Column internals Packed Tower

However, in certain cases, the impingement plate design is preferred over packed-tower columns when either internal cooling is desired, or where low liquid flow rates would inadequately wet the packing. 

The very first continuous distillation column was the patent still used to produce Scotch whiskey in the 1830s. It had 12 bubble-cap trays with weirs, downcomers, tray decks, and bubble caps with internal risers. Current trayed towers are quite similar. As most distillation towers have always been trayed rather than packed, one would have to conclude that trayed towers must have some sort of inherent advantage over packed towers. And this is indeed true, in a practical sense even though, in theory, a packed tower has greater capacity and superior separation efficiency than a trayed column. 

An extractor column is generally a tall, vertical packed tower that has two or more bed sections. Each packed bed section is typically limited to no more than 8 ft tall, making the overall tower height about 40 to 80 ft. Tower diameter depends fully upon liquid rates, but is usually in the range of 2 to 6 ft. Liquid-liquid extractors may also have tray-type column internals, usually composed of sieve-type trays without downcomers. These tray-type columns are similar to duoflow-type vapor-liquid separation, but here serve as contact surface area for two separate liquid phases. The packed-type internals are more common by far and are the type of extractor medium considered the standard. Any deviation from packed-type columns is compared to packing. 

Adsorbers, distillation colunms, and packed towers are more complicated vessels and as a result, the potential e. ists for more serious liazards. These vessels are subject to tlie same potential hazards discussed previously in relation to leaks, corrosion, and stress. However, tiicse separation columns contain a wide variety of internals or separation devices. Adsorbers or strippers usually contain packing, packing supports, liquid disuibutors, hold-down plates, and weirs. Depending on tlie physical and chemical properties of tlie fluids being passed tluougli tlie tower, potential liazards may result if incompatible materials are used for tlie internals. Reactivity with tlie metals used may cause undesirable reactions, which may lead to elevated temperatures and pressures and, ultimately, to vessel rupture. Distillation colunms may contain internals such as sieve trays, bubble caps, and valve plates, wliich are also in contact with tlie... 

AC Absorption column. Internals may include dispersing systems, packings, filling materials or operate as spray tower. 

From a process standpoint, the most important column internals are the liquid distributors. A liquid distributor is required at all locations in the tower where an external liquid stream is introduced. In addition to providing a uniform liquid distribution pattern to the top of the packed bed, the distributor also must provide sufficient gas passage area to avoid a high pressure drop or liquid entrainment. The liquid distributor should have a flow range suitable for the application and be resistant to fouling. 

TOWER INTERNAL SPECIFICATIONS SPRAY OR PACKED TYPE COLUMNS... 

Figure 9-74B. Tower internal specifications, Spray or Packed Columns.

Gasoline and kerosene rerunning was accomplished primarily in horizontal batch shell stills heated by direct firing or internal steam coils and surmounted by a vertical rectification column with partial condensers to supply reflux. The rectifying column in some installations was packed with iron rings, pipe fittings, earthware crocks, tin cans, or any suitable material readily available. In other units a fairly common type of column was the Heckmann bubble cap tower. 

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.

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