Flooding of a distillation column

Flooding of a distillation column


Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture.

Distillation is a unit operation, or a physical separation process, and not a chemical reaction.


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. 

Depending on the degree of flooding, the maximum capacity of the column may be severely reduced. 

Flooding is detected by sharp increases in column differential pressure and significant decrease in separation efficiency.

The process of distillation is very energy intensive and can contribute to more than 50% of plant operating costs. 

Thus, there is great interest in operating distillation columns as efficiently and reliably as possible.

During this field experiment, the column was operating in 100% reflux mode. Under this mode, the reboiler heat duty could be increased incrementally until flooding was observed. 

The distillation column is instrumented with Foundation Fieldbus devices, and DeltaV is used as the distributed control system.

In this experiment, the structured packing only filled the bottom half of the column. 

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