Conceptual Design of Distillation Columns for Azeotropic Systems Using a Rigorous Method
Elsa Fernández-Martínez,a Ángel Castro-Agüero,a
a Facultad de Ciencias Básicas Ingeniería y Tecnología, Universidad Autónoma de Tlaxcala, Apizaco, Tlaxcala, México, 90300.
Azeotropic mixtures show non idealities, which significantly complicates the separation of components; but also, the knowledge about the thermodynamics of system can help to obtain the design of distillation column. Azeotropic and extractive distillations are essential, because there are numerous processes by which different mixtures are separated by this kind of distillations. A number of important petrochemicals from of hydrocarbons mixtures can be separated by azeotropic and extractive distillations starting the biomass (Van Dongen and Doherty, 1985).
The mixture in study is Ethanol/Water and Ethylene Glycol is added like entrainer. Liquid solution models (Wilson and NRTL) were used to predict the vapor-liquid equilibrium of binary and ternary systems. The parameters of models were obtained from Kamihama, N, et al (2012). The Ethanol/Water mixture has been studied for many researchers and several entrainers have been used by breaking azeotrope. The homogeneous azeotropic distillation is generated with Ethylen Glycol like entrainer, (Kiva, et al, 2003). Julka, et al studied the best election of entrainers using residue curve maps, due to that entrainer determines the separation sequence.
The main purpose of this paper is calculating minimum reflux ratio for a single column, because this structural variable is important for conceptual design. Subsequently the rest of the other variables like feed location, theoretical stages, among others are determined. The proposal design model is based on the generation of a vector space by the vectorial operations and the solution of systems of linear and nonlinear equations that represent the balances of mass and energy, as well as the equilibrium relationship. This approach yields the structural variables of the conceptual design of distillation column for azeotropic mixtures. Mathematical procedure is based on concepts of Ponchon-Savarit method. Doherty and Malone (2001) show a methodology to obtain conceptual design for azeotropic mixtures.
Doherty, M. F. y Malone, M. F. “Conceptual Design of Distillation Systems”, Editorial Mc Graw Hill, primer edición, (2001).
Julka, V., Chiplunkar, M. and O’Young, L., “Selecting Entrainers for Azeotropic Distillation”, AIChE CEP, Reactions and Separations, p. 47, 53, (2009).
Kamihama, N., Matsuda, H., Kurihara, K., Tochigi, K and Oba, S., “Isobaric Vapor-Liquid Equilibria for Ethanol+Water+Ethylene Glycol and Its Constituent Three Binary Systems”, Journal of Chem. and Eng. Data, 57, p.339-344, (2012).
Kiva, V. N., Hilmen, E. K. and Skogestad, S., “Azeotropic phase Equilibrium Diagrams: a Survey”, Chem. Eng. Sci, 58, 1903-1953, (2003).
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