This paper reports on the performance of an internally Heat-Integrated Distillation Column (HIDiC) in separation of ternary mixtures. Separation of two ternary mixtures, benzene-toluene-p-xylene and n-pentane-cyclopentane-2-methylpentane, are studied to determine the effect of the span of boiling points on the performance and the energy savings of the HIDiC. For the former mixture, the HIDiC consumes about 30% less energy than a conventional distillation column, while for the latter mixture, even a higher degree of about 50% reduction of energy consumption is achieved. Although the efficiency of the HIDiC depends heavily upon the mixtures to be separated, it has been found that the HIDiC can be a very efficient alternative for the separation of ternary mixtures provided the span of boiling points is narrow enough to allow feasible application of heat pump techniques. The internal heat integration design and system performance were also evaluated by sensitivity analysis.