Abstract
The evolution behavior of anode gas during aluminum electrolysis has been a hot spot of research for energy saving and process control. In the present work, the bubble evolution behavior during aluminum electrolysis was investigated using a lab-scale see-though cell. The bubble evolution characters on an 11 cm2 (bottom surface area) flat anode, an 11 cm2 slotted anode, and a 50 cm2 flat anode were investigated with statistical analysis, respectively. The results showed that bubbles tended to generate and adhere to certain regions on the anode surface due to the heterogeneity of the carbon material, and the adhering regions moved when current density was increased. The anode slot lowered the actual current density on the anode significantly by reducing the anode bubble coverage. Influenced by the group effect of bubbles, the 50 cm2 flat anode behavior constituted a lower bubble coverage rate, lower average bubble size, and lower actual current density than the 11 cm2 flat anode.
Highlights
The Hall–Héroult electrolytic process is the most common technology for primary aluminum production nowadays
The bubble evolution behavior on aluminum electrolysis anodes was observed in a see-through cell
For the three kinds of anode as investigated in this work, with the increase in apparent current density, the size of the bubbles that adhered to the anode bottom surface showed an overall decreasing trend, indicating a faster generating rate and faster releasing rate of the bubble under a higher current density;
Summary
The Hall–Héroult electrolytic process is the most common technology for primary aluminum production nowadays. In this process, the raw material—alumina—is fed into the molten cryolite-based electrolyte at the temperature of 920–960 ◦C. Carbon is used as both anode and cathode material and the direct current goes through the anode to the cathode. As the electrochemical reactions take place, liquid aluminum is reduced at the cathode and deposited at the bottom of the cell, creating a separate fluid layer between the carbon cathode and the molten electrolyte, where the liquid aluminum layer behaves as the actual cathode [1,2]. The bottom surface of the anode is the main interface for the anodic reaction [2,3]:
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