Multistage continuous extraction

The centrifugal separator of the AKUEVE system is also used for phase separation in the SISAK technique [84]. SISAK is a multistage solvent extraction system that is used for studies of properties of short-lived radionuclides, e.g., the chemical properties of the heaviest elements, and solvent extraction behavior of compounds with exotic chemical states. In a typical SISAK experiment, Fig. 4.34, radionuclides are continuously transported from a production... 

Multistage Crosscurrent Extraction In multistage crosscurrent extraction, the raffinate is successively contacted with fresh solvent which can be done continuously or in batch (Figure 10.4). With the given flow rates of the feed and the solvent streams, the... 

Skarnemark, G., Andersson, S., Eberhardt, K. et al. 2005. A micro reactor for continuous multistage solvent extraction. ISEC 2005, Beijing, China, September 19-23. 

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. 

Continuous Extraction Versus Multistage Batch Extraction... 

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. 

Continuous Countercurrent Multistage Fractional Extraction. The industrial process utilizing the double-solvent principles is continuous and is carried out according to the flowsheet of Fig. 7.18 (2, 15). The feed, consisting principally of a mixture of B and C to be separated, is introduced into the central portion of a cascade of stages, 1 to 1. To facilitate... 

Figure 12.7-3. Method to perform overall material balance for Example 12.7-1. Sec. 12.7 Continuous Multistage Countercurrent Extraction...

Figure 8.1.37. (a) Continuous countercurrent multistage solvent extraction cascade of N stages (b) graphical determination of stage numbers in such a cascade of equilibrium extraction stages. 

Solids may be processed continuously or semicontinuously by pumping slurries or by using lock hoppers. An example is the separation of insoluble polymers by floatation with a variable-density SCF. For liquid feeds, multistage separation may be achieved by continuous counter-current extraction, much like conventional liquid-hquid extraction. The final produces may be recovered from the extract phase by a depressurization, a temperature change, or by conventional distillation. 

Multistage counter-current liquid-liquid extraction is a typical continuous process. Fig. 121 shows a schematic diagram of the process. The slope of the line depends on the volumetric ratio of the aqueous and organic phases. The aqueous and organic phases move through the system as two counter currents. The raffinate from a specific extraction stage moves on to the next stage, to be mixed with a relatively fresh portion of the extract, i.e. extractant that was previously mixed with a low-concentration aqueous solution. 

EQMULTI - Continuous Equilibrium Multistage Extraction System... 

As the potentialities of liquid extraction as a separation method were developed, the need for efficient, continuously operated, multistage equipment became apparent. It was natural therefore to turn to devices which had been so successful in other similar fluid-contacting operations, such as the bubble-tray tower and the packed tower of distillation. These devices have proved to be disappointing in liquid-extraction service, however for example, bubble-tray towers provide tray efficiencies in liquid-extraction operations of less than 5% (S7), and conventional packed towers show heights of transfer units of 10 to 20 ft. or more (T3). 

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