Column trough distributor type

For single- or multiple-bed columns, a distributor is needed for each bed. A center-fed packed distillation column, for example, requires at least two beds. In some cases, the cost of the distrib-utor(s) can approach that of the packing. One can select from several different types of liquid distributors, including trough, orifice/riser, perforated pipe, and spray nozzle. These are illustrated in Figure 12.55 and described below. 

The quality of distribution provided by notched-trough distributors is generally somewhat inferior to that achievable by orifice-type distributors. With notched-trough distributors, it is generally difficult to incorporate more than three to four drip points per square foot of column cross-sectional area (111, 438). It may also be difficult to space these drip points evenly. If it is practical to provide a sufficient number of drip points per unit of column area, and to space them evenly, this distributor can provide a distribution as good as an orifice-type distributor. 

For large-diameter columns, the trough-type distributor shown in Figure 11.50 can be used, and will give good liquid distribution with a large free area for gas flow. 

Figure 1335. Packed column and internals, (a) Example packed column with a variety of internals [Chen, Chem. Eng. 40, (5 Mar. 1984)]. (b) Packing support and redistributor assembly, (c) Trough-type liquid distributor, (d) Perforated pipe distributor, (e) Rosette redistributor for small towers. (0 Hold-down plate, particularly for low density packing.

Weir distributors are usually of the weir riser type (Fig. 3.4g) or the notched-trough type (Fig. 3.4/). The former type is commonly used in small-diameter columns (<4 ft), while the latter is used in larger-diameter columns (>3 ft), but can also be used in smaller columns. 

---