Continuous process for thermal extraction of oil shale

Claim 1

A CONTINUOUS PROCESS FOR THE PRODUCTION OF SHALE OIL BY THERMAL EXTRACTION OF OIL SHALE WITH A LIQUID HYDROCARBON COMPRISING THE STEPS OF PASSING FRESH, RELATIVELY COARSE OIL SHALE TO AN EXTRACTION ZONE, AND THEREIN PASSING SAID SHALE COUNTERCURRENTLY IN CONTACT WITH A LIQUID SOLVENT CONSISTING OF A HEAVY SHALE OIL FRACTION PREVIOUSLY DERIVED FROM THE PROCESS, MAINTAINING THE TEMPERATURE OF THE SHALE IN SAID EXTRACTION ZONE FROM ABOUT 700* TO 800* F. WHEREBY THE KEROGEN CONTENT OF SAID SHALE IS CONVERTED INTO PRODUCTS SOLUBLE IN SAID OIL, WHILE MAINTAINING THE PRESSURE IN SAID EXTRACTION ZONE SUBSTANTIALLY ABOVE ATMOSPHERIC TO PREVENT EXCESSIVE VOLATILIZATION OF SAID OIL AND EXTRACTION PRODUCTS IN SAID EXTRACTION ZONE, CONTINUOUSLY REMOVING AN EFFLUENT FROM SAID EXTRACTION ZONE COMPRISING A VOLATILE OVERHEAD STREAM AND A LIQUID STREAM CONSISTING OF EXTRACTION PRODUCTS DISSOLVLED IN SAID SOLVENT OIL, SEPARATING SAID EFFLUENT INTO A PLURALITY OF FRACTIONS, INCLUDING A HEAVY FRACTION, IN A FRACTIONATING ZONE, CONTINUOUSLY WITHDRAWING EXTRACTED SPENT SHALE CONTAINING SUBSTANTIAL QUANTITIES OF ADHERING LIQUID HYDROCARBONS FROM SAID EXTRACTION ZONE, PASSING SAID EXTRACTED SHALE TO A STRIPPING ZONE MAINTAINED AT A PRESSURE SUBSTANTIALLY