LiCl-NaCl-KCl相图的实验测量和热力学优化  

Experimental measurement and thermodynamic optimization of the phase diagram of LiCl-NaCl-KCl system

作　　者：卢广轩 赖添旺 何茂刚[1] 刘向阳[1] Guangxuan Lu;Tianwang Lai;Maogang He;Xiangyang Liu(MOE Key Laboratory of Thermo-Fluid Science and Engineering,Xi’an Jiaotong University,Xi’an 710049,China;Western Metal Materials Co.,Ltd,Xi’an 710201,China)

机构地区：[1]西安交通大学,热流科学与工程教育部重点实验室,西安710049 [2]西部金属材料股份有限公司,西安710201

出　　处：《科学通报》2020年第7期641-648,共8页Chinese Science Bulletin

基　　金：国家杰出青年科学基金(51525604)资助。

摘　　要：碱金属氯化盐混合物LiCl-NaCl-KCl可以作为熔盐电解法制备稀土及其合金的电解质,该体系的相图是构建含稀土的多元氯化盐体系热力学数据库的基础.本文采用差热分析法对二元系LiCl-NaCl和三元系LiCl-NaCl-KCl的相图进行了实验测量,并基于新的实验数据和文献数据对这两个体系的相图重新进行了热力学优化,修正了现有数据库中LiCl-NaCl-KCl的热力学参数.计算得到的LiCl-NaCl是二元匀晶体系,极小值点位于xNaCl=0.262,温度为820 K.与前人的优化结果相比,本文计算得到的固相线更接近实验值.计算结果表明,LiCl-NaCl-KCl的液相面有一个极小值点,而不是四相共晶点,对应的组分为55%LiCl-8%NaCl-37%KCl,温度为620 K.Molten salt electrolysis is one of the most important methods to produce rare earth metals and their alloys.In this method,mixtures consisting of rare earth chlorides and alkali chlorides are usually used as electrolytes.The knowledge of the thermodynamic properties of electrolytes is essential to design and improve the electrolytic process.The relationship between the composition and the primary crystal temperature can be obtained through the phase diagram of the molten salt.Then the electrolysis temperature and electrolyte composition can be initially determined,which lays a foundation for further study of other properties.Since the most commonly used alkali chlorides in industry are LiCl,NaCl and KCl,the phase equilibrium data of LiCl-NaCl-KCl are bases for constructing the thermodynamic database of multicomponent chloride melts containing rare earths.This paper mainly focuses on the thermodynamic properties of the binary system LiCl-NaCl and the ternary system LiCl-NaCl-KCl.With regard to the binary system LiCl-NaCl,numerous researchers have used the thermal analysis method to experimentally measure its phase diagram.However,the data obtained by different researchers are quite different.Whether there exist intermediate compounds and whether it is an isomorphous phase diagram is still not confirmed.Furthermore,the existing experimental data were mostly measured by the cooling curve method from 1910 to 1960 and they are generally not consistent with each other.Besides,the deviation between the recently calculated phase diagram and experimental data is somewhat large.For instance,the temperature deviation between the calculated and measured solidus can be up to 30 K.With respect to the ternary system LiCl-NaCl-KCl,the measurement of the phase diagram has been performed by many researchers and the thermodynamic optimization has also been carried out.However,there is significant difference among these experimental data.And the results of previous optimization are inconsistent with FTsalt database of FactSage softw

关 键 词：LiCl-NaCl-KCl 修正的似化学模型 实验测量 热力学优化 

分 类 号：TF803.27[冶金工程—有色金属冶金] O642.42[理学—物理化学]