Analogy Between Residue Curves and Distillation Trajectories Under Infinite Reflux

Analogy Between Residue Curves and Distillation Trajectories Under Infinite Reflux 

Investigations of residue curves have been conducted for over 100 years, beginning Ostwald (1900) and Schreinemakers (1901). Later, close correspondence between residue curves (i.e., curves of mixture composition change in time at the open evaporation) and distillation trajectories at infinite refiux (i.e., lines of mixture composition change at the plates of the column from top to bottom) was ascertained. 

The similarity and the difference of these lines are defined by their equations  

Trajectories of Distillation in Infinite Columns Under Infinite Reflux 

The distillation trajectory under infinite reflux is a line of conjugated liquid-vapor tie-lines, each of which corresponds to one of the column plates, in accordance with Eq. (3.2). In the works (Zharov, 1968 Zharov Serafimov, 1975), the broken line of conjugate hquid-vapor tie-lines is replaced with a continuous c-line, for which the liquid-vapor tie-hues are chords (Fig. 3.1a). At the same time it follows from Eq. (3.1) that the hquid-vapor tie-line is a tangent to the residue curve. Therefore, hquid-vapor tie-line, on the one hand, is a tangent to residue curve and, on the other hand, is a chord of the c-line. This fact determines the similarity and the difference between the residue curves and the c-lines (see Fig. 3.1b). In Fig. 3.1c, it is shown that the distillation trajectory under the infinite reflux (c-hne) crosses the set of residue curves. 

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