Page 369 - Chemical engineering design

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CHEMICAL ENGINEERING
appropriate Wilson coefficients (Wilson A values) in the other data statements. The
program can easily be modified for use as a sub-routine for bubble-point and other vapour
composition programs.
The use of a spreadsheet to solve the Wilson equation is illustrated in Example 8.15b.
The spreadsheet used was Microsoft Excel. Copies of the spreadsheet example can be
downloaded from support material for this chapter given on the publisher’s web site at:
bh.com/companions/075641428.
Example 8.15a
Using the Wilson equation, calculate the activity coefficients for isopropyl alcohol (IPA)
and water in a mixture of IPA, methanol, water, and ethanol; composition, all mol fraction:
Methanol Ethanol IPA Water
0.05 0.05 0.18 0.72

Solution
Use the binary Wilson A values given by Hirata (1975). The program “WILSON”,
Table 8.9, is used to solve this example.
The Wilson A-values for the binary pairs are A i,j
j

1 2 3 4
 
1 1 2.3357 2.7385 0.4180
2  0.1924 1 1.6500 0.1108 
i  
3  0.2419 0.5343 1 0.0465 
4 0.9699 0.9560 0.7795 1

Component 1 D MeOH
2 D EtOH
3 D IPA
4 D H 2 O

The output from the program for the concentrations given was:
3 D 2.11, 4 D 1.25

Experimental values from Hirata (1975)

3 D 2.1, 4 D 1.3

Example 8.15b
Using the compositions and Wilson coefficients given in Example 8.15a, determine the
activity coefficient for methanol.