Distillation

On a diagram such as the Txy and Pxy diagrams, the line connecting the boiling point curve and the dew point curve in parallel is called a tie line. The relationship between the material balance on this line is called the leverage principle for distillation.

The measure of how easily two components can be separated by distillation is called relative volatility or specific volatility. It is an important indicator in distillation because a vapor-liquid equilibrium curve can be drawn if the relative volatility α is known.

A graph that shows the relationship between liquid phase composition x, gas phase composition y, and pressure P for two components at a constant temperature is called a Pxy diagram.

A graph that shows the relationship between the liquid phase composition x, gas phase composition y, and temperature T for two components at a constant pressure is called a Txy diagram.

A graph that shows the vapor-liquid equilibrium relationship of two components is called an xy diagram. xy diagram means that the vapor-liquid equilibrium composition of the two components at a certain temperature and pressure will be the value on the vapor-liquid equilibrium curve, and the vapor-liquid equilibrium curve is obtained and used in the design of the distillation column.