Abstract: An FCC separation arrangement for a catalyst and hydrocarbon contacting zone having a downcomer terminus section uses a compact separation vessel to provide a quick separation between catalyst and hydrocarbon gases in a compact area that also accommodates the use of cyclone separators for a further removal of catalyst from the hydrocarbon gases. The separation system uses a gas collection conduit that incorporates an expansion element for accommodating differential growth between the riser separation vessel and cyclones in the same compact area. The system is suitable for single downcomers or multiple downcomers. The system can be used with a closed containment vessel or in an entirely open system that eliminates the use of a containment vessel.