Patent GB-987166-A (GB)
Title: Process and apparatus for the centrifugal separation of solids and liquid from a mixture thereof
IPC: B04B1/10
Filed: 1963-07-03
Abstract: A process of concentrating solids in, and separating them from, a solids-liquid mixture, in which the solids have a density greater than that of the liquid, comprises introducing the mixture to a centrifuging zone, feeding to the zone a carrier liquid of density greater than that of the solids, so as to form a concentrated layer of the solids radially inward of the carrier liquid and a layer of the mixture-liquid radially inward of the solids, withdrawing the mixture-liquid from a locus adjacent the axis of the zone, withdrawing together portions of the carrier liquid and of the concentrated solids by leading these portions through a discharge passage in a direction towards the axis of the centrifuging zone, and controlling the rate of feed of the carrier liquid so as to control the amount of mixture-liquid in the discharged solids.  The process is applicable to the separation of wax from lubricating oil stock containing a solvent and chilled to an appropriate temperature to solidify the wax.  It is carried out in a centrifuge, Fig. 1, comprising a rotor 10 within which a series of frusto-conical discs 36 having feed openings 37 are mounted on the skirt 26 of a centre tube 24 fitted over the rotor hub 12. Superposed over the uppermost disc is a dividing cone 40 spaced from the under surface of the rotor cover 16, so as to provide a discharge passage for the portions of carrier liquid and <PICT:0987166/C4-C5/1> <PICT:0987166/C4-C5/2> <PICT:0987166/C4-C5/3> solids, by a number of radial spacer elements 42, Fig. 2, the outer portions 42a of which are separated from the cover 16 by a gap 42b whereby a free annular zone is provided at the entrance of the discharge passage.  In operation, the mixture is fed to the pocket defined between the bottom of the hub 12 and a feed cone 12 having accelerating vanes 32, and passes through an opening 28 in the hub and holes 34 in the skirt 26 into the stack of discs. Under the action of centrifugal force, the lighter liquid component moves inwardly through the disc elements and discharges upwards over an extension 44 of the cone 40.  The heavier solid component moves towards the periphery of the rotor.  The carrier liquid, e.g. brine, is preferably introduced, prior to the feed mixture, by suitable feed tubes which may be controlled by valves, to the pocket defined by the cone 30 and a cone 46 having vanes 48 and flows to the rotor periphery through a passage 50 in the skirt 26 and a passage provided between the rotor shell 14 and a frusto-conical distributer 52 spaced from the shell by spacer elements 54. The separated solids compact against the carrier liquid and portions of both are removed through the passage between the cone 40 and the cover 16 and are discharged over a weir 56. Alternatively the carrier liquid may be partially or wholly incorporated in the mixture and fed with it to the rotor. In Fig. 5, the stack of discs 36 is surrounded by a number of frusto-conical baffles 60 arranged in zig-zag fashion to facilitate compaction of the solids and provided with holes 62 for the outward passage of the solids and the inward passage of liberated liquid in the manner described in Specification 966,353.