Rotating annulus column

Rotating annular column An implementation of preparative chromatography using a cylindrical, annular column rotating aroimd its axis. A continuous feed stream is injected at a fixed position just above the packing. Each component band follows a helical trajectory and is collected as a continuous stream along a fixed sector of the outlet annulus. 

In the first case, the sample is successively applied into a bundle of identical columns by means of a special multiport valve. In the second case, the gel is packed into a rotating annulus and sample is continuously applied at a fixed point. Both procedures are instrumentally fairly exacting and their separation power is rather low. It is expected that the continuous gel chromatography will be successfully applied in the industrial separations of simpler mixtures. 

In the rotary annular contactor [D2, L2, T2] shown schematically in Fig. 4.27 [T2], the organic and aqueous phases flow countercurrently by gravity in the annular space between a rotating itmer cylinder and a stationary outer cylinder. Taylor-instability vortices generated in the annulus promote dispersion and interfacial area. This is one of the simplest of the mechanically a tated contactors, and it has been developed for possible application to fuel reprocessing. In laboratory extractions of uranium from nitric add with TBP in kerosene, Davis [D2] obtained values as low as 7.5 cm for the column hei t equivalent to a theoretical stage. The rotor speed varied from 1200 to 2000 r/min, with annular widths of 0,1 to 0.35 cm and a stator diameter of 2.2 cm. The residence time per theoretical stage was 10 s or less. 

Unfortunately, since the preferred width of annulus is fairly constant for any diameter of column, the throughput of a rotary extractor is approximately proportional to its diameter, whereas that of other types is more nearly proportional to the square of the diameter. Consequently, the use of this type of extractor is limited to small-scale processes, and it has also been applied in a highly successful manner as an analytical tool, i.e. for the puri-flcation of continuous samples from process streams prior to analysis. The high precision engineering required for the construction of rotors capable of high-speed rotation also militates against their use on a larger production scale. 

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