2024.9.04
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2.3 Actual ASOG method calculation
2.3.1 Verification of 1979 examples.
The book ‘Vapor-Liquid Equilibrium Estimation by the ASOG method’, published by Kodansha in 1979, contains an example problem for a 115-series system. Let’s try an actual calculation using that example.
2.3.2 heterogeneous system
In systems with a large deviation from the ideal solution, e.g. n-butanol-water and methyl ethyl ketone-water systems, the liquids do not mix with each other. The liquid phase is then divided into two phases, resulting in a vapour-liquid equilibrium.
2.3.3 gas-phase association system
Low-molecular-weight carboxylic acids are known to evaporate in dimers.
We now move on to an example from the book ‘Estimating Chemical Engineering Properties with ASOG and UNIFAC BASIC’, published by Chemical Industry in 1986: the group interaction parameter akl in the 1979 book and the parameter in 1986 are identical. The parameters are therefore evaluated using MN 1979.
2.3.4 Evaluation of the azeotrope by the ASOG method.
In the book, the azeotropes of alcohols and hydrocarbon compounds determined by the ASOG method are compared with the measured azeotropes. The real solvent pairs are very limited, as many of the same solvent pairs are described with constant pressure but different pressures, constant temperature but different temperatures, etc.
2.3.5 Assessment of liquid-liquid equilibrium using the ASOG method
The 1986 book uses the same akl as the 1979 book but with various extensions. Various ASOG families have been developed, including high-pressure gas-liquid equilibrium, liquid-liquid equilibrium and solid-liquid equilibrium, and their programmes are described. ASOG for vapour-phase association systems is also a separate programme. For some families, a separate parameter has been developed from the groove-to-groove interaction parameter akl for low-pressure vapour-liquid equilibrium.
2.3.6 Assessment of liquid-phase association using the ASOG method.
The fact that low-molecular-weight carboxylic acids also associate in the gas phase by forming some dimers was explained in 1.7 Handling of the association system. In that case, of course, association also occurs in the liquid phase. Low-molecular-weight carboxylic acids dimerise in the same molecule, but this is rather rare.
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