Flooded column collapses

A Flooded Column Collapses as Water Is Being Drained from the System... 

A flooded column collapses as water is being drained from the system... 

Fig. 2-4. Examples of typical scan profiles obtained for various problems met on distillation columns, respectively from up and left to bottom and right normal column, collapsed tray, flooding, entrainment, weeping and foaming (IAEA, 2002).

Drainage can be troublesome when the bottom trays are flooded (i.e., covered with liquid), emd the rate of liquid withdrawal fiwm the column exceeds the rate of liquid downflow through the trays and downcomers (61,192,207,356). Under such conditions, a vapor gap may form below the bottom tray. The presence of this gap leaves the bottom tray with the task of supporting all the liquid above it, and may lead to failure of the bottom tray. Once the bottom tray fails and the liquid drains from it, the vapor gap moves to the space below the next higher tray. This tray may fail as well, and a cascade of collapsing trays may ascend the column (Fig. 12.8). 

If the liquid layer is deep (i.e., several of the lower trays may be flooded), vapor may travel through the liquid in the form of slugs. These can loosen bolting and other fasteners, damage trays, or lift trays off their supports (61,150a, 192, 207, 295), collapse packing supports (237), and cause column vibration and structural damage. 

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