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Aspen Physical Property System - Physical Property Models

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Other values Hansen volume calculated by <strong>Aspen</strong> Plus<br />

Reference<br />

Frank, T. C.; Downey, J. R.; Gupta, S. K. "Quickly Screen Solvents for<br />

Organic Solids," Chemical Engineering Progress 1999, December, 41.<br />

Hansen, C. M. Hansen Solubility Parameters: A User’s Handbook; CRC Press,<br />

2000.<br />

Ideal Liquid<br />

This model is used in Raoult's law. It represents ideality of the liquid phase.<br />

This model can be used for mixtures of hydrocarbons of similar carbon<br />

number. It can be used as a reference to compare the results of other activity<br />

coefficient models.<br />

The equation is:<br />

ln �i = 0<br />

NRTL (Non-Random Two-Liquid)<br />

The NRTL model calculates liquid activity coefficients for the following<br />

property methods: NRTL, NRTL-2, NRTL-HOC, NRTL-NTH, and NRTL-RK. It is<br />

recommended for highly non-ideal chemical systems, and can be used for VLE<br />

and LLE applications. The model can also be used in the advanced equationof-state<br />

mixing rules, such as Wong-Sandler and MHV2.<br />

The equation for the NRTL model is:<br />

Where:<br />

Gij<br />

�ij<br />

�ij<br />

114 2 Thermodynamic <strong>Property</strong> <strong>Models</strong><br />

=<br />

=<br />

=<br />

�ii = 0<br />

Gii = 1<br />

for Tlower � T � Tupper<br />

aij, bij, eij, and fij are unsymmetrical. That is, aij may not be equal to aji, etc.

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