Our multistage LX centrifugal extractors are stage-wise contactors. We can assemble up to 7 stages in a single rotor for extremely high extraction efficiency in a very compact machine.

A feed solution, containing one or more solutes (shown in blue/green), and an immiscible solvent (shown in red) with a different density than that of the feed solution are fed to opposite ends of the multistage extractor. Each stage consists of a mixing chamber and a decantation chamber with interstage countercurrent liquid flow analogous to a pump-mix mixer-settler.

Each stage of the LX extractor includes:

• a mixing chamber where the two liquids are mixed by means of a stationary agitation disc (Item A) mounted on the central drum. The high relative speed between the stationary agitation disc and the rotating walls of the mixing chamber create an extremely fine dispersion. The agitation disc and the mixing chamber's inlet and outlet channels form a pump which draws the two phases from the adjacent stages and also transfers the dispersion to the settling chamber.
• a settling chamber in which the liquids are separated by the centrifugal force generated by the rotating bowl. The heavier liquid (shown in blue/green) occupies the outer portion of the bowl. The light liquid (shown in red) occupies the inner portion of the bowl.

Due to the large interfacial area created by the intense mixing, and thanks to the efficient centrifugal phase separation, the extraction efficiency is very high. Each mechanical stage nearly corresponds to a theoretical stage.

The liquids are discharged from the LX extractors by gravity or by centripetal turbines.

For pilot plant duty and process development, we recommend the LX 204 which is a 4-stage centrifugal extractor with intermediate inlets at Stage #2 and Stage #3. It may therefore be operated as a 1-, 2-, 3-, or 4-stage extractor to rapidly assess the improvement in extraction efficiency as a function of the number of stages.

The multiple inlets accommodate a wide variety of flow configurations and extraction processes by introducing a third liquid that is miscible with one of the two liquid phases in the extractor. This is useful to change pH or ionic strength along the extraction profile or to scrub (wash) the extract prior to its discharge from the extractor (refer to Flow Sheets C & D above).

The intermediate inlets can also be used for a fractional extraction whereby the feed solution is introduced in Stages #2 or #3, with the two solvents being introduced at Stages #1 and #4. The LX 204 is therefore an extremely versatile process development tool.

A few of the different processing arrangements that can be achieved in the LX 204 are shown below:

Flow Diagram A: Illustrates normal operation as a 4-stage countercurrent extractor.

Flow Diagram B: Illustrates operation as a 2-stage countercurrent extractor by introducing the light phase into Stage #3. Note that if the light phase were introduced into Stage #2, three countercurrent extraction stages would be obtained.

Flow Diagram C: Illustrates contact between two miscible heavy phases and one light phase; for example three extraction stages plus one scrubbing stage (or other combinations).

Flow Diagram D: Illustrates contact between one heavy phase and two miscible light phases; for example three extraction stages plus one stage of heavy phase washing with a diluent (or other combinations).