Distillations, Application

While the carbon dioxide/caiistic test method has become accepted, one should use the results with caution. The chemical reaction masks the effect of physical absorption, and the relative values in the table may not hold for other cases, especially distillation applications where much of the resistance to mass transfer is in the gas phase. Background on this combination of physical and chemical absorption may Be found earher in the present section, under Absorption with Chemical Reaction. ... 

Distillation Applications Packings are now routinely considered for distillation columns with diameters up to 10 m or more. The pressure drop advantages of the modern, through-flow random pack-... 

Figure 9-8K. Spray nozzle distributor using full-cone wide-angle spray nozzles (depends on tower diameter). Not recommended for distillation applications, where the point-type distributors provide higher packing efficiency. Used by permission of Nutter Engineering, Harsco Corp., Bull. TI-1.

The use of V-notches in a trough wall for overflow is more sensitive to leveling problems than the other designs, and for the same %- to Me-in. level tolerance produces a more severe non-uniform flow distribution. The quality of distribution from a V-notch is poor compared to the other types of trough distributor, but does have advantages in slurry systems [131]. It should not be used for critical distillation applications, but is good for heat transfer and where solids are in the system. 

These distributors are fabricated of pipe lengths tied to a central distribution header (usually) %vith orifice holes drilled in the bottom of the various pipe laterals off the header. This style of distributor can be fed by pressure or gravity for clean fluids. The gravity feed is considered better for critical distillation application when uniformity of the flow of the drip points (or flow points) through out the cross-section of the tower is extremely important, and is excellent for low flow requirements such as below 10 gpm/ft2 [131]. 

Sulfolane (TMS) [22] Main impurities are water and 3-sulfolene (decomposed to S02 and 1,3-dibutadiene at >70°C), but 2-sulfolene and isopropyl sulfolanyl ether may also be present. For fairly pure commercial products, two vacuum distillations, the second of which is from solid NaOH, can give a distillate applicable for most general purposes. The water level is <5 mM. The distillate should be stored in the dark under a nitrogen atmosphere. For a method of purifying fairly contaminated products, see Ref. [22]. 

Use of HETP Data for Absorber Design Distillation design methods (see Sec. 13) normally involve determination of the number of theoretical equilibrium stages N. Thus, when packed towers are employed in distillation applications, it is common practice to rate the efficiency of tower packings in terms of the height of packing equivalent to one theoretical stage (HETP). 

The higher heat transfer coefficients experienced by Hickman led to the concept of placing a peripheral reboiler and core condenser on either side of a rotating packed bed (50). This concept would be useful for distillation applications that need reflux and boilup. The internal exchangers as part of the rotor would decrease the required heat transfer surface area but would involve additional design and fabrication complexity. 

Understand the advantages of using packed versus trayed towers for certain distillation applications. 

Vertical in-tube condensers—upflow. This type of condenser is often termed inerts condenser, vent condenser, or knockhack condenser. It is used in some partial condensers when small quantities of vapor flow upward, while most of the condensate drains backward by gravity. Some fractionation takes place, and the mode of flow is similar to a wetted wall column. The most common distillation application of vent condensers is in internal condensers (below), or as a secondary... 

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