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[jeferson_seibel]

Hello!

 

I'm facing a problem in UniSim: I need to simulate a vegetable oil hydrotreatment process, but the triglycerides are not available in the basic databank attached to my university's software license. So, I went over the works on literature and found the Zhong method for triglyceride property estimation, which is frequently used in simulations done in Aspen Plus as a custom model. For consulting more about this property estimation method, please, see the links below:

 

Original article: https://pubs.acs.org...1021/ie900513k#

Article correction: https://pubs.acs.org....1021/ie100160v

 

The methods proposed by the author allow one to calculate properties such as molar volume, vapour pressure, viscosity and heat capacity by considering fragment contribuitions. Then, it would be possible, for every equation of the models, to calculate the constants by adding up the fragment contributions. Once the constants were calculated for a given component (ex.: triplamitin), one could put these in a property model equation and calculate its values over a given temperature range.

 

I've done this work within MS Excel for tripalmitin, which gave me accurate results - comparing the values reported by the Zhong's work. Nevertheless, I didn't get the same results when I put the model and constants in UniSim. I defined tripalmitin in UniSim as a hypothetical component, defining some component data such as boiling point, critical properties and so on (I got this informations from a NIST databank available through Aspen Plus). I also defined the UNIFAC structure of the component in order to compute de unknown properties. Last, but more important, I defined the T-dependent properties, namely vapour pressure, liquid density, liquid viscosity and liquid heat capacity. As I had some trouble adding images to this topic, I prepared a Word documeny available in the Google Drive link below:

 

Problem description: https://docs.google....of=true&sd=true

 

I'd like to know if somebody else has ever faced some trouble of this nature in UniSim, and if there is a manner of resolving it. Maybe I'm doing something wrong in the process of defining the component inside UniSim, I don't know. Maybe you can share a tutorial or point some way for solving this.

 

Thank you in advance!

Edited by jeferson_seibel, 17 April 2022 - 11:15 AM.