6 replies to this topic

[Urruth]

Hello

 

I'm working in a project where I must simulate a destilation process with etanol and H2O. 

 

Through the process I got stuck where the column specification should turn into the following:

 

Inlet Flow

stage 14;  98.21 kmol/h;   86.1%mol etanol;   10 atm;   77,98ºC

 

Bottom Product:

19.64 kmol/h;    99.7% mol ethanol;  151°C 

 

Destillated Steam:

78.57 kmol/h;   82.7% mol ethanol;   10 atm

 

column:

28 stages;  10atm.

 

But the results never reaches it. By the way the bottom molar fraction of ethanol never goes higher than the destillated mole fraction of it. 

 

I've tryed to use various specs and the adjust operation.

 

I'm still learning how to use this plataform as i am using it for 2 weeks only.

 

So, i'd like to know if there's a way or any operations to achieve the results i'm needing.

 

Note that it is a experimetal and simulated azeotropic working project.

Edited by Urruth, 01 March 2019 - 02:19 PM.

[latexman]

Are you running into the azeotrope?

[Bobby Strain]

Maybe you should tell us all about this distillation project.

 

Bobby

[Saml]

Your requirement (pure ethanol in the bottom) is valid only if you start on the ethanol rich side of the azeotrope. I don't know the value of the azeotrope at 10 atm. At atmospheric pressure is 89 mole %.

 

Check the thermodynamic package and check at what composition it predicts the azeotrope and if that prediction matchs experimental values.

[Urruth]

The entire process is described on an arcticle, where it says the azeotrope at 1atm is 87,2% then goes down to 79,4% at 10atm. The arcticle has simulations schemes and describes it, but it was running in Aspen Hysys, in the same fluid package( Wilson-RK), I don't know if the unisim system can't run on it. But i think i can't submit the arcticle because of its copyrights. 

 

The reason I told only the second part of the destilation was to try to simplifly the question, because I already simulated all the specifications on the right proportions on the first column. There are 2 columns, one on low pressure and another on high pressure.

 

I've been told that putting the percentage mol value fixed under one variable, like one of the flows, would work, but a couldn't run it yet.

Edited by Urruth, 06 March 2019 - 10:44 AM.

[SadEngineer]

Ethanol and water are azeotrope and later at a certain point, mole fraction is not change.probably aspen hysys is assume ideal conditions

[imeagor]

This is a typical pressure swing distillation (PSD) using two columns one is lower pressure and the other is higher pressure.