Phase diagram analysis of binary and ternary salts of lithium, sodium and potassium nitroxides

doi:10.19799/j.cnki.2095-4239.2024.1227

Abstract

Abstract:

The eutectic properties of molten salts are key indicators for assessing their potential in thermal storage applications, with broad relevance in efficient thermal storage technologies. To quickly and accurately predict whether a eutectic can form between different components of mixed nitrate salts, and to further determine their eutectic composition and lowest melting point, this study employs FactSage thermodynamic simulation software to simulate five common nitrate salts—lithium nitrate (LiNO₃), potassium nitrate (KNO₃), sodium nitrate (NaNO₃), potassium nitrite (KNO₂), and sodium nitrite (NaNO₂). Phase diagrams of their binary and ternary systems were predicted thermodynamically. Based on the simulation results, the effects of anions and cations on the eutectic properties of binary and ternary nitro salt systems were further analyzed. It was found that different combinations of anions and cations significantly influence the eutectic formation temperature and eutectic composition. To verify the accuracy of the phase diagram predictions, binary salt (Li-K nitrate) and ternary salt (Li-Na-K nitrate) systems with favorable eutectic behavior were experimentally validated by determining their melting points and eutectic compositions. The experimental results showed consistency with the predicted values, further confirming the validity and accuracy of FactSage software in predicting the phase diagrams of molten salt systems. In addition, this study predicts binary and ternary phase diagrams for several common nitro salts to analyze the mechanism by which cations and anions influence mixed molten salt energy storage media. Through this work, new approaches are proposed for evaluating the eutectic behavior of mixed nitrate salts, providing essential theoretical support for optimizing and applying molten salts in future thermal storage technologies.

Key words: molten salt, phase diagram calculation, eutectic, melting point

CLC Number:

TK 02

Jinzhu ZHANG, Lingran MENG, Yuting WU, Tianqing SHI, Yongqiang SHANG, Ruiping ZHI, Wenzhen WEI. Phase diagram analysis of binary and ternary salts of lithium, sodium and potassium nitroxides[J]. Energy Storage Science and Technology, 2025, 14(6): 2515-2523.

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硝基二元盐种类	共晶温度/℃	共晶组成/%
LiNO₃-KNO₃	124.6	33.89∶66.11
LiNO₃-NaNO₃	196.2	49.17∶50.83
NaNO₃-KNO₃	218.5	43.06∶56.94

硝基二元盐种类	共晶温度/℃	共晶组成/%
LiNO₃-KNO₂	92.31	43.06∶56.94
LiNO₃-NaNO₂	151.5	46.67∶53.33
KNO₃-NaNO₂	136.9	56.94∶43.06

序号	共晶温度/℃	共晶组成(LiNO₃∶KNO₃∶NaNO₃)/%
1	119.16	29.501∶57.224∶13.275
2	119.56	29.573∶57.01∶13.417
3	121.27	31.633∶61.976∶6.391

序号	共晶温度/℃	共晶组成(LiNO₃∶KNO₃∶NaNO₂)/%
1	101.45	26.232∶55.574∶18.194
2	106.13	22.743∶56.848∶20.409
3	112.4	28.119∶45.139∶26.742
4	113.87	27.698∶43.872∶28.43
5	114.7	10.586∶56.776∶32.638
6	115.02	28.706∶42.596∶28.698

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