UNIQUAC

UNIQUAC ( Universal Quasi Chemical Abbreviation for English ) is an activity coefficient model, the activity coefficient γ of the components in a chemical mixture with the compositions, expressed as mole fractions, correlated.

Equations

In UNIQUAC activity coefficient of component i is composed of two components, the remaining portion, the intermolecular forces describes, and the combinatorial content, the size and shape of the components taken into account:

Combinatorial share

The combinatorial component is calculated exclusively from material-specific variables, the relative van der Waals volumes and surface areas of the pure substances.

With the volume fraction per mole fraction of component i

And the surface fraction per mole fraction of component i

Residual fraction

The remainder fraction containing the other hand, the interaction parameter that can be adapted to and sometimes even experimentally estimated activity coefficient.

With

These are the adjustable parameters of interaction between the components i and j.

Use

Activity coefficients allow simple relations phase equilibria ( gas-liquid, liquid-liquid, solid-liquid) to calculate and some other thermodynamic quantities. Models such as UNIQUAC now make it possible, for example in the simulation process complex calculations for arbitrary compositions of a chemical mixture carried out with only a few known parameters, without having to know experimental data for all required points.

Parameter

UNIQUAC knows two fundamentally different parameters.

Recent Developments

UNIQUAC will be further developed in many working groups. Some selected derivatives are

  • UNIFAC: A method which allows both the volumes and surfaces as well as in particular the interaction contributions to estimate. This eliminates the use of experimental data to adjust the UNIQUAC parameters.
  • Extensions for the calculation of the activity coefficient in the electrolyte mixtures containing
  • Extensions for better description of the temperature dependence of the activity coefficients
  • Extensions for polymer systems
Process simulation Digital Object Identifier
792559
de