5 replies to this topic

[icingrock]

 Diagram.pdf   275.62KB   97 downloads

A general question to seek reference book/comments/rule of thumb from experienced engineers.

A typical situation is:
A vacuum distillation column operated at elevated temperate (say 0.1bara and 150 degC), at the bottom of the column, some volume is needed either for reboiler or the sump of the column itself to have a "good" disengagement of gas and liquid so that not too much gas goes to liquid pipe to the pump suction to cause cavitation.

I heard from an engineer about it actually happened and would like to ask to share your experiences/comments/reliable rule of thumb for design of sump to avoid this.

Thank you and please find the attachment of an idea of what I am talking about.

Edited by icingrock, 22 February 2012 - 11:20 PM.

[breizh]

<sup>Good day ,

I encourage you to find a copy of : Distilation design by Henry Z Kister .
Hope this helps

Breizh</sup>

Edited by breizh, 25 February 2012 - 02:43 AM.

[icingrock]

Breizh,

Thank you for the reference, it point to my question to some degrees, but not to the point.

The rule of thumb of about residue time (FIG. 19-41 Residence Time for Liquid in the Sump) is more based on how to maintain the process continuity without shutdown. While my question is more about enough residence time to have adequate gas-liquid separation to protect pump cavitation (Pobably with enough liquid height in the sump), although I personally did not experiences this problem. Probably the reason for the pump cavitation is NPSH problem combined with gas entrainment.

But I also remember Kister touched this topic somehow in his classic books, And I will look at it when I have access to the book.

I am wondering if the The Souders-Brown equation will apply to some degree here.

Please advise.

Edited by Art Montemayor, 03 March 2013 - 01:23 PM.

[breizh]

My experience is about having a stable mesurement of the level to avoid upset on thermo syphon and cavitation on the pump . We were using gama ray level transmitter .

Better than Kister Distillation design consider Kister Distillation Operation .
Breizh

[James.bruce]

I'm interested in those posts..

 

Can you advise of the source for the PDF files you posted.. i've a slightly different system i'm looking at with linked columns, but looking to design a smaller sump for lower hazardous inventory.  Particually the residence time with reference 21. 

[breizh]

GPSA engineering data book

 

Breizh