| Aluminum reduction cell is the heart of the aluminum industry. Its developments and advancements represent improvements of aluminum reduction technologies. The behavior of anode bubbles has a significant influence on the transfer of mass and heat in aluminum electrolysis, as well as increaseing the voltage drop of electrolyte and affecting the distribution of anodic current density. In addition, the bubbles’ transportation can influence the flow field of aluminum electrolysis cell, improve alumina dissolution and diffusion, uniform the temperature and concentration gradients, promote heat exchange between electrolyte and ledge. However, it also may lead to the fluctuations of molten aluminum ped, which cause the instability of aluminum reduction cell and the possibility of re-oxidation of aluminum, finally reduce the current efficiency. Therefore, It is very important to study the behavior of anode bubbles.In this paper, a high temperature transparent cell was used to simulate the industrial electrolysis cell, graphite anode and cathode was used to simulate industrial electrode。 Base on the see-through cell experiment, physical model and mathematical model for bubbles and electrolyte flow were established based on the FLUENT stage by means of appropriate simplification. Behavior of carbon dioxide free bubbles, the behavior of anode bubbles and the electrolyte flow field due to anode bubble were simulated. Contact angle, surface tension and other parameters were explored. Simulated results were analyzed and verified by high temperature transparent cell experiments and other literature results.The main research contents and results are as follows:(1)In this paper, carbon dioxide bubble’s generation, grow up, escape and other acts were simulated. It was found that the time for bubble size generation-grow up is longer than its escape. its escape is very quick, just only0.04seconds. When the bubble size grows to around5mm hemispherical, it begin to longitudinal growth due to buoyancy, gravity, surface tension. Finally the bubble escape. In this process, the bubbles act like an oval-shaped cap, the maximum diameter is about10mm. The process peried is about0.8s. The results were verified by a transparent cell with good agreement.(2)In this paper, anode palm bubble’s generation, grow up, escape and other acts were simulated. It was found that anode gas generated as points in the anode palm. the little bubbles begin merging and forming a thin bubble layer when the bubbles grow to1～2mm, the bubble layer’s thickness is growing up with time. When the maximum thickness of bubble layer reaches5～6mm, the gas escape from the palm to the side of anode. The side bubble grows up and reaches10～15mm, all anode palm gas move to the anode side and finally escape out of the electrolyte. This process peried is about5s. The results were verified by transparent cell with a good agreement.(3)In this paper the electrolyte and gas flow field due to the effect of anode bubbles was simulated. It was found through simulation the maximum electrolyte velocity distribution at the anode side and the surface of electrolyte, reaches to0.38m/s which is close to Feng Yuqing’s simulation results, the minimum velocity distribution at the center channel where a oval-shaped vortex was found, and alumina focus in this area. Bubble layer mainly locates in the anode palm and anode side area. The volume fraction of gas may reach up to100%on the anode palm. Parts results were verified by transparent tank with good agreement.The has been verified model is benefit to simulate larger-size high temperature cell and industrial aluminum reduction cell. |
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