Process and Apparatus for Sorting Reusable Pieces of Raw Material

• US 20170261437A1
• Filed: 09/10/2015
• Published: 09/14/2017
• Est. Priority Date: 09/11/2014
• Status: Active Grant

• Current Assignee: Proassort GmbH
• Original Assignee: Proassort GmbH
• Inventors: Buchter, Edwin, Barkhausen, Winfried, Pillkahn, Hans-Bernd
• Granted Patent: US 10,641,712 B2
• Time in Patent Office: Days
• CPC Class Codes: B07C 2501/0054 Sorting of waste or refuse
• CPC Class Codes: B07C 5/342 according to optical properties, e.g. colour according to radiation transmittivity B07C5/3416
• CPC Class Codes: B07C 5/3427 by changing or intensifying the optical properties prior to scanning, e.g. by inducing fluorescence under UV or x-radiation, subjecting the material to a chemical reaction
• CPC Class Codes: G01J 3/443 Emission spectrometry
• CPC Class Codes: G01N 2021/845 Objects on a conveyor
• CPC Class Codes: G01N 21/718 Laser microanalysis, i.e. with formation of sample plasma
• CPC Class Codes: G01N 21/84 Systems specially adapted for particular applications
• CPC Class Codes: G01N 2201/06113 Coherent sources; lasers

Abstract

The invention relates to a process and an apparatus for sorting reusable raw-material pieces (5) which are moved continually in conveying direction (2) by a transport means (1), where the chemical composition of the raw-material pieces (5) is analyzed by laser-induced breakdown spectroscopy (LIBS) and automated sorting of the raw-material pieces (5) is implemented depending on the composition found, where the raw-material pieces (5) in a first step are subjected to a plurality of first laser pulses (6) in order to remove surface coatings and/or contaminants from the raw-material pieces (5), and in a second step, one or more second laser pulses (7) are directed at those locations of the raw-material pieces (5) from which the surface coatings and/or contaminants have been removed, with exposed material of the raw-material pieces (5) being converted by the second laser pulses (7) into a plasma, where the laser (3) used for the first and second laser pulses (6, 7) is the same, and the area of the raw-material pieces (5) over which the first laser pulses (6) are moved and which is freed from surface coatings and/or contaminants is greater than the area of the raw-material pieces (5) that is embraced by the second laser pulses (7), the focal diameter and the focal point of the laser beam being kept constant between the first and second laser pulses (6, 7). In this way it is possible, utilizing only one laser, to achieve undistorted analysis of the composition of the raw-material pieces (5) and to perform sorting in dependence on said analysis.

Claims

1. A process for sorting reusable raw-material pieces (5) which are moved continually in a conveying direction (2) by a transport means (1), where the chemical composition of the raw-material pieces (5) is analyzed by laser-induced breakdown spectroscopy (LIBS) and automated sorting of the raw-material pieces (5) is implemented depending on the composition found, where the raw-material pieces (5)

in a first step are subjected to a plurality of first laser pulses (6) in order to remove surface coatings and/or contaminants from the raw-material pieces (5), and

in a second step, one or more second laser pulses (7) are directed at those locations of the raw-material pieces (5) from which the surface coatings and/or contaminants have been removed, with exposed material of the raw-material pieces (5) being converted by the second laser pulses (7) into a plasma,

where the laser (3) used for the first and second laser pulses (6, 7) is the same,

wherein the area of the raw-material pieces (5) over which the first laser pulses (6) are moved and which is freed from surface coatings and/or contaminants is greater than the area of the raw-material pieces (5) that is embraced by the second laser pulses (7), the focal diameter and the focal point of the laser beam being kept constant between the first and second laser pulses (6, 7).

2. The process as claimed in claim 1, characterized in that wherein the area of the raw-material pieces (5) which is freed from at least one of said surface coatings and said contaminants and is greater by at least the focal diameter and positional tolerances than the area of the raw-material pieces (5) that is embraced by the second laser pulses (7).

3. The process as claimed in claim 1, wherein the areas of the raw-material pieces (5) that are to be freed from at least one of said surface coatings and said contaminants are embraced singly or multiply by the first laser pulses (6) depending on the nature and thickness of at least one of the surface coatings and the contaminants.

4. The process as claimed in claim 1, wherein the first laser pulses (6) are guided along at least two dimensions over the areas of the raw-material pieces (5) that are to be freed from at least one of said surface coatings and said contaminants.

5. The process as claimed in claim 1, wherein the focal diameter of the laser beam is between 60 and 140 μ

m.

6. The process as claimed in claim 1, wherein a pulse length of the first and second laser pulses (6, 7) is 20-200 ns.

7. The process as claimed in claim 1, wherein the plasma generated by the second laser pulses (7) is a thermal plasma.

8. The process as churned in claim 1, wherein the laser (3) is a solid-state laser.

9. The process as claimed in claim 1, wherein the laser is a fiber laser.

10. The process as claimed in claim 1, wherein the raw-material pieces (5) are moved with a speed of >

0.1 m/s in the conveying direction.

11. The process as claimed in claim 1, wherein the raw-material pieces (5) are steel-scrap pieces.

12. The process as claimed in claim 11, wherein the steel-scrap pieces are galvanized steel-scrap pieces.

13. The process as claimed in claim 1, wherein the raw-material pieces (5) are nonferrous-metal-scrap pieces.

14. The process as claimed in claim 1, wherein the first laser pulses (6) are directed at raw-material pieces (5) which are further back in the conveying direction (2), and the second laser pulses (7) are directed at raw-material pieces (5) which are further forward in the conveying direction (2), there being a continual alternation between the subjection of raw-material pieces (5) that are further back in the conveying direction (2) to first laser pulses (6) and of raw-material pieces (5) that are further forward in the conveying direction (2) to second laser pulses (7).

15. An apparatus for implementing a process as claimed in claim 1, having

a laser (3) which is capable of generating first laser pulses (6) for detaching surface coatings and contaminants from raw-material pieces (5), and second laser pulses (7) for converting exposed material of the raw-material pieces (5) into a plasma,

a spectrometer for analyzing the light emitted by the plasma,

transport means (1) for moving the raw-material pieces (5) in the conveying direction (2),

a control unit which controls the pulse energy, pulse duration, and pulse frequency of the laser (3) and which moves the first laser pulses (6) over an area of the raw-material pieces (5), and frees said area from at least one of said surface coatings and said contaminants, said area being greater than the area of the raw-material pieces (5) that is embraced by the second laser pulses (7), and which keeps constant the focal diameter and the focal point of the laser beam between the first and second laser pulses (6, 7),

and

a sorting unit which automatedly assigns the raw-material pieces (5) to one or more target fractions depending on the composition found.

16. The process as claimed in claim 1, wherein the pulse length of the first and second laser pulses (6, 7) is 60-120 ns.

17. The process as claimed in claim 1, wherein the raw-material pieces (5) are moved with a speed of >

2 m/s in the conveying direction.