Process and apparatus for the centrifugal separation of solids from liquid

摘要

A centrifuge for separating a wax-oil mixture into its components comprises a rotor 12 in which are mounted in concentric spaced relationship a disc stack 28 and baffles 52, 54 comprising non-radial surface portions formed with openings 56, 58, 62, 66, the mixture being fed through a tube 24 having a flared skirt 26 with openings 27 and the separated solids and liquid being separately discharged from the rotor. The baffle 52 mounted between cone-shaped members 38, 50 comprises a series of complementing frusto-conical surface portions arranged in zigzag manner and the baffle 54 consists of a ring element 60 having a flat inward surface and held in place by an annular element 64 presenting frusto-conical surfaces arranged in zig-zag fashion. The baffle 54 is held in place by circumferentially-shaped legs 58. In operation, a chilled mixture of wax solids and hydrocarbon oil which may be diluted with a solvent passes through the openings 27 and is introduced via openings 29 in the spaces between adjacent discs. Under the action of centrifugal force the oil flows inwardly and is discharged through a passage 30. The solids move outward along the underside of the discs and are directed against the baffles 52, 54, the frusto-conical surface of which cause compaction of the solids and liberation of oil entrapped thereby. The compacted solids pass through the orifices 58, 62, 66 and are carried over a ring dam 34 via passages between supporting members 41 by a carrier liquid, e.g. brine, fed by a tube 45 and accelerating vanes 42 through passages 48 and the passage between the rotor and the conical member 50. The latter may be replaced by a number of tubes. The carrier liquid may alternatively be introduced with the mixture. Instead of the ring dam arrangement, the solids may be discharged with or without carrier liquid through peripheral nozzles in the rotor, e.g. of the type described in Specification 947,990. The oil liberated between the baffles 52, 54 is shielded by the baffle 52 from the outward movement of the compacted solids and moves towards and through the orifices 56 towards the disc stack and discharge passage 30. In a modification, the outer baffle has a configuration similar to that of the baffle 52. In a further modification each of two baffles comprises a series of sets of zig-zag plates presenting peripherally, instead of vertically, arranged complementing non-radial converging surfaces. In further embodiments the compaction zone may comprise: (a) circumferentially spaced curved vanes 100, Fig. 6, extending axially of the rotor, the solids moving outwardly along the inner surfaces of the vanes and the liberated oil inwardly along their outer surfaces; (b) frusto-conical elements 166, 168, Fig. 7, which may contain orifices; (c) extending portions 28a, Fig.9, of a number of the discs in the stack 281111 having spaced orifices 28b. In Fig. 11, the centrifuge is used to separate wax solids which are lighter than the oil-solvent liquid component of the mixture, e.g. when using a chlorinated hydrocarbon as a solvent, the compaction space for the light solids provided by the baffles 153, 155 being spaced inwardly from the disc stacks 128. Liquid carrier may be split down a collar 157 to assist discharge of the solids out through extension 140. The heavy liquid component may be discharged with or without the aid of a heavy carrier liquid over the dam 134 or through peripheral nozzles. In a further modification of the embodiment of Fig. 1, the baffles 52, 54 may be replaced by loose solid elements, e.g. small cylinders of ceramic material, plastic or metal or other distillation tower-type packings, held in place in the rotor by centrifugal force and presenting in operation the non-radial compacting surfaces and irregularly restricted flow paths for the compacted solids. In all of the above embodiments, liberation of oil from the solids may be facilitated by the addition of a surface-active agent, e.g. of the ionic type such as dodecyl phosphate, to the carrier liquid. U.S.A. Specifications 2,266,553 and 2,793,169 also are referred to.