Problemen met een PET-waslijn oplossen

Een moderne Waslijn voor PET-flessen is a robust and reliable system, engineered for continuous, high-throughput operation. However, the realities of day-to-day production mean that even the best-run plants can encounter operational challenges. Proactively identifying and resolving these issues is key to maintaining efficiency, ensuring final product quality, and protecting your profitability.

This practical guide addresses three of the most common problems faced by plant managers—blockages, high moisture content, and odours—providing a framework for diagnosis and effective solutions.

1. Problem: Material Blockages and Inconsistent Flow

A smooth, consistent flow of material is the lifeblood of a recycling line. Any interruption can lead to costly downtime and reduced output.

Common Causes & Diagnosis:

• Ineffective Bale Breaking: If the bale breaker is not thoroughly separating the compressed bottles, large clumps can cause blockages in subsequent hoppers and conveyors.
• Granulator Overload: Feeding material into the granulator faster than it can be processed is a primary cause. This can also be exacerbated by dull or improperly gapped blades, which shred less efficiently and create more friction.
• Conveyor Speed Mismatch: A conveyor feeding a machine faster than its processing capacity will inevitably lead to overflow and blockages.
• Wet Material Adhesion: In later stages, particularly in cyclones and pipework, flakes with excessive moisture can stick to surfaces, accumulating over time and causing a blockage.

Solutions & Preventative Measures:

• Operator Training: Ensure staff are trained to feed bales at a steady, appropriate rate and to recognise the signs of an overloaded granulator.
• Blade Maintenance Schedule: Implement and adhere to a strict schedule for checking, sharpening, and rotating granulator blades. Sharp, correctly set blades require less power and process material more smoothly.
• System Calibration: Regularly verify that the speeds of all conveyors are correctly synchronised with the processing capacity of the machinery they feed.
• Inspect Drying Efficiency: If blockages occur post-washing, audit the dewatering and drying stages to ensure material is not being conveyed with excessive moisture.

2. Problem: High Moisture Content in Final Flakes

Exceeding the target moisture level (typically <1%) is a critical quality failure. Excess moisture leads to hydrolytic degradation during extrusion, severely compromising the Intrinsic Viscosity (IV) and structural integrity of the final product.

Common Causes & Diagnosis:

• Mechanical Dewaterer Underperformance: The screen inside a centrifugal dryer can become clogged with fines or worn over time, reducing its efficiency. Overloading the machine also prevents it from expelling water effectively.
• Insufficient Thermal Drying: This can be due to several factors:
  • Low Temperature: The temperature in the hot air pipe dryer may be set too low.
  • Short Residence Time: The material may be travelling through the drying pipes too quickly, not allowing enough contact time with the hot air. This is often linked to an excessively high feed rate.
  • Low Airflow: A clogged filter or underperforming blower can reduce the volume of hot air, hampering evaporation.

Solutions & Preventative Measures:

• Regular Screen Maintenance: Routinely inspect and clean the screen in your centrifugal dewatering machine.
• Audit Thermal Dryer Settings: Regularly verify that the temperature controller is accurate and the blower is functioning at its specified capacity.
• Optimise Feed Rate: The entire line should be balanced to ensure that the thermal dryer receives material at a rate that allows for complete drying. This is the most common point of failure.
• Monitor Ambient Conditions: Be aware that very high ambient humidity can sometimes affect the final drying performance; minor adjustments to temperature or residence time may be needed.

3. Problem: Lingering Odours in the Final Product

The final PET flakes should be clean and neutral. Any lingering chemical or organic odour indicates an inefficiency in the washing process and can lead to product rejection.

Common Causes & Diagnosis:

• Insufficient Hot Wash: This is the most frequent cause. The hot washer is responsible for removing glues, oils, and organic residues (e.g., from juice or milk bottles). If the temperature is too low, the chemical (caustic) dosage is incorrect, or the residence time is too short, these contaminants will not be fully removed.
• Contaminated Process Water: In closed-loop systems, if the water filtration and treatment are inadequate, bacteria and dissolved contaminants can build up and re-deposit onto the flakes.
• Source Material Contamination: Certain contaminants in the initial bales, such as other plastics (PVC) or excessive organic matter, can be very difficult to remove and may require specialised process adjustments within your PET plastic recycling system.

Solutions & Preventative Measures:

• Optimise the Hot Wash Stage: Regularly titrate and verify the chemical concentration. Check temperature gauges for accuracy. Ensuring the high-speed agitator is functioning correctly to provide mechanical scrubbing.
• Implement a Water Management Programme: Regularly clean filters and monitor the quality of your process water. A well-maintained water treatment system is crucial for a high-quality final product.
• Improve Pre-Sorting: Enhance quality control of incoming bales to remove heavily soiled items or obvious non-PET contaminants before they enter the main washing line.

Your Partner in Production

Proactive maintenance and a deep understanding of the process are the foundations of a successful recycling operation. By anticipating these common challenges, you can ensure your plant runs at peak performance.

At Energycle, we design our systems for reliability and operational simplicity, engineering solutions that minimise these very issues. For further technical support or to learn more about our robust and efficient PET washing lines, contact our engineering team today.