2 replies to this topic

[kacha130]

i have a problem to estimate K value i work to optimize a column of distilattion in higt pressure 11 bar 
i used antoine but it's not the in the range of pressure 
wilson it is not fiable 
my componds :Nitrogen
CO2 CO Methane Ethane Propane i-Butane n-butane i-pentane n-pentane 2-Mpentane n-hexane n-heptane n-octane n-Nonane H2O H2S TEGlycol Benzene Toluene E-Benzenem-Xylene O-Xylene n-Decane

i will attached my calculate sheet 

plz if someone can help me

Attached Files

•  Column .xlsx   36.36KB   20 downloads

[shantanuk100]

Hi Kacha,

I assume you are trying to calculate the K-value using different VLE approaches.
There are certain restrictions on these methods.

1. If you are calculating the K-value by ratios of Saturation Vapor pressure P-Vap to system pressure P, please note that this correlation is obtained by equating Raoult's law and Dalton's law.
But Raoult's law is applicable only for low pressure systems which are under 3.5 Bara. But your system being at 11 bara makes this inapplicable. That is the reason that the antoine approach is failing, not the equation itself. This approach also does not consider the fact that the K values are composition dependent, which might make the answer vary a little but is still valid.

2. An alternative approach then, would be to use the Wilson correlation which has been obtained from curve regressed data.This equation too considers independency of K upon composition, but the equation by itself is accurate and valid for low to moderate pressure systems, which are below 35 bara. So the wilson equation should be applicable to your case. Do check that out once.

3. There are more alternative approaches such as using the Equation of state methods, and fugacity coefficient methods. If you are unable to get the result using the wilson correlation, then check out these other approaches. You can find their respective equations over here :-http://www.jmcampbel...rmine-k-values/

4. Since yours is a specific high pressure case, personally I would suggest using a process simulator for the above exercise than calculating it manually yourself, unless it is for understanding the concept, because there are numerous restrictions on the applicability of each method such as on temperature ranges, pressure ranges, compositonal dependencies, precursors etc. that one single person might not be entirely aware of on their own.

Regards,
Shantanu Kallakuri

Edited by shantanuk100, 23 March 2016 - 05:37 AM.

[kacha130]

thanks shantanuk , it s pleasure