To vacuum or not to vacuum ethanol: A Solvent Recycler Drama

[tom_kha]

I have recently started a new project as a process engineer working with solvent recyclers. We are looking to optimize our solvent recovery per hour. We are a high volume company and looking to recover thousands of liters of ethanol a day.

 

The boiling point of ethanol is 79 C. Under vacuum (28 inHg) it drops to around 34 C. We add 50 degrees Celsius to the boiling point of the solvent in order to maintain boiling throughout the solvent. For ethanol, in normal atmosphere, we would use a temp of 130 C. Under vacuum it should be a temp of around 85 C.

 

What I've found is, despite the vacuum, I need to maintain the temp around 130 C to get the same distillation rate as without the vacuum.

Has anyone found it is better to distill ethanol without a vacuum as opposed to with?

Why does the ethanol still require such a high temp with the vacuum?

With such a high temp, I have not seen an increase in distillation rate. Why is this?

Thanks so much for your help and wisdom.

-Tom Kha, J.O.

Edited January 9, 2016 by tom_kha

[Sensei]

This looks like repeating of what has been said in this thread... Nearly word by word..

http://www.scienceforums.net/topic/87701-vacuum-distillation-of-ethanol/

[tom_kha]

Indeed, the same problem. Sorry that ethanol does not change boiling points between threads...

 

Still looking for an answer to this dilemma. No insight has been given to resolve it and I am trying to press to an answer.