2 replies to this topic

[polipo]

Dear all,

I want to know the equilibrium of the following mixture (component in oil phase and water phase):

Methanol 100 kg/hr
Triolein (C₅₇H₁₀₄O₆) 1000 kg/hr
NaOH 50 kg/hr
H₂O 50 kg/hr

So, I used the decanter for which the above is the component in feed at 25 ^oC and 1 bar, and there are 2 liquid phases (oil and water). The decanter is at the same condition as feed (25 ^oC and 1 bar) because I want to know the equilibrium at that pressure and temperature. The method is UNIQUAC. The key component of 2nd liquid phase is water. However, ASPEN notified that "Calculation stops because property parameter missing"

and when the control panel reported, it showed:

PROPERTY PARAMETER ERROR
ACTIVITY COEFFICIENT MODEL GMUFAC HAS MISSING PARAMETERS:
UNIFAC GROUP STRUCTURAL INFORMATION PARAMETER, UFGRP (DATA SET 1),
MISSING FOR COMPONENT NAOH; NO UFGRP PARAMETERS SUPPLIED BY USER;
DEFAULTS NOT FOUND IN DATA BANK

Anyone could help me about this. I want to be pointed out if I did something wrong and what I should do.

Best regards and Thanks

[MrShorty]

I don't know my way around Aspen specifically, but the error message suggests that you've asked it to use UNIFAC rather than UNIQUAC and, not surprisingly, UNIFAC doesn't have any information in it to tell the model how to handle an electrolyte like NaOH.

I don't know exactly how to do this in Aspen, but it looks to me like you need to research and use a different thermodynamic model that will handle electrolyte's.

Edited by MrShorty, 30 April 2012 - 08:41 AM.

[distillationman]

When using UNIQUAC for a mixture like that see that this package does not contain the binary parameters for the acrolein and NaOH pairs. The best way to model a case like that is to get data from a liquid-liquid equilibrium experiment and next work with components efficiency in aspen in order to get a good model. Regarding thermodynamics models the three ones that could deal with L_L calculations are NRTL, UNIQUAC and UNIFAC and its variants.
Another point: verify if all databases are being considered (components painel).