How it works

The Dense medium separation (DMS) or heavy medium separation (HMS), or Sink-Float gravimetric separation, also known within the field of the scrap treatment as Flotation, is a process used to separate materials that have different specific weight. To obtain this kind of separation, the material to be separated is immersed into a ‘bath’ of a fluid of the proper density, in which the light components float, while heavy ones sink.


According to the application, a suspension of powdered Ferrosilicon or Magnetite in water is used as fluid – heavy media – in order to allow the separation. To obtain a heavy media with the specific gravity most suitable for the separation, it is necessary to increase or decrease the concentration of Ferrosilicon or Magnetite dispersed in water.

In industrial plants, the heavy media is pumped and kept in circulation inside a Rotating Drum Separator where the ‘bath’ is created in which the material to be treated is immersed. The ‘Float’ components with a specific gravity lower than that of the heavy media will float on it and will come out from the Drum overflowing with the fluid from the outlet mouth. The ‘Sink’ components with a specific gravity greater than that of the heavy media will sink and are extracted from the bottom of the bath through special lifters or through a screw, depending on the type of Drum Separator.


The ‘Sink’ and ‘Float’ products are unloaded continuously from the chutes of the Drum Separator on a drainage and washing screen in order to remove the Ferrosilicon or Magnetite adhering to the surfaces of the material. After a suitable regeneration, the heavy media is recirculated inside the Drum Separator.