Current density distribution and gas volume fraction in the gap of lantern blade electrodes

• Improved design of gas-evolving anodes formed by parallel flat blades.
• Model for prediction of current density distributions.
• Use of segmented electrodes for determination of local current density.
• Determination of gas holdup by use of high-speed camera.
• Comparison of experimental and theoretical current distributions.

Electrochemical processes involving gas evolution at appreciable rates have been optimized in their design for the sake of reduced energy consumption. The present investigation was conducted in view to reducing the energy demand of a pilot process for electrolytic reduction of hematite particles to iron metal; attention was paid at the design of the lantern blade anodes where oxygen evolution occurs. An experimental cell consisting on two facing anodes and two remote cathodes has been designed and used for investigation of the gas behavior and current density distribution at the anode blades. The model for prediction of secondary distributions was validated by measurement of the currents at the segmented anodes and the effects of the average current density and the anode gap could be observed. The model was finally applied to the pilot cell for iron production; as expected, larger gaps allow more uniform current distributions at the anode, however without reducing the cell voltage. In contrast, blade lengths in the order of 10–15 × 10−3 m only would allow visible reduction in the cell voltage.