Heat required when using a vacuum to lower boiling point

[lsume]

I was very recently reading a question regarding the extraction of solvents using negative pressure and why more heat was neccesary.  If I’m correct regarding the question, I may have an answer.  I’m now a retired mechanical engineer but early in my career I was the chief engineer in two large co-gen processing facilities.  I assume that you are using a barometric condenser to establish the vacuum.  What can happen is that the vacuum itself will pull more energy than what is required to maintain the lowered boiling point.  Hence, more energy is required to maintain the boiling point.  If you were dealing with a closed system, this phenomenon wouldn’t be a problem but that is not your case.  When the solvent is condensed, it then enters an open system.

i hope that I have the question and set-up correct and that whomever posted it gets this response.

Edited April 11, 2018 by lsume
I found the post of the person asking for help