Locating all heterogeneous and reactive azeotropes in multicomponent mixtures

A novel approach for enclosing all heterogeneous and reactive azeotropes in multicomponent mixtures is presented. The thermodynamic conditions for azeotropy form a system of nonlinear equations. A deterministic global optimization approach is introduced in which the global optimization problem may contain multiple global minima and there is a one-to-one correspondence between each global minimum and a potential azeotrope. An algorithm is presented which provides a theoretical guarantee that all global minima can be enclosed. This method is general and can be applied to multicomponent mixtures that are described by standard thermodynamic models. The problem formulations for finding all heterogeneous azeotropes and for finding all reactive azeotropes are presented. The effectiveness of the proposed approach is illustrated through several example problems using the Wilson, NRTL, UNIQUAC, and UNIFAC activity coefficient equations.