Screw centrifuge for wet mechanical separation of solids

A screw centrifuge for wet mechanical separation of solids according to density, comprising:

• a rotatable drum (11) having a cylindrical wall portion and axially opposed, inwardly tapered wall portions, a first of said tapered portions having a first discharge opening (14) for discharge of the separated material as settleable solids (16), a second of said tapered portions having a second discharge opening (15) for floating solids (17), and a third discharge opening (19) in the cylindrical portion for the separating liquid (18);
• a rotatable shaft (12) extending axially within the drum with an internal passageway (21) and associated infeed opening (22) for delivering the solids to be separated between the shaft and the drum wall, wherein the shaft (12) has a first screw section with flights (13,13′,13″) for transporting settleable solids toward the first opening (14) and a second screw section with flights (23,23′) working in opposite direction for transporting floating solids toward the second opening (15);
• a baffle disc (20) arranged on the shaft between the infeed opening (22) and the first discharge opening (14);
• and
• wherein the second screw section for the floating solids (17) is a multi-channel screw and an auxiliary outer flight (13′,13″) of the first screw section surrounds some of the flights in the second screw section (22,23′).

A screw conveyor for separating solids in a screw centrifuge, comprising:

• a rotatable shaft including an internal passageway (21) and associated infeed opening (22) for the solids to be separated;
• a first flight (13,13′,13″) for transporting settleable solids in a first axial direction and a second flight (23,23′) working in opposite direction for transporting floating solids in an opposite axial direction;
• a baffle disc (20) arranged on the shaft between the first flight and the second flight;
• wherein the second flight for the floating solids (17) is multi-channelled, and the first flight includes an auxiliary outer flight (13′,13″) that extends over the baffle disc and surrounds a portion of the second flight (23,23′) adjacent to the baffle disc.