Liquid-side resistance in gas absorption



The film theory of liquid-side resistance to gas absorption, embodying the assumption of a thin stagnant liquid film adjacent to the interface in which steady state diffusion occurs, has long been open to question, particularly in packed columns. Higbie's penetration theory, believed to be more reasonable, pictures the liquid as flowing over a piece of packing for a very short period of time before being mixed as it flows to the next piece of packing. In the penetration model absorption occurs during a series of brief contacts, and unsteady state mass transfer conditions prevail in the liquid.

Several short glass-wetted-wall columns 1.9 to 4.3 cm. long were constructed to simulate the assumptions of the penetration theory. Because of the short length ripples were absent except when the gas rate was higher than ReG = 2,200. The desorption of carbon dioxide from water and of chlorine from dilute hydrochloric acid (0.16 to 0.18 N) was studied. The desorption rate of carbon dioxide was unaffected by gas velocity up to ReG of 2,200 and increased 1.1%/°C. over the temperature range of 22° to 31°C.