Entrainment tray layout

Because of their simplicity and low cost, sieve (perforated) trays are now the most important of tray devices. In the design of sieve trays, the diameter of the tower must be chosen to accommodate the flow rates, the details of the tray layout must be selected, estimates must be made of the gas-pressure drop and approach to flooding, and assurance against excessive weeping and entrainment must be established. 

Spray regime operation is desirable (321) for negative-surface-tension systems (i.e., where the mixture s surface tension decreases from the top tray toward the bottom tray). Froth regime operation is desirable for positive-surface-tension systems (surface tension increases from the top tray down), and when liquid entrainment needs to be minimized (321). In most commercial applications, vapor and liquid loading requirements override these desirability considerations and dictate the tray flow regime. For optimum tray performance, the tray layout must therefore accommodate the expected flow regime. 

Determine the tray layout and pressure drops for the distillation column in Examples 10-1 and 10-2. Determine if entrainment or weeping is a problem. Determine if the downcomers will work properly. Do these calculations only at the top of the column. 

Capacity restriction mechanism(s). Column throughput is restricted by one of several different mechanisms. These include spray entrainment flooding, froth entrainment flooding, downcomer backup flooding, downcomer choke flooding, excessive entrainment and excessive pressure drop. Optimum tray and downcomer layouts vary with the mech-... 

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