Abstract:

Distillation is a typical unit operation for separating liquid mixtures. The temperature–composition curve in the gas–liquid equilibrium phase diagram is important for guiding distillation operations. An ideal liquid mixture with two components was utilized as the study system in this work. We proved that the temperature–composition curve (T–x or T–y) of ideal liquid mixtures with two components is strictly monotonic, regardless of whether the saturated vapor pressure of liquid conforms to the Clausius-Clapeyron equation or Antoine equation. This means that the bubble point temperature and dew point temperature increase monotonously with the increase of lowly volatile substance content.

Key words: Distillation, Bubble point equation, Dew point equation, Raoult's law, Ideal liquid mixture