Rotary extractors

Lee JGM, Howarth CR, Ramshaw CR. Trace effluent removal from large flowrate aqueous phase using a packed rotary extractor. In Proceedings of Value Adding Solvent Extraction (Pap ISEC 96), Melbourne, 1996 1185-1190. 

All rotary extractors employ deep beds of solids to be extracted, sometimes as much as two or more meters deep. Hence, rotary extractors are also termed deep-bed extractors. There are several mechanical variations of these extractors. Two variations have already been mentioned. Another variation is where the individual cells have hinged bottoms that swing open whenever the cell is to be emptied. In this variation, the solids slide against a common one-piece bottom that has an opening to allow solids to fall through when extraction is completed. Termed sliding plate. 

If a deep-bed rotary extractor is run so that the solvent/miscella makes only one pass through each stage, then preparation should be monitored to ensure that miscella does not rush through any stage without spreading across the surface or that no stage floods. Usually, on a deep-bed extractor, flooding is more likely to... 

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Unfortunately, since the preferred width of annulus is fairly constant for any diameter of column, the throughput of a rotary extractor is approximately proportional to its diameter, whereas that of other types is more nearly proportional to the square of the diameter. Consequently, the use of this type of extractor is limited to small-scale processes, and it has also been applied in a highly successful manner as an analytical tool, i.e. for the puri-flcation of continuous samples from process streams prior to analysis. The high precision engineering required for the construction of rotors capable of high-speed rotation also militates against their use on a larger production scale. 

R. F. Downing and E. B. James. Dust extractors for rotary abrasive tools. British Patent no. 780 761. London Patent Office. 1957. 

Extraction can be performed in stirred tanks if the process proceeds fast and separation of phases is ea.sy, but column extractors are most commonly used. The column can be filled with a particulate material. The liquids flow countercurrently whereby the flow can be uniform or pulsed. Reciprocated and rotary agitators are often used to enhance mass transfer. An example of the latter type is shown in Fig. 7.2-13 (asymmetric rotating disk (ARD) extractor). 

A wide variety of extraction column forms are used in solvent extraction applications and many of these, such as rotary-disc contactors (RDC), Oldshue-Rushton columns, and sieve-plate column extractors, have rather distinct compartments and a geometry, which lends itself to an analysis of column performance in terms of a stagewise model. As the compositions of the phases do not come to equilibrium at any stage, however, the behaviour of the column is therefore basically differential in nature. 

Nitrobenzene oxidation was carried out by adding 50 mg of dry soda lignin into a mixture of 7 mL of 2 M NaOH and 4 ttiL of nitrobenzene in a 15 ttiL steel autoclave. Then, the antoclave was heated to 165°C for 3 hours in a preheated thermostat oil bath. After the autoclave was cooled to room temperature, the mixture was then transferred to a liqnid-hquid extractor for continuous extraction with chloroform (5 x 20 mL) in order to remove any nitrobenzene reduction product and excess nitrobenzene. The oxidation mixtnre was then acidified by concentrated HCl to pH 3 and further extracted with chloroform (5x15 mL). The solvent from the second chloroform solution was then removed using a rotary evaporator at 40°C under reduced pressure in order to obtain the nitrobenzene oxidation mixture. The mixture was then dissolved into dicloromethane and made up to 10 luL. This mixture was then used as a stock solution for high performance liquid chromatography (HPLC) analysis [6]. 

Some novel types and variations of basic types of extractors have been developed, most of which have not found wide acceptance, for instance pulsed rotary towers. The literature of a few of them is listed by Baird (in Lo et al., 1983, pp. 453-457). Here the extractors illustrated in Figure 14.15 will be described. 

Juice extractors differ in design, but all are fast, rugged, easy to clean, and adjustable to accomodate fruit of different sizes. Prior to the invention of automatic extractors, the rotary juice press was in common use, and is still used commercially in many parts of the world, principally Italy, Spain, South America. 

For recovery, the broth is clarified by means of rotary vacuum filters. The penicillin, being acidic, is extracted from the aqueous phase into a solvent, such as methyl isobutyl ketone or amyl acetate, at a pH of 2.5 by means of a continuous countercurrent extractor, such as a Podbielniak. The penicillin is then reextracted with an aqueous alkaline solution or a buffer at a pH of 6.5-7.0. About 90 percent recovery yield is typical at this step. The... 

Procedure. A measured amount of water, optimum quantity 5000 gallons (18,925 liters), was pumped through a column of Nuchar C-190, 30-mesh activated carbon 3 inches in diameter by 18 inches in height. The pumping rate used was 0.5 gallon per minute. After collection, the carbon was removed from the filter, air-dried, and placed in a modified Soxhlet extractor to remove the organic matter by benzene. Except for 250 ml., all solvent was removed by distillation. The remaining solvent was further reduced to approximately 4 ml. by rotary vacuum evapora-... 

Fans extractors Hoist and trolleys Rotary valves In-line filters... 

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