GB2126252A - Method of segregating metallic components from composite scrap - Google Patents

Abstract

A method of segregating metallic components fabricated from different aluminum wrought alloys comprises the steps of providing a feedstock such as used aluminum containers having at least two components thereon comprised or different aluminum alloys and heating the feedstock to a temperature sufficient to increase the fracture sensitivity of at least one of the components. Preferably the temperature is sufficiently high to initiate incipient melting of the component having the lowest incipient melting temperature. While at the lowest incipient melting temperature of the aluminum alloy component, the feedstock is subjected to agitation sufficient to cause the aluminum alloy component having the lowest incipient melting temperature to fragment and, when part of an article, to detach itself from the article. Thereafter, the fragmented or detached components are segregated from the remaining components or articles and may be recovered.

Description

SPECIFICATION Method of segregating metallic components This invention relates to used containers fabricated at least in part from different metals or alloys, and more particularly, this invention relates to a method or process for reclamation of used containers, such as beverage containers, in a manner which permits recovery or segregation of container components substantially in accordance with their compositions, for example, or composition types.

In the packaging or container field such as the used beverage containers having at least one or more components thereof fabricated from aluminum alloys, there has been ever-increasing interest and extensive research into methods of reclaiming the aluminum components. The interest has been precipitated by the importance of conserving resources and caring for environmental problems.

However, heretofore recycling such materials has been greatly hampered by the lack of a method which would be economically attractive. For example, attempts to recycle a beverage can having a body fabricated from one aluminum alloy and a top or lid constructed from a different aluminum alloy often results in an aluminum melt having the composition of neither alloy. Such melt greatly decreases in value because it does not readily lend itself to reuse in the can body or lid without major dilutions, purifications and realloying or other modifications. That is, it can be seen that there is a great need for a method of recycling containers of the type, for example, described wherein the different components thereof are recovered and segregated according to alloy or according to alloy type.

The problem of segregation of different alloys is recognized in U.S. Patent 3,736,896, where there is disclosed the separating of aluminum alloy tops or lids from steel bodied cans by melting a small band of aluminum around the periphery of the can body to provide a separating area allowing separation of the aluminum end from the steel cylindrical body. In this disclosure, induction heating is used to melt the band wherein an encircling inductor surrounds a bead and is connected to a high frequency power supply. However, this approach seems to presume that a used beverage can is not crushed and the end remains perfectly circular. Further, to melt the ends off in this manner would not seem to be economical since the ends would have to be removed individually.

In U.S. Patent 4,016,003, containers having aluminum alloy bodies and lids are shredded to particles in the range of 25.4 to 38.1 mm (1 to 12 inch) and then subjected to temperatures of around 371.1 OC (7000 F) to remove paints and lacquers. In addition, U.S. Patent 4,269,632 indicates that since the conventional alloys for can ends, e.g. Aluminum Association (AA alloy) 5182, 5082 or 5052, and for can bodies, e.g. AA3004 or AA3003, differ significantly in composition, and in the manufactured can, the end and body are essentially inseparable and that an economical recycle system requires the use of the entire can. U.S. Patent 4,269,632 further notes that the recycling of cans results in a melt composition which differs significantly from the compositions of both the conventional can end and can body alloys.In this patent, it is suggested that both can end and body be fabricated from the same alloy to obviate the recycling problem. With respect to can ends and bodies made from AA5182 and 3004, it is indicated that normally pure aluminum must be added regardless of the alloy prepared.

In view of these problems with recycling metal containers, such as aluminum beverage containers having components thereof comprised of different alloys, it would be advantageous to have a method which would permit recovery of the containers by segregating the components there of according to their alloys or segregating the components according to their alloy type. That is, by segregation of the components prior to melting, the components can be melted and refabricated in accordance with normal procedures without, inter alia, expensive dilutions or purification steps.

According to the present invention there is provided a method of segregating metallic components fabricated from different aluminum wrought alloys, the method comprising the steps of: (a) providing a feedstock containing at least two types of components thereof according to different aluminum wrought alloys having different incipient melting temperatures; (b) heating the feedstock to a temperature sufficient to substantially increase the fracture sensitivity of at least one of said components to a level sufficient to cause fragmentation of at least one of said components upon agitation of the heated feedstock; (c) subjecting said heated feedstock to agitation sufficient to cause at least one of said components to fragment; and (d) segregating said fragmented components from the remaining feedstock.

In accordance with the present invention there is also disclosed a method of detaching and segregating metallic components secured to metallic articles, the segregation being made in accordance with alloy composition of the components. The method comprises the steps of providing articles having at least two components thereon comprised of different aluminum alloys and heating the articles to a temperature sufficiently high to initiate incipient melting of the component having the lowest incipient melting temperature. While the articles are held at the lowest incipient melting temperature of said aluminum alloy components, they are subjected to agitation sufficient to cause the aluminum alloy component having the lowest incipient melting temperature to fracture and detach itself from the article.

Thereafter, the fractured and detached components are segregated from the articles and recovered.

In the accompanying drawings: Figure 1 is a flow sheet illustrating steps which can be used in classifying containers, such as used beverage containers.

Figure 2 is a bar graph showing the particle size distribution of material entering and exiting the furnace at a temperature of 571.1 0C (1 0600F).

Figure 3 is a bar graph showing the particle size distribution of material entering and exiting the furnace at a temperature of 582.20C (10800F).

Figure 4 is a bar graph showing the particle size distribution of material entering and exiting the furnace at a temperature of 593.30C (1 1000F).

Figure 5 is a bar graph showing the particle size distribution of material entering and exiting the furnace at a temperature of 604.40C (1 1200F).

Figure 6 is a flow sheet illustrating steps which can be used in classifying containers, and removing tramp impurities therefrom in accordance with the invention.

Figure 7 is a flow sheet illustrating steps which can be used in removing fines in a process for recycling used aluminum containers.

Referring to the Fig. 1 flow sheet, used articles from which the aluminum alloy components are to be recovered or reclaimed may comprise containers such as food and beverage containers. Containers to which the process is suited are used beverage containers comprised of two different aluminum alloys.

From the flow sheet, it will be noted that the articles to be recovered may be subjected to preliminary sorting to remove materials which would contaminate the aluminum alloy to be recovered. For example, it would be desirable to remove glass bottles and steel cans such as used for food, for example. Further, it is desirable to remove other materials such as dirt and sand, etc., in order to cut down on the amount of silicon, for example, that can occur in the reclaimed alloy. Elimination of these materials can permit use of the alloy reclaimed in accordance with the present invention without further purification procedures. The removal of steel preliminarily, as may be present in the form of containers or cans or other sources, aids in keeping the iron in the reclaimed alloy to a level which does not adversely affect the reclaimed alloy properties.

When the material to be reclaimed are food or beverage containers, these are normally packaged in bales for shipping purposes and, therefore, prior to the sorting step, the bales would normally be broken apart to remove the foreign materials.

After the sorting step, the containers can be subjected to a delacquering step. This may be accomplished by solvent or thermal treatments. The delacquering removes the coatings, such as decorative and protective coatings, which can contain elements such as titanium which in high levels is not normally desirable in the aluminum alloys being reclaimed. When solvent delacquering is used, it is usually desirable to shread or pierce the containers in order to permit the solvent to drain therefrom.

When the coatings are removed by thermal treatments, the temperature used is normally in the range of 31 5.6C to 537.80C (600 to 1 0000 F).

In the next step of the process, particularly where the containers are used beverage containers having bodies formed from Aluminum Associated alloy (AA) 3004 and having lids formed from AA5182, for example, the containers are heated to a temperature at which the AA5812 lid becomes fracture sensitive. This temperature has been found to correlate closely with the incipient melting or grain boundary melting temperature of the alloy.

Thus, in reference to used beverage containers, this is the incipient melting temperature of AA5182. By the use of incipient melting or grain boundary melting temperature herein is meant the lower temperatures of the melting range or phase melting range and slightly below at which the alloy develops or significantly increases in fracture sensitivity or at which fragmentation of the alloy can be made to occur without the use of great force. That is, in the fracture sensitive condition, fragmentation can be made to occur by the use of a tumbling action or falling action, and the use of forces such as would be obtained by a hammer mill or jaw crushers are not required. Forces such as encountered with a hammer mill or jaw crusher are detrimental to the instant process since they act to crush the containers, for example, thereby trapping material to be separated.It will be appreciated that many alloys have different incipient melting temperatures. For example, AA3004 has an incipient melting temperature of about 629.50C (11 650F) and AA5182 has an incipient melting temperature of about 580.60C (1 0770F) and has a phase melting range of about 580.6 to 636.7 OC (1 077 OF to 11 780F).

However, it will be appreciated that this range can vary depending to a large extent on the exact composition of the alloy used. Incipient or grain boundary melting of the alloy greatly reduces its strength and sets up the fracture condition. Thus, the AA5182 lids can be detached or removed from the AA3004 bodies because of the lids being provided in a condition which makes it highly sensitive to fracture and fragmentation. While in this condition, energy, e.g. tumbling action, can be applied for purposes of detaching or removing the lid from the can body. The detaching results primarily from the lid fracturing or fragmenting to provide lid particles which are not only smaller than the can body but generally smaller than a lid.

Thus, after the detaching step, there results a charge or mass comprised of can bodies and fragmented lids, the can bodies being comprised of an alloy or material different from the fragmented lids, the fragmented lids having a particle size distribution substantially different from the can bodies.

Thus, it can be seen that not only is it important to remove the lid from the can body, but the lid fragments must have a particle size which is substantially different from the can body. For purposes of obtaining a product or alloy which is not adversely contaminated with the alloy with which it is commingled, the charge is subjected to a treatment for purposes of classifying or segregating the particles. When this aspect of the process is carried out, the result is lid fragments or values comprised of substantially the same alloys which are segregated from the can bodies.

While the process has been described in general terms with respect to reclamation of used beverage cans, it should be understood that the feedstock for the process is not necessarily limited thereto. That is the process is capable of classifying aluminum alloys, particularly wrought alloys, where one of the alloys can be made fracture sensitive or put in a condition where one of the alloys can be fragmented preferentially in order to obtain a particle size distribution which is different from the particle sizes of the other alloys. In this way, a partition of the alloys can be made. Thus, for example, the feed stock for reclamation may be comprised of used beverage containers having bodies fabricated from AA3004 and lids fabricated from At51 82. Other alloys which may be used for lids include AA5082, 5052 and 5042 (Table X).However, other alloys.which may be used for food or beverage can bodies includes alloys such as AA3003, AA3104, AA5042 and AA5052 (Table IX). If such alloys are high in magnesium, for example, it is required that such can bodies be fractured or fragmented sufficiently to enable them to be classified with the lid alloys, such as AA5182. Thus, it will be understood that the process of the present invention is not only capable of removing and classifying lids from can bodies, as noted herein, but it is also capable of classifying the alloys in the can bodies with the lids when the alloys are of similar composition and which respond in a similar manner with respect to fracture or fragmentation characteristics, as explained herein.

In addition, where the containers have bodies and lids fabricated from the same alloys, that too may be reclaimed by classifying in accordance with the present invention. For example, if can body and lids are fabricated from sheet having the composition 0.1-1.0 wt.% Si, 0.01-0.9 wt.% Fe, 0.05-0.4 wt.% Cu, 0.4-1.0 wt.% Mn, 1.3-2.5 wt.% Mg and 0--0.2 wt.% Ti, the remainder being aluminum and incidental impurities, this would be classified in accordance with the invention.That is, if the feed stock to be reclaimed comprises used containers fabricated from mixed alloys such as 3004, 5182, 5042, as well as the can body and lid alloy above, this alloy would be expected to be classified with the AA3004 body stock because no incipient melting would occur when the temperature was sufficiently high to cause fracture of At51 82 or AA5042.

Likewise, if steel containers having 5182 lid attached thereto are present in the feedstock, the lids can be classified in accordance with the invention and the steel bodies would be recovered with 3004 can bodies. The steel container bodies can be separated from the aluminum alloys with which they may be classified by magnetic separation means, for example, after the lids have been removed. If the steel bodied containers had lids which fractured at temperatures in the AA3004 incipient melting range, then it would be necessary to heat the containers to a higher temperature as compared to AA5182 to effect a separation of the lid from the steel body after which the steel bodies could be removed by magnetic separation, for example.

From the above, it will be seen that the process of the present invention is rather insensitive to the aluminum feedstock being recovered. That is, the process is capable of handling most types of aluminum alloys and is particularly suited to recovering and classifying wrought alloy products such as is encountered in used containers. If the scrap were comprised of aluminum alloys used in automobiles, for example, AA6009 and AA6010, as described in US. Patent 4,082,578, where the use can be hoods and doors, etc., it may be desirable to subject such articles to a shredding action to provide a generally flowable mass. Or in recovering AA2036 and AA5182 from used automobiles, it may be desirable to shred such products and then effect a separation, as noted herein.

With respect to grain boundary melting or incipient melting of one of the aluminum alloy components to effect fracture sensitivity or fragmentation, it will be understood that this is an important step of the process and must be carried out with a certain amount of care. Using the used beverage cans as an example again, it will be noted that temperature control is important in this step. That is, if the temperature is permitted to get too high, substantial melting of the At51 82 lid can occur, which can result in losses with respect to aluminum and magnesium because of oxidation. Temperatures which bring about substantial melting of the metal normally should be avoided for the additional reason that it can result in coagulation of particles with molten aluminum to form a mass which is not readily flowable when compared to finer discrete particles.Further, molten aluminum can stick to the furnace and start building a layer of metal and particles therein which, of course, interferes with the efficiencies of the whole operation. Also, classification of the congealed mass becomes much more difficult, it not impossible. Lastly, on melting, fines such as sand, glass, dirt and pigments or contaminants such as silicon oxide, titanium oxide and iron oxide tend to become embedded in the molten metal, further making separation thereof difficult. Thus, in view of the above, it can be seen why temperatures which result in substantial melting of one of the aluminum alloy components should be avoided.

Likewise, when temperatures are employed which are too low, the fracture sensitivity of the lids drop dramatically and resistance to fragmentation increases substantially with the result that separation becomes extremely difficult and often segregation cannot be effected. Accordingly, it will be seen that it is important to have the temperature sufficiently high in order to remove the lid from the can body. For lids formed from AA5182, this temperature correlates to about the incipient melting temperature which is about 5800C (1 O770F).The melting range for AA5 182 is about 580.6 to 636.70C (1077 to 11 780F). Thus, if the used beverage containers are heated to 593.30C (11 000F), this is well below the melting range of AA3004, about 629.5 to 654.40C (1 165-121O0F),and the the lids can be detached or removed without fracturing the can bodies.

With respect to grain boundary or incipient melting, it will be understood that because the sheet from which the lids are fabricated has been rolled to a thin gauge, grains are not well defined. However, it is believed that recrystallization occurs when the used beverage containers are heated, for example, to remove lacquer, which can occur at 454.50C (850by), for example, Thus, grain boundary melting can occur.

When the used beverage containers were heated to about or slightly above 593.30C (1 1000F), generally it was found that the At51 82 ends sagged or slumped on the AA3004 can body. However, when the containers were agitated at about this temperature by permitting them to drop from a conveyor belt, for example, the lids were found to detach themselves from the can bodies and were divided or fragmented in small particles while the can bodies were relatively unchanged.Agitation sufficient to detach the ends also may be effected in a rotary furnace or kiln while the used cans are heated to a temperature in the range of 580.6 to about 623.90C (1077 to about 11 550F), with a preferred range being 580.6 to 610.00C (1077 to 1 1300F) and typically nothigherthan 604.40C (11 200 F). Agitation sufficient to remove the ends in the rotary furnace can be that which occurs at these temperatures when the cans are tumbled inside the furnace. As noted hereinabove, forces such as obtained from hammering or by the use of jaw crushers should not be used because they act to flatten the cans or otherwise entrap the fragmented ends with the can bodies.As noted earlier, operating at temperatures high in the melting range can result in too much liquid metal and the attendant problems therewith. The melting problem becomes particularly acute if the used beverage cans are held for a relatively long time at temperatures high in the melting range. At temperatures in the range of 580.6 to 610.0 C (1077 to 11 3O0F), the time at temperature can range from 30 seconds to less than 10 minutes.

In the classification step, the AA5182 fragments can be separated from whole can bodies or from can bodies which have been shredded by screening. However, it will be appreciated that other methods of separation may be used, all of which are contemplated to be within the purview of the present invention.

In another aspect of the invention as illustrated in Fig. 6, it has been found that contamination, such as clay, sand and glass, associated with used beverage cans, may be effectively removed in accordance with the present invention. That is, for purposes of recycling, it will be appreciated that contaminants, such as clay and sand, etc., can lead to higher levels of constituents, such as silicon in the recovered metal, than are permitted in the composition ranges of the alloy. Thus, in order to bring alloy compositions within specification, purification, substantial dilutions, or some form of realloying, must be made, all of which greatly detract from the economic feasibility of recycling.Accordingly, not only must the alloys of the different components, e.g., beverage cans, be separated according to alloy, but it is imperative that pickup of tramp impurities such as silicon be prevented because this also can result in an alloy which does not meet the specifications.

While reference is made mainly to clay or dirt, it will be understood that these materials can result in contamination in the form of calcium, sodium and silicon. The silicon often shows up in the form of silicon oxide. Other contaminants include iron, lead and oxides of aluminum, magnesium and titanium which often result from oxidation during treatment in the furnace. One source of TiO2 is the coatings on the containers. For purposes of this invention, these impurities are referred to as tramp impurities since they are impurities picked-up during or after usage of the containers and normally do not result from commingling of one alloy with another. However, tramp impurities are not necessarily limited to those impurities mentioned.

It will be appreciated that the addition of high purity aluminum to dilute out impurities, such as silicon, also interferes adversely with the economic feasibility of recycling. This problem is solved in the present invention by concentrating impurities, such as silicon, in a way which permits their removal from the system.

In the recycling of containers such as used beverage and food containers, as noted earlier, it is customary to remove coatings, such as decorative and protective coatings, by heating. Thus, containers can be subjected to temperatures in the range of 315.6 to 537.80C (600 to 10000F), as noted earlier, to remove these coatings. However, while this treatment is suitable for removing coatings, it has the effect of baking clay or dirt on the container. Thus, upon remelting of delacquered scrap, the baked clay or dirt would be ingested in the melt, thus adding to the problems of obtaining a useful alloy. In the present invention, it has been discovered that the fracturing of the end aids in providing smaller particles which act to remove baked materials, such as clay or dirt, from the surface of the containers.It is believed that the removal of such material from the surface is achieved by scouring or scrubbing by the fine lid particles, for example, on the container body. If heating to the fracture sensitive condition is performed in a rotary kiln, the scouring of the smaller particles on the outside of the larger bodies is achieved as the kiln turns. If a conveyor-type furnace is used, the abrading or scouring may be performed when the containers are being agitated to fracture the fracture sensitive material.

It should be noted that not only is it important to remove baked clay or dirt materials from the containers, but the baked materials must be provided in a form which permits its separation from the feed materials. Thus, preferably this is accomplished by grinding the baked clay or dirt into a fine particle size. That is, the baked clay or dirt should be permitted to be ground to a particle size smaller than the smallest particle size of any recyclable components. Thus, for example, when the feedstock being recycled is mainly containers having aluminum alloy bodies and an aluminum alloy lids or ends, e.g., bodies fabricated from AA3004 and lids fabricated from AA5182, normally it is preferred that any contaminants resulting from the baked clay or dirt, be separated from the container bodies with the fractured components.Thereafter, the ground clay or dirt may be separated from the fractured components, e.g., lids. That is, the operation of heating and agitating reduces the baked clay or dirt to a particle size which can be separated from the fractured lids. This separation may be effected by screening. Thus, in a preferred embodiment, the fine particles resulting from the baked clay can be effectively separated from the lids using a +20 mesh screen (U.S. Standard Series), for example, depending to a large extent on the amount of tramp impurities to be removed and balanced against the amount of fine metal particles present. It will be appreciated that other means for separation, e.g., air knife or flotation techniques, may be used and any such separation or the like is contemplated to be within the purview of the invention.

It will be appreciated that in the recovery of alloys, tolerance for elements such as silicon can vary depending on the alloy. For example, in high silicon alloys, silicon may not be considered to be an impurity. Thus, the use of silicon in the present invention is intended by way of example and not by limitation. Thus, in the following exemplary disclosure, reference to silicon is made for purposes of illustration only.

In still another aspect of the invention, as illustrated in Fig. 7, is has been found important to remove metal fines from the process. That is, when it is found desirable to shred the aluminum articles, e.g., used aluminum materials such as used containers, it has been found that shredding results in the generation of a significant amount of fine metal referred to herein as fines. Normally, the generation of such fines would not be considered to be a significant problem. However, when beverage containers are processed to separate the lids from the container bodies, the lids are fragmented as noted herein, and have a size range substantially smaller than the bodies which permit separation therefrom.However, if the used materials, e.g., used beverage containers, are shredded prior to processing for separation purposes, the shredding can result in fines which are in the size range constituting the lid fragments.

The fines generated by shredding, in fact, can be said to contaminate the fragmented portion. For example, if the beverage can is constituted of 75 wt.% AA3004 and 25 wt.% AA51 82, the fines generated on shredding a feedstock comprised of such containers can have 92 wt.% of AA3004 and only 7 wt.% At51 82. Thus, it will be seen that there is a great need to prevent this type of contamination in the present process. Omitting the step of removing the fines results then in the fragmented AA5182 portion being contaminated with AA3004 fines from the can bodies. Thus, it has been found that removing fines in the size range corresponding to the size range of the fragmented portion being separated from the container body portion results in substantially fragmented portions being substantially free of fines.The fines should be removed after the shredding step and before fragmenting step. One method of removing the fines can be the use of screens, although other techniques, such as air separation and the like, are contemplated within the purview of the invention.

When the feedstock used is beverage containers having, for example, AA3004 bodies and AA518 lids, after shredding the fines can constitute 1 to 1 5 wt.% or more of the shredded feedstock.

The following provides an example of the contamination which can result from the fines generated by shredding. From Table X, the composition range for manganese in At51 82 is 0.20 to 0.50 wt.%.

Normally, manufacturers of At51 82 maintain the manganese composition near the middle of this range. For purposes of the following examples, it is to be assumed that manganese concentration of 0.38% is desired.

If the process of shredding and subsequent fragmentation is performed on 1 00 units of used beverage containers, it has been found in one instance that five units of fines generated in the shredding step had a manganese level of 1.10%. These are, therefore, composed almost entirely of AA3004. The fragmentation step produced 20 units ofAA5182 with a manganese level of 0.38%. If these 25 units are not separated but are collected together, then the resulting manganese level can be calculated to be 0.52%. This requires significant dilution to produce metal of 0.38% manganese.

In yet another example, if the process produces a shredded product or feedstock that contains approximately 9 wt.% fines, the manganese level of this material is 1.05 wt.%. If these 9 units were collected in the fragmented portion together with the 20 units of AA51 82, the total 29 units would have a manganese level of 0.59 wt.%. Again, this requires significant dilution with pure aluminum to produce AA5182 having a manganese level of 0.38 wt.%. Thus, if can be seen that it is important to remove the fines prior to their being commingled with the fragmented portion.

The bales of food or beverage containers referred to above may be subjected to a shredding type operation for purposes of breaking them apart. After the shredding operation, the feedstock should be screened for purposes of removing metal fines for purposes set forth in detail hereinbelow. As shown in Figure 7, the fines may be subjected to a delacquering step and then recombined with a compatible fraction of the feedstock in accordance with the invention and eventually melted.

As further illustrative of the invention, used beverage cans having AA3004 bodies and AA5182 lids thereon were processed through a rotary-type kiln. Samples were taken of ingoing and exiting material for the rotary kiln at four different kiln set temperatures, as follows: 571.1 0, 582.20. 593.3" and 604.4"C (10600. 10800, 1 100" and 1120 F). Ingoing samples were taken which weighed about 1 5 kg (35 Ib). Approximately six minutes later, representing the residence time of used beverage cans in the kiln, about 45 kg (100 lb) of exiting material was sampled.

Prior to entering the furnaces, bales of used beverage cans were processed through a shredder. The shredder in the process of partially shredding most of the cans, generates some used beverage can fines. In the figures, the screen analyses of ingoing and exiting material are compared at each kiln set temperature to determine the degree to which end fragmentation occurs inside the kiln. This is recognized as a decrease in weight of the coarser fractions and an increase in weight of the finer fractions.

The U.S. Standard Screen sizes that were used to fractionate the samples are listed inTable 1, together with the Tyler mesh equivalents.

Samples of each size fraction were melted and analyzed to monitor alloy partitioning and also to measure the amount of tramp impurity pickup.

The chemical composition of a sample makes it possible to calculate the relative amount of AA3004 and AA5182 present. This is done by assuming that AA3004 contains 1.10% manganese and that AA5182 contains 0.38% manganese. A melt of used beverage cans having a manganese content of 0.92% can be shown to contain 75% of AA3004 material and 25% of AA5182 material. This calcuiation was done for each exiting fraction at the four kiln temperatures of the test. The amount of At5182 calculated to be present appears as the totally shaded portion on the bar graphs in Figures 2-5.

Figure 2 shows the particle size distribution of ingoing and exiting material while the kiln set temperature was 571.1 OC (1 0600F). The distribution of AA51 82 in the exiting material is also shown.

The recorded temperature during the sampling period ranged from 554.4 to 571.1 0C (1030 to 10600 F). The primary feature in the figure is that very little difference is seen in the size distribution of ingoing and exiting material. It is also shown that the mix of At51 82 and AA3004 in the coarser exiting fractions is approximately 25% and 75%, respectively, which indicates that lid fragmentation did not appear to be occurring at this temperature.

Table II shows the spectrographic analysis of the metal found in each size fraction for both entering and exiting material. Again, ingoing and exiting material for a give size fraction appear to be very similar, except for magnesium.

There does, however, appear to be a variation in composition that is dependent on size fraction which suggests that the crushing step, prior to delacquering, generates more body fines than end fines.

The finer fractions exhibit elevated manganese levels and decreased magnesium levels when compared to the coarser fractions. These finer fractions, therefore, appear to be richer in AA3004 content than the coarser ones. With the can body being thinner and accounting for a larger surface area of the can than the end, it may be expected that in shredding used beverage cans the body would produce more fines than would the end. The decreasing magnesium content with finer particle size may also reflect the increased magnesium oxidation incurred when melting the smaller sized material for analysis purposes.

The -10 mesh material, both ingoing and exiting, did not contain sufficient metallic material to melt and produce a sample for spectrographic analysis.

The data from samples taken while the kiln set temperature was 582.20C and 593.30C (10800F and 11 000F) appear in Figures 3 and 4 and Tables Ill and IV, respectively. These samples show fragmentation of AA51 82 lids inside the rotary kiln. Specifically, the amount of material present in the finer mesh fractions in the exiting material is increased when compared to the ingoing material; and these fines have compositions that show At51 82 enrichment. This trend is more pronounced at 593.30C (1 1O00F) than at 582.20C (10800F).

The samples taken at 604.40C (11 200 F) show the strongest, definitive evidence for AA51 82 fragmentation inside the kiin. The two coarsest fractions have experienced a significant weight reduction after passing through the kiln and the four finer fractions all show a significant weight increase (Figure 5).The compositions of the fractions (Table V) show that the coarser fractions are nearly commercial grade compositions of AA3004 and that the finer material is nearly the commercial grade composition of AA5 182. Comparing data for the 571.1 OC and 604.40C (1 0600F and 11 200F) experiments shows migration of AA51 82 from the coarse fractions to the fine fractions.

Table V shows that metal from the -10 mesh fraction of the 604.40C (11 200 F) sample contains 0.50% silicon. This is very significant since this fraction represents approximately 30% of the AA5182 in the system. This material was further screened down to determine the possibility of screening out the tramp silicon contaminants. The results appear in Table VI. The tramp silicon apparently migrates to the -20 mesh fractions. The -25 mesh fraction contained such a large amount of non-metallic material that it could not be melted to prepare a sample for spectrographic analysis. Visual inspection revealed significant quantities of glass and sand. Chemical analysis of the -25 material appears in Table VII. This fraction contains only about 56% metallic aluminum. The sand and glass content is about 23 wt.%, and the tramp iron content about 1.7 wt.%. Discarding all -20 mesh material, to minimize tramp silicon and iron pickup, will contribute 2.2% to the system loss. However, this material contributes substantially to skim generation and should be removed prior to melting for this reason.

It will be noted that certain alloys are more tolerant of tramp impurities, such as silicon, than others. in reference to AA3004 and At51 82, for example, it will be noted that the level is 0.30 wt.% max for AA3004 and 0.2 wt.% max for AA5182. Further, it will be seen from Table V and Figure 5 that as a result of tramp impurities, silicon can exceed these levels. Taking into consideration the weight percent and silicon content of each fraction, the amount of silicon can be calculated in the fragmented component.For instance, in the example provided for illustration, the amount of silicon in AA5182, Table V (without removing tramp impurities), is 0.30 wt.% silicon which greatly exceeds the limit of 0.20 wt.% for At51 82. However, removing tramp impurities in accordance with the invention, e.g., removing the material that passes through a U.S. No. 20 screen (Table VI) from the AA5182 fraction produces AA5182 material having only 0.17 wt.% silicon. It will be understood that 50% more siliconfree material would be required to lower the silicon content from 0.30 wt.% to 0.20 wt.%. Further, it will be understood that the fractions used and referred to in the tables are for purposes of illustration only and are not intended to limit the scope of the invention since different alloys can tolerate different levels of impurities.

In a test utilizing whole cans, the used beverage containers were processed in a test apparatus at about 598.90C (11 100F). The fragmented end pieces were 25.3% of the delacquered can weight. The body parts represented 74.7%. This suggests that the alloy separation was nearly 100% effective. The two portions were melted and analyzed. The spectrographic results appear in Table VIII which may be compared to AA5182 and AA3004 (See Tables IX and X). These analyses further support that 100% separation of the two alloys is possible when the starting material is whole cans.

TABLE I Screen Used to Fractionate the Samples U.S. Standard Sieve (U.S.) Tyler Mesh Screen Opening (mm) Equivalent 2 inches 50.8 2 inches 1 inch 25.4 1 inch 0.5 inch 12.7 0.5 mesh 0.265 inch 6.73 3 mesh No.4 4.76 4 mesh No. 7 2.83 7 mesh No. 10 2.00 9 mesh No. 14 1.41 12 mesh No.18 1.00 16 mesh No. 20 0.84 20 mesh No.25 0.71 24 mesh TABLE II Chemical Analyses of Ingoing (IN) and Exiting (OUT) Material for Each Size Fraction.

Kiln Set Temperature: 571.1 C (1060 F) U.S. Screen Si Fe Cu Mn Mg +2" IN .17 .41 .11 .90 1.19 OUT .17 .41 .11 .91 1.23 2" +1" IN .17 .41 .11 .92 1.22 OUT .18 .40 .10 .86 1.20 -1" + 1/2" IN .16 .38 .10 .85 1.72 OUT .16 .39 .11 .86 1.02 -1/2" + 0.265" IN .17 .41 .11 .91 1.19 OUT .17 .40 .11 .92 .78 -0.265" + 4 IN .21 .41 .12 1.00 .73 OUT .24 .42 .12 1.01 .78 -4 + 7 IN .37 .45 .14 1.06 .35 OUT .26 .45 .13 1.05 .68 -7 + 10 IN .24 .44 .13 1.06 .26 OUT .24 .48 .13 1.03 .54 -10* IN - - - - OUT - - - - *Contained insufficient metal content for quantometer analysis.

TABLE III Chemical Analyses of Size Fractions Exiting the Kiln at a Set Temperature: 582.20C (10800F) U.S. Screen Si Fe Cu Mn Mg +2" .17 .39 .11 .95 .96 -2" + 1" .18 .39 .10 .91 1.05 -1" + 1/2" .17 .39 .11 .90 1.10 -1/2" + 0.265" .17 .39 .10 .87 1.03 -0.265" + 4 .22 .38 .10 .83 1.63 -4+7 .18 .36 .09 .73 2.08 -7 + 10 .17 .32 .07 .60 2.70 -10 .23 .32 .11 .55 1.54 TABLE IV Chemical Analyses of Size Fractions Exiting the Kiln at a Set Temperature: 593.30C (1 1000F) U.S.Screen Si Fe Cu Mn Mg -2" .17 .41 .12 .94 .48 -2" + 1" .18 .42 .12 .97 .66 -1" + 1/2" .19 .42 .12 .98 .64 -1/2" + 0.265" .18 .41 .12 .94 .56 -0.265" + 4 .17 .35 .09 .73 1.36 -4+7 .15 .30 .19 .56 .2.57 -7 + 10 .15 .29 .06 .46 2.15 10* - - - - - TABLE V Chemical Analyses of Size Fractions Exiting the Kiln at a Set Temperature: 604.40C (1 1200F) U.S. Screen Si Fe Cu Mn Mg +2" .19 .44 .13 1.05 .58 -2" + 1" .18 .43 .12 1.02 .66 -1" + 1/2" .18 .44 .12 1.03 .67 -1/2" + 0.265" .18 .43 .12 1.02 .57 -0.265" + 4 .21 .37 .10 .82 1.61 -4 + 7 .17 .30 .07 .52 2.97 -7 + 10 .18 .25 .05 .36 3.43 -10* .50 .29 .07 .36 3.35 TABLE VI Chemical Analyses of Fractions Resulting from Further Fractionation of the Minus 10 Material Exiting the Kiln at Set Temperature 604.4 C (1120 F) U.S.Screen wt.% Si Fe Cu Mn Mg -10 + 14 2.6 .15 .27 .04 .38 3.67 -14+18 1.9 .16 .28 .04 . .38 3.82 - 18 + 20 0.5 .21 .26 .04 .35 3.64 -20 + 25 0.4 .35 .21 .05 .33 3.74 25* 1.8 - - - - *Contained insufficient metal content for quantometer analysis.

TABLE VII Analysis of Minus 25 Material Exiting the Kiln at a Set Temperature: 604.40C (1 1200F) % Aluminum by Hydrogen Evolution 56.2% Chemical Analysis: Al 56.7% Fe 1.74% Si 10.8% Calculated SiO2 23.1% % Magnetic Material 1.87% X-ray Diffraction: Aluminum > 10% Quartz > 10% MgO < 10% Unidentified < 10% TABLE VIII Chemical Analyses from Whole Can Experiment Having 3004 Bodies and 5182 Ends End Fragments Body Parts Si 0.10 0.19 Fe .25 .40 Cu .03 .14 Mn .36 1.09 Mg 3.69 .7 Cr .02 .01 Ni .00 .00 Zn .02 .04 Ti .01 .02 TABLE IX Others Alloy Silicon Iron Copper Manganese Magnesium Chromium Zinc Titanium Each Total AA3033 0.6 0.7 0.05-0.02 1.0-1.5 - - 0.10 - 0.05 0.15 AA3004 0.30 0.70 0.25 1.0-1.5 0.8-1.3 - 0.25 - 0.05 0.15 AA3104 0.6 0.8 0.05-0.25 0.8-1.4 0.1-1.3 - 0.25 0.10 0.05 0.15 Note: In Table IX, the balance is aluminum, and composition is in wt.% max unless shown as a range.

TABLE X Others Alloy Silicon Iron Copper Manganese Magnesium Chromium Zinc Titanium Each Total AA5182 0.20 0.35 0.15 0.20-0.50 4.0-5.0 0.10 0.25 0.10 0.05 0.15 AA5082 0.02 0.35 0.15 0.15 4.0-5.0 0.15 0.25 0.10 0.05 0.15 AA5052 0.45 Si + Fe 0.10 0.10 2.2-2.8 0.15-0.35 0.10 - 0.05 0.15 AA5042 0.20 0.35 0.20-0.50 3.0-4.0 0.10 0.25 0.10 0.05 0.15 Note: In Table X, the balance is aluminum, and composition is in wt.% max unless shown as a range.

While the invention has been described in terms of preferred embodiments, the claims appended hereto are intended to encompass other embodiments which fall within the scope of the invention.

Claims (34)

1. A method of segregating metallic components fabricated from different aluminum wrought alloys, the method comprising the steps of: (a) providing a feedstock containing at least two types of components therein comprised of different aluminum wrought alloys having different incipent melting temperatures; (b) heating the feedstock to a temperature sufficient to substantially increase the fracture sensitivity of at least one of said components to a level sufficient to cause fragmentation of at least one of said components upon agitation of the heated feedstock; (c) subjecting said heated feedstock to agitation sufficient to cause at least one of said components to fragment; and (d) segregating said fragmented components from the remaining feedstock.

2. A method in accordance with claim 1, wherein in step (b) the feedstock is heated to a temperature sufficiently high to initiate incipient melting of the component having the lowest incipient melting temperature, and in step (c) said heated feedstock is subjected to agitation sufficient to cause said component having the lowest incipient melting temperature to fragment.

3. A method in accordance with claim 1 or 2, wherein the feedstock provided in step (a) comprises aluminum container ends and aluminum container bodies, the ends and the bodies being fabricated from different aluminum wrought alloys, whereby said ends are separated and recovered from said bodies.

4. A method in accordance with any one of claims 1 to 3, wherein step (b) and (c) are repeated until all components comprising said feedstock are separated from one another.

5. A method in accordance with any one of the preceding claims, including using feedstock comprised of used food and beverage containers.

6. A method in accordance with claim 5, including sorting the feedstock prior to heating to remove contaminants including glass and steel containers.

7. A method in accordance with claim 5 or 6, including treating the feedstock to remove lacquers, decorative and protective coatings.

8. A method in accordance with any one of the preceding claims, including using tumbling action of the feedstock to cause the component having the lowest incipient melting temperature to fragment.

9. A method in accordance with any one of the preceding claims, wherein the feedstock contains one or more types of containers having body portions fabricated from an aluminum alloy comprising AA3003, AA5042, AA3004, AA3104 or AA5052, said containers having ends fabricated from an aluminum alloy comprising AA5182, AA5082, AA5052 or AA5042.

10. A method in accordance with any one of the preceding claims, wherein the feedstock contains containers having body portions formed from AA3004 and having ends thereon formed from AA5182.

11. A method in accordance with claim 10, including fragmenting and separating at least 50% of the AA5182 end material from the feedstock.

1 2. A method in accordance with claim 10, including fragmenting and separating at least 90% of the AA5182 end material from the feedstock.

1 3. A method in accordance with any one of claims 9 to 12, wherein the feedstock additionally contains containers having bodies and lids fabricated from sheet having the composition 0.1-1.0 wt.% Si, 0.01-0.9 wt.% Fe, 0.05-0.4 wt.% Cu, 0.4 to 1.0 wt.% Mn, 1.3 to 2.5 wt.% Mg and 0--0.2 wt.% Ti, the remainder being aluminum and incidental impurities.

14. A method in accordance with any one of the preceding claims, including shredding the feedstock prior to said heating.

1 5. A method in accordance with any one of the preceding claims, including controlling the heating in step (b) to avoid substantial melting of the component having the lower incipient melting temperature.

1 6. A method in accordance with any one of the preceding claims, wherein the feedstock is heated to a temperature in the range of 482.2 to 623.90C (900 to 11 550 F).

1 7. A method in accordance with any one of the preceding claims, wherein the feedstock is heated to a temperature in the range of 537.8 to 623.90C (1000 to 11 550C).

1 8. A method in accordance with claim 17, including maintaining the temperature of the feedstock in the range of 537.8"C to 623.9"C (1 0O00F to 11 550F) from about 15 seconds to several minutes.

1 9. A method in accordance with any one of the preceding claims, wherein the feedstock is heated to a temperature in the range of 580.6 to 623.90C (1077 to 11 550F).

20. A method in accordance with claim 1 9, including maintaining the temperature of the feedstock in the range of 580.60C to 604.40C (1 077 OF to 11 2O0F) from about 30 seconds to 15 minutes.

21. A method in accordance with any one of claims 1 to 15, wherein the feedstock is heated to a temperature in the range of 580.6 to 648.90C (1077 to 12000F).

22. A method in accordance with any one of claims 1 to 13, including providing feedstock prior to heating having particles therein of sizes larger than 2 mesh (Tyler Series).

23. A method in accordance with any one of the preceding claims, including magnetically separating iron values from the remaining feedstock in step (d).

24. A method according to any one of the preceding claims, wherein in said step (a), the feedstock has mixed therewith tramp impurities, in said step (c) the heated feedstock is agitated sufficiently to cause said component having the lowest incipient melting temperature to fragment and to cause said fragmented component to scour tramp impurities from the unfragmented feedstock, in step (d) said fragmented components and said tramp impurities are segregated from the unfragmented feedstock; and then said fragmented components are separated from said tramp impurities.

25. A method in accordance with claim 24, wherein the tramp impurities include calcium, sodium, silicon, iron, lead and aluminum and oxides thereof.

26. A method in accordance with claim 24 or 25, wherein a source of tramp impurities is dirt and clay.

27. A method in accordance with claim 26, including grinding dirt, clay and glass to a particle size smaller than the particle size of most of the recyclable components.

28. A method in accordance with any one of claims 24 to 27, wherein tramp impurities are separated from the fragmented components by screening.

29. A method according to any one of the preceding claims, which comprises shredding said feedstock provided in step (a), the shredding resulting in production of fines in the shredded feedstock and before heating step (b) removing from said shredded feedstock at least the fines having sizes in a size range of the fragmented components to be produced in step (c).

30. A method in accordance with claim 6 and 29, wherein the feedstock is sorted prior to shredding.

31. A method in accordance with claim 29 or 30, wherein said shredded feedstock is screened to remove fines therefrom.

32. A method in accordance with any one of claims 29 to 31, including delacquering said fines to remove lacquers, decorative and protective coatings therefrom.

33. A method according to claim 1 of segregating metallic components fabricated from different aluminum wrought alloys, substantially as hereinbefore described with reference to the Examples and/or the accompanying drawings.

34. Segregated metallic components of aluminum wrought alloys, whenever produced in accordance with the method of any one of the preceding claims.