Splash Baffles and Vapor Hoods

A splash baffle (Fig. 6.8a) is a flat vertical plate parallel to the outlet weir and located a short distance in front of the weir. The bottom edge 

Splash baffles are used in low-liquid-load services. The baffle backs liquid up onto the tray and increases its liquid holdup and froth height (31, 83, 374). The baffle also helps to prevent the tray from drying up and promotes froth regime operation at low liquid loads (374). In small-diameter columns ( 2 ft) it also prevents liquid drops formed at the tray inlet from being flung directly into the downcomer. 

A splash baffle is recommended when liquid flow rate is less than 0.1 gpm per inch of outlet weir (144). One successful application of tailor-designed sieve trays with splash baffles at liquid rates ranging from 0.01 to 0.07 gpm per inch of weir has been described (374). Splash baffles should only be used at low liquid loads, because they restrict the downcomer inlet area and can lead to premature downcomer choke. A calming zone upstream of the baffle is sometimes used to minimize this problem (374). Splash baffles also increase tray pressure drop and froth regime entrainment (31). 

The splash baffle should be tall enough to avoid liquid droplets from skipping over its top. To minimize effects of out-of-levelness and to ensure adequate head over the outlet weir, the outlet weir is usually notched with shallow notches (Sec. 6.7). 

The vapor hood is similar in function to the splash baffle (Fig. 6.86). A vapor hood is used with an envelope-t5q)e downcomer (see Fig. 6.14c and d in Sec. 6.15). The hood shelters the downcomer from the shower of drops on the tray and forces liquid buildup on the tray until it overflows the weir. Application and performance characteristics of the vapor hood are similar to those of the splash baffle, and, likewise, it is only suitable for very low liquid-flow-rate services. 

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Figure 6.8 Splash baffles and vapor hoods, (a) Splash baffles (6) vapor hoods.

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