| The synthesis and design of distillation processes is a classical chemical engineering problem that has been studied from the beginning of the profession. Despite the attention this problem receives, the most commonly employed methods are “by hand” graphical methods or “trial-and-error” methods through the use of process simulation software. While these methods provide adequate results for small, well-behaved systems, they are often impossible to use, or fail miserably for systems with non-ideal behavior or which contain more than three components. The work in this dissertation aims at providing a theoretical framework upon which the synthesis and design problems can be rigorously solved by computational methods.; Most distillation processes are designed based on equilibrium stages in the distillation tower. In order to properly design a distillation column, a rigorous method for determining the phase equilibrium, and in the case of reactive distillation, the phase and chemical equilibrium state on every tray in the column. The thermodynamic criterion typically used in calculating phase and chemical equilibrium is that of the minimum Gibbs free energy. In this dissertation, equations of state are employed to model both the liquid and vapor phases, and the Gibbs free energy minimization problem is formulated as a global optimization problem.; An essential step of the synthesis problem is the task of locating all of the azeotropes in the system. In this work, the system of nonlinear equations is transformed into a nonlinear optimization problem. This optimization problem may have multiple global minima, and every global minimum that has an objective value of zero corresponds to an azeotrope.; The analysis and algorithms that are developed in this dissertation are implemented in a software package called EQUISTAR. EQUISTAR provides theoretically guaranteed reliable solutions of the phase and chemical equilibrium problem, Gibbs free energy minimization, phase stability, the problem of finding all azeotropes, flash calculations, bubble point calculations, and dew point calculations. In addition, EQUISTAR solves distillation design problems using the method presented in this dissertation, and provides the user a variety of thermodynamic models from which to choose. |
