On the selection of the dispersed phase and continuous phase in the extraction column
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In an extraction column, when deciding whether the dispersed phase and the continuous phase should be the extract phase or the raffinate phase, how is this decision made? Based on which physical properties? Thank you!
In a sieve plate extractor, it is generally necessary to choose the stream with the higher volumetric flow rate as the dispersed phase, based on the magnitudes of the volumetric flow rates of the process feed and the lean solvent feed; this allows for a larger interphase contact area after dispersion through the sieve pores, thereby improving the extraction efficiency. At the same time, if the light phase is the continuous phase, a lift pipe should be designed accordingly ； If the heavy phase is the continuous phase, a downcomer is designed accordingly.
In my view, the dispersed phase and the continuous phase are separated by the phase interface within the tower; the lighter phase constitutes the continuous phase at the upper part, while the heavier phase constitutes the continuous phase at the lower part. This helps to reduce entrainment during discharging.