Transfer Coefficients and Interfacial Areas in Absorber Scale-Up

Mass-Transfer Coefficients and Interfacial Areas in Absorber. Scale-up 

The choice of a suitable reactor for gas-liquid reaction or absorption is very often a question of matching the reaction kinetics with the capabilities of the proposed reactor. The specific interfacial area a, liquid holdup /3, and mass-transfer coefficients ki and k (or kifl and k fl) are the most significant characteristics of a reactor. A synthesis of published values of the mass-transfer parameters will be given in this section. 

Our objective here is to try to answer the following questions For a proposed type of gas-liquid contactor compatible with the properties and flow rates of the phases and with the reaction type, what are the likely values of the specific interfacial area and the gas and liquid mass-transfer coefficients by which the contact performance can be predicted And what is the expected accuracy of these values Table XVIII gives typical values of these parameters in typical contactors shown in Fig. 12 for fluids with properties not very different from those of air and water (especially, liquid viscosity under 5 cP where the liquid is nonfoaming). Because this review is especially concerned with the chemical method of determining these parameters, experimental data obtained by this method will be given in subsequent tables and figures. 

Packed columns are used conventionally to obtain a low pressure drop or low liquid holdup when there is practically no heat to remove or supply or when the gas or the liquid is corrosive. They are not used when solids are present in the feed or are formed in the reaction. Although packed columns or reactors can be operated cocurrently, their operation is usually countercurrent. In particular, countercurrent use is preferred when a higher concentration driving force is needed, that is, for distillation or for most physical absorption. However, when irreversible reaction occurs between dissolved gases and the absorbent, the mean concentration driving force is the same for both modes of operation. In this case the capacity of cocurrent columns is not limited by flooding, and at any given flow rates 

Mass-Transfer Coefficients and Effective Interfacial Areas in Gas-Liquid Reactors 

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IV. Mass-Transfer Coefficients and Interfacial Areas in Absorber. Scale-Up. .. 67... 

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