Influence of viscosity and surface tension on bubble dynamics and mass transfer in a model bubble column

The influence of viscosity and surface tension on bubble dynamics and gas liquid mass transfer has been examined experimentally in a model bubble column using optical measurement methods. Different glycerol-water mixtures, together with the surfactant sodium dodecyl sulphate (SDS), were analysed in this study. Thus the present study covers a viscosity range of 0.86…9.29 mPa⋅s and a surface tension range of 44.8…72.24 mN/m, accordingly, a Morton number range of 1.71 × 10−11…7.04 × 10−7. Shadowgraphy combined with PTV has been used to determine bubble size, velocity, and bubble shrinkage. The liquid velocity and the dissolved CO2 concentration fields have been analysed by particle-image-velocimetry (PIV) and laser-induced fluorescence (LIF), respectively. The bubble sizes and velocities obtained here show a good agreement with correlations proposed in the literature. With decreasing surface tension and decreasing viscosity, the bubble size is decreased but neither the addition of glycerol nor the addition of surfactant was found to be beneficial to mass transfer from the CO2 bubbles into the liquid. Due to the bubble size and velocity change in different mixtures, the liquid flow field is changed as well. The highest velocities could be found in the high viscosity solutions. The liquid velocity profiles are similar for different viscosities, except in the bottom section of the column where the bubble curtain is produced. These results support the existence of a dual effect of viscosity on bubble column fluid dynamics as already stated in the literature before.