GlobSol Case Study in Chemical Engineering: Reliable Computation of Homogeneous Azeotropes

The determination of the existence and composition of homogeneous azeotropes is important both from both theoretical and practical standpoints in the analysis of phase behavior and in the synthesis and design of separation systems. We present here a new method for reliably locating any and all homogeneous azeotropes for multicomponent mixtures. The method also veriies the nonexistence of homogeneous azeotropes if none are present. The method is based on interval analysis, in particular an interval New-ton/generalized bisection algorithm that provides a mathematical and computational guarantee that all azeotropes are located. The technique is general purpose and can be applied in connection with any thermodynamic models. We illustrate the technique here in several example problems using the Wilson, NRTL, and UNIQUAC activity coeecient models.