Investigation of a Sink-Float plastic separator through Computational Fluid Dynamics and Particle Image Velocimetry

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• The Circular Economy Action Plan seeks to boost recycled plastic competitiveness.
• Improving recycled plastic quality is crucial for increasing its market share.

Purpose of the Study:

• Investigate the sink-float separation process for plastics recycling.
• Enhance the yield and purity of recycled plastics through process optimization.

Main Methods:

• Computational Fluid Dynamics (CFD) modeling.
• Particle Image Velocimetry (PIV) for flow field validation.
• Empirical experiments with plastic granules on a lab-scale separator.

Main Results:

• CFD model validated with PIV, showing high accuracy (flow field <5.3% error, yield/purity <1% error).
• Identified air bubble attachment to hydrophobic plastics as a primary cause of misplacement.
• Optimized injection location for plastics with density differences >0.04, achieving 99% yield and purity.

Conclusions:

• The developed CFD model and simulation strategy can optimize sink-float separators for recycling companies.
• Addressing air bubble attachment can significantly improve separation efficiency.
• The study provides a pathway to enhance recycled plastic quality and market competitiveness.