Many snow plowing companies, facility service managers from municipalities and commercial and property owners are looking for a more environmentally friendly option than sodium chloride (rock salt) to remove winter debris and ice from parking lots and sidewalks. One of the alternatives being looked at is magnesium chloride, which has a lower melting point than rock salt. But how does it compare to sodium chloride and what is its actual melting point?
Magnesium chloride and sodium chloride are both ionic compounds, meaning that they contain oppositely charged ions of magnesium (2+) and chlorine (1-). Ionic compounds have strong electrostatic forces of attraction between their ions, which must be overcome by a large amount of heat energy in order for the compound to change state (melt). Since the ions are constrained within the crystal structure of the compound, it requires a high temperature to overcome these forces, giving the substance a high melting and boiling point.
The ternary MgCl2-KCl-NaCl salt mixture has been studied for its potential as thermal energy storage (TES) material and heat transfer fluids (HTF) in next-generation concentrating solar power (CSP) systems. This study has simulated the minimum melting temperature compositions of this salt system using the FactSage 7.2 software.
The eutectic temperature of the MgCl2-KCl-NaCl system was experimentally determined by Kurnakow and Zhemchuzhnui (1907) for a composition containing 56 mol% NaCl and by Rowe et al. (Rowe, 1972) for a composition containing 62 mol% NaCl. The results of this study were compared to these experimental points to determine the lowest eutectic composition and temperature.