Optimization Of Insulation Structure For 8kA Rare-earth Electrolytic Cell

Rare earth electrolytic cell is an important equipment for the preparation of rare earth metals by molten salt electrolysis.Small and medium-sized rare earth electrolytic cell occupies a dominant position in industrial production due to its advantages of low input cost,easy operation,easy adjustment and high separation purity.After years of development,the electrolytic production process of small and medium-sized rare earth is relatively mature,but there are still problems such as high energy consumption,low electrolytic efficiency and small output.It is an important research direction to optimize the structure of small and medium-sized rare earth electrolytic cell and improve the electrolytic efficiency of rare earth electrolytic cell.This paper takes an 8k A rare earth electrolytic cell of an enterprise as the research object to optimize the thermal insulation structure of the cell.The specific research contents are as follows:(1)According to the current 8k A rare earth electrolytic cell structure,construct a three-dimensional structure model of rare earth electrolytic cell,consult relevant information,determine the boundary conditions and related parameters of rare earth electrolytic cell,and establish the electrothermal coupling model of rare earth electrolytic cell.The insulation layer of the current rare earth electrolyzer is composed of insulation brick and insulation asbestos.The insulation asbestos in the existing rare earth electrolyzer is removed and the insulation layer of the current rare earth electrolyzer is redesigned.By consulting relevant literature,the electrolytic temperature range of rare earth was obtained.Through the temperature field simulation of the electrolytic cell,the value range of the insulation layer thickness of the electrolytic cell was obtained from 66mm to 86mm,and the values were respectively taken within the range.The distribution of electric heating field in the electrolytic cell electrolytic region under different insulation layer thickness was obtained through simulation.The analysis of electric heating field shows that the temperature of electrolytic region increases with the increase of insulation layer thickness.When the thickness of the insulation layer of the electrolytic cell is 78mm,the current density of the cathode surface in the electrolytic region reaches the maximum value of 3.261×10~4A/m~2,and the maximum potential reaches the minimum value of 9.974V,and the electrolytic cell electrolytic efficiency is the highest.Therefore,it is concluded that the optimal insulation layer thickness of rare earth electrolyzer is78mm.(2)The analysis of the temperature field in the electrolytic region of the rare-earth electrolytic cell under the optimum insulation layer thickness found that the temperature difference between the molten salt electrolyte and the graphite crucible was too high.The graphite crucible structure of the electrolytic cell was modified into the improved graphite crucible structure(L=10mm),and the improved graphite crucible was used to form the improved rare earth electrolytic cell.By comparing the temperature distribution between the rare-earth electrolytic cell and the improved rare-earth electrolytic cell,it is found that the improved graphite crucible can not only effectively reduce the temperature difference of molten salt and electrolyte between the graphite crucible and the graphite anode,but also reduce the temperature difference of molten salt and electrolyte between the anode and cathode.(3)Gradually increase the length of the improved graphite crucible L.With the increase of the length of the improved graphite crucible L,the temperature difference of molten salt electrolyte between the graphite crucible and the graphite anode gradually decreases,and the temperature difference of molten salt electrolyte between the anode and cathode first decreases and then increases.When the length of the improved graphite crucible L is 30mm,The temperature difference of molten salt and electrolyte between anode and cathode reaches the minimum value,and the temperature difference between anode and cathode is the main electrolytic region.The smaller the temperature difference between molten salt and electrolyte in this region,the more balanced the electrolysis,the higher the utilization rate of graphite anode,and the greater the electrolytic efficiency.Therefore,the optimum length of the improved graphite crucible L is 30mm.(4)The improved rare-earth electrolytic cell is composed of an improved graphite crucible(L=30mm).The maximum temperature of the improved rare-earth electrolytic cell exceeds the optimal temperature range for rare-earth electrolysis,and the thickness of the insulation layer of the improved rare-earth electrolytic cell is reduced to reduce the temperature of the improved rare-earth electrolytic cell.When the thickness of the insulation layer of the improved rare-earth electrolytic cell is 62mm,the temperature between anode and cathode of the cell is within the range of the optimal temperature for rare-earth electrolysis,the current density of the cathode surface reaches the maximum 3.857×10~4A/m~2,and the maximum potential reaches the minimum 9.435V,and the electrolytic cell electrolytic efficiency is the highest.Therefore,it is concluded that the optimum insulation layer thickness of the improved rare-earth electrolyzer is 62mm.(5)By comparing the distribution of electric heating field between the rare-earth electrolytic cell and the improved rare-earth electrolytic cell under the optimal insulation layer thickness,it is found that the temperature distribution in the electrolytic region of the improved rare-earth electrolytic cell is more reasonable than that in the electrolytic region of the rare-earth electrolytic cell,and the current density on the cathode surface of the improved rare-earth electrolytic cell is greater than that of the rare-earth electrolytic cell.The maximum potential of the improved rare-earth electrolytic cell is less than that of the rare-earth electrolytic cell,and the electrolytic efficiency of the improved rare-earth electrolytic cell is greater than that of the rare-earth electrolytic cell.Therefore,it is concluded that the improved insulation structure of rare earth electrolytic cell is better than that of rare earth electrolytic cell.