Resume of the extension of the Ponchon and Savarit method for designing ternary rectification columns

This work presents a summary of the analytical extension of the classical Ponchon and Savarit method for the design of binary distillation columns to ternary systems. For a given feasible separation, convergence is almost always guaranteed in calculation times comparable to those used by commercial simulation packages. However, in this case the total number of stages and the optimal feed location are simultaneously determined. For ternary mixtures it is possible graphical representation keeping all the intuitive characteristics of the original method for binary mixtures. The presented approach include the possibility of approximate (with interpolation, correlation and intersection methods) or rigorous calculations of mass and energy balances and equilibrium relations and the direct calculation of the minimum number of equilibrium stages and the optimum feed point location for a specific product separation with a specified reflux ratio. The distillate flow rate and the reflux ratio can be optimised in an outer loop providing the method a great flexibility.University of Alicante and Institute of Culture Juan Gil Alber

Reacciones de oxidación y reducción (Redox): ecuaciones, diagramas y relaciones con otros equilibrios

Sistemas redox. Aplicación de la ecuación de Nernst a distintos tipos de sistemas. Factores que modifican el potencial redox. Reacciones de transferencia electrónica. Constante de equilibrio y potencial de equilibrio. Representaciones gráficas: Diagrama log C-E y sus aplicaciones al estudio de las reacciones redox. Sistemas redox del agua. Análisis de sistemas-combinación de diagramas.Universidad de Alicant

Aprendizaje de conceptos complejos en Oceanografía a través del diseño de aplicaciones en Matlab: Una estrategia para motivar al alumnado e introducirlo en la programación

Este trabajo pretende resolver un problema detectado en el alumnado de la asignatura Oceanografía Física del Grado en Ciencias del Mar. Dicho problema está relacionado con la dificultad del alumnado actual para sentirse motivado ante el aprendizaje de conceptos complejos en Física, Química y Matemáticas así como adquirir las competencias y capacidades asociadas a dicho concepto. Se ha escogido un concepto complejo: la obtención del flujo geostrófico en el océano. El trabajo presenta un cuestionario inicial de evaluación previa tras la explicación del concepto en una clase magistral, el posterior desarrollo de una sesión de aprendizaje utilizando simulaciones virtuales y programación en Matlab así como un cuestionario final para evaluar el grado de satisfacción así como de adquisición de conocimientos y competencias tras realizar la actividad para así poder extraer conclusiones de su actividad. Aunque los cuestionarios y la sesión no se podrán aplicar hasta el curso académico 2016-17, esperamos que mejore significativamente el aprendizaje en clase, cree un ambiente favorable entre el alumnado para utilizar las nuevas tecnologías y la programación y pueda aplicarse posteriormente a otros conceptos de esta u otras asignaturas.Universidad de Alicant

Analysis of the Zone Connecting Consecutive Sectors in Generalized Distillation Columns by Using the Ponchon-Savarit Method

Ponchon-Savarit is a classical graphical method for the design of binary distillation columns. This method is still widely used, mainly with didactical purposes, though it is also valid for preliminary calculations. Nevertheless, no complete description has been found in books and situations such as different thermal feed conditions, multiple feeds, possibilities to extract by-products or to add or remove heat, are not always considered. In this work we provide, a systematic analysis of the Ponchon-Savarit method by developing generalized equations for the operating lines or difference points, as well as a consistent analysis of what may happen in the zone between two consecutive trays of the corresponding sectors separated by a lateral stream of feed, product, or a heat removal or addition. The graphical interpretation of all situations shown allows a clarifying view of the different possibilities in the rectifying column and completes the existing literature about this method

Mapping Binary Liquid-Vapor or Liquid-Liquid-Vapor Equilibria Regions, including the Different Azeotropic Behaviours, as a Function of the NRTL Binary Parameters

13th Mediterranean Congress of Chemical Engineering (Sociedad Española de Química Industrial e Ingeniería Química, Fira Barcelona, Expoquimia), Barcelona, September 30-October 3, 2014As it is very well know, the synthesis and design of separation processes requires the use of models to represent the phase equilibrium data, which involves the previous correlation of experimental data to obtain the values of the corresponding parameters. In previous works, we have studied the capabilities and limitations of the classical GE models used in phase equilibrium data correlations, such as NRTL model, in representing the behaviour of different LV, LL and LLS equilibrium data. In the preset work, the relations between the binary parameters Aij of the NRTL model and the existence of different equilibrium regions (i.e.: LV, LL or LLV), as well as the different possible azeotropic behaviours are analyzed for different component systems. The Gibbs free enthalpy curve and the corresponding y-x and T-x,y diagrams along a matrix of Aij parameters has been studied within a range including the typical values observed in DECHEMA Chemistry Data Series

Robust program for LLSE data correlation of ternary systems

The existing commercial software packages (like Dechema Data Preparation Package (DPP) and the regression utilities of Chemical Engineering simulators like Chemcad) have been widely used and their extensive capabilities are well-known. Nevertheless, and as long as LLE calculations is concerned, they have been designed for the simplest equilibrium behaviour. For example, for ternary systems it is only possible the correlation of type 1 and type 2 LLE data. None of these applications allows for the correlation of type 0 LLE, type 3 LLLE or type 4 LLSE systems. To enable a possible extension of such software, a robust calculation algorithm to compute phase equilibria among condensed phases for all these more complicated behaviours has been developed.Vicepresidency of Research (University of Alicante) and Generalitat Valenciana (GV/2007/125)

Simultaneous VLLE data correlation for ternary systems: Modification of the NRTL equation for improved calculations

Simultaneous correlation of vapour–liquid–liquid equilibrium (VLLE) data is hardly ever attempted in literature with one common set of parameters for all the equilibrium regions present in the systems. It is common practice to obtain different sets of parameters for VLE, LLE and VLLE regions when experimental equilibrium data for ternary systems are fitted with a given model (e.g. an activity coefficient model for the liquid phase). Besides, when dealing with the correlation of VLE for ternary systems, it is quite frequent to obtain different sets of parameters for each one of the three binary subsystems from those obtained when exclusively binary VLE data are correlated. In the present work, the simultaneous correlation of all the equilibrium regions in the ternary VLL system is attempted. The objective function and the restrictions of the system are clearly presented. In addition, a simple modification of the NRTL equation for the Gibbs energy of mixing (GM) is proposed including a ternary term and a binary correction based on the Wohl equation. This modification has significantly improved the quality of the results obtained in the simultaneous correlation of different equilibrium regions

Should we trust all the published LLE correlation parameters in phase equilibria? Necessity of their assessment prior to publication

The review of a representative number of papers published in recent years that include the correlation of experimental liquid-liquid equilibrium (LLE) data has been carried out, after detecting serious inconsistencies in some of the parameters recently published. The result of this analysis shows that surprisingly many published parameters and calculated LLE data are inconsistent for different reasons, for instance: a) some parameters predict a type of system different from the experimental one, b) calculated tie-lines with the published parameters do not satisfy the Gibbs stability criteria, and c) in other cases do not even satisfy the isoactivity LLE condition. In most of these papers, the erroneous common final conclusion was a good agreement between the experimental and calculated tie-lines using these inconsistent parameters. Because these problems were not detected by the authors (when preparing the manuscript) nor by reviewers (during the review process), the necessity of a strategy for the validation of parameters (and compositions) calculated in LLE data fitting became evident. Such procedure should be applied to all LLE data correlation papers, prior to their publication in order to ascertain their consistency and quality. In this paper we suggest some possible tools that could be useful for this assessment

Comments on the correlation of vapor–liquid equilibrium (VLE) data in azeotropic ternary systems

The analysis has been carried out of the possible theoretical types of ternary systems regarding the distillation boundaries, for systems involving up to three binary azeotropes and one ternary azeotrope. The study reveals that there are some of these theoretical behaviors that classical activity coefficient models such as NRTL cannot predict. The objective of the present work is to show these limitations, analyze their causes and suggest possible solutions. The addition of one ternary interaction term to the Gibbs energy of excess function removes many of the limitations of classical models expanding the number and type of systems that could be correlated with the models and, what is more important, markedly improving the correlation capability of the model

Correlation of three-liquid-phase equilibria involving ionic liquids

The difficulty in achieving a good thermodynamic description of phase equilibria is finding a model that can be extended to a large variety of chemical families and conditions. This problem worsens in the case of systems containing more than two phases or involving complex compounds such as ionic liquids. However, there are interesting applications that involve multiphasic systems, and the promising features of ionic liquids suggest that they will play an important role in many future processes. In this work, for the first time, the simultaneous correlation of liquid–liquid and liquid–liquid–liquid equilibrium data for ternary systems involving ionic liquids has been carried out. To that end, the phase diagram of the water + [P6 6 6 14][DCA] + hexane system has been determined at 298.15 K and 323.15 K and atmospheric pressure. The importance of this system lies in the possibility of using the surface active ionic liquid to improve surfactant enhanced oil recovery methods. With those and previous measurements, thirteen sets of equilibrium data for water + ionic liquid + oil ternary systems have been correlated. The isoactivity equilibrium condition, using the NRTL model, and some pivotal strategies are proposed to correlate these complex systems. Good agreement has been found between experimental and calculated data in all the regions (one triphasic and two biphasic) of the diagrams. The geometric aspects related to the Gibbs energy of mixing function obtained using the model, together with the minor common tangent plane equilibrium condition, are valuable tools to check the consistency of the obtained correlation results