AsTher Thermodynamic Database and Applications

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Examples

1.9.4. Enthalpy-Concentration, Liquid-Gas-Concentration-Diagrams of Ethanol-Water Mixtures
(see also example calculations using AsTher Process Calculator for MS Excel )
This example explains, how you can plot state diagrams (e.g. xy-diagrams as following picture) using the empirical equations of activity coefficients in the application Equilibrium.

There is x mole fraction in liquid- and y mole fraction in in the gas phases.
Step by Step:
1.9.4.1. Elements
Main Menu: System -> Elements. Selection: C,H,O
1.9.4.2. Compounds
In the window for Gas, Select Compounds C2H5OH(g) and H2O(g)
In the window for Liquid, Select Compounds C2H5OH(l) and H2O(l)
1.9.4.3. Activity Coefficients
Main Menu: System -> Activity Coefficients
Select the logarithmic equations of van Laar in drop-down button as shown in the following picture.
Enter coefficients A and B, press Button Add
Equation 1 is the activity coefficients of ethanol and Equation 2 is the activity coefficient of water in binary mixtures of liquids at 50°C corresponding van Laar
(the constants A and B are given by C.A. Jones, A.P. Schoenborn, Ind. Chem. Eng. 40 (1940) 1273-1276).
1.9.4.4. Record Variables
Main Menu: Monitoring -> Record Definition
Select the concentration of the ethanol and water in liquid and gas phase. You can select also other variables to record
1.9.4.5. Graphic Variables
Main Menu: Monitoring -> Graphic Variables
You can determine, which variables are in which coordinates to show in the Graphic Window.
1.9.4.6. Assignment of the Equations for Activity Coefficients to Substances Ethanol and Water
Enter for activity coefficient of ethanol [1] , and for activity coefficient water [2] in the columns a.c. in the phase table corresponding the definition of the equations for activity coefficients in Chapter 1.9.4.3.
1.9.4.7. Calculation
Main Menu: System -> Calculation by Variation
Insert as variables :
Input Liquid 1 C2H5OH (l) from 0 to 1 with steps +0.01
Input Liquid 1 H2O (l) from 1 to 0 with steps -0.01
Start the calculations.
1.9.4.8. The results of the calculations will be shown in Graphic Window
Enthalpy-concentration diagram of ethanol-water-mixtures
xy-Diagram Ethanol-Water Mixtures
Course of the activity coefficients in ethanol-water mixtures corresponding given data in Chapter 1.9.4.3.