Sustainable process engineering:Highest quality PET recycling

ProTec has developed a "bottle-to-bottle" process for converting PET bottle flake into rPET pellets which combines high economic viability with low energy consumption. Final post-condensation and decontamination of the processed pellets in ProTec's tumble reactor, the keystone of the entire recycling line, results in high-quality rPET which is approved for food contact. Recycling saves large quantities of PET virgin material, conserves resources, cuts energy consumption and CO2 emissions and so reduces environmental impact.

Complete recycling lines

ProTec designs and supplies complete Industry 4.0 capable PET recycling lines using washed flakes as starting material. The multistage process starts by drying the flakes in a two-stage dryer and decontaminating them in a first step. The predried flakes are melted in a twin screw extruder, mechanical contaminants are removed with a screen changer and vacuum degassing removes further volatile foreign substances. Pelletization in an underwater pelletizer is followed by inline conversion into the partially crystalline state, achieved solely using the melting heat of the pellets. The partially crystalline PET pellets pass into an insulated weighing hopper, from which they are discharged in batches to fill the ProTec tumble reactor. Once completely decontaminated and post-condensed in the reactor, the material is finally conveyed as hot, predried pellets directly into preform production or into a cooling hopper and from there the rPET is transferred into Big Bags, storage hoppers or directly into a tanker truck. Waste heat from the cooling hopper can be returned to the process.

Suitable for food contact

rPET obtained using the tumble reactor has an acetaldehyde content of ≤ 1 ppm and overall material properties like those of PET virgin material. rPET has been demonstrated to be suitable for direct food contact, the recycling process having obtained EFSA (European Food Safety Agency) and FDA (Food and Drug Administration/USA) approvals. An IV value of 0.8 dl/g is generally required for example for producing preforms for the production of PET bottles. Still higher IV values of ≥ 1.2 dl/g, as required for engineering applications, can be achieved by treating polyesters in the tumble reactor.

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