Redistributor support

The redistributor must be compatible with the bed support above. It is best to have the manufacturer specify both. Often, the manufacturer supplies a package redistributor-support plate combination. 

A combination redistributor-support plate which can also achieve good liquid mixing (212) is the support mixer redistributor (Fig. 

Liquid distributors, liquid redistributors, supports made from metals and plastics. 

As indicated above, packed column internals include hqiiid distributors, packing support plates, redistributors (as needed), and holddown plates (to prevent movement of packing under flow conditions). Costs of these internals for columns with random packing are given in Fig. 14-80, based on early 1976 prices, and a Marshall and Swift cost index of 460. 

FIG. 14-80 Cost of internal devices for columns containing dumped packings, a) Holddown plates and support plates, (h) Redistributors, (c) Liquid distributors. [Pikulik and Diaz, Cbem. Eng., 84(21), 106 (Oct. 10, 1977).]... 

Allow 2 ft space between support of top section and redistributor of section 2 (from top). 

Select and design the column internal features packing support, liquid distributor, redistributors. 

A full redistributor combines the functions of a packing support and a liquid distributor a typical design is shown in Figure 11.52. 

Depth of packing without intermediate supports is limited by its deformability metal construction is limited to depths of 20-25 ft, and plastic to 10-15 ft. Intermediate supports and liquid redistributors are supplied for deeper beds and at sidestream withdrawal or feed points. Liquid redistributors usually are needed every 2 -3 tower diameters for Raschig rings and every 5-10 diameters for pall rings, but at least every 20 ft. 

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.

No. of trays Tray spacing in Packed height, ft Allowance for distributor, ft Allowance fer redistributor, ft Allowance for support or holddown, ft Total height, ft Middle section [between top and bottom)... 

Holddown plates and support plates, h) Redistributors. [PikuUk and Diaz, Tower wall thickness, mm... 

When faced with a packed tower, always keep in mind that packing involves an entire system, not just some mass-transfer surface. Packed towers include packing supports, packing, packing hold-down, feed distributors, internal redistributors, and other equipment. Fig. 1 shows a generic packed tower system. 

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