Method for recovering lead

Abstract

To provide a method for recovering lead that can increase the first-pass yield of the metal component.SOLUTION: The method for recovering lead includes a melting step of melting a lead raw material, a crushing step of crushing the speiss obtained in the melting step after solidification, a leaching step of leaching the crushed material obtained in the crushing step with an acid, and a step of recycling the residue obtained in the leaching step to the melting step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for recovering lead. [Background technology]

[0002] A known method for recovering lead involves melting and reducing a lead raw material obtained by copper smelting or the like in an electric furnace to produce crude lead, refining the crude lead, producing a lead anode using the lead as a raw material, and electrolytically refining the lead (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-234356 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0004] In an electric furnace, spices are generated between the metal phase and the slag phase during the smelting reduction process. The spices are then removed from the electric furnace together with the metal phase. Because the spices have high viscosity, metal components may become entrapped in the spices. Therefore, it is possible to return the spices to the copper smelting process. However, this may result in a low first-pass yield of the metal components and may also affect copper smelting operations.

[0005] In view of the above problems, an object of the present invention is to provide a method for recovering lead that can increase the first-pass yield of metal components. [Means for solving the problem]

[0006] The lead recovery method of the present invention includes a melting step of melting a lead raw material, a crushing step of crushing the spices obtained in the melting step after solidification, a leaching step of leaching the crushed material obtained in the crushing step with acid, and a step of returning the residue obtained in the leaching step to the melting step. The spices may contain at least one of Pb, Sn, Sb, and Bi, and at least one of Pb, Sn, Sb, and Bi contained in the spices may be concentrated in the residue. The spices may contain at least one of Fe, As, and Cu, and at least one of Fe, As, and Cu contained in the spices may be leached in the leaching step. The leaching solution obtained in the leaching step may be neutralized, and the precipitate may be treated in a copper smelting step. The lead raw material may include lead obtained during copper smelting. In the crushing step, the spices may be crushed until the particle size is 1 mm or less. In the leaching step, a leaching solution containing a mixture of sulfuric acid and hydrogen peroxide may be used. In the leaching step, the sulfuric acid concentration may be adjusted to 50 g / L or more and 400 g / L or less, and hydrogen peroxide may be added so that the oxidation-reduction potential (based on an Ag / AgCl electrode) is 150 mV or more. In the leaching step, the temperature of the leaching solution may be adjusted to 50°C or more and 90°C or less. [Effects of the Invention]

[0007] It is possible to provide a method for recovering lead that can increase the first-pass yield of metal components. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a method for recovering lead. [Figure 2] FIG. 1 is a diagram illustrating a Pb electric furnace. [Figure 3] FIG. 1 is a diagram showing the results of an example. DETAILED DESCRIPTION OF THE INVENTION

[0009] The lead raw material targeted in this embodiment contains at least lead (Pb) and may also contain tin (Sn), antimony (Sb), bismuth (Bi), iron (Fe), arsenic (As), copper (Cu), sulfur (S), silicon (Si), etc. Examples of lead raw materials include molten lead produced when reduced silver obtained by treating copper deposit (anode slime) produced by electrolytic refining in a copper smelting process is oxidized in an oxidation furnace, lead slag (lead sulfate) obtained by sulfuric acid leaching of dry flue dust generated in a melting furnace for recycled materials such as electronic components or a dry furnace for melting industrial waste, and lead carbonate obtained by treating lead sulfate with sodium carbonate. The lead raw material contains, for example, 20 to 40 mass% of Pb, 5 to 15 mass% of Sn, 1 to 10 mass% of Sb, 5 to 15 mass% of Bi, 5 to 15 mass% of Fe, and 1 to 10 mass% of As. The lead raw material may also contain other precious metals.

[0010] 1 is a diagram illustrating a lead recovery method according to this embodiment. The lead recovery method will be described below with reference to FIG.

[0011] (Melting process) As shown in Fig. 1, first, a lead raw material is melted and reduced in an electric furnace (Pb electric furnace). For example, coke is used as a reducing agent. For example, soda ash (sodium carbonate) is used as a solvent.

[0012] FIG. 2 illustrates a Pb electric furnace 100. As illustrated in FIG. 2, the Pb electric furnace 100 has an inlet 1 for charging the lead raw material. The lead raw material is charged into a furnace 2 through the inlet 1. The lead raw material is heated and melted by power from multiple electrodes 3. Through smelting reduction, the lead raw material separates into a metal phase 4 and a slag phase 5. Because the specific gravity of the slag phase 5 is smaller than that of the metal phase 4, the slag phase 5 floats on the metal phase 4. The metal phase 4 contains Pb, Sn, Sb, Bi, and precious metals. The slag phase 5 contains Fe, Cu, As, S, Si, and other elements. During the process of separation into the metal phase 4 and the slag phase 5, an intermediate layer called spice 6 containing spice components such as Fe, As, and Cu is formed between the metal phase 4 and the slag phase 5.

[0013] The side wall of the furnace 2 is provided with a metal discharge port 7 and a slag discharge port 8. The metal discharge port 7 is located at a lower position than the slag discharge port 8. This allows the metal phase 4 to be discharged from the metal discharge port 7, and the slag phase 5 to be discharged from the slag discharge port 8. The spice 6 is discharged together with the metal phase 4 from the metal discharge port 7.

[0014] The metal phase 4 and spice 6 extracted from the metal extraction port 7 are cooled and solidified, and then chipped to separate the metal phase 4 and spice 6.

[0015] However, spice 6 separated from metal phase 4 contains some of the metal components of metal phase 4. For example, spice 6 contains at least one of Pb, Sn, Sb, and Bi as a metal component. Furthermore, spice 6 contains at least one of Fe, As, and Cu as a spice component. Therefore, it is conceivable to feed spice 6 separated from metal phase 4 back into a copper smelting furnace as a repeating material. However, this would result in a low first-pass rate for the metal components contained in spice 6. The first-pass rate refers to the percentage of material fed into a Pb electric furnace that proceeds to the next process in one pass without being repeated. Furthermore, these metal components are smelting inhibitors in the copper smelting process and may affect copper smelting operations. In particular, the proportion of recycled materials fed into copper smelting furnaces has been increasing in recent years, making it desirable to reduce the amount of repeating material fed into copper smelting furnaces.

[0016] Therefore, it is possible to return the spice 6 separated from the metal phase 4 to the Pb electric furnace 100. However, it is preferable not to return spice components such as Fe, As, and Cu contained in the spice 6 to the Pb electric furnace 100. This is because returning the spice components to the Pb electric furnace 100 increases the amount of spice generated. Therefore, it is possible to separate the spice 6 into metal components such as Pb, Sn, Sb, and Bi and spice components such as Fe, As, and Cu. However, because the spice 6 melted in the Pb electric furnace 100 has high viscosity, the settling speed of metal particles suspended in the spice 6 is slow, and the metal components may be entrained. Therefore, it is difficult to separate the spice 6 into metal components such as Pb, Sn, Sb, Bi, and precious metals and spice components such as Fe, As, and Cu.

[0017] (Crushing process) Therefore, in this embodiment, the solidified spice 6 is crushed. The crusher used for crushing is not particularly limited, and for example, a ball mill or the like can be used. For example, by attaching a screen to the ball mill, the spice can be crushed to the desired particle size. From the viewpoint of improving the leaching rate in the leaching step described below, the particle size of the crushed spice 6 is preferably 1 mm or less, and more preferably 0.5 mm or less. Note that the particle size here means the maximum diameter of each particle.

[0018] (Leaching process) Next, the crushed spice 6 is subjected to a leaching process using an acid as a leaching solution. By using an acid as a leaching solution, spice components contained in the spice 6, such as Fe, As, and Cu, are leached into the leaching solution. Metal components contained in the spice 6 are not leached into the leaching solution as much as the spice components.

[0019] The leaching solution used in the leaching step is not particularly limited. Any solution capable of leaching the spice components contained in Spice 6 can be used as the leaching solution. For example, since the spice components contained in Spice 6 are thought to exist in the form of elemental metals or alloys, it is preferable that the leaching solution used in the leaching step also functions as an oxidizing agent. Therefore, it is preferable that the leaching solution further contains hydrogen peroxide in addition to a mineral acid such as sulfuric acid.

[0020] For example, when a mixture of sulfuric acid and hydrogen peroxide is used as the leaching solution, the sulfuric acid concentration is preferably 50 g / L to 400 g / L, and the hydrogen peroxide concentration is preferably added so that the oxidation-reduction potential (based on an Ag / AgCl electrode) is 150 mV or higher. In addition, the temperature of the leaching solution is preferably adjusted to 50°C to 90°C during the leaching step.

[0021] The residue obtained in the leaching process contains metal components entrained from the metal phase 4. Therefore, the residue obtained in the leaching process is returned to the Pb electric furnace 100. By returning the residue to the Pb electric furnace 100 after the leaching process, the amount of spice components repeatedly fed to the Pb electric furnace 100 is reduced. As a result, the amount of spice generated in the Pb electric furnace 100 is reduced.

[0022] (precipitation process) The leaching solution obtained in the leaching process is neutralized to precipitate spice components such as Fe, As, and Cu. For example, the leaching solution is neutralized using caustic soda until the pH of the leaching solution is between 6 and 8. The resulting precipitate contains concentrated spice components such as Fe, As, and Cu, so it is then repeatedly fed into a copper smelting furnace such as a flash furnace.

[0023] The metal phase 4 recovered from the Pb electric furnace 100 is subjected to a process for individually recovering each contained metal element. For example, it is subjected to a process for individually recovering Pb, Sn, Sb, and Bi. For example, Pb can be purified to prepare a lead anode, and lead can be recovered by electrolytic refining.

[0024] According to this embodiment, by performing the leaching process on the spice 6, even if the spice 6 contains metal components such as Pb, Sn, Sb, and Bi from the metal phase 4, it can be separated into a residue containing a relatively large amount of the metal components and a post-leaching solution containing a relatively large amount of spice components such as Fe, As, and Cu. This makes it possible to return metal components such as Pb, Sn, Sb, and Bi to the Pb electric furnace 100 while suppressing the amount of spice generated in the Pb electric furnace 100. In this case, since it is no longer necessary to return metal components such as Pb, Sn, Sb, and Bi to the copper smelting furnace, the first-pass rate of metal components such as Pb, Sn, Sb, and Bi can be increased. [Example]

[0025] (Example) Spices generated in a Pb electric furnace were recovered according to the lead recovery method of the embodiment below. The composition of the recovered spices is shown in Table 1. As shown in Table 1, in addition to spice components such as Fe, As, and Cu, the spices also contained metal components such as Sb, Sn, and Pb. [Table 1]

[0026] 50 g of spices crushed to a particle size of 1 mm or less were added to 445 mL of dilute sulfuric acid (sulfuric acid concentration: 400 g / L) and stirred. 55 mL of hydrogen peroxide (hydrogen peroxide concentration: 35 mass%) was then added to prepare a leachate. The leachate was then heated to between 65°C and 70°C. Samples were taken 3, 6, 24, and 48 hours after the leachate temperature reached 65°C. After the samples were taken at 3, 6, and 24 hours, 20 mL of hydrogen peroxide was added each time.

[0027] The components of the leaching solution were analyzed. The results are shown in Table 2 and Figure 2. The percentages in Table 2 indicate the leaching rate. As shown in Table 2 and Figure 3, most of the spice components Fe and Cu were leached out, and about 30% of the remaining spice component As was leached out. On the other hand, the metal components Sb, Sn, and Pb all had leaching rates of less than 10%, meaning they were hardly leached out at all. [Table 2]

[0028] From the above results, it was found that even if the spice components contain metal components, the spice components and the metal components can be separated by leaching.

[0029] 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 defined in the claims.

[0030] According to one embodiment of the present invention, it is possible to increase the first-pass yield rate of metal components such as Pb, Sn, Sb, and Bi. Therefore, one embodiment of the present invention may contribute to the achievement of Goal 9 "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation" and Goal 12 "Ensure sustainable consumption and production patterns" of the United Nations-led Sustainable Development Goals (SDGs) by promoting waste reuse and improving resource utilization efficiency. [Explanation of symbols]

[0031] 1 Inlet 2 furnace 3 electrodes 4 Metallic Phase 5 Slag phase 6. Spice 7 Slag outlet 8 Metal outlet 100 Pb electric furnace

Claims

1. a melting step of melting a lead raw material; A crushing step of crushing the spice obtained in the melting step after solidification; a leaching step of leaching the crushed material obtained in the crushing step with acid; a step of returning the residue obtained in the leaching step to the melting step; A method for recovering lead, including:

2. The spice contains at least one of Pb, Sn, Sb, and Bi, 2. The method for recovering lead according to claim 1, wherein at least one of Pb, Sn, Sb, and Bi contained in the spice is concentrated in the residue.

3. The spice contains at least one of Fe, As, and Cu, 2. The method for recovering lead according to claim 1, wherein at least one of Fe, As, and Cu contained in the spice is leached in the leaching step.

4. 2. The method for recovering lead according to claim 1, wherein the leaching solution obtained in the leaching step is neutralized, and the precipitate is treated in a copper smelting step.

5. 2. The method for recovering lead according to claim 1, wherein the lead raw material comprises lead obtained in a copper smelting process.

6. 2. The method for recovering lead according to claim 1, wherein the spice is crushed to a particle size of 1 mm or less in the crushing step.

7. 2. The method for recovering lead according to claim 1, wherein a leaching solution containing a mixture of sulfuric acid and hydrogen peroxide is used in the leaching step.

8. 8. The method for recovering lead according to claim 7, wherein in the leaching step, the sulfuric acid concentration is set to 50 g / L or more and 400 g / L or less, and hydrogen peroxide is added so that the oxidation-reduction potential (based on an Ag / AgCl electrode) is 150 mV or more.

9. 8. The method for recovering lead according to claim 7, wherein the temperature of the leaching solution is adjusted to 50°C or higher and 90°C or lower in the leaching step.

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