Patent GB-1315250-A (GB)
Title: Centrifugal separators
IPC: B04B1/18
Filed: 1971-12-01
Abstract: 1315250 Centrifugal separator ALFA LAVAL AB 1 Dec 1971 [7 Dec 1970] 55752/71 Heading B2P A centrifugal separator for separating a mixture into a liquid component and sediment comprises a rotor 1, 2, Fig. 1, an inlet 5 for the mixture to be separated, an outlet 16 for the separated liquid, valve means 12 for controlling the discharge of sediment from an outlet 11 at the periphery of the rotor, means 27, 28, Fig. 2, for supplying the rotor with a further liquid the density of which is greater than the separated liquid and less than the sediment so that in use an interface is formed between said further denser liquid and the separated liquid, and means 31 for sensing the arrival of said interface at a predetermined radial level when it moves within the rotor, the arrangement being such that when the interface is at the predetermined level the rinsing means operates to actuate the valve means and open the peripheral outlet. The inlet 5 is constituted by a central duct through the drive shaft 4 of the rotor. The mixture is directed by a distributor 7 provided with vanes 6 into the separating chamber 8 in which conical plates 9 are mounted. The valve means or disc 12, which forms the bottom of the chamber, is operable to open or close the sediment outlets 11 by liquid supplied to a space 14 underneath the disc 12 through a supply chamber 13, throttled openings 15 being provided for the escape of the operating liquid. The separated liquid component leaving the chamber 8 through the outlet 16 flows into a chamber 17 from which it is pumped by a paring disc 18 through an outlet conduit 19. A duct 20 extends inwardly towards a chamber 21 from which liquid is pumped by a paring disc 22 through an outlet conduit 23. The conduit 23 is connected to an inlet conduit 24 directly connected to the duct 5 and contains a throttle 26. The denser liquid is supplied by a pump 28 through a conduit 27 connected to the inlet conduit 24. The sensing means 31 is connected to the conduit 23 and through a connection 30 feeds to a control equipment 29, which controls the opening and closing of the sediment outlets 11, information about a certain indication made of the liquid flow in the conduit 23. This indication can be the liquid pressure, the magnitude of the flow or the dielectric constant of the liquid flowing through the conduit 23. When pressure is indicated, however, no flow of liquid is necessary through the conduit 23 which may be closed off beyond the sensing means 31. The position of the interface 32 may alternatively be sensed by means of members placed within or at the outside of the rotor.  In operation, the rotor is charged with the mixture and simultaneously the denser liquid is fed to it by the pump 28 through the conduits 27 and 24. An interface 32 is formed between the separated liquid component and the denser liquid. While the separated liquid leaves the rotor chamber 8 through the outlet 16, the interface 32 moves radially inwards due to an increase in the amount of denser liquid and of separated sediment. When the interface is situated radially outside the opening of the duct 20, the separated (lighter) liquid component discharges through the duct 20 and the conduit 23. When the interface reaches the opening of the duct 20 the pressure therein drops and the denser liquid flow through the conduit. This condition is sensed by the sensing means 31 which transmits a signal to the control equipment 29 and, the latter causes the outlets 11 to be opened so that separated sediment is discharged. Instead of supplying the denser liquid continuously to the rotor, a predetermined amount may be supplied after each time the outlets 11 have been opened. In this case the time interval between successive openings of the outlets 11 will depend entirely upon the sediment content of the mixture.