THE DATA REGRESSION SYSTEM - Teach Yourself the Basics of Aspen Plus - page 86

Unifac, and Unifac-LL. Note the similarity between Uniquac and Unifac. Note the
difference in application between Unifac and Unifac-LL.

Workshop 6.1 Use Property Analysis to estimate the mutual solubility of a
toluene - water system at temperatures varying from 32 to 86 ◦ F at 14.696 psi. Select
the property option Unifac-LL. The mutual solubility of the toluene - water system
at 86 ◦ F and 14.696 psi is 0.999894 and 0.000237 mole fraction water in each phase,
respectively. Use engineering (ENG) units. Compare to the results estimated.

Workshop 6.2a Fit the following single data point of mutual solubility for a
toluene - water system to the two-parameter form of the van Laar equation. Use the
parameters a i,j and a j,i. .At25 ◦ C and 14.696 psi the solubility of water expressed as
mole fractions in each phase is 0.999894 and 0.000237, respectively.

Workshop 6.2b Fit the toluene - water solubility data from the LLE Dechema data
collection in Table 6.5 to the van Laar equation using the a i,j and a j,i parameters.
All solubility data are at 14.696 psi and expressed in mole fractions of toluene. Use
engineering units.
What are your observations?

TABLE 6.5 Toluene-Water Mutual Solubility Data
Temperature Mole Fraction Mole Fraction

( ◦ C)

x I x II

0 0.000142 0.99891

10 0.000128 0.99844

20 0.000113 0.99784

25 0.000106 0.99763

Workshop 6.2c Repeat Workshop 6.2b using b i,j and b j,i parameters with the van
Laar equation. What are your observations?

Workshop 6.3a Repeat Workshop 6.2b using b i,j and b j,i parameters with the Uni-
quac equation. What are your observations?

Workshop 6.3b Using the data of Washburn et al. (1939) for the water - ethanol -
toluene system in Table 6.6, fit the data to the Uniquac equation with the b i,j parameters
determined from the single mutual solubility data point of Workshop 6.3a held constant.
Va r y t h e b i,j parameters for the remaining binary pairs.

Workshop 6.3c Repeat Workshop 6.3b varying all six b i,j parameters? Compare
the results to those of Workshop 6.3b. Which result should be used?

Workshop 6.4a Fit the data of Suska et al. (1970) given in Table 6.7 to the van
Laar, Wilson, NRTL, and Uniquac equations. Use the a ij parameters for all equations.
Additionally, use the c ij parameter when fitting the NRTL equation. Select and fix the
appropriate value of the c I,j parameter. Compare the four results.