Studies On Current Distribution In Aluminum Reduction Cells

The current industrial aluminum cell control system derives the change in electrolyte resistance based on the series current and cell voltage signals,which in turn controls the alumina feed,heat balance and tank stability.However,in the past 10 years,the capacity of the electrolytic cell has increased substantially,the size of the electrolytic cell has increased,and the number of anodes has increased.The spatial variation of the electrolytic cell dilutes the resistance control signal.For example,the change of single or several anode currents is not recognized in the groove voltage signal,so the existing control strategy is not ideal for controlling the large-scale electrolytic cell.For this reason,new control systems require information such as zone or single anode performance,local alumina feed control,etc.,that is,current signals that need to be included in each zone or anode on the cell.However,the accurate acquisition of the anode current signal is still a difficult problem to be solved in the current aluminum electrolysis industry.In this thesis,the bus bar,anode and cathode currents of 400kA aluminum cells were measured by fiber-optic current sensor.The variation trend and distribution characteristics of the cells were analyzed.The influence of anode replacement on the current distribution of the cell was investigated.The current data analysis of the single conductor shows that the bus current of the column is not sensitive to the change of the cell condition,and the current coefficient of variation is smaller than the anode current;the anode current will show different time in the normal channel and anode effect.And frequency response,and it is very sensitive to the occurrence of anode effect,which is different from the conventional anode current 30s before the anode effect occurs.Based on this feature,early prevention of anode effect can be achieved;cathode current is compared with anode current The peak characteristics in the frequency domain are relatively simple,without complex background peak interference,and periodic current fluctuations in the time domain,can easily find the corresponding frequency information in the frequency domain.The current distribution between the busbars of the column shows the distribution characteristics of the aluminum end,the flue end height and the middle low,and the current distribution is stable;the current distribution between the anodes in the electrolysis cell is not uniform due to the different working life cycle;At the anode current,the current distribution between the cathodes is relatively uniform.The current distribution between the column busbars is not sensitive to the pole-changing operation,and the current distribution is relatively stable during the production process;the effect of the pole-changing on the anode current distribution is relatively large,especially for the anodes in the region and adjacent regions.The two factors that have the most significant influence on the amount of change in anode current are screened by analysis of variance,which are the current carrying the anode and the region where the anode is located.Regression analysis was used to establish a mathematical model of the change of the anode current caused by the change of the anode current with the magnitude of the current carried by the anode before the pole change and the area of the anode.It was found that the increase of the anode current in the adjacent region of the anode was the largest,and the region was second.