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2004
Conference Paper
Titel
Fast identification of light metal alloys by laser-induced breakdown spectroscopy for material recycling: Development of a demonstrator for automatic sorting of aluminium scrap
Abstract
Due to the rising demand and use of light metal alloys, e. g. primary and secondary aluminium in the automobile industry, the recycling of the accumulating scrap metals becomes more important. Energy savings of up to 95 % compared with the production of primary aluminium and corresponding savings of expenses are achievable. However, producing high-quality secondary aluminium is only possible if the scrap is available in presorted fractions of cast and wrought alloys. In a German joint national R&D project carried out by ILT1, I.A.R.2 and 5 companies an efficient automatic sorting method for cast and wrought alloys is developed. The aspired throughput of the sorting method amounts to 2 - 4 t/h of sorted alloys with purities better than 95 wt.-% and a minimum output of 90 wt.-%. The technical approach for fast sorting of light metal alloys is based on a combination of Image processing, laser-based geometry detection and Laser-Induced Breakdown Spectrometry (LIBS). The image processing and geometry detection provide colour and form information of every scrap particle moving on a conveyor belt at a speed of 2 - 4 m/s. On the basis of this information a pulsed laser beam is controlled to one or more positions at the surfase of every moving scrap particle in order to determine the individual chemical composition. For fast identification of aluminium alloys by LIBS a 100 Hz solid-state laser and a Paschen-Runge spectrometer with photomultipliers are applied. A decision for sorting is taken in real-time using the acquired geometric and spectroscopic information and subsequently the scrap particles are separated automatically in three or more fractions. First results concerning the influences of several measuring parameters on the LIBS analysis will be presented.