Patent GB-1139707-A (GB)
Title: Improvements in sludge centrifuges
Inventor: NILSON CARL-GORAN
IPC: B04B13/00
Filed: 1967-10-19
Abstract: 1,139,707. Centrifugal separators. ALFALAVAL A.B. 19 Oct., 1967 [14 Nov., 1966], No. 47642/67. Heading B2P. In a centrifuge including a rotor 1, Fig. 1, having a sludge space, at least one channel 4 leading from the sludge space to a central chamber 5 and a liquid inlet to the chamber, first and second means 12, 14 are arranged to sense different liquid levels in the chambers 5. Liquid to be centrifuged is introduced via a pipe 6 and a distributor 7. Centrifuged liquid emerging from the conical disc at 2 flows through holes 10 into a chamber 11 containing a paring disc 8 which leads to a discharge pipeline 9. The first sensing means 12 may be, as shown, in the form of a paring disc which communicates with a pipeline 13 in which are inserted a manometer 24 and a pressure switch 25. The latter is connected to a sludge discharge electrical control box 18 and is inserted in the current circuit of an electric motor 26 which effects adjustment of a throttling valve 27 inserted in the pipeline 9. The second sensing means 14 may be in the form of a disc 14 having peripheral openings which communicate with a pipeline 15 in which are inserted a valve 17 for adjusting a flow of liquid to the chamber 5, a solenoid valve 20 actuated from the control box 18 and a non-return valve 16 preventing flow of liquid in a direction away from the rotor. A pressure switch 21 connected to the control box 18 is actuated by pressure in the pipeline 15 transmitted by a pipeline 20. At the start of an operation, a programming device in the control box 18 initiates the supply of liquid to be centrifuged through the pipeline 6. A small quantity of liquid, e.g. previously centrifuged liquid, is fed by means of valve 17 and intermittently admitted through pipeline 15 by means of valve 20. Switch 25 is closed and valve 27 kept fully open by energizing motor 26. When the liquid level in chamber 5 reaches a level radially inside the edge of disc 12 pressure is generated in pipeline 13 and, when this pressure reaches a certain value, the switch 25 is actuated to stop the motor 26 and the valve 27 throttles the outlet of the centrifuged liquid. Alternatively, the valve 27 may be adjusted by hand while observing the manometer 24. Centrifugation proceeds until liquid flow from pipeline 15 through chamber 5 and channel 4 is throttled by sludge formed at the channel opening. The liquid level in chamber 5 moves radially inwardly of the edge of disc 14 and generates a counter-pressure to liquid flow through pipeline 15. The resulting pressure increase in pipeline 15 is transmitted to switch 21 which is thereby closed whereupon the programming device in control box 18 initiates automatic discharge of the sludge during which the supply of liquid to pipeline 6 is interrupted. When sludge has been discharged, the liquid levels in chamber 5 are displaced radially outwardly, the pipeline 13 is relieved of pressure so that switch 25 is closed and actuates motor 25 to open valve 27. The cycle of operations is then restarted. In Fig. 2, the valve 20 is dispensed with and a quantity of gas adjusted by valve 17 flows continuously through pipeline 15 into chamber 5. Liquid is supplied to chamber 5 through a hole 28 in the wall of pipeline 9. When gas is prevented from flowing out of disc 14 as a result of inward movement of the liquid level to the edge of disc 14 due to sludge accumulation at the opening of channel 5, the gas pressure, in pipelines 15, 22 rises until it closes switch 21. In another arrangement, the first or each level sensing means, may be an electric probe and the level sensing can be effected by closing a current circuit. In a further arrangement, the level sensing means may be actuated by a disc which offers resistance to turning, e.g. by means of a spring, and the periphery of which is wetted by the liquid level.