Enhancement of liquid-fluidized bed classification (LFBC) of plastic particle mixtures via selective thermal particle modification

A novel method, based on temperature programming of the fluidizing medium, is investigated to improve the separation of complex plastic mixtures via liquid-fluidized bed classification (LFBC). Experiments were performed in a liquid-fluidized bed apparatus that was designed to operate in both upflow and downflow modes, for “heavier-than-water” and “lighter-than-water” plastic particle species, respectively. Temperature programming was achieved by using heated or cooled fluidizing feed water from two different reservoirs controlled at the desired temperatures. Binary beds of plastic mixtures of typical consumer/industrial plastics (PVC, PET, PS PC, LDPE, HDPE, and PP) were used. Due to differences in the thermal properties of the various plastic types, namely thermal diffusivities and glass transition temperatures, the experimental results show that the separation performance of LFBC can be significantly improved by selective modification of particle size/density via temperature programming of the fluidizing medium, water.