LiNO3-NaNO3-KNO3三元熔盐材料的设计及热稳定性研究

采用共形离子溶液模型(conformalionic solution model, CIS) 在二元熔盐体系相图的基础上,对三元熔盐体系LiNO₃-NaNO₃-KNO₃进行了相图计算,得到该三元体系最低共熔点为117.7℃,相应的摩尔分数组成分别为x(LiNO₃) = 0.375,x(NaNO₃) = 0.075,x(KNO₃) = 0.550。按照热力学最低共熔点计算结果,采用熔融法制备了三元硝酸熔盐,通过DSC和TG实验测定其最低共熔点为118.3℃,这与计算得到的结果(117.7℃)基本一致。TG测试结果表明当温度低于587.2℃时,该三元熔盐体系较为稳定,其工作温度范围为118.3~587.2℃,该三元硝酸熔盐适合在太阳能热发电中作为高温传热蓄热材料使用。

Design and thermal stability study of LiNO3-NaNO3-KNO3 ternary molten salt system

According to the binary molten salt system phase diagrams, the phase diagram of LiNO₃-NaNO₃-KNO₃ ternary molten salt system was calculated with the CIS model, it turned out that, the lowest eutectic melting point was 117.7℃ and the corresponding composition was x(LiNO₃) = 0.375,x(NaNO₃) = 0.075 and x(KNO₃) = 0.550. The eutectic mixture was prepared based on the predicted eutectic composition, and a experiment test was carried out by the thermal gravimetric analysis (TG) and differential scanning calorimeter (DSC). The DSC test showed that the experimental melting point was 117.7℃, which was in good agreement with the result of this calculation. The TG test results show that the ternary molten salt system is stable when the temperature is below 587.2°C, and its working temperature range is 118.3—587.2°C. The system is quite suitable as a material for high-temperature heat transfer and heat storage in solar thermal power generation.