Design and characterization of a multistage, mechanically stirred column absorber

Abstract A multistage, mechanically stirred column absorber has been designed and built with a modular construction, based on preliminary experiments with a test column. The column has been characterized as a gas-liquid contactor by its gas holdup, gas and liquid axial dispersion, mixing times, oxygen transfer coefficients and power consumptions, determined as a function of gas velocity, liquid velocity and impeller speed for one and two impellers per stage. Gassed power was correlated with ungassed power, gas rate and impeller speed. The gas phase axial mixing was essentially plug flow and the liquid phase axial mixing varied between 5 and 12 equivalent stages. Oxygen transfer coefficients were correlated with power consumptions and aeration rates by the equation K L a γ (P/V) a (υ sg ) b . The oxygen transfer coefficients with single stiffer stages were 25% above those for the double stirrer stages for equal power consumption and gas rates. Except for the low aeration and high power consumption extremes, the column showed superior oxygen transfer performance. in comparison to tubular loop and tank fermenters.