A Short Note on Steady State Behaviour of a Petlyuk Distillation Column by Using a Non-Equilibrium Stage Model

A Petlyuk distillation column, considering equilibrium and non-equilibrium stage models, was studied. Rigorous simulations were conducted using Aspen Plus™ RATEFRAC Module for the separation of ternary mixtures. According to the equilibrium model, the energy-effi cient design of the Petlyuk column requires that the intermediate component be extracted from the maximum point in the composition profi le in the main column. It was found that, for the intermediate component, mass transfer occurs from the vapour to the liquid phase from the top of the column to the stage where the side stream is extracted, from this point mass transfer occurs in the opposite direction. This point, considering the nonequilibrium model, corresponds to the stage in which the net mass transfer rate is zero. For the case of two segments per stage, it was found that the heat duties predicted by the equilibrium model are signifi cantly lower than those obtained by using the non-equilibrium model, which is consistent with previous reported results. However, it is important to say that despite the higher energy duty predicted by the non-equilibrium model; both models predict signifi cant energy savings.

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