Valorization of Tetra Pak Waste in a Conical Spouted Bed: Predicting the Polyethylene/Aluminum Mixing Index Using CFD Designs

Abstract

The production of waste-derived fuels and aluminum recovery from LDPE/Al represent a sustainable strategy for valorizing the byproducts of Tetra Pak recycling. Nevertheless, ensuring homogeneity and stability within reactors is essential for the efficient production of fuel. To address the challenge of particle segregation, a model integrating two predictive methodologies for the particle mixing index in a conical spouted bed was validated against experimental data. This model evaluates how the ratios of particle diameters and the concentrations of LDPE/Al influence the mixing index throughout the column, identifying regions of optimal mixing or segregation that may impact the performance of waste pyrolysis. The CFD designs utilized k-epsilon turbulence and Gidaspow drag models, effectively demonstrating mixing under conditions of low particle diameter ratios and concentrations. The model successfully predicted trends with a mean absolute error of less than 10%. The thermal recycling of the LDPE/Al composite facilitates the recovery of approximately 0.05 tons of aluminum for each ton of waste, resulting in energy savings of 0.67 MWh when compared with conventional aluminum production from bauxite. These findings underscore the potential of the conical spouted bed as an efficient and well-mixed reactor for the processing of binary particle mixtures, fostering uniform thermal decomposition and enhancing the viability of waste-to-fuel technologies.