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Distillation Column: Increase Purity In Hysys


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#1 jmea

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Posted 15 November 2015 - 12:03 AM

Hi! I'm simulating a vinyl acetate plant using ASPEN Hysys V8.6. I have a mixture of acetic acid-H2O-vam and in my first distillation column, I have already separated acetic acid leaving me with a vam-H2O mixture. The vam-H2O mixture will then enter another distillation column. But this time, I'm not able to purify vam to 99.99%. Do you guys have any tips for me to increase the purity? 



#2 AlertO

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Posted 15 November 2015 - 10:51 PM

hi jmea

 

i've never performed VAM-H2O seperation before but i think the separation problem is your purity speciffication is higher than the azeotrop point. i may need more equipment for separate them.

 

Do you have a simplify diagram of the process to perform the simulation? If not, you may need more information.

 

Anyway, if you have more information, please share to us.

 

good luck



#3 PingPong

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Posted 16 November 2015 - 05:01 AM

VAM and water form a minimum boiling azeotrope. At atmospheric pressure that azeotrope has a boiling point of 66 oC and composition is 75 mol% VAM / 25 mol% H2O , which is 93 wt% VAM / 7 wt% H2O.

 

The good news however is that VAM and H2O do not mix completely, so you can separate them in the reflux drum of the first distillation column that removes the acetic acid as the bottoms product.

Solubility of VAM in H2O, as well as H2O in VAM are only a few wt%.

 

So you have to model the distillation such that water can be decanted from the reflux drum.

 

Both the wet VAM and the decanted water can be distilled further in two separate columns to produce an azeotropic overhead product, that is recycled to the first column. The bottoms of both columns are then nearly pure VAM and nearly pure water.

 

Read section 10.2.2 and further on google books: https://books.google...eotrope&f=false

and note figure 10.5


Edited by PingPong, 16 November 2015 - 05:02 AM.


#4 jmea

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Posted 18 November 2015 - 06:51 PM

Thanks for your answers guys!! 






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