GPSA Ch. 16 / Fenske-Underwood-Gilliland
| Parameter | Range |
|---|---|
| Pressure | 350–500 psig |
| Overhead Temp | −20 to 20°F |
| Bottoms Temp | 150–250°F |
| Reflux Ratio | 1.0–3.0 |
| Trays | 25–40 |
Fenske Equation (Minimum Stages):
Where xLK,D = light key mole fraction in distillate, xHK,B = heavy key mole fraction in bottoms, α = average relative volatility of light key to heavy key.
Gilliland Correlation:
Correlates actual stages N to actual reflux ratio R given minimum stages Nmin and minimum reflux Rmin from the Underwood equation.
Underwood Equation: Determines minimum reflux ratio Rmin from feed composition, feed condition (q), and relative volatilities. Combined with Gilliland correlation to find actual stages at the design reflux multiplier.
Column Diameter: Sized from vapor/liquid traffic using Fair’s flooding correlation at the design flood fraction.
Understand deethanizer design, NGL fractionation principles, and shortcut distillation methods
A deethanizer (DeC2) is a fractionation column that separates ethane (C₂) from propane and heavier components (C₃+). It typically operates at 350–500 psig with overhead temperatures of −20 to 20°F.
This calculator uses the Fenske-Underwood-Gilliland shortcut method per GPSA Ch. 16, ASME Section VIII, and GPA 2140 to determine minimum stages, reflux ratio, actual trays, column diameter, and heat duties.
Typical deethanizer conditions include 350–500 psig pressure, −20 to 20°F overhead temperature, 150–250°F bottoms temperature, reflux ratio of 1.0–3.0, and 25–40 trays.
In a deethanizer, the light key is ethane (C₂) and the heavy key is propane (C₃). The Fenske equation uses the relative volatility between these two components to determine minimum theoretical stages.