Separator continuous counter-current

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. 

Paprika can be extracted to recover carotenoids, not only with CO2 but also with other gases. For example, by using ethane or ethylene, better results were obtained for the yield, extraction time, and quality of product. The solubilities of carotenoids are better in these gases, which is why the consumption of solvent and the extraction time were reduced. Practically water-free dye-concentrate was recovered by supercritical fluid ethane (under the conditions extraction 250 bar, 45°C separation 46 bar, 45 °C). The separation of pungent substances (capsaicinoids, free fatty acids) from the pigments can be carried out effectively in a continuous, counter-current extraction column with a large number of theoretical plates. 

Problem. Consider the same separation as previously, where a hydrocarbon gas stream is to be purified by continuous counter-current contact with a liquid organic solvent in an absorption column. The inlet gas contains 1.5% by volume of toxic DMSO of which 95% is to be removed. The gas flows at a rate of G = 0.1 kmol s 1 on a DMSO-free basis. 

In contrast to the case of HMPC, most lipases hydrolyze the racemic acetate of CPBA 9 to give a mixture of the insecticidally active (S)-CPBA 2 and the (R)-acetate 1J). Thus, the desired (S)-CPBA J2 could be separated from the (R)-acetate 10 by means of a continuous counter-current extraction using n-heptane solvent at 80°C. However, it is important to utilize the recovered (R)-acetate W for an efficient process. Fortunately, since the proton of the asymmetric carbon of the cyanohydrin acetate is labile, the antipodal (R)-acetate is easily racemized by treatment with weak organic base such as triethylamine without any side reactions. The racemized acetate J9 thus obtained was recycled as shown in Figure 6. Therefore, all of the racemic acetate 9 was converted to the desired (S)-CPBA 2 in this recycling process. The (S)-CPBA 2 obtained was esterified with (S)-2-(4-chlorophenyl)-3-methylbutyryl chloride to produce the most insecticidally active stereoisomer V2 of fenvalerate, namely esfenvalerate. The relative biocidal activities between... 

In practice fliis process is run using an aulomaled continuous counter-current circuit in which the organic solvent flows in fhe opposite direction to the aqueous layer containing the lanthanides. An equilibrium is set up between the lanthanide ions in the aqueous phase and the organic layer, with there tending to be a relative enhancement of the concentration of the heavier lanthanides in the organic layer. Because the separation between adjacent... 

The process was demonstrated in a simulated continuous counter-current chromatographic separation pilot plant. Both the primary method of operation and the pre-pulse technique were demonstrated, with the pre-pulse technique showing improved recoveiy. Using commercial n-paraffin depleted kerosene (Molex Raffinate) feedstock we routinely demonstrated the ability to achieve better than 90% mono-methyl and normal paraffin purity with greater than 70% recovery of mono-methyl paraffins. 

Continuous counter-current separation by SMB chromatography improves process economics. Nevertheless, more improved processes have been developed recently. They are all based on the standard SMB technology but operated under variable process conditions to reduce the costs of column hardware and stationary phase as well as for fresh eluent and eluent work-up. 

Cadotte ( ) presents a comprehensive review of the development of the composite membrane with emphasis on the pros and cons of the four preparation methods mentioned above and on the polymer chemistry Involved. Cadotte points out that while each of the four methods continues to receive some attention, the Interfaclal polymerization method appears to be the most versatile. This method can be used to produce skin layers from polyamines, polylmlnes, polyurethanes, polyesters and other polymers. Elsewhere In this volume, Lee and co-workers (45) discuss the advantages and problems associated with using these composite membranes for ethanol-water separations via counter-current reverse osmosis. Also, Cabasso (44) discusses double-layer composite membranes. 

Strohlein, G., Aumann, L., Mazzotti, M., and Morbidelli, M. (2006) A continuous, counter-current multi-column chromatographic process incorporating modifier gradients for ternary separations. /. Chromatogr. A, 1126, 338-346. 

The fissionable isotope passes from the water solution into the organic solvent, which is separated at the top of the column. The water solution containing the fission products is passed out of the bottom of the column into waste. The organic solvent containing the fissionable isotope is next charged to a similar continuous counter-current extraction column at the bottom and re-extracted into a water solution of the composition used in the pile. The columns are identical in construction, and the water layer from the bottom of the second column can be pumped directly back into the reactor or can be passed through further purification cycles as above, if needed. 

Tool for Continuous Counter-Current Adsorptive Separations, Ind. Eng. Chem. Proc. Des. Dev., 15, 261 (1976). 

A considerable saving in the number of operations is clearly made by mechanization of mixing, settling and separating. This, however, is only done in the case of certain specialized laboratory applications. Instead, it is more usual to allow the two phases to flow continuously rather than in discrete portions, and a large variety of plant and equipment is now available for carrying out these processes of continuous counter-current solvent extraction on an industrial scale. 

The 2,5-dihydrofurane (bp = 66 °C) and the crotonaldehyde (bp = 104 C) can then be separated from the reaction mixture by distillation due to their low boiling points, while the higher boiling oligomers remain in the IL-catalyst phase. This phase is fruther treated with an extractant solvent such as naphtha, to recover the oligomers and recycle the IL-catalyst. The plant is operated with three continuous, stirred-tank reactors, a wiped-film evaporator, a distillation train, and a continuous, counter-current, liquid-liquid extractor for recovery of the catalysts. The plant is now idle, because the market for the product has declined. 

The rest of this chapter, however, is concerned with continuous counter-current washing. The separators used may be sedimenting centrifuges, gravity thickeners or filters but the preferred choice is often hydrocyclones. The inherent advantages of hydrocyclones are compactness, small hold-up of liquid, high shear forces and turbulence in the flow, the latter two of which improve mass transfer and dispersion. 

Corrillard F, Foucault A, Duiand D (2(X)5) Process and device for separation of the components to a liquid load by centrifiigal liquid-liquid chromatography. Patent W02005011835 Van den Heuvel R, Mathews B, Dubant S, Sutherland 1 (2(X)9) Continuous counter-current extraction on an industrial sample using dual-flow counter-current chromatography. 

Oxygen (7 l.h ) is bubbled through a solution of colupulone (20 g 5 x 10 mol) in iso-octane (200 ml) at 50°C during 7 h, while the reaction vessel is continuously irradiated with visible light (Osram 500 W). A yellow oily precipitate is formed at the inner surface. After removal of the solvent the residue is separated by counter-current distribution in the two-phase system iso-octane aqueous buffer with pH values of 1.90, 4.50, 6.40, 7.00, 8.15 and 11.15, respectively. 

I.2.I.4. Enantioselective Extractions Enantioselective iiquid-iiquid extraction (ELLE) is an implementation of the extraction of one enantiomer from a racemic mixture by the transfer between two liquid phases. Liquid-liquid extraction can be easily operated in a continuous counter-current mode to fractionate the racemate into its enantiomers, and this is a great advantage for the up-scaling. The possibility to operate at all scales, from laboratory separations to bulk processes in the chemical and pharmaceutical industries, makes this technology of a great interest to a... 

In a packed column, liquid and vapor flow counter-currently and separation between the liquid and vapor phases takes place continuously. In contrast, in a column with trays, separation occurs in stages. In a packed column, vapor does not bubble through the liquid as in the columns with trays. For this reason, and due to the absence of the vapor-flow orifices, packed columns operate at a much lower pressure drop. In addition, because liquid and vapor contact in a packed column is less agitated than in a trayed column, packed columns are less likely to foam. 

The Swedish-Norwegian continuous process and the Hercules process are discussed below Swedish-Norwegian Chematur and Norsk Spraengstoffindustri Continuous Process This process, patented in Sweden in 1953 (Ref 42), employes stepwise nitration of mono- and/or di-nitrotoluene to trinitrotoluene in a series of counter-current units, each unit consisting of a nitrator and a separator... 

Continuous ion-exchange separation technology, which adopts counter-current processing in a rotating turntable, is currently making an impact and 70% of the world s lysine manufacture units use this technology. 

The separation of liquid mixtures by distillation depends on differences in volatility between the components. The greater the relative volatilities, the easier the separation. The basic equipment required for continuous distillation is shown in Figure 11.1. Vapour flows up the column and liquid counter-currently down the column. The vapour and liquid are brought into contact on plates, or packing. Part of the condensate from the condenser is returned to the top of the column to provide liquid flow above the feed point (reflux), and part of the liquid from the base of the column is vaporised in the reboiler and returned to provide the vapour flow. 

Separating funnels for batch extraction special glass apparatus for continuous extraction automatic shakers used for discontinuous counter-current distribution. 

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