Investigation of bubble behaviour at cryolite melt - alumina slurry electrolysis

Physical modeling of oxygen bubbles generated on the inert anode as a result of electrochemical evolution at cryolite melt - alumina slurry electrolysis movement, growth and evacuation results are presented in the paper. Similarity criteria are calculated, experiments are performed on two types of cell: for three phase flow at vertical electrode observation from front and side views. The behaviour of bubbles in slurry was recorded. For the model, an 20 % aqueous solution of sulfuric acid with 30 vol. % of alumina was used. Current density range was 0.05 to 0.25 A/cm 2 . Bubble behavior information allows estimating the ability of effective gas evacuation from the inter-electrode space during slurry electrolysis. The highest bubbles vertical speed (2.5 cm/s) was reached at 15 to 20 cm depth from the electrolyte - atmosphere border, after which the speed was reduced. Bubble layer thickness does not exceed 2.2 mm. Bubble’s average growth rate was 2.68 mm 3 /s.