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Composite Curve For Distillation Column

hidic heat integration distillation column energy savings

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#1 panoskagiou

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Posted 15 April 2018 - 09:00 AM

Hello everyone I would like to simulate the internally heat integrated distillation column in ASPEN PLUS. But before that I need to generate the composite curve (T-H) of the distillation column (the conventional one). I have seen this graph in many papers, I attach one of it. Could you please help me?

 

Thank you in advance!!

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#2 serra

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Posted 16 April 2018 - 08:34 AM

not sure with Aspen,
however it should be as many software applications such as Prode Properties give as output temperatures, pressures plus vapor and liquid flows on each tray, from those you can calculate Hin, Hout on each tray,
if you wish to evaluate the minimum thermodynamic condition for a distillation column (reboiling and condensing loads distributed over the temperature range of operation of the column) you can start with a stage - enthalpy or grand composite curve,
as far as I know the solution is not easy, there are papers discussing binary distillation but with multicomponent mixtures there are several limits....



#3 panoskagiou

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Posted 17 April 2018 - 01:15 PM

Ok I see. Generally in each stage, the vapor and the liquid enthalpy are calculated. But I cannot really understand how these two can be combined. 

Thanks for the answer!



#4 serra

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Posted 18 April 2018 - 01:54 AM

knowledge of mass & heat transfer on different trays (plus hot / could utilities etc.) allows to determine overall efficiency of process, for a short introduction see

http://nptel.ac.in/c...e1/lecture1.pdf

 

there are also several good books with detailed discussions.


Edited by serra, 18 April 2018 - 02:06 AM.


#5 panoskagiou

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Posted 18 April 2018 - 03:02 PM

I used ASPEN PLUS for the simulation of the column, so what I was thinking is to use the vapor and the liquid enthalpies that are calculated in each stage. What I mean I will multiply the vapor enthalpy with the vapor molar flow rate in each stage the same for the liquid. And after that I will sum these two. What do you think about this approach?

 

Let me write with expressions:

Htotal=Hliq*molar rate of liquid+Hvapor*molar rate of vapor and I will have the duty of each stage.

Sounds reasonable??

 

Thank you in advance!



#6 serra

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Posted Yesterday, 02:14 AM

for intermediate stages (no feeds, no side streams, no heat added removed) 

H (vapor inlet - vapor outlet) = H (liquid inlet - liquid outlet)

Prode Properties exports these values, I presume Aspen Plus does the same (you can easily verify)

 

added : (heat balance) H(Vin)+H(Lin)=H(Vout)+H(Lout) -> H(Vin)-H(Vout) = H(Lout)-H(Lin) -> ...


Edited by serra, Yesterday, 03:50 AM.


#7 panoskagiou

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Posted Today, 03:24 PM

Thank you for the answer. 






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