The base case location of the fresh feed of reactant A is on tray 6 because there are five stripping trays. Figures 2.17-2.19 show the effect of moving the feed tray up into the reactive zone. The upper left graph in Figure 2.17 demonstrates that there is an initial decrease in the vapor boilup required to achieve the specified 95% conversion and impurities. Thus, the optimum feed tray location in this example is not at the very bottom of the reactive zone.
The lower graphs in Figure 2.17 show that the concentration of impurity A in the distillate increases as the feed tray is moved up in the column and the concentration of B increases in the bottoms. This seems reasonable because the A is being introduced closer to the top and further away from the bottom. Figure 2.18 gives the temperature profiles for different values of NFa. The temperatures in the stripping section increase and the temperatures in the rectifying section decrease as the feed tray is moved up the column. Because
Figure 2.17 Effect of location of fresh feed of A.
A is lighter than B, the lower concentrations of A in the stripping section result in higher temperatures. The reverse is true in the rectifying section. The composition profiles throughout the column are provided in Figure 2.19.
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