Method and Apparatus for the Alloy-Dependent Sorting of Scrap Metal, in Particular Aluminum Scrap

Abstract

Disclosed is a method for sorting of scrap metal in which a composition analysis is carried out on a scrap fragment. Surface composition information about the local composition of the scrap fragment is determined, and associated volumetric composition information about the composition of the scrap fragment is assigned to the scrap fragment depending on the surface composition information determined by measurement and on a given assignment rule. Also disclosed is an apparatus for sorting scrap metal having a conveyor designed to convey a quantity of scrap fragments, an analysis device designed to carry out composition analyses on scrap fragments, and a control device designed to assign associated volumetric composition information about the composition of the scrap fragment. A composition analysis of a scrap fragment includes determining surface composition information about the local composition of the scrap fragment by measurement.

Claims

1. A method for the alloy-dependent sorting of scrap metal, in particular aluminum scrap, comprising: performing a composition analysis on a scrap fragment, wherein surface composition information about the local composition in a surface region of the scrap fragment is determined by measurement on the scrap fragment; and assigning associated bulk composition information about the composition of the scrap fragment in the bulk to the scrap fragment as a function of the surface composition information determined by measurement and a predetermined assignment rule.

2. The method according to claim 1, further comprising: providing a quantity of scrap fragments; respectively carrying out a composition analysis on a plurality of scrap fragments from the quantity of scrap fragments, wherein surface composition information about the local composition in a surface region of the respective scrap fragment is determined by means of measurement on the respective scrap fragment, and assigning associated bulk composition information about the composition of the respective scrap fragment in the bulk to the respective scrap fragment as a function of the surface composition information determined by measurement and a predetermined assignment rule.

3. The method according to claim 1, further comprising: sorting the scrap fragment as a function of the associated bulk composition information.

4. The method according to claim 1, further comprising: assigning associated bulk composition information to the scrap fragment as a function of the surface composition information determined by measurement and a predetermined assignment rule in that bulk composition information is selected from a plurality of predetermined pieces of bulk composition information as a function of the surface composition information determined by means of measurement and the predetermined assignment rule.

5. The method according to claim 4, further comprising: respectively assigning a predetermined piece of surface composition information to the predetermined piece of bulk composition information and the selection of the piece of bulk composition information from the plurality of predetermined pieces of bulk composition information takes place by a comparison of the measured surface composition information with the predetermined pieces of surface composition information.

6. The method according to claim 1, further comprising: determining in the composition analysis, surface composition information about the local composition in a surface region of the scrap fragment, wherein the surface region extends from the surface of the scrap fragment to a known depth, in particular to a depth in the range of 2-10 m.

7. The method according to claim 1, wherein the composition analysis comprises a spectroscopic analysis, in particular laser-induced breakdown spectroscopy (LIBS) or X-ray fluorescence analysis (XRF).

8. The method according to claim 1, wherein the surface composition information determined by measurement comprises values for the contents of at least two alloy components of the scrap fragment.

9. The method according to claim 2, further comprising: separating the scrap fragments before a composition analysis is performed on the scrap fragments.

10. An apparatus for the sorting of metal scrap, in particular aluminum scrap, preferably for carrying out the method according to claim 1, comprising: a conveyor configured to convey a quantity of scrap fragments; an analysis device configured to perform composition analyses of scrap fragments conveyed on the conveyor, wherein composition analysis of a scrap fragment comprises determination of surface composition information about the local composition in a surface region of the scrap fragment by means of measurement; and a control device which is configured to respectively assign associated bulk composition information about the composition of the scrap fragment in the bulk to the scrap fragments analyzed by the analysis device as a function of the surface composition information determined by measurement and a predetermined assignment rule.

11. The apparatus according to claim 10, further comprising a sorting device which is configured to sort scrap fragments as a function of the bulk composition information respectively assigned to the scrap fragments by the control device.

12. The apparatus according to claim 10, wherein the analysis device comprises a spectroscopic analysis device, in particular an analysis device for laser-induced breakdown spectroscopy (LIBS) or X-ray fluorescence analysis (XRF).

13. The apparatus according to claim 10, further comprising a separating device which is configured to separate scrap fragments before they are fed to the analysis device.

14. The apparatus according to claim 10, further comprising a detection device which is configured to detect the position of scrap fragments conveyed on the conveyor, wherein the control device is configured to control the analysis device and/or the sorting device as a function of the detected position of a scrap fragment.

15. The apparatus according to claim 10, wherein the control device is configured to control the implementation of: performing a composition analysis on each scrap fragment, wherein surface composition information about the local composition in a surface region of each scrap fragment is determined by measurement on each scrap fragment; and assigning associated bulk composition information about the composition of each scrap fragment in the bulk to each scrap fragment as a function of the surface composition information determined by measurement and a predetermined assignment rule.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0058] Further advantages and features of the method and the apparatus will become apparent from the following description of embodiments, in which reference is made to the accompanying drawings, in which:

[0059] FIG. 1 shows an embodiment of the device according to the invention,

[0060] FIG. 2 shows the analysis device of the apparatus of FIG. 1,

[0061] FIG. 3 shows the assignment of a bulk composition information,

[0062] FIG. 4 shows examples of measured depth-dependent composition information, and

[0063] FIG. 5 shows an embodiment of the method according to the invention.

DETAILED DESCRIPTION

[0064] FIG. 1 shows an embodiment of the apparatus according to the invention for the sorting of metal scrap, in particular aluminum scrap, in a schematic representation. The apparatus 2 comprises a separating device 3 and a conveying device 4 in the form of a conveyor belt, with which scrap fragments 6 separated by the separating device 3 may be conveyed through the apparatus 2. The conveyance of the scrap fragments 6 through the apparatus 2 is represented in FIG. 1 by the material flow 7 indicated by an arrow.

[0065] Furthermore, the apparatus 2 has an analysis device 8 which is configured to carry out composition analysis on the scrap fragments 6 conveyed on the conveyor 4. For this purpose, the analysis device 8 comprises a spectroscopic analyzer 10, which may be, for example, an analyzer for laser-induced breakdown spectroscopy.

[0066] With the analyzer 10, surface composition information about the local composition in a surface region of the analyzed scrap fragment 6 may be determined by means of a measurement. Such an analysis will be explained in more detail below in connection with FIG. 2.

[0067] Furthermore, the apparatus 2 has a control device 12, which is configured to control the apparatus 2. For this purpose, the control device 12 comprises, in particular, a microprocessor 14 and a memory 16 connected thereto, which contains instructions the execution of which in the processor effects the control of the apparatus 2.

[0068] The analysis device 10 is connected to the control device 12 via a data connection 18 in order to transmit the surface composition information of a scrap fragment 6 determined by the analyzer 10 to the control device 12.

[0069] Furthermore, the control device 12 is designed to select bulk composition information associated with the surface composition information, as a function of the surface composition information received via the data connection 18 and a predetermined assignment rule stored in the memory 16, and to assign the bulk composition information to the scrap fragment analyzed by the analyzer 10. The selection of the bulk composition information is explained in more detail below in connection with FIG. 4. The assignment of the bulk composition information to the respectively associated scrap fragments 6 may be effected, for example, by assigning an order corresponding to the order of the scrap fragments 6 to the bulk composition information. Since the scrap fragments 6 are separated by the separator 3 and are therefore conveyed successively in a specific order by the apparatus 2, unambiguous assignment may be achieved in this way.

[0070] The apparatus 2 also has a sorting device 20, which is configured to sort the scrap fragments 6 as a function of the respectively assigned bulk composition information. The sorting of the scrap fragments 6 is shown schematically in FIG. 1 by the division of the material flow 7 into two partial flows 22 and 24. If the material flow 7 contains, for example, scrap fragments of low-alloyed aluminum alloys with an Mg and/or Mn content of max. 0.5 wt.-% and high-alloyed aluminum alloys, for example, with a Mg and/or Mn content of more than 2 wt.-%, then sorting of the scrap fragments 6 from the material flow 7 may be effected by the sorting device 20, in which scrap fragments, whose associated bulk composition information indicates a low Mg and Mn content, are assigned to the first partial flow 22, and the remaining high-alloyed scrap fragments are assigned to the second partial flow 24.

[0071] In order to assign a scrap fragment 6 to one of the partial flows 22, 24, the sorting device 20 shown in FIG. 1 has a controllable flap 26 which may be moved between a closed position (continuous line) and an open position (dashed line). When the flap 26 is in the closed position, a scrap fragment 6 conveyed on the conveyor belt 4 is assigned to the partial flow 22. When the flap 26 is in the open position, however, the scrap fragment 6 passes to the second partial flow 24. The controllable flap 26 is just one simple example of a way to divide the material flow 7 selectively into the partial flows 22, 24. Other means for sorting the scrap fragments 6 may be provided instead. For example, the individual scrap fragments may also be assigned pneumatically to one of the two partial flows 22, 24 by being conveyed into the respective partial flow by a short, strong burst of air.

[0072] Furthermore, the apparatus 2 also has a detection apparatus 28 in the form of a camera, with which the position of scrap fragments 6 conveyed on the conveyor 4 may be detected. For example, a laser scanner may be used instead of a camera.

[0073] The operation of the apparatus 2 will now be described.

[0074] A quantity of scrap fragments 6 is introduced into the separating device 3 and separated there, so that the scrap fragments 6 get successively on the conveyor 4 in a fixed order and are transported with this order through the apparatus.

[0075] The separated scrap fragments 6 are successively detected by the detection apparatus 28, by what the order of the scrap fragments 6 is detected.

[0076] The individual scrap fragments are then analyzed in the analysis device 8, and the control device 12 selects associated bulk composition information on the basis of the surface composition information determined during the analysis and of the predetermined assignment rule, and assigns these to the respective scrap fragment 6. The assignment of the bulk composition information is carried out in the present case by assigning the detected sequence of the scrap fragments 6 to the bulk composition information.

[0077] In the sorting device 20, the scrap fragments 6 are then supplied as a function of the respectively assigned bulk composition information each to one of the two partial flows 22, 24. To this end and based on the sequence of scrap fragments 6 detected with the detection device 28, it is determined which scrap fragment 6 gets next to the flap 26 and the flap 26 is controlled as a function of the bulk composition information assigned to this scrap fragment 6, so that the scrap fragment is fed to the correct partial flow 22, 24.

[0078] In this way, effective separation of different aluminum alloys from the material flow 7 is possible. The separation based on the respective bulk composition information assigned to the scrap fragments avoids misinterpretations and thus permits clean sorting of the individual scrap fragments.

[0079] In FIG. 1, two partial flows 22, 24 are exemplified. Of course, the material flow 7 may also be divided into more than two partial flows.

[0080] The sorting device 20 is shown in FIG. 1 as a unit spatially separated from the analysis device 8. However, the sorting device 20 and the analysis device 8 may also overlap spatially. For example, the sorting of the scrap fragments 8 may take place immediately after the analysis.

[0081] FIG. 2 shows a schematic illustration of the analysis device 8 of the apparatus 2 from FIG. 1. The analyzer 10 in this embodiment is an analyzer for laser-induced breakdown spectroscopy. The analyzer 10 comprises a laser source 30, with which a scrap fragment 6 conveyed on the conveyor belt 4 may be acted upon by a pulsed laser beam 32. The incident laser beam 32 vaporizes a small volume 34 on the surface of the scrap fragment 6 and ionizes it into a plasma 36. This creates a corresponding crater in the scrap fragment surface. Upon the breakdown of the plasma 36, light 38 is emitted that is characteristic of the alloy elements contained in the bulk 34. The volume 34 or the crater corresponding to the volume have a conical shape in this exemplary embodiment. The cross-section of the crater or of the volume 34 thus decreases with depth, so that the light 38 is predominantly dominated by the uppermost layers of the volume 34.

[0082] The analyzer 10 has optics 40 to capture the light 38 and pass it via a light guide 42 to a spectrometer 44, with which the spectral distribution of the light 38 may be analyzed. An evaluation device 46 connected to the spectrometer then calculates the composition of the volume 34 from the measured spectral distribution. Since the laser beam 32 has only a certain penetration depth 48, which is, as a function of the adjusted laser power, typically in the range of 1 to 10 m, the evaluation device 46 delivers surface composition information 50, i.e. composition information about a near-surface volume of the scrap fragment material. The surface composition information 50 is labeled with a 0 for surface in FIG. 2 and contains contents of various alloy elements (Mg, Mn, Cu, etc.) in weight %. For apparatus 2, this surface composition information 50 is sent to the control device 12 via the data link 18 for further processing.

[0083] FIG. 3 schematically shows how the control device 12 assigns an associated bulk composition information to the surface composition information 50 measured by the analysis device 8.

[0084] First of all, the control device 12 receives in a first step 60 the surface composition information 50 measured by the analysis device 8.

[0085] In a second step 62, the control device 12 selects the associated bulk composition information 66 as a function of the surface composition information 50 and an assignment rule 64 stored in the memory 16. For this purpose, the assignment rule 64 in the present example comprises a table in which to a plurality of alloy regions for the surface composition information 68a, 68b, etc. an associated alloy region for the bulk composition information 70a, 70b is assigned in each case. The alloy regions shown numerically in the figure are exemplary.

[0086] The control device 12 compares the surface composition information 50 with the alloy regions for the surface composition information 68a, 68b and selects therefrom the appropriate alloy region for the surface composition information, which is the alloy region 68a in the present example. The alloy region for the bulk composition information 70a associated with this alloy region then represents the bulk composition information 66 assigned to the surface composition information 50, by which the sorting device 20 is controlled.

[0087] By selecting an associated bulk composition information 66 for the surface composition information 50 and controlling the sorting device 20 as a function of the bulk composition information 66 instead of the surface composition information 50, it is considered that the composition determined by the analysis device 8 on the surface of the scrap fragment 6 deviates from the actual bulk composition of the scrap fragment 6 due to segregation and diffusion effects. This allows a more reliable alloy-specific sorting of the scrap fragments based on the volumetric composition.

[0088] To determine the assignment rule, e.g. for a scrap fragment to be sorted, it is preferably examined which bulk compositions of a scrap fragment are reflected in which surface compositions. For example, individual sample fragments may be taken from a quantity of scrap fragments, such as a scrap quantity to be sorted, before being fed to the apparatus 2, for which individual sample fragments the surface composition, on the one hand, and the volumetric composition, on the other hand, are analyzed. The assignment rule 64 may then be defined from the relationships determined in this analysis between the surface composition and the bulk composition.

[0089] The analysis of the sample fragments may be investigated, for example, by glow discharge optical emission spectroscopy (GDOES). In this method, the sample fragment is used as a cathode in a DC plasma.

[0090] Through cathode sputtering, material is removed successively layer by layer from the surface of the sample fragment, wherein the removed atoms in the plasma emit characteristic light, which may be examined spectroscopically. In this way, the composition of the samples may be analyzed as a function of the depth.

[0091] FIG. 4 shows a diagram with measurement results of GDOES analysis on two scrap fragments. The diagram shows the depth-dependent composition of the scrap fragments using the example of the alloying element Mg. The abscissa indicates the depth in m, i.e. the distance from the surface of the scrap fragment to the volume of the scrap fragment. The ordinate indicates the local Mg content in weight % at the corresponding depth.

[0092] The first analyzed scrap fragment consisted of an AA5XXX type aluminum alloy. The horizontal line (a) shows the average Mg content of the scrap fragment, which was determined by optical emission spectroscopy (OES). In the OES, the sparks penetrate deeper into the material and thus provide a value that corresponds to the average composition. Typically, a very accurate value for the bulk composition can be measured by an OES. The measurement curve (b) shows the depth-dependent Mg content of the scrap fragment determined by GDOES.

[0093] The second analyzed scrap fragment consisted of an AA6XXX type aluminum alloy. The horizontal line (c) in turn shows the average Mg content of the scrap fragment determined by optical emission spectroscopy (OES). The curve (d) shows the depth-dependent Mg content of the scrap fragment determined by GDOES.

[0094] It may be seen from the diagram that the Mg content directly at the surface of the scrap fragments (at 0-approx. 0.5 m) is greatly increased by segregation and diffusion effects and is clearly above the respective average Mg content. At greater depth, the Mg content drops sharply and is even below the average Mg content in the investigated depth range of approx. 0.5 to 5 m, since Mg has diffused from here to the surface.

[0095] The measurement results shown in FIG. 4 may be used, for example, to define a corresponding assignment rule 64, for example for a scrap delivery to be sorted. In particular, it may be deduced from the diagram which Mg content in the bulk for certain scrap fragments corresponds to a specific Mg content of a surface composition information.

[0096] By integrating or averaging the depth-dependent Mg content from curve (b) or (d) in the depth range from 0 m to the penetration depth 48 of the laser beam 32, the Mg content may be determined, which Mg content results from the measurement with the analysis device 8 shown in FIG. 2 at the volume content along the line (a) or (c). The penetration depth 48 of the laser beam 32 depends essentially on the laser power and is thus known at a fixed laser power. For example, if the penetration depth 48 is set to 5 m by adjusting the laser power, the Mg value of surface composition information may be calculated in particular by averaging the contents between 0 and 5 m from the GDOES analysis. Preferably, the averaging or integration is carried out in a weighted manner in order to be able to take into account the footprint of the laser beam and/or the shape of the crater created by the laser beam in the scrap fragment surface. For example, in the cone-shaped crater illustrated in FIG. 2, near-surface contents are preferably weighted correspondingly more.

[0097] By means of these and corresponding analyses for further alloy elements, the alloy regions for the surface composition information 68a, 68b, etc., and the associated alloy regions for the bulk composition information 70a, 70b, etc. of the assignment rule 64 may thus be determined.

[0098] The diagram in FIG. 4 also shows that direct use of the Mg contents measured by the analysis device 8 to control the sorting device 20 without taking into account the assignment rule 64 would lead to considerable misinterpretations regarding the composition of the scrap fragments.

[0099] FIG. 5 shows an exemplary embodiment of a method according to the invention using the apparatus 2 shown in FIG. 1.

[0100] In a first step 80 of the method, scrap fragments 6 are supplied by the conveyor 4 to the analysis device 8 and there subjected to a composition analysis. For this purpose, the individual scrap fragments are subjected to a pulsed laser beam 32 by the analysis device 10, and respective surface composition information 50 is determined from the resulting light emission.

[0101] In a second step 82 of the method, the control device 12 selects an associated bulk composition information 66 for each surface composition information 50 by means of the assignment rule 64 and assigns this to the respective scrap fragment 6.

[0102] In a third step 84, the control device 12 controls the sorting device 20 so that the respective scrap fragment 6 is sorted as a function of the bulk composition information 66, i.e. in the present example it is assigned to one of the two partial flows 22 or 24.

[0103] As may be seen from the exemplary embodiments described above, an improved alloy-specific sorting of scrap fragments may be achieved with the described device and with the described method.

[0104] All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0105] The use of the terms a and an and the and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms comprising, having, including, and containing are to be construed as open-ended terms (i.e., meaning including, but not limited to,) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., such as) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0106] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.