Thermodynamic modeling of eutectic point in the LiNO3–NaNO3–KNO3–NaNO2 quaternary system

Abstract

A novel model based on the thermodynamic principles is developed to predict the eutectic temperature and composition in molten salt systems. In pursuit of novel low melting point molten salt mixtures with high thermal storage density for concentrating solar power generation, a new quaternary eutectic system comprising of lithium nitrate, sodium nitrate and potassium nitrate and sodium nitrite was developed. The thermodynamic model based on regular solution approximation was used to predict the eutectic composition and temperature in the LiNO3–NaNO3–KNO3–NaNO2 quaternary salt system. The result obtained for eutectic point of the LiNO3–NaNO3–KNO3–NaNO2 quaternary system was T=98.6°C and XLiNO3=0.215, XNaNO3=0.142, XKNO3=0.424, and XNaNO2=0.219. The calculated eutectic composition obtained from the thermodynamic model was verified experimentally for the eutectic temperature using the Differential Scanning Calorimetry (DSC) technique. Melting temperature of 99.02°C was obtained from the heating cycles. The experimentally determined melting temperature of the eutectic composition was in excellent agreement with that of calculated eutectic temperature of the system.