SummaryThe effects of aeration on the flow characteristics of water in a glass pilot-scale airlift fermentor have been examined. The 55-L capacity fermentor consisted of a 15.2-cm-i.d.riser column with a 5.1-cm-i.d. downcorner tube. It was found that the average bubble size diminished with increased aeration. Typically, average bubble sizes ranged from 4.32 mm at a superficial gas velocity of 0.64 cm/s to 1.92 mm at 10.3 cm/s. A gas holdup of 0.19 was attained with superficial gas velocities (u,) on the order of 10 c d s , indicating the highly gassed nature of the fluid in the riser section of the fermentor. Circulation velocities of markers placed in the fermentor decreased with increasing aeration rates due to increased turbulence and axial liquid backmixing within the riser section. Actual volumetric liquid circulation rates remained relatively constant (0.36-0.49 L/s) for values of v, up to 10 cml s. Based on theoretical calculations, the ascending velocity of bubbles in a swarm reached 54 cm/s in the range of u, values studied.
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