A catalyst regenerator for combusting carbonaceous deposits from a catalyst comprising a first chamber which comprises a catalyst inlet for feeding spent catalyst with carbonaceous deposits to the first chamber, a supplemental fuel gas distributor, and a distributor for distributing oxygen containing gas into the first chamber; a riser section extending from the first chamber for transporting the spent catalyst and the flue gas, the riser section comprising an outer wall, at least one slot in the outer wall, and a riser termination device which comprises a substantially internally flat cover plate, at least one arm extending from the cover plate, wherein the arm extends about the slot from the outer wall, the arm comprising an outer shell that encloses the arm and wherein no internal portion of the cover plate extends above an upper surface of the outer shell of the at least one arm is provided.