PINTO, F. S. L.; PINTO, Flávio Sérgio Lima.
Résumé:
The great importance of the distillation process is due to the
effectiveness in the separation of the most different mixtures. However, the
operation of distillation columns demands great amount of energy, what has
been motivating researches in the sense of reducing this energy consumption.
The economy, in investment terms and operational costs, in distillation
processes can be gotten through the substitution of conventional columns (twoproducts
column) for columns with lateral retreat (side-stream column).
Intuitively, the lateral current should contain mainly the intermediary
component. Besides, the literature suggests that this lateral current is in the
vapor phase if the retreat happens below the feeding and in the liquid phase if
above feed, according the indication of Tedder and Rudd (1978). In this point,
the residual curves become of fundamental importance for choice of systems
where we can substitute conventional columns for columns with lateral retreat.
Using the approach of the residual curves, this work shows a new processe
and new distillation sequences for old processes. The studies were
accomplished for mixtures azeotropics, so that the lateral current could be a
binary azeotropic or a pure component. The obtained results show that the
advantage of the columns with lateral retreat depends on the location of the
initial feeding in the composition triangle. Another interesting conclusion is that
the lateral retreat can happen in the liquid phase, even the retreat being
located below the feeding. However, the use of the residual curves as
approach for definition of separation sequence should be careful, because, in
some cases this approach affirms to be impossible a separation when, in fact,
the separation is extremely easy. An example of this situation is the
dehydration of aqueous mixtures of etanol using ethylene glycol as solvent.
