Sedimentation centrifuge containing screw conveyor with fins

A sedimentation centrifuge, comprising:

• an elongated, hollow, rotatable, solid-wall bowl adapted to receive a mixture of light liquid, heavy liquid and solids, said bowl being rotatable about a longitudinally extending axis, said bowl having a cylindrical section having first and second axial ends, said bowl having first and second, coaxial, truncated conical, canted sections connected in series with each other, said first canted section extending away from said first end of said cylindrical section, said second canted section being adjacent to and extending away from said first canted section, said first and second canted sections each having a tapered wall, said tapered walls each extending at an acute angle to the axis of rotation of said bowl, said tapered wall of said first canted section being tapered at a larger angle than said tapered wall of said second canted section, said bowl having a first outlet for solids at an axially outer end of said second canted section, said bowl having second and third outlets for light liquid and heavy liquid, respectively, at said second end of said cylindrical section;
• a rotatable, helical screw conveyor rotatably mounted inside said bowl and extending substantially the full length thereof, said screw conveyor having a screw flight with an inner portion which is inclined with respect to the axis of rotation of said bowl and conforms to said cylindrical section and said canted sections and an outer portion which is normal to an inner wall surface of said bowl;
• a plurality of helical fins mounted on said screw conveyor and extending parallel to and being positioned between the turns of said screw flight, said fins being straight in a direction from a radially innermost edge to a radially outermost edge thereof;
• a coaxial supply pipe inside said conveyor and hole means extending from said pipe for feeding the mixture into said cylindrical section of said bowl at a location close to said first end of said cylindrical section, a first zone extending from said location to the axially outer end of said second canted section being free of fins, a second zone extending from said location to said second axial end of said cylindrical section containing said fins.