„Tracer-Based-Sorting“ in der Verpackungs-Abfallwirtschaft

Quality Aspects in the Compounding of Plastic Recyclate

“…The sorting performance of NIR sorters is limited by high belt speeds and the associated short measuring times, as well as by overlapping, black, dirty, wet, or fully printed packaging surfaces, and by labels that cover more than 30% of the packaging and where the polymers differ [13,14]. Further sorting tasks where NIR sorters are reaching their limit or are not capable are the differentiation of food and non-food packaging [33], the sorting of brand-specific materials for the implementation of extended producer responsibility [34], or the identification of certain plastic types of the most important polymers, such as polyethylene terephthalate amorphous/glycol-modified (PET-A/G) and polypropylene homopolymer/copolymer (PP-H/C) [21] or certain multilayer packaging [35].…”

Challenges and Solutions for Plastic Packaging in a Circular Economy

“…In state of the art sorting plants, LWP is sorted based on the materials' inherent physical properties such as density, color, absorption properties, conductivity, or product geometry [15]. For sorting of main polymers such as PET, PS, or PE, mainly NIR sorters are applied, of which up to 50 are used in a single sorting plant with a throughput of hundreds of thousand tons [16]. Due to overlapping, black, dirty, wet, or fully printed packaging surfaces, NIR sorting is limited in its sorting performance [14].…”

“…Based on this plant, an additional horizontal belt identification system was designed and built. Additional sorting tests [16] were performed in a conventional NIR sorter ''Steinert Unisort'', with standard Steinert software for assessment and an additional integrated laser excitation optic. The line focus of the laser was adjusted to cover the standard camera (equipped with a filter to absorb laser light) measuring area for reflection spectrum measurements.…”

“…Colored pigments affect the intensity of tracer fluorescence, e.g., by absorption, so packaging material colors are relevant for TBS. Preliminary research [16] showed that light colors such as yellow and white are advantageous for tracer emission, while black and dark materials have a lower quantum yield rate but with a still detectable tracer emission. Fig.…”

“…Similar effects of handling-related impurities due to geometric conditions apply to all separation processes using compressed air nozzles for separation. They are, e.g., known for the separation of round or moving objects [16].…”