CFD Simulation of a Sink-Float Separator

One of the biggest challenges in the recycling industry is the separation of materials. One of the commonly used solutions is density-based separation. A sink-float tank is a machine that is often used to perform such separation.

CFD (Computational Fluid Dynamics) is a powerful tool to model the fluid flow in the tank in order to understand and improve the process. CFD is therefore valuable in many situations:

• Particle behaviour: Understanding the trajectory and physical behaviour of the particles and their interactions based on material properties.
• Design: Optimizing the design to minimize regions of turbulence, recirculation, and stagnation. This way, prototype cost can be reduced significantly.
• Efficiency evaluation: Predict the performance of the system under different conditions. For example:
  • Predict the maximal inlet velocity to ensure complete separation
  • Predict the maximal density of the plastic to prevent plastic outflow at the bottom

As an example, the video below shows a generic design of a sink-float tank to separate light plastics from heavier debris. This CFD simulation was performed in Ansys Fluent using the Discrete Phase Model (DPM).

Contact us to discuss the possibilities of CFD in density-separation and particle tracking processes such as:

• Mixers
• Dust accretion problems
• Residence time sensitive systems