# Flash Distillation of a Constant Relative Volatility Mixture

Flash Distillation of a Constant Relative Volatility Mixture

Consider a binary mixture with a constant relative volatility . The thermal quality of the mixture, , is to be set by the user. This mixture is fed to an isothermal flash drum.

α

q

The liquid and vapor mole fractions of the two product streams (i.e. one vapor and one liquid) are solutions of the mass balance and equilibrium relationship given by:

y=x+

q

q-1

z

1-q

y=

αx

1+(α-1)x

where is the feed composition (i.e. mole fraction of the light component).

z

A simple algebraic manipulation of the two equations gives the following quadratic equation, which can be solved for :

x

1-f

f

2

x

1-f

f

(α-1)

f

z

f

where is the vapor fraction of the feed.

f=1-q

This Demonstration shows the graphical solution, the intersection point (in cyan) of the equilibrium curve (red) and the operating line (blue), as well as the flash drum setup.