How will increasing/decreasing the pressure of the distillation tower affect flooding?

Flooding occurs if vaporization rate of reboiler is higher, then liquid partially carryover by the vapors from below tray to above tray, if it is continue then liquid hold up on the above tray increases and causes flooding

Naturally we don’t want to over pressure the tower and open the safety valve, Same way if tower pressure goes too low then we could not condense the reflux, then the liquid level in reflux drum would fall and the reflux pump would lose suction.

Now Take

1. Raising the tower pressure

Higher pressure reduce volumatric flow of vapor, (As the Pressure is inversely proportional to Volume), So increasing the tower pressure does not Causes Flooding but its a one of the option to reduce the effect of Flooding .

Now the question is why we are increases the Tower Pressure?

so the answer is to permit higher reflux rates.

2. Decreasing the tower pressure

Generally Distillation columns are operated at low pressure,

Because as the tower pressure will decreases the vaporization rate will be increases and thus chances to occurs flooding will be increases.

But why we are decreases the tower pressure?

the answer is reducing tower pressure will increases relative volatility.

Comments

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