Research On The Influence Of Electrode Spacing On Physical Fields In Rare Earth Electrolyzer And The Selection Of Electrode Spacing

With the rapid development of national industry,the manufacturing industry has an increasing demand for rare earth metals.In order to find the appropriate electrode spacing in the electrolytic process of rare earth and improve the electrolytic efficiency of rare earth electrolytic cell,the influence of the existing electrode spacing of 8KA rare earth electrolytic cell on the physical field in the cell was studied.Based on the common electrode spacing in rare earth electrolytic production is between 80-90 mm,the electric field,thermal field and flow field in 8KA rare earth electrolytic cell were simulated with the electrode spacing of75 mm,80mm,85 mm,90mm and 95 mm respectively,and the simulation results were analyzed.The influence of electrode spacing on current density,cell voltage,cell temperature distribution and electrolyte flow in electrolytic cell was obtained.The influence law of electrode spacing on physical field in cell was found out by comparing the variation of various parameters,and the most suitable electrode spacing under normal electrolytic condition was found out.The physical field parameters under the electrode spacing were verified by experiments.The specific conclusions of this study are as follows:(1)The electric field mathematical model of 8KA rare earth electrolytic cell under different electrode spacing was established,and the electric field simulation in the cell was carried out.Comparing the simulation results,it was found that Yin and Yang were extremely unequal potential bodies,the anode current density distribution was uneven,the anode current density reached its maximum at the electrolyte level on the inner surface of the anode,and the current density decreased as it went down,and slightly increased at the bottom tip due to current convergence.The cathode current density decreases gradually from the electrolyte level down.With the increase of the electrode spacing,the current density on the inner surface of the anode decreases.As the gap between adjacent anodes increases,more current flows from the anode side to the electrolyte.The increase of electrode spacing leads to the increase of cell voltage.The potential analysis of anode surface shows that the increase of cell voltage is due to the increase of electrolyte,the increase of resistance and the increase of anode surface potential,but the potential of anode remains at 0.4V.(2)The mathematical model of the thermal field in the 8KA rare earth electrolytic cell with different electrode spacing was established,and the electrothermal coupling simulation in the electrolytic cell was carried out.Comparing the simulation results,it was found that the temperature in the cell increased with the increase of the electrode spacing,and the maximum temperature and minimum temperature in the cell increased obviously.Too small pole spacing will cause the temperature in the tank is too low,electrolyte solidification,too large pole spacing is easy to cause the dielectric temperature is too high,unfavorable to electrolysis;As the distance between poles increases,the maximum temperature of the cell decreases from the upper position in the middle of the cell.The temperature of the electrolyte between the anode and the cathode increased with the increase of the electrode distance,and the electrolyte temperature between the anode and the cathode was all within the most suitable electrolytic temperature range at the 90 mm electrode distance.Compared with the simulation results,it is concluded that the temperature distribution in the cell is the most favorable for electrolysis when the electrode spacing is 90 mm.The experimental verification shows that the temperature distribution in the cell is in a reasonable range when the electrode spacing is90 mm.(3)The simulation model of the bubble flow field in the 8KA rare earth electrolyzer under different pole spacing was established,and the simulation of the bubble flow field in the electrolyzer was carried out.By comparing the simulation results,it was concluded that:The electrolyte flow field reaches a stable flow cycle state about 25 s after the electrolytic interruption(anode replacement or rare earth metal removal)is re-energized.With the increase of electrode spacing,the stable maximum flow velocity of the electrolyte flow field first increases and then decreases.The area of eddy current between anode and cathode also increases gradually.When the distance between poles is 95 mm,the small eddy current at the bottom of the cell is divided by eddy current between anode and cathode.The increase of eddy current between anode and cathode will lead to the complex flow of the flow field at the bottom of the electrolytic cell,which will greatly affect the collection of rare earth metals at the bottom of the electrolytic cell.Compared with the simulation results,the flow condition at the bottom of the electrolytic cell is more conducive to the collection of rare earth metals when the distance between the poles is less than 90 mm.According to the influence of 8KA electrode spacing on the electric field,temperature field and flow field in the electrolytic cell,the parameters of the physical field in the cell are the most reasonable under the condition of 90 mm electrode spacing,and the electrode spacing is considered to be the most appropriate in normal electrolytic process.