Trough distributor

Figure 6. Orifice trough distributor with side-wall orifice, Model 137. (Courtesy of Norton Chemical Process Products Corporation.)...

Figure 9-8G. Koch/Sulzer trough distributor (MDP), for medium to large diameter columns for structured packing (patented), one of several designs available. Used by permission of Koch Engineering Co., Inc., Bull. KS-6.

With a trough distributor it is often more difficult to obtain uniform distribution next to the tower wall than with a PAN or orifice pipe distributor. Bonilla [131] recommends the rule of thumb Any 10% of the outer surface area of packing in the tower should not receive more or less liquid than the average 10% of the surface area. 

The use of V-notches in a trough wall for overflow is more sensitive to leveling problems than the other designs, and for the same %- to Me-in. level tolerance produces a more severe non-uniform flow distribution. The quality of distribution from a V-notch is poor compared to the other types of trough distributor, but does have advantages in slurry systems [131]. It should not be used for critical distillation applications, but is good for heat transfer and where solids are in the system. 

Notched trough distributors (Fig. 14-69g) consist of parallel troughs with side V notches. This distributor obeys the triangular notch equation instead of the orifice equation, which makes the flow proportional to h25 [instead of h05 in Eq. (14-163)]. This high power renders the distributor highly sensitive to out-of-levelness and... 

With any trough distributor, and especially those with V notches, excessive hydraulic gradients must be avoided. This is often achieved by using more parting boxes. 

Packed-tower efficiency and turndown are strongly dependent on the quality of initial liquid distribution. Uneven distribution may cause local variations in the liquid/gas ratio, localized pinch conditions, and reduced vapor-liquid contact. Figure 14 shows two common liquid distributor types, the ladder type (shown as the top distributor) and the orifice type (shown as the redistributor). The ladder type is a horizontal header of pipes, which are perforated on the underside. The orifice type is a flat perforated plate equipped with round or rectangular risers for gas passage. Other common types of distributors are a header equipped with spray nozzles (spray distributor) and a header of horizontal channels, with V notches cut in the vertical walls of the channels (notched-trough distributor). 

Liquid distributors function to spread an even distribution of liquid over the packing bed. Liquid distributors are commonly broken down by motive force into pressurized or gravity distributors. Pressurized distributors include pipe-oriflce distributors and spray distributors. Gravity distributors include pan-oriflce distributors and trough distributors. 

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