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Vacuum Distillation

steam ejectors pressure increase

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#1 Tara97


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Posted 18 March 2017 - 02:47 PM


I'm a first year ChemEng student and I'm writing a report about vacuum distillation (just general stuff: how it works; how you decrease pressure, etc). I'm using a steam ejector to decrease presure in the column, but I am unsure about it's location. Is it supposed to be inside the column? And where exactly? 

There are 3 vacuum columns in the process and are we supposed to increse pressure of the bottom product before it enters the next column to minimize the impact of external pressure on the pipes and then secrease the pressure again inside the next column?


Thank you!!!


#2 breizh


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Posted 18 March 2017 - 06:07 PM

hi Tara,

I've attached documents to support your work.


hope this helps


Attached Files

Edited by breizh, 19 March 2017 - 03:55 AM.

#3 Art Montemayor

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Posted 19 March 2017 - 10:25 PM



I am concerned that as a 1st year Chemical Engineering student you are setting out to write a paper that “reports” on the subject of vacuum distillation.  My concern is based on the manner in which you relate to what you don’t know about the subject at hand.


In order to write anything on this subject, you should at least be familiar with the subject matter itself, the principles, and the equipment that it operates under.  You don’t seem to know the principle of fluid transport - the movement of fluids through a system and how to apply this principle.  Start with the basic knowledge required: A vacuum is a system totally or partially devoid of gas or vapor particles such that there exists a very low vapor pressure within the system.  That means you must devise a means to transport the gaseous molecules inside your distillation column to an external space, leaving a vacuum (actually a partial vacuum, since a total vacuum is practically not achievable) inside.  You should know that this can be done by applying a steam jet ejector that operates on the principle of a venturi.  You should study and know how a venturi accomplishes the development of a vacuum.  You can also apply other means besides a venturi jet, such as a liquid ring vacuum pump, a rotary positive displacement blower, etc.  You should know this before starting to write.  Study the material that Breizh has so kindly submitted to you and you will have answers to your basic questions.  Use your common sense to decide where you place the steam jet: you are trying to eject gas, so you obviously would place the jet downstream of all overheads vapors that are generated in your column(s).  Be aware that no distillation system is "leak-proof" and that external air will always migrate into your vacuum system from the outside atmosphere.  You have to allow for this in the design of your vacuum system's capacity.


I am attaching additional documents to complement what Breizh has submitted.  I hope this material helps you understand what you are confronting.


You have to do your share of identifying and studying all the material that you report on.  Otherwise, you simply don’t know what you are doing.

Attached File  Producing and Maintaining Vacuum Rev1.xlsx   372.8KB   23 downloads

Attached File  Vacuum_Distillation_Column_Design_and_Control(1).xlsx   67.86KB   35 downloads

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