Stripper for fluidized contact solids

Claim 1

IN A PROCESS WHEREIN HYDROCARBONS ARE CRACKED IN A CONVERSION ZONE AT CONVERSION CONDITIONS IN CONTACT WITH A DENSE, TURBULENT BED OF FLUIDIZED CATALYST, THE IMPROVED STRIPPING METHOD WHICH COMPRISES OVERFLOWING A MIXTURE OF FLUIDIZED PARTIALLY SPENT CATALYST AND HYDROCARBONS FROM THE DENSE BED INTO A PLURALITY OF ADJACENT CONCENTRIC ANNULAR STRIPPING ZONES, PASSING THE FLUIDIZED CATALYST MIXTURE THROUGH THE ANNULAR STRIPPING ZONES AS HELICAL DOWNWARD STREAMS, THE ROTATION OF THE HELICAL STREAM IN ONE ANNULAR STRIPPING ZONE BEING IN THE OPPOSITE DIRECTION TO THE ROTATION OF THE HELICAL STREAM IN AN ADJACENT STRIPPING ZONE, THEREBY COUNTERBALANCING THE TORQUE PRODUCED BY THE FLOW OF THE CATALYST, INJECTING A PLURALITY OF SPACED STREAMS OF AN INERT STRIPPING GAS AT THE BOTTOM OF EACH ANNULAR STRIPPING ZONE AND ALLOWING THE GAS STREAMS TO RISE IN A SUBSTANTIALLY VERTICAL DIRECTION, THEREBY CAUSING EACH HELICAL STREAM OF CATALYST TO CROSS A PLURALITY OF THE SAID RISING GAS STREAMS, AND WITHDRAWING STRIPPED CATALYST FROM A BOTTOM PORTION OF THE SAID ANNULAR STRIPPING ZONES.