Example 05.09 Compare experimental VLE to Wilson Equation Results

problem:

Compare the experimental vapor phase mole fractions published by Hiaki et al. for the system acetone (1) - chloroform (2) - methanol (3) at 1 atm with the calculated ones using the binary Wilson parameters l_ij listed in assuming ideal vapor phase behavior.

The calculation should be performed for the following composition at T=331.42 K:

x₁ = 0.229, x₂ = 0.175, x₃ = 0.596, y₁ = 0.250, y₂ = 0.211, y₃ = 0.539.

general

constants

and

definitions:

input data

Experimental data:

Antoine constants of the components:

Antoine function for vapor pressure calculation:

Liquid molar volumes of the components:

Interaction parameter matrix:

Solution

Calculation of the interaction parameters Dl as function of temperature:

Calculation of the interaction parameters DL as function of temperature:

Calculation of the activity coefficient as function of temperature and composition can be performed using the expression given in Table 5.6:

Calculation of partial pressures, total pressure and vapor mole fractions::

The results can now be compared to the experimental data given by Hiaki et al.. The measurements were performed at 1 atm, which is 3.2% lower than the calculated value.

The experimental vapor phase compositions of the first two components differ strongly (by about 4 mol%) from the experimental findings:

This also results in serious discrepances between the experimental and calculated separation factors:

Although the vapor phase concentration was nearly correct, all separation factors are very unrealistic. Either the model parameters or the experimental results are therefor not acceptable.