Stripping in fluid coking

Claim 1

IN A PROCESS FOR COKING A HEAVY HYDROCARBON OIL WHICH COMPRISES THE STEPS OF CONTACTING THE OIL COKING CHARGE STOCK AT A COKING TEMPERATURE WITH A BODY OF INERT PARTICLES HAVING AN AVERAGE PARTICLE SIZE IN THE RANGE OF 100 TO 400 MICRONS MAINTAINED IN THE FORM OF A DENSE, TURBULENT, FLUIDIZED BED IN A REACTION ZONE HAVING A LOWER CONFINED STRIPPING SECTION, REMOVING PRODUCT VAPORS FROM THE REACTION ZONE, CIRCULATING THE PARTICLES THROUGH AN EXTANEOUS HEATING ZONE WHEREIN A PORTION OF THE PARTICLES ARE HEATED AND BACK TO THE REACTION ZONE TO SUPPLY HEAT THERETO, AND WHEREIN OVERSIZED PARTICLES LARGER THAN SPECIFIED ACCUMULATE AND HAVE TO BE REMOVED, THE IMPROVEMENT WHICH COMPRISES THE STEPS OF SCREENING THE OVERSIZED PARTICLES IN AN ANNULAR SCREENING ZONE ABOVE AN ANNULAR STRIPPING ZONE, WITHDRAWING THE OVERSIZED PARTICLES FROM THE STRIPPING SECTION THROUGH A CONFINED CONDUCTING ZONE COUNTERCURRENT TO INJECTED FLUIDIZING GAS FOR THE DENSE BED, SAID CONDUCTING ZONE EXTENDING CENTRAL OF THE STRIPPING SECTION AND DEFINING THE ANNULAR STRIPPING ZONE, SENDING PREDOMINATLEY ALL THE CIRCULATING PARTICLES FROM THE COKER INTO THE ANNULAR STRIPPING ZONE FREE OF OVERSIZED PARTICLES, STRIPPING THEM WITH AN AUXILIARY INERT GAS AT A SUPERFICIAL VELOCITY LOWER THAN THAT OF THE FLUIDIZING GAS AND CIRCULATING THE THUS STRIPPED COKE FROM THE ANNULAR ZONE TO THE EXTERNAL HEATING ZONE.