Sieve tray design hole pitch

Sieve Tray Design Perforations usually are in the range of 0.125 to 0.25 in (0.32 to 0.64 cm) in diameter, set 0.5 to 0.75 in (1.27 to 1.81 cm) apart, on square or triangular pitch. There appears to be relatively little effect of hole size on the mass-transfer rate, except that with systems of high interfacial tension, smaller holes will produce somewhat better mass transfer. The entire hole area is normally set at 15 to 25 percent of the column cross section, although adjustments may be needed. The velocity through the holes should be such that drops do not form slowly at the holes, but rather the... 

Reference A3 (Figure 11.28) details the recommended plate configuration for liquid flowrate versus column internal diameter. A reverse flow-type sieve plate is suggested as shown in Figure 9.3. The pitch of the sieve-tray holes is selected so that the total hole area is reduced to 0.07 times the total column area. The other design criteria employed to provide the provisional plate specification are detailed in Table G,3. 

The perforations in sieve trays are seldom less than of an inch in diameter and they are located on equilateral triangles such that the pitch to diameter ratio is greater than 2 but less than 5 with an optimum of about 3.8. The trays are generally designed with tray thickness to hole diameter of 0.1 to 0.7. 

Design a sieve-tray column for the ethanol absorber of Example 4.4. For alcohol absorbers, Kister (1992) recommends a foaming factor Ff = 0.9. The liquid surface tension is estimated as a = 70 dyn/cm. Take do- 5 mm on an equilateral-triangular pitch 15 mm between hole centers, punched in stainless steel sheet metal 2 mm thick. Design for an 80% approach to the flood velocity. 

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