Influence of gas distributor design on the oxygen transfer characteristics of an airlift fermenter

The performances of two types of gas distributor (a perforated ring and a porous plate) in an airlift fermenter were compared in the measurement of gas holdup, overall mass transfer coefficient and mixing time, using four aqueous media containing different concentrations of four electrolytes, sugar and antifoam agent in order to simulate fermentation media. In pure water, a 50% higher kLa value was found with the porous plate; this difference was emphasized by adding salts or organic compounds so that the kLa could become two or three times higher with the porous plate. The type of sparger seemed to have very little effect on holdup ratios and mixing times.