Effect of purity on thermophysical properties, thermal stability and corrosivity of ternary mixed salts

Abstract

In this work, a ternary mixed salt of KNO₃-NaNO₂-Ca(NO₃)₂ was prepared by high temperature melting method. The thermal physical properties of selected ternary mixed molten salt with 99 % and 98.5 % purity are investigated under thermal shock and constant high temperature conditions. The results show that the melting points of the initial ternary molten salt are 125.62 °C and 120.3 °C with 99 % and 98.5 % purity, while the decomposition temperatures are 601.5 °C and 593.2 °C. In comparison with the initial base salt, the melting point, initial crystal point and specific heat capacity of the 99 % and 98.5 % purity salt mixtures were found to increase by a maximum of 49 % under the 1000 h constant temperature test, and the thermal conductivity was reduced by a maximum of 12 % under the 500 times thermal shock condition. The annual corrosion rates after 1000 h of static corrosion in air are 0.051 mm y⁻¹ and 0.053 mm y⁻¹. The decomposition temperatures are almost stable in all conditions. The impurities have a slight influence on the thermal stability of the mixed molten salts. This work provides valuable data and insights for the utilization of mixed ternary mixed molten salt.