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High quality plastic materials from electronic wastes by use of combined identification methods and new handling technologies

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A recycling process which is capable of delivering high quality plastic materials from electronic wastes has to include sophisticated identification methods. For this issue it was necessary to combine different identification methods to characterise plastic wastes with respect to matrix material, flame retardants, fillers and additives, and also to develop new handling technologies for an effective operation of the complete system. The identification methods used are: -Laser pulse thermography (TIR). -Mid-infrared spectroscopy based on AOTF-technology. -Laser induced plasma spectroscopy (LIPS). All three identification units were improved with respect to optimised identification results on to an identification handling technology (ID-prototype line) which had to be developed. The Mid-Infrared Acousto-Optic Tunable Filter (MIR-AOTF) Spectrometer got an illumination system, which enhances the reflected light and improves the signal quality. Besides, it is shielded in a sealed housing to withstand the harsh industrial environment. For the Thermal Impulse Response (TIR) System, the laser system was improved by use of a new laser module giving less power but with an increased stability. A new cooling system was integrated to augment the overall stability of the system. Another aspect was the improvement of the identification algorithms. For the Laser Induced Plasma Spectroscopy (LIPS), optimisations concerning hardware and software were made. Especially, the comprehensive analysis of all available spectral lines was a main focus of work. The adaptation of the identification methods by a control unit took into account the status of the handling line by control sensors (speed and position of parts), acquiring the results of the identification methods and combining them for monitoring and deriving a decision for the ID-line. Surface Cleaning is necessary to eliminate layers like lacquers or labels, which could cause false identification results, and to generate surface properties, which enable a good signal acquisition. Feeding, simulation and sorting to the ID-unit includes positioning of bigger parts on a conveyor belt by hand, feeding of the parts onto a pallet, fixing the parts with a pneumatic piston system and moving with constant velocity, installation of the identification systems at the belt and observing the plastic parts through the gap of the pallet. The ID-line incorporating the AOTF-MIR-system and the LIPS-system was installed at first at Mirec, Eindhoven and later at Gaiker, Bilbao. Systematic studies with more than 500 plastic covers of TV-sets and computer monitors were run to characterise the performance. The ID-line is able to identify and sort the most important plastics of various sizes from electronic products independently of the colour. Metallic additives are identified directly and the halogen flame retardants indirectly by their synergist antimony trioxide. The throughput and the purity depend on the conditions of operation and levels of reliability whereas a transport of the plastic parts was realised at 0.14 m/s and purities obtained between 85 to 100 %. The Thermal Impulse Response system which can also contribute to the identification as a redundant information, was completed but not tested at the ID and sorting line. The quality control enabled the property investigation of re-processed materials derived from the ID-line and showed that acceptable recycled plastics could be obtained. The sorted material was analysed and the properties successfully tested by investigation of re-granulated, re-processed plastics. The results would enable an increase of the recycling quote of electronic and electric equipment of at least 5-10 % if the ID-line is applied in practice.

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