Avaliação de Diferentes Abordagens na Solução do Problema de Equilíbrio Sólido-Líquido em Óleos Parafínicos

ABSTRACT In this paper, the computational efficiency in the solid-liquid equilibrium (SLE) problem for paraffinic oils was examined. Several different thermodynamic models were evaluated for liquid phase: the Peng-Robinson equation of state (PR-EOS), and the activity coefficient models for ideal solution, the predictive Wilson model, the predictive Universal Quasi-chemical (UNIQUAC) model, and UNIQUAC Functional-group Activity Coefficient (UNIFAC) model. The solid phase is characterized by the multisolid model and the prediction of solid phase formation is initially estimated by a thermodynamic stability test. Afterwards, the systems of non-linear equations (SNLE) formed by the thermodynamic equilibrium and the material balance equations was solved using Newton-Raphson method (multivariate). As far as we can see, there are no systematic studies addressing the effect of the model (and its complexity) on the computational effort of the algorithm. On the other hand, considering the high number of different components in the oil fractions studied, the robustness (due to different initial estimates), and the computational time are important aspects and were analyzed in this work.