Impact of Curved-Blade Impellers on Gas Holdup and Liquid Homogenization Dynamics in Stirred Tanks

Design and optimization of aerobic fermentation processes in stirred tanks must factor in specific features, such as the formation of gas cavities on the rear of impeller blades and the need for high power input. Here, the ability of a curved-blade impeller to reduce these drawbacks, which are typical of flat-blade impellers, is investigated. The analysis is based on gas holdup distributions and liquid homogenization dynamics collected by electrical resistance tomography in a pilot-scale stirred tank of geometry similar to typical industrial aerated fermenters. A wide range of gas flow rates and impeller speeds in single-impeller and multiple-impeller configurations are considered and the differences arising when a Rushton turbine is replaced with a Bakker turbine are discussed.