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 said first chamber , a supplemental fuel gas distributor , and a distributor for an oxygen containing gas for distributing oxygen containing gas into said first chamber to contact said spent catalyst and combust carbonaceous deposits and supplemental fuel which further deactivates the spent catalyst and generates flue gas; a riser section extending from said 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 at least one arm extends about the slot from the outer wall and the at least one arm extends from the cover plate at an arm angle (D) of from 10 degrees to 85 degrees, the at least one arm comprising an outer shell that encloses the arm , the outer shell having a top portion and two side portions , and wherein no internal portion of the cover plate extends above an upper surface of the outer shell of the at least one arm , wherein the arm angle (D) is defined between a first line extending parallel to the two side portions of the arm from a centrepoint (A) between the two side portions of the arm , and a second line tangential to the cover plate and passing through a point (B) where the first line intersects an outside edge of the cover plate . a first chamber which comprises a catalyst inlet for feeding spent catalyst with carbonaceous deposits to said first chamber , a supplemental fuel gas distributor , and a distributor for an oxygen containing gas for distributing oxygen containing gas into said first chamber to contact said spent catalyst and combust carbonaceous deposits and supplemental fuel which further deactivates the spent catalyst and generates flue gas; a catalyst inlet for feeding spent catalyst with carbonaceous deposits to said first chamber , a supplemental fuel gas distributor , and a distributor for an oxygen containing gas for distributing oxygen containing gas into said first chamber to contact said spent catalyst and combust carbonaceous deposits and supplemental fuel which further deactivates the spent catalyst and generates flue gas; a riser section extending from said 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 at least one arm extends about the slot from the outer wall and the at least one arm extends from the cover plate at an arm angle (D) of from 10 degrees to 85 degrees, the at least one arm comprising an outer shell that encloses the arm , the outer shell having a top portion and two side portions , and wherein no internal portion of the cover plate extends above an upper surface of the outer shell of the at least one arm , <EOS>