Degradation of a commercial ternary molten salt under various atmospheres for CSP applications

Abstract

This research aims to study the degradation and the changes in physicochemical properties of a ternary molten salt mixture, commercially known as Hitec, in contact with a nitrogen and an air atmosphere. The degradation of the salt was determined by chemical analysis of the NO3- and NO2- anions and DSC determination of the melting and freezing point of the mixture. To this end, isothermal tests at 500 °C were performed for 1000 h. A deeper study of the evolution of the salt under air atmosphere was carried out until 2000 h. It was found that the mixture properties studied remain invariable when it was operated under N2 atmosphere. The use of atmospheric air resulted in a progressive increase in melting and freezing points due to the nitrite transformation to nitrate. The effect of the degradation could be observed in the early hours of the test and after 2000 h of test, the system had not reached and steady state and the degradation progress was still ongoing.This research aims to study the degradation and the changes in physicochemical properties of a ternary molten salt mixture, commercially known as Hitec, in contact with a nitrogen and an air atmosphere. The degradation of the salt was determined by chemical analysis of the NO3- and NO2- anions and DSC determination of the melting and freezing point of the mixture. To this end, isothermal tests at 500 °C were performed for 1000 h. A deeper study of the evolution of the salt under air atmosphere was carried out until 2000 h. It was found that the mixture properties studied remain invariable when it was operated under N2 atmosphere. The use of atmospheric air resulted in a progressive increase in melting and freezing points due to the nitrite transformation to nitrate. The effect of the degradation could be observed in the early hours of the test and after 2000 h of test, the system had not reached and steady state and the degradation progress was still ongoing.