Recycling feedstock is first unloaded and processed into handleable particles. Clean, clear PET bottle waste is cut into small sized flakes. Waste blocks from the polymerization process are passed through a grinder. Post-industrial textile waste are passed through a shredder to produce “popcorn”. This solid-form processing is important for not only solids handling functions, but also to maximize surface area for quicker dissolving in the partial glycolysis stage.

The recycling feedstock undergoes partial glycolysis in the Melter Reactor to produce oligomer. The recyclate next goes through a filtration stage, then onward in the process.

Above 30% recycle content production, there is a drastic reduction in the reaction rate, affecting the production capacity of the Polymerization unit and the color of the polyester product. To address these issues, the recyclate from the Partial Glycolysis step is subjected to end group optimization, wherein the OH and COOH groups are balanced using KTS’s’ proprietary technology, before passing the recyclate on to the Polymerization step.

Depending upon the recycle content, the recyclate is fed directly from the Partial Glycolysis Melter System or via KTS’s End Group Optimisation System into the inlet of the pre-polymerizer reactor. In partial recycle applications, the recycle stream is injected to the main oligomer line from the esterification reactor, otherwise the material is directly fed to the pre-polymerization reactor for the 100% recycle case. The polymerization process is then carried out the same as for virgin polyester production.