Batch boiling residue curves

It is also customary to show the positive direction of movement of the residue curves on the maps [3]. This direction corresponds to the way the tr ectory would be generated during batch boiling, and is therefore related to forward integration towards positive infinity. Thus, the profiles move from the low-boiling component to the high-boiling component, as indicated. 

Let us consider a mixture of three components A, B, and R. Of special importance are the so-called residue curves, which represent the liquid residue compositions with time in a simple batch distillation. Different curves are obtained for different starting compositions, and a collection of these curves for a given ternary system is called an RCM. A typical RCM is shown in Figure 14.4a. Some important features of these curves should be noted If the direction of the curve is assumed to be from the starting composition to the ending composition, then the arrow on each curve points from the lower-boiling component or azeotrope (if one is formed) to the higher. The presence of azeotropes can create boundaries... 

Figure 6.3.12B. Liquid residue composition curves in simple batch distillation for two types of systems solid lines illustrate residue curves for the ideal system ethanol-isopropanol at 1 atm dashed lines show the residue curves for the minimum-boiling azeotropic system, pentane-dichloromethane system at 1 atm. (Figure developed from figs. 5.2 and 5.4 of Doherty and Malone (2001).)...

---