Experimental Study of Hygroscopy of Single and Different Mixtures of MgCl₂, KCl, NaCl, ZnCl₂ for Application As Heat Transfer Fluids in CSP

Eutectic molten chloride salts by MgCl₂, ZnCl₂, KCl, and NaCl are considered as promising high temperature heat transfer and thermal storage fluid in concentrated solar power (CSP) systems. However, chloride salts MgCl₂ and ZnCl₂ are water affinity, so they can absorb water from surroundings easily. This will increase the corrosion of metals when the molten salts stay with metals at high temperatures. Our study also found that the presence of trace water in the solid salt caused vapor pressure of the molten salts increase. The current work presents studies about the kinetic processes of water absorption and removal from single and different mixture of NaCl, KCl, MgCl₂ and ZnCl₂ salts. The process of water uptake from ambient air and removal through heating are measured quantitatively. Water removal from molten salts through sparging with argon gas was employed as a further treatment method.