Multistage extraction apparatus

The multistage electrophoretic method has been developed by combining free electrophoresis and multistage extraction and is explored as an improved alternate method for the purification and concentration of cells or macromolecules. The present discussion is restricted to cells and particles. The present design is based on a derivative of the thin-layer multistage extractor design of Albertsson [70] and Treffrey et al. [71] and called ADvanced SEParation apparatus (ADSEP), designed by SHOT, Inc. [42]. 

A new apparatus was developed for continuous extraction of contaminated soil material for high pressure (25 MPa) and high temperature (663 K) operating conditions. The extraction of hydrocarbon contaminants from long weathered and highly contaminated soil material could be realised with supercritical water under parallel flow. Within a residence time of only 28 s suspensions of less than 0.75 wt% soil in water could be cleaned (> 90 %). For a concentration of 1 wt% soil in water 43 s were needed to achieve a clean-up result of 98.3 %. The continuous extraction process can be carried out multistage. Then higher concentrated suspensions (2-4 wt%) can be also cleaned by supercritical water extraction. 

From this knowledge, the idea of using a mixer-settler system for the extraction with supercritical fluids was derived. The purpose of this project is to build a multistage high pressure apparatus and to compare the separation efficiency and behaviour of the new system with that for a conventional column. 

Three steps required for multistage solvent extraction, i.e., phase mixing, phase settling, and transfer of the mobile phase, are defined clearly in the discontinuous countercurrent distribution process using the Craig apparatus. These basic requirements are essentially fulfilled by the use of a coiled tube in a continuous fashion. Solvent extraction using a coiled column is most efficiently performed with a horizontally laid coil that rotates about its own axis. In this horizontal coil orientation, the rotation induces the well known Archimedean screw force, which can be utilized for performing countercurrent solvent extraction. 

As with the gas-liquid operations, liquid extraction processes are carried out in slagewise equipment which can be arranged in multistage cascades and also in differential-contact apparatus. We shall consider the methods of calculation and the nature of the equipment and its characteristics separately for each type. 

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