Column and Tray Parameters

Structtiral details of a sieve tray distillation column (a) downcomer (b) tray support (c) sieve trays (d) manhole (e) outlet weir and (f) inlet weir. 

Liquid flow proceeds across a tray into a downcomer that has the cross section of circular segments and continues downward onto the next tray where it resumes its horizontal direction. Vapor moves upwards through perforations in the tray and is in crossflow with the liquid on it. A feature not always known is the provision of weirs at both the inlet and outlet to a tray. They serve to control the flow and height of liquid in the downcomer. Manholes are provided at intervals to allow internal inspection. (The uninitiated sometimes need to be reminded that it should not be sized for three-year-olds.) 

The detailed design of a tray is beyond the scope of this text. It involves the use of a host of semiempirical correlations and it is best to draw on information provided by vendors. The reader should, however, have a sense of scale of the parameters involved, which we attempted to provide in Table 7.4. The choice of tray is assisted by Table 7.5, which summarizes the principal features of the three major types. The scale of column dimensions is conveyed by Table 7.6. 

In the early years of tray development, bubble-cap trays predominated. Sieve trays were used much more sparingly because of their tendency to 

Mass Transfer and Separation Processes Principles and Applications 

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At this point most of the column and tray parameters have been tentatively deter-... 

At this point most of the column and tray parameters have been tentatively determined. Next, a performance check is carried out at various operating conditions to determine the operable ranges and whether any of the design parameters need to be adjusted. Performance checks include such items as pressure drop, liquid handhng capacity, entrainment, and weeping. 

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