Absorption of CO2 in water

Determination of ArRe rit for film flow is made from measurements of absorption of CO2 in water film. Effects of wall roughness on iVReorit were also studied. 

Bhaumik et al. [4] demonstrated the efficiency of transverse flow hollow fiber devices equipped with fibers in a mat wrapped around a central tube (distributor of the liquid) for the absorption of CO2 in water. 

The influence of the partial pressure of the solute on its equilibrium content in the solvent, the loading Xabs> is shown in Figure 3.3.24 for a physical absorption of CO2 in water and methanol and a chemical absorption in an aqueous solution of monoethanolamine (MEA). 

Example 3.3.4 Absorption of CO2 in water and subsequent bicarbonate formation... 

Example 3.3.6 Basic design data of a column for absorption of CO2 in water... 

Massimilla et al. ["2l[j measured the rate of absorption of CO2 in water using 3 sizes of silica and glass particles smaller than 1mm. They concluded that the absorption rate increased with increasing liquid velocity and decreased with increasing particle sizeo... 

The applicability of model <23> as formulated here with consideration of gas flow and pressure variations has been demonstrated by Deckwer [34] for absorption and hydration of isobutene in sulfuric acid and by Deckwer et a1. [35, 36] for CO2 mass transfer. The physical absorption of CO2 in water proved to be a very useful tool to simulate conditions which often prevail in chemical processes, i.e. large amounts of gas are absorbed in a liquid under drastic changes of gas volume flow. As an example Fig. 11 shows CO2 gas phase profiles measured in a BC of 20 cm diameter and 7.2 m height. As shown in Fig. 11, the profiles computed on the basis of model <23> excellently describe the measured data. It is understood that... 

Another technique for studying the absorption of CO2 into water uses an interferometer to obtain the concentration gradients as close as 0.01 cm. to the surface (Bl) a cine-camera permits results to be obtained within 5 sec. of the admission of the CO2. Though various corrections are I c fiuired, it is claimed that this method eliminates convection difficulties and that resistances as low as 0.25 sec. cm. i can be detected. Experimental results for CO2 into distilled water show no detectable interfacial resistance, though, when surface-active agents (Lissapol, Teepol) are dissolved in the water, the values of Rj are about 35 sec. cm.. ... 

With a reactive solvent, the mass-transfer coefficient may be enhanced by a factor E so that, for instance. Kg is replaced by EKg. Like specific rates of ordinary chemical reactions, such enhancements must be found experimentally. There are no generalized correlations. Some calculations have been made for idealized situations, such as complete reaction in the liquid film. Tables 23-6 and 23-7 show a few spot data. On that basis, a tower for absorption of SO2 with NaOH is smaller than that with pure water by a factor of roughly 0.317/7.0 = 0.045. Table 23-8 lists the main factors that are needed for mathematical representation of in a typical case of the absorption of CO2 by aqueous monethanolamlne. Figure 23-27 shows some of the complex behaviors of equilibria and mass-transfer coefficients for the absorption of CO2 in solutions of potassium carbonate. Other than Flenry s law, p = HC, which holds for some fairly dilute solutions, there is no general form of equilibrium relation. A typically complex equation is that for CO2 in contact with sodium carbonate solutions (Harte, Baker, and Purcell, Ind. Eng. Chem., 25, 528 [1933]), which is... 

Recovery of power from the thermal energy of a high temperature stream is the subject of Example 1.5. A closed circuit of propane is the indirect means whereby the power is recovered with an expansion turbine. Recovery of power from a high pressure gas is a fairly common operation. A classic example of power recovery from a high pressure liquid is in a plant for the absorption of CO2 by water at a pressure of about 4000 psig. After the absorp-... 

Absorption of CO2 in carbonate buffer soluhons in packed columns oxidation of black liquor in the paper and pulp industry absorption of CO2 in carbonate soluhon wet air oxidahon of soluble compounds in waste water. 

This dependence of ki on was also reported by Prasher and Wills (1973) based on the absorption of CO2 into water in an agitated vessel, as follows ... 

Fig. 2.94 Solubility of CO2 in water (at 1 atm CO2) in terms of the dimensionless Bunsen absorption coefficient a in dependence from temperature (in volume dissolved CO2 / volume of solution) data from Gmelin (1943).

We see from Reactions (5.15) that for every mole of CO2 that is absorbed in water, one mole of H30 (aq) is produced. Therefore, to produce 0.25 x 10 M of H30 (aq), 0.25 x 10 moles of CO2 would have to be absorbed in each liter of rainwater. Since this is about the solubility of CO2 in water at atmospheric pressure, we see that the absorption of CO2 in rainwater will cause it to have a pH of about 5.6. 

Figure 3.3.33 McCabe-Thiele diagram for absorption of CO2 in cold water (5 °C).

Figure 14.3.1.B-2 shows the partial pressure and concentration profiles of CO2 and MEA in the gas and liquid films at a number of heights in the column. Since CO2 is not very soluble, the absorption of CO2 in pure water is controlled by the resistance to mass transfer in the liquid film. In a MEA solution, on the other hand, the absorption is strongly enhanced by the very fast reaction, and gas film resistance to mass transfer becomes important. No depletion of the reactant MEA is observed at the top of the column, and the reaction is of pseudo-first order. At the bottom of the column the depletion of the MEA is almost complete in the liquid film.

Under turbulent flow condition, the transfer of species (mass) from adjacent phase to the phase concerned, such as physical absorption like the absorption of CO2 by water, the following steps are undertaken in sequence ... 

Letter B denotes the group HOCH2.CH2 and step (Rl) represents the physical absorption of CO2 by water, accompanied by the heat of solution H - At very short time of exposure in industrial practice, the effect of reaction (R3) can be neglected, and only reaction (R2) affects the absorption rate of CO2. Reaction (R2) can be... 

The absorption of CO2 into water and dilute alkaline solutions is hindmed by a slow chemical reaction which is required to convert the dissolved carbon dioxide molecules into the more reactive ionic species. In effect, the CO2 molecules are absorbed until some molecules are removed by the hydration reaction. The efficiency of CO2 absorption can, therefore, be improved by turbulence in the liquid film (this aids diffusion of unreacted molecules into the body of the liquid) and by an extended hold-time of liquid in the absorption zone (this provides for the continuous reaction of CO2 molecules that do entm the liquid phase). These conditions can be met, for example, by a tall, packed column operating at a relatively high liquid-flow rate or by a liquid-filled column through which bubbles of gas are made to pass. 

A mixed gas of 60 to 75 percent CO2 derived from mixing the 40 percent CO2 from the kilns and the 90 percent CO2 from the calcination of bicarbonate, is fed to the bottom of these crystallizing units. Absorption of CO2 in the highly alkaline ammoniated brine results in crystallization of crude sodium bicarbonate. Because of the heat evolved in the absorption and neutralization of the carbonic acid gas and from crystallization of the sodium bicarbonate, the temperature of the liquor in the column rises from 38°C to a maximum of about 62 to 64°C. In normal operation, the temperature of the discharge slurry is maintained at about 27°C by automatic adjustment of the water flow through the cooling tubes. A tower such as that shown in Fig. 12.3 has a capacity for producing 50 tons/day of finished soda. 

Other methods for analyzing combustion products can be substituted for chromatography. Gravimetry can be used, for example, after a series of absorption on different beds, as in the case of water absorption in magnesium perchlorate or CO2 in soda lime infra-red spectrometry can be used for the detection of CO2 and water. 

Lujuid-Pha.se Transfer. It is difficult to measure transfer coefficients separately from the effective interfacial area thus data is usually correlated in a lumped form, eg, as k a or as These parameters are measured for the Hquid film by absorption or desorption of sparingly soluble gases such as O2 or CO2 in water. The Hquid film resistance is completely controlling in such cases, and kjji may be estimated as since x (Fig. 4). This... 

Boiler Water Treatment. Alkanolamines, in general, provide excellent corrosion protection to steel in many appHcations. When used in boiler water treatment, AMP provides excellent protection to steel and copper in steam lines through efficient absorption of CO2, effectual distribution ratio for... 

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