Kennedy extractors

The Kennedy extractor (Fig. 18-87), also requiring little head-room, operates substantially as a percolator that moves the bed of solids through the solvent rather than the conventional opposite. It comprises a nearly horizontal line of chambers through each of which in succession the solids being leached are moved by a slow impeller enclosed in that section. There is an opportunity for drainage between stages when the impeller lifts sohds above the liquid level before dumping them into the next chamber. Solvent flows countercur-rently from chamber to chamber. Because the solids are subjected to mechanical action somewhat more intense than in other types of... 

In contrast to the previously described modes of operation, solvent and feed move continuously towards each other in absolute countercurrent extraction. These extractors, e.g. the screw-conveyor extractor, the Bonotto extractor, the Kennedy extractor and extraction batteries with decanter, all move the solid material and are, therefore, mechanically stress objected. For the miscella this requires extended filtration for removing solids. 

Washing and adsorption The belt filters are used for washing and dewatering of fine solids in the manufacture of catalysts, zeolites, alumina and other crystalline substances, and so on. The belt filter requires the associated equipment — several vacuum pumps and separation drums. Through-circulation tray driers and through-circulation rotary driers are used to dry solids. All these are continuous crosscurrent processes. These could be replaced with a moving-bed, Hildebrand (screw) conveyer or Kennedy extractor [18], each of which is a countercurrent process. Their potential for PI has not been explored. 

The Kennedy extractor [38], a modem arrangement of which is indicated schematically in Fig. 13.19, is another stagewise device which has been in use since 1927, originally for leaching tannins from tanbark. It is now used for oilseed and other chemical leaching operations. The solids are leached in a series... 

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