In this paper, the energy-saving potential of a heterogeneous azeotropic dividing-wall column is investigated by demonstrating an example for the separation of pyridine and water using toluene as entrainer. The original two-column system includes a heterogeneous azeotropic column with top decanter and another column served as preconcentrator column for the fresh feed and also served as recovery column for aqueous outlet stream from decanter. It is demonstrated that this complex two-column system can be thermally coupled into a dividing-wall column with top decanter. By comparing the optimized design of this dividing-wall column with the original design, a significant reduction (29.48%) in steam cost can be obtained. Furthermore, because important control degree-of-freedoms (two reboiler duties) are still preserved in this dividing-wall column, control performance of this proposed design is found to be comparable to that of the original two-column system.