NGL Fractionation Column Sizing

FUG Shortcut Method

This calculator uses the Fenske-Underwood-Gilliland (FUG) shortcut method per GPSA Section 19:

• Fenske: Minimum stages at total reflux (N_min)
• Underwood: Minimum reflux ratio (R_min)
• Gilliland: Actual stages at operating reflux
• Fair: Column diameter from vapor loading
• Kirkbride: Optimal feed tray location

GPSA Typical Operating Ranges

• Deethanizer: 250-450 psia, 30-50 trays, α ≈ 2.5-3.0
• Depropanizer: 180-300 psia, 25-40 trays, α ≈ 2.2-2.6
• Debutanizer: 60-150 psia, 20-35 trays, α ≈ 2.0-2.4
• Butane Splitter: 100-200 psia, 80-120 trays, α ≈ 1.1

Design Notes

• Reflux ratio: R = 1.1-1.3 × R_min is economic optimum
• Tray efficiency: O'Connell correlation gives η = 0.70-0.85
• Diameter sizing: Design at 75-85% of flooding velocity
• Tray spacing: 24" standard for NGL; 18" for small columns
• Pressure drop: ~0.1-0.2 psi per tray typical

Limitations

• FUG assumes constant relative volatility (α ± 20%)
• Results are ±10-20% for preliminary design
• Multicomponent feeds require rigorous simulation
• Verify with HYSYS/Aspen before final design