3 replies to this topic

[shahidulislam48]

Hi,

 

When I try to simulate N2 and H2O to find their critical properties, I mix these 2 streams, mixing stream critical properties just shows me the Pseudo Tc and Pc not any true value. What is really wrong with this?

 

I have used Peng-Robinson as a fluid package for simulation.

 

Is there any different approach of finding True Critical properties for mixing components?

 

Thanks in advance

 

Shahidul

[latexman]

The pseudocritical constants are simply empirical parameters that have been found useful for correlating the physical properties of a mixture.  Unlike T_c and P_c for a single component, T'_c and P'_c have no physical significance.

 

Footnote 11 on page 211 of Elementary Principals of Chemical Processes by Felder and Rousseau.

[serra]

possibly you mean VL critical point(s),

many simulators allow to calculate these critical point(s) as part of phase envelope (diagram) procedure,

the process library which I use (Prode Properties) exports specific methods =StrPC()  =StrTc() etc. as Excel macros,

but I presume you can obtain equivalent values from Aspen (may be you have to set some dialog),

take care that PR model may show quite large errors for N2-H2O mixture,

you may consider different models.

[shahidulislam48]

Thanks Serra for your suggestion.