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.