Section trajectory bundles evolution

Structure and Evolution of Section Trajectory Bundles for Three-Component Mixtures... 

To understand the structure of section trajectory bundles for multicomponent mixtures and their evolution with the increase of reflux number, let s examine first three-component mixtures, basing on the regularities of distillation trajectory tear-off at finite reflux and the regularities of location of reversible distillation trajectories. 

General regularities of the evolutions of sections trajectory bundles, discussed in the previous section for three-component mixtures, are valid also for the mixtures with bugger number of components. Figure 5.23 shows evolution of top section trajectory bundle at separation of four-component ideal mixture, when the product is pure component (i.e., at direct split) Ki > K2 > >... 

So far, discussing distillation trajectories and their bundles, we proceeded from the fact, that separation stages are equilibrium ( theoretical plates). In real separation process at plates of distillation columns equilibrium is not achieved and the degree of nonequilibrium is different for different components. That leads to decrease of difference between compositions at neighboring plates and to change of curvature of distillation trajectories (Castillo Towler, 1998), but does not influence the location of stationary points of distillation trajectory bundles because in the vicinity of stationary points equilibrium and nonequilibrium trajectories behave equally. Therefore, implemented above analysis of the structure and of evolution of section trajectory bundles is also valid for nonequilibrium trajectory bundles. 

The use of the Underwood equation system allows for examination of the evolution of separation product compositions of one- and two-section columns at set feed composition and at variable refiux number. Figure 5.2 shows such evolution for one-section rectifying column (Shafir et al., 1984). This figure also shows trajectory bundles N => A+ (N 5 -> A+) in accordance with the notion of... 

Figure 5.13. The evolution of trajectory bundles of the rectifying section (Reg = RegJ )...

The analysis carried out above (see Figs. 6.8 and 6.9) allows for a general conclusion about dimensionality, structure, and evolution of trajectory bundles (regions) of intermediate section at sharp extractive distillation for any multicomponent mixtures. 

Figure 5.11. The evolution of trajectory (arrow-ended line) bundles of the rectifying section for an ideal mixture with K > K2 > Kj, (component 1 is the product) (a) L/V< Kl,(b) K < L/V < K, (c) L/V > K (the attraction re-...

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