三元硝酸熔盐高温热稳定性实验研究与机理分析

Experimental study and mechanism analysis for high-temperature thermal stability of ternary nitrate salt

通过熔盐质量损失率和试样中NO2-含量变化状况,以及熔盐材料的热重(TG)曲线,研究了三元硝酸熔盐(53%KNO3-40%NaNO2-7%NaNO3)在空气和氮气气氛中高温条件下的热稳定性性能。结果表明,三元硝酸熔盐空气中的上限使用温度为773K,高温时存在劣化现象;而在氮气气氛中三元熔盐的热分解温度为723K。同时,从热力学和动力学角度分析得到,三元硝酸熔盐在773K以下空气中发生的反应为亚硝酸钠的分解和氧化;而在氮气气氛中三元熔盐723K以下时主要发生的是亚硝酸钠的分解反应。在氧气含量一定的情况下,氧气的扩散和亚硝酸盐的分解反应符合一级反应动力学模型。

High-temperature thermal stability of ternary nitrate salt（53%KNO3-40%NaNO2-7%NaNO3）in air and nitrogen is investigated by mass loss ratio,NO-2 content of molten salt and thermo-gravimetric analysis.The results show the upper limit of operation temperature is 773 K in air for the ternary nitrate salt and the deterioration will appear at higher temperatures,while the thermal decomposition begins at 723 K and proceeds slowly in nitrogen.According to the thermodynamics and kinetics of molten salt,the thermal decomposition and oxidation of sodium nitrite of the ternary nitrate salt occur below 773 K in air,while the reaction for the ternary salt in nitrogen is the thermal decomposition of sodium nitrite below 723 K.Diffusion of oxygen and decomposition reaction of nitrite follow the first order reaction kinetics when the oxygen content is constant.