Now available from Herbold Meckesheim USA (N. Smithfield, RI), Density Separation Tanks or Sink-Swim Tanks use water to separate plastics of different densities in post-consumer recycling systems. They can also be used to separate contaminants from homogenous plastics. Items are introduced to the large steel tanks by a feeding screw or conveyor at one end. Three or four transport drums (rotating paddles) move the material from one end of the tank to the other. During this process higher density plastics like PET and PVC and/or contaminants sink to the bottom of the tank while lower density plastics like PE and PP float on the surface of the water. Lighter plastics exit the tank via a top discharge and heavier items are continuously removed by a scraping chain conveyor mounted below the bottom of the tank. The tank’s V-shaped bottom helps to ensure that sinking waste can be exited from the bottom with no accumulation or build-up.
Tanks are available in three sizes from 78” x 31” up to 157” x 71” with drive motors from 1.5 up to 15 hp. Throughputs vary depending on material and tank size.