MXPA01005112A - Improved apparatus and process for separating aluminium from a mixture of aluminium and aluminium dross - Google Patents

Abstract

An apparatus (14) for separating molten Aluminium from a mixture of molten aluminium and aluminium dross includes a table (16, 54) for supporting an insulated crucible (59, 75) containing the mixture of aluminium and aluminium dross. Electrical, mechanical or ultrasonic vibrators (70) or the like are provided to vibrate the table and crucible (59, 75). A frame (50, 52, 54) supports a rotatable paddle (18, 64), which can be lowered into the mixture in the crucible (59, 75) for stirring the mixture enabling simultaneous vibration of the crucible (59, 75) and stirring of the mixture. By virtue of that stirring and vibration, the aluminium droplets and particles of the dross coalesce to form larger droplets and gradually sink to the base of the crucible (59, 75). The aluminium can then be drained out into a bucket (20, 20a, 76). A screening means is disposed to substantially surround the crucible (59, 75) when it is supported by the table (16, 54). The screening means includes a door (72) to allow access to the crucible (59, 75) in one position and in a second position prevents access to the crucible (59, 75). A hood (80, 83) is provided at the top of the apparatus (14) so that the crucible (59, 75) is substantially fully enclosed. Gas burners (88, 90) may be used to retain heat in the crucible (59, 75) and contents.

Description

IMPROVED APPARATUS AND PROCESS TO SEPARATE ALUMINUM FROM AN ALUMINUM MIXTURE AND ALUMINUM SCENE FIELD OF THE INVENTION This invention relates to an apparatus and a process for separating aluminum from a mixture of aluminum and aluminum slag. In particular, the invention relates to a process for recycling aluminum from the slag produced during an aluminum smelting process, and to an apparatus for carrying out that recycling process.

BACKGROUND OF THE INVENTION When the aluminum is melted, for example, for the manufacture of extrusions of ingots and billets, due to the influence of the oxygen coming from the ambient air on the aluminum and the existence of impurities, particularly oxides, nitrides and carbides, in the molten aluminum, A layer of sediment, also known as slag emerges towards the surface of the molten aluminum. This layer of slag has to be removed from the molten aluminum before the molten aluminum can be emptied. This is done by using a suitable pouring kettle. In a rather crude process, known as skimming, the pouring cauldron is dragged through the upper part of the molten aluminum and the slag is scraped into a suitable receptacle or reservoir. During the skimming process, as well as the removal of sediment that includes oxides and other impurities, pure aluminum is also removed. The amount of pure aluminum removed depends on the depth at which the pouring cauldron is inserted into the aluminum to ensure the removal of all the slag and to a greater degree depends on the skill of the furnace worker operating the casting cauldron. However, typically 30 to 60% of the mixture / impurity by weight is aluminum. The term slag, as used herein, refers to impurities such as oxides that float to the surface of aluminum, but the term is also used in the art to refer to the mixture of aluminum and impurities. Due to the amount of aluminum in the mixture, it is obviously desirable to remove as much aluminum from the slag / aluminum mixture as possible. Almost all the recycling is done through a process known as processing in a rotary kiln. In that process, the slag containing pure aluminum is first allowed to cool. The longer the aluminum is heated, the more oxidation occurs and less aluminum is recovered in the recycling process, so that cooling is often promoted and accelerated. In some cases, some initial separation of the aluminum from the mixture is first carried out by one of two more inefficient devices, known as drainage coppers and slag presses, respectively. In the first, the mixture is allowed to settle while it is melted, and some of the aluminum will melt towards, and will agglomerate in, the bottom of the pan. In the second device, the mixture is compressed and the aluminum droplets tend to agglutinate each other. These processes are inefficient and have to be followed by rotary salt processing or other external slag processing methods. Because the mixture is kept hot for a longer time for the drainage perol or slag press process, the rate of recovery in the subsequent rotary salt process is reduced, so draining coppers and slag presses are generally non-commercially viable and often not used.

Recycling is not generally done in the furnace, but is usually used by companies specialized in recycling metals. In the rotary salt recycling process, the slag is heated and melted again, and various salts and flows are added in order to separate the aluminum from the oxides and other impurities. While the process is highly efficient in terms of the amount of aluminum removed from the slag, the removal of approximately 85% of available aluminum, the waste product from the recycling process, for example the mixture of salts and oxides, is not pleasant, is environmentally unfriendly, and difficult to dispose of safely. In addition, the process requires the transportation of the slag to the recycler in motorcars or the like, which is also undesirable from an environmental point of view, and inefficient in terms of fuel. Also, the slag has to be melted again in order to extract the aluminum in the recycling process, which requires a substantial amount of energy. There are some foundry plants that have their own rotary saline recycling furnace, however, the cooling and transportation process of the cooled mixture to the furnace remains the same, although savings in total transport costs are realized. Proposals have been made to separate aluminum from slag in the past, British Patent GB-1533696 and US Patent No. 3689049 describe two different devices for separating aluminum from slag. No device has had any commercial success, perhaps because these are very complicated and too unreliable for the extreme environment in which they have to operate. The present inventor has also invented an apparatus and a process, described in AU-56260/98, which provides a simpler and lower cost method for recycling aluminum from the slag. The present invention is directed to the improvements in the devices previously developed by the inventor.

BRIEF DESCRIPTION OF THE INVENTION According to a first aspect, the present invention is an apparatus for separating molten aluminum from a mixture of molten aluminum and aluminum slag which includes: a table for supporting an insulated crucible, containing the mixture of molten aluminum and aluminum slag, the mixture is adapted to vibrate, to vibrate the crucible; a frame or structure adapted to support a pallet means or agitating means, the means for rotating the pallet means and the means for relatively lowering the same towards the mixture in the crucible, for stirring the mixture with the pallet means , making possible the simultaneous vibration of the crucible and the fixation of the mixture; and a sieving means capable of substantially surrounding the crucible when it is supported by the table, the sieve means has at least a portion thereof movable between at least a first retracted position to allow access to the crucible, and at least a second position where it prevents access to the crucible. The screening medium can be removably mounted to the frame. In this embodiment, the movable portion may comprise a door that is retractable to allow access to the appliance table. The door can be adapted to move up, laterally or downward, to provide a portal for accessing the table. The door can be slidably movable relative to the rest of the screen medium. In yet another embodiment, the door can be pivotably mounted to the wall. When the door is completely retracted, the portal should be of sufficient size to allow the crucible to pass through the portal. In yet another embodiment, the complete screen means may be movable between the first retracted position and the second position. In this embodiment, the sieve means may extend downwardly from the descent means for the pallet means, and is thus movable relative to the table and the crucible, in unison with the operation of the descent means. The sieving means is preferably adapted to prevent or at least improve the escape of heat from the vicinity of the crucible. By preventing the escape of heat, the screening medium serves to protect the workers who work near the appliance. This also serves to decrease the cooling speed of the crucible and its contents, which is desirable. The screening means may also be preferably adapted to prevent or at least substantially prevent the escape of dust and flame from the vicinity of the crucible. The sieving medium can also be adapted to safeguard workers working in the vicinity of the apparatus, from the explosion of aluminum and slag from the crucible. The screening medium is preferably formed of a multilayer structure, comprising at least one inner layer and one outer layer. The inner and outer layers can be fabricated from a suitable metal or other material, including refractory and cementitious materials. The blade or stirring means may comprise a plurality of blades mounted on an axle supported by a frame, the shaft is adapted to be raised or lowered, so that the blades can be raised when a new crucible is placed on the table placed below the blades. In one embodiment, in use, the shaft is placed at or near the center of the crucible and is rotatable by a rotary means about its longitudinal axis. In a further embodiment, the shaft, in use, is radially displaced from the center of the crucible and is, in addition to rotating about its longitudinal axis, also rotated by the means of rotation about the center of the crucible, thereby providing agitation more complete of the contents of the crucible. In a further embodiment, a gear is provided such that the shaft undergoes a planetary movement as it is rotated by the rotating means about the center of the crucible. This additional rotation of the blades leads to an even more complete stirring of the contents of the crucible. The crucible can be made of a refractory material having a metallic outer film spaced from the refractory material by an insulating layer. The crucible may be provided with a covering means that covers at least partially the upper opening of the crucible. The cover may be retractable or otherwise removable from the crucible when the paddle or agitation means is relatively lowered into the crucible. If desired, the cover can be adapted to surround the axis of the pallet means or agitation, while the paddle or agitation means is stirring the contents of the crucible. The table can be mounted on springs to help the vibration of the crucible. The vibration of the table and crucible cel can be achieved by mounting at least one ultrasonic transducer, electric vibrator, mechanical vibrator or a combination of one or more of these transducers to the crucible and / or the table. The table can be vibrated such that it oscillates on a horizontal axis, a vertical axis or on both axes. The framework may consist of two or more vertical pillars. A transverse beam can be supported by the frame and that transverse beam can carry the rotating means. The shaft for the blades can protrude down from the cross beam with the blades mounted on the lower end of that shaft. The apparatus may include one more exhaust pipes that allow the gaseous product from the process performed by the apparatus to be vented to the atmosphere outside the screening medium. The exhaust pipes can incorporate bagged systems that collect the gaseous exhaust product for subsequent disposal. The bagging systems can also be adapted for or instead of extracting the powder from the gaseous product. The exhaust systems may also include filtration or purification means that clean or substantially clean the gaseous product from the process of the hazardous or potentially hazardous constituents. The apparatus may include a weighing means, such as an electronic or mechanical balance, which allows the measurement of the weight of the crucible and its contents while the crucible is seated on the table. The apparatus may also include a control means. The control means is preferably adapted to allow an operator to operate all the characteristics of the apparatus from a central position. In a further preferred embodiment, the control means may be automated such that the apparatus normally runs without operator participation. Thus, in a further aspect of the present invention, there is provided an apparatus for separating the molten aluminum from a mixture of molten aluminum and aluminum slag which includes: a table for supporting an insulated crucible containing the molten aluminum mixture and aluminum slag; a means of weighing, such as an electronic or mechanical balance to measure the weight of the crucible and its contents, while the crucible is seated on the table; a frame adapted to support a paddle means or stirring means, the means for rotating the paddle means and the means for relatively lowering the same inside the mix in the pot, to stir the mix with the paddle means, making possible the simultaneous vibration of the crucible and the stirring of the mixture; a sensor means for detecting the pressure on the paddles on the agitation; and an accommodating control means for determining the optimum agitation time from the pressure measurements on the blades and / or the weight of the crucible and the contents. The control means can also control the sequence and speed of the vibrations. While the size of the crucible containing the slag is not important, typically the crucible must be large enough to carry between 800 kilograms to 1.5 tons of slag. The process takes approximately 10 minutes and removes up to 95% of the aluminum in the slag, therefore the present invention can separate approximately 1000 kilograms of aluminum from the slag every 4-10 minutes. Typically, the crucible will include plugged holes that are plugged before carrying out the separation process for example with a cone or clay sand solution, and are uncovered to drain the crucible into a drainage pan. The drainage basin preferably has a cover, which has an inlet gate, which encloses the drainage pan. In use, the aluminum that is drained from the crucible at the end of the process cycle, passes through the inlet gate and into the additional drain pan. Since there is a risk of an explosion if the molten aluminum comes in contact with moisture in the additional drainage pan, the cover preferably contains any explosion if it occurs, thereby ensuring the safety of the workers who are nearby. In an alternative embodiment, the apparatus may include an additional drainage pan adapted to be placed directly below the crucible, which is engageable to the crucible and movable so, if desired, with the crucible when the crucible is moved in and out of the crucible. apparatus. Where the crucible has a drainage basin, the crucible could preferably have one or more drainage holes in or adjacent to its bottom surface and in fluid communication with the drainage basin, so that the aluminum can be drained into the drainage basin . The provision of a drainage basin is advantageous, since it allows the collection of the aluminum that moves towards the bottom of the crucible to be easily recovered from the crucible. This has particular application in those chaos where the aluminum content of the aluminum / slag mixture is relatively high, for example about 65-85% aluminum. If the aluminum can not be drained in these cases, it is possible that the previously melted aluminum in the mixture closest to the top of the crucible, will begin to solidify before the completion of the process of agitation and vibration according to the present invention. By lowering the level of mixing during the process, using the draining copper, the probability of solidification in the crucible is reduced before the completion of the process. One or more drainage holes that are in fluid communication with the drainage basin may be sealable by a sealing means. Each sealing means can be mounted to the crucible at all times, and moved inside or outside the sealed coupling with its respective drainage hole, as desired. It will be appreciated that the apparatus could be adapted to receive more than one crucible at one time. For example, the apparatus could comprise two or more tables and agitating means to allow the contents of two or more crucibles to be stirred simultaneously. In another example more, the apparatus should comprise two or more tables but only a means of agitation. In this mode, the contents of each crucible could be agitated sequentially. As such, the option could be left open for the contents of a crucible that is to be agitated and vibrated, while another crucible is being filled with the slag mixture and placed in the apparatus. When the process cycle is completed on the first crucible, the agitation medium could be relatively high, moved and then relatively lowered into the next crucible. While this is happening, the recovered aluminum can be drained from the first crucible and this can be removed from the apparatus, filled with the next amount of slag mixture to be processed, and then returned to the apparatus ready for the medium to agitation again be moved and descended towards this crucible. This sequential mode of operation is particularly advantageous since it minimizes the dead time where the stirring means is not in operation. In a further aspect, the present invention is an apparatus for separating molten aluminum from a mixture of molten aluminum and aluminum slag, comprising: a table for supporting an insulated crucible containing the mixture of molten aluminum and aluminum slag; at least one ultrasonic transducer, electric vibrator or mechanical vibrator, adapted to vibrate the table either directly or indirectly; a frame adapted to support a blade means or stirring means, the rotation means for the blade means and the means for relatively lowering the same inside the mixture in the crucible, to stir the mixture with the blade means, making possible the simultaneous vibration of the crucible and the agitation of the mixture. According to a further aspect, the present invention comprises an insulated crucible capable of containing a mixture of molten aluminum and aluminum slag, and a drainage pan which is placed immediately below or adjacent, and is removably attachable to the crucible, being adapted the drain pan to receive the molten aluminum flowing through at least one sealable drainage hole in the crucible. One or more drainage holes in the crucible are preferably sealable by a sealing means, which is mounted on the crucible and is movable inside or outside the sealing coupling with its respective drainage orifice, as desired. In a further aspect, the invention involves a method for separating molten aluminum from a mixture of aluminum and aluminum slag, comprising the steps of: removing the mixture from a furnace containing molten aluminum; the transfer of the hot slag to an isolated crucible; the transfer of the crucible to a table medium; the insertion of a pallet means into the mixture in the crucible; the relative descent of a sieve means such that it substantially surrounds the crucible; the agitation of the mixture with the paddle means and the simultaneous vibration of the table and the crucible, to cause the oxide film on the aluminum droplets to break, and cause the aluminum droplets to coalesce, such that the droplets they enlarge in volume and weight and tend to melt towards the bottom of the crucible; and the removal of aluminum from the bottom of the crucible. In still another aspect, the invention involves a method for separating the molten aluminum from a mixture of aluminum and aluminum slag, comprising the steps of: removing the mixture from a furnace containing the molten aluminum; the transfer of the hot slag to an isolated crucible; the transfer of the crucible to a table medium; the insertion of a pallet means into the mixture in the crucible; stirring the mixture with the paddle means and simultaneously vibrating the table and the crucible using at least one ultrasonic transducer, electric vibrator, mechanical vibrator or a combination of one, two or all to cause the oxide film on the droplets of aluminum in the slag are broken, and cause the aluminum droplets to coalesce, such that the droplets enlarge in volume and weight and tend to sink towards the bottom of the crucible; and the removal of aluminum from the bottom of the crucible. The pure aluminum can then be either cast as an ingot or recycled directly to the furnace containing the molten aluminum, or drained to a crucible. The process is carried out without substantially cooling the slag, preferably at a temperature of about 750 ° C. In a further aspect, the invention provides an apparatus for separating molten aluminum from a mixture of molten aluminum and aluminum slag, which includes: a table for supporting an insulated crucible containing the mixture of molten aluminum and aluminum slag; at least one heating means such as a gas burner or the like, adapted either to preheat the blades or to heat the contents of the crucible or to heat both, a frame adapted to support a paddle means or the agitating means, the medium to rotate the pallet means and the means for relatively lowering thereof within the mixture in the crucible, to agitate the mixture with the pallet means, making possible the simultaneous vibration of the crucible and the agitation of the mixture. Gas burners or the like can be used to keep the heat in the contents of the crucible during the stirring process. In contrast to prior art devices, such as slag presses that maintain heat during the separation process, it has been found to be desirable.

BRIEF DESCRIPTION OF THE DRAWINGS By way of example only, the preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic and simplified illustration of the present invention; Figure 2 is a detailed drawing of the apparatus exemplifying the present invention; Figure 3 is a detailed drawing of the apparatus described in Figure 2, but with additional features; Figure 4 is a cross-sectional view of another embodiment of a crucible for use in the present apparatus; Figure 5 is another view of the crucible of Figure 4 / Figure 6 is a simplified plan view of the crucible of Figure 4; Figure 7 is a side view of a variation on the separation apparatus shown in Figure 2; and Figure 8 is a drawing of a bucket with a lid.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY With reference to the drawings, Figure 1 shows a hoist 10 carrying a crucible containing the slag at a temperature of approximately 750 ° C to an apparatus, generally indicated at 14, to remove the aluminum from the slag. The crucible is placed on the table 16 of the apparatus. The blades 18 are lowered into the molten slag, the table 16 is vibrated in a vertical direction, as illustrated by the arrows AA, the blades 18 rotate in the molten slag, and by virtue of that agitation and vibration, the aluminum droplets and the particles in the slag coalesce to form larger droplets and gradually join to the base of the crucible. The aluminum can then be drained out to a hub 20 and transferred either directly to the furnace or used to produce an aluminum ingot 22. Figure 2 shows a more detailed drawing of the apparatus of the present invention. The device includes a frame comprised of a number of vertical pillars or rails 50, a base 52 and a transverse beam 54. In the plan view, the frame includes four pillars placed on the corners of a square. A table 54 is mounted on the plump pillars 56 that rise from the base 52. A number of springs 58 also extend between the base 52 and the table 54. On the top of the table is located a crucible 59. The crucible It can be generally square or circular in plan view, and has sides that taper outward. The inner part of the base of the crucible is shaped like a pyramid, so that there are no sharp corners, so that the slag can be agitated properly and so that the crucible can be easily cleaned. A tube or channel 60 is formed in the base of the crucible which, when unblocked, allows the molten metal to flow outwardly from the crucible. The crucible is made of a refractory material, which has an outer metal film and an insulating layer placed between the film and the refractory material. Although the refractory material has insulating properties, the additional layer helps to prevent the slag from cooling as it is transported to the table. A shaft 62 protrudes from the transverse beam 54 and on the lower end of the shaft there are a series of blades or paddles 64 for stirring the contents of the crucible. The shaft is movable relative to the transverse beam in the vertical direction to raise and lower the blades 64. A motor is also provided on the shaft to rotate the shaft in the B direction to thereby stir the contents of the crucible by means of the blades 64. While not described, it can be considered that each of the blades 64 could be smaller than described, with the shaft 62 adapted to rotate about its own axis and that of the crucible 59 Other agitation arrangements for the blades 64 such as described above could also be easily considered. In use, the slag is taken from the furnace and placed directly in a crucible 59, and the crucible is moved by a forklift or the like, and placed directly on the table 54. Once the crucible is in place on the table, the blades are descended towards the slag. The table on which the crucible sits is then vibrated in the vertical direction, at a rate of between 500 to 5,000 or more vibrations per minute. In the embodiment described in Figure 2, the vibration of the table is achieved through the use of electric vibrators 70 mounted under the table 54. In other embodiments, the vibration can be achieved through the use of one or more ultrasonic transducers, mechanical vibrators, or a combination of such vibrators mounted to the table 54. It is also possible to mount the electric vibrators on the sides of the crucible or the frame to provide horizontal vibration in addition to, or instead of, the vertical vibrations. In normal operation, the blades 64 rotate at a speed between 3 to 40 revolutions per minute. The vibrations break the oxide layer surrounding the aluminum droplets in the slag and allow the metal droplets to coalesce with the result that the droplets then become larger in volume and tend to sink to the bottom of the crucible., where these can flow through the orifice 60 into another draining bucket or pan. As shown in Figure 9, the other drain bucket 20a may have a cover 80 having an inlet 82 to allow the aluminum to drain into the bucket in a safe manner. The speed of vibration can change during the process and tends to start more slowly and then increase later for better results. High vibrational speeds are used to join very small drops of liquid metal together, and by using higher vibrational speeds a higher percentage of pure metal can be recovered. As discussed above, in general, the content of pure metal in the slag from aluminum furnaces is usually between 30 to 60%, and once the process described above has been carried out on the slag, the aluminum content Remaining in the slag tends to be in the range of 3 to 5%. Agitation and vibration are necessary. The specific embodiment described above refers to the vibration of the crucible on a generally vertical axis, and general horizontal agitation, agitation and vibration can take place on other axes and by other methods. The important feature of the invention is that sufficient agitation, vibration, or rotational movement occurs at speeds that cause the aluminum droplets to coalesce. In a further embodiment of the invention as described in Figure 3, the walls 71 are shown mounted to the frame 50 of the apparatus 14. The walls are a multi-layer structure comprising an inner metallic layer and an outer metallic layer. The walls 71 serve to prevent heat, dust, flame and explosion from escaping into the vicinity of the crucible and endangering the workers working nearby. The walls 71 also serve to retard the rate of fall of the temperature of the crucible and its contents during the operation of the apparatus. Placed on one side of the apparatus is an opening 72 provided by a door that can be raised or lowered as desired. In the described embodiment, the door is not visible, since it has been retracted below the top wall 71. The opening is of sufficient size to allow the hoist to insert the crucible into the apparatus. In Figure 3, the device is described just after the crucible has been placed on the table 54, and with the blades 64 lowered into the crucible ready to stir the contents of the crucible. In normal operation, it could be anticipated that the door could be left open for as short a period of time as possible. Accordingly, in normal operation, it could be expected that the opening 72 could be closed by the door immediately after the crucible is placed on the table or as the blades 64 are lowered into the crucible. An alternative crucible to that described in Figures 1 to 3 but which could be used in the apparatus and process described herein, is generally described as 75 in Figures 4 to 6. In this embodiment, the crucible 75 has a copper of drainage 76 placed immediately below and removably coupled to the bottom surface of the crucible 75. Located on the bottom surface of the crucible are a plurality of drainage holes 77 through which the aluminum can be drained into the drainage basin 76, in the use. The drainage basin 76 is particularly advantageous for those smelters that have a high proportion of metal to slag in the slag mixture. In some cases, the higher proportion of aluminum can lead to the solidification of the aluminum near the top of the mix before the agitation and vibration cycle is completed. By providing the drainage holes 77, the aluminum falling to the bottom of the crucible 75 can be drained from the crucible 75., whereby the level of slag mixture in the crucible is lowered, and thus reduces the probability that the aluminum in the remaining mixture will solidify before the end of the cycle. Figure 7 shows a variant of the apparatus shown in Figures 2 and 3 having a number of additional features. First a bell 83 is provided and the exhaust pipe 84 is also provided to allow the safe removal of the powder and / or gaseous product from the process. A bagging system 86 for capturing the dust that passes through the exhaust pipe is also provided, so that the gases leaving the outlet of the tube 88 are clean. Figure 7 also illustrates the provision of two gas burners 88 and 90. The gas burner 88 is used to preheat the blades and the burner 90 can be used to heat the surface of the contents of the crucible, to help prevent solidification of aluminum. An additional feature is the provision of a weighing means such as electronic scales adapted to weigh the crucible and contents, and transmit that information to a computer control unit 94. The control unit also receives the input signals from the sensors 96 associated with the paddle drive means that measure the force required to rotate the paddles. From this information, the control means can determine the optimum agitation time and feed the control signals to a control box 94, which controls the speed and duration of agitation. The control means can also be used to control the sequence and the speed of the vibrations.

Although the above process has been described as being used with aluminum, it may be possible to employ the process in other processes that have metals with properties similar to aluminum. It will be appreciated by persons of skill in the art that numerous variations and / or modifications to the invention may be made as shown in the specific embodiments, without departing from the spirit and scope of the invention, as is amply described. Therefore, the present modalities have to be considered in all aspects as illustrative and not as restrictive.

Claims (40)

1. An apparatus for separating molten aluminum from a mixture of molten aluminum and aluminum slag, including: a table for supporting an insulated crucible, containing the mixture of molten aluminum and aluminum slag, the mixture is adapted to vibrate, to vibrate to the crucible; a frame or structure adapted to support a pallet means or agitating means, the means for rotating the pallet means and the means for relatively lowering the same towards the mixture in the crucible, for stirring the mixture with the pallet means , making possible the simultaneous vibration of the crucible and the fixation of the mixture; and a sieving means capable of substantially surrounding the crucible when it is supported by the table, the sieve means has at least a portion thereof movable between at least a first retracted position to allow access to the crucible, and at least a second position where it prevents access to the crucible.

2. An apparatus according to claim 1, wherein the sieving means is movably mounted to the frame.

3. An apparatus according to claim 2, wherein the movable portion comprises a door that is retractable to allow access to the table of the apparatus, to provide a portal for access to the table.

4. An apparatus according to claim 3, wherein the table is slidably movable relative to the rest of the screening means.

5. An apparatus according to claim 1, wherein the door is pivotally mounted to the wall.

6. An apparatus according to claim 1, wherein the complete sieving means can be movable between the first retracted position and the second position, and wherein the selection means extends downwardly from the descent means for the medium of pallet, and is thus movable in relation to the table and the crucible, in unison with the operation of the means of descent.

7. An apparatus according to any of the preceding claims, wherein the screening means is adapted to prevent or at least improve the escape of heat from the vicinity of the crucible.

8. An apparatus according to claim 7, wherein the screening means is formed from a multilayer structure, comprising at least an inner layer and an outer layer.

9. An apparatus according to claim 8, wherein the inner layer and the outer layer are made of metal or a refractory material.

10. An apparatus according to any preceding claim, wherein the paddle or agitation means comprises a plurality of blades mounted on an axle supported by a frame, the axle is adapted to be raised or lowered so that the blades can be raised when a New crucible is placed on the table located below the blades.

11. An apparatus according to claim 10, wherein, in use, the shaft is positioned at or near the center of the crucible, and is rotatable by a rotary means about its longitudinal axis.

12. An apparatus according to claim 10, wherein, in use, the shaft is radially displaced from the center of the crucible and is, in addition to rotating about its longitudinal axis, also rotated by the rotary means about the center of the crucible.

13. An apparatus according to claim 11 or 12, wherein a gear is provided such that the shaft undergoes a planetary movement as it is rotated by the rotary means around the center of the crucible.

14. An apparatus according to any preceding claim, wherein the crucible is made of a refractory material having a metallic outer film spaced from the refractory material by an insulating layer.

15. An apparatus according to claim 14, wherein the crucible is provided with a covering means at least partially covering the upper opening of the crucible, which cover is retractable or otherwise removable from the crucible when the vane or stirring means It is relatively lowered inside the crucible.

16. An apparatus according to claim 15, wherein the cover is positioned or adapted to surround the axis of the vane or stirring means while the vane or stirring means is rotating the contents of the crucible.

17. An apparatus according to any preceding claim, wherein a drainage pan adapted to be placed directly below the crucible is also included.

18. An apparatus according to claim 17, wherein the drainage basin is engageable with the crucible and movable so, if desired, with the crucible when the crucible is moved in and out of the apparatus.

19. An apparatus according to claim 17 or 18, wherein the crucible has one or more drainage holes in or adjacent to its bottom surface and in fluid communication with the drainage basin, so that the aluminum can be drained to the copper. of drained.

20. An apparatus according to claim 19, wherein one or more of the drainage holes which are in fluid communication with the draining basin are sealable by a sealing means mounted to the crucible, and are movable in or out of sealing coupling. with its respective drainage hole, as desired ..

21. An apparatus according to any preceding claim, wherein the table is mounted on springs to assist in the release of the crucible.

22. An apparatus according to any preceding claim, wherein the vibration of the table and the crucible is caused by the assembly of at least one ultrasonic transducer, electric vibrator, mechanical vibrator or a combination of one or more of these transducers to the crucible and / or to the table, arranged to vibrate the table such that it oscillates on a horizontal axis, a vertical axis or both axes.

23. An apparatus according to any preceding claim, wherein the frame includes two or more vertical pillars and a transverse beam supported by the frame, and wherein the transverse beam carries the rotating means and the axis for the blades is hung down from the beam transverse, with the blades mounted on the lower end of that axis.

24. An apparatus according to any preceding claim, which includes one or more exhaust pipes that allow the gaseous product from the process carried out by the apparatus to be vented to the atmosphere outside the screening medium.

25. An apparatus according to claim 24, wherein the exhaust pipes incorporate bagging systems that collect the gaseous exhaust product for subsequent disposal.

26. An apparatus according to claim 24 or 25, wherein the bagging systems extract the powder from the gaseous product.

27. An apparatus according to claims 24, 25 or 26, wherein the exhaust systems also include filtering or purifying means for cleaning or substantially cleaning the gaseous product from the process, from the hazardous or potentially hazardous constituents.

28. An apparatus according to any preceding claim, further including a weighing means, such as an electronic or mechanical balance for measuring the weight of the crucible and its contents while the crucible is seated on the table.

29. An apparatus according to any preceding claim, further comprising a control means adapted to allow an operator to operate all the characteristics of the apparatus from a central position, such that the apparatus normally runs without the participation of the operator.

30. An apparatus according to claim 28, further including a control means and the sensor means for detecting the pressure on the blades, the control means is arranged to determine the optimum agitation time and the optimum vibration sequence and speed at from the measurements of the pressure on the blades and / or the weight of the crucible and the contents.

31. An apparatus according to any preceding claim, which includes an additional drain pan that is adapted to receive aluminum at the termination of each cycle of operation of the apparatus having a cover, an inlet gate, enclosing the drain pan.

32. An apparatus according to any preceding claim, wherein the apparatus comprises two or more tables that are arranged to receive more than one crucible at one time, so that the contents of one crucible can be stirred and vibrated while the other crucible is being filled with the slag mixture, and placed in the apparatus, the stirring medium is movable from a crucible to the next crucible at the end of the separation process.

33. An apparatus for separating molten aluminum from a mixture of molten aluminum and aluminum slag, including: a table for supporting an insulated crucible containing the mixture of molten aluminum and aluminum slag; at least one electric vibrator, mechanical vibrator or ultrasonic transducer, adapted to vibrate the table either directly or indirectly; a frame adapted to support a paddle means or stirring means, the means for rotating the paddle means and the means for relatively lowering the same inside the mix in the pot, to stir the mix with the paddle means, making possible the simultaneous vibration of the crucible and the agitation of the mixture.

34. An insulated crucible for use with an apparatus according to any of claims 1 to 33, the crucible is adapted to contain a mixture of molten aluminum and aluminum slag, and which includes a sealable drainage orifice and a drainage basin placed immediately below, which is removably engageable in the crucible, the drainage basin is adapted to receive the molten aluminum flowing through at least one sealable drainage hole in the crucible.

35. An insulated crucible according to claim 34, wherein one or more drainage holes in the crucible are sealable by a sealing means that is mounted on the crucible, and is movable inside or outside of sealing coupling with its respective orifice. Drained

36. A method for separating molten aluminum from a mixture of aluminum and aluminum slag, comprising the steps of: removing the mixture from a furnace containing molten aluminum; the transfer of the hot slag to an isolated crucible; the transfer of the crucible to a table medium; the insertion of a pallet means into the mixture in the crucible; the relative descent of a sieve means such that it substantially surrounds the crucible; the agitation of the mixture with the paddle means and the simultaneous vibration of the table and the crucible, to cause the oxide film on the aluminum droplets to break, and cause the aluminum droplets to coalesce, such that the droplets they enlarge in volume and weight and tend to melt towards the bottom of the crucible; and the removal of aluminum from the bottom of the crucible.

37. A method for separating the molten aluminum from a mixture of aluminum and aluminum slag, comprising the steps of: removing the mixture from a furnace containing the molten aluminum; the transfer of the hot slag to an isolated crucible; the transfer of the crucible to a table medium; the insertion of a pallet means into the mixture in the crucible; stirring the mixture with the paddle means and simultaneously vibrating the table and the crucible using at least one ultrasonic transducer, electric vibrator, mechanical vibrator or a combination of one, two or all to cause the oxide film on the droplets of aluminum in the slag are broken, and cause the aluminum droplets to coalesce, such that the droplets enlarge in volume and weight and tend to sink towards the bottom of the crucible; and the removal of aluminum from the bottom of the crucible.

38. A method according to claim 37, wherein the method is carried out without substantial cooling of the slag, preferably at a temperature of about 750 ° C.

39. An apparatus for separating molten aluminum from a mixture of molten aluminum and aluminum slag, which includes: a table for supporting an insulated crucible containing the mixture of molten aluminum and aluminum slag; at least one heating means such as a gas burner or the like, adapted either to preheat the blades or to heat the contents of the crucible or to heat both; a frame adapted to support a paddle means or the stirring means, the means for rotating the paddle means and the means for relatively lowering the same inside the mix in the pot, for stirring the mix with the pallet means , making possible the simultaneous vibration of the crucible and the agitation of the mixture.

40. An apparatus for separating molten aluminum from a mixture of molten aluminum and aluminum slag which includes: a table for supporting an insulated crucible containing the mixture of molten aluminum and aluminum slag; a means of weighing, such as an electronic or mechanical balance to measure the weight of the crucible and its contents, while the crucible is seated on the table; a frame adapted to support a paddle means or stirring means, the means for rotating the paddle means and the means for relatively lowering the same inside the mix in the pot, to stir the mix with the paddle means, making possible the simultaneous vibration of the crucible and the stirring of the mixture; a sensor means for detecting the pressure on the paddles during agitation; and an accommodating control means for determining the optimum agitation time and optionally the sequence and speed of the vibrations, the pressure measurements on the blades and / or the weight of the crucible and the contents. SUMMARY OF THE INVENTION An apparatus (14) for separating molten aluminum from a mixture of molten aluminum and aluminum slag is described, which includes a table (16, 54) for supporting an insulated crucible (59, 75) containing the mixture of molten aluminum and slag of aluminum. Electric, mechanical or ultrasonic vibrators (70) or the like are provided to vibrate the table and the crucible (59, 75). A frame (50, 52, 54) supports a rotating vane (18, 64), which can be lowered into the mixture in the crucible (59, 75) to agitate the mixture, making possible the simultaneous vibration of the crucible (59, 52, 54). , 75) and the agitation of the mixture. By virtue of that agitation and vibration, the aluminum droplets and the particles of the slag coalesce to form larger droplets and gradually sink towards the base of the crucible (59, 75). The aluminum can then be drained out to a bucket or bucket (20, 20a, 76). A screening means is positioned to substantially surround the crucible (59, 75) when it is supported by the table (16, 54). The sieving means includes a door (72) to allow access to the crucible (59, 75) in one position, and in a second position prevents access to the crucible (59, 75). A bell (80, 83) is provided in the upper part of the apparatus (14), so that the crucible (59, 75) is substantially completely enclosed. Gas burners (88, 90) can be used to retain heat in the crucible (59, 75) and the contents.