Effect of Slotted Anode on Gas Bubble Behaviors in Aluminum Reduction Cell
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E´ROULT cell is the main industrial application for the production of primary aluminum. In the present electrolytic aluminum production process (as shown in Figure 1), electrochemical reduction occurs in molten electrolyte at a high temperature about 1233 K (i.e., 960 C) with the direct current. Due to the electrolytic reaction, gas bubbles are generated at the bottom of the anode and the molten aluminum (metal) is deposited under the electrolyte (i.e., also referred as
MEIJIA SUN, BAOKUAN LI, LINMIN LI, JIANPING PENG, and YAOWU WANG are with the School of Metallurgy, Northeastern University, Shenyang 110819, Liaoning, China. Contact e-mail: [email protected] QIANG WANG is with the State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, Hubei, China. SHERMAN C.P. CHEUNG is with the School of Engineering, RMIT University, Melbourne, VIC 3083, Australia. Manuscript submitted January 17, 2017.
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bath) due to density difference. The gas bubbles also drive the circulation of the molten electrolyte, resulting in a better dissolution and diffusion of alumina particles. The convective heat transfer and current efficiency could also be improved between the bath and tank wall. On the other hand, a swarm of bubbles that accumulate at the bottom of the anode could form a continuous gas layer through bubble collision and coalescence process. Such gas layer or swarm of large bubbles could reduce the contact area between anode and bath. This would significantly affect the conductivity of the total cell and drive the cell voltage rise which eventually impact the electrolytic proceeding.[1,2] In recent years, some research works have been focusing on re-inventing the structure of cathodes and anodes to solve these problems and reduce the power consumption of aluminum reduction cell. Feng[3–5] proposed an innovative cathode in aluminum cell. Some industrial productions have been performed with the slotted anodes in aluminum cells. According to the data from industrial tests, the power is reduced to about 1000 kWh per tonne aluminum. Most of the aluminum
Fig. 1—Aluminum reduction cell.
companies have also attempted to implement the slotted anode in trail operation. It is generally accepted that the slotted anode can reduce gas coverage and gas bubble layer resistance.[6,7] The current work is to study the gas bubble behaviors with slotted anode in aluminum cell as well as to explore the mechanism of gas bubble removal and bath–metal interface fluctuation. Nevertheless, it is known that the direct measurement of flow field in aluminum reduction cell is difficult and inaccurate in the harsh operating conditions. Most physical experiments are done with limited considerations and the details of multi-physics fields such as electric field, magnetic field, etc., are not yet fully understood. Therefore, numerical simulation is adopted as an effective method to understand the complicated process in the aluminum reduction cell. There are some previous stud
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