Gas–Liquid Mass Transfer Characteristics in Two Inline High Shear Mixers

The mass transfer characteristics of a gas–liquid continuous flow system accompanied by reaction in two commercial inline high shear mixers (HSMs) were evaluated by the sulphite oxidation method. The gas–liquid specific interfacial area, a, and the volumetric mass transfer coefficient, kLa, were measured under different operating conditions involving the rotor speed, the liquid flow rate, the gas flow rate and the surface tension. The results indicate that a and kLa increase with the rotor speed and liquid flow rate due to an increase of turbulence intensity. Both parameters increase slightly first but then decrease with the gas flow rate. For either the dual rows ultrafine-toothed or the single-row blade-screen configuration of HSMs, a increases while kLa decreases with the surfactant concentration, and both of them tend to be changeless at the surfactant concentration higher than 30 mg/L. Correlations for the specific interfacial area and the Sherwood number are obtained to guide the process design and scale-up of both types of inline HSMs.