So 50 percent is often used for many hydrocarbon services. The factor that compensates aeration effect is 0.5. The liquid actually is froth or foam in nature which is called aerated liquid. The pressure drop of the vapor flowing through the tray above the downcomer.īut in the actual scenario, there is no clear liquid exists either in the downcomer, on the tray itself, or outlet weir.Height of the Crest of liquid overflowing the outlet weir.Liquid exit velocity from the downcomer onto the below tray.At the same time, all trays below downcomer B will get dry on the loose liquid levels. This condition will be continued till all the trays and downcomers above downcomer B are flooded. Once tray-2 floods, downcomer C (shown in Fig. If the bottom edge of the downcomer is too adjacent to the below tray then a higher pressure drop is needed for the liquid to escape from downcomer B onto tray-1 & which causes the liquid level in downcomer B to back up onto tray-2. The next reason for flooding is inadequate clearance of the downcomer and tray deck which is shown in the figure below (Fig-2). The vapor pushes the liquid up onto the tray above which is the main reason for flooding. The upgoing vapor drives away the downflowing liquid. This allows the vapor to flow upwards to downcomer B. The height of the outlet weir is less than the bottom edge of the downcomer from the upper tray. The reason is the loss of the downcomer seal. This condition is called flooding of the distillation column.Īdvertisements Cause of Flooding in Distillation Column Loss of downcomer sealĪs per the figure depicted in Fig.1A, it has been clearly shown that downcomer B is flooding. This foam should separate back into a vapor and a liquid in the downcomer & if it is not drained fast from a downcomer onto the below tray, then the foamy liquid or froth will back up onto the tray above. The function of a tray is to mix the vapor and liquid together to form foam. Vapor bubbles through the holes of the sieve trays, or caps of the valve trays, on the tray deck, where the vapor comes into intimate contact with the liquid. The liquid starts overflowing the outlet weir and drains through the downcomer to the tray below. What is Flooding of Distillation Column?įlooding of a distillation column is a phenomenon when liquid flows across a tray and goes toward the outlet weir. The next problem may lead to the ‘flooding’ of the tower.Įntrainment is expressed as kg (droplet entrained)/s, kg/kg vapor, kg/kg liquid flow, or kmol/ kmol liquid flowing.The carryover of a substantial mass of liquid as droplets into the upper tray increases the liquid flow rate and downcomer load of that tray.This adversely affects the mass transfer which reduces the tray efficiency. It causes the mixing of the entrained liquid from the lower tray with the liquid on the upper tray.
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