Abstract: A mixture of material is transported by a vibrating conveyor (B), deposited thereon by belt conveyor (A), before an inlet (11) of a suction mouth (1). Suction mouth (1) is adjustable in all directions and by using the adjustable units (2) mounted on the suction duct (4), the height of the mouth (1) may be adjusted above the transported mixture of materials which is to be treated. The width of the opening (11) of suction mouth (1) is adjustable (20-26) to shape the mouth either symmetrically or asymmetrically. The suction power at the inlet (11) of the suction mouth (1) is regulated by adjusting its width combined with outside air supply using an air inlet valve (3) associated with suction duct (4) and adjustments of the capacity of exhaust fan (8). The exhausted air is fed to a cyclone (5) in which the materials which are sucked up and transported with the air have to be deposited.