Pet

A bale of pressed bottles may contain also: 

HDPE bottles

Aluminum cans

Little glass (normally broken already)

Little PS in form of trays, cups and sticks.

PVC bottles 

For Bales of already sorted bottles, the picture doesn’t change much, some PVC bottles will still be present, but no glass,  and sorting colours will be much easier.

 

With positive sorting, operators standing beside a conveyor belt pick up every plastic bottle and toss it on another conveyor going to granulator, while with negative sorting, personnel should care about other materials. Aluminum cans are easy to identify and pieces of the metal if present can be separated manually or with an Eddy current type detector. PS items do not have a shape of a bottle and are easily removed. If PS labels will be present on bottles, they can be removed, after granulation, with one or more air separation systems. Pieces of glass will be removed in the pre-washing phase while HDPE bottles are no concern at all.

 

After the manual sorting, automatic separation by one or two NIR detector which can recognize nearly all polymers, also by colour, is used to separate PET bottles. As the efficiency of this type of detector is 95-96% if PVC is present and not completely removed, it will be reasonable to add an X-RAY detector for PVC only, at the end. 

 

At this point we have our bottles separated, by type of plastic, colour, metals and foreign objects free, ready to go into granulation


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