Prediction by Data Interpolation

Vital et al. (131) present an extensive tabulation of tray efficiency data collected from the published literature. Data interpolation is one of the more reliable methods for obtaining tray efficiency, provided the data are good and the rules recommended for data scale-up (Secs. 

Alternatively, Fig. 7.5o gives oc 70 percent, which agrees well with Lockett s equation form. 

Allowing for a 10 percent error, an efficiency of 62 percent will he appropriate for design purposes. This can also be seen from Pig. 7.6a. The number of trays is therefore 18 stages/0.62 = 29 trays. In the rectifying section, there will be 29 X Vi = 11, while in the stripping section there will be 29 x Vie = 18 trays. 

It is worth it to compare this design efficiency against data listed in the Vital et al. tabulation (131). The tabulation contains no data for depropanizers, but there are data for two related systems a 4.7-ft ID, 264-psia stabilizer ( mv = 100 percent) and a propane-butane separation (Eqq = 100 percent). The data suggest that the depropanizer design efficient msfy be conservative. However, the data are too few and do not simulate the depropanizer closely enou to provide an adequate basis for designing for higher efficiency. 

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