Centrifuge apparatus

In a decanter centrifuge for separating light and heavy phase materials into respective inner and outer layers from a mixture thereof and for separately discharging said materials, having an elongated imperforate bowl with a tapered portion, said bowl being adapted for rotation about its longitudinal axis, feed means for delivering the mixture to be separated into said bowl, a screw conveyor comprising a hub and a series of helical flights mounted on said hub, said series of helical flights being coaxially arranged within the bowl to advance heavy phase material in the direction of the tapered portion of the bowl during rotation of said screw conveyor relative to said bowl, means for discharging light phase material from the bowl, and means for discharging heavy phase material from the bowl including a discharge port in the tapered portion of said bowl, said discharge port having a weir surface, said screw conveyor defining with said bowl a helical chamber extending about said axis between said means for discharging light phase material and said means for discharging heavy phase material, that improvement comprising:

• a baffle carried by the screw conveyor and extending between the mutually facing broad surfaces of two adjacent helical flights in sealing relationship to thereby divide the helical chamber into
• a separating zone communicating with said means for discharging light phase material, and
• a discharging zone for heavy phase material, said discharging zone being disposed within the tapered portion of the bowl and communicating with said means for discharging heavy phase material,
• said baffle having an outer edge closely spaced from said bowl to define therewith a restricted passageway for the underflow of heavy phase material from the separating zone to the discharging zone and extending inwardly from said outer edge for at least the radial distance of the combined thickness of said layers of light phase material and heavy phase material in the separating zone to prevent the flow of light phase material from said separating zone to said discharging zone,
• and means cooperating with said baffle to maintain the inner surface of the layer of separated light phase material at a level disposed inwardly of said weir surface and to discharge light phase material from said separating zone to said discharge passageway, the centrifugal pressure head of the layer of separated light phase material being applied to the heavy phase material in the separating zone and being transmitted through the restricted passageway to the heavy phase material in said discharging zone,
• whereby the centrifugal pressure head transmitted to the heavy phase material in said discharging zone combines with the force applied by said screw conveyor to the heavy phase material in said discharging zone to overcome the centrifugal pressure head of the heavy phase material in said discharging zone, and thereby advance the heavy phase material in said discharging zone to said discharge port for discharge therefrom.