Sieve Tray Column Interface Control

Control of the main liquid-liquid interface for a sieve tray column can be counterintuitive because of complexity caused by the presence of multiple interfaces within the column. For example, if the interface level is too high, the usual control response is to allow the heavy phase to flow out the bottom of the column for a time until the desired level is reached (using the scheme outlined in Fig. 15-61). Ideally, this should lower the interface level, as shown in Fig. I5-62a. This is a typical response for most differential contactors sucn as packed or spray columns. However, for the sieve tray column the initial response can actually be a rise in the interface level for a short time, as shown in Fig. 15-62. In some cases, this can result in entrainment of heavy phase out the top of the tower. 

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