| During the production of rare earth molten salt electrolysis,the flow field formed by molten salt-anodic bubble-rare earth metal affects the circulation of electrolyte,which has an important influence on the dissolution of rare earth raw materials,the diffusion of oxide ions and the blanking process of raw materials.The improper feeding method can easily lead to problems such as slow dissolution rate and agglomeration of raw materials,which is not conducive to the electrolysis reaction.The internal flow field distribution of the electrolytic cell at high temperature is not easy to observe.The numerical simulation technology can calculate the internal flow field distribution and summarize the flow field distribution law to optimize the rare earth oxide blanking process and improve the rare earth metal electrolysis technology.In this paper,the 6 k A plug-in cathode rare earth electrolytic cell is used as the prototype.by numerical simulation.ANSYS-FLUENT software is used to study the internal flow field,oxide blanking position,blanking method and blanking particle size of rare earth electrolytic cell.The results are as follows :(1)A multiphase flow model was established to calculate the water air two-phase flow field.According to the actual structure of the electrolytic cell,a water model test bench was built.The numerical simulation results were compared with the water model experimental results.At the same time,compared with other literature,the flow field distribution results were basically consistent,thus verifying the accuracy of the multiphase flow model.(2)The multiphase flow model was used to calculate the three-dimensional multiphase flow field of molten salt,anode bubble and rare earth metal in the actual electrolyzer,and the distribution law of multiphase flow field in the actual electrolyzer with uniform pole distance was studied.The maximum flow velocity in the electrolyzer was 0.535 m/s,and the penetration depth of bubbles was 25 mm.Therefore,the blanking position should be 25 mm away from the inside of the anode.The influence of non-uniform pole distance on the multiphase flow field in the actual electrolytic cell was studied.The results showed that the maximum flow velocity in the electrolytic cell increased from 0.535 m/s to 0.7 m/s.With the increase of pole distance,the bubble penetration depth decreased from 25 mm to 18 mm.Rare earth metals exhibit skewness during the dripping process,and the skewness angle increases with the increase of the polar distance ratio.(3)The multiphase flow model is used to calculate the three-dimensional multiphase flow field of electrolytic cells with different polar distances,and the blanking position is optimized through the downward axial velocity in the gas-liquid interface.The optimal cutting position is a circular ring with a cathode center as the center and a ring width of 30 mm.When the polar distance is 85 mm,95 mm,105 mm,and 115 mm,the inner diameters of the ring are 50 mm,60 mm,70 mm,and 75 mm,respectively.(4)Based on the multiphase flow model,a component transport model was added to calculate the concentration distribution of neodymium oxide at different feeding points,and optimize the feeding mode.The results indicate that the optimal feeding method is to simultaneously feed at four feeding points,which not only accelerates the diffusion rate of oxide ion concentration,but also facilitates the uniform distribution of rare earth oxides in the electrolytic cell.(5)Based on the multiphase flow model,the discrete phase model was added to calculate the trajectories of neodymium oxide particles with different particle sizes,and the residence time and number ratio of neodymium oxide in the electrolytic reaction zone of the cathode and anode of the electrolytic cell were analyzed.The optimum particle size of neodymium oxide is10 um,and 96.8 % of neodymium oxide has a residence time of more than 10 s in the electrolytic reaction zone after feeding at four feeding points at the same time,which is beneficial to the electrolysis. |
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