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Unformatted text preview: mn = Nt = 8.2 + the partial reboiler. The column contains 12 plates + the partial reboiler. From Eq. (6-21), the overall plate efficiency is,
Eo = Nt /Na = 8.2/12 = 0.68 or 68%. The column contains 5 plates in the rectifying section. This is equivalent to a plate efficiency in that section of 4.2/5 = 0.84 or 84%. The stripping section contains 6 plates plus the feed plate. Analysis: (a) (continued) Exercise 7.41 (continued) Therefore, the efficiency in this section is 4/7 = 0.57 or 57%. Note these results are subject to degree of curvature of the operating lines and the placement of the feed in the McCabe-Thiele method. In the McCabe-Thiele method, if one more equilibrium stage is added to the stripping section, so as to give 5 stages plus the partial reboiler, then the rectifying section only needs 3.8 equilibrium stages. Then the overall plate efficiency is 73%, with 71% in the stripping section and 76% in the rectifying section. This still does not account for the effect of curvature of the operating lines. Analysis: (a) (c...
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