Oxygen transfer characteristics in a pilot scale surface aeration vessel with simcar aerator

The volumetric mass transfer coefficient, K_La, was determined by dynamic method in a surface aerated pilot scale squared vessel up to 0.531m³ equipped with Simcar type impeller. Through surface aeration, the oxygen transfer characteristics were investigated with the variations of operating variables such as stirring speed, impeller diameter, liquid height and power input per liquid volume (Po/V). It was seen from the results of different oxygen concentration absorption that the dynamic method might lead to errors in K_La when air was used for absorption. To provide reliable K_La values measured by dynamic, the K_La data using pure oxygen were used and confirmed with feeding steady-state method (FSM). As expected, K_La depends on Po/V, impeller size and liquid height. However, for Simcar type impeller, the K_La shows linear dependency on Po/V in contrast to majority of correlations reported in the literature which shows K_La ∝ (Po/V)^0.65 for disk type impeller. Moreover, it was interesting to find that the bubble behaviors inside the vessel computed by computational fluid dynamics (CFD) could explain qualitatively the K_La changes with operating variables. For the purpose of scale-up procedures, the empirical correlations for predicting K_La were developed within ±2% accuracy.