6 replies to this topic

[mb23]

Dear all,

I would like to understand how exactly the column efficiency is affected by varying the reflux flow?

It is clear that reflux flow helps to achieve the desired T95 of distillate, I would like to understand, what happens if I maintain more reflux flow than required and less flow than required,in both cases maintaining top temperature of the column constant. In terms of quality of top and bottom products and tray efficiency.

Does Distillate and Bottom product quality in terms of T95 and T5 vary with variation of reflux at same column top temperature?

Note: Assuming the minor changes of reflux flow increase and decrease such that, it doesn't lead to Incipient flooding nor weeping.

Edited by mb23, 21 September 2022 - 10:06 AM.

[breizh]

Hi,

Sorry to ask the meaning of T95 and T5!

For tray efficiency consider the doc attached .

Breizh

[horatorres]

It is not as simple as you set. I recomen to start with  distillation desing Henry Kyster

 

Horacio

[mb23]

Hi,
Sorry to ask the meaning of T95 and T5!
For tray efficiency consider the doc attached .
Breizh

[mb23]

Dear Breizh,

T95 is the temperature to vaporize 95percent of the distillate or any product stream from fractionation column.


T5 is the temperature to vaporize 5percent of any product stream from fractionation column

[Nikolay_]

Hi,

 

Minor changes of reflux flow make minor changes in T95, T5.

 

Column top temperature depends on T95. To increase reflux you need to input more heat and less efficient trays are needed in this case. 

[SilverShaded]

Column top temperature is affected strongly by the T95 of the top product.  Essentially its how heavy you pull the top product determines the top temperature.

 

Increasing reflux, either by adding more heat in a reboiler/feed or by decreasing a pumparound lower down the column will improve separation and at constant product rate will increase the T5 distillation point and decrease the T95 distillation point, yields can then be adjusted back to whatever product spec your running to.

The proviso is that you don't increase entrainment up the column which can make the T95 worse.