ARD-extractor

Extraction can be performed in stirred tanks if the process proceeds fast and separation of phases is ea.sy, but column extractors are most commonly used. The column can be filled with a particulate material. The liquids flow countercurrently whereby the flow can be uniform or pulsed. Reciprocated and rotary agitators are often used to enhance mass transfer. An example of the latter type is shown in Fig. 7.2-13 (asymmetric rotating disk (ARD) extractor). 

A detailed design of an ARD extractor based on pilot plant work is presented by Misek and Marek (in Lo et al., 1983, pp. 407-417). The design and operating parameters of the ARD extractor are related to the vessel diameter D (mm) thus ... 

Countercurrent columns with additional kinetic energy input have found a broad range of industrial applications [42-48]. Examples of extraction towers with energy input are pulsed towers, pulsed packed columns and pulsed perforated-plate towers. A number of units with some form of mechanical agitation are also used (Karr column, Scheibel column, Oldshue-Rushton column, Ktihni column, RZE extractor, RDC and ARD extractor, Graesser contactor). 

Stagewise contact with controlled coalescence redispersion cycles Tray column Pulsed sieve column. Pulsed Mixer-Settler-cascade, Extraction tower with controlled cycle Scheibel column, ARD-Extractor, Leisibach column, Mixer-Settler cascade ... 

In an ARD-extractor the asymmetrical stator consists of trays and baffles to divide the column into extraction zones and linked transfer zones. On the rotor mixing discs are mounted. The extraction zone is limited by the stator partition and is separated by the trays into chambers. Phase transport and separation take place in the settling zone behind the partition. Compared to the RDC smaller throughput but better separation efficiency. 

---