What is Downcomer flooding in distillation column?
Downcomer Flooding:- In distillation column, liquid flows in downward direction by gravitational force but it flows against the pressure. When liquid flows from one tray to next below tray, it flows from lower pressure to higher pressure. Hence, to compensate that, it elevates certain level inside the downcomer.
What is Downcomer flooding?
Downcomer backup flooding occurs when the hydraulic head requirements to flow liquid through the downcomer exceed the height of the downcomer itself. The liquid level in a downcomer behaves in a similar manner to a manometer as shown in Figure 1.
What happens when a distillation column floods?
Distillation is a common unit operation, which is used to separate or purify components in a feed stream. Flooding is a common abnormal process condition wherein the distillation column stops generating a separation, thus causing the quality of the top and/or bottom products to go off specification.
What is Downcomer in distillation column?
Downcomer: A device to direct the liquid from a distillation column at a location above the bottom tray and below the top tray.
What is Downcomer backup flooding?
Downcomer Backup flooding_Aerated liquid backed up into the downcomer because of increased tray pressure drop or liquid height. When this backup exceeds the tray spacing, liquid accumulates on the tray above, causing downcomer flooding.
How do you fix a weeping in a distillation column?
If the reboiler produces low amount of vapour and send into the column, it will cause this type of problems. If we maintain the Vapour flow rate in constant level, we can overcome this problem . Otherwise we will go for the bubble cap contractor or valve tray to avoid weeping.
How can you prevent a distillation column from flooding?
Some of the more common methods used to eliminate flooding involve temporarily decreasing the feed rate, the reflux rate, or both, to reduce the amount of liquid in the column, and decreasing the vapour in the column by reducing the reboiler steam.
What is a downcomer pipe?
Definition of downcomer : a pipe to conduct something downward: such as. a : a pipe for leading the hot gases from the top of a blast furnace downward to the dust collectors and flue system.
What is column flooding factor?
Flooding. Flooding is brought about by excessive vapour flow, causing liquid to be entrained in the vapour up the column. The increased pressure from excessive vapour also backs up the liquid in the downcomer, causing an increase in liquid holdup on the plate above.
What is the difference between entrainment flooding and downcomer flooding?
Froth entrainment flooding occurs at higher liquid rates. When vapour velocity is increased, the froth height increases. Downcomer choke flooding occurs when the liquid flow rate increases until such a point that the velocity of the aerated liquid in the downcomer exceeds a certain limit.