Local bubble size distributions, gas–liquid interfacial areas and gas holdups in a stirred vessel with particle image velocimetry

Abstract

Abstract Particle image velocimetry (PIV) was used to measure local bubble size distributions (BSD), gas–liquid interfacial areas, gas holdups and flow velocities simultaneously from a flat-blade turbine agitated 14 dm3 vessel. Air–water and CO2–n-butanol systems were investigated at several agitation conditions in order to find out the effect of physical properties on the vessel hydrodynamics. Dispersion was illuminated with a laser light sheet to minimise the blurriness in the images. The depth of field (DOF), needed in the calculation of local gas–liquid interfacial areas and gas holdups was obtained from the calibration experiments with a bubble gel. A simple method was developed to correct some bias errors of the measurement technique. Calibration experiments verified the need and the relevance of the developed correction. The measured BSDs varied reasonably with the measurement point in both air–water and CO2–n-butanol systems and were in agreement with the well-known correlations of Calderbank [P.H. Calderbank, Physical rate processes in industrial fermentation. Part 1. The interfacial area in gas–liquid contacting with mechanical agitation, Trans. Inst. Chem. Engrs. 36 (1958) 443–463]. The results show that local hydrodynamic quantities can be measured simultaneously with the PIV from a stirred vessel. This is a benefit, since more consistent experimental information is obtained for the validation of gas–liquid stirred tank simulation tools.