Static Mixing in Fermentation Processes

Abstract

In order to improve transfer processes in bioreactors in the absence of mechanical impellers, which consume energy and develop high shear stresses, considerable efforts have been made to study all the prerequisites of the major relationship among flow, mass, and heat transfer over motionless mixers such as plates, cylinders, baffles, and spheres, as well as through sieves and trays. In recent decades, new constructive types of internals known as static mixers have been developed, which offer spectacular increases in transfer rates. An overview of the published results on fluid flow through various static mixer structures, their mixing, residence time distribution, and transfer process (momentum, heat, and mass) performance, examined both in single and multiphase systems by considering conventional and new and modern methods of investigation is presented in the chapter. Depending on the specific design and application, static in‐line mixers are able to promote continuous radial mixing, together with an effective degree of plug flow, while ensuring uniform and short residence times. It has been found that static mixers are able to change the velocity fields inside a tube and their effects are the consequence of specially designed flow arrangements, displacement and distortion, cutting and twisting, or separation and expansion based on the energy extracted from the fluid flowing through the mixers. The chapter emphasizes that static mixers can be applied regularly in multiphase turbulent flow and they can meet industrial requirements not only for biotechnological processes (fermentation, in particular), but also for absorption, reaction, extraction, and heat transfer/phase change.