Abstract Next-generation concentrating solar power (CSP) technology requires a high-temperature heat-transfer fluid and thermal energy storage media. Molten MgCl2-KCl-NaCl is considered a potential candidate salt due to its thermophysical properties. However, MgCl2 presents various challenges because of its hygroscopic nature. To keep corrosion under control, this molten chloride needs to remain free of hydrates and other impurities. Here, we have developed an effective purification method for MgCl2-containing salts by 1) combining known laboratory-scale, batch-style thermal and chemical purification processes to enable scalable, continuous-style processes for commercial next-generation CSP operation; 2) improving overall efficiency and minimizing the major corrosive impurity MgOHCl by optimizing key engineering parameters such as heating temperature/time and amount of elemental Mg addition; and 3) investigating the addition of halite (NaCl) to carnallite (KMgCl3) to reduce the liquidus temperature. Laboratory-scale results suggest that 1) adding 6.5 wt% of halite and less than 0.1 wt% of elemental Mg to commercial carnallite and 2) following a heating schedule to at least 650 °C with ~3 h of holding time at that temperature can produce a ternary MgCl2-KCl-NaCl salt composition with a low liquidus temperature of about 400 °C. It also reduces the presence of the corrosive impurity, MgOHCl, from ~1 to 2 wt.% to ~0.1 wt%. Findings of these key engineering parameters should provide a pathway toward a scalable, continuous-style salt-purification process at a scale of metric tons per hour that can produce a corrosion-controlled chloride molten salt for CSP applications.

中文翻译：

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用于下一代聚光太阳能技术的含 MgCl2 盐的经济高效纯化方法的潜在可扩展性

摘要 下一代聚光太阳能（CSP）技术需要高温传热流体和热能储存介质。由于其热物理特性，熔融的 MgCl2-KCl-NaCl 被认为是一种潜在的候选盐。然而，MgCl2 由于其吸湿性而面临各种挑战。为了控制腐蚀，这种熔融氯化物需要保持不含水合物和其他杂质。在这里，我们通过以下方式开发了一种有效的含 MgCl2 盐的纯化方法：1) 结合已知的实验室规模、间歇式热和化学纯化工艺，为商业下一代 CSP 操作提供可扩展的连续式工艺；2）通过优化加热温度/时间和元素Mg添加量等关键工程参数，提高整体效率并最大限度减少主要腐蚀性杂质MgOHCl；3) 研究在光卤石 (KMgCl3) 中添加岩盐 (NaCl) 以降低液相线温度。实验室规模的结果表明，1) 向商业光卤石中添加 6.5 wt% 的岩盐和低于 0.1 wt% 的元素镁，以及 2) 遵循加热计划至至少 650 °C，在该温度下保持约 3 小时的时间可以产生具有约 400 °C 的低液相线温度的三元 MgCl2-KCl-NaCl 盐组合物。它还可以将腐蚀性杂质 MgOHCl 的存在从 ~1 到 2 wt.% 减少到 ~0.1 wt%。这些关键工程参数的发现应该为实现可扩展的、