Countercurrent stagewise extraction

The full model is described in Section 3.3.1.5 and consists of a countercurrent stagewise extraction cascade with backmixing in both phases. 

Consider the countercurrent extraction of solute A from solution in B using pure solvent C. The operatioo is performed in the column shown in Fig. 7.3-1, which may be either continuous-contact (packed) or stagewise. 

Caustic Washing. A flowsheet of the type of Fig. 11.3 may be used, involving stagewise contacting. In the first extractor H2S is removed by a prewash of caustic, as outlined above. The next three stages are used for countercurrent extraction of the mercaptans from the gasoline with aqueous sodium hydroxide, and the treated gasoline is water-washed to remove... 

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