Gas-liquid mixing performance of a non-Newtonian fluid in a multiple-impeller agitated tank

BACKGROUNDThis target is to decide power input and gas hold-up for gas-liquid mixing aqueous CMC solutions. The analysis considers the impact by varying the impeller speed and gas flow rates in a stirred tank bioreactor of three kinds of multiple impellers. The effects of the impeller type, rheology, and operating conditions were investigated on power drawn, relative power demand (RPD), gas holdup, and volumetric mass transfer coefficient.RESULTCompared to the Rushton turbine (6RT) and 4-pitch blade (4PBT) impeller, the propeller (3PP) impeller presented a minimal event of the gassing on the RPD. 4PBT impeller has shown a higher gas hold-up compared to the Rushton turbine and propeller impellers. The aerated agitated tank was established a dimensionless correlation for the RPD as a function of flow number and web number. Besides, the gas-liquid agitated system was also introduced a dimensionless correlation to compute the overall gas hold-up as a function of specific power consumption. For the maximum dispersion mixing intensity, the impeller structure with low RPD looks to be more adequate. Further, maximizing gas holdup in the structures with high RPD is advantageous. The effects of impeller speed, gas superficial velocity, and rheology on the volumetric mass transfer coefficient were examined.CONCLUSIONThe volumetric mass transfer coefficient increased with an increase in impeller speed, gas superficial velocity, and power consumption per unit volume and decreased as rheology increased. The averaged kLa for each multiple-impeller was correlated well with the specific gassed power consumption and gas superficial velocity. (c) 2024 Society of Chemical Industry (SCI).