Thermodynamically equivalent distillation schemes to the Petlyuk column for ternary mixtures

Thermally coupled distillation sequences for ternary separations have been shown to provide significant energy savings with respect to the conventional direct and indirect distillation sequences. Although the Petlyuk column is generally more efficient than the other thermally coupled schemes, its structure creates potential operating problems because of the bi-directional vapour interconnecting streams. In this paper, second law calculations were performed for the Petlyuk column and six alternative distillation schemes that show unidirectional flows; in principle, such alternative configurations are expected to present better operational properties than those of the original Petlyuk column. The results indicate that the proposed distillation arrangements have values of thermodynamic efficiency very close to that of the Petlyuk column. This result is important because let us establish that the alternative distillation sequences: (i) are thermodynamically equivalent to the Petlyuk column, (ii) could be more easily implemented in practice, and (iii) also achieve significant energy savings.