2 replies to this topic

[juuichi]

Hi everyone,

 

For my project, there is a filter dryer in which the contents shall undergo vacuum distillation - heating up and pulling a vacuum in the filter dryer (via vacuum pump) in order to remove solvent vapor, which then gets condensed at the overhead condenser.

 

With regards to the Operating Pressure in the filter dryer, I am rather confused. Is it physically possible for it to be less than the vapor pressure of the solvent?

 

My take is that it is not possible, as at the low operating pressure, the higher vapor pressure will cause the solvent to boil, which will then ultimately increase the operating pressure. So its not physically possible for the operating pressure to be lower than the vapor pressure of the solvent. The operating pressure has to be at least at the vapor pressure. I don't know if I am right, and I would really appreciate any enlightening advice.

 

Cheers

Kai

 

[Art Montemayor]

The operating pressure existing inside a filter drum (I am assuming that is what you have: a filter drum rotating continuously in a bath of material to be filtered) with a vacuum being pulled through the drum's shaft will always be less than the liquid fluid's vapor pressure.  In order  for there to be vapor flow from the drum to the final vapor total condenser, there MUST BE A PRESSURE DROP.  Pressure is the driving force in any fluid movement within a closed system.  In this case there is a differentially decreasing pressure downstream where the vapor is being condensed.  Without a pressure drop, there wouldn't be any vapor flow.

 

You (and all other members submitting queries) should always supply a detailed sketch of your system.  There are many different type of dryers out there and they work in different ways.  Engineering descriptions and explanations should always be done with drawings or sketches because our profession is such that we don't communicate like poets or writers of novels.

[juuichi]

Thanks I've got it sorted.Yes indeed it should be less and it is physically possible.