GB954172A - Centrifugal separator - Google Patents

Abstract

<PICT:0954172/C1/1> A centrifuge for separating a liquid-solids slurry into its components comprises a rotatable solid bowl 12 having separate end outlets for the solid and liquid fractions, the liquid fraction outlet 45 being arranged to maintain an annular pool P of slurry within the bowl, a coaxially mounted conveyer 28 which has at least one helical blade 30 projecting into the pool P and is rotated in the same direction as, and at a speed slightly different from that of, the bowl 12 so that the solids are separated by centrifugation against the bowl and are conveyed to their outlet by the blade 30, means for continuously feeding the slurry to the bowl interior adjacent the end opposite the liquid outlet 45, and means for feeding at least one fluid agent, capable of promoting the centrifugal separation of the solids, to the slurry adjacent its passage into the bowl. The bowl 12 is mounted in a casing 10 and is belt-driven through a pulley 18 on a hollow shaft 14 secured to the bowl by a spider 34. The conveyer 28 is driven by a shaft 22 coupled to the bowl hollow supporting shaft 16 through reduction gearing 20. The liquid outlet 45 consists of slots in a plate 44 which communicate with a compartment 80 in the casing. Adjustable weirs 46 defining the depth of the pool P. The solids are discharged into a compartment 38 through the spaces between the arms of the spider 34, impeller blades 40 facilitating the discharge. The slurry is fed through a pipe 50 connected by a T-connection 54 to a source of supply and opening at 52 into an end compartment in the conveyer 28 bounded by a wall 48 and communicating through openings 58 with the bowl interior. The fluid agent may be fed from a tank 62 via a flow regulator 64, a control valve 66 and a pipe 60 adjacent the opening 52. The agent may alternatively or additionally be fed via a pipe 68 to a compartment bounded by the walls 48, 70 and communicating with the interior of the bowl by means of nozzles 76, 78 discharging above or beneath the inner surface of the pool P. The agents from the pipes 60, 68 may be of the same or different nature or they may be of different concentrations. Baffles 82 extending below the pool surface are provided on the conveyer 28 to ensure a thorough mixing of the fluid agent with the slurry as it travels towards the outlet 45. In a modification, a third fluid agent feed pipe is provided extending through the slurry feed pipe to a third compartment in the conveyer 28 communicating through discharge nozzles with the bowl interior. The fluid agent may be in the form of a chemical which may act as a flocculating, coagulating, sequestering or de-emulsifying agent. Examples of slurries treated are aqueous suspensions of fine clay particles, digested sewage sludge and oil-water emulsions containing suspended fine solid particles.