Liquid-Liquid-Extraction


Liquid-liquid-extraction, also called solvent extraction, is a separation technique that is based on different solubility of a material in two insoluble phases (e.g. benzine/water). One of the two phases is aqueous in most instances.


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Liquid-liquid-extraction is advantageous for processing large volumes of 100,000 m/h and more within reasonable apparatus dimensions.
The actual extraction process hardly needs any energy, but the subsequent regeneration stage (in most cases a rectification stage) needs a corresponding energy consumption for the recycling of the extraction agent.
The accumulated raffinate phase frequently needs to be fed to a secondary treatment.
The choice of the adequate extraction agent is thus made not only according to the extraction selectivity but also according to technically easiest and energetically most economic regenerative options.


Advantages

  • Very large capacities possible with a minimum of energy consumption
  • Selectivity, when other standard separation methods fail or require expensive equipment or energy cost
  • Heat sensitive products are processed at ambient or moderate temperatures (example: vitamin production)
  • Separation of small contents of high-boiling impurities, mostly in aqueous solutions.

Agitated Extraction Columns

As no other type, the agitated extraction column is universally suitable for practically all kinds of extracting applications. Limiting condition is a minimal density difference of 0.05 kg/m between both phases and a not too strong tendency to form a stable emulsion, in order to allow a smooth agitation.

Advantages


  • Adaptation of the compartment and agitator geometry to the specific product and the operational process conditions
  • The optimel droplet size can be adjusted by variation of the agitator speed
  • Insensitive to solids
  • mechanically simple construction together with extremely small agitator speed 

Extraction columns AMEX 110-24 at Litwin