CENTRIFUGE APPARATUS

• US 3,795,361 A
• Filed: 09/06/1972
• Issued: 03/05/1974
• 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:
  US05/284,371
• Time in Patent Office: 545 Days
• Field of Search: 233/2,7,27,28,46,47R
• US Class Current: 494/26
• 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 onto 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 mxiture to be separated into said bowl, a screw conveyor coaxially arranged within the bowl to revolve relative to the bowl for advancing heavy phase Material in the direction of the tapered portion of the bowl, a discharge passageway for light phase material, and means including a discharge port for discharging heavy phase material from the tapered portion of the bowl, said discharge port having a weir surface, that improvement comprising:

an annular baffle carried by the screw conveyor positioned to divide the interior of the bowl into a separating zone communicating with said discharge passageway, and a discharging zone for heavy phase material, said discharging zone being disposed within the tapered portion of the bowl and communicating with said discharge port, said baffle extending outwardly beyond the interface between the separated layers of light and heavy phase materials in the separating zone, said baffle having its outer peripheral edge in closely spaced relationship with the bowl to define therewith a restricted passageway for the underflow of heavy phase material from the separating zone to the discharging zone, and means cooperating with said baffle to maintain the inner surface of the layer of separted eight 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.

2. A centrifuge according to claim 1 wherein the baffle is a flat plate arranged coaxially within said bowl.

3. A centrifuge according to claim 2 wherein the plate is disposed normal to said longitudinal axis.

4. A centrifuge according to claim 1 wherein the baffle is of frusto-conical configuration and is formed about said longitudinal axis.

5. A centrifuge according to claim 4 wherein the baffle tapers in the same direction as the tapered portion of said bowl.

6. A centrifuge according to claim 1 wherein the feed means includes an outlet which is open to the separating zone and is disposed adjacent to the baffle on the side of said baffle facing the separating zone.

7. A centrifuge according to claim 6 wherein the baffle is of frusto-conical configuration and is formed about said longitudinal axis, the outlet of said feed means being disposed inwardly of said baffle in position to direct the mixture to be separated onto the inner surface of said baffle.

8. A centrifuge according to claim 7 further including axially extending, accelerating vanes on the inner surface of said baffle for increasing the angular velocity of said mixture as it flows outwardly along the inner surface of said baffle.

9. A centrifuge according to claim 1 wherein said baffle is imperforate at least for the radial distance of said light phase layer.

10. A centrifuge according to claim 1 wherein said discharge passageway for light phase material is a port formed in said bowl, and the last-introduced means of said claim 1 is a weir surface on said port disposed closer in radial direction to the longitudinal axis of said bowl than the weir surface of the discharge port included in the means for discharging heavy phase material.

11. A centrifuge according to claim 10 wherein the respective ports of said discharge passageway for light phase material and said means for discharging heavy phase material are disposed at opposite end portions of said bowl.

12. 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 within 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:

an annular baffle carried by the screw conveyor positioned to divide 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 extending outwardly beyond the inner layer of separated light phase material in the separating zone and having its peripheral 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 means for pressurizing the heavy phase material in the separating zone with a deep layer of light phase material in said separating zone whereby the 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 therefrom, wherein the pressurizing means comprises means for maintaining the inner surface of the light phase material in said separating zone at a level inward of the level of said weir surface of said port, whereby the centrifugal pressure head of that portion of the light phase material disposed iwnard of the level of said weir surface provides pressure in addition to the centrifugal pressure head of that portion of the light phase material disposed outward of the level of said weir surface.