n x HETP
Comment. The calculations show that the current design is adequate. Flooding calculations performed using different correlations gave very similar answers. The column is lightly loaded in the top section. It may be tempting to go to an even smaller (1-in) packing in the top section, and save more vertical height. However, such a move is likely to further increase the column to packing diameter ratio to about 75, making the column more sensitive to maldistribution. The author would therefore feel uncomfortable with a further reduction of packing diameter in the top section.
9.4.5 Column sizing example: design checks
The design checks that will be performed in this example are MOC, pressure drop, efficiency data, and minimum wetting. Other checks that are often performed are loading point, liquid holdup, and efficiency from a theoretical correlation. The author excluded these checks because he expects them to serve little purpose in this example. The uncertainty involved in defining and predicting the load point argues against basing a design on this parameter. Liquid holdup is seldom a concern with high-pressure systems. Finally, as was previ ously stated (Sec. 9.1.5), theoretical methods of predicting packing efficient compare unfavorably with the empirical rule of thumb used here (Sec. 9.4.4). Further, high pressure is outside the range of application of most, if not all, the popular theoretical methods (e.g., Table 9.1).
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