Design of absorbers

Data Sources m the Handbook Sources of data for the analysis or design of absorbers, strippers, and distillation columns are mani-... 

Such data are necessary for the design of absorber systems however, they are not readily available for uncommon organic compounds. The solvent chosen to remove the... 

Souders, M. and Brown, G. G. Ind. Eng. Chem. 24 (1932) 519. Fundamental design of high pressure equipment involving paraffin hydrocarbons. IV. Fundamental design of absorbing and stripping columns for complex vapours. 

Data Sources in the Handbook Sources of data for the analysis or design of absorbers, strippers, and distillation columns are manifold, and a detailed listing of them is outside the scope of the presentation in this section. Some key sources within the handbook are shown in Table 14-1. 

Design of Absorber-Stripper Systems The solute-rich liquor leaving a gas absorber normally is distilled or stripped to regenerate the solvent for recirculation back to the absorber, as depicted in Fig. 14-3. It is apparent that the conditions selected for the absorption step... 

Temperature and Humidity of the Rich Gas Cooling and consequent dehumidification of the feed gas to an absorption tower can be very beneficial. A high humidity (or relative saturation with the solvent) limits the capacity of the gas to take up latent heat and hence is unfavorable to absorption. Thus dehumidification of the inlet gas is worth considering in the design of absorbers with large heat effects. 

Henry s law may be assumed to apply for most dilute solutions. This law finds widespread use in absorber calculations since the concentration of the solute in some process gas streams is often dilute. This greatly simplifies the study and design of absorbers. One should note, however, that Henry s law constant is a strong function of temperature. 

There is ample experimental evidence to show that the efficiencies of different components in a multicomponent system are not all equal. The first clear statement of this fact can be found in a paper by Walter and Sherwood (1941) who, on the basis of an extensive experimental study of Murphree vapor and liquid efficiencies for absorption, desorption, and rectification operations, concluded The results indicate that different efficiencies should be used for each component in the design of absorbers for natural gasoline and refinery gases. Since the publication of their paper many others have provided additional data to confirm this view [see Krishna and Standart (1979) for a list of references]. We review some of these data below. 

Although vapor-liquid equilibrium data represent the most critical data required for tbe design of absorbers and strippers, other physical property data also are needed. Properties are required for both the... 

The equations covering mass transfer with chemical reaction are not yet widely used in the design of absorbers and strippers. More coromonly, designs are based on experimental deta obtained with the same chemical system and similar equipment. However, examples have been worked out for a number of commercially important esses, and these are described in the recent literature. 

In a conventional type plant with a single absorber it is practical to design the plant to be autothermal with a gas containing as little as 3% sulfur dioxide because heat is only lost when the gas goes to the absorber plus the normal heat lost to atmosphere. In the double-catalysis process, heat is lost from the gas stream going to each of the two absorbers. In the normal design of absorber, if the total gas stream leaves the interstage absorber at 170-180°F to be reheated to converter temperature it would be impossible for the plant to be autothermal with 4% sulfur dioxide gas. 

The design of absorbing materials is a question of compromise. If a thin thickness of material is preferred to the detriment of the mass, magnetic materials will be selected. On the other hand, if thiekness higher than 10 mm is allowed, then dielectric materials would be the better solution [29]. 

Souders, M., and G. G. Brown, Fundamental Design of High Pressure Equipment Involving Paraffin Hydrocarbons. IV. Fundamental Design of Absorbing and Stripping Columns for Conplex Vapors, Ind. Eng. Chem., 24, 519 (1932). 

The most important physical property data required for the design of absorbers and strippers are gas-liquid equilibria. Since equilibrium represents the limiting condition fbr any gas-liquid contact, such data are needed to define the maximum gas purity and rich solution concentration attainable in absorbers and the maximum lean solution purity attainable in strippers. Equilibrium data also are needed to establish the mass transfer driving force, which can be defined simply as the difference between the actual and equilibrium conditions at any point in a contactor. 

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