JP6959169B2 - Sn removal method and Pb manufacturing method - Google Patents

Description

This case relates to a method for removing Sn and a method for producing Pb.

For example, in lead smelting in which product Pb is produced from lead raw materials such as lead (Pb) slag generated in copper smelting, tin (Sn) scum is generated by performing soda treatment on molten crude Pb metal. .. Sn can be removed by recovering the Sn scum (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2013-234356

However, impurities such as Pb are also mixed in the Sn scum. If the amount of impurities mixed in the Sn scum is large, the repeated amount of the impurities may increase when the leachate residue of the Sn scum is repeated in the lead smelting step, the processing cost may increase, and the yield may deteriorate.

In view of the above problems, it is an object of the present invention to provide a method for removing Sn and a method for producing Pb, which can suppress the amount of impurities mixed in Sn scum.

In one embodiment, the method for removing Sn includes a series of steps including a step of performing soda treatment on molten crude Pb metal and a step of separating Sn scum generated in the soda treatment in a Harris furnace. The Harris furnace includes the Harris treatment step of repeating the above and a recovery step of leaving a part of the purified Pb metal obtained in the Harris treatment step in the Harris furnace and recovering it, and when the next Harris treatment step is started, the Harris furnace is started. It is characterized in that a molten crude Pb metal having a Sn grade of 6.0 mass% or less, which is obtained by mixing the purified Pb metal remaining in the above and the crude Pb metal, is subjected to soda treatment.

In one aspect, the method for producing Pb is characterized in that Pb is produced by performing an electrolysis step on the purified Pb metal recovered in the recovery step of any of the above Sn removing methods.

According to the present invention, the amount of impurities mixed in Sn scum can be suppressed.

It is a figure explaining an example of the process of manufacturing Sn and Pb. (A) and (b) are diagrams illustrating the Harris processing step. It is a figure which illustrates the relationship between the Sn grade in a molten crude Pb metal, and the amount of Pb mixed in Sn scum (Pb / Sn ratio).

Hereinafter, embodiments for carrying out the present invention will be described.

FIG. 1 is a diagram illustrating an example of a manufacturing process for manufacturing product Sn and product Pb. As illustrated in FIG. 1, decopperation and carbonation are performed on lead raw materials such as lead slag and waste batteries generated in a copper smelting process and the like. Lead carbonate obtained by decopperation and carbonation is put into a Pb electric furnace as a Pb raw material. Lead carbonate is separated into crude Pb metal and slag by melting at 1000 ° C. to 1200 ° C. in a Pb electric furnace.

The crude Pb metal contains Sn as an impurity. For example, the Sn grade of the crude Pb metal exceeds 6.0 mass% and may be 8.0 mass% or more. Since Sn can be effectively removed in the steps described below, it is particularly effective when the Sn quality of the crude Pb metal exceeds 10.0 mass%.

The cooled crude Pb metal is charged into the Harris furnace. In the Harris furnace, soda treatment is performed on the molten crude Pb metal obtained by melting the crude Pb metal. In the soda treatment, for example, caustic soda is added to the molten crude Pb metal melted by heating to about 500 ° C., and in some cases, additional caustic soda and sodium nitrate are added to make Sn a soda salt (Na ₂ SnO ₃ ). It is a process of solidifying on the surface of the molten metal. The solidified Sn soda salt is generally called Sn scum. The Sn scum can be removed by scooping and separating the Sn scum. In order to sufficiently lower the Sn quality in the molten crude Pb metal, a series of steps including a soda treatment step and a Sn scum separation step are repeated one or more times. A step of repeating the series of steps one or more is called a Harris treatment step.

Sn scum is used as a Sn raw material for Sn production. Specifically, the Sn scum is subjected to a Sn leaching step of leaching Sn. The obtained post-leaching liquid is subjected to an electrowinning step to produce a product Sn. The leaching residue of the Sn leaching step is repeated in the lead electric furnace or carbonation step. On the other hand, the Harris treatment step provides a purified Pb metal having a low Sn grade. This purified Pb metal is subjected to an electrolytic refining step to produce a product Pb.

FIG. 2A is a diagram illustrating the Harris processing step. As illustrated in FIG. 2A, cooled crude Pb metal is charged into the Harris furnace 10. By heating this crude Pb metal in the Harris furnace 10, the molten crude Pb metal 20 is obtained. The black circles represent the Sn components contained. By performing soda treatment on the molten crude Pb metal 20, Sn scum 30 is generated on the surface of the molten metal. The Sn scum 30 can be removed by scooping and separating the Sn scum 30. Further, by performing soda treatment on the molten crude Pb metal 20, Sn scum 30 is generated on the surface of the molten metal. The Sn scum 30 can be further removed by scooping and separating the Sn scum 30. In the Harris treatment step, the step of performing the soda treatment and the step of separating the Sn scum 30 are repeated until the Sn concentration in the molten crude Pb metal 20 becomes sufficiently low. When the Sn concentration in the molten crude Pb metal 20 becomes sufficiently low, the purified Pb metal 40 can be recovered from the Harris furnace 10 by sucking the molten crude Pb metal 20 with a metal pump.

Here, when the Sn scum is formed by the soda treatment, impurities such as Pb and Bi (bismuth) are also involved in the Sn scum and are mixed in the Sn scum. As illustrated in FIG. 1, the mixed impurities are recovered as a leachate residue in the Sn leaching step and repeated in the lead smelting step. If the amount of impurities repeated in the lead smelting process increases, the processing cost may increase and the yield may deteriorate. Therefore, it is desired to suppress the amount of impurities mixed in the Sn scum.

FIG. 3 is a diagram illustrating the relationship between the Sn grade in the molten crude Pb metal and the amount of Pb mixed in the Sn scum (Pb / Sn ratio). As illustrated in FIG. 3, it was found by the diligent studies of the present inventors that the higher the Sn grade in the molten crude Pb metal, the larger the amount of Pb mixed in the Sn scum. For Bi, the same result as in FIG. 3 can be obtained.

Therefore, in the present embodiment, when the purified Pb metal 40 is recovered from the Harris furnace 10, a part of the purified Pb metal 40 is left in the Harris furnace 10. Even if all the purified Pb metal 40 is to be recovered by the metal pump, some of the refined Pb metal 40 may remain in the Harris furnace 10. Therefore, "leaving a part" here means intentionally leaving a part of the purified Pb metal 40 that can be recovered by the metal pump. For example, 1/10 to 1/2 of the purified Pb metal 40 in the Harris furnace 10 may be left.

In this case, as illustrated in FIG. 2B, when the cooled crude Pb metal is charged into the Harris furnace 10, the purified Pb metal 40 remains in the Harris furnace 10. Since the Sn concentration of the purified Pb metal 40 remaining in the Harris furnace 10 is sufficiently low, the Sn concentration in the molten crude Pb metal 20 at the time of performing the soda treatment is low. Therefore, it is possible to suppress the amount of impurities mixed in the Sn scum generated during the soda treatment.

From the results of FIG. 3, in order to suppress the Pb / Sn ratio in the Sn scum to less than 1.5, the purified Pb metal 40 remaining in the Harris furnace 10 and the crude Pb metal newly put into the Harris furnace 10 It is preferable to adjust the Sn quality of the molten crude Pb metal 20 (the molten crude Pb metal at the start of the Harris treatment) obtained by mixing the above to 6.0 mass% or less. From the viewpoint of sufficiently suppressing the amount of Pb mixed in the Sn scum, the Sn quality of the molten crude Pb metal 20 at the start of the Harris treatment is preferably 4.0 mass% or less, preferably 2.0 mass% or less. Is more preferable.

The Sn grade C3 in the molten crude Pb metal 20 at the start of the Harris treatment can be represented by the following formula (1).
C3 = (C1 x W1 + C2 x W2) / (W1 + W2) (1)
C1: Sn grade in purified Pb metal 40 (constant at 1 mass% or less)
C2: Sn grade in coarse Pb metal (about 5 mass% to 20 mass%)
C3: Sn grade in molten crude Pb metal 20 at the start of Harris treatment W1: Weight of refined Pb metal 40 left in Harris furnace 10 W2: Weight of crude Pb metal

By adjusting the weight W1 of the refined Pb metal 40 left in the Harris furnace 10 according to the Sn grade C2 in the crude Pb metal, the Sn grade in the molten crude Pb metal 20 at the start of the Harris treatment is reduced to 6 mass% or less. Can be adjusted. When the Sn grade in the crude Pb metal is high, the purified Pb metal 40 is diluted by leaving a large amount in the Harris furnace 10. When the Sn grade in the crude Pb metal is low, the amount of the purified Pb metal 40 left in the Harris furnace 10 can be reduced. In this case, the amount of purified Pb metal 40 that can be recovered from the Harris furnace 10 by the metal pump increases, the process can be simplified, and the cost can be suppressed.

For example, when the Sn grade C2 in the crude Pb metal is 18 mass%, if the weight W1 of the refined Pb metal 40 left in the Harris furnace 10 is 6 tons or more and the weight W2 of the crude Pb metal is 3 tons or less, Harris The Sn grade C3 in the molten crude Pb metal 20 at the start of the treatment can be set to 6 mass% or less. For example, when the Sn grade C2 in the crude Pb metal is 12 mass%, the weight W1 of the refined Pb metal 40 left in the Harris furnace 10 is 4.5 tons or more, and the weight W2 of the crude Pb metal is 4.5 tons or less. Then, the Sn grade C3 in the molten crude Pb metal 20 at the start of the Harris treatment can be set to 6 mass% or less.

(Example)
The Harris treatment step was performed according to the embodiment. When the purified Pb metal 40 was recovered from the Harris furnace 10, a part of the purified Pb metal 40 was left in the Harris furnace 10. The crude Pb metal was charged into the Harris furnace 10 in which the refined Pb metal 40 remained. The Sn grade in the molten crude Pb metal 20 at the start of the Harris treatment was 5.1 mass%. Sn scum was generated by the Harris treatment process and scooped up. Table 1 shows the grades of each component of the scooped Sn scum.

(Comparison example)
In the comparative example, when the purified Pb metal 40 was recovered from the Harris furnace 10, all the purified Pb metal 40 that could be recovered by the recovery capacity of the metal pump was recovered. Then, the crude Pb metal was put into the Harris furnace 10. The Sn grade in the molten crude Pb metal 20 at the start of the Harris treatment was 8.9 mass%. Sn scum was generated by the Harris treatment process and scooped up. Table 2 shows the grades of each component of the scooped Sn scum.

By leaving a part of the purified Pb metal 40 remaining, the Sn grade in the molten crude Pb metal 20 at the start of the Harris treatment could be lowered. From the results in Tables 1 and 2, it was found that by lowering the Sn grade in the molten crude Pb metal 20 at the start of the Harris treatment, the amount of impurities mixed into the Sn scum can be suppressed. Further, it was found that the amount of impurities mixed in the Sn scum can be sufficiently suppressed by setting the Sn grade in the molten crude Pb metal 20 at the start of the Harris treatment to 6 mass% or less.

Although the examples of the present invention have been described in detail above, the present invention is not limited to the specific examples, and various modifications and modifications are made within the scope of the gist of the present invention described in the claims. It can be changed.

10 Harris furnace 20 molten crude Pb metal 30 Sn scum 40 refined Pb metal

Claims (4)

In the Harris furnace, a Harris treatment step in which a series of steps including a step of performing soda treatment on molten crude Pb metal and a step of separating Sn scum generated in the soda treatment is repeated one or more.
Including a recovery step of leaving a part of the purified Pb metal obtained in the Harris treatment step in the Harris furnace and recovering it.
When the next Harris treatment step is started, the purified Pb metal remaining in the Harris furnace and the crude Pb metal are mixed and obtained , and the molten crude Pb metal having a Sn grade of 6.0 mass% or less is subjected to soda treatment. A method for removing Sn, which comprises performing. The method for removing Sn according to claim 1, wherein the Sn grade is adjusted to 6.0 mass% or less by mixing the crude Pb metal with the purified Pb metal remaining in the Harris furnace. The method for removing Sn according to claim 2, wherein the Sn grade of the crude Pb metal is 8.0 mass% or more. A method for producing Pb, which comprises producing Pb by performing an electrolysis step on the purified Pb metal recovered in the recovery step of the method for removing Sn according to any one of claims 1 to 3. ..

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