Transfer interfacial areas and mass

Generally speaking, the design of TBR requires knowledge of hydrodynamics and flow regimes, pressure-drop, hold-ups of the phases, interfacial areas and mass-transfer resistances, heat transfer, dispersion and back-mixing, residence time distribution, and segregation of the phases. 

A. Schumpe, W.D. Deckwer, Gas holdups, specific interfacial areas, and mass transfer coefficients of aerated carboxymethyl cellulose solutions in a bubble column, I EC Process Des. Develop. 21 (1982) 706-711. 

M. Bouaifi, G. Hebrard, D. Bostoul, M. Roustan, A comparative study of gas hold-up, bubble size, interfacial area and mass transfer coefficients in gas—liquid reactors and bubble columns, Chem. Eng. Proc. 40 (2001) 97-111. 

C.W. Robinson, C.R. Wilke, Simultaneous measurement of interfacial area and mass transfer coefficients for a well-mixed gas dispersion in aqueous electrolyte solutions, AIChE J. 20 (1974) 285-294. 

For example, it is found that the mass transfer coefficient, Kca, for gas-liquid processes, is mostly a function of the linear superficial gas velocity and the power per unit volume with the constant D/T ratio for various size tanks. This is because the integrated volumetric mass transfer coefficient over the entire tank can be quite similar in large and small tanks even though the individual bubble size, interfacial area, and mass transfer coefficient can vary at specific points within the small and large tanks. 

In this study, a and kLa are measured in a TBR in the pressure range [0.3-3.2 MPa] using fast and slow chemical absorption of carbon dioxide into diethanolamine (DEA) aqueous and organic solutions. Only the trickling regime and trickling/pulsing transition have been explored. A simple model to explain the increase of interfacial area and mass transfer... 

III. Measurement of Interfacial Areas and Mass-Transfer Coefficients. 35... 

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. 

When necessary, results of surface-renewal theories will be presented simultaneously, as these models may be applied directly to determine interfacial area and mass-transfer coefficients in the laboratory apparatus considered in Sections III,B and V. 

Chemical methods for determining gas-liquid interfacial areas and mass-transfer coefficients have been intensively developed for the last 10 years. The principles of these methods are deduced from the results presented in Section III,B,2 A gas A is absorbed into a liquid where it undergoes a reaction with a dissolved reactant B ... 

INTERFACIAL AREA AND MASS TRANSFER COEFFICIENT IN GAS-LIQUID DISPERSIONS... 

The main reason for the deficiencies of the present state of the art is, however, the maldistribution of gas and liquid in packed beds. Many studies reveal that there exist large deviations from plug flow of gas and in particular of hquid within the bed. (Hoek et al. 1986 Kammermaier 2008). The degree of maldistribution as well as its effect on mass transfer are unknown and, in turn, not accounted for in existing mass transfer models. Thus the pubhshed data for interfacial area and mass transfer coefficients comprise the maldistribution in an undefined manner. The data are not true but pseudo values which are not predictable within the plug flow model. 

Gas dispersion in agitated tanks may be described in terms of bubble size, gas hold-up, interfacial area and mass transfer coefficient. While gas dispersion in low viscosity systems [Smith, 1985 Tatterson, 1991 Hamby et al., 1992] has been extensively studied, little is known about the analogous process in highly viscous Newtonian and non-Newtonian media, such as those encoim-tered in polymer processing, pulp and paper manufacturing and fermentation applications. 

Sharma.M.M. and P.V.Danckwerts. "Chemical methods of measuring interfacial area and mass transfer coefficients in two-phase systems." Brit.Chem.Eng. 15 (1970) 522-528. 

Sridharan,k. and M.M.Sharma. "New systems and methods for the measurement of effective interfacial area and mass transfer coefficients in gas-liquid contactors". Chem.Engng.Sci. 31 (1976) 767. 

Rate measurements with well-stined vessels may be continuous or batch. An example of the latter is simply a stirred flask. The former include the AKUFVE apparatus and bench-scale models of mixer-settler contactors. Because the interfacial area and mass transfer conditions in these systems are not known, th generally do not yield intrinsic heterogeneous rate data for metal-extraction systems. Nevertheless, th are useful for screening relative rates and identifying cases where slow kinetics may be a problem. 

The mechanisms by which freely rising bubbles interact with each other in relatively low-viscosity liquids and, specifically, how they approach, contact, and coalesce or break up are important aspects of multi-phase flow. Coalescence and breakup can control the interfacial area and mass transfer rate in bubble columns and gas-sparged chemical and biological reactors. Bubble interaction is fundamental in two-phase flow instability that plagues boilers and oil and gas wells. But bubble interaction remains a relatively mysterious area. 

Film and overall mass-transfer coefficients in packed towers. As discussed in Section 10.5 it is very difficult to measure experimentally the interfacial area A m between phases L and V. Also, it is difficult to measure the film coefficients k and ky and the overall coefficients K and Kf Usually, experimental measurements in a packed tower yield a volumetric mass-transfer coefficient that combines the interfacial area and mass-transfer coefficient. 

The rate and the manner in which energy is delivered influence such important fluid-fluid parameters as dispersed-phase holdup, interfacial area, and mass transfer coefficient (Calderbank, 1958 Nagel et al 1972, 1973 KastanSc, 1976 Zahradnik et al 1982 Oldshue, 1983). Thus, an energy-based classification would be both useful and appropriate. In this classification, the contactors are essentially divided into three broad groups ... 

Dhanuka, V.R. and J.B. Stepanek, "Simultaneous Measurement of Interfacial Area and Mass Transfer Coefficient in Three-Phase Fluidized Bed". AIChE J. (1980) 1029-1038. 

Robinson, C.W., and Wilke, C.R., "Simultaneous Measurement of Interfacial Area and Mass Transfer Coefficients for Well-Mixed Gas Dispersion in Aqueous Electrolyte Solutions",... 

Specify the arrangement to be used and estimate the average gas-bubble diameter, gas holdup, specific interfacial area, and mass-transfer coefficient to be expected. 

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