Experimental Study of Physical Absorption of Gases at Low Concentrations with Different Solubilities

This paper presents the experimental studies of kinetic tendencies in the physical absorption of gases (CO₂, H₂S, SO₂, NH₃) in a wide range of phase velocities during the downward film flow of a liquid along the inner surface of a vertical tube. In each experiment, the temperature of the gas and liquid was maintained constant by passing them through the coils submerged in thermostatted vessels. The amount of absorbed gas was determined by analyzing the concentration of the component in the gas–air mixture before and after the apparatus and by control analysis of the liquid leaving the apparatus. For further reliability of gas concentrations obtained by chemical analysis of the initial and final gas–air mixture, the liquid concentration after the apparatus was also determined in a number of experiments. Empirical dependences of the mass transfer coefficient (K_OG) on the gas velocity (V_g) were obtained. The discrepancy between the experimental data on absorption in many cases does not exceed 10%. Based on the experimental data, it can be noted that the K_OG values for CO₂, H₂S, and SO₂ in the first region, where they increase with the gas velocity, coincide with K_OG for ammonia obtained at the same V_g, which is associated with the prevailing gas phase resistance to the substance transfer under these conditions. For poorly soluble gases, however, the phase resistance ratio transforms already at relatively low gas velocities. In this case, the mass transfer coefficient, which is independent of V_g, changes with the irrigation density.