Thermodynamic models for metal-salt-oxide liquid solutions

提出的研究计划的目标是为混合金属和离子熔融相的建模开发一个强大和系统的方法，以便在工业和科学兴趣的多组分系统中获得液相热力学性质及其与固相和气相平衡的可靠预测。初级金属的生产和回收通常在高温下的熔融状态下进行，通常在离子液体助熔剂（熔盐、炉渣、冰砂）的存在下进行。今天，科学与工程在很大程度上依赖于模型和仿真工具，以提供不同工艺和材料中物质行为的可靠预测。当涉及化学方面时，热力学模型是这些模拟工具的核心，并且对于在不同条件下为物质的反应、转化和扩散提供驱动力是必不可少的。CALPHAD法已成为冶金和化学无机体系相平衡和热力学性质计算的必备工具。它包括开发吉布斯能量函数，根据实验数据和第一性原理计算，对化学系统中的每个给定相进行校准。化学平衡和相平衡可以通过使用最小化技术来计算，该技术用于找到使能量最小的相的组合和组成。这种方法目前在世界范围内应用于多组分化学系统。不幸的是，液态金属和熔融氧化物/盐之间的混溶性和非混溶性的适当建模还没有很好地建立，特别是相对于影响其导电性的已知化学物质。熔融金属盐平衡表现为完全液相混相（Fe-FeS, Cs-CsCl），部分混相（Cu-Cu2O），强不混相（Cu-Cu2S, li - liff），或几乎完全不混相（Mg-MgCl2）。***本项目的科学方法包括系统测试和实施液体热力学模型，该模型将使用从电导率测量中获得的离子种类，以单一吉布斯能量函数覆盖液态金属和离子组成范围之间的完整组成范围。该模型将测试碱金属-碱卤化物盐，mg - cd - bi -氯化物和表现出部分离子特征的金属合金，如碱重金属，最后测试用于铜冶炼和转化的Cu-Fe-S-O-Si系统。本研究首次允许对离子熔体中的金属溶解和合金中的非金属溶解进行正确的评价。加拿大将在金属生产（铜冶炼、特种金属和合金）领域受益，并通过提高电解的电流效率提高能源效率。

The objective of the proposed research program is to develop a strong and systematic approach for the modeling of mixed metallic and ionic molten phases in order to obtain reliable predictions of the liquid phase thermodynamic properties and its equilibria with solid and gas phases in multicomponent systems of industrial and scientific interests. Primary metals production & recycling are typically performed in the molten state at high temperature, usually in the presence of ionic liquid fluxes (molten salts, slags, mattes). Science & Engineering are today heavily dependent on models and simulation tools to provide reliable predictions of the behavior of matter in different processes and materials. When chemical aspects are involved, thermodynamic models are at the core of these simulation tools, and are essential to provide the driving forces for reactions, transformations, diffusion of species under different conditions. The CALPHAD Method has very strongly established itself as a mandatory tool in the calculation of phase equilibria and thermodynamic properties of metallurgical and chemical inorganic systems. It consists in developing Gibbs energy functions, calibrated on experimental data and First-Principles calculations, for every given phase in a chemical system. Chemical and phase equilibria can be computed by the use of minimization techniques applied to find the combination and composition of phases that give a minimum in the energy. This approach is now applied worldwide for multicomponent chemical systems. ***Unfortunately, the proper modeling of the miscibility and immiscibility between liquid metals and molten oxides/salts is not well established, especially relative to the known chemical species that are affecting their electrical conductivity. Molten metal-salt equilibria show cases of full liquid miscibility (Fe-FeS, Cs-CsCl), partial miscibility (Cu-Cu2O), strong immiscibility (Cu-Cu2S, Li-LiF), or virtually complete immiscibility (Mg-MgCl2).***The scientific approach in this project consist in systematic tests and implementation of a liquid thermodynamic model which will use ion species derived from the electrical conductivity measurements to cover, with a single Gibbs energy function, the complete composition range between the liquid metal and the ionic composition range. This model will be tested for alkali metal-alkali halide salts, for Mg-Cd-Bi-chlorides and for metal alloys that exhibits a partial ionic character, such as the alkali-heavy metals, and finally for the Cu-Fe-S-O-Si system used for Cu-smelting and converting. For the first time, the proposed research permit to evaluate correctly both the metal dissolution in ionic melts and non-metal dissolution in alloys. Benefits for Canada will be in the field of metal production (Cu smelting, specialty metals and alloys) and in the energy efficiency by increasing current efficiency in electrolysis.