Enter compositions and relative volatility — get minimum stages, minimum reflux, actual stages and the feed stage.
Open the calculator →EnggiBasis takes your feed, distillate and bottoms specifications and returns a complete shortcut column design — the theoretical stages, the reflux ratio and the feed location — using the classic McCabe-Thiele graphical method for binaries and the Fenske-Underwood-Gilliland (FUG) shortcut for multicomponent systems. Then it sizes the column diameter and internals.
N_min = ln[(x_D/(1−x_D)) · ((1−x_B)/x_B)] / ln(α)
the minimum theoretical stages at total reflux, from the light-key purities and the relative volatility α.
Underwood's equations give the minimum reflux ratio R_min. Real columns run at R ≈ 1.1–1.5 × R_min to trade stages against energy.
The Gilliland correlation converts R and R_min into the actual stage count N; Kirkbride's ratio locates the feed stage. EnggiBasis does all of it and draws the McCabe-Thiele diagram.
Shortcut, then detail. FUG gives you the design fast; EnggiBasis then hands the traffic (V, L) to the hydraulics module to size tray or packed-column diameter — the same handoff a rigorous simulator makes.
| Input | Value |
|---|---|
| Relative volatility α | 2.4 (benzene / toluene) |
| Distillate purity x_D | 0.95 |
| Bottoms x_B | 0.05 |
Result: N_min = ln[(0.95/0.05)(0.95/0.05)] / ln(2.4) ≈ 6.7 stages at total reflux — the floor before you add reflux and real-tray efficiency. Run your own separation →
Fenske for minimum stages, Underwood for minimum reflux, Gilliland for the actual stage count at your operating reflux. McCabe-Thiele gives the same graphically for binaries.
N_min = ln[(x_D/(1−x_D))·((1−x_B)/x_B)]/ln(α).
Binary McCabe-Thiele is free. Multicomponent FUG, hydraulics and column drawing are part of EnggiBasis Pro (₹99/month).
Free binary McCabe-Thiele · FUG & hydraulics in Pro (₹99/month)
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