Method for producing an aluminium secondary raw material from aluminium containing scrap

Abstract

The invention relates to a method for producing an aluminium secondary raw material composition, comprising the steps: a) producing or providing an aluminium-containing scrap composition, wherein the aluminium-containing scrap composition comprises: a1) a plurality of first scrap subvolumes consisting of a first metallic material with an aluminium content of 85 % or more, and a2) a plurality of second scrap subvolumes consisting of a second metallic material with an aluminium content of less than 85 %, b) comminuting the aluminium-containing scrap composition using predefined comminuting parameters, wherein the comminuted composition: i) first particles with an equivalent sieve diameter of less than 40 mm, ii) second particles with an equivalent sieve diameter in the range of 40 to 130 mm, and iii) third particles with an equivalent sieve diameter of more than 130 mm, wherein the predefined comminuting parameters are chosen so that 60 % or more of the first metallic material that is leaving the comminution unit is comprised by second particles, d) analysing particles of the comminuted composition with a optical detection device to detect a material information for the particles, wherein a mass fraction of more than [X] of the analysed particles are second particles, wherein [X] is the mass fraction of the second particles in the comminuted composition, and e) separating particles for that the material information does not meet a predefined quality criterion.

Description

[0001] The present invention relates to a method for producing an aluminium secondary raw material from an aluminium-containing scrap composition and a corresponding method for producing an aluminium product comprising the steps of the respective method.

[0002] Due to an ever-increasing demand for metallic raw materials and in view of an increased awareness for the aspect of sustainability in many industries, there exists a constant demand for alternative sources for such raw materials. Among such alternative sources for raw materials, scrap that is obtained by scrapping end-of-life metallic articles, is historically of great importance. Especially aluminium scrap has long been seen not only as a waste but also as an important secondary raw material which may be employed in numerous applications to reduce the need for newly produced metals. The use of scrap as raw material reduces the dependence of industry on scarce raw materials and reduces the amount of otherwise unnecessary refuse. The reduced demand for newly obtained metals and alloys whose large industrial scale production is generally associated with a considerable need for energy and other resources also allows for a more sustainable economy.

[0003] Especially in the field of producing scrap products for high-performance applications, like e.g. for car body sheets, particularly high requirements are placed on aluminium-containing scraps and their properties. If such scraps are to be employed instead of newly obtained metals these must reliably have material properties that are at least similar to those of newly obtained metals.

[0004] There is therefore in principle a great need for many industrial applications to obtain particularly pure aluminium scrap compositions, for that the content of impurities is within a predefined, typically quite narrow specification range, which ideally also have an advantageous poured density. However, this is well known to be a very challenging objective since the starting materials for the production of corresponding scrap compositions are inherently heterogeneous and, in many cases, only comprise comparably small amounts of aluminium or sufficiently aluminium rich alloys, potentially in conjunction with alloys, whose aluminium content is outside the specification, or other impurities that are difficult to separate.

[0005] To obtain corresponding aluminium rich scrap compositions the prior art discloses various, usually very complex processes which may in principle extend to manual sorting processes which merely comprise workers isolating particularly suitable fractions of a scrap composition. Operators of large industrial scale shredding plants often realize production of comparatively pure aluminium scrap compositions in practice by passing the processed scraps through the treatment plant and the shredder repeatedly, i.e. the scrap is processed using two or more comminution steps.

[0006] The processes known from the prior art have the disadvantage that they are either comparatively time- and / or cost-intensive, for example since they necessitate twofold processing of the materials, thus reducing the material throughput of the plant, or are not capable of providing the desired degree of purity.

[0007] In order to enhance the quality of the resulting scrap material that can be obtained from the processing of aluminium scrap it was suggested in the prior art to use optical detection methods like X-ray to automatically analyse the scrap that exits the shredder after the comminuting.

[0008] An example for a prior art process is disclosed in EP 2716774 A1. The method of EP 2716774 A1 is a good example for the prior art, as it utilizes a multi-stage process for crushing the scrap, employing a shredder and a post-shredder. The goal of the measures employed in EP 2716774 A1 is to provide for a well-dispersed, well-comminuted scrap composition that comprises sufficiently small particles in order to allow for a convenient analysis using an optical method, i.e. X-ray in the case of EP 2716774 A1. While modern processes like the one disclosed in EP 2716774 A1 can indeed provide for an improved processing of aluminium scrap, there still exists a demand for further increasing the efficiency of such processes and to increase the quality of the product that can be obtained with a given investment of time and costs.

[0009] While typical prior art processes employ an extensive comminuting to obtain sufficiently small particle sizes, some of these processes need to separate the smallest particles from the obtained well-comminuted scrap composition, e.g. by sieving, as these could cause problems in the down-stream devices and can in many cases not be efficiently processed.

[0010] In particular, many of the prior art processes are very demanding with respect to the required equipment, in particular with respect to the layout of multistage shredder and / or the optical detection device that is used. The latter is due to the fact that large quantities of the comminuted material need to be processed and analysed for their chemical composition in order to achieve sufficiently high removal rates for those scrap particles that do not consist of aluminium to the required degree.

[0011] It was the primary objective of the present invention to overcome or at least reduce the disadvantages of the prior art.

[0012] In particular it was an objective of the present invention to provide for a method or producing an aluminium secondary raw material from aluminium-containing scrap that allows the production of valuable aluminium scrap product that can be used as a secondary raw material even in demanding applications, with a beneficial time and cost efficiency.

[0013] In so far, it was an objective of the present invention that the identified method compared to the prior art processes should be able to provide for a higher product purity, i.e. higher aluminium contents and lower amounts of impurities, and / or provide comparable purity levels in a reduced time.

[0014] Furthermore, it was an objective of the present invention that the identified method should reduce the requirements for instrument-based requirement, e.g. for the optical detection devices used in such methods, in particular regarding the required throughput per ton of aluminium containing scrap composition, without limiting the quality of the aluminium secondary raw material that is obtainable by said process.

[0015] Likewise, it was an objective of the present invention that the identified method should be able to efficiently use scraped vehicles as input material in their entirety or at least almost in their entirety and still be able to deliver a high-quality product without requiring too much throughput for the detection devices.

[0016] It was a further objective of the present invention that the identified method should allow for efficient process automation and enable high throughput.

[0017] It was a further objective of the present invention to provide for a method for producing an aluminium product from an aluminium secondary raw material obtained with the identified method, that is particular suitable for the production of high value aluminium products, in particular car body sheets.

[0018] The inventors of the present invention have now found, that the above objectives can surprisingly be achieved if the comminuting of the aluminium-containing scrap composition that is fed into the method for producing an aluminium secondary raw material rather than being comminuted as much as possible -as known from the prior art, e.g. by a multi-stage shredder process- is instead subjected to a carefully controlled comminuting, for that the comminuting conditions are adjusted based on a desired degree of size reduction for aluminium-rich input material, allowing to obtain a comminuted composition from a more heterogenous input material with a distribution profile of particle diameters, wherein predominantly the intermediate fraction is analysed using an optical detection device, to allow for a separation of particles, that do not meet a predefined quality criteria in order to obtain a high quality aluminium secondary raw material, as defined in the attached claims.

[0019] In other words, the inventors found that it is beneficial to overcome the existing prejudice that the aluminium containing starting material should ideally be comminuted as much as possible, for example in a multi-stage shredder process, to obtain as much of the starting material with a small particle size, i.e. in one fraction with a small particle size. Instead, it was found highly beneficial to aim for a carefully adjusted, more intermediate degree of comminuting in order to obtain a composition that comprises three fractions of particles, i.e. particles of intermediate size as well as particles that are smaller and larger. Herein, the intermediate fraction is chosen with a comparatively narrow diameter range. This results in a comparably broad profile of the particle size distribution of the material that exits the shredder, wherein it is the intermediate fraction that is predominantly subjected to the subsequent analysis using an optical detection device.

[0020] Notably, the desired degree of comminuting can beneficially be obtained in a one-step shredding process, wherein the process parameters of the shredder are adjusted by the skilled person depending on an aluminium-rich reference input material, rather than focussing on the maximum size reduction of the employed heterogeneous input material. The inventors found, that adjusting the shredder process parameters in order to obtain a comminuted composition with a certain particle size profile on aluminium-rich input material, results -when employed on an actual heterogeneous input material- in a composition, in that the majority of those particles, that comprise enough aluminium to meet a predetermined quality criterion can be found in the intermediate fraction of the resulting particle size distribution. In clear contrast, the inventors found that the particles in both the smaller and the larger size fraction have a much higher chance of not meeting the predetermined quality criterion, due to not comprising enough aluminium and / or too many impurities. Thus, the efficiency of the process can be increased significantly, by reducing the number of particles that need to be subjected to the optical analysis.

[0021] Beneficially, when continuously employing the method for similar heterogeneous input materials, e.g. entire vehicles that comprise body parts and the engine block, using the carefully set comminuting conditions will result in a distribution pattern of particle sizes that is comparatively stable during the process, allowing to tailor the method and the down-stream devices towards a comparatively well defined mass of the intermediate size fraction.

[0022] In a preferred embodiment, the intermediate fraction can be separated from the smaller and larger particles before the analysis with the optical detection device. By predominantly forwarding the specific intermediate fraction into the optical analysis in the first place, the amount of scrap that needs to be put through the optical detection device can be reduced significantly, thereby reducing the demand for the material throughput through the optical detection device. Together with the fact, that it is not only possible but also preferred to use a simple single-stage comminuting process, the process has a much lower requirement for the employed apparatuses.

[0023] Without wishing to be bound by theory, based on their own experiments, the inventors assume that during crushing of the scrap particles in the aluminium-containing scrap composition, i.e. the heterogeneous input material, the breakup-behaviour of each particle under mechanical stress correlates with his chemical composition and thus his mechanical properties, with different metals and alloys each showing a specific break up-behaviour. By adjusting the process parameters of the shredder in a way that the desired aluminium rich materials predominantly experience a specific size reduction, while those pieces that have a composition outside the specification experience a larger or smaller size reduction, the specific breaking behaviour of aluminium rich scrap can be utilized to amass most of the most relevant scrap particles in the intermediate fraction.

[0024] The aforementioned objectives are therefore solved by the subject-matter of the present invention as defined in the claims. Hereinafter, the subject-matter of the invention is discussed in more detail, wherein preferred embodiments of the invention are disclosed.

[0025] It is particularly preferred to combine two or more of the preferred embodiments to obtain an especially preferred embodiment. Correspondingly, especially preferred is a method according to the invention, that defines two or more features of preferred embodiments of the present invention. Also preferred are embodiments in which a feature of one embodiment that is to some extent designated as preferred is combined with one or more further features of other embodiments that are designated to some extent as preferred.

[0026] The present invention relates to method for producing an aluminium secondary raw material composition from an aluminium-containing scrap composition, comprising the steps: a) producing or providing an aluminium-containing scrap composition, wherein the aluminium-containing scrap composition comprises: a1) a plurality of first scrap subvolumes consisting of a first metallic material with an aluminium content of 85 % or more, with respect to the mass of the first metallic material, and a2) a plurality of second scrap subvolumes consisting of a second metallic material with an aluminium content of less than 85 %, with respect to the mass of the second metallic material, b) comminuting the aluminium-containing scrap composition in a comminution unit to obtain a comminuted composition using predefined comminuting parameters, wherein the comminuted composition that is leaving the comminution unit comprises: i) first particles with an equivalent sieve diameter of less than 40 mm, ii) second particles with an equivalent sieve diameter in the range of 40 to 130 mm, and iii) third particles with an equivalent sieve diameter of more than 130 mm, wherein the predefined comminuting parameters are chosen so that 60 % or more of the first metallic material that is leaving the comminution unit is comprised by second particles, with respect to the mass of the first metallic material that is leaving the comminution unit, d) analysing particles of the comminuted composition with at least one optical detection device to detect at least one material information for the particles, wherein a mass fraction of more than [X] of the analysed particles are second particles, with respect to the combined mass of all analysed particles, wherein [X] is the mass fraction of the second particles in the comminuted composition, and e) separating particles for that the detected material information does not meet a predefined quality criterion to obtain an aluminium secondary raw material composition comprising particles for that the detected material information meets the predefined quality criterion.

[0027] The method of the present invention is a method for obtaining a high value aluminium composition starting from an input material that is aluminium-containing scrap. For the sake of a clear identification, the valuable product of the method according to the invention is labelled "aluminium secondary raw material composition", wherein its suitability to serve as a secondary raw material in the production of high-quality aluminium products is emphasized.

[0028] Preferred is a method according to the invention, wherein the method is conducted as a continuous or semi-continuous process, preferably a continuous process. Alternatively or additionally a method according to the invention is preferred, wherein the method is at least partially controlled by an electronic control unit.

[0029] Like for the prior art processes, the method of the present invention starts with an aluminium-containing scrap composition, i. e. the inhomogeneous input material for the process, that can either be provided from an external source or directly produced in the framework of the method of the present invention. In agreement with the skilled persons understanding, the term "aluminium-containing" means that the scrap composition comprises aluminium in its elemental, i.e. metallic, form or in any chemical compound, in particular in the form of alloys.

[0030] As defined above, the aluminium-containing scrap composition comprises a1) a plurality of first scrap subvolumes consisting of a first metallic material with at least a minimum aluminium content, and a2) a plurality of second scrap subvolumes consisting of a second metallic material with an aluminium content of less than 85 %, with respect to the mass of the second metallic material. In agreement with the skilled persons understanding, this clarifies that the aluminium-containing scrap composition is inhomogeneous and comprises both aluminium rich metallic material as well as metallic material for that the amount of aluminium is low, e.g. alloys in that aluminium is only a minor component or even non-aluminium containing metals like steel. Determining the aluminium content of an alloy poses no problem for the skilled person. If provided with a metallic material, the skilled person can employ established analytic techniques to analyse its composition, e.g. by established quantitative chemical methods that rely on dissolving a sample, e.g. in an acid, before analysing the composition of the resulting solution. Notably, the amount of aluminium can efficiently be analysed using an optical detection device, preferably the optical detection device that is employed in the method.

[0031] The above definition uses the term "subvolumes" to define the aluminium-containing scrap composition. In agreement with the skilled persons understanding, an aluminium-containing scrap composition can comprise several scrap pieces that comprise first metallic material and / or second metallic material and / or non-metallic material. For example, a vehicle door can comprise parts of aluminium rich metallic material together with parts of low aluminium content alloys or aluminium free metals as well as plastic or leather parts. Therefore, rather than defining the aluminium-containing scrap composition by its macroscopic pieces (e.g. doors or entire end of life vehicles), it is expedient to theoretically subdivide all scrap pieces into smaller subvolumes that consist entirely of a single material, e.g. the aluminium rich first metallic material or a non-metallic material. Therefore, typically it will be a method according to the invention in that the aluminium-containing scrap composition further comprises: a3) a plurality of third scrap subvolumes consisting of a non-metallic material, wherein the non-metallic material is exemplarily selected from the group consisting of ceramics, glasses, plastics and natural materials, e.g. leather or cotton fibre.

[0032] The first metallic material can be basically pure elemental aluminium or aluminium rich alloys, preferably aluminium alloys with one or more elements selected from the group consisting of copper, zinc, magnesium, manganese and silicium. The second metallic material can be alloys with a low amount of aluminium.

[0033] The above definition of the aluminium content of the first metallic material is adjusted to a first metallic material that -based on the experience of the inventor-is sufficiently aluminium rich for producing an aluminium secondary raw material that is suitable for several applications. However, if the desired purity of the aluminium secondary raw material is higher than the aluminium content in the first metallic material, it is a) necessary that a portion of the first subvolumes consists of first metallic material that exhibits the desired aluminium content and b) overall efficient, to adjust the aluminium content of the first metallic material, and therefore the minimum aluminium level of the material for that the comminuting is optimized, towards the desired aluminium content in the aluminium secondary raw material. In view of this, a method according to the invention is preferred, wherein the first metallic material has an aluminium content of 88 % or more, preferably 90 % or more, more preferably 92% or more, even more preferably 94 % or more, most preferably 96 % or more, in particular 98 % or more, with respect to the mass of the first metallic material. For the sake of clarity, it is efficient to not redefine the aluminium content in the second metallic material, due to the fact that the presence of aluminium poor subvolumes is still a requirement of the method to justify its use. Thus, if the above features are included, it is expedient to assume that a plurality of further scrap subvolumes are included, that consist of a third metallic material with an aluminium content of 85 % or more but less than [Z], wherein [Z] is the lower value of the first metallic material defined above.

[0034] A very efficient method is obtained, if the aluminium content of the first metallic material is set close to the desired aluminium content in the aluminium secondary raw material. Thus, a method according to the invention is preferred, wherein the first metallic material has an aluminium content of 0,9*[Y] or more, preferably 0,95*[Y] or more, more preferably 0,98*[Y] or more, even more preferably 0,99*[Y] or more, most preferably 1,0*[Y], with respect to the mass of the first metallic material, wherein [Y] is the aluminium content of the aluminium secondary raw material, with respect to the mass of the aluminium secondary raw material.

[0035] Aluminium-containing scrap compositions that can be used in a method according to the invention are in principle known to the skilled person. Such aluminium-containing scrap compositions are inhomogeneous and in many cases comprise scrap from different sources or at least larger scrap pieces that have a inhomogeneous composition, for example end of life vehicles. Relevant for most embodiments is therefore a method according to the invention, wherein the aluminium-containing scrap composition is an inhomogeneous aluminium-containing scrap composition comprising aluminium-containing scrap from two or more, preferably three or more, more preferably four or more, different sources.

[0036] Due to the fact that scrap that is obtained directly from industrial production processes for producing aluminium products, is typically comparably pure and can in many cases easily be recycled, the method of the present invention is of particular interest for recycling end of life scrap, i.e. scrap that originates from products that were used for their purpose before reaching their end of life. Preferred is a method according to the invention, wherein the aluminium-containing scrap composition comprises end of life scrap. Especially preferred is a method according to the invention, wherein the aluminium-containing scrap composition comprises scrap that is selected from the group consisting of construction wastes, production wastes, and end of life vehicle scrap and household waste, preferably end of life vehicle scrap. Herein, it is an important benefit of the present invention, that the method according to the invention can efficiently produce a high quality aluminium secondary raw material composition from end of life vehicle scrap that e.g. still comprise the engine block, that typically is mostly aluminium free, preferably from end of life vehicle scrap that comprise more than 90 % by mass of all metallic parts of the end of life vehicle, preferably more than 95 %, more preferably more than 98 %, most preferably basically 100 %.

[0037] As defined above, the input material is aluminium-containing. In order to obtain a very efficient process, it is expedient to choose an input material, with as much initial aluminium content as possible. The skilled person readily understands that it is beneficial, to e.g. provide for an initial selection step, that removes larger scrap parts, that are known to not comprise sufficient aluminium, e.g. those parts of cars, that are predominantly made of steel or plastics. For example, it is conceivable to e.g. separate the comparatively aluminium rich doors of end of life vehicles from the remaining scrap, to employ only the doors in the method of the present invention. Therefore, for maximising the yield and efficiency it is beneficial to use comparably aluminium-rich scrap compositions as a starting material, in particular scrap compositions that comprise high amounts of the first metallic material. This is particular true because obtaining at least intermediate aluminium amounts, e.g. of 40 to 60 % by mass, for the starting material is comparably easy and cheap, e.g. by employing a rough hand sorting and / or very basic separation techniques, e.g. for iron removal. If the process according to the invention is operated in this way, the comparably larger effort to obtain the highest levels of purity are not spend on contaminants, that could have been more efficiently removed with much lower effort. Preferred is a method according to the invention, wherein the aluminium-containing scrap composition comprises aluminium in an amount of 50 % or more, preferably 70 % or more, more preferably 90 % or more, with respect to the mass of the aluminium-containing scrap composition, and / or wherein the aluminium-containing scrap composition comprises aluminium in an amount in the range of 40 to 95 %, preferably in the range of 50 to 90 %, more preferably in the range of 60 to 85 %, most preferably in the range of 70 to 80 %, with respect to the mass of the aluminium-containing scrap composition.

[0038] The skilled person understands that it will be particularly efficient, if the input material not only has a high average aluminium content, but also comprises a lot of its aluminium in aluminium rich metallic materials, i.e. first metallic materials. Correspondingly, a method according to the invention is preferred, wherein the aluminium-containing scrap composition comprises first metallic material in an amount of 50 % or more, preferably 70 % or more, more preferably 90 % or more, with respect to the mass of the aluminium-containing scrap composition, and / or wherein the aluminium-containing scrap composition comprises first metallic material in an amount in the range of 40 to 95 %, preferably in the range of 50 to 90 %, more preferably in the range of 60 to 85 %, most preferably in the range of 70 to 80 %, with respect to the mass of the aluminium-containing scrap composition.

[0039] While it is efficient to use an aluminium-rich scrap composition, it is considered an important advantage of the method according to the invention that it can yield excellent results starting from a comparably aluminium-poor starting material. In particular, excellent results are obtained when entire end of life vehicles are used as input material that sometimes comprise just 2 % by mass of aluminium. Thus, especially preferred is a method according to the invention, wherein the aluminium-containing scrap composition comprises aluminium in an amount of 2 % or more, preferably 3 % or more, more preferably 4 % or more, with respect to the mass of the aluminium-containing scrap composition, and / or wherein the aluminium-containing scrap composition comprises aluminium in an amount in the range of 2 to 55 %, preferably in the range of 3 to 50 %, more preferably in the range of 4 to 45 %, most preferably in the range of 5 to 40 %, with respect to the mass of the aluminium-containing scrap composition.

[0040] In analogy to the above arguments, a method according to the invention is particularly preferred for applications, wherein the aluminium-containing scrap composition comprises first metallic material in an amount of 2 % or more, preferably 3 % or more, more preferably 4 % or more, with respect to the mass of the aluminium-containing scrap composition, and / or wherein the aluminium-containing scrap composition comprises first metallic material in an amount in the range of 2 to 50 %, preferably in the range of 3 to 45 %, more preferably in the range of 4 to 40 %, most preferably in the range of 5 to 35 %, with respect to the mass of the aluminium-containing scrap composition.

[0041] In particular if aluminium-containing scrap compositions with a potentially low aluminium-content are used, it is beneficial to employ one or more additional sorting step between steps b) and c) in order to remove particles with strongly diverging properties from the comminuted composition, e.g. with respect to density or magnetic properties, in order to increase the relative concentration of aluminium in the comminuted composition before the optical analysis. For this, known techniques can be employed, that allow for comparatively rough high throughput sorting with a beneficial cost efficiency.

[0042] Preferred is a method according to the invention, wherein the method comprises before step d) one or more separation steps for removing organic impurities and / or magnetic material from the comminuted composition, wherein the separation steps are preferably selected from the group consisting of windsifting and magnetic separation, in particular eddy current separation.

[0043] The inventors suggest that the aluminium-content of the comminuted composition should be as high as reasonably possible before the optical analysis, either by employing an aluminium rich starting material or employing an additional sorting step before the optical analysis to subsequently increase the aluminium content in the comminuted composition. Thus, preferred is a method according to the invention, wherein the comminuted composition in step d) comprises aluminium in an amount of 80 % or more, preferably 90 % or more, more preferably 95 % or more, with respect to the mass of comminuted composition. Additionally or alternatively, preferred is a method according to the invention, wherein the comminuted composition in step d) comprises first metallic material in an amount of 80 % or more, preferably 90 % or more, more preferably 95 % or more, with respect to the mass of comminuted composition.

[0044] The inventors of the present invention found that the method according to the invention is particularly suited to isolate aluminium in high purities from aluminium-containing scrap compositions that comprise aluminium alloys with a low amount of aluminium alloys as impurities, that form a very important group of impurities in many end of life scrap materials. Thus, to utilize the beneficial suitability for removing such alloys, the inventors suggest applying the method according to the invention to aluminium-containing scrap compositions, that do indeed comprise such alloys. Thus, a method according to the invention is preferred, wherein the aluminium-containing scrap compositions comprises second scrap subvolumes consisting of second metallic materials that are selected from the group consisting of aluminium alloys, preferably aluminium alloys with one or more elements selected from the group consisting of copper, zinc, magnesium, manganese and silicium.

[0045] However, taken into consideration that it is overall efficient to use an aluminium-rich starting material, the inventors suggest that the total amount of alloys with a low aluminium content should not be too large either. Therefore, a method according to the invention is preferred, wherein the aluminium-containing scrap composition comprises second metallic materials that are aluminium alloys, in a combined mass fraction of 30 % or less, preferably 20 % or less, more preferably, 10 % or less, with respect to the mass of the aluminium-containing scrap composition, and / or wherein the aluminium-containing scrap composition comprises second metallic materials that are aluminium alloys, in a combined mass fraction in the range of 0,5 to 25 %, preferably in the range of 1 to 20 %, more preferably in the range of 5 to 15 %, with respect to the mass of the aluminium-containing scrap composition.

[0046] Besides for aluminium alloys with low aluminium content, excellent results were achieved with the method according to the invention when removing iron and its alloys, in particular steel. Therefore, it is also beneficial to utilize this capability of the method according to the invention and employ an aluminium-containing scrap composition that comprises iron and its alloys. Therefore, a method according to the invention is preferred, wherein the aluminium-containing scrap composition comprises second scrap subvolumes consisting of second metallic materials that are selected from the group consisting of iron and iron alloys, in particular steel, wherein the combined mass fraction of such second metallic materials preferably is 30 % or less, more preferably 20 % or less, even more preferably 10 % or less, with respect to the mass of the aluminium-containing scrap composition, and / or wherein the aluminium-containing scrap composition comprises second metallic materials that are selected from the group consisting of iron and iron alloys, in a combined mass fraction in the range of 0,5 to 25 %, preferably in the range of 1 to 20 %, more preferably in the range of 5 to 15 %, with respect to the mass of the aluminium-containing scrap composition.

[0047] Without wishing to be bound by theory, the inventors assume that the beneficial performance of the method of the present invention for removing unsuitable aluminium alloys as well as iron and its alloys, is due to the distinct difference in the breaking and crushing behaviour of such impurities compared to the desired aluminium rich first metallic material that allows to efficiently separate such materials as first and / or third particles, respectively, from the comminuted composition in that the first metallic material is predominantly in the intermediate fraction. It is therefore found that the selection of an aluminium-enriched intermediate fraction in the method of the present invention is specifically suited to pre-isolate aluminium rich particles from such second metallic materials.

[0048] While it is possible in theory to provide the aluminium-containing scrap composition to the process, in practice it will more relevant that the aluminium-containing scrap composition is produced during the process, i.e. on-site. For this, the aluminium-containing scrap composition can for example be directly produced in the comminution unit or directly before the comminution unit, e.g. on a conveyer that leads towards the comminution unit. Correspondingly, a method according to the invention is preferred, wherein the aluminium-containing scrap composition is produced within the comminution unit. Exemplary is a method according to the invention, wherein the aluminium-containing scrap composition is fed into the comminution unit with a conveyor, preferably a conveyor belt. A method according to the invention is preferred, wherein the aluminium-containing scrap composition is continuously fed into the comminution unit.

[0049] In process step b) a comminuting unit is used to comminute the aluminium-containing scrap composition. In agreement with the skilled person's understanding, the comminution unit serves to crush the scrap material and to reduce the aluminium-containing scrap composition to obtain smaller particle sizes. Herein, it is an advantage of the present invention, that the skilled person can use typical comminution units that are commercially available, in particular so-called shredders. Thus, a method according to the invention is preferred, wherein the comminution unit is a shredder. A method according to the invention is especially preferred, wherein the comminution unit comprises: a comminuting space having at least one discharging outlet for comminuted material and at least one rotor arranged in the comminuting space and fitted with one or more crushing elements.

[0050] Insofar, a method according to the invention is preferred, wherein the rotation speed of the plurality of crushing elements is in the range of 10 to 90 m / s, preferably in the range of 15 to 80 m / s, more preferably in the range of 20 to 70 m / s.

[0051] Additionally or alternatively, a method according to the invention is preferred, wherein the crushing elements have a weight in the range of 100 to 250 kg, preferably in the range of 110 to 220 kg, more preferably in the range of 120 to 190 kg. Additionally or alternatively, a method according to the invention is preferred, wherein the discharging outlet has dimension of 90 to 150 mm times 130 to 190 mm, preferably of 100 to 140 mm times 140 to 180 mm, more preferably of 110 to 130 mm times 150 to 170 mm.

[0052] As indicated above, it is an important advantage of the present invention, that the aluminium-containing scrap composition does not need to be reduced in its particle size as much as possible, wherein instead a comparable intermediate degree of particle size reduction is desired that is carefully optimized to concentrate first metallic material in the intermediate particle fraction, i.e. in the second particles. Apart from the advantages in the efficiency of aluminium isolation, this also beneficially reduces the demand for sophisticated, multi-stage comminuting schemes and apparatuses. In fact, as a multi-stage comminuting, that is known from the prior art, aims at reducing the particle size to make it sufficient for the needs of the respective process, thereby aiming to receive as much of the scrap in a single fraction, the use of such comminuting schemes is explicitly less preferred, wherein it is most preferred to use a one stage comminuting process, e.g. by employing just a single shredder. Correspondingly, a method according to the invention is preferred for the vast majority of embodiments, wherein the comminuting is conducted using a single comminution unit, and / or wherein the comminuting is a single stage commuting. In other words, a method according to the invention is preferred, wherein the comminuted composition is not comminuted further.

[0053] In accordance with the definition given above, the comminuting is conducted in a specific way as to obtain a comminuted composition comprises i) first particles with an equivalent sieve diameter of less than 40 mm, ii) second particles with an equivalent sieve diameter in the range of 40 to 130 mm, and iii) third particles with an equivalent sieve diameter of more than 130 mm, meaning that at least minor amounts of each particle type need to be present.

[0054] The comminuting is conducted using predefined comminuting parameters. In agreement with the skilled persons understanding, these predefined comminuting parameters are specific for the comminution unit that is employed, wherein potentially different predefined comminuting parameters would be employed if a different comminution unit is installed, or an existing comminution unit is modified.

[0055] The predefined comminuting parameters are chosen so that the majority of the first metallic material that is comprised by the aluminium-containing scrap composition ends up in second particles, i.e. particles with an equivalent sieve in the range of 40 to 130 mm. In other words, the comminuted composition that is leaving the comminution unit comprises 60 % or more of the first metallic material in second particles.

[0056] The above defined particle size target for the first metallic material serves as an instruction to the skilled person on how to define the comminuting parameters parameter of the employed comminuting unit. The skilled person understands that the process parameter required to obtain this target can vary significantly depending on the comminution unit that is employed. However, in view of the present teaching, for any specific comminution unit, the skilled person can identify suitable process parameter for the comminution unit that are suitable to obtain the desired result, using routine experiments. More specifically, the skilled person can change the comminuting parameters in an iterative process until he finds that the required portion of the first metallic material is comprised in the intermediate fraction, i.e. the second particles. Synergistically, the optical detection device can be used to allow for a convenient analysis of the distribution of the first metallic material. In a particular efficient approach, starting values for the optimization of the comminuting parameters can be obtained in a preceding calibration run, in that instead of a typical, everyday input material, a reference input material is used that comprises predominantly or even entirely scrap that consists mostly or even entirely of first metallic material. For example, a calibration run could be performed using comparably pure post industrial scrap, i.e. a scrap that basically completely consists of pure aluminium or an aluminium rich alloy, whose aluminium content is similar to the expected aluminium content in the first metallic material in the aluminium-containing scrap composition. Due to the low number of impurities, it is particularly easy to find starting values for the optimization of the comminuting parameters in that aluminium rich scrap predominantly ends up in the desired particle size range. Based on these starting values, the remaining optimization will typically be fast and only needs to take into account comparably minor deviations that result from the inhomogeneity of the aluminium-containing scrap composition and the nature of the scrap contained therein.

[0057] For the optimization, the skilled person will in particular change the power of the comminution unit and / or the rotation speed of the hammers and / or the average residence time of the scrap within the comminution unit, that can e.g. be adjusted by changing the size of the discharger of the comminution unit. Insofar, a method according to the invention is especially preferred, wherein the comminuting parameters are selected from the group consisting of comminuting power and average residence time of the scrap in the comminution unit.

[0058] In other words, a method according to the invention is preferred, comprising a preparatory step of adjusting the comminuting in step b), wherein the predetermined comminuting parameters for use in the method are determined iteratively, wherein preferably the preparatory step comprises one or more calibration runs for identifying starting values for the optimization of the comminuting parameters, wherein for the calibration runs the method is conducted using a reference aluminium-containing scrap composition, that comprises first metallic material in an amount of 80 % or more, preferably of 90 % or more, more preferably 95 % or more, even more preferably 98 % or more, most preferably basically 100 %, with respect to the mass of the reference aluminium-containing scrap composition.

[0059] It is especially preferred to adjust the predefined comminuting parameters so that as much of the first metallic material is in the intermediate fraction, although amassing basically 100 % in the second particles will be very difficult for most cases. Thus, preferred is a method according to the invention, wherein the predefined comminuting parameters are chosen so that 65 % or more, preferably 70 % or more, more preferably 75 % or more, even more preferably 80 % or more, most preferably 85 % or more, potentially even 90 % or more, of the first metallic material that is leaving the comminution unit is comprised by second particles, with respect to the mass of the first metallic material that is leaving the comminution unit.

[0060] Based on the idea that the breaking behaviour of pieces that comprise first metallic material can be used to convert most of such pieces into second particles, while different metallic materials will more likely end up as smaller or larger particles, it is clear to the skilled person that the presence of second metallic material will in most cases result in first and / or third particles that comprise the second metallic material. Thus, preferred is a method according to the invention, wherein the predefined comminuting parameters are chosen so that 10 % or more, preferably 20 % or more, more preferably 30 % or more, even more preferably 40 % or more, most preferably 50 % or more, of the second metallic material that is leaving the comminution unit is comprised by first particles and / or third particles, with respect to the mass of the second metallic material that is leaving the comminution unit.

[0061] In particular, in the preferred case, in that the method of the invention is used to remove a notable amount of material with an insufficient aluminium content, it is expected that both the first particle and the second particle fraction are notably populated, while the intermediate fraction will in most cases be the majority fraction. Typically for most cases will be a method according to the invention, wherein the comminuted composition that is leaving the comminution unit comprises with respect to the mass of the comminuted composition: i) first particles with an equivalent sieve of less than 40 mm in a combined mass fraction of 1 % or more, preferably 2 % or more, more preferably 3 % or more, and / or ii) second particles with an equivalent sieve in the range of 40 to 130 mm in a combined mass fraction of 40 % or more, preferably 50 % or more, more preferably 60 % or more, and / or iii) third particles with an equivalent sieve of more than 130 mm in a combined mass fraction of 0,2 % or more, preferably 0,5 % or more, more preferably 1 % or more.

[0062] During the development of the present invention, in comprehensive experiments the inventors identified exemplary particle size distributions for the comminuted composition that can be obtained for relevant input materials, in particular when employing mostly complete end of life vehicles.

[0063] Exemplary is a method according to the invention, wherein the comminuted composition that is leaving the comminution unit comprises with respect to the mass of the comminuted composition: i) first particles with an equivalent sieve of less than 40 mm in a combined mass fraction in the range of 2 to 20 %, ii) second particles with an equivalent sieve in the range of 40 to 130 mm in a combined mass fraction in the range of 65 to 97,5 %, and iii) third particles with an equivalent sieve of more than 130 mm in a combined mass fraction in the range of 0,5 to 15 %.

[0064] Specifically, with respect to the first particles, a method according to the invention is preferred, wherein the comminuted composition comprises first particles in a combined mass fraction in the range of 2,5 to 17,5 %, preferably in the range of 5 to 15 %, more preferably in the range of 7,5 to 12,5 %. Additionally or alternatively, a method according to the invention is preferred, wherein the comminuted composition comprises 2 % or less, preferably 1,5 % or less, more preferably 1 % or less, most preferably 0,5 % or less, first particles with a diameter of 10 mm or less, preferably 15 mm or less, most preferably 20 mm or less.

[0065] Regarding the second particles, a method according to the invention is preferred, wherein the comminuted composition comprises second particles in a combined mass fraction in the range of 70 to 96,5 %, preferably in the range of 75 to 93,5 %, more preferably in the range of 80 to 90,5 %, and / or wherein the comminuted composition comprises second particles in a combined mass fraction of 67,5 % or more, preferably of 70 % or more, more preferably of 72,5 % or more.

[0066] For the third particles, a method according to the invention is preferred, wherein the comminuted composition comprises third particles in a combined mass fraction in the range of 1 to 12,5 %, preferably in the range of 1,5 to 10 %, more preferably in the range of 2 to 7,5 %. Additionally or alternatively, a method according to the invention is preferred, wherein the comminuted composition comprises 2 % or less, preferably 1,5 % or less, more preferably 1 % or less, most preferably 0,5 % or less, third particles with a diameter of 300 mm or more, preferably 250 mm or more, most preferably 200 mm or more.

[0067] The inventors found that it is especially preferred to conduct the comminuting in a way that the majority of the second particles has a size in the middle on the range defined above. In particular, a method according to the invention is preferred, wherein the comminuted composition comprises second particles with a diameter in the range of 50 to 120 mm in a combined mass fraction in the range of 70 to 95 %, preferably in the range of 75 to 90 %. Additionally or alternatively, a method according to the invention is preferred, wherein the comminuted composition comprises second particles with a diameter in the range of 60 to 110 mm in a combined mass fraction in the range of 70 to 92,5 %, preferably in the range of 75 to 87,5 %.

[0068] In the framework of the present invention, the diameter of the particles refers to the equivalent sieve diameter of such particles, as is e.g. relevant for sieving. In other words, it refers to an equivalent spherical diameter of the oftentimes irregularly shaped objects that corresponds to the largest ideal sphere that can pass through a sieve with the same mesh size. In other words, the equivalent sieve diameter is the largest diameter of a particle's smallest projection surface, so that this particle can pass through a give sieve aperture. This is in agreement with the skilled person's understanding and the respective diameter can conveniently be measured for large quantities of particles using sieving devices. As an alternative, as the relevant sizes are in the range of millimetres, the quantification of the particle size distribution can also readily be conducted using optical methods, e.g. camera based analysis, potentially in conjunction with machine learning identification of the sizes. The mass fraction of the three fractions can be determined for a representative sample of the comminuted composition. In practice, the relevant analysis will in most cases be conducted by separating the particle fractions via sieving and weighting the fractions. As the first particles can comprise potentially very small particles that might be more difficult to separate with some sorting methods, the mass fraction can also be derived from the overall weight of the comminuted composition after subtraction of the weight of the two larger fractions. Thus, the analysis of the particle size distribution in the comminuted composition can readily be analysed by the skilled person, using e.g. a sieve-based separation of the fractions.

[0069] In view of the above definition, the skilled person understands that the combined mass fraction of first particles, second particles and third particles will always be 100 %.

[0070] In step d) particles of the comminuted composition are analysed using an optical detection device, i.e. an electronic device for conducting an optical detection.

[0071] Before going into more detail about the optical analysis and the methods employed, it is emphasized that the analysed particles will not only be predominantly second particles but second particles will also - among all particles analysed - have a larger share by mass than their mass fraction in the comminuted composition. This is expressed by the feature that a mass fraction of more than [X] of the analysed particles are second particles, with respect to the combined mass of all analysed particles, wherein [X] is the mass fraction of the second particles in the comminuted composition.

[0072] The skilled person understands that this means, that not the entire comminuted composition that is received from the comminuting unit is analysed using the optical detection device. Instead, the focus of the analysis is on the second particles. In the above definition, this is defined by clarifying, that the mass fraction of second particles relative to the mass of all analysed particles is larger than the second particles mass fraction in the comminuted composition. A method according to the invention is preferred, wherein more than ([X] +0,2 %), preferably more than ([X]+0,5 %), more preferably more than ([X]+1,0 %), most preferably more than ([X] + 2,0 %), by mass of the analysed particles are second particles, and / or wherein more than 97,5 %, preferably more than 98 %, more preferably more than 99 %, most preferably more than 99,5 %, particularly preferably 99,9 %, by mass of the analysed particles are second particles.

[0073] For achieving a very efficient process, the inventors suggest that it is expedient to isolate the second particles at least partially from the other particles before subjecting them to the optical analysis. In such a case, the optical analysis can be conducted for all the particles in a so-called size-selected composition while automatically meeting the criterion that the mass fraction of the second particles among all particles analysed shall be higher than their respective mass fraction in the comminuted composition. In view of this, a method according to the invention is especially preferred, wherein the method comprises between steps b) and d) the step of c) separating first particles and / or third particles from the second particles of the comminuted composition to obtain a size-selected composition, wherein the size-selected composition comprises the second particles in a combined mass fraction of more than [X], with respect to the mass of the size-selected composition.

[0074] In this optional but preferred process step c), a size-selected composition is produced from the comminuted composition. This size-selected composition comprises a higher amount of and preferably predominantly second particles, i.e. the intermediate fraction in the above particle size distribution. The skilled person understands that this size-selected composition is the composition that is subsequently analysed with the optical detection device. For obtaining the size-selected composition, there are in principle two ways. Either by separating first and / or third particles, preferably first and third particles, from the comminuted composition or removing second particles from the comminuted composition and collecting them in the size-selected composition, thereby separating them from the first and third particles as well. However, as the comminuted composition in preferred embodiments will predominantly consist of second particles, the inventors suggest that it is more efficient, to remove the first and / or third particles. Herein, it is beneficial, that this way most of the second particles from the comminuted composition can be transferred to the size-selected composition. Although it would be possible in theory that the size-selected composition - while essentially consisting of second particles - only comprises a fraction of the second particles that were contained in the comminuted composition, combining at least most of the second particles from the comminuted composition in the size-selected composition is highly preferred. In view of the above, a method according to the invention is preferred, wherein the size-selected composition comprises the second particles in a combined mass fraction of 98 % or more, preferably of 99 % or more, more preferably of 99,5 % or more, most preferably of 99,9 % or more, particularly preferably of essentially 100 %. Additionally or alternatively, a method according to the invention is preferred, wherein the size-selected composition comprises second particles with an equivalent sieve diameter in the range of 50 to 120 mm in a combined mass fraction of 99 % or more, preferably 99,5 % or more, more preferably 99,9 % or more, most preferably of essentially 100 %, wherein preferably second particles with a larger and / or smaller equivalent sieve diameter are separated from the comminuted composition. Again, additionally or alternatively, method according to the invention is preferred, wherein the size-selected composition comprises second particles with an equivalent sieve diameter in the range of 60 to 110 mm in a combined mass fraction of 99 % or more, preferably 99,5 % or more, more preferably 99,9 % or more, most preferably of essentially 100 %, wherein preferably second particles with a larger and / or smaller diameter are separated from the comminuted composition.

[0075] It can be considered an advantage of the preferred method according to the invention, that the separating in process step c) can rapidly be conducted using very robust and efficient methods, that are known in the art for isolating a certain size fraction, for example sieving and wind sifting, wherein sieving is particularly preferred. Herein, the wind sifting can take many forms, wherein the general principle is the same, namely that a density / size selection is achieved using an airflow, that is e.g. generated by a ventilator against the direction of the falling pieces. Thus, a method according to the invention is preferred, wherein the separating in step c) comprises a sieving, and / or wherein the separating in step c) is at least partially, preferably predominantly, made by using one or more sieves. Additionally or alternatively, a method according to the invention is preferred, wherein the separating in step c) comprises a wind sifting, and / or wherein the separating in step c) is at least partially made by using one or more wind sifter.

[0076] As an alternative to the above-described physical separation of second particles and the production of a size-selected composition the inventors suggest that a very beneficial process can be obtained, if the analysis in step d) is conducted in a size-selective way, without actually separating the particles before the optical detection device. For this, the optical detection device can comprise means for determining the size of the analysed particles, wherein the optical detection device is configured to measure only particles with an equivalent sieve diameter in a certain range, preferably within the range defined above for the second particles. Such means for analysing the particle size can for example be a camera with a respective software, wherein in particular machine learning can efficiently be deployed to only apply the optical analysis for particles in the preferred parameter range.

[0077] The composition of the particles that shall be analysed is fed into the optical detection device. Thus, it is a method according to the invention, wherein the comminuted composition or the size-selected composition is fed into the detection zone of the optical detection device, preferably with a conveyor.

[0078] The optical detection device employs an optical measurement method, wherein the term optical measurement method within the framework of the present invention comprises all detection methods, that are based on electromagnetic radiation, in particular X-ray or light. Due to the high quality of the achieved analysis as well as the high throughput that becomes possible, a method according to the invention is preferred, wherein the optical detection device is selected from the group consisting of optical detection device for x-ray analysis, preferably x-ray transmission or x-ray fluorescence, infrared analysis, and laser-induced breakdown spectroscopy (LIBS), preferably x-ray transmission or laser-induced breakdown spectroscopy (LIBS), most preferably x-ray transmission. In other words, a method according to the invention is preferred, wherein the analysis in step d) is made by x-ray analysis, preferably x-ray transmission or x-ray fluorescence, infrared analysis and / or laser-induced breakdown spectroscopy, preferably x-ray transmission or laser-induced breakdown spectroscopy, most preferably x-ray transmission.

[0079] The purpose of this analysis in the optical detection device is to measure for each particle under study at least one material information that can be correlated with its chemical composition, in particular the amount of aluminium in the particle. In other words, it is a method according to the invention, wherein the material information detected for the particles correlates with the chemical composition of the particles, preferably with the amount of aluminium in the particles and / or the amount of contaminants in the particles, preferably of iron and / or alloys with insufficient aluminium content, in particular aluminium alloys with insufficient aluminium content. A method according to the invention is preferred, wherein the material information detected for the particles is the x-ray transmission of the particles.

[0080] Referring to the first metallic material, a method according to the invention, wherein the material information detected for the particles correlates with the amount of first metallic material in the particles and / or the amount of second metallic material in the particles.

[0081] The goal of the analysis of the particles with the optical detection device is to subsequently separate those particles that do not have the desired amount of aluminium and / or comprise unwanted contaminants from the composition in order to obtain the aluminium secondary raw material composition in the desired purity. For this, a predefined quality criterion is set in order to distinguish those particles that are allowed to proceed to the final aluminium secondary raw material composition from those that should be separated. The skilled person understands that a method according to the invention is preferred for most embodiments, wherein the predefined quality criterion for the material information correlates with a minimum amount of aluminium in the particles, and / or wherein the predefined quality criterion for the material information correlates with a maximum amount of contaminants in the particles, preferably of iron and / or alloys with insufficient aluminium content, in particular aluminium alloys.

[0082] Using a different reference, a method according to the invention is preferred for most embodiments, wherein the predefined quality criterion for the material information correlates with a minimum amount of the first metallic material in the particles, and / or wherein the predefined quality criterion for the material information correlates with a maximum amount of second metallic material in the particles.

[0083] Insofar, the Inventors suggest that the predefined quality criterion can also be that the material information lies within a certain parameter range, thereby excluding particles that exhibit higher or lower values, e.g. when the grey tint obtained from a x-ray-measurement is used.

[0084] The inventors found that beneficially a compensation scheme can be employed when setting the predefined quality criterion for the material information. Said compensation scheme can profit from the fact, that typically the particles will exhibit a distribution of aluminium content. Thus, several particles will have very high aluminium contents. As the target aluminium content that is desired for the aluminium secondary raw material is a bulk property that is the average of the multitude of particles comprised by the aluminium secondary raw material, such particles with a high aluminium content can compensate for particles that have an aluminium content that lies below the desired target specification. While this provides a beneficial safety measure against imperfections of the optical measurement as well, this in particular allows to set the predefined quality criterion to an aluminium concentration that is lower than the actual target of the aluminium concentration in the aluminium secondary raw material. Thus, a process according to the invention is preferred, wherein the predefined quality criterion for the material information correlates with a minimum amount of aluminium in the particles, wherein the minimum amount of aluminium in the particles is lower than [Y], wherein [Y] is the aluminium content of the aluminium secondary raw material, with respect to the mass of the aluminium secondary raw material.

[0085] In order to facilitate the separation depending on the detected material information, it is expedient to derive a spatial and / or temporarily resolved information about the analysed particles, so that a subsequent sorting mechanism can identify those particles that need to be separated based on their position and / or the time that they arrive at a certain position. Thus, a method according to the invention is preferred, wherein the material information is detected with the optical detection device with a spatial and / or temporal resolution to obtain a spatially and / or temporally resolved information profile of the analysed particles.

[0086] While it in principle is possible to conduct the separation in dependence on the detected material information by hand, it is most preferred to use an automated apparatus, wherein in particular pneumatic sorting devices can be used. Therefore, a method according to the invention is preferred, wherein the separating in step e) is carried out by an automated apparatus. A method according to the invention is especially preferred, wherein the separating in step e) is made using a pneumatic sorting device, preferably an air-pressure pistol, and / or wherein the particles in step e) are sorted our pneumatically, preferably with an air-pressure pistol.

[0087] While it is possible to use a method of the present invention to obtain an aluminium secondary raw material composition with lower degrees of purities and / or higher amounts of specific impurities, it is most preferred to use the power of the method according to the invention to obtain comparably aluminium rich product compositions that can be used for high value applications, and that in particular comprise only minute amounts of a most relevant contaminants. By leveraging the benefits of the present invention, a method according to the invention is preferred, wherein the aluminium secondary raw material composition comprises 90 % or more, preferably 95 % or more, more preferably 98 % or more, most preferably 99 % or more, in particular 99,5 % or more, of aluminium, with respect to the mass of the aluminium secondary raw material composition.

[0088] Additionally or alternatively, a method according to the invention is preferred, wherein the aluminium secondary raw material composition comprises with respect to the mass of the secondary raw material composition: less than 1 % by mass, preferably less than 0,9 %, preferably less than 0,8 % of silicium, and / or less than 0,6 % by mass, preferably less than 0,5 %, preferably less than 0,4 % of iron, and / or less than 0,5 % by mass, preferably less than 0,4 %, preferably less than 0,3 %, more preferably less than 0,2 %, most preferably less than 0,1 % of copper, and / or less than 0,8 % by mass, preferably less than 0,7 %, preferably less than 0,6 % of manganese, more preferably less than 0,5 % and / or less than 0,8 % by mass, preferably less than 0,6 %, preferably less than 0,4 % of magnesium, and / or less than 0,4 % by mass, preferably less than 0,3 %, preferably less than 0,2 % of zinc.

[0089] In order to maximise the efficiency, the inventors of the present invention suggest that the mandatory steps of the method according to the invention can beneficially be combined with further established separation methods, that in particular allow for an efficient removal of very high / low density impurities (e.g. by wind sifting) or magnetic impurities, in particular iron. A method according to the invention is preferred, wherein the method comprises, preferably between step b) and d) and / or as part of step c) and / or as part of step d), preferably between step b) and d) and / or as part of step d), further processing steps, preferably for removing organic impurities, wherein the further processing steps are preferably selected from the group consisting of windsifting, magnetic separation, in particular eddy current separation, and hand sorting.

[0090] The high-quality aluminium secondary raw material composition that comprises aluminium in a high purity can beneficially be used to produce an aluminium product, wherein the aluminium product composition can be mixed with virgin aluminium or even be used as the entire raw material. Beneficially, the pure aluminium product obtained in the method according to the invention can be processed using established production methods, in particular by smelting the starting composition and the casting the resulting smelted composition.

[0091] The inventions also relates to a method for producing an aluminium product comprising the steps of the method for producing an aluminium secondary raw material composition from aluminium containing scrap composition, as well as the steps of: x) providing or producing a starting composition comprising or consisting of the aluminium secondary raw material composition, y) smelting the starting composition and casting the resulting smelted composition to obtain the aluminium product.

[0092] Preferred is a method according to the invention, wherein the aluminium product is an aluminium sheet, preferably an aluminium sheet for use in the production of vehicles, more preferably a car body sheet.

[0093] Hereinafter, the invention is described in more detail, wherein preferred embodiments of the invention are disclosed with respect to the figures. The figures show: Fig. 1a schematic visualization of the steps of a preferred method according to the invention in a first embodiment; and Fig. 2a visualization of the steps of a preferred method according to the invention in a second embodiment.

[0094] Fig. 1 and 2 visualize the steps of the method according to the invention in two preferred embodiments.

[0095] In both cases in the first process step 102 an inhomogeneous aluminium-containing scrap composition consisting of mixed end of life scrap, comprising in particular end of life vehicles, is conveyed into a single stage shredder. In an alternative example, instead of end of life vehicles also doors of end of life vehicles could be employed.

[0096] The inhomogeneous aluminium-containing scrap composition comprises a plurality of first scrap subvolumes consisting of a first metallic material with an aluminium content of 95 % or more, namely basically pure aluminium and aluminium rich alloys. Furthermore, the end of life vehicles also comprise a plurality of second scrap subvolumes consisting of different metallic materials with insufficient aluminium content, in particular steel and aluminium alloys with low aluminium content, for example as part of the engine block.

[0097] In the comminuting space within the shredder the end of life scrap is crushed by the crushing hammers of the shredder for comminuting the aluminium-containing scrap composition in step 104.

[0098] The process is conducted as an essentially continuous process wherein the predefined comminuting parameters for operating the shredder where initially adjusted to ensure that about 90 % of the first metallic material that is leaving the comminution unit ends up in particles with an equivalent sieve diameter in the range of 40 to 130 mm.

[0099] In the present example, the process is adjusted through the predefined comminuting parameters so that the mass fraction of particles with an equivalent sieve maximum diameter in the range of 40 to 130 mm varies in the range of about 75 to 95 % during operation, with the subtraction with a maximum equivalent sieve diameter in the range of 50 to 120 mm contributing up to about 90 %. At the same time, the combined mass fraction of particles with a maximum equivalent sieve diameter of less than 40 mm and of more than 130 mm makes up for about 5 to 25 %, with the smaller particle fraction typically contributing at least more than 3 to 4 % while the larger particles contribute at least more than 1 to 2 %.

[0100] In the process depicted in Fig. 1, in step 106 sieves are used to isolate a size-selected composition that basically consists of the intermediate fraction, i.e. the second particles, while the larger and smaller particles are discharged. In contrast, in the process of Fig. 2, no additional isolation step is conducted.

[0101] Before entering the optical detection device in step 108, the size-selected composition or the entire comminuted composition, respectively, are treated using eddy current separation for removing non metallic impurities before the optical analysis.

[0102] In step 108, the optical analysis is conducted using x-ray transmission, wherein the "gray tint" of the pieces is analyzed that can be correlated with the chemical composition of the particles. While in the process of Fig. 1, basically all particles of the size-selected composition are analysed, the process of Fig. 2 uses a camera and a suitable software to only analyse particles whose diameter is in the range of 50 to 120 mm, thus enabling a software-based focus on the intermediate size fraction.

[0103] Based on the observed "gray tint" obtained for the individual particles, those particles that are out of specification are removed from the respective composition in step 110 using an air-pressure pistol and discharged. The resulting composition is obtained as valuable aluminium composition that can be used as secondary raw material to produce aluminum products.

[0104] The respective production of aluminium products is indicated in Fig. 1 and 2 by the steps of 202 and 204 in that the material composition resulting from the preceding steps is smelted and subsequently casted to obtain car body sheets.Reference Signs

[0105] 102process step a) 104process step b) 106process step c) 108process step d) 110process step e) 202process step x) 204process step y)

Claims

1. Method for producing an aluminium secondary raw material composition from an aluminium-containing scrap composition, comprising the steps: a) producing or providing an aluminium-containing scrap composition, wherein the aluminium-containing scrap composition comprises: a1) a plurality of first scrap subvolumes consisting of a first metallic material with an aluminium content of 85 % or more, with respect to the mass of the first metallic material, and a2) a plurality of second scrap subvolumes consisting of a second metallic material with an aluminium content of less than 85 %, with respect to the mass of the second metallic material, b) comminuting the aluminium-containing scrap composition in a comminution unit to obtain a comminuted composition using predefined comminuting parameters, wherein the comminuted composition that is leaving the comminution unit comprises: i) first particles with an equivalent sieve diameter of less than 40 mm, ii) second particles with an equivalent sieve diameter in the range of 40 to 130 mm, and iii) third particles with an equivalent sieve diameter of more than 130 mm, wherein the predefined comminuting parameters are chosen so that 60 % or more of the first metallic material that is leaving the comminution unit is comprised by second particles, with respect to the mass of the first metallic material that is leaving the comminution unit, d) analysing particles of the comminuted composition with at least one optical detection device to detect at least one material information for the particles, wherein a mass fraction of more than [X] of the analysed particles are second particles, with respect to the combined mass of all analysed particles, wherein [X] is the mass fraction of the second particles in the comminuted composition, and e) separating particles for that the detected material information does not meet a predefined quality criterion to obtain an aluminium secondary raw material composition comprising particles for that the detected material information meets the predefined quality criterion.

2. Method according to claim 1, wherein the aluminium-containing scrap composition comprises scrap that is selected from the group consisting of construction wastes, production wastes, and end of life vehicle scrap and household waste.

3. Method according to any one of claims 1 or 2, wherein the aluminium-containing scrap composition comprises aluminium in an amount in the range of 2 to 55 %, with respect to the mass of the aluminium-containing scrap composition.

4. Method according to any one of claims 1 to 3, wherein the method comprises before step d) one or more separation steps for removing organic impurities and / or magnetic material from the comminuted composition5. Method according to any one of claims 1 to 4, wherein the aluminium-containing scrap compositions comprises second scrap subvolumes consisting of second metallic materials that are selected from the group consisting of aluminium alloys.

6. Method according to any one of claims 1 to 5, wherein the aluminium-containing scrap composition comprises second scrap subvolumes consisting of second metallic materials that are selected from the group consisting of iron and iron alloys.

7. Method according to any one of claims 1 to 6, wherein the comminuting is a single stage commuting.

8. Method according to any one of claims 1 to 7, wherein the comminuted composition that is leaving the comminution unit comprises with respect to the mass of the comminuted composition: i) first particles with an equivalent sieve of less than 40 mm in a combined mass fraction of 1 % or more, and / or ii) second particles with an equivalent sieve in the range of 40 to 130 mm in a combined mass fraction of 40 % or more, and / or iii) third particles with an equivalent sieve of more than 130 mm in a combined mass fraction of 0,2 % or more.

9. Method according to claim 8, wherein the comminuted composition that is leaving the comminution unit comprises with respect to the mass of the comminuted composition: i) first particles with an equivalent sieve of less than 40 mm in a combined mass fraction in the range of 2 to 20 %, ii) second particles with an equivalent sieve in the range of 40 to 130 mm in a combined mass fraction in the range of 65 to 97,5 %, and iii) third particles with an equivalent sieve of more than 130 mm in a combined mass fraction in the range of 0,5 to 15 %.

10. Method according to any one of claims 1 to 9, wherein the method comprises between steps b) and d) the step of c) separating first particles and / or third particles from the second particles of the comminuted composition to obtain a size-selected composition, wherein the size-selected composition comprises the second particles in a combined mass fraction of more than [X], with respect to the mass of the size-selected composition.

11. Method according to any one of claims 1 to 10, wherein the optical detection device is selected from the group consisting of optical detection device for x-ray analysis, infrared analysis, and laser-induced breakdown spectroscopy (LI BS).

12. Method according to any one of claims 1 to 11, wherein the material information is detected with the optical detection device with a spatial and / or temporal resolution to obtain a spatially and / or temporally resolved information profile of the analysed particles.

13. Method according to any one of claims 1 to 12, wherein the aluminium secondary raw material composition comprises 90 % or more of aluminium, with respect to the mass of the aluminium secondary raw material composition.

14. Method for producing an aluminium product comprising the steps of the method for producing an aluminium secondary raw material composition from aluminium containing scrap composition according to any one of claims 1 to 13, as well as the steps of: x) providing or producing a starting composition comprising or consisting of the aluminium secondary raw material composition, and y) smelting the starting composition and casting the resulting smelted composition to obtain the aluminium product.

15. Method according to claim 14, wherein the aluminium product is an aluminium sheet, preferably an aluminium sheet for use in the production of vehicles, more preferably a car body sheet.

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