Quantifying Air Entrainment at the Gas-Liquid Interface in Stirred Tank Reactors

Air entrainment, or surface aeration, is a critical phenomenon in mixing processes that promote the development of a multiphase flow. It can either disturb the yield of a process by enhancing oxidation or promoting separation of low-density substances in a mixture. In this study, a standard stirred tank reactor (STR) with a Rushton-type impeller is used to analyze air entrained at the air-water interface. Both impeller speed and clearance beneath the surface play a major role in the quantity of air entrained in the system. High-speed backlit imaging is used to visualize and quantify air entrainment. It will be shown that the interplay between rotation speed and clearance depth is complex. Future characterization methods will also be discussed that will quantify air entrainment volume.