基于低温熔盐系Na5Al3F14-Li3AlF6-K3AlF6-AlF3-Al2O3铝电解基础研究

A temperature decrease in the aluminum electrolytic process is in favor of reduction of the energy consumption and increase of the cell life. However, the electrical conductivity and the alumina solubility also continue to decrease with decrease temperature. Some alumina sludge forms easily on the cathode due to low dissolution rate of alumina in a low temperature melt. Based on a mild effect of component on liquidus temperature of Na5Al3F14-AlF3 and improving the conductivity by Li3AlF6 and the alumina solubility by K3AlF6, a new molten electrolyte system of Na5Al3F14-Li3AlF6-K3AlF6-AlF3-Al2O3 is suggested for low temperature aluminum electrolysis. The appropriate range in component and temperature would be determined based on a serial of experiments and investigations on liquidus temperature, electrical conductivity of the melt and solubility of alumina and aluminum in the melt. The kinetic model of dissolution of alumina would be built. Especially, the mechanism of formation and dissolution of sludge would be explained. The electrode processes would also be investigated by electrochemical analysis. Effects of temperature, components, aluminum solubility and current density on current efficiency of aluminum electrolysis would be discussed. This work is supposed to provide theoretical basis for developing the low-temperature aluminum electrolysis technology with the system.

降低铝电解的操作温度有利于降低电能消耗、延长铝电解槽寿命。通常，低温铝电解面临着因温度降低电解质熔体的电导率性能变差、对氧化铝溶解性能降低、槽底沉淀多且难以溶解等问题。针对这些问题，基于Na5Al3F14-AlF3系初晶温度受组分影响较弱，Li3AlF6与K3AlF6可分别提高电解质熔体的电导性能与氧化铝溶解性能，提出一种新的Na5Al3F14-Li3AlF6-K3AlF6-AlF3-Al2O3电解质体系。基于对该电解质体系的初晶温度、电导率、氧化铝溶解度、铝溶解度等关键物理化学性质的研究，确定适于铝电解的组分与温度范围。并在此基础上，重点研究氧化铝溶解动力学、沉淀形成与溶解机制。基于电化学技术，研究电极过程动力学。在实验室电解槽上铝电解实验，并结合铝溶解与二次反应损失机理，探索电流效率损失机理。通过本项目研究，为实现该体系低温铝电解技术的应用奠定理论基础。

降低铝电解的操作温度有利于降低电能消耗、延长铝电解槽寿命。通常，低温铝电解面临着因温度降低电解质熔体的电导率性能变差、对氧化铝溶解性能降低、槽底沉淀多且难以溶解等问题。针对上述问题，提出Na5Al3F14-Li3AlF6-K3AlF6-AlF3-Al2O3电解质体系。本项目系统地对该电解质体系的初晶温度和相平衡、电导率、氧化铝溶解度、铝溶解度等关键物理化学性质进行了研究；研究了氧化铝溶解动力学，电解质-氧化铝沉淀形成与溶解机制；研究了铝电解电极过程动力学；研究了电解质对碳阴极腐蚀；通过低温铝电解实验，考察了电解质组分、电流密度、极距、温度等关键因素。通过项目研究：1）建立了低温电解质体系的初晶温度与氧化铝溶解度等关键物理化学数据模型；2）探明了沉淀形成过程，揭示了其溶解机制；3）阐明了低温电解质在炭阴极中渗透规律，明确了该体系铝电解电极过程；4）探索了低温铝电解电流效率损失机理；5）完善了该体系低温铝电解的理论基础。通过研究，发表学术论文13篇，其中被SCIE收录8篇，EI收录2篇；申请国家发明专利6项，其中5项授权；培养博士研究生1名，硕士7名（均毕业）；获第三届全国有色金属优秀青年科技奖1项。