A distillation column separating ethanol from water is shown in the following figure. Pressure is \(1 \mathrm{~kg} / \mathrm{cm}_{2}\). Instead of having a reboiler, 100 \(\mathrm{kg} / \mathrm{min}\) of saturated steam (pure water vapor) is injected directly into the bottom of the column to provide heat. Feed rate is \(100 \mathrm{~kg} / \mathrm{min}\) of \(30 \mathrm{wt} \%\) ethanol at \(20^{\circ} \mathrm{C}\). Reflux is a saturated liquid. Distillate concentration is 60 \(\mathrm{wt} \%\) ethanol, and bottoms product is \(5 \mathrm{wt} \%\) ethanol. What is the external reflux ratio, \(\mathrm{L} / \mathrm{D}\) ?

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Qcol = 0 F,Z V Qc L D, XD Ys,S B,XB