Solvent extraction spray towers

Extraction (sometimes called leaching) encompasses liquid-liquid as well as liquid-solid systems. Liquid-liquid extraction involves the transfer of solutes from one liquid phase into another liquid solvent it is normally conducted in mixer settlers, plate and agitated-tower contacting equipment, or packed or spray towers. Liquid-solid extraction, in which a liquid solvent is passed over a solid phase to remove some solute, is carried out in fixed-bed, moving-bed, or agitated-solid columns. 

While flowsheets are generally the same in principle in other plants, they frequently differ in details. For example, Crawford (30) describes a plant in which the extractors are spray towers, where the pyridine is continuously removed from a portion of the extracting solvent by an acid wash, and where CO2 or NaHCOs is used instead of H2SO4 to release the phenols from... 

Type C In order to overcome the disadvantage of loss of extract involved in processes of type B, the adsorption stages may be replaced by absorption into a liquid. In processes of this type the extract which has been dissolved in the solvent is absorbed by a wash fluid flowing countercurrent to the ex-tract/solvent stream. The absorption takes place in high pressure vessels which may either be operated as spray towers or as packed columns. Quick-acting closures are not necessary for these vessels. 

Almost all countercurrent extraction devices utilize dispersion of one immiscible phase as drops in another immiscible phase we will provide a brief introduction here. At the end, we will introduce porous hollow fiber membrane based nondispersive countercurrent solvent extraction devices. The dispersive devices may involve continuous agitation or no agitation at all. Dispersive devices without any agitation as such are of three types spray towers packed towers perforated plate towers. Spray towers were illustrated in Figure 8.1.2(b). 

---