稀土电解槽石墨内衬氧化扩散与孔隙结构演化模型

Oxidation diffusion and pore structure evolution model of graphite lining for rare earth electrolysis

基于Fick定律和质量守恒定律,考虑石墨内衬中氧化反应、气体扩散和孔隙结构演化之间耦合作用,建立稀土熔盐电解环境下的石墨内衬试样的氧化扩散与孔隙结构演化数学模型,研究石墨内衬氧化扩散和孔隙结构演化过程。在二氧化碳环境下进行石墨高温氧化实验,采用CT显微技术获取试样孔隙结构图像,对CT图像进行二值化分割处理,统计计算孔隙率,将圆柱试样模型孔隙率、失重率的计算值与实验测试值进行对比验证,并对氧化腐蚀过程中圆柱试样二氧化碳浓度、孔隙率、失重率、氧化速率变化规律进行数值分析。结果表明:反应扩散与孔隙结构演化密切相关,氧化扩散会显著改变孔隙结构,孔隙结构演化会反过来影响氧化扩散进程;石墨内衬氧化扩散与孔隙结构演化受温度影响显著,温度越高,反应越快,孔隙率越大,槽体寿命越短。模型计算结果与实测结果基本一致,表明运用该模型对稀土电解槽石墨内衬在电解环境下氧化扩散与孔隙结构演化过程进行计算分析可行、有效。

Based on the Fick＇s law and the law of conservation of mass,the mathematical model for the oxidation diffusion and the pore structure evolution of graphite liner under the rare earth molten salt electrolysis environment was established which included the effects of the oxidation reaction, the gas diffusion and the pore structure evolution. Under high carbon dioxide environment and high temperature, the graphite oxidation experiment was carried out. The CT technology were adopted to obtain the pore structure images which were then binarized and the porosity was calculated statistically. The calculated values of the porosity and weight loss rate of the cylindrical sample were compared with the experimental results. Then the oxidative corrosion process were simulated numerically. The results show that the reaction diffusion iand the evolution of the pore structure influnece each other significantly. In additon, the oxidation and diffusion of the graphite liner was greatly influenced by temperature. At higher temperature,the reaction runs faster,and the porosity becomes higher,as a result,the life of the tank is shorter. The calculation results of the model are consistent with the measured results,which indicates that it is feasible and efficent to use the model to calculate and analyze the oxidation and diffusion process of the graphite liner under the electrolytic environment.