Countercurrent extraction with

The yield of furfural from xylose is improved by countercurrent extraction with tetraJin (Schoenemann, Proc. 2d Europ. Symp. Chem. React. Eng., Pergamon, 1961, p. 30). 

The buckets have perforated bottoms. As they start to descend, they are filled with fresh flaked material and sprayed with dilute intermediate extract. The solution percolates downward from bucket to bucket. As the travel turns upward, the buckets are subjected to countercurrent extraction with solution from fresh solvent that is charged about 1/3 the distance from the top. There is sufficient travel time for drainage before discharge of the spent flakes. 

Downstream processing After removing the mold mycelium, the penicillin is separated from the broth by means of a two-stage continuous countercurrent extraction with amyl or butyl acetate. 

Interaction of Density, Viscosity and Interfacial Tension in Countercurrent Extraction with Near-Critical Fluids... 

Salex A process for purifying sodium chloride. Continuous countercurrent extraction with brine removes the impurities without dissolving the salt. There are three variants SALEX-B, SALEX-C, AND SALEX-M. Developed by Krebs Swiss and first operated in 1982. 

Craig and collaborators have extensively supplemented countercurrent extraction with gel filtration (Hill and Konigsberg, 1960 Rasmussen and Craig, 1961). Occasionally the more laborious countercurrent extraction method can be replaced by Sephadex filtration (Rasmussen and Craig, 1962). 

The simplest extraction system is made up of three components the solute (material to be extracted) the carrier, or nonsolute portion of the feed and the solvent, which should have a low solubility in the carrier. Figure 14.1 illustrates a countercurrent extraction with a light-phase solvent. The diagram can be inverted for a heavy-phase solvent. 

When processing apples, the recovery of juice solids can also be achieved by continuous countercurrent extraction with water. These extraction systems were derived from the extraction of sugar beets in the sugar industry and they work either as hot or as cold extraction. 

Derivation The mold is grown in a nutrient solution such as com steep liquor, lactose, or dextrose. After several days of cultivation the mold excretes penicillin into its hquid culture medium. This hquid is then filtered off, and the penicillin extracted and purified by countercurrent extraction with amyl acetate, adsorption on carbon, or other methods. Different varieties of penicillin are produced biosynthetically by adding the proper precursors to the nutrient solution. 

Ssuss D, Brunner G. Countercurrent extraction with supercritical carbon dioxide behaviour of a complex natural mixture. Proceedings of the GVC-Fachaussschuss Hochdruckverfahrenstechnik-, 1999 189-192. 

Countercurrent extraction with feed at intermediate stage... 

FIGURE 7.3 8 Countercurrent extraction with reflux as in Fig. 7.3-7, showing location of A, and A2. 

A flow diagram for countercurrent extraction with reflux is shown in Fig. 20.14. To emphasize the analogy between this method and fractionation, it is assumed that the cascade is a plate column. Any other kind of cascade, however, may be used. The method requires that sufficient solvent be removed from the extract leaving the cascade to form a raffinate, part of which is returned to the cascade as reflux, the remainder being withdrawn from the plant as a product. Raffinate is withdrawn from the cascade as bottoms product, and fresh solvent is admitted directly to the bottom of the cascade. None of the bottom raffinate needs to be returned as reflux, for the number of stages required is the same whether or not any of the raffinate is recycled to the bottom of the cascade. The situation is not the same as in continuous distillation, in which part of the bottoms must be vaporized to supply heat to the column. 

Figure 7.18 Use of Janecke diagram with auxiliary distribution curve for countercurrent extraction with reflux.

Example 7.6 Countercurrent Extraction with Extract Reflux... 

A process which takes advantage of both the solubility characteristics and chemical properties of the amines is One which employs selective absorption in weakly acidic compounds such as cresols. Solubility is in- uenced not only by the solvent, but by the different basicities of the amines, as indicated under dissociation constants in Table 8-19. According to this process, mono- and dimethylamine are separated from trimethylamine by countercurrent extraction of the mixture with cresol saturated with water. The undissolved trimethylamine overhead is the least soluble In various solvents and is more weakly basic than dimethylamine. Prior to extraction, NHj can be removed, under specific conditions, from the three amines by countercurrent extraction with 17 per cent NaOH solution. This operation gives a mixed amine gas overhead and an NaOH solution of NHj. Under another set of conditions employing 10 per cent NaOH lolution in lower volumes, 100 per cent trimethylamine is the overhead gas. 

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