The use of molten salt hydrates in metallurgical processing

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The proposed projects are aimed at better understanding molten salt hydrates and their potential applications to mineral and metal processing.  Molten salt hydrates (MSHs) are compounds that have a high affinity to water and so form hydrates that have a range of melting points and degrees of hydration, depending on the temperature and humidity, for each salt.  Some examples are MgCl2-XH2O and FeSO4-XH2O, where X is the number of associated waters.   To date, research work concerning salts has typically been divided into two camps: aqueous, and anhydrous.  Aqueous systems are those with a very high ratio of water to salt, and anhydrous systems consist of only salt (molten salts).  This work seeks to investigate the region between these two very different phases.  Certainly, there will be a significant shift in water activity with MSHs with a small change in the degree of hydration (i.e. 2.1 moles of water versus 1.9 moles).  This phenomenon could be exploited.  Through a better understanding of MSHs, it should be possible to investigate a wide range of potential applications in mineral and metal processing.  Some of these topics are: - Gas absorption:  Some MSHs reversibly absorb large amounts of gases such as CO2 and SO2, opening the possibility for their use in flue gas cleaning, or gas separation.  For this work, solubility of various gases would be determined over a range of MSHs (salt, temperature, hydration) to generate sufficient data to be used for modelling purposes.  Gases for consideration include CO2, SO2, H2S, and HCl. - Hydrolysis:  Given the high temperatures obtainable one could hydrolyse metal ions in the MSH; for example it might be possible to obtain valuable metal oxide powder from a metal chloride-bearing MSH. - Thermal storage:  Reversibly adding steam can release an MSH's considerable heat of hydration, giving thermal storage/cooling for HVAC and solar-thermal energy applications.  More conventional sensible heat storage is also an option. - Leaching:  Acid activity in MSHs is much higher than that in dilute solution.  A hot MSH might therefore act as a "super-leachant" to dissolve refractory minerals.  This has already been shown to be the case in preliminary chloride leaching tests but the mechanism of this effect and the optimum conditions are not clearly understood.