Sieve trays with downcomers

Figure 8-118. Sieve tray with downcomers, tower assembly. Used by permission, Hendrick Mfg. Co.

Figure 8-124. Typical operating curve of sieve trays with downcomers. Note modes of operation used by permission, Chem. Eng., Chase, J. D., July 31 (1969), p. 105. Also see Klein [201], Figure 8-148.

Figure 8-130. Effective iiquid head for sieve trays with downcomers. Used by permission, Hughmark, G. A. and O Connell, H. E., The American Institute of Chemical Engineers, Chem. Eng. Prog. V. 53, (1957 ), p. 127M, all rights reserved.

This is the case with diameter determination. The relation of Equation 8-250 for the perforated tray or sieve tray with downcomers can be used for the plate without downcomers. Generally, the liquid level and foam-froth height will be higher on this tray, hence the ralue of h., clear liquid on the tray, may range from 1-in. to 6-in. depending on the service. 

Fig. 9.4 Sieve trays with downcomers for liquid systems with (a) high interfacial tension and dual-flow trays for liquid systems and (b) with low interfacial tension. In the case of downcomers, only the phase to be dispersed flows through the holes. The droplets are formed by jet disintegration. In dual-flow trays, both hquids flow through the same holes alternately. The larger drops spUt because of colhsion with the tray.

In systems with a low surface tension, the hole size of the sieve tray with downcomer should be smaller than 2 mm to prevent the continuous phase percolating through. For the treatment of such systems, dual flow trays without downcomers are more suitable. On a dual flow tray, the disperse and continuous phases flow in turn through the base plate holes and between the trays, producing strongly circulating convection cells. 

Fig. 6-33. a) Sieve tray with downcomer b) Dual-flow tray... 

Opening ratio 5 (sieve tray with downcomer)... 

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