Does the reflux divider represent the reflux ratio (L/D) ?

[Theophile]

Dear everyone

I am trying to simulate the pilot distillation column in ASPEN plus. This column doesn't have a reflux drum, it employs
a reflux divider instead.

I'm not sure that the reflux divider can represent the L/D ratio or not because R/W ratio in the reflux divider
operation represents the time (second) to close and open the divider, it doesn't represent flow rate ratio in my understanding.

Give me some idea please
Thank you so much for your help

 

[StoneCold]

In theory the divider will represent the L/D ratio as it is supposed to be a percent of the total time on stream.
In reality most of the time the reflux is so subcooled that when it re-enters the column it knocks down a bunch of vapor and your reflux ratio is higher than you think.
Heat losses in the column also contribute to a higher reflux ratio than the splitter represents.

You really have to run the process and take GC samples of the distillate in real time to get the actual composition.
Since you are doing batch distillation your composition is changing all the time anyway.

So in the real world you take a front cut and either recycle that or throw it away.
Then there is the product cut which is hopefully most of your material.
Then there is often a bottom cut that is left in the still that you have to do something with.

The trick in the real world is to get from front cut on to product cut quickly so you can maximize your product cut.


Regards
StoneCold

 

[Theophile]

Dear StoneCold
Thank you very much