Half-periodic process of the multistage cyclic countercurrent extraction

The processes of countercurrent multistage extraction has been analyzed. A half-periodic method has been proposed for performing these processes in the cascade of novel mixer-settlers, in which periodic mixing and phase separation occurs sequentially in the same chamber. In the cascade of these apparatus, each cycle of the extraction process consists of two half-periods: (1) a half-period of the heavy-phase flow movement through the cascade and (2) a half-period of the light-phase flow movement through the cascade. The half-period of the flow movements of each phase comprises several stages. At each of these stages, three operations are performed sequentially: the supply of a portion of the respective phase, which has a volume equal to that in a single apparatus, the cascade, and its movement through it while the mixers are off; intensive contact between the phases while the mixers are on; phase separation while the mixers are off. The half-periodic mode allows one to perform extraction processes at a higher mass-transfer rate and a lower (compared to the conventional countercurrent mode) degree of longitudinal mixing, which significantly improves the effectiveness of these processes.