Graesser contactor

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). 

Finally, the Graesser contactor deserves mentioning. It employs a horizontal format where a series of discs is mounted on a central shaft, with C-shaped buckets mounted between the discs (Fig. 2.22). There is a peripheral gap between the discs and the interior of the shell and longitudinal flow of the phases is through this gap. The heavy phase outlet level is adjusted in such a way that it results in an interface level approximately on the centreline of the unit. In operation, the rotor assembly is slowly rotated and each phase is dispersed, in turn, in the other. The design is virtually unique in not having one phase dispersed and the other continuous throughout. 

The Graesser contactor, also shown in Fig. 6.3-3, has some industrial importance for processing systems with very low interfacial tensions. The agitating elements (half pipes) rotate arotmd a horizontal axis. During upward motion the elements transport some heavy Uquid upward and disperse it into the light phase. After being... 

The Graesser contactor takes an extreme position in the diagram. It has the highest separation efficiency (10 stages per meter) but the lowest capacity (1-2 m/h). The other extremum takes the static sieve tray extractor with only one equilibrium stage per meter and up to 50 m/h capacity. The capacity of a pulsed sieve tray column is as high as 30 m/h with a separation efficiency of 5 to 6 stages per meter. 

Extraction apparatus with continuous phase contact Spray column Packed column Pulsed packed column Rotating disc contactor, Oldshue-Rushton column, Graesser-Contactor, Kuhni column Podbiehiiak- Extractor, Luigi-Westfalia- Extractor, De Laval-Extractor... 

The Graesser contactor consists of [6.64] a horizontal column divided into in- [6.68] dividual chambers by partions and a rotor with circulating dipping tubes. 

Phases to be contacted flow counter-currently through the column. Phase mixing occurs in the chambers. Via a gap between the circulating partitions and the column shell the mixture is passed from chamber to chamber. Due to gentle phase mixing the Graesser contactor is especially suitable for systems which form emulsions that are difficult to separate. 

Mechanical agitation Group E Rotating disc contactor Oldshue-Rushton column Zeihl column Graesser contractor Group F Scheibel column Mixer-settlers... 

Kuhni column Graesser raining-bucket contactor... 

The RTL contactor, formerly known as the Graesser raining bucket contractor (Fig. 14), is a horizontal design with the phases interdispersed by water wheel arrangements. The unit has the unusual feature of dispersing each phase into the other. The contactor was developed for... 

FIGURE 14 Graesser raining-bucket contactor. [Reprinted by permission of Chem. Eng. 75(18), 76 (1968).]... 

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