Oxygen transfer in mechanically agitated aqueous systems containing dispersed hydrocarbon

Publisher Website
Google Scholar
Abstract
The effect of dispersed n ‐dodecane or n ‐hexadecane on the air‐to‐aqueous phase overall volumetric oxygen transfer coefficient in a simulated (cell‐free) stirred‐tank fermentor is described. The oil volume fraction ranged from zero to 0.10; the ionic strength of the aqueous phases was varied from 0 to 0.45. The air‐to‐aqueous phase coefficients in both oil‐free (KLa) and oil‐bearing (KLa*) systems were evaluated from unsteady‐state experiments using a membrane‐covered probe to follow the aqueous phase dissolved oxygen tension.For all systems studied, KLa*/KLa was found to be independent of P/V and vs for all practical purposes. However, for a particular aqueous phase and at a given P/V and vs, the ratio KLa*KLa generally differed from unity. Depending on the combination of hydrocarbon type and volume fraction and the aqueous‐phase ionic strength employed, the dispersed hydrocarbon may, in some cases, reduce the rate of oxygen transfer and in others enhance it relative to that of the corresponding oil‐free gas–liquid dispersion. Enhancement of the air‐to‐aqueous transfer rate by such negative spreading coefficient hydrocarbons has not been reported previously.