Hydrodynamics in rectangular air‐lift reactors: Scale‐up and the scale‐up and the influence of gas‐liquid separator design

Experiments were conducted on air‐lift reactors with different liquid volumes, aspect ratios, and gas‐liquid separator configurations, with constant downcomer to riser cross‐sectional area ratio and riser/downcomer height. Reactor performance was highly dependent on the gas‐liquid separator design. By changing the latter, the mode of operation could be changed from that of a concentric tube reactor (with gas recirculation) to an external loop reactor (without gas recirculation). Liquid velocity and overall gas hold‐up data were correlated to the power per liquid volume and “Disengagement Ratio”, a geometric parameter describing the separator's configuration. During scale‐up, similar gas hold‐ups and liquid velocities were found in laboratory and pilot reactors. A modified air‐lift reactor with an enlarged channel for a gas‐liquid separator also was studied.