铝电解槽槽帮与电解质多尺度行为机理与数学建模

With the large-capacity prebaked aluminum reduction cell and process operations of harsh, the cell self-regulating ability is greatly reduced, which makes it very important to study the behavior of ledge for long life and low power consumption of aluminum reduction cell. Since the microscopic formation, evolution and interphase interaction of ledge is still not very clear in aluminum reduction cell, multi-scale modeling and experiment will be carried out to study the morphology–phase field process-heat and mass transfer of ledge in this project. Firstly, a ledge-electrolyte molecular model will be created to calculate the morphology of each element, which will be validated by the Raman spectroscopy and other modern technology. At the same time, the thermodynamic calculations were carried out to build the microscopic phase-field model, which will be used to study the formation and phase transformation between the ledge and electrolyte. Moreover, the actual experiment and industrial test will be carried out to derive the macroscopic phase change and heat transfer mechanism, which will be used to build transit multi-phase flow model of ledge. Finally, a method of coupling microscopic and macroscopic by parameter exchange were be put forward, and a multi-scale ledge behavior model is built, and the ledge behavior, including the ledge microscopic formation and evolution, macroscopic shape, interphase interaction and heat transfer, will be theoretically analyzed and calculated, and the dynamic interaction law between the ledge behavior and the heat and material balance of the cell will be revealed. This project can provide reliable theoretical basis for the optimized ledge formation and regulation method in super-large scale or energy saving aluminum reduction cell.

随着铝电解槽大型化及操作工艺苛刻化，其自平衡能力被大幅削弱，研究并掌握槽帮的多尺度行为对电解槽长寿命低电耗运行具有重要意义。本项目针对现有铝电解槽槽帮微观形成、演变及与电解质相间作用机理不明确的现状,拟应用机理建模与实验检测结合的方法，开展槽帮内元素赋存形态-相场过程-传质传热的多尺度行为研究。项目首先建立槽帮的分子动力学模型，计算各元素的赋存形态，并应用拉曼光谱等技术进行验证与修正；同时，基于热力学计算结果，建立槽帮微观组织相场模型，分析槽帮内各液固相及微观组织的形成与转变规律；在此基础上，结合宏观实验和理论推导，获得槽帮-电解质之间宏观相变与热传递机理，开发基于参数传递的微观与宏观耦合建模方法，建立多场作用下铝电解槽槽帮与熔体多尺度多相流模型，研究并揭示槽帮行为对电解槽能量与物料平衡的作用规律。本项目研究成果可为特大型或节能型铝电解槽最优化槽帮的形成与调控提供理论依据。

本项目针对现有铝电解槽槽帮微观形成、演变及与电解质相间作用机理不明确的现状,应用机理建模与实验检测结合的方法，开展了槽帮元素赋存形态-相场过程-传热的多尺度行为研究。.主要研究内容为：典型槽帮界面微（介）观尺度各元素赋存形态、槽帮微观晶体的生长与消融演变过程微观动力学、槽帮-电解质之间的相变传质与传热机制、多场作用下槽帮-电解质的相间传质-传热机理模型。.所获主要成果: .①通过开展实验室槽帮模拟生成和工业槽帮实时生成实验及相关检测，发现槽帮样本在厚度方向上有明显的结构分层，呈现具有致密层和开放结构层等多孔结构，槽帮主要的物相组成为冰晶石、钙冰晶石、亚冰晶石和氧化铝。.②计算了典型槽帮体系的三元相图、自由能和相平衡数据，拟合出槽帮熔盐各相连续自由能关系式并离散化，引入相场模型，计算分析了不同过冷度、各向异性参数、界面厚度等参数对晶体生长及凝固组织生长演化过程、形核密度等微观组织演化的影响。.③建立了槽帮的微-介观导热模型，计算了槽帮物相晶格导热率和槽帮有效导热率，并通过微观检测图像的处理预测了槽帮介观导热性质。槽帮的有效导热率随温度的升高而减小，温度高于563 ℃时，槽帮中的主要化合物冰晶石发生相转变，有效导热率进一步减小。.④结合微-介观导热模型计算结果，建立了铝电解槽热-流强耦合多相流凝固模型，实现了对三维全槽槽帮形状的稳态求解。结果表明：槽膛内形整体形状不规则，槽内四周角部区域的槽帮较厚，上部槽帮与伸腿转换的位置存在着一个明显的台阶，伸腿部分普遍过于肥大。.⑤基于上述槽帮传热与传质机理行为的研究结果，提出铝电解槽槽帮优化设计方案，建立了槽帮最优化调控思路，当电解槽内热量过剩时，通过增强外部散热条件可以加强对槽帮的调控，尤其是增强电解槽上部和覆盖料表面的散热。.本项目研究成果可为特大型或节能型铝电解槽最优化槽帮的形成与调控提供理论依据。