Three types of thermally coupled distillation systems, namely the sequence with side rectifier, the sequence with side stripper and the Petlyuk column, have been shown to provide significant energy savings for the separation of ternary mixtures with respect to the conventional direct and indirect sequences. Although the Petlyuk column in general is more energy efficient than the other options, its structure creates potential operating problems because of the bidirectional flow of the vapor interconnecting streams. Alternative options with potential operational advantages have been recently suggested. In this paper we analyze the energy performance of six alternative schemes to the Petlyuk system with thermal coupling. Two of them make use of two interconnections with unidirectional flow, while the other four show a reduction in the number of interconnections. It is shown that several of the alternate options provide similar energy savings to the Petlyuk column.
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