Plastic Waste Recycling: From Shredder to Recycled Pellets

Every production site accumulates start-up waste, off-spec material and rejects. Instead of throwing them away, they can be recycled into secondary raw material, which reduces costs and the environmental load. We review what equipment is needed for this and how it works.

Stages of recycling bulky waste

1. Shredder — a size-reduction machine with triangular knives for pipes, sprues and melt purgings.
2. Crusher — further reduces the material after the shredder to a state suitable for subsequent processing.
3. Pelletizer — turns the crushed material into recycled pellets.

Film recycling

Film is usually shredded first and then processed on a pelletizer. Some pelletizers are equipped with a built-in unit that allows film to be fed as is, without prior size reduction.

How a pelletizer works

All pelletizers work on the extrusion principle. The raw material goes through the loading hopper into the screw and barrel, which is heated by ring heating elements, and leaves as a melt through a die with holes. The following process depends on the pelletizer type.

Pelletizer types

• Strand pelletizers (from English strand): the melt emerges as strands, is cooled in a water bath and then cut.
• Die-face cutting: the melt is cut immediately at the die exit.
• Air-cooled: the pellets are cooled by an air stream.
• Water-ring cutting: the pellets are cooled by a continuous flow of water.

Water-ring cutting cycle

The cut pellets, together with water, go along a chute into a centrifuge for preliminary drying, then onto a vibrating table where they are sorted by size. Through screens of the required mesh the pellets enter the pneumatic conveying screw, then go to the storage silo, and from there are packed into containers.

Where recycled pellets are used

Recycled pellets are used wherever the technical specification allows: in injection molding, extrusion of films, sheets, pipes and other products.

What to read and see next

• Recycling lines in the catalog.
• Industrial shredders and crushers.
• Washing and pelletizing line.

A Plastic Expert manager will help you select equipment for your waste: 8 (800) 700-49-01.