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3

Hot Bypass With Pressure Differential Valve


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#1 Venkat @89

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Posted 03 December 2022 - 11:01 AM

Hi everyone,


We have got Naphtha splitter that splits Naphtha into Light and Heavy Naphtha, whose column pressure is 1.5kgf/cm2g and top temperature is 105degC. Reflux drum pressure is maintained above 0.6kgf/cm2g.

Just want to understand the importance of maintaining pressure in reflux drum via Hot bypass PDV? What factor decides the minimum value of pressure to be maintained in it?


How does variation of pressure via Pressure differential valve in reflux drum affects the top product quality(Light Naphtha).

Attached Files


Edited by Venkat1989, 04 December 2022 - 08:28 AM.


#2 Bobby Strain

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Posted 03 December 2022 - 11:55 AM

What is the normal pressure control for the column? A sketch would help.

 

 

Bobby



#3 Venkat @89

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Posted 04 December 2022 - 05:39 AM

Dear Bobby Sir,

 

As I couldn't upload the pressure control sketch here, posted the same question on industrial forums with Naphtha Splitter PFD, with title naming Importance of maintaining pressure in reflux drum in totally condensable vapor stream. Thank you.



#4 latexman

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Posted 04 December 2022 - 06:59 AM

Venkat1989,

 

Edit your original post, click "Use Full Editor" under the text window, under the new text window attach your files.



#5 Venkat @89

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Posted 04 December 2022 - 07:04 AM

Thanks Latexman, 

 

Attached the Naphtha Splitter PFD.



#6 breizh

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Posted 04 December 2022 - 07:07 AM

Hi,

No attachment.

Breizh



#7 latexman

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Posted 04 December 2022 - 07:42 AM

Thanks Latexman, 

 

Attached the Naphtha Splitter PFD.

 

Breizh says no attachment.

 

Did you "Choose File" and then "Attach This File" and then "Add Reply"?  



#8 Venkat @89

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Posted 04 December 2022 - 08:27 AM

Thanks for the reply.

 

Now it is attached.

Attached Files



#9 SilverShaded

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Posted 04 December 2022 - 01:31 PM

The control scheme is simply that way to allow independant control of two pressures, the drum and column overhead.  The column overhead pressure has to be high enough to push the vapours through the overhead exchangers.  Why the drum pressure is set to 0.8 is probably because its just a typical low positive pressure for design purposes for this type of column.  Maybe someone has a logical reason for choosing 0.8.  Pump Cavitation etc etc??  Ideally we like to operate at the lowest positive pressure possible.

The naptha composition is really only determined by reflux rate and product draw rate (cut point) as this has (at least in design) no vapour coming off the drum (sub-cooled).


Edited by SilverShaded, 04 December 2022 - 01:32 PM.





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