Study On Thermal-Electric-Stress Field And Sodium Expansion In Aluminum Reduction Cell

Aluminum reduction cell(ARC) is one of the main equipment of industrial aluminum producing. In the process of producing aluminum, the multi-physical fields in ARC are very complicated. It is of great significance to study the multi-physical field in the ARC, which is helpful to guide the design of the aluminum reduction cell and increase the current efficiency and the life of the aluminum reduction cell.In this dissertation, three kinds physical fields in ARC, including the electric field, thermal stress field, and sodium expansion stress, were carefully analyzed using the finite element software ANSYS. Some typical working conditions during the operation of the cell such as heating up were also considered. Main works and results are as follows:(1) A thermal-electric coupled model for the whole cell was established. In order to accord with the actual situation, the height distribution of the anode carbon block, the heat absorption of the chemical reaction and so on were considered in this model. The temperature distribution in the cell in the normal production state and the heat flux distribution were computationally obtained, showing a good agreement with the actually measured results and thus validating this computational model.(2) A thermal-stress-sodium expansion coupled calculation model was established, and a method, which was based on the similarity between the heat transfer and the sodium diffusion, was suggested to calculate sodium diffusion. Then the stress field under thermal expansion and sodium expansion was calculated. This model, which considered the material nonlinearity, the contact nonlinearity of friction and the thermal shrinkage effect of some heat insulation lining, gave results with good agreements with the actually observed results.(3) A transient thermal-electric field calculation model was established and then the temperature change in the cell when changing anode carbon block was simulated. The results showed that temperature of the electrolyte near new anode decreased significantly. Precipitation or coagulation cloud be formed on the surface of new anode block, and the temperature of electrolyte would recovery after 13 hours.(4) A transient thermal-electric field calculation model for extracting aluminum operate of aluminum reduction cell was established, where the heat income change brought by the change of polar distance was considered as energy. The results showed that the temperature changes brought by extracting aluminum operate was relatively small, thus would not cause significant impact on the energy balance of the cell.(5) The thermal field and thermal-stress field of aluminum reduction cell under different covering material thicknesses were calculated. The results showed that temperature in the cell increased 11? when the thickness of covering material increased 2cm; and the impact on stress and displacement brought by variety of covering material thickness was not significant.(6) A model for the transient thermal-electric field and the thermal-stress field calculations during the heating-up operate was established, and the temperature change and the thermal stress in the cell after the baking process were calculated. The results showed that the temperature gradient around the cathode carbon block was relatively large, and the strain at the bottom corner of the cell was about 1.99%, and thus the cathode carbon block was easy to crack when the temperature was too high.