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Figure 6.9 Composition profiles for reactive distillation of two-column flowsheet with reactive zone placed in column base, feed tray NFA, and fraction of total conversion (Ri/Rt).

Reboiler Tray Number Condenser

Figure 6.9 Composition profiles for reactive distillation of two-column flowsheet with reactive zone placed in column base, feed tray NFA, and fraction of total conversion (Ri/Rt).

reactive trays and increasing their reactive holdup has the opposite effect, which will be explained next.

6.2.5 Number of Reactive Trays

The optimum design has no reactive trays, just a reactive base. However, if five reactive trays are used (upper right graph, Fig. 6.10), increasing the number of reactive trays has <1% influence on the vapor boilup. This is quite different from the system considered previously with an intermediate-boiling reactant. For a case with five reactive trays, Figure 6.11 shows that the reverse reaction dominates from tray 3 upward. Adding more trays does not help with the conversion. As opposed to the case of IK , LK + HK, both products in the HK , LK + IK case move in the same direction toward the top of the reactive distillation. High product concentrations promote the reverse reaction and lead to a net negative reaction in the reactive trays as shown in Figure 6.11. Additional reactive trays would keep the compositions at their chemical equilibrium values, which would not change from tray to tray. The temperature profile in Figure 6.12 demonstrates that there is very little change in temperature over

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