Vapor-Liquid-Liquid Equilibrium (VLLE)
This Demonstration shows the phase equilibrium for a system of two partially miscible liquids (A and B) on a T-x-y phase diagram. Because of the partial miscibility, vapor-liquid equilibrium (VLE), liquid-liquid equilibrium (LLE), and vapor-liquid-liquid equilibrium (VLLE) are possible. You can move the black dot on the phase diagram by changing the mole fraction of component B and the heat added using sliders. The heat added (or removed) changes the temperature, except when at 77°C, where all three phases are in equilibrium: alpha liquid, beta liquid, and vapor (yB = 0.60) At 77°C, one phase must completely evaporate (or condense if removing heat) before the temperature increases (or decreases). The relative amounts of each phase, which are determined from mole balances, are shown in the bar graph. The mole fraction of component B in each phase present is also displayed on the bar graph. In the multiple phase regions, vertical dashed lines show the mole fractions of B in each phase.

Download the CDF file to view the simulation using the free Wolfram CDF player.