The optimal structure and operation of a batch distillation column separating ternary mixture are discussed from the viewpoint of energy conservation. The optimal reflux operation, which minimizes energy consumption, is derived for three types of batch distillation columns: rectifying, stripping and total reflux columns. The separation performance measured in terms of energy consumption is calculated for each column under different conditions. The results of the example problems show that the separation performance of the total reflux column can be considerably improved by optimizing reflux flow rate, while those of the rectifying and the stripping columns can not be. In all example cases, the separation performance of the total reflux column is equal to or even better than those of the other two columns. It is experimentally verified using a pilot plant that the energy consumption of the total reflux column can be drastically reduced when the optimal operation is used.