【作者】 王志刚；

【导师】 李劼；

【作者基本信息】 中南大学 ， 有色金属冶金， 2009， 博士

【摘要】 铝电解槽是炼铝的核心设备,其发展与进步代表了电解铝工艺的革新。传统铝电解工艺一直沿用消耗性的炭素阳极,由此产生了一系列的问题,惰性阳极及其电解新工艺因能解决这些问题而成为国际铝业界的研究焦点,因此开展惰性阳极铝电解槽设计方面的研究具有十分重要的意义。本文以满足国家“863”重点项目中关于“构建扩大试验用(5kA级)惰性阳极铝电解槽”的需求为目标,以本课题组研发的一种金属陶瓷惰性阳极为应用原型,开发了惰性阳极铝电解槽的物理场仿真方法。主要研究成果如下:(1)在充分研究用金属陶瓷惰性阳极替换现行炭素阳极后电解槽在结构和工艺参数等方面所发生的显著变化的基础上,建立了惰性阳极铝电解槽“电-磁-热-流-应力”等物理场的仿真计算方法及程序。经验证,此方法合理可行、收敛性好、精度较高,为惰性阳极铝电解槽的开发提供了技术支持。(2)针对本课题组研发的一种深杯状金属陶瓷惰性阳极,深入研究了其热应力的分布与演变规律。计算结果表明:压应力作用于阳极大部分区域,在阳极与电解质及空气接触的三相界面处存在较大的轴向拉应力,是阳极破裂的主要原因;通过优化阳极结构参数、阳极浸入电解质中的深度以及电解工艺参数(包括阳极电流密度和电解温度等)可以达到减缓阳极热应力的目的,例如,适当增加阳极高度、阳极中孔深度和降低中孔半径、阳极浸入电解质中的深度以及降低电解温度均可降低阳极热应力。(3)针对已有的铝电解槽熔体流动场(即流场)仿真计算方法对流场(尤其是结构相对较复杂的惰性阳极周边的流场)仿真计算效果不佳的问题,提出了铝电解槽准三相流仿真计算方法。通过将气体作用等效为体积力作用,将复杂的电解质-铝液-气泡三相流计算转化为多步两相流计算,从而能够实现在气体及电磁力共同作用下电解质和铝液流场的耦合计算。应用该方法对惰性阳极铝电解槽的流场仿真计算表明,通过优化阳极结构参数、阳极浸入电解质中的深度以及电解工艺参数可以达到优化电解质和铝液流场的目的。(4)提出了多种5kA级惰性阳极铝电解槽结构原型,研究了电解槽的电热场、热应力、电磁场、流场等物理场的分布特征。对比分析表明,采用六阳极为一阳极组的电解槽比采用八阳极为一阳极组的电解槽具有更优的物理场分布,适宜电解槽采用。在此基础上仿真研究了过热度及电流强度对5kA级惰性阳极铝电解槽物理场的影响,这些结论为惰性阳极电解槽的建造与试验提供了技术支撑。更多还原

【Abstract】 Aluminum reduction cell is the core equipment for extracting aluminum, and its development and progress represent the renovation of aluminum electrolysis. Consumable carbon anodes have always been adopted in conventional aluminum electrolysis process, which has a series of problems. Owing to the problem-solving capabilities, inert anode and new reduction techniques using inert anode have become the research focus of international aluminum industry. Thus the research in designing aluminum reduction cell using inert anode has great significance.With the construction of an experimental (5kA grade) inert-anode aluminum reduction cell prepared for a national "863" program as the main target of this research and with a kind of cermet inert anode prepared by our research group as the application prototype, methods for simulating physical fields in inert-anode aluminum reduction cell have been developed. The main conclusions and achievements are as follows:(1) Based on full study of the remarkable change of cell structure and technical parameters caused by the replacement of carbon anode with inert anode, methods and procedures for the simulation of "electric-magnetic-thermal-flow-stress" fields in the inert-anode aluminum reduction cell have been developed, which have been proved to be reasonable and feasible with good convergence and high precision and can provide technical support for the development of inert-anode aluminum reduction cell.(2) Focusing on a kind of "deep-cup" cermet inert anode developed by our group, the distribution and evolution of its thermal stress have been studied thoroughly. The results show that compressive stress exists on most region of the anode and large tensile stress exists at the three-phase contact surface of the anode, bath and air, which is the major cause of anode cracking. By optimizing the anode structure parameters, anode immersion depth and technical parameters including current intensity and electrolysis temperature etc., the thermal stress of the inert anode can be relaxed. For example, increasing the anode height and central hole depth and reducing central hole radius, anode immersion depth and electrolysis temperature properly can be helpful to the reduction of the thermal stress of the inert anode.(3) As the calculation effect of the existing method for simulation of the flow-field in aluminum reduction cell, especially of the flow field around the inert anodes with complicated structure, is not good enough, a quasi simulation method has been put forward. By equating the gas effect to volume force, the complex calculation of electrolyte-aluminum-bubble three-phase flow can be converted to the multi-step calculation of two-phase flow, which can realize the coupled calculation of electrolyte and aluminum under the combined effect of gas and electromagnetic force. The flow field simulation of the inert-anode aluminum reduction cell shows that the flow field of electrolyte and aluminum can be optimized by optimizing the anode structure, anode immersion depth and technical parameters.(4) Several structure prototypes of 5kA-grade inert-anode aluminum reduction cell have been put forward and the distribution of the physical fields including thermoelectric, thermal stress, electromagnetic and flow fields has been investigated. The comparison and analysis show that distribution of the physical fields in the cell with six anodes as an anode group is better than that in the cell with eight anodes as an anode group, so the former is more suitable for 5kA-grade inert-anode aluminum reduction cell. On the basis of above investigation, the effect of superheat temperature and current intensity on the physical fields has been studied. All these conclusions provide technical support for the building and experiment of the inert-anode aluminum reduction cell.更多还原