Column internals liquid collector

The multiple phase contact inside the column is promoted by internal mass transfer equipment. Three groups of mass transfer equipment are commonly differentiated, which are separation trays, random packings and structured packings. Besides mass transfer equipment, further column internals are required in rectification to ensure the proper operation of the mass transfer equipment. Such internals may include support and hold-down plates, liquid distributors and redistributors, vapour distributor devices, gas-liquid phase separators and liquid collectors that usually do not participate on mass transfer. 

Figure 8.4 draws attention to the principal internal components of a packed column. The parhcular packing shown is of the structural type displayed in Figure 5.5b. They allow the column diameter, which in distillahon is usually confined to 1 m or less, to exceed that limit many times. Liquid collectors and distributors, which are shown only twice, are usually used every 3 m to coxmteract channeling. This undesirable effect can be particularly severe at low liquid flow rates (vacuum operation).

For columns in which there is a substantial flash of the feed liquid, or in which the feed is a vapor of a different composition than the internal vapor, a collector plate can be installed above the feed point. The purpose of this plate is to provide mixing of the vapor phase in the gas risers so that a more uniform vapor composition enters the rectifying section of the column. 

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