Effect of Downcomer Design in Distillation at High Pressures

Distillation at higher pressures require careful considerations for the design of downcomers because the flooding mechanism is often governed by downcomer flood. Studies on trayed columns have shown that the mechanism of coalescence and separation of the two-phase liquid-vapor mixture in the downcomer is significantly more complicated as pressure increases. In terms of design of the downcomer, both the downcomer entrance area as well as the area available for the two-phase flow of froth within the downcomer are of importance. In this presentation, we describe research on downcomer performance conducted by FRI’s legendary expert - Tak Yanagi. An analysis and interpretation of his findings on the effects of downcomer design in high-pressure distillation will be discussed.