Obtaining residual curves maps for homogeneous azeotropic ternary systems: a comparative study

Abstract

Residual curve maps are particularly useful for interpreting azeotropic distillation performance of homogeneous systems. These maps are obtained through a system of differential equations, which is commonly solved in two steps, namely a liquid-vapor equilibrium and a system of differential equations. An alternative solution treats both steps as a single system of equations. The objective of the present work is to compare both solution approaches. The ternary systems, namely ethanol/methyl-cyclohexene/3-methyl-pentane, and ethyl acetate/n-hexane/acetone, are used to this end. The fugacity coefficient of the vapor phase was calculated by the Virial equation, and the activity coefficient of the liquid phase, through the WILSON, NRTL, UNIQUAC and UNIFAC models. The results showed the potential of the alternative method in comparison to the conventional approach. This regards to the computational time spent for obtaining the residual curve maps, equal to 4 and 25 seconds in average, respectively. Other issue concerns the detection of the distillation border, which can be obtained without the computation of the azeotrope points.