Hydrocarbon conversion

Claim 1

IN THE PROCESS OF PRODUCING DISTILLATE OILS AND HIGH QUALITY RESIDUAL FUEL OILS OF LOW-SEDIMENT CONTENT BY VISBREAKING HEAVY VIRGIN CRUDE DISTILLATION RESIDUES, THE IMPROVEMENT WHICH COMPRISES PASSING A FEED STREAM CONSISTING ESSENTIALLY OF A VIRGIN DISTILLATION RESIDUE BOILING ESSENTIALLY ABOVE 800* F. THROUGH A VISBREAKING ZONE UNDER RELATIVELY SEVERE CONDITIONS INCLUDING A REACTION TEMPERATURE OF 850 TO 975* F., SEPARATING THE RESULTING HYDROCARBON PRODUCT INTO A VAPOR FRACTION AND A FIRST-STAGE RESIDUAL TAR FRACTION, MIXING AT LEAST A PORTION OF THE SEPARATED TAR FRACTION WITH ANOTHER FEED STREAM OF A DISTILLATION RESIDUE OF AN ASPHALT-CONTAINING VIRGIN CRUDE STOCK BOILING ESSENTIALLY ABOVE 800* F. TO GIVE A MIXTURE CONTAINING ABOUT 15 TO 20 PARTS OF THE TAR FRACTION PER 100 PARTS OF THE VIRGIN STOCK, PASSING THE MIXTURE THROUGH A SECOND VISBREAKING ZONE UNDER RELATIVELY MILD CONDITIONS INCLUDING A REACTION TEMPERATURE OF ABOUT 750 TO 900* F. AND A RESIDENCE TIME CORRESPONDING TO ABOUT 2.5 TO 30 V./V./HR. ABOVE 750* F., THE REACTION TEMPERATURE IN SAID SECOND VISBREAKING ZONE BEING ABOUT 50 TO 100* F. LOWER THAN THE TEMPERATURE IN SAID FIRST VISBREAKING ZONE, SEPARATING THE RESULTING HYDROCARBON MIXTURE INTO A VAPOR FRACTION AND A LOW-SEDIMENT RESIDUAL TAR FRACTION, AND RECOVERING THE LOW-SEDIMENT TAR.