4 replies to this topic

[Shim.94]

I am currently doing a design project and would wish to design an extractive distillation column to separate o-xylene from xylene isomers.

 

I've met a difficulty when designing this column. I am using Aspen HYSYS for my design at the moment and have chosen UNIQUAC as my fluid package. However, it does not change the relative volatility of m-xylene to o-xylene as suggested by a patent when the solvent is added. I do not have the experimental interaction parameters. I have used different solvents for this case and none of them was able to have any effects on the relative volatilities of the xylene isomers.

 

Is there any way around this problem? Your help is very much appreciated.

[Bobby Strain]

The separation is usually accomplished with simple distillation. So, why would you wish to use extractive distillation?

 

Bobby

[Shim.94]

Hi Bobby,

 

Thank you for suggesting that. I have read through a couple of processes stating the fact that they are normally done by simple distillation.

 

However, I have done a simulation using simple distillation and I have gotten 135 stages for the distillation column when it is operated at atmospheric pressure. Therefore, I was wondering whether designing an extractive distillation column would be beneficial for the process. 

[Bobby Strain]

The separation is usually part of paraxylene production. And it is typically placed after paraxylene recovery, typically with molecular sieves. You should look at this flow scheme when considering orthoxylene recovery. Good luck. You don't want to waste much of your valuable time on projects such is this. Your main objective should be learning fundamentals of Chemical Engineering. I don't understand why today's students are required to learn process simulation. Anyone can learn to do this soon enough after acquiring fundamental skills.

 

Bobby

[latexman]

IMO, extractive distillation doesn't seem very promising.  Why would one isomer associate significantly more or less than the other isomer?  I don't see it happening to the extent it justifies another column, heat exchangers, pump, etc. to recover the extractant.

Edited by latexman, 12 March 2017 - 09:40 AM.