Simple stirred mixer-settler

The type of stirrer used in a simple stirred mixer-settler is relatively unimportant provided it mixes the two phases adequately. It is clearly not necessary for it to have any pumping action. Neither is it essential for any individual stirrer to be operable at any particular time, since the effect of a breakdown in a single stage is merely to lose the extraction effect of that stage. An interface will form in the faulty mixing chamber at the level of the mixed phase port and both phases will take their normal paths, except without mixing. 

It is envisaged that this process could be operated with the simple type of mechanically stirred mixer-settler which is satisfactory in the Springfields uranium purification process. The Femald type of sieve-plate pulse column is another alternative. 

The types of equipment used, which range from stirred tanks and mixer-settlers to centrifugal contactors and various types of columns, affect both capital and operating costs [9]. In the decision to build a plant, the choice of the most suitable contactor for the specific situation is most important. In some systems, because of the chemistry and mass transfer rates involved, several alternative designs of contacting equipment are available. In the selection of a contactor, one must consider the capacity and stage requirements solvent type and residence time phase flow ratio physical properties direction of mass transfer phase dispersion and coalescence holdup kinetics equilibrium presence of solids overall performance and maintenance as a function of contactor complexity. This may appear very complicated, but with some experience, the choice is relatively simple. 

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