Long cool-down tube with air input joints

A method of conditioning a mixture stream, the method comprising:

• providing a conduit formed by a surface extending from a first end to a second end, wherein a plurality of fluid delivery features are disposed along the conduit between the first end and the second end, and wherein each fluid delivery feature comprises a port structure fluidly coupled to the interior of the conduit and an annular housing disposed around the conduit and covering the port structure, the annular housing comprising a fluid supply port;
• flowing the mixture stream through the conduit from the first end to the second end;
• and
• delivering a conditioning fluid into the conduit while the mixture stream flows through the conduit, wherein the conditioning fluid is flown through the fluid supply port of the annular housing to the port structure where it is delivered through the port structure of each of the delivery features disposed along the conduit between the first end and the second end, each fluid delivery feature delivering the conditioning fluid into the conduit in an annular formation in a direction angled towards the second end in the same direction as the flow of the mixture stream, thereby providing a sheath of conditioning fluid between the conduit surface and the mixture stream.