To determine the behavior of a distillation column over wide ranges of operating conditions, calculational procedures are needed for treating certain limiting conditions which arise such as D = 0 and D = F. Procedures are presented and discussed below.
One of the more interesting results obtained in this section is shown in Fig. 10-3. Examination of this figure shows that as the distillate rate is varied from D = 0 to D = F at a fixed reflux rate Ll9 there exists a particular D (0 < D < F) at which the mole fraction of each component other than the lightest and the heaviest of the mixture passes through a maximum. The lightest component is seen to have its maximum XD at D = 0, and the heaviest component has its maximum XD (namely XD = X) at D = F. The results shown in Fig. 10-3 were obtained by solving Example 10-1 at each of several distillate rates ranging from D = 0 to D = F at Lj = 125.
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