GB952722A - Removal of waxy material from oils - Google Patents

Abstract

<PICT:0952722/C3/1> Waxy material is removed from oil by treating the oil to form a slurry having its liquid phase of lower density than its solid phase and separating the phases in an imperforate centrifuge bowl which gradually increases in internal diameter for at least a substantial portion of its length, forcing the waxy material, deposited under the action of centrifugal force at the inner surface of the bowl, axially in the direction of decreasing radius of the bowl into a region in which it is freed from entrained oil by washing with a solvent, removing the oil-free waxy material from the region, and withdrawing the oil from the bowl at its end of greater radius. Raw lubricating oil feed stock containing waxy material is dissolved in a suitable solvent. The mixture is heated to bring the oil and wax components in solution and is then cooled sufficiently to form the required slurry. The chilled slurry is introduced through an inlet 10 into a stationary unit 11, passes into a screw conveyer 14 via its rotary shaft 12 and out through ports 16 on to the surface of the conveyer and is impinged upon the inner surface of the bowl 20 rotating at a higher speed than the conveyer. The bowl may be conical, or partly conical and partly cylindrical. Due to its higher density the wax-containing solid material from the slurry is consolidated in a layer on the bowl inner surface by centrifugal force while the oil-containing liquid component overflows through ports 24 into a housing 26 from which it is withdrawn through a discharge outlet 28. The solid material is swept by the conveyer blade 18 from the surface of the consolidated layer into a zone 30 and out through ports 32 into the casing 26 where it is withdrawn through a discharge outlet 34. Wash-solvent may be introduced through a pipe 42 and forced through nozzles or ports 44 in the conveyer 14 to remove entrained oil from the solid material. The cooling of the heated mixture may be by means of heat-exchange apparatus or by auto-refrigeration. The temperature of the chilled slurry is maintained during centrifugation by coolant circulation about the bowl area. The process may be continuous or intermittent. A number of solvents are specified and results of de-waxing processes using propane as the solvent are given.