Page 134 - Distillation theory

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5

Distillation Trajectories and Conditions

of Mixture Separability in Simple Infinite

Columns at Finite Reflux

5.1. Introduction
This chapter is the central one of the book; all previous chapters being introductory
ones to it, and all posterior chapters arising from this one. Distillation process in
infinite column at finite reflux is the most similar to the real process in finite
columns. The difference in results of finite and infinite column distillation can be
made as small as one wants by increasing the number of plates. Therefore, the main
practical questions of distillation unit creation are those of separation flowsheet
synthesis and of optimal design parameters determination (i.e., the questions of
conceptual design) that can be solved only on the basis of theory of distillation in
infinite columns at finite reflux.
The significance of such theory and, in particular, the significance of develop-
ment of minimum reflux number calculation methods has been clear for numerous
investigators all over the world since the beginning of distillation science devel-
opment. A great number of publications have been devoted to these questions.
However, the general distillation theory at finite reflux was created only lately
on the basis of unification of several important ideas and theories of geometric
nature. One can refer to the latter the idea of examination of distillation trajec-
tory bundles at finite reflux for fixed product composition, the conception of sharp
separation of multicomponent mixtures, the theory of location of reversible dis-
tillation trajectories in the concentration simplex, the theory of trajectory tear-off
from the boundary elements of concentration simplex at finite reflux, and the
theory of section trajectories joining.
The whole history of investigation of distillation in infinite columns at finite
reflux can be divided into three main stages: creation of distillation theory for
binary mixtures, creation of distillation theory for multicomponent ideal mixtures,
and creation of general distillation theory for all kinds of mixtures.
The development of the McCabe and Thiele diagram (McCabe & Thiele, 1925)
that allowed minimum reflux number and minimum number of theoretic plates for
binary mixtures was of decisive significance for the creation of distillation theory
for such mixtures. For many years, this diagram was the basis for investigation of

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