Abstract
Dry gravity separation of shredder residue of electric appliance wastes were carried out by using gas-solid fluidized beds. It is generally known that the gas-solid fluidized bed has liquid like properties such as density and viscosity. When objects of different density are immersed into the fluidized bed, light objects float at the fluidized bed surface and heavy objects sink into the bottom. The boundary of the density of floating and sinking objects depends on the apparent density of the fluidized bed. The apparent density can be controlled by changing the superficial air velocity or mixing ratio of binary particles which are used as fluidized medium. The main purpose of this study is to separate Cl-containing plastics like polyvinyl chloride (PVC) from waste plastics. The mixture of glass beads and polystyrene particles was used. The particle diameter and true density were 210 - 300 µm, 2500 kg/m3 for glass beads and 355 - 500 µm, 1050 kg/m3 for polystyrene particles respectively. Floating and sinking of plastic pieces in the fluidized bed were examined by changing the superficial air velocity and mixing ratio of the mixture. The Cl-containing plastics and Cl-noncontaining plastics were successfully separated at top and bottom of the fluidized bed at u0/umf = 1.5 and volume fraction of glass beads = 0.8, although density difference of those plastics was only about 200 kg/m3. Effect of plastic shape on the floating and sinking was also investigated by changing the equivalent volume diameter, aspect ratio and flatness ratio. Good correlation between shape coefficient and the floating-sinking was obtained.
