基于显微CT的多场耦合作用下稀土电解槽石墨内衬破损渗漏研究

Cell life has always been a problem remained to be solved in the electrolysis industry of rare earth. The core of the problem lies in the failure and leakage problem of the pot lining in rare earth electrolysis cell, and the key to solving this problem is to achieve the precise prediction and control of the pot lining failure process. In accordance with the specific service environment of the pot lining, this project has made a fundamental research on the pot lining failure action by an entry point to the multi-field coupling effect, based on the microscopic damage mechanics and porous media flow solid coupling theory and adopting the comprehensive utilization of experimental and theoretical analysis, numerical simulation methods. The specific research idea is to create a set of coupling penetration testing and non-destruction identification technology in the whole process of stress-strain and in the environment of rare earth electrolysis based on the pot lining under the micro-CT scan, to realize the three-dimensional reconstruction and analyze the evolution law and response mechanism of the real fine view of the pot lining structure. We will establish a micro-damage constitutive equation of the pot lining and a penetration-stress-damage coupling model to carry out the finite element transplantation of the new model in the aim of achieving the microscopic numerical simulation of the pot lining penetration failure process and adopting it to predict the space-time evolution process of molten salt penetration field, stress field and damage field. Therefore, it will provide the technical parameters and theoretical basis for optimizing the preferable design and extending the life of rare earth electrolysis cell, which shows an important theoretical and practical value.

槽龄问题一直是稀土电解业亟待解决的难题，其核心就是槽内衬破损渗漏问题，而解决此问题的关键就是如何对内衬破损过程进行精准预测和控制。针对内衬所处的特定服役环境，本项目以多场耦合效应为切入点，以细观损伤力学和多孔介质流固耦合理论为基础，综合利用实验、理论分析、数值模拟等方法对内衬的破损行为进行基础性研究。具体研究思路是：构建一套基于显微CT扫描的稀土电解环境下内衬应力—应变全过程渗透耦合试验与无损识别技术，实现对内衬真实微细观结构的三维重建，分析内衬微细观结构的演化规律及其与渗透性的响应机制；以此为基础建立内衬细观损伤本构方程及渗透—应力—损伤耦合模型，并对新构的模型进行有限元移植，实现内衬渗透损伤演化过程的细观数值模拟，用于预测熔盐渗透场、应力场和损伤场的时空演化，从而为稀土电解槽的优化设计和延长槽寿命提供技术参数和理论依据，具有重要的理论和实际应用价值。

稀土电解槽寿命偏短一直是困扰稀土业界的难题，其中，由于缺乏对核心构件石墨内衬破损过程的预测与控制，导致其先行失效的例子屡见不鲜，成为制约延长槽寿命的主要瓶颈。为此，本项目以实验研究为基础，采用理论分析和数值计算相结合的方法，对内衬破损的时空演化规律进行了研究，获得了以下研究成果：以细观损伤力学和多孔介质流固耦合理论为基础，构建了一套基于显微CT扫描的稀土电解环境下内衬应力—应变全过程渗透耦合试验与无损识别技术，实现了对内衬真实微细观结构的三维重建，通过显微CT扫描对内衬孔隙结构进行了定量表征，利用分形维数可以很好的描述孔隙分布复杂程度，测得的孔喉参数可以用来分析空气和电解质在石墨内衬中的流动情况，进而分析内衬的氧化腐蚀程度。基于Fick定律和质量守恒定律，考虑内衬中氧化反应、气体扩散和孔隙结构演化之间耦合作用，建立了稀土熔盐电解环境下的内衬氧化扩散与孔隙结构演化数学模型，揭露了内衬氧化扩散和孔隙结构演化规律。并通过引入渗透系数与体应变之间的关系式，综合考虑氧化腐蚀—应力耦合作用，建立了内衬氧化腐蚀—应力耦合本构模型。并对新构的模型进行有限元移植，实现了内衬渗透损伤演化过程的细观数值模拟，用于预测熔盐渗透场和应力场的时空演化，从而为稀土电解槽的优化设计和延长槽寿命提供技术参数和理论依据，具有重要的理论和实际应用价值。依托该项目，发表了7篇论文，其中EI论文5篇，授权3项发明专利。培养研究生2名，参加国内外学术会议4次，顺利完成了整个项目预期研究目标。