Side mass transfer coefficient

Here, kg and ki are the gas-side and liquid-side mass transfer coefficients. Their units are identical to those for Kg and Ki, m/s. Like the overall coefficients, they are usually measured and reported as the composite quantities kgAj and kiAi with SI units of s. ... 

SAHAY, B. N. and SHARMA, M. M. Chem.Eng. Sci. 28 (1973) 41. Effective interfacial areas and liquid and gas side mass transfer coefficients in a packed column. 

Fortunately changes in k,a due to mass transfer enhancement from ozone decay can be neglected, as Huang et al. (1998) showed by example of cyanide ozonation in strongly basic solutions (pH = 12-14) in a system where the value of the purely physical liquid side mass transfer coefficient was not too low (kL° > 0.03 cm s l). This is supported further by the results from several ozonation experiments, which showed that no ozone decay occurs in the liquid film at lower pH values (phenol, pH = 10 (Metha et ah, 1989) 4-nitrophenol, pH = 8.5 (Beltran et ah, 1992 a)). 

The second section presents a review of studies concerning counter-currently and co-currently down-flow conditions in fixed bed gas-liquid-solid reactors operating at elevated pressures. The various consequences induced by the presence of elevated pressures are detailed for Trickle Bed Reactors (TBR). Hydrodynamic parameters including flow regimes, two-phase pressure drop and liquid hold-up are examined. The scarce mass transfer data such gas-liquid interfacial area, liquid-side and gas-side mass transfer coefficients are reported. 

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 is practically nothing about the high-pressure liquid-side-mass transfer coefficient, ku in TBR in the open literature. The only paper published was that of Lara-Marquez et al. [57], The values of kia are determined by using the following chemical absorption systems in the slow reaction regime ... 

Regrettably, for our knowledge there is a lack of information in the open literature on values of the gas-side mass-transfer coefficient, k( , in TBR operating at elevated pressures and especially on the effect of the gas density on it. 

N. Midoux, B.I. Morsi, M. Purwasasmita, A. Laurent and J.C. Charpentier, Interfacial area and liquid-side mass transfer coefficient in trickle-bed reactors operating with organic liquids, Chem. Engng. Science, 39 (1984) 781-794. 

The design of packed column reactors is very similar to the design of packed columns without reaction (Volume 2, Chapter 12). Usually plug flow is assumed for both gas and liquid phases. Because packed columns are used for fast chemical reactions, often the gas-side mass transfer resistance is significant and needs to be taken into account. The calculation starts on the liquid side of the gas-liquid interface where the chemical reaction rate constant is compounded with the liquid side mass transfer coefficient to give a reaction-enhanced liquid-film mass transfer... 

Gas-liquid interfacial area per unit volume of dispersion a = 195 m2/m3 Liquid-side mass transfer coefficient kL = 2.5 x 10 4 m/s... 

From Fig. 4.3 it may be seen that this value, although smaller than that in Example 4.2, is still sufficiently large for all the reaction to occur in the film. Also the concentration of dissolved C02 at the interface in contact with the incoming gas containing C02 at a partial pressure of 0.001 bar will be only 0.001/., i.e. 0.001/25 4 x 10"5 kmoi/m3 which is much less than 0.05 kmol/m3, the concentration of the OH- ion, so that the reaction will still behave as nseudo first-order. The enhanced liquid-side mass transfer coefficient kl will thus be k[ V(9.5 x 103 x 0.05 x 1.8 x 10 9) 0.925 x 10 3 m/s. 

By applying the Lewis number prediction (hG/kCs =1), where k is the gas side mass transfer coefficient, and using Equation 5.29, we get... 

L liquid-side mass transfer coefficient measured by oxygen absorption, ms-1... 

The rate constant of Reaction (Rl) (the slowest and hence the most important reaction in the system) according to Ref. 132 The liquid-side mass transfer coefficient according to Ref. 133 The gas-side mass transfer coefficient according to Wehmeier (see Ref. 134)... 

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