Phase Equilibrium Correlation: Regarding the full consistency of the thermodynamic parameters obtained

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Title: Phase Equilibrium Correlation: Regarding the full consistency of the thermodynamic parameters obtained
Authors: Labarta, Juan A. | Olaya, Maria del Mar | Marcilla, Antonio
Research Group/s: Computer Optimization of Chemical Engineering Processes and Technologies (CONCEPT)
Center, Department or Service: Universidad de Alicante. Departamento de Ingeniería Química
Keywords: Liquid | Equilibrium | Termodynamic | Consistency | NRTL | UNIQUAC | Phase | Equilibria | Gibbs | Energy | Mixing | Excess
Knowledge Area: Ingeniería Química
Date Created: 14-Aug-2017
Issue Date: 2-Oct-2017
Abstract: The correlation of experimental equilibrium data by using any thermodynamic model is an essential task in order to allow the optimal design or simulation of the equipment or processess where that equilibrium is present. In this sense, the quality of the calculations made, especially in liquid-liquid equilibrium systems, depends strongly on the accurancy of the parameters used to reproduce the system under study. In a previous work (1) we have detected a relevant number of published inconsistencies that motivate the present contribution intended to: a) remark the necessity of refreshing the relevant role that has the topological analysis of the GM/RT function has to avoid false solutions and b) summarise a procedure that allows to any researchers on this topic, to confirm the coherence of the correlation parameters obtained in the correlation process. Basically, the main steps of the proposed procedure are: i) Check the partial miscibility for the different calculated binary subsystems and assure their coherence with the experimental data and expected behaviours. This task can be done easily by cheking the corresponding GM/RT curve (and/or its frist and second derivative) in all the binary subsystems (in the whole range of compositions). ii) Check the consistency of the different tie-lines. At this point it is neccesary to confirm two different points: a) the non-existence of metastable solutions (Gibbs minor common tangent test) and b) the full compliance of the isoactivity criterion. In this case, the revision has to be done by cheking the corresponding GM/RT curve in the whole range of compositions along the tie-line (calculated and/or experimental). iii) Aditonal comprobations can also be considered, such as to confrm the existence of a consistent binodal curve, and to assure that the model does not predict regions of inmiscibility not physicaly existing. These can be acomplished by analysing the determinant of the Hessian matrix and representing the GM/RT surface to check the whole range of compositions. Based on these ideas we developed as example a simple but very useful tool, using a Graphical User Interface (2) in MatLab, to visualized the Gibbs energy of mixing surface (for ternary systems). Thus, the consistency of the model and parameters used could be easily checked (3). Obviously, this procedure could also be used to analyse LV and LLV equilibrium correlations.
Description: Abstract and Presentation in the 10th World Congress of Chemical Engineering, Barcelona, 1st-5th October, 2017.
URI: http://hdl.handle.net/10045/70035
Language: eng
Type: info:eu-repo/semantics/conferenceObject
Rights: Licencia Creative Commons Reconocimiento-NoComercial-SinObraDerivada 4.0
Peer Review: no
Appears in Collections:Docencia - Ingeniería y Arquitectura - Presentaciones
INV - CONCEPT - Comunicaciones a Congresos, Conferencias, etc.

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