Size a debutanizer column with the Fenske-Underwood-Gilliland method: stages, reflux, and duty.
| Parameter | Range |
|---|---|
| Pressure | 75–150 psig |
| Overhead Temp | 120–160°F |
| Bottoms Temp | 300–400°F |
| Reflux Ratio | 1.0–2.5 |
| Trays | 25–40 |
Fenske Equation (Minimum Stages):
Where xLK,D = light key (nC₄) mole fraction in distillate, xHK,B = heavy key (iC₅) mole fraction in bottoms, α = average relative volatility of nC₄ to iC₅.
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 debutanizer design, nC₄/iC₅ separation principles, and natural gasoline production
A debutanizer (DeC4) is a fractionation column that separates C₄ (butanes) from C₅+ (natural gasoline/pentanes+). It produces mixed butane product overhead and natural gasoline as bottoms product.
This calculator uses the Fenske-Underwood-Gilliland (FUG) shortcut method per GPSA §19 and GPA 2140. It calculates minimum stages, minimum reflux ratio, actual trays, column diameter, and reboiler/condenser duties.
Typical debutanizer conditions include 75–150 psig pressure, 120–160°F overhead temperature, 300–400°F bottoms temperature, reflux ratio of 1.0–2.5, and 25–40 trays.
In a debutanizer, the light key is n-butane (nC₄) and the heavy key is iso-pentane (iC₅). The separation is based on the relative volatility between these two components.