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 separation step of separating the crushed material obtained in the crushing step into lightweight material and heavy material, and a step of recycling the heavy material to the melting step.SELECTED DRAWING: Figure 3

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 lead raw materials obtained by copper smelting or the like in an electric furnace to produce crude lead, refining the crude lead, and using this as a raw material to prepare lead anodes, which are then subjected to electrolytic refining (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 process for melting a lead raw material, a crushing process for crushing the spice obtained in the melting process after solidification, a separation process for separating the crushed material obtained in the crushing process into light materials and heavy materials, and a process for returning the heavy materials to the melting process.

[0007] The spice may contain at least one of Pb, Sn, Sb, and Bi, and the concentration of at least one of Pb, Sn, Sb, and Bi contained in the spice may be higher in the heavy material than in the spice. The spice may contain at least one of Fe and As, and the concentration of at least one of Fe and As contained in the spice may be higher in the light material than in the spice. A gravity separator may be used in the separating step. The crushing step may crush the solidified spice to a particle size of 30 mm or less. The lead raw material may contain lead obtained during copper smelting. [Effects of the Invention]

[0008] 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]

[0009] [Figure 1] FIG. 1 illustrates a method for recovering lead. [Figure 2] FIG. 1 is a diagram illustrating a Pb electric furnace. [Figure 3] FIG. 10 is a diagram illustrating an example of an air table. [Figure 4] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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.

[0011] Fig. 1 is a diagram illustrating a lead recovery method according to this embodiment. As illustrated 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 electrical 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 separation process into the metal phase 4 and the slag phase 5, some of the Fe and As are alloyed, resulting in the formation of an intermediate layer, spice 6, 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 and As 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 and As 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 and As. 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 and As.

[0017] Therefore, through extensive research, the inventors have discovered that when spice 6 is crushed after solidification, metal components such as Pb, Sn, Sb, and Bi have relatively high specific gravities, while spice components such as Fe and As have relatively low specific gravities. Therefore, in this embodiment, spice 6 is crushed and then subjected to gravity sorting. It is preferable to crush the spice 6 to a particle size of, for example, 30 mm or less. The crusher used for crushing is not particularly limited, but a hammer crusher, for example, can be used. For example, a screen can be attached to the hammer crusher to crush the spice to the desired particle size. Here, particle size refers to the maximum diameter of each particle.

[0018] A gravity separator is used for gravity separation. For example, a two-axis air table can be used as the gravity separator. FIG. 3 shows an example of an air table 10. The air table 10 is a two-axis air table having, for example, an inclination angle θ1 (>0°) and a separation angle θ2 (>0°). The air table 10 includes a plate-shaped table 11. The table 11 is trapezoidal, with the width of the downstream edge 11b being larger than the width of the upstream edge 11a. The table 11 is provided with a slit-shaped air blowing section 12. Air is blown out from the air blowing section 12 as indicated by arrow 12a, applying buoyancy to the objects to be separated supplied onto the table 11. The table 11 is also configured to be vibrated.

[0019] The table 11 is set to have an inclination angle θ1 (>0°) and a separation angle θ2 (>0°). The inclination angle θ1 is the angle of the side connecting the first end 11a1 of the upstream edge 11a and the first end 11b1 of the downstream edge 11b with respect to the horizontal plane. The separation angle θ2 is the angle of the downstream edge 11b with respect to the horizontal plane. In this embodiment, the separation process is performed with the inclination angle θ1>0° and the separation angle θ2>0°, so that the first end 11b1 of the downstream edge 11b is positioned at the lowest position.

[0020] When materials to be separated are supplied near the upstream edge 11a of the air table 10 as indicated by arrow 13 and the air table 10 is operated, the light materials move as indicated by arrow 14, and the heavy materials move as indicated by arrow 15. This results in gravity separation. In this embodiment, crushed spice 60 is supplied to the air table 10 as materials to be separated as indicated by arrow 13. By operating the air table 10, the materials are separated into metal components such as Pb, Sn, Sb, Bi, and precious metals, and spice components such as Fe and As. Since the spice components such as Fe and As are light, they move as indicated by arrow 14. On the other hand, since the metal components such as Pb, Sn, Sb, and Bi are relatively heavy, they move as indicated by arrow 15. Therefore, the concentration of at least one of Pb, Sn, Sb, and Bi contained in the spice 6 is higher in the heavy materials than in the spice 6. Furthermore, the concentration of at least one of Fe and As contained in the spice 6 is higher in the lighter materials than in the spice 6. In this way, metal components such as Pb, Sn, Sb, and Bi are separated from spice components such as Fe and As.

[0021] 1 again, the separated heavy materials are sent back to the Pb electric furnace 100. The separated light materials are sent to a process other than the Pb electric furnace 100. For example, they are sent back to a flash furnace for copper smelting.

[0022] The metal phase 4 is then subjected to a process for recovering each of the contained metal elements individually. For example, Pb, Sn, Sb, and Bi are recovered individually. For example, Pb can be purified to produce a lead anode, and lead can be recovered by electrolytic refining.

[0023] According to this embodiment, by crushing the spice 6 and performing gravity separation, even if the spice 6 contains metal components, it can be separated into heavy materials containing relatively large amounts of metal components such as Pb, Sn, Sb, and Bi, and light materials containing relatively large amounts of spice components such as Fe and As. This allows the metal components such as Pb, Sn, Sb, and Bi to be sent to the Pb electric furnace 100 instead of being sent to the copper smelting furnace. As a result, the first-pass rate of metal components such as Pb, Sn, Sb, and Bi can be increased. [Example]

[0024] (Example) Spices generated in a Pb electric furnace were recovered. The composition of the recovered spices before gravity separation is shown in Table 1. As shown in Table 1, the spices contained Sn, Sb, Pb, and Bi in addition to Fe and As. The spices were crushed to particle sizes of 30 mm or less.

[0025] The crushed material was then gravity-separated using a two-axis air table to separate it into heavy and light materials. The inclination angle θ1 of the two-axis air table was set to 6.5°, and the separation angle θ2 was set to 2.75°.

[0026] The amounts of components contained in the heavy and light materials were measured. As a result, the amounts of components in Table 1 and the distribution ratios shown in Figure 4 were obtained. As shown in Table 1 and Figure 4, Pb, Sn, Sb, and Bi were found in large amounts in the heavy materials, while Fe and As were found in large amounts in the light materials. These results confirmed that by separating crushed spices into heavy and light materials by gravity separation, it is possible to separate the spices into metal components such as Pb, Sn, Sb, and Bi, and spice components such as Fe and As. [Table 1]

[0027] 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.

[0028] 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]

[0029] 1 Inlet 2 furnace 3 electrodes 4 Metallic Phase 5 Slag phase 6. Spice 7 Slag outlet 8 Metal outlet 10. Airtable 11 tables 11a Upstream edge 11b Downstream edge 11b1 First end 12 Air outlet θ1 1st inclination angle θ2 2nd inclination angle 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 separation step of separating the crushed material obtained in the crushing step into light materials and heavy materials; and repeating the heavy object through the melting step.

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

3. The spice contains at least one of Fe and As, The method for recovering lead according to claim 1, wherein the concentration of at least one of Fe and As contained in the spice is higher in the light material than in the spice.

4. 2. The method for recovering lead according to claim 1, wherein a gravity separator is used in the separation step.

5. 2. The method for recovering lead according to claim 1, wherein in the crushing step, the solidified spice is crushed to a particle size of 30 mm or less.

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

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