In tray towers

TABLE 14-9 Relative Fabricated Cost for Metals Used in Tray-tower Construction ... 

To allow for the vertical height required for packed tower distributors and redistributors—and in tray towers the vertical height used by additional trays—typically using 10%-20% of the vertical packed height (10% for 2-in. random packing and 20% for structured packing) [136] the analysis indicated ... 

The notch or weir, in which the fluid flows over the weir so that its kinetic energy is measured by determining the head of the fluid flowing above the weir. This instrument is used in open-channel flow and extensively in tray towers 3 where the height of the weir is adjusted to provide the necessary liquid depth for a given flow. 

Figure 1332. Internals and mode of action of trays in tray towers, (a) Some kinds of bubblecaps (Glitsch). (b) Two kinds of valves for trays, (c) Vapor directing slot on a Linde sieve tray [Jones and Jones, Chem. Eng. Prog. 71, 66 (1975)]. (d) Vapor flow through a bubblecap. (e) Sieve tray phenomena and pressure relations hh is the head in the downcomer, h, is the equivalent head of clear liquid on the tray, hf is the visible height of froth on the tray, and h, is the pressure drop across the tray (Bolles, in Smith, 1963). (f) Assembly of and action of vapor and liquid on a bubblecap tray.

Relative fabricated cost for metals used in tray-tower construction... 

Absorption and stripping are usually conducted in packed columns or in trayed towers. Packed columns are preferred when (1) the required column diameter is less than 60 cm (2) the pressure drop must be low, as for a vacuum service (3) corrosion considerations favor the use of ceramic or polymeric materials and/or (4) low liquid holdup is desirable. Trayed towers are preferred when (1) the liquid/gas ratio is very low, and (2) frequent cleaning is required. If there is no overriding consideration, cost is the major factor to be taken into account when choosing between packed columns and trayed towers for absorption or stripping. 

Understand the fundamentals of the McCabe-Thiele graphical method to analyze binary distillation in trayed towers. 

In tray towers, entrainment of liquid in the gas is a form of back mixing, and there are back mbcing and axial mixing on the trays, which we have already considered. In sparged vessels, the liquid is essentially completely back-mixed to a uniform solute concentration. Both phases are largely completely mixed in mechanically agitated vessels. 

Liquid/gas ratio. Very low values of this ratio are best handled in tray towers. High values are best handled in packed towers. 

A chemical reaction of the solute with a conmonent in the liquid phase has the effect of increasing the liquid-fihn absorption coefficient over what would be observed with single physical absorption. 11115 results in an increase in the overall absorption coefficient in packed towers or an increase in tray efficiency in tray towers. 

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