JPS5928538A - Aluminum purification method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention relates to a method for purifying aluminum υ,
Specifically, the present invention relates to a method for obtaining high purity aluminum from impure molten aluminum by a one-fraction crystallization method.

Several methods have been proposed for producing high-purity aluminum by fractional crystallization. (Special public showμ?-jrOt,
, jθ-20ri36. Tokukai Shoj! -r95t39. j4
-6j630 and jt-//2t, 29). In these methods, impurities with small distribution coefficients such as iron and silica 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 obtained high-purity aluminum by storing molten aluminum in a container with a horizontal bed, cooling the bed while stirring it, and causing aluminum gold to crystallize on the bed. I proposed a method (Tokugansho!≦−ko0／／／／／
This method is an excellent industrial method, but when using a large container with a large floor area, special care must be taken to ensure uniform flow of molten aluminum in each part of the bed. De Usu. This is because if the floor area is large, it is almost impossible to stir the entire area with seven stirrers, so multiple stirrers will be used.
This is because the flows caused by each stirrer influence each other, and the flow of molten aluminum tends to become non-uniform in each part on the floor surface. If the flow is non-uniform, impurities will not be sufficiently released from the crystallized aluminum in areas where the flow rate is low, resulting in a decrease in the purity of the crystallized aluminum.

The present invention proposes a method that can obtain high-purity aluminum even when using a large container by stirring the molten aluminum using a rotary stirrer so that the flow is uniform. .

According to the invention, a horizontal floor of a rectangular or similar shape with a ratio of the length of the long axis to the right axis of 2 or more, The molten aluminum is placed in a container equipped with two or more stirrers, and all the stirrers are rotated in the same direction to stir the molten aluminum while cooling the bed to deposit high-purity aluminum on the bed surface. By crystallizing and then separating from the molten aluminum all the aluminum residues crystallized on the bed, high purity fart aluminum can be obtained.

To explain the present invention in more detail, in the present invention, Vi.

The agitators were arranged in seven rows so that the agitators would not interact with each other and cause stagnation of fluid on the bed.

and all stirrers rotate in the same direction.

In addition, the shape of the bed is rectangular or ice-like, similar to a box L, so that seven rows of stirrers can generate sufficient fluidity over the entire bed.

The present invention will be explained based on the drawings. Fig. 1 is a plan view of the lower part of seven examples of an apparatus suitable for carrying out the method of the present invention, in which carbon blocks mainly forming the floor surface,
This is to schematically show the connection with the cooling medium distribution pipe buried inside. Figures 2 and 3 are
2A and 2B are vertical cross-sectional views taken along lines A-A' and B-B, respectively, of the device shown in FIG. 1. In the figure, (1) is the insulation brick layer.

(2) is a firebrick 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 side wall portions that come into contact with molten aluminum may also be lined with a carbonaceous material on top of the refractory brick layer, similar to the bottom surface. In this case, the structure should be such that it does not allow access. (3) is a layer of carbonaceous material that constitutes the surface layer of the bed.

Usually, this layer is constructed by lining up carbon blocks (4) ft and filling the gaps with a carbonaceous binder, similar to the cathode of an aluminum electrolytic cell. Carbonaceous block (4
) is preferably graphite or quasi-graphite, which has a high thermal conductivity. In addition, if desired, carbon block (4)
It is also possible to further coat the upper surface of the carbonaceous material 1, such as the carbonaceous binder described above, to prevent the carbon block from being worn away by the flow of aluminum. (5) is a cooling medium flow pipe buried in the carbonaceous material layer (3).

When crystallizing aluminum, the heat of molten aluminum is transferred to the cooling medium in the cooling medium flow pipe through the carbonaceous material layer (3). Therefore, the carbonaceous material preferably has a 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. Carbonaceous material layer (311Ii,
The shape is a rectangle or a shape similar to a rectangle with a length ratio of the long axis to the short axis of 2 or more, for example, a shape with rounded corners.

The length of the short axis is determined from the length that allows uniform stirring with seven stirrers. On the other hand, the length of the long axis is determined from the required surface area of the carbonaceous material layer (3), that is, the desired capacity of the seven devices. Typically, the ratio of the lengths of the major axis to the minor axis is 3:/-22/.

(6) and (7) are outlets for molten aluminum provided in the longitudinal side walls. (8) is an agitator in which 1.2 or more units, usually 3 to IO units, are arranged in 7 rows in the center along the long axis of the floor. The portion of this stirrer that comes into contact with the molten aluminum is also made of a material that contaminates the molten aluminum, preferably graphite. The length of the stirrer blade is θ of the short axis of the bed. It is preferable to set it as 3 to 0.2 times. The stirrer is attached to a drive (not shown). The stirrer is gradually raised during driving according to the rise of the crystallized aluminum surface so that the distance from the crystallized aluminum surface is always within a certain range. ! When the crystallization operation is complete, remove the stirrer from the container.

By heating when remelting the crystallized aluminum,
Avoid damaging the agitator. Therefore, the stirrer is installed so that it can be moved up and down in this manner. (9) is an inlet for molten aluminum provided on the short side wall. (10) is a burner, which heats the surface of the molten aluminum during the crystallization operation to prevent aluminum from crystallizing on areas other than the bottom surface;
After the crystallization is completed, the remaining mother liquor is discharged and the crystallized aluminum is fully heated and redissolved after fc.

In order to completely purify aluminum by the method of the present invention using the apparatus shown in the figure, first the molten aluminum inlet (9
), and stir it by inserting the stirrer (8) into it. Next, the floor (3) is cooled by circulating air or other cooling medium through the cooling medium distribution pipe (5),
Aluminum αυ is crystallized on the floor surface. The cooling medium flow ftf'i, the crystallization rate of aluminum, that is, the rate of rise of the aluminum crystallization surface is /θ~/j OwR/
It is preferable to select the time accordingly. You can also use a stirrer (
The rotational speed of 8) is /~10 as the tip speed of the stirring blade.
rIL/sec is a good name. It is necessary that the stirrers (8) all rotate in the same direction. If the rotating directions of the adjacent λ agitators (8) are different, a suction side and a discharge side are formed, and the flow of molten aluminum stagnates on the suction side. Therefore, dendrites tend to form in this stagnation area, and impurities removed during crystallization remain between the crystals, reducing the purity of the crystallized aluminum.

During the crystallization operation, burner αQ heats the molten aluminum surface to compensate for heat losses from the surface and sidewalls;
Prevent aluminum from crystallizing anywhere other than the bottom surface. Heating may be continuous or intermittent, but the temperature is maintained at a temperature slightly higher than the melting point of the molten aluminum, usually about 1°C, and the distance between the crystallization surface and the lower end of the stirring blade is approximately 1°C. Make it constant. Typically this distance is 10~io,
o- is good. Detection of the crystallization plane can be performed using the IF tangent or can be estimated indirectly from the cooling heat needle.

Aluminum of f9r 5jLic, usually 30-20% of the charged aluminum, preferably gθ~SO%
When , crystallizes, the crystallization stops, and the apparatus is fully tilted to allow the remaining molten aluminum to flow out from the discharge port (6). During the crystallization operation, it was impossible to supply and discharge molten aluminum to and from the entire device, so the agitator (8) was pulled out of the device, and the molten aluminum was rapidly heated with a burner.
It is advantageous to reduce its viscosity. Usually ≦! ~
It is heated to 62° C. to cause the molten aluminum to flow out, but it may be heated to a higher temperature if rapid heating is possible to avoid excessive melting of the crystallized aluminum.

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 allow purified molten aluminum to flow out from the discharge port (7). The product is then cast into a predetermined shape.

According to the method of the present invention, aluminum can be efficiently purified using a large-sized device.

[Brief explanation of drawings]

FIG. 1 is a plan view of the lower part of an apparatus suitable for carrying out the invention, with arrows indicating the direction of flow of the cooling medium. FIG. 1 is a longitudinal cross-sectional view of the device of FIG. 1 along line A-A'. FIG. 3 is a longitudinal cross-sectional view of the device of FIG. 1 along line B-B'. In addition, in FIG. 1 and FIG. 3, the part in front of the support device of the stirrer is omitted. Tll Insulating brick layer (2) Refractory brick layer (3
) Carbonaceous material layer (4) Carbon block (5) Coolant flow pipe (61, (7) Molten aluminum outlet (8)
Stirrer (9) Molten aluminum inlet α0)
Burner αη Crystallized aluminum layer Patent applicant Mitsubishi Light Metal Industries, Ltd. Representative Patent attorney Hase - Others/names

Claims (4)

[Claims] (1) Molten aluminum is placed in a container equipped with at least a rectangular stirrer with a ratio of the length of the long axis to the short axis of 2 or more, and all the stirrs are rotated in the same direction in Φ to melt the aluminum. A method for purifying aluminum, which comprises cooling a bed while stirring aluminum to crystallize high-purity aluminum on the surface of the bed, and then separating the crystallized aluminum from the remaining molten aluminum. (2) The method according to claim 1, wherein the horizontal bed is made of a carbonaceous material with high thermal conductivity and has a cooling medium flow pipe therein. (3) As the aluminum crystallizes on the bed, the stirrer is pulled upward, and the distance between the crystallized aluminum surface and the stirrer is maintained approximately constant during the crystallization. Well, IC is the method described in Section 2. (4) The method according to any one of claims 1 to 3, characterized in that the surface of the 11!11 Jδ fused aluminum crystallized onto the bed is heated continuously or intermittently.