Development and validation of a CFD-based model for simulating rotating drum separators

Abstract

Within the context of the European Green Deal, recycling rates of plastics and metals are targeted to increase which will subsequently increase the requirements for high-quality recycled plastics and metals. The decisive step to achieve this high-quality recyclate lies in the sorting of the materials before their recycling. Density separation sorts materials based on their density difference from a liquid's density and is the most widely used separation technique in the industry because of its high cost-effectiveness. However, experimentally optimising a density separator would require a large amount of time and investment due to its large dimensions and the complex physical phenomena involved. Hence, the scope of this study is to develop a Computational Fluid Dynamics (CFD) model to investigate the fluid flow and trajectories of plastic particles in a density-separation-based rotating drum. This novel strategy and CFD model offer a tool capable of predicting the separation efficiency with an absolute error of 1-5%, depending on the polymer type, while reducing the computational time by a factor of 9. Moreover, the influence of air bubble attachments to the injected particles in the drum is observed and the inclusion of inter-particle collisions on the accuracy of the model is assessed.