Distillation subregions structures

The totality of all bonds characterizes the mixture s structure. The bond serves as the elementary nonlocal characteristic of the residue curve bundle structure. Bonds form bond chains. The bond chains of maximum length connect the unstable node A and the stable node A+ of the distillation region Reg". Let s call a polyhedron formed by aU stationary points of one maximum-length bond chain and containing aU components of the mixture a distillation subregion Reg. ... 

A bond, bond chain, distillation subregion, andregion are the nonlocal structural elements of the azeotropic mixture concentration space. 

Bonds between the stationary points (points of the components and azeotropes) and distillation subregions Reg j are the structural elements of the distillation regions. Residue curve bundle structure of multicomponent mixtures can be described with the help of a structural matrix that reflects the bonds available between the stationary points. 

However, the above-described method is unfit for splits other than the direct and indirect ones, and the number of such splits grows dramatically with the increase of n. The general methods of splits set determination are based on the usage of structural matrix and of method of product simplex for distillation subregions (Petlyuk, Kievskii, Serafimov, 1979). 

Figure 3.16. Regions Reg°° and subregions Regsa of distillation and product simplexes B.egsimp of some structures of three-component mixtures. 1,3.4a,..., classification according to Gurikov (1958). Dotty lines with arrows, boundaries of distillation regions thin lines, boundaries of distillation subregions dotted lines, boundaries of product simplexes.

In Sections 1.3 to 1.5, the residue curve bundles, which characterize the direction of Uquid-vapor tie-lines in each point of the concentration space (i.e., the phase equilibrium field), were considered. As stated previously, such characteristics of the phase equilibrium field and structural elements related to it (bonds, distillation regions, and subregions) are the most important for one of the distillation modes, in particular, for the infinite reflux mode. 

Figure 3.9. Subregions of distillation under infinite reflux Regsa for some structures of three-component mixtures and product regions for given xp, 3,4a,4b... — classification according to Gurikov (1958). Product regions are shaded bottom regions are darker shaded.

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