JPH08199254A - Rotary cooling body for aluminum refining and method thereof - Google Patents

Abstract

PURPOSE: To recover high purity refined aluminum from aluminum molten metal in high yield. CONSTITUTION: A rotary cooling body 30, which has an inner tube 31 inserted concentrically into an outer tube 32 connected to the supply source of a cooling medium 40 and in which a cooling chamber 44 is formed between a flange 33 mounted to the lower end of inner tube 31 and a bottom wall 37, is immersed from the upper side of a refining vessel 10 in an aluminum alloy molten metal M. Plural ruggednesses are laid concentrically, helically, radially or dottedly on the bottom wall 37. After an intermetallic compound 1 is crystallized from the molten metal M, the cooling medium 40 is supplied, the α-Al crystal crystallized from molten metal M by cooling is stuck/grown on the bottom wall 37 and side wall 36. Ruggedness prevents stuck α-Al crystal from falling off, and thereby the refined aluminum is recovered in high yield.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a rotary cooling used for efficiently refining an aluminum alloy melt prepared by melting a high-purity aluminum melt whose primary crystal is an α-Al crystal or scrap. Body and purification method.

[0002]

2. Description of the Related Art There is known a method of purifying aluminum by adding impurities such as Fe and elements forming an intermetallic compound to a molten aluminum and separating the crystallized intermetallic compound. For example, JP-A-57-2134
In Japanese Patent Laid-Open No. 59-12731, Mn or Al-Mn and M are added.
g or Al-Mg is added together. In either method, Fe as an impurity is separated and removed as an Al-Fe-Mn-based intermetallic compound. When the impurities are separated and removed by adding Mn, an excessive amount of Mn is added, so that the purified aluminum material contains a large amount of Mn as impurities. Therefore, the removal of this Mn becomes a problem.

JP-A-57-92148 introduces a method of purifying an aluminum material having a relatively high purity by utilizing segregation solidification. In this method, the molten aluminum contained in the crucible is cooled and solidified from the bottom of the crucible while stirring the molten aluminum with a stirrer. The high-concentration impurity solution at the solidification interface diffuses upward from the solidification interface without being caught in the solidified body by the stirring flow of the molten aluminum given by the stirrer.
Therefore, a high-purity aluminum material is produced as a solidified body at the bottom of the crucible. The high-concentration impurity solution released from the solidified body diffuses throughout the molten aluminum. Therefore, as the solidified body grows, impurities are concentrated in the remaining molten aluminum. When the impurity concentration is high, it is impossible to prevent the impurities from being taken into the solidified body. Therefore, when purifying an aluminum material by the method described in JP-A-57-92148, when about half of the molten amount of the aluminum material injected into the crucible is solidified, the remaining aluminum molten material has to be discharged from the crucible. I can't. That is, the whole amount of the aluminum material charged in the crucible is not purified as a solidified body, and the purification method is poor. In addition, since aluminum materials that are not refined as solidified bodies also heat and melt,
The heat energy wasted in vain is also large.

[0004]

The inventors of the present invention have developed a refining method for solving the above drawbacks by crystallizing refined aluminum on the lower surface of the cooling body set in the upper part of the container. It was introduced in Japanese Patent Publication No. 295465.
In this method, the intermetallic compound crystallized along with the refining of aluminum falls to the bottom of the container to improve the refining efficiency. Further, in order to further enhance the action of the cooling body on the crystallization separation of the intermetallic compound, the cooling body is rotated to further promote the crystallization separation of the intermetallic compound, and a method and apparatus for purifying aluminum with higher efficiency. Japanese Patent Application No. 6-23
Proposed in No. 0730. In this proposed apparatus, after crystallizing and growing α-Al crystals on the lower surface of the rotary cooling body, the rotary cooling body is pulled up to separate the crystallized substance from the molten metal.
Obtain purified aluminum. The present invention aims to obtain refined aluminum with a high yield by further improving the function of the rotary cooling body introduced in the prior application and by giving the rotary cooling body a function of restraining the crystallized α-Al crystals. And

[0005]

In order to achieve the object, the rotary cooling body for an aluminum refining apparatus of the present invention is immersed in a molten aluminum alloy from above a refining vessel, and crystallized α-Al crystals are formed on the bottom surface. A rotary cooling body that adheres and grows, an outer tube connected to a source of a cooling medium, and an inner tube that is concentrically inserted through the outer tube and discharges the cooling medium used to cool the molten metal, An outer pipe side flange attached to the lower end of the outer pipe, and attached to the lower end of the inner pipe,
A plurality of irregularities are formed by surrounding the inner pipe side flange having a plurality of orifices formed on the radially expanded surface, the lower end portion of the outer pipe, the lower end portion of the inner pipe and the inner pipe side flange. And a casing whose lower end side is closed by a bottom wall, wherein the cooling medium is from a distribution chamber formed between the outer pipe side flange and the inner pipe side flange, and passes through the orifice to the inner pipe side flange. It is characterized in that it is fed into a cooling chamber formed between it and the bottom wall and discharged through the inner pipe.

The plurality of concavities and convexities provided on the lower surface of the outer tube side flange can be arranged in a concentric circle shape, a spiral shape, a radial shape, a dot shape, or a combination thereof. Further, the side plates forming the casing may be provided with irregularities. When refining the aluminum alloy molten metal in which the intermetallic compound crystallizes as the primary crystal, after separating the precipitated intermetallic compound by precipitation,
The rotating cooling body immersed in the molten aluminum alloy is rotated while supplying the cooling medium to crystallize and grow α-Al crystals on the lower surface of the bottom wall and the outer surface of the side plate. When the α-Al crystal grows to a predetermined thickness, the rotary cooling body is pulled up from the molten metal to separate the crystallized product of the α-Al crystal from the residual hot water to obtain purified aluminum. The intermetallic compound deposited on the bottom is redissolved and then discharged from the refining device together with the residual hot water. The molten metal refined according to the present invention is a relatively high-purity aluminum molten metal whose primary crystal is α-Al crystal, or an aluminum alloy molten metal prepared by melting scraps, etc., in particular, an intermetallic compound crystallizes as a primary crystal. Aluminum alloy melt, etc.
It is a molten aluminum of any purity.

The refining method according to the present invention is carried out by using the apparatus having the equipment structure shown in FIG. The device shown in FIG. 1 has the same basic configuration as proposed in Japanese Patent Application No. 6-230730, but the gas passages, bottom wall, side plates, etc. formed inside the cooling body are different. As the refining vessel 10, a graphite crucible or a crucible obtained by mixing and firing graphite and SiC is usually used. The crucible body 11 is put in the outer container 12, and the lid 13 is attached. A burner 14 for temperature control may be attached to the lid 13. The bottom of the refining vessel 10 preferably has the lowest center in the bottom and an inclined surface inclined upward toward the periphery so that impurities crystallized from the molten metal M are easily deposited, but refining with a flat bottom is preferred. The container 1 can also be used. A heating mechanism 20 is provided on the outer periphery of the purification container 10.
Are arranged so as to surround the outer container 12. Heating mechanism 2
No. 0 is provided with heater blocks 22 to 24 made of refractory bricks with a heater 21 attached to the inner peripheral side, and each heater block 2
It is preferable that the amount of heat of 2 to 24 is independently controlled.
The heater block 25 is also arranged at the bottom of the purification container 10. By adopting the independently controllable heater blocks 22 to 24, the vertical temperature distribution of the molten metal M in the refining vessel 10 can be adjusted.

The aluminum scrap to be refined may be melted in a melting furnace and charged into the refining vessel 10.
Alternatively, the scrap may be directly charged into the refining vessel 10 and then melted by heating from the heater blocks 22 to 25. The molten metal is maintained at a temperature at which the AlSiFeMn-based intermetallic compound crystallizes, specifically, 680 to 600 ° C.
After precipitating and separating the intermetallic compound that crystallizes as a primary crystal by this high temperature holding, the cooling medium 40 is supplied to the rotary cooling body 30 in the range of the molten metal temperature of 600 to 570 ° C. The α-Al crystal is crystallized. The rotary cooling body 30 has a double pipe structure in which an outer pipe 32 is fitted to an inner pipe 31. An inner pipe side flange 33 and an outer pipe side flange 34 are attached to the lower ends of the inner pipe 31 and the outer pipe 32, respectively, which are spread in the radial direction. Inner pipe side flange 33
3, a plurality of orifices 35 are formed in a substantially uniform density distribution, as shown in FIG. The inner pipe side flange 33 forms a distribution chamber 43 (FIG. 2) between the inner pipe side flange 33 and the outer pipe side flange 34. Although the inner pipe 31 and the outer pipe 32 are made of stainless steel in this example, a graphite block having a predetermined gas passage may be used. The flanges 33 and 34 have a circular shape, and have a structure in which the peripheral edges are closed.

A casing having a side plate 36 is provided so as to surround the flanges 33 and 34. Side plate 36
The bottom wall of the bottom wall 3 has a constant distance from the flange 33.
7 is attached, and a cooling chamber 44 is formed between the inner pipe side flange 33 and the bottom wall 37. As shown in FIG.
As shown in FIG. Unevenness 3
As shown in FIG. 4, as shown in FIG. 4, concentric continuous ridges and grooves (a), spirally continuous ridges and grooves (b), and radially continuous ridges and grooves (c). , And are formed by dot-like projections or recesses (d) which are dispersed at substantially equal intervals. Moreover, as shown in FIG. 5, the cross section of the unevenness has a straight concave portion or convex portion (a), an inverted trapezoidal concave portion or trapezoidal convex portion (b), a head-equipped bolt or the like attached ( c) etc. Furthermore, it is also possible to combine the irregularities shown in FIGS. 4 and 5. For example, FIG. 4A shows an example in which two linear irregularities are combined with concentric circular irregularities, and FIG. 4B shows an example in which concentric circular irregularities are combined with radial irregularities. In any case, due to these irregularities 38, the lower surface of the bottom wall 37 is not flat, and the mechanical restraining force for the α-Al crystal attached thereto increases, and
Cooling efficiency is also improved by increasing the cooling area. Further, when the unevenness 39 is also formed on the side plate 36, the mechanical restraining force on the α-Al crystal that crystallizes on the side plate 36 is further increased.

A cooling medium 40 such as air or an inert gas is sent from the supply port 41 to the outer pipe 32, and the inner pipe 31 and the outer pipe 3 are connected.
2 through the annular passage 42 formed between the flange 3
It is introduced into a distribution chamber 43 formed between 4 and 33.
Then, the cooling medium 40 flows into the cooling chamber 44 via the orifices 35, 35. At this time, the cooling medium 40
After being once introduced into the cooling chamber 44 from the annular passage 42 into the distribution chamber 43 having a large internal volume, the flow rate distribution in the radial direction is made uniform. The cooling medium 40 in the cooling chamber 44 cools the molten metal M via the bottom wall 37. Since the heat removal capability of the cooling medium 40 is made uniform within the surface of the bottom wall 37, α-Al crystallizes uniformly from the cooled melt M on the lower surface of the bottom wall 37. The cooling medium 40 that has been heated by heat exchange with the molten metal M is discharged from the cooling chamber 44 to the outside of the system through the exhaust passage 45 in the inner pipe 31 and the exhaust port 46. When the plurality of exhaust ports 46 are provided, they are opened at the upper end of the inner pipe 31 at equal intervals in the circumferential direction around the rotation axis of the rotary cooling body 30.

The outer tube 32 extends upward through the lid 13 and is connected to the output shaft 53 of the motor 52 via a coupling 51. The arm 54 extending from the motor 52 is
It is fitted into a feed screw 56 rotated by a motor 55. As a result, the rotary cooling body 30 rotates in the refining container 10 so as to be vertically movable. For the cooling medium 40, air, non-oxidizing gas, air containing mist-like water, or the like is used. Due to the flow of the cooling medium 40, the molten metal M is cooled via the bottom wall 37, and α-Al crystals grow on the lower surface of the bottom wall 37. The temperature of the molten metal M and the growth rate of the α-Al crystal are optimally maintained by controlling the flow rates of the heater blocks 22 to 24 and the cooling medium 40. When the temperature of the molten metal M is maintained in the range of 680 to 600 ° C., in the system where the primary crystal is an intermetallic compound, for example, A
The 1-Si-Fe-Mn-based intermetallic compound crystallizes out. Since this crystallized substance has a larger specific gravity than the molten metal M, the molten metal M
The inside is settled and deposited at the bottom of the purification container 10.

At this stage, the rotary cooling body 30 is kept inactive without feeding the cooling medium 40 so that crystallized substances do not adhere to the lower surface of the rotary cooling body 30. Or Al
While the crystallization of the —Si—Fe—Mn intermetallic compound is in progress, the rotary cooling body 30 is held above the molten metal surface without being immersed in the molten metal M. Crystallization of the Al-Si-Fe-Mn-based intermetallic compound can be controlled by the temperature of the molten metal M, and the Al-Si-Fe-Mn-based intermetallic compound is separated from the molten metal M in the temperature range of 680 to 600 ° C. Crystallize and separate. With the crystallization of the intermetallic compound, the remaining molten metal M is purified. Then, crystallization of α-Al crystals starts when the temperature of the molten metal M is in the range of 600 to 570 ° C. Therefore, the cooling medium 40 is supplied to the rotary cooling body 30, or the rotary cooling body 30 is supplied.
Is immersed in the melt M to crystallize and grow α-Al crystals on the bottom wall 37 of the rotary cooling body 30. At this time, α-Al crystal and molten metal M
The purified concentrated liquid at the interface with and is diffused into the molten metal M by the centrifugal force caused by the rotation of the rotary cooling body 30. Therefore, a predetermined concentration gradient is maintained at the solidification interface, and crystallization of α-Al crystals is promoted.

The bottom wall 37 has a large concavity and convexity 38 on the lower surface from which the α-Al crystal is crystallized, and therefore has a great restraining force on the α-Al crystal. Therefore, the centrifugal force generated by the rotation of the rotary cooling body 30 prevents the crystallized product of the α-Al crystal from separating from the bottom wall 37, and the purified aluminum is recovered with a high yield. In addition, a large amount of α-Al crystals are added to the bottom wall 37.
Can be attached and held. The rotary cooling body 30 is α-
When the Al crystal is solidified, it rotates at a peripheral speed for diffusing the impurity element and the intermetallic compound I crystallized into the molten metal M. At an excessively high rotation speed, the vortex generated by the rotation of the rotary cooling body 30 becomes large, and not only the oxidation of aluminum, which causes a decrease in yield, progresses, but also the molten metal M scatters, which causes safety and operational inconvenience. Occurs. Further, the solidified α-Al crystal is scattered into the molten metal M by the centrifugal force, and the solidification efficiency is deteriorated.

Specifically, the rotation speed of the rotary cooling body 30 is preferably set at an outer peripheral speed of 0.2 to 8 m / sec. Also,
In order to prevent the oxide film floating on the surface of the molten metal M from being entrained, it is preferable to rotate the rotary cooling body 30 in one direction, but the rotary cooling body 30 may be periodically rotated alternately.
The purity of the molten metal M decreases with the crystallization of α-Al crystals, and approaches the eutectic composition. Therefore, when the concentration of the molten metal reaches a predetermined level while constantly detecting the concentration of the molten metal M, or when the refining end time predicted from the refining raw material such as aluminum scrap is reached, the supply of the cooling medium 40 and the rotary cooling body are performed. The rotation of 30 is stopped and the motor 55 is rotated to take out the rotary cooling body 30 from the crucible body 11. Immediately thereafter, the entire refining vessel 10 is tilted, and the remaining molten metal M and the intermetallic compound I deposited on the furnace bottom are discharged. Next, the α-Al crystals crystallized on the bottom wall 37 of the rotary cooling body 30 are transferred to the refined metal recovery furnace arranged on the refinement furnace side, melted and recovered.

[0015]

EXAMPLE A graphite crucible having an inner diameter of 430 mm and a height of 720 mm was mounted on the refining apparatus shown in FIG. 1, and 150 kg of aluminum raw material having a composition in which the primary crystal was an intermetallic compound was used.
Melted at 60 ° C. Then, by holding the molten aluminum at 610 ± 5 ° C. for 5 hours, the intermetallic compound crystallized from the molten M was settled and separated at the bottom of the refining vessel 10.
The molten aluminum changed its concentration as shown in Table 1 by holding at a high temperature, and the impurities such as Si, Fe, Cu, Mn, and Cr were reduced.

[0016]

[Table 1]

After precipitating and separating the intermetallic compound, α-Al crystals were crystallized when the melt M was in the range of 600 to 570 ° C. As the rotary cooling body 30, as shown in FIG. 4 (a), 6 concentric circular concavo-convex and 2 diametrically-shaped bottom walls 37 having a cross-sectional shape of FIG. The one having a side wall 36 having a height of 100 mm and having two irregularities formed in the direction was used. Then, the rotary cooling body 30 was set so that the bottom wall 37 was positioned at a depth of 20 mm from the surface of the molten aluminum. While supplying cooling air as the cooling medium 40 to the rotary cooling body 30 at a constant flow rate of 3,000 liters / minute, the rotary cooling body 30 was rotated under the conditions shown in Table 2. The α-Al crystals crystallized from the molten metal M adhered to the bottom wall 37 of the rotary cooling body 30 and grew in the shape shown in FIG. As shown in Table 2, in the crystallized substance of the α-Al crystal, the concentration of elements other than Ti decreased as the rotation speed of the rotary cooling body 30 increased. However, if the rotation speed was excessively increased, the purified weight tended to decrease. It is speculated that the decrease in the purified weight is caused by the crystallized α-Al crystals being scattered by the centrifugal force. Therefore, in order to carry out purification to a predetermined target purity and increase the purification yield,
It can be seen that the rotation speed has a suitable range.

[0018]

[Table 2]

For comparison, an aluminum melt was purified under the same conditions using the rotary cooling body 30 equipped with the bottom wall 37 having no unevenness 38. In this case, Table 3
As shown in B1 to B3, the α-Al crystals attached to the rotary cooling body 30 often fall off, and B4 that does not fall off
The refined weight of B5 was significantly smaller than that of Table 2.
Moreover, in the case of B5 in which the cooling capacity is set to be large by setting the cooling air supply rate to 3,000 liters / minute, the purification purity is lowered due to the faster solidification rate. From this comparison, the unevenness 38 formed on the bottom wall 37 shows that crystallized α-Al.
It can be seen that the crystal has a large restraining force and is effective in preventing the α-Al crystal from falling off during purification.

[0020]

[Table 3]

[0021]

As described above, the rotary cooling body for a refining device according to the present invention is provided with unevenness on the bottom wall.
The mechanical restraining force for the α-Al crystals crystallized on the lower surface of the cooling body is increased and the cooling capacity is also increased. for that reason,
Α-Al crystallized from the molten aluminum on the bottom surface of the bottom wall
The crystals are separated from the residual hot water as purified aluminum by pulling up the rotary cooling body after the purification without dropping off from the rotary cooling body during the purification. Therefore, when using the rotary cooling body of the present invention, purified aluminum is recovered with a high yield. Further, when refining an aluminum melt in which an intermetallic compound crystallizes as a primary crystal, by precipitating and separating the intermetallic compound and then crystallizing an α-Al crystal on the bottom wall of the rotary cooling body, the impurity concentration is increased. A product with reduced purity and high purity can be obtained.

[Brief description of drawings]

FIG. 1 is a refining apparatus adopted in an embodiment of the present invention.

FIG. 2 is a sectional view of a rotary cooling body.

[Fig. 3] Inner pipe side flange with multiple orifices

FIG. 4 shows several examples of bottom walls having a plurality of irregularities.

FIG. 5 shows several examples of the cross-sectional shape of the unevenness formed on the bottom wall.

FIG. 6 α-Al crystals growing on the bottom wall of the rotary cooling body

[Explanation of symbols]

M: Molten aluminum I: Crystallized intermetallic compound 10: Purification vessel 20: Heating mechanism 30: Rotating cooling body 31: Inner tube 32: Outer tube 33: Inner tube side flange 34: Outer tube side flange 35: Orifice 36: Side plate 3
7: Bottom wall 38: Asperity on bottom wall 39: Asperity on side wall 40: Cooling medium 41: Supply port 4
2: Annular passage 43: Distribution chamber 44: Cooling chamber 4
5: Exhaust passage 46: Exhaust port

Claims (4)

[Claims] 1. A rotary cooling body which is immersed in a molten aluminum from above a refining vessel and crystallized α-Al crystals adhere to and grow on the bottom surface, and an outer tube connected to a supply source of a cooling medium; An inner pipe that is concentrically inserted through the outer pipe to discharge the cooling medium used to cool the molten metal, an outer pipe side flange that is attached to the lower end of the outer pipe, and an inner pipe that is attached to the lower end of the inner pipe. The inner pipe side flange having a plurality of orifices formed on the radially expanded surface, the lower end portion of the outer pipe, the lower end portion of the inner pipe, and the inner pipe side flange are surrounded, and a plurality of irregularities are formed. A casing whose lower end side is closed by a formed bottom wall, wherein the cooling medium flows from the distribution chamber formed between the outer pipe side flange and the inner pipe side flange through the orifice to the inner pipe side. Formed between the flange and the bottom wall Fed into the cooling chamber, rotating cooling body for aluminum refining system is discharged through the inner tube. 2. The rotary cooling body for an aluminum refining device, wherein the plurality of irregularities formed on the lower surface of the bottom wall according to claim 1 are arranged in a concentric circle shape, a spiral shape, a radial shape or a dot shape. 3. A rotary cooling body for an aluminum refining apparatus, wherein concavities and convexities arranged concentrically, spirally, radially or in dots are formed on a side plate constituting the casing according to claim 1. 4. The rotation according to claim 1, wherein when the molten aluminum alloy in which the intermetallic compound crystallizes as a primary crystal is purified by a refining device, the crystallized intermetallic compound is separated by sedimentation and then separated. Rotate while supplying the cooling medium to the cooling body,
An aluminum refining method of crystallizing and growing α-Al crystals on the lower surface of the bottom wall and the outer surface of the side plate.