Work out distillation reflux ratio instantly with clear inputs, formula shown and shareable results.
Reflux ratio is the liquid returned to the column divided by the distillate withdrawn. Since everything condensed at the top either returns or leaves, the vapour reaching the condenser is L + D, and the internal ratio L/V is what sets the slope of the operating line. Returning 80 against 20 drawn off is R = 4, meaning 80% of the overhead vapour goes back down the column.
Reflux ratio
R = L / D
Vapour and internal ratio
V = L + D, and L/V = R / (R + 1)
More liquid returning means more vapour-liquid contact per tray, so separation improves - at the cost of reboiler duty and condenser load.
Taking no distillate at all, so R is infinite. It gives the maximum separation and the minimum number of trays, and is used for start-up and testing.