Distillation boundaries originate from saddle azeotropes, dividing the composition space into distillation regions. In heterogeneous mixtures distilled in packed columns, distillation regions overlap. The common area of distillation regions is parametrically sensitive, and it determines the possibilities of crossing (at a finite reflux) the distillation boundaries defined for a total reflux or reboil ratio. This work is an extended research of the paper (Królikowski et al., 2011) conducted to scrutinize whether the distillation regions overlapped in heteroazeotropic systems distilled in staged columns. Presented studies were performed by finding such composition points of the products, for which the rectifying profiles of staged columns were ended in different distillation regions. Calculations were executed for the heterogeneous mixture classified under Serafimov's topological class as 3.1-2: ethanol - benzene - water. Distillation regions for staged columns were found to overlap each other in the heterogeneous systems. As a result, their common part was parametrically sensitive.

Fast development of computation techniques for electrolyte activities contributed recently to introduction of a few substantial programmes for thermodynamic computing of multiphase systems. The presented study comprises useful information for practical computing using selected thermodynamic models of aqueous electrolyte solutions. Those models enable quantitative description of both phase and ionic equilibria and provide values of activity coefficients. The carried out analysis of individual models involved a comparison of their practical effectiveness features along with problems encountered in evaluation of the coefficients. The authors conclude that for the Solvay soda system the exUNIQUAC model for an in-house code or the MSE model for a commercial one can be used.

This is an extended research of the paper (Islam et al., 2011) conducted to obtain a universal set of interaction parameters of the model NRTL over the temperature range 10 - 100 °C for hexane-butanol-water system; meaning for binary pairs hexane-butanol, butanol-water and hexane-water; and for ternary system hexane-butanol-water. Thorough investigations of data selections for all binary pairs (Vapor-Liquid Equilibrium (VLE), Liquid-Liquid Equilibrium (LLE)), infinite dilution activity coefficient (γ∞), infinite dilution distribution coefficient (Dsw), excess enthalpy (HE), and for ternary system (LLE of hexane-butanol-water) were carried out. Finally quadratic temperature dependent interaction parameters were estimated regressing all the mentioned data and in each case calculated results were compared with literature values. The comparisons showed an overall percentage of error within 15% for the mentioned phase equilibrium calculations.