Abstract: A hydrocarbon conversion-catalyst regeneration operation and apparatus required is described. Hot regenerated catalyst is mixed with spent catalyst in a first upflow annular fluid catalyst bed regeneration operation about a second concentric downflow fluid catalyst bed regeneration operation. Catalyst flow-through passageways pass catalyst from said downflowing catalyst bed operation to said upflow catalyst bed regeneration operation.

Abstract: A hydrocarbon conversion-catalyst regeneration system is described which particularly relies upon a fluidized catalyst regeneration operation arranged to restrict the catalyst inventory of the system by employing upflowing and downflowing fluid masses of catalyst in cooperative arrangement with one another providing a limited dispersed catalyst phase section and wherein the recycle of regenerated hot catalyst admixed with spent catalyst is controlled principally as a function of the pressure differential between the upflowing and downflowing catalyst masses.