Separating device, comprising a rotatable double walled separating drum, where a first wall of the drum constituting the inner drum (2) is arranged concentrically inside and space from a second wall constituting the outer drum (3) of the separating drum, and that a plurality of apertures are provided in said drum walls, where the apertures in the first wall have larger openings than the apertures in the second wall, and that the axis about which the drum rotates may be arranged at an inclined angle in relation to a horizontal plane.