| Abstract:The distribution of temperature and electricity in aluminum reduction cell is always in a state of dynamic equilibrium, which influences the energy consumption of the electrolysis process and the life span of the cell. Thus, the online simulation of thermal-electric field is significant theoretically and practically for the real-time understanding of the distribution and variation trend of temperature and electricity in aluminum reduction cell and providing instructions for the adjusting of technology parameters to keep a steady and high-efficiency operation of the cell.According to the problems existing in current thermal-electric model, this thesis aims to simulate the online distribution of the thermal-electric field in aluminum reduction cell based on the distribution of anode current by improving the theoretical basis of the numerical simulation directly coupling the thermal-electric field in aluminum reduction cell, formulating efficient calculation methods of the side ledge profile and optimizing the calculating efficiency of the model. The main innovations and achievements are as follows:(1) Based on the analysis of energy budget, thermal-electric balance principle and the coupling relationship between electric field and thermal field of aluminum reduction cell, a thermal-electric model was set up, which considered the calculation of heat effect during electrochemical process, the interfacial heat transfer between melt and side ledge. Then, the model was used to calculate and analyze the thermal-electric field of a420kA aluminum reduction cell in ANSYS. And according to the structural characteristic of aluminum reduction cell, the calculation efficiency of the model was increased greatly by optimizing it on the geometry scale without reducing the computational accuracy.(2) On the basis of the optimization theory, the iterative calculation strategies of the3D side ledge profile were developed by using bisection method and golden section method respectively. Based on the model directly coupling thermal and electric field, the calculation accuracy and efficiency of these two strategies were compared with each other and with another strategy already published. The results show that, under the convergence criteria set in the process, these two calculation strategies of the side ledge profile based on the optimization theory achieve the same calculation accuracy and efficiency, and have less iterations thus more efficient than the calculation strategies of the side ledge profile already published.(3) The heat transfer between the slice model and the rest part of the cell was analyzed and a heat source was added in the melt to simulate that heat transfer. And according to the difference of heat generation rate in the melts between slice models with theoretically designed anode current and non-theoretically designed anode current, a iterative strategy was developed to calculate the heat generation rate of the heat source added in the melt of the slice model with non-theoretically designed anode current. And thus a model directly thermal and electric field based on the distribution of anode current was set up with respect to calculation accuracy and efficiency. Then, the model was used to calculate the thermal-electric field and side ledge profile of a420kA aluminum reduction cell with anode current varying from90%to110%of anode current theoretical design value in ANSYS. The results show that this model takes only33minutes to calculate the thermal-electric field and side ledge profile of the cell with a certain anode current value, and the distribution of the thermal and electric field and side ledge profile vary with obviously regular fluctuations under the change of anode current. |
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