JP2023018761A - Continuous refining system and continuous refining method of high purity metal - Google Patents

Abstract

To provide a continuous refining system capable of refining high purity metal without a large installation area.SOLUTION: A refining system is equipped with a melting furnace 1 for melting metal, a plurality of molten metal holding tanks 3 connected in series to which molten metal is sent in order from the melting furnace, and cooling units 4 each paired with each of molten metal holding tanks 3 for crystallizing high purity metal in the molten metal. A lump of the high purity metal deposited, coagulated, and recovered at the cooling units 4 of one or more of downstream molten metal holding tanks 3 among the plurality of molten metal holding tanks 3 is sent back to the melting furnace 1 for remelting.SELECTED DRAWING: Figure 1

Description

The present invention relates to a continuous refining system for high-purity metals using segregation solidification.

Conventionally, among the methods for producing high-purity metals with few impurity elements, a method that utilizes the segregation phenomenon during solidification (segregation method) has been widely industrially used due to its cost advantage over other refining methods.

In such a segregation method, as a system for efficiently refining high-purity aluminum, a plurality of serially connected molten metal holding tanks into which the molten metal from the aluminum melting furnace is sequentially fed, and each molten metal holding tank is paired. A series of equipment equipped with a rotating cooling body is set as one line, and a plurality of sets of this line are provided, and the high-purity aluminum mass adhered and solidified on the rotating cooling body and collected in the (n-1)th line is transferred to the following nth order. A system has been proposed that repeats refining by melting in a melting furnace on the line (Patent Document 1 below).

JP 2009-24234 A

Increasing the number of lines in this way is effective in increasing the purity, but it requires a corresponding amount of facility space, and there are cases where it cannot be used due to increased facility installation costs and site space.

The present invention has been made in view of such circumstances, and provides a continuous high-purity metal refining system capable of refining high-purity metals without increasing the number of lines (although it is not denied that the number of lines will be increased). intended to

The present invention provides the following means.

[1] A melting furnace for melting metal, a plurality of molten metal holding tanks connected in series to which the molten metal from the melting furnace is sequentially fed, and each molten metal holding tank paired with each other, in the molten metal a cooling body for crystallizing the high-purity metal,
A high-purity metal ingot that has been adhered and solidified by a cooling body of one or more molten metal holding tanks downstream of the plurality of molten metal holding tanks and collected is returned to the melting furnace and remelted. Continuous refining system for high-purity metals.

[2] The high-purity metal continuous refining system according to the above item 1, wherein the metal is aluminum or an aluminum alloy.

[3] Continuous production of high-purity metal according to the above item 1 or 2, wherein the number of molten metal holding tanks for returning the collected high-purity metal ingots to the melting furnace for remelting is 1/2 or less of the total number of molten metal holding tanks. purification system.

[4] A melting furnace for melting metal, a plurality of molten metal holding tanks connected in series to which the molten metal from the melting furnace is sequentially fed, and each molten metal holding tank paired with A continuous refining method for high-purity metals using a continuous refining system comprising a cooling body for crystallizing high-purity metals,
A step of returning the high-purity metal ingots adhered and solidified by the cooling body of one or more molten metal holding tanks downstream of the plurality of molten metal holding tanks to the melting furnace for remelting is repeated multiple times. A method for continuously refining a high-purity metal characterized by:

[5] The method for continuous refining of high-purity metals as described in [4] above, wherein the temperature of the high-purity metal ingot is 300° C. or higher when it is returned to the melting furnace and re-melted.

According to the invention of the preceding item [1], the high-purity metal ingot refined in the downstream molten metal holding tank has a lower purity than the upstream molten metal holding tank, but the purity is higher than that of the raw material put into the melting furnace. Therefore, by returning it to the melting furnace and remelting it, the purity of the molten metal supplied from the melting furnace to the molten metal holding tank can be increased. A refined mass can be obtained.

According to the invention of the preceding item [2], highly pure aluminum can be obtained.

According to the invention of the preceding item [3], the amount of high-purity metal ingots to be returned to the melting furnace and re-melted is less than half of the latter half of the entire molten metal holding tank, thereby suppressing a decrease in the weight of the product recovered. , impurities can be reduced.

According to the invention of the preceding item [4], the step of returning the high-purity metal ingot to the melting furnace and remelting it is repeated a plurality of times, thereby further increasing the purity of the molten metal supplied from the melting furnace to the molten metal holding tank. It is possible to obtain a purified lump of higher purity.

According to the invention of the preceding item [5], compared to the case where the high-purity metal ingot is cooled to less than 300° C. and then returned to the melting furnace, the ingot melting time can be shortened and excellent energy efficiency can be obtained.

1 is a diagram showing the configuration of a continuous refining system for high-purity metals according to one embodiment of the present invention; FIG. 2 is a diagram showing in detail the configuration of part of the system of FIG. 1; FIG. FIG. 4 is a diagram showing details of a molten metal holding tank; FIG. 4 is a diagram showing the configuration of a high-purity metal continuous refining system according to another embodiment of the present invention;

FIG. 1 is a diagram showing the configuration of a high-purity metal continuous refining system according to one embodiment of the present invention.

This system comprises a melting furnace 1 for melting metal, a plurality of (10 in this example) molten metal holding tanks 3 connected in series to which the molten metal from the melting furnace 1 is fed in order, and each molten metal A rotating cooling body 4 for forming a pair with a holding tank 3 and crystallizing a high-purity metal in the molten metal is provided.

FIG. 2 is a diagram showing in detail the configuration of part of this system.

The melting furnace 1 melts raw metal containing impurities. The molten metal 5 melted in the melting furnace 1 is delivered to each molten metal holding tank 3 through the gutter 2 . A rotating cooling body 4 is installed in each molten metal holding tank 3 .

FIG. 3 is a diagram showing the details of the molten metal holding tank.

The molten metal holding tank 3 has, for example, a bottomed cylindrical shape with an inner diameter D and a height H, and the bottom surface is formed in a downward arc shape.

The rotary cooling body 4 is formed, for example, in the shape of a truncated cone with a large diameter on the upper end side, and is arranged at a predetermined position in the molten metal holding tank 3 having an outer diameter d at the upper surface of the molten metal and a height h from the upper surface of the molten metal to the lower end of the cooling body. be. The rotating cooling body 4 is internally cooled by a cooling body such as air or steam and rotates in the molten metal.

When the temperature of the molten metal in the molten metal holding tank 3 is kept above the freezing point, the high-purity metal to be refined is crystallized on the surface of the rotating cooling body 4 according to the principle of segregation solidification, and a high-purity metal lump is formed. It is formed.

The molten metal having a high impurity concentration in the molten metal holding tank 3 is sent to the next molten metal holding tank 3 positioned downstream in sequence.

The metal lumps crystallized and extracted on the surface of the rotating cooling body 4 are pulled up while rotating the rotating cooling body 4, and after the rotation is stopped outside the molten metal holding tank 3, they are recovered by a recovering device (not shown), for example mechanically. to be recovered.

When recovering the metal ingots crystallized and purified in the rotary cooling bodies 4 immersed in the respective molten metal holding tanks 3, they may be recovered all at once, but in consideration of continuous production, it is desirable to recover sequentially.

The molten metal in each of the molten metal holding tanks 3 . . . has an impurity concentration that sequentially increases from upstream to downstream.

Residual molten metal not collected in the plurality of molten metal holding tanks 3 arranged in series is drained out of the system by a drain device 6 .

Regarding the purity of the high-purity metal ingots recovered from the rotary cooling bodies 4 of the respective molten metal holding tanks 3, those recovered from the uppermost molten metal holding tank 3 having the highest purity of the molten metal are the highest in purity, and the purity is the highest in the upstream side. The purity decreases sequentially from the downstream side.

In the high-purity metal continuous refining system shown in FIG. 1, while high-purity metal ingots recovered from the five upstream molten metal holding tanks 3 are taken out as products, they are recovered from the five downstream molten metal holding tanks 3. The high-purity metal ingot is returned to the melting furnace 1 and melted again.

The high-purity metal ingots recovered from the molten metal holding tank 3 on the downstream side have a lower purity than the high-purity metal ingots recovered from the molten metal holding tank 3 on the upstream side, but are more pure than the raw materials put into the melting furnace 1. High purity.

Therefore, by returning it to the melting furnace 1 and remelting it, the purity of the molten metal in the melting furnace 1 becomes higher than that of the raw material, and the purity of the molten metal supplied from the melting furnace 1 to the molten metal holding tanks 3 is increased. can be obtained, a highly purified mass can be obtained.

In particular, by repeating the process of returning the high-purity metal ingot recovered from the molten metal holding tank on the downstream side to the melting furnace 1, the purity of the molten metal in the melting furnace 1 is further increased, and the high-purity metal ingot obtained as a product is increased. High purity can be obtained.

Increasing the number of lines is effective in increasing the purity, but the facility area is required for that amount. A metal ingot with a higher purity can be obtained instead of increasing the .

In the above explanation, five molten metal holding tanks 3 from which high-purity metal ingots are taken out as products are assumed upstream, and five molten metal holding tanks 3 for returning high-purity metal ingots to the melting furnace 1 are assumed downstream. One or a plurality of molten metal holding tanks 3 from which ingots are taken out as products may be provided on the upstream side, and one or a plurality of molten metal holding tanks 3 for returning high-purity metal ingots to the melting furnace 1 may be provided on the remaining downstream side.

By reducing the number of molten metal holding tanks 3 taken out as a product and increasing the number of molten metal holding tanks 3 returned to the melting furnace, the purity of the molten metal in the melting furnace 1 can be further increased, so that metal ingots of higher purity can be obtained. Since the amount of metal ingots obtained as a product is reduced, the production efficiency is lowered.

On the other hand, if the number of molten metal holding tanks 3 returned to the melting furnace 1 is reduced, the amount of metal ingots obtained as products increases and the production efficiency increases, but the purity of the metal ingots obtained as products decreases.

The number of molten metal holding tanks 3 returned to the melting furnace 1 may be appropriately set in consideration of the required purity of the metal ingot and the production efficiency (production volume). , preferably less than or equal to 1/2 of the total number of molten metal holding tanks. By making it 1/2 or less, it is possible to suppress a decrease in the recovered weight of the product and reduce impurities.

When the high-purity metal ingot recovered from the molten metal holding tank 3 on the downstream side is returned to the melting furnace 1 and melted again, the temperature must be 300° C. or higher before the recovered high-purity metal ingot cools down. It is preferable to return to the melting furnace 1 in the meantime.

If the high-purity metal ingot is cooled, the time and energy required for remelting will increase. Excellent energy efficiency is obtained.

Next, another embodiment of the present invention applied to a continuous refining system having multiple lines will be described.

FIG. 4 is a diagram showing the configuration of a high-purity metal continuous refining system according to another embodiment of the present invention.

This refining system comprises a primary line having ten molten metal holding tanks 13 and a secondary line having five molten metal holding tanks 23 .

In the primary line, the molten metal melted in the melting furnace 11 is sequentially sent to the molten metal holding tanks 13 connected in series via the gutter 12 .

Each molten metal holding tank 13 . Residual molten metal that has not been drained is discharged out of the system by a drain device 16 .

In this embodiment, the high-purity metal ingots recovered from the two downstream molten metal holding tanks 13, 13 are returned to the melting furnace 11 and remelted, while the eight upstream molten metal holding tanks 13, . . . The collected high-purity metal ingots are sent to the melting furnace 21 of the secondary line.

The structure of the secondary line is similar to that of the primary line, and the molten metal melted in the melting furnace 21 is sequentially sent to the molten metal holding tanks 23 connected in series through the gutter 22, and the molten metal holding tanks 23 . is provided with a pair of rotating cooling bodies 24, and high-purity metal ingots are recovered from each of the molten metal holding tanks 23 and provided as products.

The residual molten metal not collected in the plurality of molten metal holding tanks 23 on the secondary line may be discharged outside the system by a drain device, but preferably returned to the melting furnace 11 on the primary line by the molten metal recovery device 27. .

All of the starting materials for the secondary line are high-purity metal lumps crystallized in the molten metal holding furnace 13 of the primary line, and are generally higher in purity than the metal raw material that is the starting material for the primary line. By returning it to the line, the purity of the molten metal in the primary line can be increased, and the amount of metal discharged out of the system can be reduced.

In this embodiment, the high-purity metal ingot recovered from the molten metal holding tank 13 on the downstream side in the primary line is returned to the melting furnace 11, so compared to the case where it is not returned, the high-purity metal ingot recovered in the primary line The purity of metal lumps can be increased.

The high-purity metal ingots recovered from the molten metal holding tanks 13 on the upstream side of the primary line have higher purity than the high-purity metal ingots recovered from the molten metal holding tanks 13 on the downstream side. As a starting material for the line, segregation solidification is performed in the secondary line, and the high-purity metal ingot recovered from the molten metal holding tank 23 is used as a product, so that an extremely high-purity metal ingot can be obtained.

Although the type of metal to be refined by the continuous refining system in the above two embodiments does not matter, for example, aluminum or an aluminum alloy can be mentioned as a suitable metal.

When aluminum is used, the finally produced refined ingot has high aluminum purity, so that it can be used for various processing and applications to exhibit excellent performance and functions.

For example, refined metals may be used for casting to produce castings, or these castings may be rolled and used as various metal plates and metal foils.

Also, this metal foil may be used as an electrode material for an aluminum electrolytic capacitor, for example.

In the above two embodiments, only the raw material metal is put into the melting furnace 1, and the molten metal is sent from the melting furnace 1 through the gutter 2 to the molten metal holding tanks 3 arranged in series. Also in the system to which the present invention is applied, a known method for increasing metal purity may be used in combination.

For example, when aluminum is used as the metal, boron may be added to the melting furnace 1 and peritectic impurities such as Ti, Zr, and V may be reacted with boron.

In addition, a stirring tank to which boron can be added may be installed between the melting furnace 1 and the molten metal holding tank 3 with the rotating cooling body 4 .

Furthermore, it is also effective to configure a separation tank for separating the slag separated on the surface of the molten metal to a system other than the molten metal holding tank between each transfer 3 of the molten metal and each transfer of the molten metal.

Next, in a one-line continuous refining system equipped with 20 molten metal holding tanks connected in series, the high-purity metal ingots recovered from the downstream molten metal holding tanks were returned to the melting furnace and remelted. Example and a comparative example in which the operation of returning to the melting furnace is not performed will be described.

Each molten metal holding tank used was a bottomed cylinder having an inner diameter D of 500 mm and a height H of 800 mm, and the bottom surface was formed in a downward arc shape.

The rotating cooling body was made of graphite and had a truncated cone shape with a large upper end, an outer diameter d at the upper surface of the molten metal of 210 mm, and a height h of the lower end of the cooling body from the upper surface of the molten metal of 150 mm.

Compressed air of 2000 L/min was circulated inside the cooling body 4 as a cooling medium, and the refining treatment was performed for 15 minutes at a rotational speed of 200 rpm.

Other refinement conditions were a cooling air pressure of 0.15 MPa, a melt temperature of 670° C., and a recovery rate of 81%.

In Example 1, the high-purity metal ingots recovered from the 18 upstream molten metal holding tanks are used as products, and the high-purity metal ingots recovered from the two downstream molten metal holding tanks are returned to the melting furnace. The process of recovering the high-purity metal ingots and re-inserting them into the melting furnace was repeated five times.

In Example 2, the metal ingots in the 10 downstream molten metal holding tanks were returned to the melting furnace, and in Example 3, the metal ingots in the 15 downstream molten metal holding tanks were returned to the melting furnace.

The raw material composition is aluminum with Si: 150 to 155 ppm and Fe: 195 to 200 ppm, and the product is obtained from the upstream molten metal holding tank recovered for the fifth time when re-input is repeated five times. Table 1 shows the average composition of the high-purity metal ingots.

Table 1 also shows the average composition of the high-purity metal ingots as products, as Comparative Example 1, in which all the high-purity metal ingots recovered from the molten metal holding tank are used as products and the process of returning to the melting furnace is not performed.

As shown in Table 1, the refined mass average composition of the example was higher than that of the comparative example.

In addition, the higher the purity, the higher the number of pieces returned to the melting furnace.

Since the production amount per unit time is inversely proportional to the number of refined ingots returned to the melting furnace, it decreased in the order of Examples 1, 2 and 3.

INDUSTRIAL APPLICABILITY The present invention can be used for continuous refining of high-purity metals using segregation solidification.

REFERENCE SIGNS LIST 1 melting furnace 2 gutter 3 molten metal holding tank 4 rotary cooling body 5 molten metal 6 drain device

Claims (5)

A melting furnace for melting metal, a plurality of molten metal holding tanks connected in series to which the molten metal from the melting furnace is sequentially fed, and each molten metal holding tank paired with a high-purity metal in the molten metal a cooling body for crystallizing the
A high-purity metal ingot that has been adhered and solidified by a cooling body of one or more molten metal holding tanks downstream of the plurality of molten metal holding tanks and collected is returned to the melting furnace and remelted. Continuous refining system for high-purity metals. 2. The system for continuously refining high-purity metals according to claim 1, wherein said metal is aluminum or an aluminum alloy. 3. The high-purity metal continuous refining system according to claim 1 or 2, wherein the number of molten metal holding tanks for returning the collected high-purity metal ingots to the melting furnace for remelting is 1/2 or less of the total number of the molten metal holding tanks. . A melting furnace for melting metal, a plurality of molten metal holding tanks connected in series to which the molten metal from the melting furnace is sequentially fed, and each molten metal holding tank paired with a high-purity metal in the molten metal A continuous refining method for high-purity metals using a continuous refining system comprising a cooling body for crystallizing out
A step of returning the high-purity metal ingots adhered and solidified by the cooling body of one or more molten metal holding tanks downstream of the plurality of molten metal holding tanks to the melting furnace for remelting is repeated multiple times. A method for continuously refining a high-purity metal characterized by: 5. The method for continuously refining a high-purity metal according to claim 4, wherein the temperature of the high-purity metal ingot is 300[deg.] C. or higher when it is returned to the melting furnace and re-melted.

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