The gas evolution is one of the key factors for alumina distribution in bath and current efficiency in aluminum electrolysis cell using vertical inert anodes. A see-through cell is presented to investigate the gas evolution and releasing behavior with big inert anode. The test results show that with small anode

the bubble behavior of nucleation

growth and detaching periodically occurs on surface of big anode. However

the sliding and coalescence behavior on big surface is different to that on small anode. At working face of the anode

however

multi layers of bubbles are formed. The bubbles adjacent to the anode are moving fast than those at the outer layer. Most of bubbles go directly into the atmosphere at the liquid surface

while the remaining bubbles are carried by the electrolyte to move horizontally and they are released gradually. There is a bubble foam layer on the electrolyte surface. The moving velocity of bubble generated at inert anode is measured by image processing

which is in the range of 0.006-0.445 m·s-1. The bubbles at the bottom have a wide velocity range

while the bubbles at the middle have a narrow velocity range under the influence of the electrolyte.