Wednesday, December 28, 2011: 03:05:58 PM

PET Recycling: Sorting Systems

The S+S Flake Purifier performs up to three sorting tasks (plastic types, metal and colour) in one go.

S+S Separation and Sorting Technology GmbH presents sorting systems for PET recycling.
The big challenge in PET recycling is that bottles or flakes must be separated to provide unmixed and contaminant-free output materials. S+S has developed solutions that separate contaminants from PET material flows and sort these material flows into unmixed fractions. Using state-of-the-art sorting technology that is able to separate huge mass flows into various secondary raw materials in a very short time is an important element for an economically efficient recycling process.

PET recycling has become an essential factor for the saving of crude oil and thus for the reduction of CO2 pollution. Every recycled PET bottle has a crude oil equivalent of 25 gram. In view of the global recycling quantity of 4.53 million tonnes of PET bottles per year, this means a saving of crude oil of approximately 3.7 million tonnes.
Even packaging that at first glance may seem to be ecologically unfavourable, such as non-returnable PET bottles, due to its recycling thus becomes ecologically valuable packaging that in its eco-balance is in no way inferior to competitors like returnable glass bottles. More than 80 per cent of the PET recycling companies in Germany, and more than 60 percent of the European recycling companies use polymer, metal and colour separators for the reliable separation of contaminants.

Polymer separators with multi-spectral sensors are used to detect contaminants and plastic types. In PET recycling these systems in fully-automatic operation separate unwanted plastic types from the PET material based on the infrared absorption of the various plastic types. They for example remove PVC contents or bioplastics such as PLA, which otherwise would considerably reduce the quality of the recycled material or would even make high-quality material recycling impossible. Against the background of an increasing use of ‘bio bottles’ that up to 100 per cent are made of vegetable raw materials and from the outside cannot be distinguished from conventional PET bottles, this is an important sorting criterion.

Contaminant separators with inductive sensors reliably remove all kinds of metals from mixed PET materials. While conventional metal separators can separate certain types of metal like stainless steel only to a very limited extent, the contaminant separators perform this separation task without any problems - irrespective of the type of metal.

Colour separators with optical sensors in fully automatic operation separate off-colour contaminations (e.g. coloured from clear, non-transparent bottles) from a PET material flow. Optical inspection is performed by high-speed cameras. The optically relevant information is evaluated, and the wanted or unwanted colour fractions are correspondingly separated.

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