Patent ID: 8366912

Claim:
A method for producing a high yield of high quality base oil from a used waste lubricating oil, the method consisting essentially of: a) separating a distillate stream comprising contaminants including at least one of water, light hydrocarbons, solvents, solids, polymers, high molecular weight hydrocarbons, lubricating oil additives, chemicals, and salts from the waste lubricating oil and a first bottom stream in a first flash distillation zone; b) separating a first flash distillation stream having a boiling range from about 350° F. to about 500° F. from the first bottom stream to produce a second bottom stream by contacting the first bottom stream with a heated portion of the second bottom stream in a second distillation zone at a temperature selected to produce the first flash distillation stream; c) separating a second flash distillation stream having a boiling range from about 500° F. to about 650° F. and a third bottom stream from the second bottom stream by contacting the second bottom stream with a heated portion of the third bottom stream in a third distillation zone at a temperature selected to produce the second flash distillation stream; d) separating a third flash distillation stream having a boiling range from about 650° F. to about 1050° F. and a fourth bottom stream from the third bottom stream by contacting the third bottom stream with a heated portion of the fourth bottom stream in a fourth distillation zone at a temperature selected to produce the third flash distillate stream; e) contacting the third flash distillation stream with a solvent effective to separate high quality base oil from lower quality base oil in a solvent extraction zone and recovering a stream of high quality base oil and solvent and a stream of lower quality base oil and solvent; and f) separating the high quality base oil and the solvent to produce a stream of product high quality base oil; g) separating the lower quality base oil and the solvent to produce a lower quality base oil stream; and h) combining the second flash distillation stream with the lower quality base oil stream to produce a combined stream and passing the combined stream to hydrogenation to produce a high quality base oil stream.