An Integrated Approach to Identify the Total Recirculation Regime for a Gas–Liquid System in an Agitated and Sparged Tank Contactor

Abstract

Mass-transfer rates vary across hydrodynamic regimes in gas− liquid (G−L) systems in an agitated and sparged tank contactor (ASTC). Ideally, kinetics studies should be conducted in the total recirculation regime (TRR) representing intimate G−L contact, minimizing hydrodynamic limitations while offering optimum mass-transfer rates. Our earlier studies indicated the utility of gassed to ungassed power ratio (P g /P l ) as a means of identifying regimes. Continuing with our efforts, we have used a combined strategy of gassed to ungassed differential pressure ratio (Δp g /Δp l ) supported by P g /P l profiles to accurately identify the TRR and its point of transition to the flooding regime. We also demonstrate how the TRR offers an optimum interfacial area (S opt ) ideal for mass transport across the G−L interfaces. A standard ASTC of 0.25 m diameter (D T ) equipped with turbine impellers and ring spargers containing 10 L or 1 × 10 −2 m 3 water was used for our studies. The stirring rate (N 0 ) was varied from 1.67 to 41.67 rps for an oxygen flow rate (Q G ) of 7.5 NLPM or 12.50 × 10 −5 Nm 3 s −1 at a temperature (T) between 303 and 313 K under atmospheric pressure. This comprehensive approach offers a novel yet simple method for identifying the TRR, applicable to G−L kinetics studies in general and valuable in enhancing energy efficiency in chemical reaction engineering.