Inflection Point Engineering Calculators

Distillation Shortcut — Fenske / Underwood / Gilliland

Minimum stages, minimum reflux, actual theoretical stages, and feed stage for a binary or pseudo-binary distillation by the shortcut FUG method. Underwood root is solved numerically by bisection between 1 and α.

References: Fenske (1932), Underwood (1948), Gilliland (1940), Molokanov et al. (1972), Kirkbride (1944). Validated against: Wankat, Separation Process Engineering, 4th ed., Ch. 7 (benzene–toluene worked example). Shortcut method only — not a substitute for rigorous stage-by-stage simulation (Aspen, ProMax) for design.