Time-dependent gas hold-up and bubble size distributions in a gas—highly viscous liquid—solid system

The accumulation of small bubbles during the aeration of suspensions of a solid in a highly viscous liquid has been investigated. It was found that bubble size distribution is dependent on aeration time. Displacement of the maxima in the direction of smaller bubble diameters occurs during the aeration time and the maxima becomes higher. The distribution curves do not change after an “establishment time”. After this time, the small bubble hold-up and the total gas hold-up reach their final values. The contribution of small bubbles to the gas volume in the dispersion reaches about 60%, and depends on the liquid viscosity, the gas flow rate and the solid loading. The course of the small bubble accumulation process is described by the first order kinetic equation. The accumulation rate constant was found to be dependent on the superficial gas velocity and the apparent suspension viscosity.