화학공학소재연구정보센터
Fluid Phase Equilibria, Vol.408, 265-272, 2016
Effect of VLE uncertainties on the design of separation sequences by distillation - Study of the benzene-chloroform-acetone system
It is widely recognized by experts that the computer-based design of chemical processes depends strongly on the correlated thermodynamic and transport properties, and that the effect of the property uncertainties should be accounted for in the design. The most significant source of property uncertainties on process design comes from the correlations of mixture phase equilibrium. Many approaches to uncertainty analysis have been proposed, but uncertainty analysis is not a routine element of today's industrial practice, mainly because education and awareness are lacking, and the proposed methods are difficult to apply. In order to help rectify the situation, the author developed an intuitive and easy-to-apply phase-equilibrium (specifically, activity coefficient) perturbation method based upon treating the mixture, for the purpose of uncertainty perturbation, as a set of pseudobinaries described by the Margules equation. The approach was applied to two case studies (1) a propylene-propane superfractionator for which small changes in correlated relative volatilities have a large effect on the design of the distillation column; and (2) a dehexanizer column that separates a mixture containing many close-boiling components - and demonstrated that the proposed methodology provides quantitative insight into the effect of property uncertainties, and helps to estimate the safety factors that should be imposed upon the design. In this paper the Margules perturbation method is applied to the "textbook" separation of an acetone - chloroform benzene ternary mixture; this case study was proposed in 1996 by Westerberg and Wahnshafft, and was previously studied by Parodi and Campanella. The approach of Parodi and Campanella used different levels of data fitting to identify uncertainties, while the present methodology is to obtain the best fit of the data, and then apply uncertainties based upon estimated combined model uncertainties, which includes experimental uncertainties and any model inadequacies. The purpose of this paper is to further study whether the Margules approach to mixture uncertainty offers insight, and is a useful technique to perform uncertainty analysis. (C) 2015 Elsevier B.V. All rights reserved.