Described is a catalyst regenerator system that includes a regenerator vessel within which is a verticaliy extending partition that divides a fluidized bed zone of the regenerator vessel into a dense phase fluidized bed zone and a fast-fluidized bed zone. Apparatus is provided to introduce spent catalyst into the fast-fluidized bed zone and to remove regenerated catalyst from the dense phase fluidized bed zone. The partition is equipped with openings that provide for the flow of catalyst from the dense phase fluidized bed zone to the fast-fluidized bed zone.