JPH022936B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a metal purification device,
Specifically, the present invention relates to an apparatus for obtaining purified metal from impure molten metal by a fractional crystallization method.

Several methods have been proposed for producing high-purity aluminum using the fractional crystallization method (Japanese Patent Publication No. 1973-
5806, 50-20536, JP-A-55-89439, 56-55530
and 56-112429). In these methods, impurity elements having a distribution coefficient of less than 1, such as iron and silicon, are excluded from the crystallized aluminum crystals and remain in the mother liquor. Therefore, by separating the crystallized aluminum and the mother liquor by an appropriate method, highly pure aluminum can be obtained. The present inventors also first stored molten aluminum in a container equipped with a bed having a cooling medium flow pipe inside, cooled the bed while stirring, and crystallized aluminum on the bed. proposed a method for obtaining aluminum (patent application 1982-
(see 201181).

In this method, the bed is made of a carbonaceous material, usually a fired carbon block similar to the cathode part of an aluminum electrolyzer, especially a quasi-graphitic or graphitic carbon block, so as not to contaminate the molten aluminum and to conduct heat well. be done. Then, in the same way as installing a collector bar in the cathode section of an electrolytic cell, a groove is bored in the carbon block, and a metal tube for circulating the cooling medium is buried in the groove.

In this method, it is necessary to have good heat conduction between the carbon block and the metal tube. This is accomplished by bringing the carbon block and metal tube into close contact. However, since the metal tube has a higher coefficient of thermal expansion than the carbon block, if the two are kept in close contact with each other, there is a risk that pressure will be applied to the carbon block due to the thermal expansion of the metal tube during the crystallization operation, causing cracks in the carbon block. be. In addition, in this method, the metal tube is repeatedly heated and cooled for each crystallization operation, which causes deformation of the metal tube, which creates uneven pressure on the carbon block and risks causing cracks. .

The present invention provides a metal purification apparatus having a floor structure that does not generate large pressure on the carbon block even if the carbon block and the metal tube are brought into close contact with each other.

The apparatus according to the present invention comprises a container made of a carbonaceous material and provided with a bed having a cooling medium flow pipe therein, and a stirrer suspended in the container. A device for precipitating metal purified from a metal on the bed, wherein the flow pipe has a continuous cutout along the pipe axis, and the cutout is perpendicular to the pipe axis. The cooling pipe is characterized by being sealed with an expansion absorbing material whose width can be contracted as the circumferential length of the cooling pipe increases in a plane.

To explain the present invention based on the drawings, FIG. 1 is a plan view of the lower part of an example of the apparatus according to the present invention, in which carbon blocks mainly constituting the floor surface,
This is to schematically show the relationship with the cooling medium distribution pipe buried therein. Figures 2 and 3 are A-A' and B of Figure 1, respectively.
FIG. This device consists of a lower structure that is shaped like a rectangular shallow pot and has a discharge inlet for molten metal formed on its side wall, an upper structure that covers the upper structure, and a stirrer that is suspended from this upper structure. . In the figure, 1 is a heat insulating brick layer and 2 is a fireproof brick layer. For the side wall portion of the refractory brick layer that comes into contact with molten aluminum, a material that does not contaminate molten aluminum, such as a high alumina refractory brick, is used. If desired, the sidewall portions in contact with the molten aluminum, as well as the bottom surface, may be further lined with carbonaceous material over the refractory brick layer. In this case, in order to avoid crystallization of aluminum onto the lining layer, the structure is such that heat does not flow through the lining layer to the carbonaceous material layer on the bottom surface. 3 is a layer of carbonaceous material constituting the surface layer of the bed. Usually, this layer is constructed by arranging carbon blocks 4 and filling the gaps with a carbonaceous binder, similar to the cathode of an aluminum electrolytic cell.
The carbon block is preferably graphite or quasi-graphite, which has a high thermal conductivity. If desired, a carbonaceous material may be added to the upper surface of the carbon block 4.
For example, the carbonaceous binder described above may be coated to prevent the carbon block from being worn away by the flow of molten metal. Reference numeral 5 denotes a cooling medium flow pipe buried in the carbonaceous material layer 3. When crystallizing the metal, the heat of the molten metal is transferred to the cooling medium in the cooling medium flow pipe through the carbonaceous material layer 3. Therefore, it is preferable that the carbonaceous material has high thermal conductivity, and it is preferable that the flow direction of the cooling medium be reversed in adjacent pipes so that the bed is uniformly cooled. It is preferable that the shape of the carbonaceous material layer 3 is a rectangle or a similar shape, for example, a shape with rounded corners, and a plurality of stirrers 8 are arranged on the center line of its long axis (Japanese Patent Application No. 1983-1999)
(See 138251 ``Method for Purifying Aluminum''). The portion of the stirrer 8 that comes into contact with the molten aluminum is also made of a material that does not contaminate the molten aluminum, preferably graphite. In addition, the stirrer is attached to a drive device (not shown) provided in the upper structure, and the stirrer responds to the rise of the crystallized metal surface during driving so that the distance to the crystallized metal surface is always within a certain range. and gradually raise it. Further, when the crystallization operation is completed, the stirrer is taken out of the container to prevent damage to the stirrer due to heating during re-dissolving the crystallized metal. Therefore, the stirrer is installed so that it can be raised and lowered in this manner.

6 and 7 are molten metal outlets provided in the longitudinal side walls. 9 is an inlet for molten metal provided on the short side wall. 10 is a burner, which burns fuel oil or fuel gas to heat the surface of the molten metal during the crystallization operation to prevent metal from crystallizing anywhere other than the bottom surface, and after the crystallization is completed, the remaining mother liquor is discharged. This is for later heating and remelting the crystallized metal.

FIG. 4 is an enlarged view of the carbon block and coolant flow pipe shown in FIG. 2. A continuous notch 11 is formed in the flow pipe 5 along the pipe axis, and the notch 11 absorbs an increase in the circumferential length of the cooling pipe in a plane perpendicular to the pipe axis. It is sealed by an expandable absorbent material 12 that can be used. The expansion absorbing material 12 is made of a corrugated plate having concavities and convexities continuous in the direction of the tube axis, and both ends thereof have cutout portions 1.
It is welded to the left and right tube walls 13 and 14 of 1. Therefore, when the flow tube 5 is heated to a high temperature by heat transfer from the carbon block 4 during the crystallization operation, the flow tube 5 thermally expands in a plane perpendicular to the tube axis, and its circumference increases. A part of the pressure of this expansion is absorbed by the carbon block 4, and the rest is absorbed by the reduction in the distance between the notches 11. At this time, the expansion absorbing material made of the corrugated plate easily follows the reduction in the interval between the notches 11 and reduces its width. Note that the expansion absorbing material may have other shapes as long as it can easily follow changes in the interval between the notches 11. For example, FIG. 5 shows one example in which an expansion absorbing material made of a plate having a continuous bulge in the tube axis direction is welded to the cooling tube. In addition, FIG. 6 shows an expansion absorbing material made of a flat plate with significantly lower strength than the cooling pipe, which easily deforms when the pressure of thermal expansion is applied to absorb the reduction in the spacing between the notches 11. Can be done.

Next, an example of a method for purifying aluminum using the illustrated apparatus will be described. First, molten aluminum is introduced into the apparatus through the inlet 9, and a stirrer 8 is inserted into the apparatus for stirring. Next, air or other cooling medium is passed through the cooling medium distribution pipe 5 to cool the bed 3, and aluminum 15 is crystallized on the bed surface. The flow rate of the cooling medium is preferably selected such that the crystallization rate of aluminum, that is, the rate of rise of the aluminum crystallization surface is 10 to 150 mm/hour. Further, the rotational speed of the stirrer 8 is preferably 1 to 10 m/sec as the tip speed of the stirring blade.

During the crystallization operation, the molten aluminum surface is heated by burner 10 to compensate for heat loss from the surface and sidewalls and to prevent aluminum from crystallizing anywhere other than the bottom surface. Heating may be continuous or intermittent, but is such that the molten aluminum is maintained at a temperature slightly above its melting point, typically around 662°C. Further, as the aluminum crystallizes, the stirrer 8 is pulled up continuously or intermittently so that the distance between the crystallization surface and the lower end of the stirring blade is always approximately constant. Typically, this distance is preferably between 10 and 100 mm.
The crystallization plane can be detected directly or indirectly estimated from the amount of cooling heat.

When a predetermined amount of aluminum, usually 30 to 70%, preferably 40 to 50%, of the charged aluminum has crystallized, the crystallization is stopped, and the apparatus is tilted to allow the remaining molten aluminum to flow out from the outlet 6. let Although it is not impossible to supply and discharge molten aluminum to and from the apparatus during the crystallization operation, it is not a preferred method because temperature control is difficult. Note that, prior to discharging the molten aluminum, it is advantageous to pull the stirrer 8 out of the apparatus and to rapidly heat the molten aluminum with the burner 10 to reduce its viscosity. Normally, the molten aluminum is heated to 665-667°C to flow out, but if it is possible to heat rapidly to avoid excessive melting of the crystallized aluminum, heating to higher temperatures is possible. good. Once the remaining molten aluminum has been discharged, the apparatus is returned to the horizontal position, the crystallized aluminum is heated and melted with a burner, and the apparatus is tilted in the opposite direction to flow out the purified molten aluminum from the discharge port 7, and the predetermined amount is It is made into a product by casting into the shape of.

According to the present invention, even if the carbon block and the coolant flow pipe are brought into close contact with each other, excessive pressure is not applied to the carbon block during the crystallization operation. Therefore, it is possible to bring the two into close contact with each other and maintain good heat conduction between the two.

[Brief explanation of drawings]

FIG. 1 is a plan view of the lower portion of an apparatus according to an embodiment of the present invention, and arrows in the figure indicate the direction of flow of the cooling medium. Figure 2 shows the A-
It is a longitudinal cross-sectional view along A'. FIG. 3 is a longitudinal cross-sectional view of the device of FIG. 1 taken along line BB'. In addition, the second
In the figures and FIG. 3, the support mechanism for the stirrer is omitted. FIG. 4 is an enlarged view of the carbon block and coolant flow pipe shown in FIG. 2. FIGS. 5 and 6 are examples of coolant flow pipes using an expansion absorbing material having a shape different from that of FIG. 4. FIG. 1...Insulating brick layer, 2...Fireproof brick layer, 3
...Carbonaceous material layer, 4...Carbon block, 5...
Cooling medium distribution pipe, 6, 7... Molten metal discharge port, 8
... Stirrer, 9 ... Molten metal inlet, 10 ... Burner, 11 ... Notch, 12 ... Expansion absorber, 13 ... Left side of notch, 14 ... Right side of notch Part 15...Crystallized metal layer.

Claims (1)

[Claims] 1. From impure molten metal, comprising a container made of carbonaceous material and provided with a bed having a cooling medium flow pipe inside the container, and a stirrer suspended within the container. The apparatus is for depositing purified metal on the bed, and the flow pipe has a continuous cutout along the pipe axis, and the cutout is perpendicular to the pipe axis. A device characterized in that the cooling pipe is sealed with an expansion absorbing material whose width can be contracted in accordance with an increase in the circumferential length of the cooling pipe in a plane. 2. The device according to claim 1, characterized in that the bed is composed of carbon blocks. 3. The device according to claim 1 or 2, wherein the expansion absorbing material is a corrugated plate having concavities and convexities continuous in the tube axis direction. 4. The device according to claim 1 or 2, wherein the expansion absorbing material is a plate having a continuous bulge in the tube axis direction.