Packed towers mechanism

The transfer of mass between phases in a packed tower occurs either as essentially all gas film controlling, all liquid film controlling, or some combination of these mechanisms (see Figure 9-69). To express the ease (low number... 

Covers distillation and packed towers, and shows how to apply techniques of process design and interpret results into mechanical equipment details... 

As Sherwood and Pigford(3) point out, the use of spray towers, packed towers or mechanical columns enables continuous countercurrent extraction to be obtained in a similar manner to that in gas absorption or distillation. Applying the two-film theory of mass transfer, explained in detail in Volume 1, Chapter 10, the concentration gradients for transfer to a desired solute from a raffinate to an extract phase are as shown in Figure 13.19, which is similar to Figure 12.1 for gas absorption. 

Figure 13.15. Mechanism, nomenclature, and constructions for absorption, stripping and distillation in packed towers, (a) Two-film mechanism with equilibrium at the interface, (b) Sketch and nomenclature for countercurrent absorption or stripping in a packed tower, (c) Equilibrium and material balance lines in absorption, showing how interfacial concentrations are found, (d) Equilibrium and material balance lines in stripping, showing how interfacial concentrations are found, (e) Equilibrium and material balance lines in distillation, showing how interfacial concentrations are found.

For gas absorption, the equipment possibilities are generally packed columns plate distillation towers, possibly with mechanical agitation on every plate deep-bed contactors (bubble columns or sparged lagoons) and mechanically agitated vessels or lagoons. Packed towers and plate distillation columns are discussed elsewhere. Generally these... 

The design of a packed tower requires consideration of mechanical factors, such as pressure drop, flow capacities, and foundation load. In addition, consideration must be given to the factors that influence the effectiveness of contact between the fluid phases. A satisfactory packing should have the following properties ... 

I. Gravity-operated extractors A. No mechanical agitation 1. Spray towers 2. Packed towers... 

This latest edition covers the technical performance and mechanical details of converting chemical and petrochemical processes into the appropriate hardware for distillation and packed towers. It incorporates recent advances and major innovations in distillation contacting devices and features new generations of packing. In addition, this new edition reflects the significant progress that has been made in process design techniques in recent years. 

Such processes as mechanical surface aeration, diffused aeration, spray fountains, spray or tray towers, open-channel cascades, and countercurrent packed towers are encompassed by the term air stripping. These procedures produce a condition in which a large surface area of the water to be treated is exposed to air, which promotes transfer of the contaminant from the liquid phase to the gaseous phase. This occurs because under normal conditions the concentration of the contaminant in ambient air is much lower than the concentration in contaminated water. 

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