5 replies to this topic

[chemkravi]

In High Vacuum/Vacuum Distillation, Why The Vacuum Line Connected In The Top Of The Column/Condensor?

[aroon]

Please elaborate your question a bit.

[markymaark]

Where else would you want to place it?

 

You don't want it at any liquid level

[Art Montemayor]

ChemKravi:

 

You seem to lack an understanding of how a vacuum system is supposed to work - and why.  That's OK; it seems a lot of engineers today - especially younger ones - don't have a clear idea of what constitutes a vacuum system and how it is supposed to operate sucessfully.  However, you bring out a very important point: it not only is necessary on knowing how a vacuum system works - but also, WHERE in the affected system the vacuum "puller" is supposed to be installed.  In my 54 years as an engineer I have never found anyone - professor, text book, technical paper, or journal that clearly indicates where the best physical location for a vacuum connection is called for.

 

This is a complex question and the answer is: it depends.   It depends basically on the configuration of the actual, physical equipment and the various flow paths that the non-condensable, gaseous compounds/elements take.   The best way to answer this type of question is to review the equipment layout and piping isometrics.  In your case, the general answer is that is is supposed that the air and other non-condensables will all flow directly to the "end" of the gaseous process, which is at the coldest/highest portion of the overhead total condenser.  But this is based on conjecture because we don't have a detailed, accurate drawing.

 

For an explanation of the vacuum system and how it should work, refer to the attached workbook that I put together many years ago to tutor young engineering graduates.  I hope it helps out.

 

 Producing and Maintaining Vacuum.xls   145.5KB   45 downloads

[Mahesh@A&M]

ChemKravi:

 

I worked on couple of projects involving  overhead condensers for vacuum distillation.

 

I installed BJ21M exchanger with the non condensable venting from the top and center section of the condenser. In another project, we installed a cross flow  condenser with the vent at the top and far end of the exchanger. The reason being is to cool the vapor to improve the operability of the vacuum pump.

[S.R.Shah]

Chemkravi

 

You are supposed to use overhead condenser over

fractionating

 

column ,in which all vapors that leave from top of the fractionation  column 

and reached to overhead condenser,

 

Vacuum is applied to top vent nozzle on condenser(single condenser -No secondary condenser

This shall facilitate

Solvent vapor reaches to condenser heat transfer surface,It get condensed get back and leaves for separation chamber for separating between Reflux and product.If it is placed to other location there are chances that solvent vapors does not reach to condenser 

Heat transfer surface and directly pulled uncondensed to vacuum source

 

SRShah