Kinetics of Absorption of Gases with Low Concentrations from Gas-Air Mixtures

This paper presents studies of the kinetic regularities of physical absorption of gases (CO2, H2S, SO2, NH3) in a wide range of interphase distribution coefficients and phase motion velocities during the downward film flow of a liquid along the inner surface of vertical tubes, providing a "fixed surface" of interphase exchange. For gases with different solubility, some common tendencies were revealed for different gases. For the dependences of the absorption coefficient on the gas velocity, the general tendency is as follows: the absorption coefficient increases with an increase in the gas velocity to a certain value. At low gas velocities, it ceases to grow for low-solubility gases. It is of interest from both theoretical and practical viewpoints to examine the character of kinetic tendencies for the zone of the dependences of the absorption mass transfer coefficient on the gas phase velocity. Having reached a certain value at a given irrigation density, other process conditions being constant, the absorption mass transfer coefficient ceases to depend on the gas phase velocity. Based on the analysis of experiments, it can be concluded that the values of the absorption mass transfer coefficient for gases of different solubility under the same conditions depend on the equilibrium constants. Thus, for absorption of low concentrations, for which the process is not complicated by significant changes in the physical constants of the liquid during absorption, it is possible to obtain general kinetic dependences that are common to the absorption coefficients of gases of different solubility.