Prediction of thermodynamic consistency of vapour-liquid equilibrium of a two-phase system in the presence of the salting-in and salting-out effects
Che-Galicia, Gamaliel Dutta, Abhishek × Dhar, Abhishek Ramana Murthy, B. Venkata Al-Zahrani, Mohammed Ibrahim Raychaudhuri, Uttam François, An Castillo, Carlos O. #
Taylor & Francis
Indian Chemical Engineer vol:58 issue:2 pages:106-117
Salt effect on vapor liquid equilibrium (VLE) has been a subject of intense investigation from experimental and modeling perspectives since the salting-in and salting-out effects might eliminate the possibility of azeotrope formation at saturation. Nevertheless, thermodynamic consistency evaluation of data generated from this type of studies, accounting for non-idealities of one or two of the phases involved is mandatory. In this communication, a primary evaluation of thermodynamic consistency under a non-ideal VLE situation of data generated for an ethanol-water system with and without the addition of inorganic potassium chloride (KCl) salt is presented. The equilibrium data (T-x-y diagram) for ethanol-water system is generated under isobaric conditions, with and without 2 and 4 g/L concentration levels of KCl. The isobaric VLE data of ethanol-water system saturated with KCl concentrations is correlated by means of a modified Raoult’s law to predict the activity coefficient of the volatile components. Activity coefficients are evaluated using a state equation and fugacities as well. Both methodologies give identical activity coefficients, indicating that Raoult’s law is a simple approach to calculate these parameters. Thermodynamic consistency of VLE data with and without the addition of KCl is validated from a simple but reliable strategy that makes use of the Gibbs Duhem plot and Murthy’s approach which avoids the use of enthalpy of mixing.