Unsteady behaviour of bubble column in homogeneous flow regime: Startup and shutdown

The startup (engagement, EN) and shutdown (disengagement, DE) processes in the bubble column are investigated both experimentally and theoretically. Two horizontal interfaces, top and bottom, characterize the evolving bubble bed. Their motion is explored by measurements in a laboratory air–water bubble column operated in the homogeneous flow regime (HoR). The effect of two control parameters is determined: clear liquid height L and gas superficial velocity q. The following results are obtained: the trajectories of the top and bottom interfaces, the duration of the early and late stages of EN, the coordinate points of the typical events of the bubble bed dynamics, the bubble swarm velocities related to the interfaces, the characteristic time scales, the symmetry features of EN and DE processes, the parametric dependence on L and q. A simple mathematical model is suggested to describe and interpret the experimental data.

Fig. Evolution of liquid free surface and bubble bed during startup (engagement) and shutdown (disengagement) processes.

Ruzicka, M.C., Orvalho, S., Unsteady behaviour of bubble column in homogeneous flow regime: Startup and shutdown. Chemical Engineering Science 277, 118806, 2023. DOI: 10.1016/j.ces.2023.118806