Multicomponent three-phase azeotropic distillation. 2. Phase-stability and phase-splitting algorithms

Abstract

A literature review of three-phase distillation calculation procedures highlights the large number of efforts that have been made to account for the appearance of a second liquid phase on a distillation tray. The numerical problems due to the introduction of a second liquid phase during an iteration scheme are summarized in a table containing the known 15 solution sets. Many of these solutions contain a liquid-phase-splitting algorithm. A new algorithm based on Michelsen's phase-stability test and phase-splitting algorithm has been developed. New procedures in the iteration method and to identify liquid-phase instability have been produced and verified. These new procedures use analytical partial derivatives which can be determined from modern thermodynamic models to describe nonideal liquid-phase behavior. The predicted separation performance of a three-phase azeotropic distillation column using this new algorithm is in good agreement with the experimental data collected in part 1 of this series.

Conceptual Design of Azeotropic Distillation Processes

“…Global and local phase stability tests have been reviewed by Cairns et al [65] and Zhang et al [66]. While only global methods assure a correct solution, especially the combination of local methods, like the negative flash [67], and continuation methods [68,69] or rate-based methods [70], allow for computationally efficient solutions with high reliability.…”

Modelling of a dynamic multiphase flash: the positive flash

“…Yet, as the number of phase is not known in advance, it is tricky to select the phase number relevant set of equations that is to be solved and numerical problem difficulties may occur due to non-smooth problems or pseudo solutions Morbidelli, 1981, 1982 ;Bullard and Biegler, 1993). To overcome this difficulty, equationsolving method usually involve two sequential or imbricated loops : first the determination of the number and type of coexisting phases relying on a stability test like the tangent plane criterion (Baker et al, 1981, Michelsen, 1982a, 1982b, Cairn and Fürzer, 1990a, 1990b, Gupta et al, 1991, Widagdo et al, 1992, Sun and Seider, 1995Jalali and Seader, 2000) and second, the calculation of phases composition and ratio solving the correct set of governing equations. For more than two coexisting phases like liquid-liquid-vapor equilibria, these two loops may be repeated several times until the correct phase configuration is found.…”

Representación de los Equilibrios Líquidos Multifásicos de Sistemas Cuaternarios con los Modelos NRTL y UNIQUAC

“…En la industria química, la tecnología de la extracción por solventes depende en gran medida de la miscibilidad limitada y la distribución de un soluto entre dos fases líquidas. Por ejemplo, en destilación azeotrópica, la separación del componente de arrastre de los productos obtenidos después del condensador se facilita debido a la formación de dos fases líquidas (Cairns y Furzer, 1990). En el diseño del equipo para tales procesos y la simulación de los procesos químicos a escala industrial, es necesario conocer, ya sea de datos experimentales o a través de cálculos, la composición de los componentes de cada fase en equilibrio.…”