Interfacial Heat Transfer Model And Electrothermal Field Coupling Simulation Of Rare Earth Electrolytic Cell

Molten salt electrolysis is widely used in the preparation of rare earth elements and rare earth alloys.In the process of electrolysis,the molten salt generates heat under the action of current and its own resistance,and transfers heat to all parts of the tank through heat conduction and convective heat exchange.A reasonable electrolysis temperature has an important impact on the electrolysis reaction.In the rare earth electrolytic cell,there are limited parts that can be measured by instruments.Generally,the heat transfer formula is used to establish the temperature field model of the electrolytic cell for research.Therefore,it is very important to determine the accurate heat transfer formula for the research of the electrolytic cell.In the heat transfer formula,each heat transfer coefficient directly affects the theoretical calculation of the temperature field of the electrolytic cell,but there is little research on the heat transfer coefficient in the rare earth electrolytic cell.Based on the current situation that the research on the temperature field of the rare earth electrolytic cell is not enough supported by the National Natural Science Foundation of China,this thesis takes the 6k A rare earth electrolytic cell as the research object and uses commercial software to carry out the analysis and modeling of the temperature field of the rare earth electrolytic cell.The research contents include the experimental measurement of the actual temperature distribution of 6k A rare earth electrolytic cell,the modeling and calculation of the heat transfer coefficient between the side shell and the environment of the rare earth electrolytic cell,the modeling and calculation of the heat transfer coefficient between the liquid surface and the air interface of the electrolytic cell,the modeling and calculation of the electro thermal field coupling of the rare earth electrolytic cell,and the analysis of the influence of relevant parameters under different working conditions on the electrothermal field in the cell,so as to find the reasonable structural parameters of the electrolytic cell.The main research contents and conclusions of this thesis are as follows:(1)Through the design of experimental device,the temperature distribution inside the electrolytic cell of fluoride molten salt system is actually measured.It is found that the average temperature of the cell is 1069.3℃,the temperature distribution inside the cell is relatively uniform,and the temperature distribution of excess temperature difference is no more than 3.7℃.The temperature near the open area of the electrolytic cell is the lowest and the temperature near the electrical control equipment is the highest due to the influence of heat transfer coefficient;The temperature distribution characteristics of the external insulation layer of the tank show that the insulation effect at the bottom is the best;(2)Based on the actual temperature measurement experiment,combined with the theory of heat transfer and the analysis of the heat exchange interface of rare earth electrolytic cell,the calculation model of interfacial heat transfer between rare earth electrolytic cell body and environment is established,and the comprehensive heat transfer coefficients of liquid surface and environmental interface of rare earth electrolytic cell,sidewall and environmental interface of rare earth electrolytic cell are calculated respectively.Finally,their respective theoretical results are obtained,The heat transfer coefficient increases with the increase of air velocity;On the simulation platform,the coefficient of the heat transfer coefficient calculation model is modified to obtain the Nusselt number criterion between the liquid level and the environment Nu=0.136 Gr Pr~14,and the Nusselt number criterion between the side tank shell and the environment Nu=0.075 Gr Pr~13,which provides the required thermal boundary conditions for the simulation of electrolytic cell;(3)The electric thermal field coupling calculation of 6k A rare earth electrolytic cell model is carried out by using the numerical simulation software.The simulated temperature distribution results are in good agreement with the actual measurement results,which proves the accuracy of the interface heat transfer model.Under other conditions unchanged,the heat transfer coefficient increases gradually with the increase of temperature,and the heat transfer coefficient changes uniformly with the temperature;With the increase of heat transfer coefficient,the liquid surface temperature decreases gradually;(4)Commercial software is used to simulate the distribution of electrolytic cell potential and temperature field under different working conditions.The size of cathode diameter and the depth of electrode insertion directly affect the electrode surface potential,thus affecting the electrolysis temperature,and finally affecting the output of rare earth metals.Through optimization simulation,it is found that the working condition is the best when the cathode diameter and electrode insertion depth are controlled at 80mm and470mm respectively,which is consistent with the actual production situation on the site.