Avaliação e aplicação de modelos termodinâmicos no equilíbrio de fases em uma ampla faixa de pressão em sistemas envolvendo água, álcool e hidrocarbonetos

Abstract

The role of thermodynamics models in describing several industrial processes for chemical engineers is essential. Many of those processes involve, mainly, phase equilibrium. This is the case of separation processes equipment, such as distillers, dryers, and decanters. In this manner, this work presents a review over several thermodynamics excess Gibbs energy models, or simply activity coefficients models. In addition, the use of these models was investigated when they were coupled to equations of state by using mixing rules. The models were addressed in different ways in order to perform phase equilibrium calculations, be them vapor-liquid or liquid-liquid. Concerning to the VLE data prediction for the binary systems studied in this work, the UNIQUAC and NRTL (either using literature parameters or optimized parameters) models presented the best results among the correlative models, and among the predictive models the UNIFAC (with estimated parameters) and the COSMO-SAC models yielded the most accurate results. When the predictions of infinite-dilution activity coefficients of the same systems were analyzed, the F-SAC has proved to be the most successful model. The phase-envelope prediction of several ternary liquid mixtures was best performed by the UNIFAC-LLE model, however, for several systems the COSMO-SAC and F-SAC models also presented reliable results. When the mixing rules were applied, the UNIFAC model offered, again, great results, and the UNIFAC+VDW1+PRSV combination the most accurate among the 45 combinations that were tested. The COSMO-SAC model has revealed significant unconformity in the VLE predictions when associated to an EOS by the HVOS mixing rule. It was also observed that the mixing rules results tend to deteriorate as the chain-length of the alkane present on the mixture becomes larger.