Hydrodynamics of gas bubbles in the gap of lantern blade electrodes without forced flow of electrolyte: Experiments and CFD modelling

Gas-liquid flow is of prime importance in multiphase processes, in particular in electrochemical cells for which generated gas enhances the ohmic drop and the energy consumption. The present investigation was aimed at investigating the hydrodynamics of electrogenerated oxygen bubbles in a process still in development for iron electrodeposition in alkaline solutions; the lantern-blade configuration of the pilot anode was emulated by facing parallel anodes in a laboratory cell without forced circulation of the liquid. Distributions of bubble velocities and void fractions in the anode-to-anode space were determined through experimental observations and CFD simulations to investigate the behaviour of gas bubbles in the anode gap. The effects of the anode gap, current density and cell inclination on the hydrodynamics of the gas phase were followed. Predicted gas velocity near the anode wall was validated by experiment. However, CFD showed that a negative lift coefficient is required for simulations in order to reproduce the experimental dispersion of the bubbles curtain: wall and repulsion forces that were not taken into account in the model might play a major role in the expansion of the bubble swarm.