High-performance recycling system for waste plastics using raman identification

Abstract

Raman spectroscopy has potential for application to waste plastic recycling when large-scale, accurate sorting processes are required. We developed a high-speed Raman identifier with a 3-ms measuring time. This identifier was successfully integrated with an on-line sorting system in a shredded plastic recycling plant. A practical-scale (200-600 kg/h) demonstration facility was constructed with 50 Raman apparatuses on a 30-cm-wide conveyor (speed: 100 m/min). This facility included preprocessing using specific gravity classification and putty removal. The Raman identification system was used to control air jets to sort polypropylene, polystyrene and acrylonitrile-butadiene-styrene copolymer with high accuracy from shredded plastics from post-consumer electrical appliances. Raman plastic identification can also provide solutions to problems at recycling sites such as the detection of brominated flame-retardants and the identification of black plastics.