The Definitive Guide to PET Bottle Recycling Washing Lines

Stage 1: Bale Breaking

The process begins with compressed bales of PET bottles being fed into a balenbreker. This machine aggressively de-compacts the bales, separating the bottles to ensure a consistent and even flow into the rest of the washing line.

Key Benefit: Creates a steady, manageable material stream, preventing clogs and maximizing throughput.

Stage 2: Pre-Sorting & De-Labeling

Here, large, obvious contaminants (like rocks, metals, and non-PET plastics) are removed. This is often followed by a mechanical de-labeler, which uses friction to tear off over 80-90% of the bottle labels before the washing process even begins.

Key Benefit: Protects downstream equipment like granulators from damage and improves the efficiency of the washing stages.

Stage 3: Wet Grinding / Crushing

The whole bottles are conveyed into a high-speed granuleermachine or crusher. This machine, often operating with water, cuts the bottles into uniform flakes (typically 12-16mm). The water helps pre-clean the material and reduces wear on the blades.

Key Benefit: Grinding into flakes dramatically increases the surface area, making the cleaning process far more effective and efficient.

Stage 4: Label & Dust Separation

An air classifier, often called a Zig-Zag Separator, is used to remove the remaining label fragments. A cyclone system generates a current of air that blows the lighter paper and plastic label pieces away from the heavier PET flakes.

Key Benefit: Efficiently removes low-density contaminants, significantly purifying the flake stream.

Stage 5: Hot & Cold Washing

This is the heart of the cleaning process. The flakes undergo several washing cycles:

• Heet wassen: Flakes are washed in a hot washer with water heated to 85-95°C, typically with a caustic soda solution. This powerful step sterilizes the material, dissolves all remaining glue, and removes oils and greasy residues.
• Friction Washing & Rinsing: High-speed friction washers scrub the flakes against each other, and subsequent rinsing tanks wash away any remaining detergents and contaminants.

Key Benefit: The hot wash is critical for dissolving tough adhesives and ensuring the highest level of cleanliness for the rPET flakes.

Stage 6: Float-Sink Separation

The mixed flakes enter a float-sink tank filled with water. This stage brilliantly uses the simple physics of density. The heavier PET flakes (density ~1.33 g/cm³) sink to the bottom, while the lighter PP/PE caps and rings (density <1 g/cm³) float to the top and are skimmed off.

Key Benefit: This is the most crucial step for separating different plastic types, achieving a PET purity level of over 99%.

Stage 7: Dewatering & Drying

Moisture must be almost entirely removed. This is a two-step process:

• Mechanical Dewatering: A centrifugal (spin) dryer first removes the bulk of the water, quickly reducing moisture content to around 2-3%.
• Thermisch drogen: The flakes then pass through a hot air thermal drying system, which reduces the final moisture content to below 1%.

Key Benefit: Dry rPET flakes are stable for storage and meet the strict requirements for downstream processing like pelletizing or sheet extrusion.

Stage 8: Final Quality Control & Packing

In top-tier lines, the finished flakes pass through a final “flake sorter” to remove any remaining off-color or non-PET flakes. A dust removal system ensures a clean final product before it’s packed into large jumbo bags, ready for sale or internal use.

Key Benefit: Guarantees the highest possible product quality, commanding a premium price in the market, especially for bottle-to-bottle recycling.