UNIQUAC

Ethanol is currently one of the most important and attractive sources of energy with a heating value of 12800 kJ/kg. Ethanol is commonly obtained from many sources worldwide, mainly renewable sources, and its separation is achieved typically by atmospheric distillation. Even so, there is new technologies looking for cheaper and more efficient ethanol separation and purification: pressure-swing distillation, extractive distillation, adsorption with molecular sieves and vacuum membrane distillation. The design, rating and optimization of these process technologies requires a reliable and universal thermodynamic modeling approach capable of represents the ethanol-water system properties, and in particular the vapor-liquid equilibrium (VLE) near the azeotropic point. This study summarize VLE experimental data for ethanol-water system at 3 vacuum pressures (13.15, 19.71 and 101.32 kPa), and 17 azeotropic point data. Thermodynamic consistency test of the data was performed using the Redli...

Ethanol is currently one of the most important and attractive sources of energy with a heating value of 12800 kJ/kg. Ethanol is commonly obtained from many sources worldwide, mainly renewable sources, and its separation is achieved typically by atmospheric distillation. Even so, there is new technologies looking for cheaper and more efficient ethanol separation and purification: pressure-swing distillation, extractive distillation, adsorption with molecular sieves and vacuum membrane distillation. The design, rating and optimization of these process technologies requires a reliable and universal thermodynamic modeling approach capable of represents the ethanol-water system properties, and in particular the vapor-liquid equilibrium (VLE) near the azeotropic point. This study summarize VLE experimental data for ethanol-water system at 3 vacuum pressures (13.15, 19.71 and 101.32 kPa), and 17 azeotropic point data. Thermodynamic consistency test of the data was performed using the Redlich-Kister method. The parameters and constants for the detailed thermodynamic modeling of the ethanol-water system using polar fluid Soave-Redlich-Kwong equation of state (polar-SRK) are summarized as part of this study, as well as the standard binary interaction parameters for NRTL and UNIQUAC excess Gibbs energy models. Both models are used simultaneously for the simulations involved in the chemical process engineering activities in science, academy and industry. The main target of this study consist in the regression of new binary interaction parameters in a temperature dependent form compatible with the most process simulation software, for NRTL and UNIQUAC, and its validation using experimental data for azeotropic points at 3 different low pressures with errors of less than 1%, for temperature and ethanol molar fraction in the vapor phase. The regressed new parameters were tested using isobaric experimental data for VLE at the 3 under-atmospheric pressures mentioned, obtaining correlation coefficient (R 2) values of about 1. The calculations were performed using Python 3.4® codes developed and supplied by S&S and Aspen properties® V8.6 provided by the Universidad Nacional de Colombia. Resumen El etanol es actualmente una de las fuentes de energía más importantes y atractivas, posee un poder calorífico de 12800 kJ / kg. El etanol se obtiene comúnmente de diversas fuentes en todo el mundo, principalmente fuentes renovables, y su separación se logra comúnmente mediante destilación atmosférica. Aun así, existen nuevas tecnologías que buscan una separación y purificación de etanol más económica y eficiente, tales como: destilación de presión y destilación, destilación extractiva, adsorción con tamices moleculares y destilación por membrana de vacío. El diseño, evaluación y optimización de estas tecnologías de proceso requiere de un enfoque de modelado termodinámico confiable y universal capaz de representar las propiedades del sistema etanol-agua, y en particular el equilibrio vapor-líquido (ELV) cerca del punto azeotrópico. 18 Este estudio resume los datos experimentales de ELV para el sistema etanol-agua a 3 presiones de vacío (13.15, 19.71 y 101.32 kPa), y 17 datos de puntos azeotrópicos. La prueba de consistencia termodinámica de los datos se realizó utilizando el método de Redlich-Kister. Los parámetros y constantes para el modelado termodinámico detallado del sistema etanol-agua usando la ecuación de estado para fluidos polares Soave-Redlich-Kwong (polar-SRK) se resumen como parte de este estudio, así como los parámetros de interacción binarios estándar para NRTL y UNIQUAC exceso de modelos de energía Gibbs. Ambos modelos se utilizan simultáneamente para las simulaciones involucradas en las actividades de ingeniería de procesos químicos en la ciencia, la academia y la industria. El objetivo principal de este estudio consiste en la regresión de nuevos parámetros de interacción binaria en una forma dependiente de la temperatura que es compatible con la mayoría del software de simulación de procesos en la industria y el mercado, para NRTL y UNIQUAC, y su validación utilizando datos experimentales para puntos azeotrópicos a 3 diferentes bajas presiones, esta validación permitió verificar que el modelo empleado tiene errores de menos del 1%, para la temperatura y la fracción molar de etanol en la fase de vapor. Los nuevos parámetros regresados se probaron usando datos experimentales isobáricos para VLE a las 3 presiones atmosféricas mencionadas, obteniendo valores de coeficiente de correlación (R2) de aproximadamente 1. Los cálculos se realizaron usando códigos Python 3.4® desarrollados y suministrados por S&SE S.A.Sy Aspen properties® V8.6 proporcionado por la Universidad Nacional de Colombia.

ABSTRACT Isothermal vapor–liquid–liquid equilibrium data were measured for the ethanol + water + diethyl carbonate (DEC) ternary system and the constituent binaries using static headspace gas chromatography (HSGC) at 353.15 and 363.15 K. Multiple headspace extraction was used to calibrate the gas chromatograph. The activity coefficients were calculated using the Gibbs–Duhem equation and thermodynamic correlations. The thermodynamic consistency of the experimental vapor–liquid and vapor–liquid–liquid equilibrium data was verified. The experimental data were correlated using NRTL and UNIQUAC models, obtaining new UNIQUAC and NRTL interaction parameters for the VLE and VLLE.

ABSTRACT Experimental (liquid+liquid) equilibrium data for the mixtures of (heptane, or hexane, or cyclohexane+toluene+1,3-dimethyl-2-imidazolidinone) were determined at T=298.15K and P=101.3kPa. The solubility (binodal) curves and tie-line end compositions are reported for the related mixtures and presented as complete phase diagrams. Distribution coefficients and separation factors were evaluated for the immiscibility region. The reliability of the experimental tie-line results was verified by using the Othmer–Tobias correlation. The experimental tie-line data were correlated by UNIQUAC model, which gave satisfactory representation for the systems. It was observed that the separation of toluene from cyclohexane is easier to achieve than from heptane and hexane.