Process for regenerating exhausted oils

Claim 1

A process for regenerating spent oils, characterized by comprising the steps of: (a) Heating the oil in a first oven, (b) Sending the heated oil to a pre-distillation column and separating at the column head the water and the light hydrocarbons, (c) Recovering from the bottom of the pre-distillation column the oil which is sent to a solvent-extraction section to remove from the oil the major fraction of the impurities contained therein, (d) Heating the oil raffinate exiting the extraction section after having stripped the solvent therefrom in a second oven, (e) Feeding the oil from the heating stage to a stage of distillation under vacuum with a bottom temperature higher than 300° C., to separate from the column side the lubricating bases having the lower viscosity and deprived of impurities and discharging from the bottom the heavier lubricating bases in which the remaining impurities have been concentrated, (f) Subjecting the heavier lubricating fraction to a heat treatment at a temperature from 300° C. to 450° C. under adiabatic conditions for a time varying from 1 to 120 minutes, (g) Subjecting the heavier lubricating fraction, after the heat treatment, to a second extraction with solvent, and (h) Sending the heavy lubricating base raffinate and the other bases having a lower viscosity, separately, to a hydrofinishing stage.