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Conceptual analysis of single-feed heterogeneous distillation columns
Análisis conceptual de columnas de destilación heterogénea con un alimento
Keywords:
VLL equilibrium, heterogeneous azeotropic distillation, operation leaves, pinch point curves, conceptual analysis (en)Equilibrio VLL, destilación azeotrópica heterogénea, hojas de operación, curvas pinch, análisis conceptual. (es)
Separation in heterogeneous distillation columns is attained by interaction of two liquid and one vapor phases, interaction of three phases involves complexities due to the determination of vapor-liquid-liquid equilibrium and hence, in the design of separation units. Nevertheless, the liquid-liquid equilibrium allows developing separations that may be unfeasible by vapor-liquid equilibrium. In this way, heterogeneous azeotropic distillation is a useful operation for the separation of azeotropic and close-boiling mixtures. In this work, a new methodology for evaluating the feasibility of this process is developed. This methodology is an extension of that proposed by Castillo et al. (1998) for homogeneous systems. Operation leaves for heterogeneous systems are calculated using the concept of pinch point curves in order to establish the process feasibility. Heterogeneous columns with external decanter are considered as the only heterogeneous stage (OHED: only heterogeneous external decanter). The initialization process for the column calculation requires the selection of the distillate composition using thermodynamic criteria in order to guarantee homogeneous phases within the column. A system with industrial and academic relevance was considered as case study: water-acetic acid-amyl acetate. Results show that the developed shortcut method allows evaluating process feasibility and estimating design parameters, without the use of trial and error procedures implemented, with the aid of simulation tools.
En las columnas de destilación heterogénea la separación se logra por la interacción de dos fases líquidas y una de vapor, la interacción de tres fases genera complejidades especiales en los cálculos de equilibrio vapor-líquido-líquido y de los equipos de separación que se basan en este equilibrio; sin embargo, el equilibrio líquido-líquido permite desarrollar separa-ciones que pueden ser imposibles mediante equilibrio vapor-líquido. En este sentido, la destilación azeotrópica heterogénea es una operación útil para la separación de mezclas azeotrópicas y con puntos de ebullición cercanos. En este trabajo se desarrolla una nueva metodología para evaluar la viabilidad de este proceso de separación; esta metodología es una extensión de la propuesta por Castillo et al. (1998) para sistemas homogéneos. Las hojas de operación se calculan usando el concepto de curvas pinch para establecer la viabilidad del proceso. Las columnas heterogéneas con decantador externo fueron consideradas como la única etapa heterogénea (OHED: only heterogeneous external decanter). Para iniciar el cálculo de las columnas es necesario escoger la composición del destilado con criterios termodinámicos, para garantizar que la fase líquida es homogénea en la columna. Un sistema con relevancia académica e industrial fue considerado como estudio de caso: agua-ácido acético-acetato de amilo. Los resultados muestran que el método corto desarrollado permite determinar la viabilidad del proceso y estimar parámetros de diseño, evitando la implementación de procedimientos de ensayo y error con el auxilio de herramientas de simulación.
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Copyright (c) 2015 Carlos Arturo Martinez Riascos, Libardo Estupiñan Perez
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