Centrifuge apparatus

• US 3,885,734 A
• Filed: 01/10/1974
• Issued: 05/27/1975
• Est. Priority Date: 09/06/1972
• Status: Expired due to Term

• Current Assignee: Alfa-Laval AB Gustavslundsvagen-147 Alvik Stockholm Sweden
• Original Assignee: Chie-Ying Lee
• Inventors: Lee, Chie-Ying
• Primary Examiner(s): Krizmanich, George H.
• Application Number:
  US05/432,258
• Time in Patent Office: 502 Days
• Field of Search: 233/1R,3,7,12,13,14R,19R,19A
• US Class Current: 494/25
• CPC Class Codes: B04B 1/20 discharging solid particles from the bowl by a conveying screw coaxial with the bowl axis and rotating relatively to the bowl
• CPC Class Codes: B04B 2001/2033 with feed accelerator inside the conveying screw
• CPC Class Codes: B04B 2001/2041 with baffles, plates, vanes or discs attached to the conveying screw

Abstract

A decanter centrifuge having a screw conveyor within an imperforate bowl is provided with an annular baffle carried by the screw conveyor. Light phase material and heavy phase material is separated from a mixture thereof fed to the centrifuge bowl. The heavy phase discharge port, usually in a tapered portion of the bowl, is preferably at a greater radial distance from the rotational axis than the inner surface of the light phase material. The periphery of the baffle is closely spaced from the bowl in order to form a restricted passageway for the underflow of heavy phase material from a separating zone within the cylindrical portion of the bowl to a heavy phase discharge zone within the tapered portion of the bowl. Pressure from the materials within the separating zone, or from an independent source, is transmitted through the restricted passageway and applied to the heavy phase material undergoing discharge, thus facilitating its discharge with minimum content of light phase material. With a conical baffle, incoming feed is directed into the inwardly facing surface of the baffle and accelerated in order to minimize turbulence in the separating zone. Efficient separation is accomplished, even with materials heretofore considered unsuited for separation by a decanter centrifuge.

Claims

1. 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 coaxially arranged with the bowl to revolve relative to the bowl for advancing heavy phase material in the direction of the tapered portion of the 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, that improvement comprising:

a baffle positioned between said axis and said bowl and dividing the interior of the bowl into a separating zone which communicates with said means for discharging light phase material, and a discharging zone for heavy phase material which is disposed within the tapered portion of the bowl and communicates with said means for discharging heavy phase material, said baffle having its inner edge disposed closer to said axis than the radial distance between said weir surface and said axis, and extending through the entire layer of separated light phase material in the separating zone and having its outer edge closely spaced from the bowl to define therewith a restricted passageway for the underflow of heavy phase material from the separating zone to the discharging zone and to prevent the flow of separated light phase material from said separating zone to said discharging zone, and means for pressurizing the heavy phase material in the separating zone beyond the pressures applied thereto by the centrifugal force of separated light phase material disposed radially outwardly of the weir surface of said port, whereby the additional pressure provided by said pressurizing means is transmitted to the heavy phase material in said separating zone and through said restricted passageway to the heavy phase material in the discharging zone for promoting the advance of the heavy phase material through the discharging zone to said port for discharge thereform.

2. A centrifuge according to claim 1 wherein the pressurizing means comprises means for delivering pressurized gas to the separating zone.

3. A centrifuge according to claim 2 wherein the means for delivering pressurized gas includes a conduit extending through said feed means.

4. A centrifuge according to claim 1 wherein the pressurizing means comprises means for maintaining the inner surface of the light phase material in said separating zone radially outward of the weir surface of said port, whereby the centrifugal pressure head of that portion of the light phase material disposed radially outward of said weir surface provides said additional pressure.

5. A centrifuge according to claim 1 wherein said baffle is annular and is carried by the screw conveyor.

6. A centrifuge according to claim 1 wherein the pressurizing means comprises means for delivering pressurized fluid to the pressurizing zone.