低熔点硝酸熔盐储热材料的开发

Development of Low Melting Point Nitrate Molten Salt Heat Storage Material

低熔点混合硝酸熔盐可以很好解决传统Solar二元熔盐储热系统管道冻堵等问题,对于降低熔盐储热系统的运维成本,提高系统的运行安全性有重要意义。基于计算相图方法对NaNOKNO Ca(NO_(3))_(2)三元熔盐进行相图热力学计算,通过试验获得NaNO-KNO,-Ca(NO_(3))_(2)三元熔盐的低温共晶点配比和熔点,并在三元共晶组分基础上添加LiNO_(3),进一步降低熔盐熔点。根据不同配比熔盐在不同温度下的形态,得到更低熔点的四元熔盐材料,经过差示扫描量热法测试和热重测试,熔点为55.1℃,初晶点为54.6℃,上限使用温度为561℃。该四元混合熔盐相比Solar二元熔盐和Hitec三元熔盐,熔点更低,上限使用温度更高,在光热发电、工业储热传热领域有广泛的应用前景。

Low melting point mixed nitrate molten salt can well solve the problems such as pipeline freezing and blocking in traditional Solar molten salt heat storage system,which is of great significance for improving the safety and reducing the operation cost of the molten salt heat storage system.The phase diagram thermodynamic calculation of NaNO_(3)-KNO_(3)-Ca(NO_(3))_(2) molten salt was carried out based on CALPHAD method,and the composition ratio of low temperature eutectic point and melting point of NaNO,-KNOCa(NO_(3))_(2) molten salt were obtained through experiment.Furthermore,LiNO_(3)was added into the ternary eutectic component,and the melting point of molten salt can be reduced.According to the forms of molten salts with different ratios at different temperatures,the quaternary molten salt material with lower melting point was obtained.The melting point is 55.1℃,the initial crystallization point is 54.6℃,and the upper limit of use temperature is 561 C through DSC test and TG test.The melting point of this quaternary mixed molten salt is lower than Solar molten salt and Hitec molten salt,the upper limit operating temperature is higher,and it has a broad application prospect in the fields of solar thermal power generation,industrial heat storage and heat transfer.