Stirrerless Mixing of Liquids in Large Containers and Vessels

Jet mixing or gravity-driven mixing by rising gas bubbles can be applied for homogenization of liquids in tanks (→ concentration or temperature) or for shortstopping of reactions (injecting an inhibitor or a cooling/diluting liquid). Whereas the mixing efficiency of gas bubbles in large bubble column reactors at superficial gas velocities above 2 cm s⁻¹ is well-known, less information is available for significantly lower gas flow rates below 1 mm s⁻¹ (→ bubble plumes). This can be applied to enhance heat transfer for cooling down a stagnant liquid in a reactor after a shutdown. These mixing processes are reviewed and demonstrated by large-scale field tests. The application of the axial dispersion model to evaluate mixing times is discussed.