LOCATING ALL AZEOTROPES IN HOMOGENEOUS AZEOTROPIC SYSTEMS

A global optimization based approach for finding all homogeneous azeot ropes in multicomponent mixtures is presented. The global optimization approach is based on a branch and bound framework in which upper and lower bounds on the solution are refined by successively partitioning the target region into small disjoint rectangles. The objective of suc h an approach is to locate all global minima since each global minimum corresponds to an homogeneous azeotrope. The global optimization prob lem is formulated from the thermodynamic criteria for azeotropy, which involve highly nonlinear and nonconvex expressions. The success of th is approach depends upon constructing valid convex lower bounds for ea ch nonconvex function in the constraints. The convex lower bounding pr ocedure is demonstrated with the Wilson activity coefficient equation. The global optimization approach is illustrated in an example problem .