Patent GB-1392496-A (GB)
Title: Solid-shell screw-conveyor centrifuge
IPC: B04B1/20
Filed: 1972-06-20
Abstract: 1392496 Centrifugal separators G BRUCKMAYER [trading as FLOTTWEG-WERK DR GEORGE BRUCKMAYER] 20 June 1972 [21 June 1971] 28905/72 Heading B2P In a screw-conveyor centrifuge for the continuous separation of solid-liquid mixtures, at least one discharge opening for the liquid fraction is located in the separating chamber 4 of the centrifuge bowl 8, Fig. 1, at a distance in the conveying direction from the feed end of the bowl and is connected by drain conduit means 10 extending along the screw-conveyor 2, 7 to a drain chamber 17 which is separated from the separating chamber 4 and is provided with at least one drain port 23 leading to the outside of the bowl. A sealing disc 5 attached to the hub 2 of the screw-conveyor separates the chambers 4 and 17. The solid-liquid mixture to be separated is fed via a pipe 1 into the interior of the hub 2 and passes via perforations 3 into the chamber 4. Clarified liquid is discharged through drain pipes 10 extending through the conveyor helix flights 7 and the disc 5 into the chamber 17 and thence via openings 23. In a modification Figs. 2a and 2b (not shown), the drain pipes are replaced by drain troughs of frusto-conical cross-section which may be inserted at different radial distances from the conveyor axis in similarly shaped cut-outs formed in the conveyor flights. In a further modification, Figs. 3a and 3b (not shown), drain pipes are insertable in bores located in the conveyor flights and having different radial spacings from the conveyor axis. In the last two arrangements, separated liquids of different densities may be removed at different levels from the bowl. In Fig. 4, the screw-conveyor flights 18 are disposed on supporting webs 19 of hollow construction carried by the hub 2. The solidliquid mixture travels from right to left on the outside of the webs during centrifuging and the clarified, liquid is removed through the webs in a left to right direction. Plastics or metal inserts may be provided within the webs. In Fig. 5, a double-flight screw conveyor is used defining a conveyor screw channel 21 for the solid-liquid mixture travelling from right to left and a drain screw channel 20 for the clarified liquid travelling from left to right, the two channels communicating with each other via openings 24 in a conveyor flight 22. The sealing disc 5 is perforated in the zone of interaction with the drain channel 20 to permit liquid to enter the drain chamber 17 from which it can be removed through the openings 23 or via a paring element. Fine solids which may still settle within the drain screw channel 20 are seized by the screw and pushed up to the discharge openings. One or more gaps 25 are provided in the conveyor flight 22 through which the fine solids are transferred from the drain channel into the conveyor channel upstream of the coarser solids already pushed ahead by the conveyor channel 21 whereby the coarser solids further assist the conveyance of the fine solids. In a modification, Fig. 6 (not shown), the two channels are of differing widths and the screw flight separating the drain channel from the conveyor channel extends only just beyond the clarified liquid drain openings therein.