Gas transfer and liquid dispersion inside a deep airlift reactor

Gas transfer experiments in bubbly flow are conducted inside a deep bubble column/airlift reactor containing air and water with a maximum aerated water height of 23.4 m and diameter of 1.06 m. The effects of geometry and operating conditions on mixing and gas transfer are determined. Fluorescence measurements are used to estimate dispersion coefficients for several operating conditions, while bubble-water gas transfer measurements are made using dissolved oxygen (DO) probes. A two-phase convection-dispersion model is fit to the DO measurements using the liquid film coefficient (kL) as a fitting parameter. Sparger differences had a substantial effect upon kL, and the gas transfer coefficient for the airlift reactor was four times that of the bubble column. Results are characterized using Sherwood, Reynolds, and Bond numbers. A low Reynolds number exponent was found, indicating that kL in a deep column tends toward a constant and is not highly dependent upon air discharge. © 2008 American Institute of Chemical Engineers AIChE J, 2008