The use of molten salt hydrates in metallurgical processing

拟议的项目旨在更好地了解熔盐水合物及其在矿物和金属加工中的潜在应用。熔盐水合物(MSHS)是与水有很高亲和力的化合物，因此形成水合物，其熔点和水化程度取决于温度和湿度。例如，一些例子是MgCl2-XH2O和FeSO4-XH2O，其中X是缔合水的数量。到目前为止，关于盐的研究工作通常分为两大类：水和无水。水相体系是指水盐比非常高的体系。而无水体系只由盐(熔融盐)组成。这项工作试图调查这两个非常不同的相之间的区域。可以肯定的是，MSHS的水活度将发生显著变化，水合度略有变化(即2.1摩尔的水与1.9摩尔的水)。但这种现象是可以利用的。通过更好地了解MSHS，应该有可能研究矿物和金属加工中的广泛潜在应用。这些主题中的一些是：-气体吸收：一些MSH可逆地吸收大量气体，如CO2和SO2，为它们用于烟气净化或气体分离打开了可能性。在这项工作中，将确定各种气体在MSHS(盐、温度、水合作用)范围内的溶解度，以产生足够的数据用于建模目的。考虑的其他气体包括CO2、SO2、H2S和HCl。-水解：考虑到可获得的高温，可以对MSH中的金属离子进行水解；例如，从含有金属氯化物的MSH中获得有价值的金属氧化物粉末是可能的。-储热：如果可逆地添加蒸汽，可以释放MSH相当大的水化热，为暖通空调和太阳能热能应用提供储热/冷却。更传统的显热储存也是一种选择。-浸出：MSHS中的酸活度远远高于稀溶液中的酸活度。因此，热MSH可能起到溶解难溶矿物的“超级浸出剂”的作用。*在初步的氯离子浸出试验中已经证明了这种情况，但这种效应的机理和最佳条件尚不清楚。

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.