Aplicação do método da minimização da energia de Gibbs no cálculo de equilíbrio químico e de fases em sistemas eletrolíticos / Application method of the Gibbs energy minimization to calculation of phase and chemical equilibrium in electrolyte systems

AUTOR(ES)

Valter Nunes Trindade Júnior

FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

14/12/2011

RESUMO

In several industrial applications are used mixtures containing different solutes, often these solutes are non-volatile, such as electrolytes. The phase and chemical equilibrium in these processes occur in the various unit operations. The stages of production, as well as the separation and purification steps are critical to product quality. Thus, the calculation of the behavior of the equilibrium of salts in solvents is of great importance for the design and optimization of this type of equipment. The main objective of this work was to develop a methodology for calculation of the combined phase and chemical equilibrium in electrolytic solutions. In this study, the behavior of the equilibrium was done by varying the pressure and the temperature in the systems studied. In the model were made the following considerations: a vapor phase, n liquid phase and a solid phase, using the methodology of minimizing the Gibbs energy. The vapor phase was considered ideal and phase solida was considered as pure solid. To represent the nonideality of the liquid phase we used the electrolyte NRTL model (e-NRTL), in this way, the problem should be treated as a nonlinear optimization problem. The results were compared with literature data with solutions containing an electrolyte in solvent or solvents mixtures for Solid-Liquid and vapor-Liquid equilibrium. The modeling was written as a nonlinear programming. The advantage of this program is not having to know in advance what phases will be formed, the process of minimization of Gibbs energy determines the phases automatically. The program was solved in GAMS® software (General Algebraic Modeling System), version 23.2.1, with CONOPT solver that uses the Generalized Reduced Gradient algorithm.

ASSUNTO(S)

otimização gibbs energia livre de soluções eletroliticas equilíbrio sólido-liquido equilíbrio líquido-vapor optimization gibbs free energy electrolyte solutions solid-liquid equilibrium vapor-liquid equilibrium

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