Bubblecap trays

Comparison of Diameters of Sieve, Valve, and Bubblecap Trays for the Same Service 

A C3 splitter has 24 in. tray spacing and will operate at 80% of flooding. These data are applicable  

The correlations for sieve and bubblecap trays have no provision for multipass flow of liquid. Their basic data may have been obtained on smaller towers with liquid flow equivdent to two-pass arrangement in towers 8 ft dia. The sieve tray correlation should be adapted to multipass flow by comparison with results obtained by tbe valve tray conelation in specific cases. 

Nonfoaming, regular systems Fluorine systems, e.g., BF, Freon Moderate foaming, e.g., oil absorbers, amine and glycol regenerators 

The allowable vapor velocity and the corresponding tray diameter are represented by the work of Soudeis and Brown, which is cited in standard textbooks, for example Treybal (1980). Its equivalent is the Jersey Critical formula. 

12) DIVIDE LIQUID FLOW RATE BY 2 -- 13) OBTAIN DIAMETER FROM TWO-PASS TRAY LINE 

The correlations for sieve and bubblecap trays have no provision for multipass flow of liquid. Their basic data may have been obtained on smaller towers with liquid flow equivalent to 

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Bubblecap trays are used only when a liquid ievei must be maintained at iow turndown ratio they can be designed for lower pressure drop than either sieve or valve trays. 

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.

A factor that is of concern with bubblecap trays is the development of a liquid gradient from inlet to outlet which results in corresponding variation in vapor flow across the cross section and usually to degradation of the efficiency. With other kinds of trays this effect rarely is serious. Data and procedures for analysis of this behavior are summarized by Bolles (in Smith, 1963, Chap. 14). There also are formulas and a numerical example of the design of all features of bubblecap trays. Although, as mentioned, new installations of such trays are infrequent, many older ones still are in operation and may need to be studied for changed conditions. 

Bubblecap trays, 428,430-433 allowable vapor rate, 432 comparisons with other kinds, example,... 

The allowable vapor velocity for bubblecap trays is about the same as for sieve trays, and Figure 13.32(b) may be used. The most complete published source of design and performance prediction of these trays is given by W. L. Bolles (in Smith, 1963). 

The calculated point efficiency must be converted to overall column efficiency, which will lower its value and make it closer to the O Connell prediction. The calculated value of Eog is slightly higher than obtained experimentally (Eog = 0.83-0.92) at the University of Delaware for bubblecap trays (Annual Progress Report of Research Committee, Tray Efficiencies in Distillation Columns, AIChE, New York, 1955). 

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