Extraction, advantages continuous countercurrent

Continuous glycerin washing of soap produced by saponification has been demonstrated in a countercurrent centrifugal extractor (38). The device achieves phase separation with as little as 0.02 specific gravity difference and accomplishes up to 10 theoretical stages of extraction. Some of the advantages over prior operations reportedly include flexibility in feed, low holdup, less waste due to more efficient separation, simple operation, rapid startup, and small space requirements. 

For process engineering applications, the particle extraction process is developed as a continuous operation. This means that both phases are in circulation and that within the column a countercurrent flow occurs, such that the product (i.e. organosol) and the waste (i.e. the particle-free used aqueous phase) can be produced continuously into separate tanks, as already presented in Fig. 16b. Therefore, ricinoleic acid is used as a surfactant due to its advantageous process behavior and short processing times. As shown in Fig. 20a, transferred magnetite yields of about 90 % are achieved with a stable process behavior. 

---