Another type of gravity-flow, vertical contactor with a rotating axial shaft is the rotating disk contactor developed by the Shell Development Company [Rl, R2], shown schematically in Fig. 4.28. It consists of alternate annular stator disks attached to the outer shell and circular rotor disks attached to the rotating shaft. Rotation of the central shaft, at peripheral speeds up to 6 m/s, provides controlled dispersion of the two phases and sets up a toroidal flow pattern within each stator compartment. There are no settling chambers, and the two phases drift past each other in countercurrent flow.

Dimensions of contactors for which test data are available [R2] are given in Table 4.15.

When the 20-cm-diameter column was tested in hexone-acetic acid-water, a height equivalent to a theoretical stage as low as 10 cm was observed, with a combined flow rate of both phases of 1.0 cm3 /(s-cm2) of column cross-sectional area. The holdup time per equivalent theoretical stage is only 10 cm т 1 cm/s = 10 s.

The rotating disk contactor has had extensive application in petroleum refining and organic chemical separations. A modified version, with holes in the horizontal stator disks to promote countercurrent flow, has been used in the recovery of uranium from solutions used in cleaning process equipment [D4, L2].