the zinc sulfate solution re-introduced into the weak acid leaching step is again fed into the copper removal step.

3. The conditioning step includes reducing the post-coppering step solution to generate a post-conditioning step solution, 2. The method for recovering copper from a zinc sulfate solution according to claim 1, wherein the solution after the conditioning step is treated with a thickener and a filter, and the discharged solution is used as an iron precipitation step feed solution to be fed to an iron precipitation step, and the solid matter is discharged as the conditioning cake.

4. 4. The method for recovering copper from a zinc sulfate solution according to claim 3, wherein the iron precipitation step input solution is input to an iron precipitation step in which iron oxide is recovered by a pressure oxidation step.

5. The iron precipitation step includes generating a post-iron precipitation solution through the pressure oxidation step, 5. The method for recovering copper from a zinc sulfate solution according to claim 4, wherein the solution after the iron precipitation step is treated with a thickener and a filter, and the discharged solution is transferred to the neutral leaching step, and the solid matter is discharged as iron oxide.

6. 2. The method for recovering copper from a zinc sulfate solution according to claim 1, wherein the repulping step is carried out at a process temperature of 60°C to 80°C and a pH of 2.5 to 3.

0.

7. 7. The method for recovering copper from a zinc sulfate solution according to claim 6, wherein in the repulping step, the concentration of the conditioning cake in the zinc solution is 100 g / L to 200 g / L.

8. 2. The method for recovering copper from a zinc sulfate solution according to claim 1, wherein the concentration of sulfuric acid in the solution after the purification leaching step is 25 g / L to 50 g / L.

9. 9. The method for recovering copper from a zinc sulfate solution according to claim 8, wherein the copper contained in the conditioning cake is dissolved by 85% or more in the cleaning leaching step.

10. 10. The method for recovering copper from a zinc sulfate solution according to claim 9, wherein in the purification leaching step, 92% or more of the iron and 98% or more of the zinc contained in the conditioning cake are dissolved.

11. 9. The method for recovering copper from a zinc sulfate solution according to claim 8, wherein the cleaning leaching step is carried out for 2 to 3 hours, the dissolution temperature is 60 to 80°C, and the process pressure is 1 to 2 atmospheres.

12. 2. The method for recovering copper from a zinc sulfate solution according to claim 1, wherein the pH of the weak acid leaching step is 2.5 to 3.

0.

13. 13. The method for recovering copper from a zinc sulfate solution according to claim 12, wherein the weak acid leaching step has a process time of 3 to 4 hours.

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