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Kettle Reboiler Sizing

heat exchanger heat transfer kettle reboiler shell and tube heat exchanger stripper regeneration

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#1 chyke7

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Posted 17 January 2018 - 05:39 PM

Hi Everyone, I am sizing a kettle reboiler (stripper column with a pressure of 190 kPa) using a commercial process simulator (ProMax), however, I ran into some problems and this seems to be solved when I specify a pressure drop of 25 kPa (3.625 psi) in the shell side.

 

Please, from experience, what is the recommended (thumb rules) pressure drop for the shell side of the kettle reboiler?

 

In addition, is it common to have shells in parallel for kettle reboilers?

 

 

Thanks for your anticipated assistance.



#2 Art Montemayor

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Posted 17 January 2018 - 07:11 PM

Could you please explain how it is that you expect a pressure drop to exist in the shell side of a kettle reboiler?

Doesn't your solution enter the shell side of the reboiler as over flow from the bottom of your stripper, flow laterally through the length of your tube bundle via convection currents until it reaches a weir that allows for overflow of the same liquid?   While this procedure is happening the upper space of the kettle (shell side) is filled with stripping vapor AT THE SAME PRESSURE THROUGHOUT THE LENGTH OF THE KETTLE.

 

The reason the shell side liquid "flows" from one end of the kettle to the other is because it falls by gravity into the shell, fills the tube bundle section of the reboiler and rises in level as it fills that section up to the weir's height, where it falls by gravity into the weir's downstream section to be sucked by the suction of the rich solution pump.

 

I believe under the above described conditions the "pressure drop" across the length of the kettle's internal liquid space is essentially ZERO.  Please correct me if my description and response are wrong, but that is the logic I've always used in designing and building my kettle reboilers in the past.



#3 chyke7

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Posted 17 January 2018 - 08:10 PM

Hi @Art Montemayor,

 

You are actually right.  I have attached a screenshot of the stripper connected to the reboiler and other preliminary sizing data. In addition, is it common to have kettle reboilers with shells in parallel?  

Attached Thumbnails

  • C1.PNG
  • C2.PNG
  • C3.PNG


#4 Bobby Strain

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Posted 17 January 2018 - 10:47 PM

You can have as many reboilers as you like. Kettles or otherwise. I have even used a kettle in series with a vertical shell & tube exchanger.

 

Bobby



#5 chyke7

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Posted 17 January 2018 - 11:12 PM

Hi @Bobby

 

Thanks for your response. Please, from your experience was there any form of pressure drop on the shell side of the kettle reboilers?



#6 Bobby Strain

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Posted 18 January 2018 - 10:20 AM

Most all the pressure drop is for inlet and outlet nozzles. If you use an exchanger design/rating software you will see this. Never use a process simulator for details on heat exchangers. They are only adequate for energy and material balances.

 

Bobby



#7 chyke7

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Posted 18 January 2018 - 01:08 PM

Hi @Bobby,

 

Many thanks for your explanation. It is very helpful.

 

Kind regards

 

Chike



#8 srfish

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Posted 19 January 2018 - 02:27 PM

It is not common to have kettle reboilers in parallel I have seen a problem when this is done. Every bit of the piping has to be identical or there will be problems.



#9 Bobby Strain

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Posted 19 January 2018 - 07:53 PM

And the secret is to use butterfly valves in each liquid inlet. Set once and forget.

 

Bobby



#10 Art Montemayor

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Posted 20 January 2018 - 11:40 PM

chyke7:

 

In the opening paragraph of my response to your question I asked you a direct question: Could you please explain how it is that you expect a pressure drop to exist in the shell side of a kettle reboiler?

 

You did not reply to my question and merely inferred that I am right.  I have tried to show you a failing that you exhibit: you haven't logically looked at the reboiler you are trying to simulate.  If you follow what I have outlined for you in logical steps you will have achieved a Lesson Learned.

 

I hope you can see how clear the answer to your question is.






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