Jump to content



Featured Articles

Check out the latest featured articles.

File Library

Check out the latest downloads available in the File Library.

New Article

Product Viscosity vs. Shear

Featured File

Vertical Tank Selection

New Blog Entry

Low Flow in Pipes- posted in Ankur's blog

Boiling Point Elevation In Aspen Plus

bpe boiling point aspen plus boiling point elevation simulation aspen sugar solution question

This topic has been archived. This means that you cannot reply to this topic.
4 replies to this topic
Share this topic:
| More

#1 Kylan

Kylan

    Brand New Member

  • Members
  • 2 posts

Posted 02 September 2015 - 09:14 AM

What is the easiest way to add boiling point elevation into Aspen Plus simulations?

 

In the sugar industry, correlations have been made to determine the boiling point elevation of impure sucrose solutions.

How can I put in a calculation to determine the boiling point of a mixture based on a stream's composition and then tell Aspen that this must be the boiling point of that stream?



#2 shan

shan

    Gold Member

  • ChE Plus Subscriber
  • 692 posts

Posted 02 September 2015 - 09:47 AM

You may define a hypothetical component with the boiling curve.



#3 MrShorty

MrShorty

    Gold Member

  • ChE Plus Subscriber
  • 517 posts

Posted 02 September 2015 - 03:35 PM

If you convert your boiling point curves into activity coefficients for water, you can make use of Aspen's built in activity coefficient models. I do not know how high your concentration is expected to be, but the Chem 105 level problems would usually be well modeled even using Raoult's law. Even at moderate sucrose concentrations, I would expect our usual activity coefficient equations to handle the boiling point elevation reasonably well.


Edited by MrShorty, 02 September 2015 - 05:31 PM.


#4 Kylan

Kylan

    Brand New Member

  • Members
  • 2 posts

Posted 03 September 2015 - 05:20 AM

If you convert your boiling point curves into activity coefficients for water, you can make use of Aspen's built in activity coefficient models

 

Thanks for the great suggestion, can you point me in the right direction as to how to convert boiling point curves into activity coefficients?

 

You may define a hypothetical component with the boiling curve.

 

Thanks for your reply. I need to keep the original individual components to account for evaporation of water, inversion of sucrose and crystallisation. 



#5 MrShorty

MrShorty

    Gold Member

  • ChE Plus Subscriber
  • 517 posts

Posted 03 September 2015 - 09:53 AM

Obviously I cannot recreate an entire college level textbook here, so I will have to assume that you have seen some of this before.

 

As a first guess, I might suggest that you see if Raoult's law is adequate for your purposes:

 

P(tot)=total pressure

P(H2O)=Partial pressure of water

x(H2O)=mole fraction water in the liquid phase

P0(H2O)=vapor pressure of pure water at T.

P(tot)=P(H2O)=x(H2O)*P0(H2O)

Note that we are assuming that the sugar is completely non-volatile, which should be a good assumption at low temperatures, but may be a poor assumption if the temperature gets high enough. Also note that concentration is in mole fraction, so you may need to convert whatever your concentration units are to mole fraction. At this point, I will assume that you have seen this sort of thing before and know how to solve this equation for "boiling point temperature".

 

As a second guess, I might suggest a simple "modified Raoult's law", where we assume the vapor phase is ideal and we can model the non-idealities in the liquid with a simple activity coefficient:

 

gamma(H2O)=activity coefficient of water

P(tot)=P(H2O)=x(H2O)*gamma(H2O)*P0(H2O).

 

I don't know how Aspen will prefer to have this done. It is certainly possible to solve this equation for gamma(H2O), then fit those activity coefficients to your desire activity coefficient equation. Some algorithms will take the P, T, and x data and a chosen activity coefficient model and regress on boiling point directly using the parameters of the activity coefficient model.






Similar Topics