The concentration process of an alcohol used for the intermediate material in the production of plasticizer is examined for the energy conservation of energy-efficient distillation system instead of the conventional two column system through numerical simulation.Some 41% of energy conservation is expected from the proposed system,and its conservation principle is explained with colunm profiles.In addition,not only the operating cost but also investment cost can be reduced for the additional benefit of the column application when the thermally coupled distillation is implemented.