Solvent dewaxing process

In a continuous process for separating wax from a waxy distillate oil stock having an initial boiling point in the range of 600.degree. to 625.degree. F. and an end point in the range of about 1050.degree. to 1100.degree. F., wherein said waxy oil stock is treated with dewaxing solvent in a solvent to oil volume ratio of from about 1:1 to about 5:1, wherein said oil-solvent mixture is cooled to a selected separation temperature for crystallizing wax from said mixture, wherein solid wax is separated, in a solid-liquid separation zone, from the solvent-oil mixture, and wherein said separated solvent-oil mixture is fractionated, in a fractionation zone, into a solvent fraction and a dewaxed oil fraction;

• the improvement which comprises:
• (a) heating, in a heating zone, said waxy oil stock, undiluted by dewaxing solvents, to a temperature at which all wax is in solution;
• (b) cooling, in a first cooling zone, said heated waxy oil by indirect heat exchange with refrigerant fluids under conditions of plug flow radial mixing to a temperature about 0.degree.-15.degree. F. below the waxy oil cloud point temperature;
• (c) mixing, in a mixing zone, said cooled waxy oil from step (b) with dewaxing solvent, having a temperature about 25.degree.-40.degree. F. above said separation temperature, in a volume ratio of solvent to oil from about 1:1 to about 5:1, under conditions of plug flow radial mixing, for precipitating wax and forming a wax/oil/solvent mixture;
• (d) cooling, in a second cooling zone said wax/oil/solvent mixture from step (c) at a rate of about 1.degree.-8.degree. F. per minute, to said separation temperature for crystallizing wax from said solvent-oil mixture;
• and
• (e) flowing the wax/solvent/oil mixture from step (d) to said solid-liquid separation zone at said separation temperature.