Solvent dewaxing process

Claim 1

In a continuous solvent dewaxing process wherein a light waxy distillate petroleum oil stock is heated, in a heating zone, to a temperature wherein all wax is dissolved, wherein said heated oil stock is treated with solvent in a solvent to oil volume ratio of 1:1 to 5:1 to form an oil-solvent mixture, and wherein said oil-solvent mixture is cooled, in a cooling zone, at a cooling rate of 1°-8° F./min, to a selected separation temperature in the range of about +25° to -40° F. for precipitating wax from said oil-solvent mixture; where said precipitated wax is separated, in a solid-liquid separation zone, from said oil-solvent mixture to yield slack wax and a free oil-solvent mixture is fractionated, in a fractionation zone, to yield a solvent fraction and a dewaxed oil fraction; the improvement which comprises: (a) continuously flowing a liquid stream of dewaxing solvent, having a selected temperature in the range of about 40°-80° F., into the inlet of a plug flow radial mixing zone; (b) injecting said heated waxy oil stock into said dewaxing solvent flowing within said plug flow radial mixing zone via a plurality of injection nozzles spaced along the length of said mixing zone; (c) mixing, in said plug flow radial mixing zone each injected portion of heated waxy oil stock intimately with said flowing solvent before injection of the next following portion of heated waxy oil stock, for producing an oil-solvent mixture exiting said mixing zone having a temperature below the depressed cloud point; (d) cooling, in a cooling zone, said oil-solvent mixture to a selected separation temperature in the range of about +25° F. to -40° F., for precipitating wax and forming a wax/oil/solvent mixture; and (e) flowing said wax/oil/solvent mixture from said cooling zone to said solid-liquid separation zone.