Page 103 - Distillation theory

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4

Trajectories of Thermodynamically

Reversible Distillation

4.1. Introduction
Although the thermodynamically reversible process of distillation is unrealizable,
it is of great practical interest for the following reasons: (1) it shows in which
direction real processes should be developed in order to achieve the greatest
economy, and (2) the analysis of this mode is the important stage in the creation
of a general theory of multicomponent azeotropic mixtures distillation.
First investigations of thermodynamically reversible process concerned binary
distillation of ideal mixtures (Hausen, 1932; Benedict, 1947). Later works con-
cerned multicomponent ideal mixtures (Grunberg, 1960; Scofield, 1960; Petlyuk
& Platonov, 1964; Petlyuk, Platonov, & Girsanov, 1964).
The analysis of the thermodynamically reversible process of distillation for
multicomponent azeotropic mixtures was made considerably later. Restrictions
at sharp reversible distillation were revealed (Petlyuk, 1978), and trajectory bun-
dles at sharp and nonsharp reversible distillation of three-component azeotropic
mixtures were investigated (Petlyuk, Serafimov, Avet’yan, & Vinogradova, 1981a,
1981b).
Restrictions at nonsharp reversible distillation of three-component azeotropic
mixtures were studied by Poellmann and Blass (1994).
Trajectories of adiabatic distillation at finite reflux for given product points
should be located in concentration space in the region limited by trajectories at
infinite reflux and by trajectories of reversible distillation (Petlyuk, 1979; Petlyuk
& Serafimov, 1983).
The algorithm, based on this principle and checking for three-component mix-
tures whether it is possible to get either products of given composition at distilla-
tion, was developed by Wahnschafft et al. (1992).
As far as stationary points of trajectory bundles of distillation at finite reflux
lay on trajectories of reversible distillation, these trajectories were also called
the lines of stationarity (pinch lines, lines of fixed points) (Serafimov, Timofeev, &
Balashov,1973a,1973b).Theselineswereusedtodealwithimportantappliedtasks
connected with ordinary and extractive distillation under the condition of finite

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