Oxygen transfer in a multiple air-lift loop reactor

The Multiple Air-lift Loop reactor (MAL) is a new type of bioreactor, in which a series of airlifts with internal loops is incorporated into one vessel. As such, the MAL is an approximation of an aerated plug-flow fermenter. Gas/liquid oxygen transfer was studied as a function of the gas flow rate in a MAL. The second MAL-compartment in the series was investigated in particular, and a Rectangular Air-lift Loop reactor (RAL) was used as a reference. Both a dynamic and a steady-state method were used for the determination of the overall volumetric oxygen-transfer coefficient. Both methods gave the same results. The oxygen transfer coefficient in the second MAL-compartment was low compared to that of conventional internal-loop reactors. Wall effects probably caused bubble coalescence and a reduction in the oxygen transfer. For the RAL it was found that oxygen transfer was comparable to that in a bubble column.