Parameters
Relative Volatility α
2.50
Higher α = easier separation
Distillate Composition xD
0.95
Bottoms Composition xB
0.050
Feed Composition zF
0.500
Feed Condition q
1.00
0=sat. vapor / 1=sat. liquid / >1=subcooled
Reflux Ratio Multiplier R/Rmin
1.50
—
Theoretical Stages N
—
Min Stages Nmin
—
Min Reflux Rmin
—
Actual Reflux R
—
Feed Stage
—
Distillate Purity xD
—
Bottoms xB
—
Rel. Volatility α
Reflux Ratio vs Theoretical Stages
Design Equations
VLE (vapor-liquid equilibrium): $y = \dfrac{\alpha x}{1 + (\alpha-1)x}$
Rectifying operating line: $y = \dfrac{R}{R+1}x + \dfrac{x_D}{R+1}$
Fenske equation (minimum stages): $N_{min} = \dfrac{\log\!\left[\dfrac{x_D}{1-x_D}\cdot\dfrac{1-x_B}{x_B}\right]}{\log\alpha}$
q-line: $y = \dfrac{q}{q-1}x - \dfrac{z_F}{q-1}$
Process Engineering Applications: Petroleum refining (crude distillation, vacuum towers), chemical plants (ethanol-water separation), LNG production. Stage calculations are used for Aspen Plus model validation and column revamp studies.