5 replies to this topic

[kumar123]

Hello all,


I am finding it difficult calculating the amount of steam required to create certain vacuum in a distillation column. 4 stage steam ejector is used to create the vacuum inside the column. Could anyone please guide me how to deal with it.

I have another doubt does the amount of steam changes to create certain vacuum in the column when the amount of vapor coming from the column increases.

Thank you in advance..

[katmar]

The vacuum ejector (or any vacuum pump) on a distillation column is there to eliminate the incondensibles, so the capacity of the ejector depends on the leakage of air into the system and whether there are any incondensibles dissolved in the feed to the column. The steam requirement will also depend on the pressure (depth of vacuum) you want to achieve.

The main driver of vacuum in the column itself is the condenser. Your coolant on the condenser must be cold enough to achieve (better than) the equilibrium temperature in the condenser corresponding to the pressure you want to achieve.

Any incondensibles passing through the condenser will be saturated with the top product, so that would also have to be factored into the capacity determination.

Once you know how much incondensible gas you have to deal with, and the entrained vapor, and you know the pressure you want a vacuum pump supplier will be the best source to get the steam requirement. You could estimate it yourself using (for example) the curves in Perry, but a call to a supplier would be quicker, easier and more accurate.

[Art Montemayor]

I think I've addressed your concerns and difficulties in my Excel Workbook, "Producing and Maintaining a Vacuum", which you will find as a free download in the Forum's Hall of Fame. In it I discuss and illustrate such topics as:

• Notes and Experiences
• Determining Air Seepage
• Process-Generated Gases
• Sizing Example
• Vent Condenser Applications
• Sizing Vacuum Equipment
• Equipment Types

If I have failed to explain what ails you, please let me know so that I can revise the workbook to include that help. I originally put together the workbook trying to help young graduates under my lead who seemed to lack a thorough understanding of how vacuum is produced and maintained.

Basically, the workbook simply elaborates on the basic principles that Katmar has so concisely pointed out.

I cannot seem to find this spreadsheet. Please help. How do I navigate to the Hall of fame?

Edited by jasmine, 12 September 2011 - 05:14 AM.

[breizh]

I've attached the document !

Breizh

Note : From Download to search button you should get your answer

[kumar123]

@ all,

Thank you for your kind replies....