Other Kinds of Extractors

Less specific information about the other kinds of extractors mentioned here is presented by Lo et al. (1983, pp. 419-448) but no integrated examples. The information perhaps could be run down in the abundant literature cited there, or best from the manufacturers. 

Centrifugal Contactors. These devices have large capacities per unit, short residence times, and small holdup. They can handle systems that emulsify easily or have small density differences or large interfacial tensions or need large ratios of solvent to feed. Some types are employed as separators of mixtures made in other equipment, others as both mixers and settlers, and some as differential contactors. 

Residence time can be as short as 10 sec. One 750 gpm unit is said to have a total liquid holdup of 200 gal. From 3-10 stages per unit have been reported, although Table 14.6 shows a range of 1.8-7.7. A 65 in. dia casing can accommodate throughputs up to 25,000 gal/hr. An economic comparison of a Podbielniak with other 

Column Type Maximum Load (mJ/(m,Xh)) Maximum Column Diameter (m) Maximum Throughput (mJ/h) 

These data apply at a high interfacial tension (30-40 dyn/cm). a viscosity similar to water, an inlet ratio of the phases of 1 1 parts by volume, and a density difference of approximately 0.6 g/cm . 

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Efficiencies of several kinds of small-scale extractors are shown in Fig. 19-28. Larger-diameter equipment may have less than one-half these efficiencies. Spray columns are inefficient and are used only when other kinds of equipment may become clogged. Packed columns as liquid-liquid reactors are operated at 20 percent of flooding. Their height equivalent to theoretical stage (HETS) range is from... 

The Soxhlet extractor (figure 8.4) is filled with fine grains of one of the two kinds of rock which are most common on the earth s surface, viz. basalt and granite. Next water is constantly passed through this rock mass and for a very long time. This results in a continuous extraction of materials from the rock in other words the rock is exposed to... 

The analysis of extracts is also possible by using other techniques, such as infrared spectrometry. This kind of detector is very useful because it provides a total spectrum for the analyte. For example, a method for analyzing poly(dimethylsiloxane) oil from polymer samples was developed by Kirschner et al. In this case, the extractor... 

An extension of the filter-driers are the reactor-filter-driers, as illustrated in Fig. 7.2-9 by an apparatus known under trademark name Nutrex" and developed by Rosenmund. Equipment of this kind is still more versatile and operation safer. In one vertical position the device can act as a filter, a granulator, and an apparatus for all operations with filter cakes (i.e. re-slurrying, smoothing, and squeezing). In the reverse position, it can operate as a reactor, extractor, evaporator, crystallizer, drier, etc. There are many other companies offering reactor-filter-driers, e.g. SEN, Giovanola, Schenk, and Cogeim. 

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