Liquid mass transfer coefficient

FIG. 18-28 Usually, the gas-liquid mass-transfer coefficient, K, is reduced with increased viscosity. This shows the effect of increased concentration of microbial cells in a fermentation process. 

Hog, Hql = Height of transfer unit based on overall gas or liquid film coefficients, ft Gm, Ljn = Gas or liquid mass velocity, lb mols/(hr) (ft ) Kga, Kla = Gas or liquid mass transfer coefficients, consistent units... 

Coppock and Meiklejohn (C9) determined liquid mass-transfer coefficients for the absorption of oxygen in water. The value of k, was observed to vary markedly with variations of bubble velocity, from 0.028 to 0.055 cm/sec for a velocity range from 22 to 28 cm/sec. These results appear to be in general agreement with the results obtained by Datta et al. (D2) and by Guyer and Pfister (G9) for the absorption of carbon dioxide by water. 

Later publications have been concerned with mass transfer in systems containing no suspended solids. Calderbank measured and correlated gas-liquid interfacial areas (Cl), and evaluated the gas and liquid mass-transfer coefficients for gas-liquid contacting equipment with and without mechanical agitation (C2). It was found that gas film resistance was negligible compared to liquid film resistance, and that the latter was largely independent of bubble size and bubble velocity. He concluded that the effect of mechanical agitation on absorber performance is due to an increase of interfacial gas-liquid area corresponding to a decrease of bubble size. 

The volumetric gas-liquid mass transfer coefficient ki a) has been obtained by fitting the concentration profile of dissolved oxygen to the axial dispersion model [8, 18]. The value of... 

Evaluation of reactor hydrodynamics by measuring gas-liquid mass transfer coefficient... 

This research used mechanically agitated tank reactor system shown in Fig. 1. The reactor, 102 mm in diameter and 165 mm in height, was made of transparant pyrex glass and was equipped with four baffles, 120 mm in length and 8 mm in width, and six blades disc turbine impeller 45 mm in diameter and 12 mm in width. The impeller was rotated by electric motor with digital impeller rotation speed indicator. Waterbath thermostatic, equipped with temperature controller was used to stabilize reactor temperature. Gas-liquid mass transfer coefficient kia was determined using dynamic oxygenation method as has been used by Suprapto et al. [11]. 

The measurement of liquid side gas - liquid mass transfer coefficient kia, showed that the value of kia increase with increasing rotation speed (V) and gas flow rate (Qg). hi the present research, the effect of impeller rotation on mass transfer coefficient was more significant than the effect of gas flow rate. The following correlation was obtained kia =1.7 x 10 ... 

Gas-Liquid Mass Transfer. Gas-liquid mass transfer within the three-phase fluidized bed bioreactor is dependent on the interfacial area available for mass transfer, a the gas-liquid mass transfer coefficient, kx, and the driving force that results from the concentration difference between the bulk liquid and the bulk gas. The latter can be easily controlled by varying the inlet gas concentration. Because estimations of the interfacial area available for mass transfer depends on somewhat challenging measurements of bubble size and bubble size distribution, much of the research on increasing mass transfer rates has concentrated on increasing the overall mass transfer coefficient, kxa, though several studies look at the influence of various process conditions on the individual parameters. Typical values of kxa reported in the literature are listed in Table 19. 

The proposed catalyst loading, that is the ratio by volume of catalyst to aniline, is to be 0.03. Under the conditions of agitation to be used, it is estimated that the gas volume fraction in the three-phase system will be 0.15 and that the volumetric gas-liquid mass transfer coefficient (also with respect to unit volume of the whole three-phase system) kLa, 0.20 s-1. The liquid-solid mass transfer coefficient is estimated to be 2.2 x 10-3 m/s and the Henry s law coefficient M = PA/CA for hydrogen in aniline at 403 K (130°C) = 2240 barm3/kmol where PA is the partial pressure in the gas phase and CA is the equilibrium concentration in the liquid. 

Gas-liquid mass transfer coefficient. The correlation of Sato (.First Pacific Chem Eng Congress p 187, 1972),... 

Solid-liquid mass transfer coefficients in airlift reactors, 15 727t relationships for estimating, 15 719-721t Solid-liquid protein separation, 12 136 Solid-liquid sedimentation, 22 50, 51 Solid-liquid separation (SLS)... 

KGa Gas-liquid mass transfer coefficient referring to concentration in G-phase 1/s... 

An analogous approach was applied on the calculation of the gas-liquid mass transfer coefficient of hydrogen (kLn) The physical parameters needed for the mass transfer coefficients and the dimensionless parameters (Re, Sc) are listed in the Notation section near the end of this chapter. 

The solid-liquid mass transfer coefficient without aeration is a function of power consumption per unit volume of the liquid. One typical case is the Levins and Glastonbury correlation for small particles (<2 mm), fully suspended and moderate density differences (Treybal, 1980) ... 

One more correlation is that of Calderbank-Moo-Young for the solid-liquid mass transfer coefficient in stirred tanks without aeration (Kato et al., 2001)... 

The liquid mass transfer coefficient (or convection coefficient) is a flow-dependent parameter, which can be evaluated from several correlations found in the related literature. 

The gas-liquid mass transfer coefficient is given by Reiss correlation (Ramachandran and Chaudhari, 1984) ... 

The conditions (a), (b), (c), and (d) are met since we have the experimental value of the gas-liquid mass transfer coefficient, the wetting efficiency is given to be 100%, plug-flow condition is assumed in the original study, and the expansion factor is zero as the oxygen concentration has been taken as constant. 

Chapman C M. Gilibaro L G, Nienow A W (1982) A dynamic response technique for the estimation of gas-liquid mass transfer coefficients in a stirred vessel, Chemical Engineering Science 37 1891-896. 

The influence of pressure on the mass transfer in a countercurrent packed column has been scarcely investigated to date. The only systematic experimental work has been made by the Research Group of the INSA Lyon (F) with Professor M. Otterbein el al. These authors [8, 9] studied the influence of the total pressure (up to 15 bar) on the gas-liquid interfacial area, a, and on the volumetric mass-transfer coefficient in the liquid phase, kia, in a countercurrent packed column. The method of gas-liquid absorption with chemical reaction was applied with different chemical systems. The results showed the increase of the interfacial area with increasing pressure, at constant gas-and liquid velocities. The same trend was observed for the variation of the volumetric liquid mass-transfer coefficient. The effect of pressure on kia was probably due to the influence of pressure on the interfacial area, a. In fact, by observing the ratio, kia/a, it can be seen that the liquid-side mass-transfer coefficient, kL, is independent of pressure. 

There are two mass transfer coefficients that are significant, the gas/liquid mass transfer coefficient and liquid to solid coefficient. If the gas is a mixture, the gas/liquid coefficient is more difficult to estimate. 

Gas-Liauid Hydrogen Transport. Using a dynamic method (ref. 15), the gas-liquid mass transfer coefficient I a for hydrogen into toluene was measured in the 50 ml reactor. The autoclave was pressurized to an initial pressure Pt and then stirring was staned. The rate of mass transfer as a function of time and in terms of P[ and the final pressure P2, is given by Equation 1. 

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