Patent GB-1220430-A (GB)
Title: Improvements in or relating to centrifugal separation apparatus
IPC: B04B1/20
Filed: 1969-10-14
Abstract: 1,220,430. Centrifugal separators. BIRD MACHINE CO. 14 Oct., 1969 [15 Oct., 1968], No. 50410/69. Heading B2P. [Also in Division G3] In a centrifugal separator comprising a rotatable solid bowl 14, Fig. 1, into which a solids-liquid slurry is fed to form a pool and from which a relatively rotatable conveyor 36 continuously discharges a first fraction of the slurry containing solids which are separated towards the wall of the bowl under the action of centrifugal force and a skimmer 42 continuously discharges a second fraction of the slurry containing solids which are not so readily separated, means are provided for automatically adjusting the distance of the skimmer 42 from the wall of the bowl, and hence the pool depth, under the control of signals obtained from at least one consistency analyser for at least one of the separated fractions. The slurry is fed via a fixed T-pipe 86 and a rotatable pipe 60 into an end compartment 66 of the conveyor hub 26 and thence into the bowl interior. Flocculant or other chemical to facilitate solids separation is fed via pipes 88, 88' into a compartment 90 of the hub and discharges therefrom, through nozzles 92, into the pool formed in the bowl 14. The skimmer extends into an annular chamber member 38 provided on the conveyor hub 26 and having inlet openings 40 and is mounted on eccentric flanges 48 on a sleeve 50 extending coaxially through the bowl shaft 20 and fixedly connected to a support ring 52 on a support structure 24. The skimmer removes the second fraction from the pool of slurry and discharges it through ports 54, sleeve 50 and effluent pipe 56. The distance of the skimmer from the wall of the bowl is adjusted by rotating it on the eccentric flanges 68 by means of the rotatable pipe 60 through a block 58 and a gib slide connection 54, the pipe 60 being rotated by a worm shaft 70 operated by a reversible electric motor 94. The first slurry fraction is discharged by the conveyor 36 into a chute 12, which is provided with a sampling hopper 74. As shown in Fig. 2, a pipe 78 connected to the hopper 74 leads a sample of the first fraction to a pump 100 which continuously discharges through a line 102 to a consistency analyser 104 which provides an electric output signal which is a function of the density of the sample being analysed, the sample being continuously returned via a line 80 to the chute 12. The signal is fed via a converter 116 and line 118 to control circuitry CC for operating the motor 94 in the required direction to move the skimmer radially either outwardly towards, or inwardly from, the wall of the bowl and hence decrease or increase the pool depth. A sample of the second fraction is continuously led from the effluent pipe 56 through a line 82 to a turbidity measuring device 130 which provides an output signal indicative of the solids concentration of the sample which is returned to the pipe 56 through a line 84. This signal is fed via a receiver recorder 138 and line 140 to control circuitry CC for operating a variable speed reduction motor 144 driving a pump 146 which delivers the required amount of chemical to the pipe 88. The signal on line 118 may additionally or alternatively be utilized to operate the chemical feed pump 146 as indicated by dotted line 122. The signal on line 140 may additionally or alternatively be utilized to operate the pool adjustment motor 94 as indicated by the dotted line 152. Two diagrams of the control circuitry are described in detail.