Absorption of gases in liquids

Bubble columns are important appliances for the absorption of gases in liquids and, consequently, for the execution of chemical reactions in gas/liquid system. In this context, the attainable interface (A sum of the surfaces of all gas bubbles) is of most interest because it affects the mass flow in a directly proportional manner. If a gas throughput q is introduced into a bubble column with the diameter D and the liquid height H, the liquid height rises by the amount occupied by the gas bubbles in the liquid. The gas fraction in the liquid, the so-called gas hold-up H can be determined from the liquid height Hr, of the gassed and the non-gassed liquid (see sketch). 

In many commercial processes such as distillation, extraction, absorption of gases in liquids, and the like, the entering and leaving streams represent two different phases that flow in opposite directions to each other, as shown in Fig. E2.22a. (The flgure could just as well be laid on its side.)... 

Shironji Hatta (1895—1973) was a professor at the Tohoku Imperial University, now the Tohoku University, in Tokyo, Japan. He undertook a number of fundamental studies about the absorption of gases in liquids, in particular absorption with simultaneous chemical reaction. 

Bunsen (1855), to whom we owe the first accurate measurements of the solubilities of gases in liquids, expressed his results in terms of an absorption coefficient /3, which he defined as the volume of gas, reduced to 0° C. and 76 cm., dissolved by 1 c.c. of the liquid at any given temperature under the same pressure. If v c.c. of gas are dissolved by Y c.c. of liquid at a temperature 6 and pressure p cm., the volume reduced to normal conditions is... 

The adsorption of gases on solid surfaces proceeds to such an extent that approximately 10 7 gr. is present per cm.2 in the equilibrium state. This is of the same order of magnitude as the strength of the limiting capillary layer of a liquid ( 184), hence it is not improbable, as suggested by Faraday (9) (1884), that the adsorbed gas is sometimes present in the liquid state. The adsorbed amount increases with the pressure and diminishes with rise of temperature. The first effect does not follow a law of simple proportionality, as in the case of the absorption of gases by liquids, rather the adsorbed amount does not increase so rapidly, and the equation ... 

FIG. 14-79 Liquid-film resistance in absorption of gases in wetted-wall columns. Theoretical lines are calculated for oxygen absorption in water at 55°F, To convert feet to meters, multiply by 0.3048 °C = % (°F - 32). (Sherwood and Pigford, Absorption and Extraction, 2d ed., McGraw-Hill, New York, 1952.)... 

Nitrate explosives. The term explosion is applied to the effect produced by a sudden change in the pressure of one or more gases. This may be the result of either chemical or physical changes—that is, the sudden liberation or absorption of gases in chemical reactions or the sudden formation of gases from either liquids or solids. Because certain nitrates decompose readily with liberation of gaseous products, these substances are useful in compounding a variety of commercial explosives. Ammonium nitrate is stable under ordinary atmospheric conditions and may be handled safely in small quantities, even at elevated temperatures. When the dry salt is heated, it decomposes with liberation of nitrous oxide and water,... 

In this section we consider the rate of absorption of gases into liquids that are agitated so that dissolved gas is transported from the interfacial surface to the interior by convective motion. The next section, based on this one, treats chemical methods for determining interfacial areas and mass-transfer coefficients in agitated gas-liquid reactors. 

The resistance to mass transfer according to (1.221) and (1.223) is made up of the individual resistances of the gas and liquid phases. Both equations show how the resistance is distributed among the phases. This can be used to decide whether one of the resistances in comparison to the others can be neglected, so that it is only necessary to investigate mass transfer in one of the phases. Overall mass transfer coefficients can only be developed from the mass transfer coefficients if the phase equilibrium can be described by a linear function of the type shown in eq. (1.217). This is normally only relevant to processes of absorption of gases by liquids, because the solubility of gases in liquids is generally low and can be described by Henry s law (1.217). So called ideal liquid mixtures can also be described by the linear expression, known as Raoult s law. However these seldom appear in practice. As a result of all this, the calculation of overall mass transfer coefficients in mass transfer play a far smaller role than their equivalent overall heat transfer coefficients in the study of heat transfer. 

Absorption an irreversible chemical retention effect on surfaces, either liquid or solid. Improperly applied to the dissolution (physical effect) of gases in liquids. 

Wang RLC, Kreuzer HJ, Grunze M (2006) Theoretical modeUing and interpretation of x-ray absorption spectra of liquid water. Phys Chem Chem Phys 8 4744-4751 Wilhelm E, Battino R, Wilcock RJ (1977) Low-pressure solubility of gases in liquid water. Chem Rev 77 219-262... 

Henry s law is significant for the description of processes of ab- and desorption of gases in liquids. Absorption takes place when the partial pressure of the gas in contact with the liquid is greater than the equilibriiun pressure and therefore the gas is solved in the liquid. Desorption is the opposite process, thus the removal of gas out of liquids, see Chap. 5. 

Diffusion coefficients in liquids are of great significance in many theoretical and engineering calculations involving mass transfer, such as absorption, extraction, distillation, and chemical reactions. The measurement of accurate diffusion coefficients of gases in liquids is not an easy task. Different values are often obtained from different workers in different laboratories, even by using similar measuring techniques. 

Fuels such as diesel and kerosene readily absorb hydrocarbon vapors, the total uptake and absorption rate depending on both chemical and physical factors. If a soluble test gas is introduced above a charged test oil the concentration of flammable test gas therefore decreases with time. Liquid mist and spray produced by charged liquid increase the absorption rate relative to a quiescent liquid surface. As discussed in A-5-4, absorption could lead to an underestimation of test gas MIE near the liquid surface unless the rate of test gas introduction is sufficiently high to offset the rate of removal. Table 3-8.1.2 shows solubilities of a selection of gases in a mineral-based transformer oil at ambient temperature and pressure [200]. 

Gas absorption The process of absorption of gases that takes place in certain solids or liquids. 

Fig. 7.5. Fitting of the -dependence of the widths for the rotational absorption spectrum of HC1 in liquid noble gases. Experimental data are shown by dots, theoretical calculations by solid curve.

Inspired by Henry s work, Dalton spent much time in early 1803 measuring solubilities of various gases the results of this work he published in the memoir On the Absorption of Gases by Water and Other Liquids. 

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