Tar sands extraction process

Abstract

This invention relates to a process for the extraction of bitumen from tar sands which comprises contacting the tar sand in an extraction zone with a paraffinic hydrocarbon solvent having from 5 to 9 carbon atoms at a ratio of from 2 to 10 parts solvent per part of bitumen present in the tar sand, maintaining the asphaltene fraction of said tar sands in suspension, separating a major portion of said solvent which contains a major amount of the bitumen dissolved therein along with the suspended asphaltene fraction from the extracted sand, passing the extracted sand along with a minor portion of said solvent and a minor amount of bitumen into a water contacting zone and therein contacting said extracted sand with sufficient water at a temperature of at least 100.degree. F. to separate substantially all of said minor amount of bitumen and said minor portion of solvent from said sand, separating said major solvent portion from the suspended asphaltenes and distilling said solvent from said major solvent portion to recover said major amount of bitumen. In a preferred embodiment, the extract from the water contacting zone is centrifuged to separate fines and water from the bitumen and solvent, said minor amount of bitumen is removed from the solvent, e.g., by distillation and may be burned to provide heat for the process. The process of the instant invention contemplates separating said minor amount of bitumen as a low metals bitumen fraction, thus useful as a clean burning fuel. The metal contaminants of the tar sand are removed with the asphaltenes and discarded. Asphaltenes are defined throughout the specification as that fraction of tar which is insoluble in n-heptane and soluble in benzene at room temperature.