Local power uptake in gas-liquid systems with single and multiple rushton turbines

Prediction of the power uptake of impellers is crucial for a successful scale-up, operation, and design of stirred tank reactors (STR). However, for gas-liquid systems equipped with multiple impellers, commonly used in industry, information on the local power uptake is scarce in literature. For single-impeller stirred vessels, inconsistency between the experimental data on power uptake under gassed conditions and available relations in literature is often reported. In this paper empirical correlations on the local gassed power uptake of impellers are derived both for single-impeller and multi-impeller systems, based on a large body of experimental data from literature. Under gassed conditions the bottom impeller of a multiple impeller configuration or a single impeller draws relatively less power than an impeller in the middle or at the top. The power uptake by impellers in a gassed STR shows two regimes. It is found that middle and top impellers reach their second regime at a much higher gas flow rate than single or bottom impellers under the same conditions.