Analyzing the effect of the density of medium on efficiency of hydrocyclone separator in sorting of PVC and PET using CFD

Abstract

In plastic recycling, the precision with which a plastic component is separated during the recycling process from a combination determines the purity of the recycled plastic. In this study, polyethylene terephthalate (PET) particles and polyvinyl chloride (PVC) particles are separated using a hydrocyclone separator, a density-based sorting device that uses centrifugal force and a flow pattern generated by liquid pressure to separate particles. In hydrocyclonic sortation, the density of the medium is one of the crucial variables that affect sortation because an effective separation requires a suitable density difference between particles and medium. If the medium density is too close to the particle density, there won't be enough centrifugal force to separate the particles from the fluid, and the separation will be inefficient. And when the medium density and particle density differ too much, excessive turbulence disrupts the sorting process, making the sortation process less efficient. Therefore, using both theoretical and computational fluid dynamics (CFD) simulation approaches, the study analyzes the influence of medium density on separation efficiency and determines an optimal medium density at which separation efficiency is maximum. Theoretically, medium density should be 1374.07 kg/m3 for maximum efficiency, while 1380 kg/m3 has been determined to be optimal medium density for maximum efficiency in CFD simulation. The result of the CFD simulation is in good agreement with the outcome of the theoretical approach. In both scenarios, it turned out that the appropriate medium density for obtaining the best separation efficiency is closer to that of denser particles.