3 replies to this topic

[mayuresh]

If anyone out there have a moment to spare.

 

i am having difficulty in understanding the concept of "Reflux Ratio". there is much hype around this paticular topic.

How does one finalize upon the Optimization in this regard.

are there any topics i should probably be aware, before i go about reading this topic.

Is zeroing in on a particular refulx ratio, based on various different factor. if it is then, any precise guidance will be very much appreciating.

 

hope i was pretty close to presenting my doubt.

Thanks to all, thanks for your valid help, Mayuresh.

[Zauberberg]

Hi Mayuresh,

 

Every single mass transfer textbook explains the concept of reflux ratio in plenty of details. I suggest you use Google as the source of information - for example:

 

http://www.separatio...n/DT_Chp04n.htm

http://www.che.ufl.e...tion-theory.pdf

http://lorien.ncl.ac...l/distildes.htm

[mayuresh]

Thanks Zauberberg for the Links. Would surely go through all the links.

[PingPong]

Mayuresh,

You should understand that distillation and fractionation is affected by the L/V ratio (or V/L ratio) in each section of the column. However measuring the V and L at any point inside the column is not possible. The reflux flowrate however is easy to measure, and therefor the equations in hand methods like McCabe-Thiele are written in terms of reflux ratio R. It is then asumed that V and L are constant in each section of the column: equimolar overflow, so L/V ratios can be written in terms of R.

 

The boil-up ratio is also important, but as it cannot easily be measured hardly anybody talks about it. You probably never heard of it.

But reflux ratio and boil-up ratio are related in McCabe-Thiel: if you know one, you can easily calculate the other. In fact: one could rewrite all equations in terms of boilup ratio instead of reflux ratio. But because boil-up ratio can in practice not be determined, nobody does.

 

In reality however there is no equimolar overflow, so simulators don't work with equations based on R but rigorously calculate V and L at each theoretical stage (usually from the stage heat balance) and use those, together with the K-values of all components, to calculate the separation in the column.